Arkansas Water Resources Center

WATER RESOURCES ASPECTS OF COAL TRANSPORTATION

BY SLURRY PIPELINE

Dr. James W. Moore

Department of Civil Engineering University of Arkansas

Fayetteville, Arkansas 72701

Publication No. MSC-011

Arkansas Water Resources Center 112 Ozark Hall

University of Arkansas Fayetteville, Arkansas 72701

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WATER RESOURCES ASPECTS

OF

COAL TRANSPORTATIOf4 BY SLURRY PIPELINE

Dr. James W. Moore

Department of Civil EngineeringUniversity of ArkansasFayetteville, Arkansas

72701 ..

Prepared for Presentationto

Office of Water Research & TechnologyDepartment of Interior

Washington, D.C.December 9,1977

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TABLE OF CONTENTS

Page -i

Water Resources Aspects of Coal Transportation. 5

Considerations Involved in the Selection of Alternatives.. 7

Gasification/liquefaction with Subsequent Transportation. 7

Electric Power Production with Transmission by EHVPower lines 8

Coal Slurry Pipelining versus Rail Shipment. 10

General Description of the Coal Slurry Pipelining Process. 14

History of Coal Slurry Pipelines. 17

Water Quality Considerations. 19

Phase I Resu.l ts 22

Alkalinity. 23

Aluminum 29

Biochemical Oxygen Demand. 29

Chemi ca 1 Oxygen Demand. 38

Calcium and Total Hardness. 38

Chloride. 41

Nitrate. 44i

pH 44

Potassium 48

Si 1 ica 48--'-0,

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Page

Sodium. 48

Su 1 fa te 52

Titanium.. 52 -

Anaerobic-Aerobic Comparisons. 52 .

Phase I I Resul ts 52

Phase III Results.. 59

Summary. 61

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LIST OF TABLES

Table Page -

I. Incremental Water Supplies Required for EnergyProduction in 1985 6

II. Approximate Water Requirements at Source forTransportation Alternatives. 5

III. Cost Breakdown of Slurry Pipelines. 13

IV. Pipeline Coal Size Characteristics. 15

V. r~ajor Water Quality Paramaters in SlurryWastewater 23

VI. Potential Toxicity of Trace Elements in Coal. ..24

VII. Aquatic Effects of Trace Elements Derived fromLife-Time of 1400-M~/e Coal-Fired Power Plant. ..25

VIII. Detectable Limits of Tests for Selected Parametersin Sl urry Wastewater. 26

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lIST OF fI~URE$

Figure Page

1. Map of United States Coals 3 :

2. Existing and Planned Coal Slurry Pipelines inthe United States 4

3. Comparison of Alternate Modes of Coal EnergyTransmission, for 1000-Mile Transport Distance 9

4. Coal Slurry Pipeline Transportation Costs 12

5. Inflation on Coal Transport Costs 13

6. Flow Diagram of a long-Distance Coal SlurrySystem 16

7. Total Alkalinity Concentrations in the SlurryWastewater as a Function of Residence Time 27

8. Total Alkalinity Concentration in the SlurryWastewater as a Function of Residence Timeand Slurry Solids Concentration 30

9. Total Alkalinity Concentration in the SlurryWastewater as a Function of Coal Source and

I Residence Time 30/

10. Aluminum Concentrations in the Slurry Wastewateras a Function of Residence Time 31

11. Typical Ultimate Biochemcial Oxygen Demand Curve 33

12. Biochemical Oxygen Demand Curves representingvarious Degrees of Treatability 33

13. Ultimate Biochemcial Oxygen Demand Curve forSlurry Wastewater 35

14. Biochemcial Oxygen Demand Concentrations inSlurry Wastewater as a Function of ResidenceTime 36 ---:

15. Biochemical Oxygen Demand Concentrations in theSlurry Wastewater as a Function of ResidenceTime and Slurry Solids Concentration 36

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16. Biochemical Oxygen Demand Concentrqtionsas a Function of Residence Time and Coal

co.

Source 37

17. Chemical Oxygen Demand Concentrations in thej Slurry Wastewater as a Function of Residence

Time 39

18. Chemical Oxygen Demand Concentrations in theSlurry Wastewater as a Function of ResidenceTime and Solids Concentration 39

19. Chemical Oxygen Demand Concentrations in theSlurry Wastewater as a Function of ResidenceTime and Coal Source 40

20. Chemical Oxygen Demand Concentrations in theSlurry Wastewater as a Function of ResidenceTime and Solids Concentration 40

21. Calcium and Total Hardness Concentrations in theWastewater as a Function of Residence Time 42

22. Calcium and Total Hardness of the Slurry Waste-water as a Function of Residence Time 42

23. Calcium and Total Hardness Concentrations in /Slurry Wastewater as a Function as a Functionof Residence Time 43

24. Chloride Concentrations in the Slurry Wastewateras a Function of Residence Time 45

25. Chloride Concentrations in the Slurry Wastewateras a Function of Residence Time and Coal Source 45

26. Chloride Concentrations in the Slurry Wastewaterwith Distilled Water and Municipal WastewaterEffluent Used as the Slurry Media 46

27. Nitrate Concentrations in the Slurry Wastewateras a Function of Residence Time and Coal Source 46

:

28. Nitrate Concentrations in the Slurry Wastewateras a Function of Residence Time and Slurry Media 47

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29. pH of Slurry Wastewater at various ResidenceTimes 47

30. Variations in pH with Residence Time forSlurry Wastewater 49 .

31. Potassium Concentrations in the Slurry Waste-water as a Function of Residence Time andCoal Source 49

32. Silica Concentrations in the Slurry Wastewateras a Function of Coal Source and Residence Time 50

33. Sodium Concentrations in the Slurry Wastewateras a Function of Percent Solids and ResidenceTime 50

34. Sodium Concentrations in the Slurry Wastewateras a Function of the Coal Source and Residence

,Time 51

35. Sodium Concentration in Slurry Wastwater as aFunction of Residence Time and Water ource 51

36. Sulfate Concentration in Slurry Wastewater as aFunction of Residence Time and Coal Source 53

37. Sulfate Concentrations in Slurry Wastewater asa Function of Residence Time 53

38. Titanium Concentration in Slurry Wastewater asa Function of Residence Time and SolidsConcentration 54

39. Titanium Concentration in Slurry Wastewater asa Function of Residence Time and SolidsConcentration 54

40. pH of the Slurry Wastewater as a Function ofResidence Time 55

41. Total Alkalinity Concentrations in the SlurryWastewater as a Function of Residence Time 55 --~

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Figure Page

42. Calcium and Total Hardness Concentrationsin the Slurry Wastewater as a Function ofResidence Time 56 -

43. Biochemcial Oxygen Demand Concentrations inthe Sl urry ~~astewater as a Function ofResidence Time 56

44. Chemical Oxygen Demand Concentrations in theSlurry Wastewater as a Function of ResidenceTime 57

45. Mixed Liquor Suspended Solids Concentrationsin the Laboratory Activated Sludge TreatmentStudies 61

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The use of slurry pipelines for transporting large volumes of coal

over lonq distances has received widespread and increasing interest in

the past few years. Several reasons account for this increased attention

including the apparent long-term economic and other advantages of large

volume-long distance slurry pipelines over unit train shipment of coal,

the technical success of the Consolidated Coal Company and Black Mesa

slurry pipelines, the increasing price of natural gas and petroleum

fuels, declining natural gas reserves and activity by both the state

and Federal governments.

By general acknowledgement, a substantial increase in utilization

I of the nation's coal reserves will be required to meet the nation's short-

and mid-term energy needs and to reduce the nation's dependence on imported

petroleum. If these needs are to be satisfied, new large fossil-fuel

fired furnaces will have to be coal-fired and conversion of numerous

existing natural gas or oil-fired furnaces to coal will be required.

The increased coal consumption will require that adjustments be

made in both coal mining and coal transportation capabilities as well as

in the coal utilization capacity. Concerning coal transportation, the

alternatives for transporting the large volumes of coal required include

expansion and upgrading of rail capacity, construction of coal slurry

pipelines, barging (where applicable), generation of electric power with---subsequent transmission of the power by extra high voltage (EHV) trans- .

mission lines (either conventional or cryogenic), gasification or lique-

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faction of the coal with subsequent movement of the gas or liquid fuel

to the use site, or by a combination of these alternatives.

An examination of the location of the nation's coal reserves -

indicates the transportation requirements that will occur as the nation's

coal resources are developed. As shown on Figure 1, the major coal reserves

are located in four general areas. These are the t~estern deposits in the

Rocky r~ountain area, the bituminous deposits in the Oklahoma, Kansas,

~1issouri, Nebraska, Iowa, Illinois, Indiana and Kentucky area, the

lignite deposits in the Texas, Louisiana, Arkansas, Mississippi and southern

Alabama area and the bituminous deposits in the Appalachian area.

Smaller deposits are scattered throughout much of the country. The

Eastern coal deposits are generally located closer to markets than are

the coal deposits in the Rocky Mountain area. The longer distances to

markets involved in developing the ~~estern coal reserves and the low-

sulfur content of the Western coal, among other factors, have focused

most of the coal siurry pipeline activity on movement of the Western

coal. Figure 2 shows the coal slurry pipelines that have been built and

that have been considered in some detail. The Consolidated Coal

Company pipeline was the first major coal slurry pipeline constructed and

operated. It extended from Cadiz, Ohio to Cleveland and provided coal

for Cleveland Electric Illuminating Company's Eastlake Station. The

Black Mesa pipeline was constructed in the late 1960's and extends from

the Black r~esa coal mine in northern Arizona to Southern California

Edison's r~ohave Station in Southern Nevada. Pipelines in various stages --."

of development include the Energy Transportation Systems, Inc., Houston

Natural Gas, Montana/Houston pipeline, Nevada Power Company and Gulf

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-W@ r'i':1 .~I;:iI 1;';::::':;3 L.::J 'i:f.iiWJ ~~,gAr;THRACITE SEMIBITUMIr;OUS BITUMIr;OUS SUBBITUMIr;ous LIGr;OTE

Figure 1. r~ap of United States Coals (After Fry1ing(1))

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Figure 2. Existing and Planned Coal Slurry Pipelinesin the United States

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Interstate-Northwest Pipeline pipelines.

~~ Resources Aspects .2f ~ TransportatiQn

Although awareness that the nation's water resources are limited is

increasing, the Eastern United States has an abundant supply of water

relative to the Western states. In this context, the Eastern states'

refer to the 31 contiguous states east of a line extending generally

northward from the Texas-Louisiana boundary. The 17 contiguous states

West of this line all utilize the appropriation water doctrine for the

I, purpose of maximizing benefits from the available water resources.

Because of the more limited water resources in the West, the impact of

the transportation method(s) used requires more careful consideration.

However, the potential water resource impacts of the development of the,i

Eastern coals must also be evaluated. Table I shows the incremental water

requirements for energy production in 1985 as estimated by the rJational

Academy of Engineering (2). Using these figures to develop approximate

relationships, the data in Table II show the relative water requirements

for the various alternatives.

TABLE II

Approximate Water Requirements atSource for Transportation Alternatives

(Based on 1000 MW equivalency)

Cubic Feet Acre-feetper Second per Year

Unit train Negligible NegligibleCoal slurry pipeline* 2.54 1.840Synthetic gas *** 10.26 7,430Synthetic liquid 13.54 9,810Electric power generation** 27.63 20,000 ---0

BTU B* Based on 8500 ~ coal, 10,000 ~ heat rate and 0.65 load factor.** Taken directly from Table I. b

*** Based on 1000 ~ gas, 10,000 ~ heat rate and 0.65 load factor.kw .b

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TABLE I

Incremental Water Supplies Required

for Energy Production in 1985

Amount of Water,Thousands Acre-

Resource Development Feet per tear

Increased coal production in theWest. surface-mininq reclamationfor 500 million tons/year 24

Coal slurry pipelines to transportWestern coal, 1.00 millions tons/year 55

New coal-lignite electric generatingcapacity, 1.70 gigawatts 3,400

New nuclear electric generatingcapacity, 325 gigawatts 7,1.50

Oil from shale, 1. million barrelsper day 160

Synthetic gas from coal, 1..1. millionbarrels per day oil equivalent (21.gasification plants, each with 250million cubic feet per day capabity) 250

Synthetic liquids from coal, 0.6 millionbarrels per day .180

TOTAL 1.1...21.9

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Although these data are only approximate, they do show the relative

water requirements of the several alternatives. Thus, from the water

resources viewpoint, unit train shipment of coal would be the most

acceptable transportation method in the arid West with coal slurry pipe--

lining being the second best alternative. For Eastern coals where water'

is more abundant, any of the alternatives would be acceptable from the

water resources viewpoint providing reasonable siting criteria were

used in the site selection process.

Considerations Involved in the Selection of Alternatives. In

addition to the volumetric water resources considerations, a variety of

factors have been advanced by the proponents and opponents of the several

.transportation methods. Several of these are included to generally

characterize the considerations involved.

Gasification/Liquefaction ~ Subsequent TransportatiQ~. Both

coal gasification and liquefaction must still be considered in the experi-

mental stage, although demonstration programs are being conducted. The

question of whether the cost of the gasified and liquefied fuels will

ever be sufficiently low to be competitive with coal for use in large

fossil-fuel fired furnaces remains. Additionally, the limited water

resources in the West will undoubtedly inhibit widespread adoption of

qasification/liQuefaction for the Western coal. Obviously., water from the

Upper lv1issouri basin could be used for these processes but such usaqe

will preclude other beneficial utilization at some future time and would

probably not be acceptable to the Western states. It is conceivable tha~_..,

national needs may dictate that Upper Missouri water be used for wide-

spread gasification/liquefaction processing, but the best procedure would

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appear to attempt to develop the lrIestern coal resources with minimum

adverse impact on the Western water resources. Water could be transported

from a more distant point on the t1issouri River or from another source

where the adverse impact would be less significant but this procedure

would further increase the cost of the gasified or liquefied fuel. ,

Electric ~ Production ~ Tran~m!ssion ~ ~ ~ .!:~.

The two major disadvantages of locating electric power generating stations

at or near the coal source in the West are the large water requirements

for cooling and the losses encountered by conventional extra high voltage

(EHV) Dower lines. Additionally, the construction of numerous large

generation stations near the coal resources could likely cause an adverse

sociological and environmental impact from the point of view of the resi-

dents. Figure 3 shows a comparison of the costs of transporting energy

by unit train (coal), coal slurry pipelining and extra high voltage power

lines. Of the three alternatives shown for transportinq coal energy, the

EHV costs are the highest, the unit train shipment the more economical

for less than about six million tons per year and coal slurry pipelining

the most economical for greater than about six million tons per year.I

Regardless of whether one agrees with the exact costs reported, the place-

ment of the curves on the graph do generally indicate the relative econo-

mics of the three alternatives. Should cryogenic extra high voltage

power lines become available, both technically and economically, at some

time in the future, EHV could assume a greater role. However, considera-

ble research and developmental work remains before cryogenic extra high~~~.

voltage power transmission becomes a reality on a widespead basls. The

use of dry cooling towers for rejecting heat from power plants for the

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~ ~~...fISSION"~ ..'..~ ~ 3.0 U~T-!.R~~ @ 0.69'fTon Mile

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20 .EHV CO\t\ Adapted from FPC.1970 National Power Survey Part I

.1973 Cost Ba\is

1.50 1 2 3 4 5 6

Million Kilowett Plant Capacity

I I I I I 110 3 6 9 12 15 18

Million Tons per Yoar Coal

Figure 3. Comparison of alternate modesof coal energy transmission.for lOOO-mile transport distance.(After Wasp and Thompson (3)).

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...purpose of minimizing water requirements could be a major cQnsideration,

In general, both the capital and operating costs of dry cooling towers

are greater than for wet cooling towers, Thus, the use of dry cooling

towers would result in a larger delivered cost of electric power for the

generation at the coal source with transmission by extra high voltage

power lines alternative,

~ Slurry Pi~elining versus~ Shipment, Because of the

factors previously identified, much of the emphasis has been focused on

using unit trains and coal slurry pipe lining for transporting most of the

Western coal to markets, Additionally, private firms developing coal

slurry pipeline projects have not had eminent domain authority as do firms

developing natural gas and petroluem product pipelines, For this reason,

considerable attention has been directed towards the coal slurry-unit

train alternatives, At least two states, Oklahoma and Texas, have passed

legislation providing eminent domain authority for coal pipelines,

Congress has considered such legislation and has held hearings in both the

House and Senate (4,5). Hearings have been held on the current

bill (HR 1609, Coal Pipeline Act of 1977). A variety of considerations

have been advanced by both the opponents and proponents of coal slurry

pipelines. Many of these relate to economic, environmental and social

considerations. Slurry pipeline proponents point to the noise levels of

unit trains; the frequency of passage of unit trains through communities~

particularly near the coal mines; the potential range fire hazards caused

by frequent passage of trains through range land (hot boxes, etc.); the

I loss of coal from unit trains during shipment (estimated to be as much ,

as one percent of the coal transported by rail in open cars; the

high reliability of coal slurry pipelines; the reduced impact of inflation!

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over a long period on transportation costs of coal delivered by slurry

pipeline; reduced susceptibility to electric power generation interruption

by strikes and other labor problems; lower steel and other material

requirements for pipelines than for equivalent rail transportation capa-

city~ lower adverse esthetic effects of pipelines, the safety factor of

slurry pipelines, lower long-term transportation costs and other con-

siderations. Opponents of slurry pipelines point to the larger water

demand of slurry pipelines than for rail shipment; the adverse effect the

use of slurry pipelines would have on the financial and economic welfare

of railroads; the environmental impact of slurry pipelines; the lower

labor requirements (less jobs) of slurry pipelines compared with rail-

roads and other factors as disadvantages of slurry pipelines.

Concerning the economic considerations, slurry pipelines apparently

have long-term advantages for large volume-long distance transportation

coal movement. Figure 4 shows the relative costs of rail shipment and

slurry pipelining for several distances. As indicated by these curves,

slurry pipelining is competitive \1hen large volumes and long distances

over extended time periods are involved unless site specific factors

are significant. Figure 5 shows projected escalation curves for pipe-

line and unit train shipment of coal. Pipelines are capital intensive,

but the variable costs are a relatively low proportion of the total cost.

One estimate of the cost breakdown for slurry pipelines is shown in Table

I I I .

Because coal slurry pipelining is less labor intensive than is rail---shipment of coal, the proponents of slurry pipelines point to the re- .

duced likelihood of interruptions in electri~ power and other industrial

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PIPIIINF0 !, lilt, hili"" SillIlY PI",'

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0 t\ 111\ II i ;IIlIt' fl;ll" wi.. II!I""";II" ,

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Figure 4. Coal Slurry PipelineTransportation Costs(After Wasp (6))

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~ 2.0~-I-'~ 0.5% ESC Pipeline.;:: 1. 0-I-' :to..-~~ 0

0 5 10 15 20 25

Tlt~E (YEARS)

Figure 5. Inflation on Coal Transport Costs(Basis 3.6 % Gt1P Inflation Rate)(Excerpted from t1ining Con;ress Journal (2)

TABLE III

Cost Breakdown of Slurry Pipelines(Excerpted from Pipeline Industry (7 )

Percentage ofFactor Total Cost

Fixed cost 84

Variable costs

Power 6

Labor 5

Supplies -2

j Total 100

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production when slurry pipelining is used. Management personnel could

operate the slurry pipelining system should labor problems develop.

Obviously, coal can be and usually is stock-piled at the plant site

when unit trains are used to minimize the impact of labor difficulties

on the plant operation. With this procedure, only extensive strikes

would severely affect power or other industrial production. Disadvan-

tages of stockpiling of coal are potential adverse environmental impacts

from surface runoff, leaching through the stored coal, and the cost of

funds tied-up by the unused fuel.

The arguments that:noise levels of unit trains are significant;

large numbers of unit trains would increase the danger at railroad-

highway grade crossings; community disruption would occur when large

numbers of trains pass through communities near the coal reserves; the

potential for fire hazards would be increased because of the additional

unit trains; most of the physical facilities required by slurry pipelines

(pipeline) are buried and, thus have less adverse esthetic effects -all

must be considered, but do not necessarily bear on the water resources

aspects of coal slurry pipelines. Similarly, railroad arguments that

passage of the Coal Pipeline Act of 1977 would have an adverse effect

on the financial and economic welfare of the nation's railroads must be

considered but does not have a direct bearing on the water resource

considerations.

General Description.Qf ~ ~ Slurry Pipelining Process

Basically, the coal slurry pipelining process consists of crushing

and grinding the coal to a size that will allo\~ suspension in water, .~~

mixing the coal and water (slurry formation), movement of the slurry

through the pipeline by pumping, and separation of the coal solids from

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the liquid at the receiving station. Separation processes and opera-

tions may include flocculation, sedimentation and centrifugation or

vacuum filtration. The size of the coal solids in the s1urry vary some-

what depending on site specific considerations, but the general size

characteristics can be illustrated by the coal gradation used in the:

Consolidated Company pipeline as shown in Table IV.

TABLE IV

Pipeline Coal Size Characteristics(After Frey, Jonakin & Caracristi ( 8))

Screen Mesh Percent Retained

8 0.7

14 6.9

28 18.2

48 18.9

100 15.1

200 10.4

325 6.3

-325 23.5

Total 100.0

! Because most modern large coal-fired furnaces use pulverized coal,

crushing and grinding of the coal at either the source or at the use

site is acceptable. Figure 6 shows the flow diagram of the overall coal~-..,

slurry pipeline operation. II!

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!CO,\L SUPPliER .1. PIPf. LINE SYST(I,I

! .SlURlIY~ I PREPAnAiIOt~ .

'. , .~ ;I'::~ '1,::,- ~,r~,'. "'.{"'-~a ~I ':I~\ ':.t, 9" .~ .~ "II Iii'.] \:1 \ -"-

V Jf 3. ."":'!;~A-"~~ .: .' ' I -r ~" ' " '" ,':""H't:., ,- -, ". --K

MINE ~ PilE COAL ClEAI~ING t " TA"KAG,l,

\""1[11 SUrrLY ~,{, y 8

,,'\\).,;- V'~\,-:1~ J(:"

,-,,~" 0 Io\,~~ 'e .,~ PIPt:Llf-l[ .!. COAl

SYSTEM I IJUYER rOWER~ .PLAt-lT

ok"'" ~ ~~,~j').. ~ 'lj( 0 / "~ J.-":.~ 'e ""'-.;:.,'?),~ -"k"" .DfWAlfllED --

I '; ,Iif COAL

.; ~1il:j'n:~:II::' ~ .BARGES ~ -).. ~ ~: , It!l, I 't' -";I,,- ..z:e-,-

"..,ijl ~~DE\'lATERlNG .PLANT

Figure 6. Flow diagram of a long distancecoal slurry pipeline system.(Reprinted from Pipeline Industry,May, 1975 (7)),

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History.Ql ~ Slurry Pipelines

The concept of transporting coal by slurry pipeline is an old one.

However, the first major coal slurry pipeline was not constructed until

the mid-1950's. This pipeline, constructed by the Consolidated Coal

Company, moved coal from Cadiz, Ohio, to Cleveland Electric Illuminating

Company's Eastlake Station (9). Disagreement with existing freight

rates apparently was the motivation for developing the slurry pipeline

project. The pipeline was used for only about six years because a sub-

sequent reduction in freight rates made rail shipment more economical

( 9). However, the pipeline was maintained in a "ready" status should

the rail freight rates again increase sufficiently that pipeline ship-

ment would be more economical (9). The pipeline was small (108 miles).

Operations at the slurry preparation plant were unique primarily because

th e plant was designed for operation with either two or three shifts

per day whereas the pipeline was to be operated twenty-four hours per

day, seven days per week. Essentially, the slurry preparation plant

consisted of screening, crushing, storage, mixing, and slurry storage

facilities. Clean 3/8" X 0 coal was initially screened with the screen

undersize stored in drag tanks. The screen oversize was either crushed

or stored in a storage pond. If crushed, the screen oversize was either

sent to the drag tanks or to a second storage pond depending on the

quantity of coal needed for the pipeline at that particular time. The

very fine coal that was carried over with the overflow from the drag

tanks was stored in a third pond. Storage in three ponds rather than,,~-=

in a single pond was used to avoid segregation by size fractions. By

preventing segregation by size, the fractions could be recombined in

18

the proportions required (.9).

Dewatering of the liquid-solids mixture was accomplished by thicken-

ing, vacuum filtration and flash drying. The general dewatering scheme

was thickening to about 60 percent solids (by weight), vacuum filtration

to about 20% moisture and flash drying to the extent desired. The dried

material was then stored until needed. Particulates from the drier were

collected and either sent to the boiler or flocculated and returned to

the vacuum filter. The filtrate from the vacuum filter was flocculated

and settled before discharge (9).

The second major coal system constructed was the Black ~1esa pipe-

line which transports coal from the Black Mesa coal mine in northern

Arizona to the f4ohave Power Station in southern Nevada. This pipeline

has been in operation since 1970 and has displayed excellent operational

characteristics. Some plugging occurred during start-up until the

optimal size gradation was established, but the plugging was minimal and

did not cause major difficulty (10). Reported availability of the pipe-

line has exceeded 99 percent (10). The Black Mesa slurry system is 273

miles in length and is eighteen inches in diameter for most of the

distance. Pipeline size was reduced to 12 inches for the purpose of

increasing headloss as the line descends from the mountainous terrain

to the Colorado River valley.

Coal preparation consists of crushing and wet grinding the two-inch

coal received from the mine to minus one-eighth inch in a two-step

operation. Dry crushing and impact mills are followed by wet grinding

and rod mills where the slurry is formed (10). d-""'"

Coal is dewatered at the Mohave generating station by centrifu-

~ - - ~:-.l20

...., ".

Department of Interior. The research program has three major objectives

which are to: 1) identify the type and extent of water quality changes

that will occur as a result of the coal slurry pipelining process; 2) I

determine the technical feasibility of using poor-quality water, such as

treated municipal and industrial wastewater, as the slurry medium; and"

3) to determine the treatment measures suitable for use in restoring the

slurry wastewater quality to acceptable levels. The research program

is in the final year of a three-year program and will be completed in

June, 1978.

The conceptual design of the research program was general, rather

than being specific for one pipeline, to allow general application of

the data. Consequently, several parameters, which would be fixed for a

specific pipeline, were varied. These include coal source, slurry

~c make-up water quality, slurry solids concentration, coal gradation, and

residence time. Five "types" of water have been used in the research

'program to date 'including distilled water, "surface" water, ground water,

municipal wastewater and industrial wastewater. r~ore than one water

source were used for the ground water and industrial wastewater. The

purpose of using distilled water was to provide data which could be

readily reproduced. Both the slurry solids concentration and coal

gradation have been varied in the experimental work. To insure that the

slurry solids concentrations used would bracket the concentrations that

would be encountered in slurry pipeline systems, solids concentrations

of 40,50, and 60 percent by weight were chosen. A slurry pipeline using.--

a 40 percent solids concentration would be both economic and water in-

efficient. It is conceivable that future developments may allow use of

,,' ;; 21'

.

a 60 percent solids concentration slurry by using polymers or other mea-

sures to minimize water requirements. However, the 60 percent slurry

should provide an acceptable upper solids concentration. Coal gradation

was varied in a similar manner.

The general approach used in the research program was to evaluate ~

the water quality changes that would occur under both aerobic and

anaerobic conditions. This approach was used because both environmental

conditions can be expected in a full-scale system. If surface water is

used for the slurry medium, it will ordinarily have free dissolved

oxygen present. Additionally, the wet grinding of coal and mixing of

the coal and water (slurry formation) will ordinarily be conducted in

the presence of air, thus assuring that the slurry is initially aerobic.

The amount of dissolved oxygen present may vary, but some can be expected

to be present. The dissolved oxygen concentration could conceivably

vary from a relatively small concentration to a saturation value and

possibly could be supersaturated in some instances. Once the slurry

has been charged to the pipeline, no additional free molecular oxygen

will be available unless the slurry is exposed to air such as in a dump

pond or should the pipeline be evacuated of slurry for repair or other

reasons. Oxygen consuming materials, both inorganic and organic, will

depress the dissolved oxygen concentration and will ordinarily deplete

the available molecular oxygen, thus developing an anaerobic environment.

The reactions are different under anaerobic conditions than under

aerobic conditions for some parameters. In addition .to the aerobic--00:

environment initially in the pipeline, the slurry storage at the origi-

nating station, the dump ponds (if or when needed), slurry storage at

22.~

..-, '.0 I

the receiving station, and the dewaterin~ operation will normally be

aerobic. Thus, the environment could vary from aerobic to anaerobic

and back to aerobic from the time the slurry is formed until dewatering

has been completed.

The agitation vessels were designed and constructed to provide:

varying degrees of agitation, again to bracket the conditions that should

be encountered. Twelve of the twenty-four agitation vessels were designed

as closed vessels and were equipped with ports for adding nitrogen gas

to form a blanket on top of the liquid in the vessel to maintain an

anaerobic environment.

The research work is being completed in three phases corresponding

to the three objectives of the research program. The data accumulated

over the two-and-one-half year period are too voluminous to include all

of it in this report, rather the general results will be summarized.

I Phase I Results

The objective of this phase was to identify and characterize the

water quality changes that will occur in the coal slurry pipelining

operation. The highest concentration water quality parameters are

included in Table V.

There are a variety of trace elements that are present in coal.

Most of these are not leached from the coal in substantial concen-

trations. Table VI shows one assessment of the potential toxicity

of trace elements in coal.

I,

" 23

..\,.

TABLE Y

Major Water Quality Parameters Iin the Slurry Wastewater

Alkalinity pH

Biochemical oxygen demand Potassium -iI

Calcium hardness Si1ica ;'

Chemical oxygen demand Sodium

Chloride Specific conductance

Magnesium Sulfate

~Jitrate Total hardness

Table VII shows one assessment of the aquatic effects of trace elements

in coal.

The concentrations of several parameters were below the detectable

limits of the test procedure used. These include chromium, copper,

iron, manganese, mercury, phosphate and zinc. Atomic absorption vias

used for the metals determinations. The detectable limits of the

test procedures are included in Table VIII.

Alkalinity. Alkalinity in water may consist of the bicarbonate,

carbonate and hydroxide ions depending on pH. The primary effect

of alkalinity is that it serves as a buffer which resists changes in

pH as do other weak acids and bases. When no buffering capacity is

present in water, the pH can fluctuate radically when only small~--

amounts of either acids or bases are present. Conversely, a water

with a large buffering capacity will reflect only small changes inIL

-

t. 24..' 1 '1

.I'

TABLE VI

Potential Toxicity of

Trace Elements in Coal

Terrestrial -

[1 ement =!~~ ~ Aquati c

Antimony Medium High* Low*

Arsenic Low Low Low

Beryllium Medium High High*

Bismuth Medium Low Low*

Boron High Medium LoW*

Cadmium High High High

Chromium High Medium t4edium

Cobalt High Medium High

Copper High Medium High

Fluoride High High Low

lead Low Medium Medium

t~ercury Medium High* High

t.1olybdenum low ~1edium Low

Nickel High High Medium

Tantalum High High Medium

Tin low low Low

Titanium low Low* Medium*

Tungsten t~edi urn t,1edi um* Low*

i Vanadi urn Hi gh LoVJ* r~edi um*.I Zinc Low Medium Medium c

* Uncertain

- -

, 25

.,-' I- .

f

Table VIr

Aquatic Effects of Trace ElementsDerived from Life~-Time Operation of a

1400-MW(e} Coal-Fired Power Plant

Projected water Estimated "no-effect"concentrations after concentrations ;

El~!!!ent 40 years (1,1g/1iter) (~g/liter)

Hg 0.05 0.05 (animal, chronic)

Cd 0.1 0.1 (animal, chronic)

Be 0.06 1.5 (animal, acute)

Co 0.6 10 (animal, chronic)

Cu 0.03 10 (animal, chronic)

Zn 3 30 (animal, chronic)

T1 0.04 30 (animal, acute)

Pb 0.7 30 (animal, chronic)

Ni 0.1 30 (animal, chronic)

V 0.53 50 (animal, acute)

Cr 0.01 100 (amima1, chronic)

Ti 100 (plant, acute)

Se 0.08 125 (animal and plant,acute)

B 220 (animal, acute)

Sn 0.6 350 (animal, chronic)

Mn 3 500 (animal, acute)

As 0.03 500 (animal, chronic)

Sb 0.05 500 (animal, acute) '-"":

Mo 0.001 2500 (plant, acute)

F 0.4 7000 (animal, chronic)

W 1

I.- 26.."..

TABLE VIII.

Detectable Limits of Tests for

Selected Parameters in the Slurry Wastewater

Chromium 0.1 ng/ml ;

Copper 0.09 ng/ml

Iron 0.12 ng/ml

Manganese 0.055 ng/ml

Mercury 7.5 ng/ml

Phosphate 0.01 ng/ml

Zinc 0.018 ng/ml

!

pH even when relatively large quantities of acids or bases are added.

Water with extremely large concentrations of alkalinity is caustic

and is unacceptable, but the concentrations encountered in the coal

slurry experimental work were not in the caustic range. Figure 7

shows the total alkalinity concentrations in the slurry wastewater as

a function of residence time under an aerobic environment. As

shown on the figure, the alkalinity concentrations were reduced as

the residence time increased. This is generally typical of the alka-

linity data obtained throughout the experimental work.

The impurities in coal vary from one source to another and, to

some extent, withi,n the same seam. Consequently, the amount of~_. "":

i alkalinity that will leach from the coal can be expected to vary. ii

There is a considerable data base concerning the amount of alka.,.

line material in coal when one considers the calcium oxide (the

!

i

L_~~ ---

.' 27

".

>,4-' or- M

s::oor- U '

..-10IOU

.:0,(.

..-1/)

<1:10

10-4-'0"1OE1--

.! 0 1 2 3 4 5 6 7 8 9 10 I

T I t1E (DAYS) I,

Figure 7 ° Total Alkalinity Concentrationsin the Slurry Wastewater as aFunct.i~~ nf Residence Time

carbonate and bicarbonate, if present, are calcined in the furnace)

in the flyash from coal-fired po~Jer plants. In two electric power

generating stations (Colstrip Station, Montana Electric Power and

Sherburn Station, Northern States Power) the calcium oxide in the

flyash (from 17 to 20 percent, by weight) is used as the primary

source of alkaline material for the flue gas desulfurization systems

at these stations. Both stations use coal from the Colstrip, MontanaI

areao In other installations using low sulfur coal, electrostatic !

precipitator design has been altered because of the increased resisti-

vities of the flyash caused largely by the higher calcium oxide content --

.of the Western coal flyash when compared with most Eastern coals.

Oxidation of the sulfur that is removed from the coal results in---

i.::. 28. I '

,

substantial quantities of sulfate in the slurry wa~tewater, However,

the pH values of the slurry wastewater from the low-sulfur ~.Jestern

coals used in the experimental work were only moderately acidic..

Generally, these values ranged from 5..5 to 7..0.. Consequently, no acid

mine drainage characteristics have been observed.. There are several

reasons for maintenance of the pH in a range higher than that en-

countered under acid mine drainage characteristics.. The sulfur content

of most Eastern coals is considerably higher than for the low-sulfur

Western coal.. Second, the form in which most of the sulfur occurs in

coal is different between Eastern and Western coal. Sulfur occurs iniicoal in three formS!: 1) pyritic; 2). organic; and 3) sulfate sulfur. I

i.The organic sulfur is chemically bound with the coal and, consequently,

does not leach readily.. ~10st of the sulfur in Western coal is usuallyr:

organic with only a small fraction of the sulfur present as pyritic.

Conversely, a substantial fraction of the sulfur present in most

Eastern coals is pyritic. A major portion of pyritic sulfur can

usually be removed by washing, magnetic separation and/or other methods..

Third, the alkaline source present in the Western coal is present in

retatillely-larqe quantities compared with Eastern coal.. In the

Western coal used in the experimental work conducted to date, the

alkalinity concentrations have been depressed followin~ long residence

times but have not dropped to zero in any of the experimental work.. It

is probable that a simultaneous neutralization of the alkalinity in

the slurry media and leaching of the alkalinity source in the coal

occurs in the longer residence time circumstances.. Additionally, ---,

other weak bases and weak acids become more significant when the

i29...., .

carbonate-bicarbonate alkalinit~ is reduced. Figure 8 shows the alka-

linity concentrations wi.th time for 40 and 50 percent solids concen-

trations slurries under aerobic conditions with distilled water used

as the slurry media. As shown on this figure, the alkalinity started

to decrease following a residence time of 24 hours. Although the coal

and water sources were different for Figures 7 and 8, the same general

tendency would apparently have resulted had the time for Figure 8

been extended. Figure 9 shows a comparison of the alkalinity concen-

trations in the slurry wastewater from two coals with distilled water

as the slurry media. These curves illustrate the differences in alka-

linity concentrations resulting from the two coals. However, the

alkalinity concentrations at the end of 60 hours were about the same.

Aluminum. The concentrations of aluminum in the slurry

wastewater were low, generally less than one part per million. Figure

10 shows the aluminum concentrations for a 50 percent solids slurry

with distilled water used as the slurry media. This curve is generally

typical of those resulting from the distilled water studies.

Biochemical oxygen demand. Biochemical oxygen demand can

, be defined as the quantity of molecular oxygen required to stabilize

the biodegradable fraction of a waste by aerobic biochemical action.

The two biochemical oxygen demand values ordinarily used are the five-

day biochemical oxygen demand (BO05) and the ultimate biochemical

oxygen demand (BOD or BOD1 ). The five-day biochemical oxygenu u t

demand refers to the quantity of oxygen required to stabilize a waste~~-

after a five-day incubation period. The ultimate biochemical oxygen

demand represents the maximum quantity of waste that can be stabilized

I:" 30

f.,.'", I.

100

>,i ~M 80: co

(Jr--1UIU (J 60~ .

r--VIc:( IU 40

'; ~ 40%+'(:1)0 E '

20

AADS0

a 100 60

Tlt1E (DAYS)

Figure 8. Total Alkalinity Concentrationsin the Slurry ~~astewater as aFunction of Residence Timeand Slurry Solids Concentration

100

>,+' 80M

co(J

'; ~ 60~r-- VIc:(1U

r-- r-- 40IU-+'(:1)

~ -=- 20

0 A DS

0 10 20 30 40 50 60

Tlf-tE (HOURS) I!ii

Figure 9. Total Alkalinity in the Slurry,~[aste\'Jater as a Function ofCoal Source and Residence Time

Ii!

I

-

,31. , ." ..

1.0

0.8r---C1

..=:. 0.6E

I ~I c: 0.4.r-

E~

~ 0.2

ABDS00 10 20 30 40 50 60

TIME (HOURS)

Figure 10. Aluminum Concentrations in theSlurry ~Jastewater as a Functionof Residence Time

.,

i

~32

, ,,' I, .

biologically, For "typical" domestic wastewater, the ultimate bio-

chemical oxygen demand is usually exerted within 25 to 30 days and

generally is about 1.5 times the five-day biochemical oxygen demand.

These relationships do not, ho\'Jever, necessarily occur in industrial

wastewaters. Such wastewaters may range from non-biodegradable to .

readily biodegradable depending on the type of organic material

present. Figure 11 shows a "typical" biochemical oxygen demand curve

for domestic wastewater. The lower curve represents the carbona-

ceous demand with the upper curve representing nitrogenous demand.

The carbonaceous demand refers to the quantity of oxygen required to

I stabilize the carbon in the waste. The nitrogenous demand refers to

the quantity of oxygen required to convert the nitrogen in the waste

to nitrate (NO3)'

Figure 12 sho\'JS three biochemical oxygen demand curves that can

occur for various industrial wastewaters. Curve A represents a

wastewater that is non-biodegradable, has little biochemical oxygen

demand or requires acclimation. Acclimation of microorganisms (when

possible) can be accomplished by growing the microorganisms on a

similar synthetic or natural media with gradual substitution of the

wastewater until the microorganisms are acclimated. Curve B repre-

i sents a wastewater that required acclimation but that was relatively

easy to acclimate. Curve C represents a "typical" domestic waste-

water included for comparison purposes. These curves are included as

background because the biochemical oxygen demand curve for the slurry:

waste\'Jater is unusual. An ultimate biochemical oxygen demand curve

representing the slurry wastewater for one coal source is shown on

j -

,-, 33

'" .I ., .

"0'=toE :QJ

0

'=QJ0')>, x 0-

0')E

I ~-I °E

QJ.cu0

or-i co ,

i

Time (days)

Figure 11. Typical Ultimate Biochemical OxygenDemand Curve

"0'=toEQJ0

'=QJ0')>, ~ ~ --x 0- .,---

~ 01E to- /' ..

o~ / /.c .Iu

~ ..,/,-

TIME (DAYS) '..-,

i! Figure 120 Biuchemical Oxygen Delnand Curves

Representing Various Degrees ofTreatability,I

rr

~ 34

. I ." ..Figure 13. As shown on this figure? some of the biochemical oxygen

demand is readily exertable with additional demand exerted in stages.

The significance of this curve cannot be generalized because site

specific factors will largely determine its significance. Slurry

wastewater treated by conventional biological treatment would not.

necessarily remove the biochemical oxygen demand. If the wastewater

were discharged to a surface watercourse following conventional bio-

logical treatment, the biochemical oxygen demand would be exerted

in the watercourse. Conversely, if the site conditions were such

that no discharge from the plant site, occurred, little significance

would be attached to the curve. Should the slurry wastewater be used

in the circulating water system, the high biochemical oxygen demand

could cause difficulty. These factors are discussed more completely~

in the Phase III results.

Figure 14 shows the five-day biochemical oxygen demand curve for

one coal source at 50 percent solids concentration with an anaerobic

environment. As shown by the figure, the five-day biochemical oxygen

demand decreases with increasing residence time in the pipeline.

The generally decreasing five-day biochemical oxygen demand concen-

trations may result from stabilization of the biochemical oxygen

demand, from adsorption of the biochemical oxygen demand by the coal,

from the increasing concentration of a toxic material, or a combination

of these factors. Figure 15 shows the five-day biochemical oxygen demand

concentrations for the 40 and 50 percent solids concentrations sluries,..

under aerobic conditions with municipal wastewater used as the slurry'"

media. These show the same general tendencies as did the anaerobic data

shown on Figure 14. Figure 16 provides a comparison of five-day

,""."",.-1""",,,,

Ii'~ 35

..

4500

--;:: 4000-C1

.s 3500-0c~ 3000CIJc

~ 2500C1>,X0 2000r--~.~ 1500ECIJ

.c:g 1000

.r-00

500

4 8 12 16 20 24 28 32 36 40 44 48

Tlt1E (DAYS)

Figure 13. Ultimate Biochemical Oxygen DemandCurve for Slurry Wastewater

---:,I

-

':

.36'" I ..'

.1

I

.i

100

t::OJ0) 80~..-x-

001E 60 '

~u-o

'r- t::

~ ~ 40.c:OJuo0

~ 20 :!

0 ABMS

0 1 2 3 4 5 6 7 8 9

TIME (DAYS)

Figure 14. Biochemical Oxygen DemandConcentrations in the Slurry~Iastewater as a Function ofResidence Time

-g 250~EOJ0 200t::OJ

~ 150x-Or--r- 01 100~Eu-'r-E~ 50u0~ 0 AA~1S

0 10 20 30 40 50 60

TIME (HOURS)

Figure 15. Biochemical Oxygen Oemand Concentrationsin the Slurry ~Iastewater as a Function of-Residence Time and Slurry Solids Concentration

I~ 37:..' I. .,.

ji

"0 25t=toE

~ 20t=OJ0"1 15>,x-

Or--r-- 0"1 100 .to Eu or-

~ 5.c:u0

or-ro

20 50

Tlt1E (HOURS)

Figure 16. Biochemical Oxygen Demand Concentrationsas a Function of Residence Time andCoal Source

i

--,

I' :38.,'",.

biochemical oxygen demand for the slurry wastewaters from two coals with

treated municipal wastewater used as the slurry media. As indicated by

Figure 16, the differences in the initial five-day biochemical oxygen

demand concentrations for the two coals were significant, but the con- I

centration$ were about the same after a residence time of about 36 hours.

Chemical Oxygen Demand. The chemical oxygen demand test also pro-

vides a measure of the organic material present in a wastewater. This

test used a strong oxidant (potassium dichromate) in the presence of a

strong acid (sulfuric) to oxidize the organic materials present. Because

the chemical oxygen demand test measures both non-biodegradable and bio-

degradable organic material, the chemical oxygen demand concentration

is greater than the biochemical oxygen demand concentration for a sample;i

! except when certain specific chemicals which interfere with the test are

present. Figure 17 shows the chemical oxygen demand concentrations in

a slurry wastewater under anaerobic conditions with municipal wastewater

effluent used as the slurry media. Figure 18 provides a comparison of

the chemical oxygen demand concentrations for two slurry solids concen-

trations under aerobic conditions with distilled water used as the slurry

media. Figure 19 shows the chemical oxygen demand concentration for

slurry wastewaters from two coals under aerobic conditions with distilled

water used as the slurry media.

I The chemical oxygen demand concentrations for 40 and 50 precent

solids slurries under aerobic conditions with municipal wastewater effluent

used as the slurry media are shown on Figure 20. ~-~

Ca1.ciumand Total Hardness. The term "hardness" refers to the diva-

lent metal cations present in water. For most waters, the concentrations

i

I"., 39

"' I,"

1

1

14~t::

~12QJa

~1000)>,a 80ItSU'r- 60EQJ

..c: u 40

20i

i0

0 1 2 3 4 5 6 7 8 9 10

TIME (DAYS)

Figure 17. Chemical Oxygen Demand Concentrations in theSlurry Wastewater as a Function of Residence

Time

~ 250t::

~ 50%~ 200

;, t::I QJ 0) 150

I >, I x 0)

DE';;; "--" 1 00 40%

uor-

~ 50.cu

0

0 10 20 30 40 50 60

TIf'1E (HOURS)

Figure 18. Chemical Oxygen Demand Concentrations ~ :

in the Slurry Wastewater as a Functionof Residence Time and Solids Concentration

i.f' 40

" ~" I ,.'

-0 250; Coal BEOJ 200

CI

cOJ

~-;::: 150x-001

Er 100to =U.

'r-

~ 50..c: .u

00 10 20 30 40 50 60

.TIt'1E (HOURS)

Figure 19. Chemical Oxygen DemandConcentrations in the51 urry ~~astewater as aFunction of ResidenceTime and Coal Source

350r---01

5 300-0Cto 250EOJ

~ 200OJC1>,x 1500

40%..-~ 100

'r-EOJ

6 50

AAt1S0

0 10 20 30 40 50 60

TIME (HOURS)Figure 20. Chemical Oxygen Demand Concentrations

in the-Slurry Wastewater as a Functionof Residence Time

i", '..41

" .....of iron, manganese and strontium are sufficiently low that the term

usually refers to the ions of calcium and magnesium. The significance

! of hardness in water is related primarily to non-physiological properties.

Water treated for domestic consumption usually is softened (i.e., some

of the hardness removed) if the hardness exceeds 150-175 milligrams per

liter. Such treatment is provided to reduce soap consumption, to mini-

mize calcium carbonate precipitation on heat exchange surfaces and other

more limited reasons.

The technology of hardness removal from water is well developed.

Consequently, the presence of hardness in the slurry wastewater is pri-

marily an economic consideration. Hot and cold lime-soda ash softening.

hot phosphate softening and ion exchange all may be used'with minimal

difficulty for hardness removal. For installations utilizing the slurry

wastewater in heat exchange equipment without dilution, softening may

be required to avoid significant reduction in heat exchange rates because

of calcium carbonate precipitation on the heat exchange surfaces.

The calcium and total hardness concentrations in the slurry waste-

water may be substantial as shown on Figure 21. This curve represents I

the hardness resulting from an anaerobic environment with municipal

wastewater effluent used as the slurry medium. Figure 22 shows the cal-

cium and total hardness concentrations in slurry wastewater with distilled

water used as the slurry medium. Figure 23 shows the relationship of

calcium and total hardness with residence time with muncipal wastewater

effluent used as the slurry make-up water. These curves represent the

same coal used for developing Figure 22. ---0

i

Chloride. The chloride concentrations in the slurry wastewater are

relatively low and are a function of both the coal quality and the slurry!

--

, 42

J.

600(V)

a~ 500u

VI10 400..-C"IE 300""-VI -

~ 200t:

"0~

~ 100

0 NBr.1S0 1 2 3 4 5 6 7 8 9 19

TIME(DAYS)

Figure 21. Calcium and Total HardnessConcentrations in SlurryWastewater as a Functionof Residence Time

400

(V)a 350u10U

VI 30010

..-~ 250E""-

~200OJt:

"0So. 1510

:J: AADS

100

0 10 20 30 40 50 60

TIME (HOURS)

Figure 22. Calcium and Total Hardness -"--,",

of,the Slurry Wastewater

as a Function of Residence-Time

I , ".. " .~~, .."

".

.43, ...c

,

400

OM 350Uto

U

I/) 30to

..-ci 250E

I/) 20I/)

Q)t::

~ 15to

:1:

1000 10 20 30 40 50 60~

TIME (HOURS)

Figure 23. Calcium and Total Hardness Concentrationsin Slurry Wastewater as a Function ofResidence Time

~~-:

; 44

..."-

,

media water quality. Figure 24 provides a comparison of the chloride

concentrations in slurry wastewaters from 40 and 50 percent solids slur-

ries with distilled water used as the slurry media. A comparison of the

chloride concentrations resulting from two different coals with distilled

water used as the slurry media is shown on Figure 25. The effect of -

slurry media water quality on the chloride concentrations in the slurry'

wastewater is shown on Figure 26. The chloride concentration in the

traded municipal wastewater was 35.0 milligrams per liter.

r'jitrate. The primary significance of nitrate in \'/ater supplies is

that nitrates have been linked with methemoglobinemia and death in infants

and cattle., The nitrate concentrations in the slurry wastewater were

relatively low. Because a nitrogen blanket is being used to obtain an

anaerobic environment, the nitrate test is not being conducted for the

anaerobic studies. Figure 27 provides a comparison of the nitrate con-

centrations in slurry wastewaters representing two coals with distilled

water used as the slurry media. The effect of slurry media water quality

on the nitrate concentrations in the slurry wastewater is shown to some

extent on Figure 28. A raw water with substantial concentrations of

I nitrate would be expected to yield higher nitrate concentrations in the

slurry wastewater.

~" The pH of a solution is a measure of the hydrogen ion concen-

tration in the solution. By definition it is the negative logarithm of

the reciprocal of the hydrogen ion concentration. Thus, pH serves as

a measure of the acidity or alkalinity of a water or wastewater. Figure..",:

29 shows the fluctuations in the pH values measured under anaerobic

conditions with municipal wastewater effluent used as the slurry media.

"""

45., .." I'

I

20

-15 .0>E---<l) 10

"C'r-~.:::. 5.s::.u

0

0 10 20 30 40 50 60

Tlr.1E (HOURS)

Figure 24, Chloride Concentrations in theSlurry ~Jastewater as a Functionof Residence Time

..

20

r-

"di 15E---<l) 10

"C'r-~0r- 5.s::.u

0 AODS

0 10 20 30 40 50 60

TI~1E (HOURS)

Figure 25, Chloride Concentration in the Slurry~~astewater as a Function of ResidenceTime and Coal Source

~~~

I1'- 46

" ..' 1 '

60 t1unicipa1 ~~astewater

50

~ 40 -E

~ 30 :'.-S-or-- 20<3 0 i s till ed ~I ate r

10

0 AAOS

0 10 20 30 40 5r) 60

TI ~1E (HOURS)

Figure 26, Chloride Concentrations in Slurry~~astewater wi th Oi sti 11 ed ~Jater andMunici pa 1 ~lastewater Eff1 uent Usedas the Slurry t1edia

5M

0Z 4

VIro

r-- 3--.0)-=- ' Coal A

QJ 2-+J

~ 1-+J".-Z 0 AOOS

0 10 20 30 40 50 60

TI t-1E (HOURS)---,:

Figure 27. Nitrate Concentrations in the SlurryWastewater as a Function of ResidenceTime and Coal Source

--

!

1-: 47

, ...I' .

5 ..

4r--

C)E 3OJ -+J~ 2s.. ,+J.r-Z

1

0 AAOS

0 10 20 30 40 50 60

! Tlt1E (HOURS),

Fi gure 28. ~Ii trate Concentrations in the Sl urryI

\~as~ewater ~s a Function of .Resldence Tlme and Slurry Medla

8.0

7.0

6.0:t:0-

5.0

4.0

NBMS3.0

0 1 2 3 4 5 6 7 8 9 10

T I r.1E (DAYS) ~-.-:

Figure 29. pH of Slurry Wastewater atVarious Residence Times

", 48

..t .." I ,

IThe pH values for the slurry wastewaters from two coals under aerobia

conditions with distilled water used as the slurry media are shown on

Figure 30.

Potassium. Figure 31 shows a comparison of the potassium concen-

trations in slurry wastewaters from two coals with distilled water used'

as the slurry media water quality. The potassium concentrations were

low in the slurry wastewater for all experimental work. Consequently,

other then the contribution to total dissolved solids, this paramete~

is not significant.

ISilica. Figure 32 shows a comparison of the silica concentrations

in the slurry wastewater from two coals under aerobic conditions with

distilled water used as the slurry media. The primary significance of

silica in water is that it can form a hard dense scale on heat exchange

surfaces and can severely impede heat transfer.

Sodium. The primary significance of sodium in public \'Jater supplies

is related to cardiovascular problems, that is, persons with cardiovas-

cular difficulties are usually assigned a low-sodium diet. A comparison

of the sodium concentrations in slurry wastewater from 40 and 50 percent

solids slurries under aerobic conditions with distilled water used asI, the slurry media is shown on Figure 33. These concentrations are only

moderately high and should not create significant problems. The sodium

concentrations in slurry wastewaters from two coals under aerobic condi-

tions are shown on Figure 34. The chloride concentrations in slurry

wastewaters under aerobic conditions with both distilled water and treated

municipal wastewater used as the slurry media are shown on Figure 35. I

The sodium concentration in the municipal waste\~a-ter was 7.8 milligrams

per liter.

I

.I.~ 49

.. I ., \.

8.0Coal B

7.0

6.0 Coal A:I:

'0;

5.0

4.

AODS3.0

0 10 20 30 40 50 60

TI ~1E (HOURS)i

Figure 30. Variation in pH with Residence Timefor Sl urry ~Jastewater

10 Coal A

-;::- 8-0)

5 6E~

.~ 4In~+'~ 2

AODS0

0 10 20 30 40 50 60

TIME (HOURS)

Figure 31. Potassium Concentrations in the Slurry\~astewater as a Function of ResidenceTime and Coal Source

'--

!

" 50

, . I ., '..

I 25 Coal B

N

~ 20 -V')

,.I/) .rtI 15

r---t:nE 10"-'rtIU

;= 5 Coal A.r-

V')

00 10 20 30 40 50 60

TIME (HOURS) .

Figure}2. Silica Concentrations in the SlurryWastewater as a Function of CoalSource and Residence Time

r

50

40r---~ 30"-'

E.;: 20-0aV') 10

0 S

0 10 20 30 4fJ 50 60

T I r~E (HOURS)

Figure 33. Sodium Concentrations in the SlurryWastewater as a Function of Percent ---:Solids and Residence TimeL

!t'). 51

" ..' I,

50 Coal B

40r---0)

~ 30 Coal AE::3

~ 20 ;.0

V) I

10

00 10 20 30 40 50 60

"TIt.1E (HOURS)

Figure 34. Sodium ConcentratiQns io the Slurry~Jastewater as a runctlon of tneCoal Source and Residence Time

6

Final Effluent5 0 ~ , e 4 -"'Distilled Water ---~--"--- -.

-r--

~ 30E

§ 20.r--00V) 10

AAOS0

0 10 20 30 40 50 60

TIME (HOURS) ~~"':

Figure 35. Sodium Concentration in Slurry Wastewater as aFunction of Residence Time and Water Source

"

52 ., .\ ,: ..

~~. A comparison of the sulfate concentrations resulting I

Ifrom two coals under aerobic conditions with distilled water used as the I

slurry media is shown on Figure 36. As would be expected, the sulfate

concentrations in the slurry wastewater are a function of coal Source,

r that is, coal quality. Figure 37 shows the slurry wastewater sulfate

: concentrations over a longer residence time.

~n~. The titanium concentrations in slurry wastewater were

relatively low. Figure 38 shows the titanium concentrations as a func-

tion of residence time and slurry solids concentration.

~~~-r:.2.!?-~.:~~~~ .£!!yir~! ~~ari s~. Fi gures 40, 41, 42, 43and 44 provide comparisons of the parameter concentrations for pH, total

alkalinity, calcium and total hardness, five-day biochemical oxygen

demand and chemical oxygen demand, respectively~ under anaerobic and

aerobic-anaerobic environments has been taken and is currently being

evaluated.

Phase II Results-~~.. --

The objective of this phase of the research program was to determine

the feasibility of utilizing poor-quality water (impaired water) such

as municipal and industrial effluents as the slurry medium. The impaired

water phase was included for two reasons. First, if the impaired water

would be acceptable for use as slurry media, the higher quality water

in the state of origin could be reserved for other purposes, thus avoid-

ing the duplicate cost of quality restoration of the impaired water. :

Second, the use of the impaired water would undoubtedly be more accept-

able in the state of origin.

i

53.~ i: ,

I,.,

700

Coal #2600

500

400r--

~ 300-OJ

~ 200tic-r--~

(/) 100

0 AODS

0 10 20 30 40 50 60

Tlt.1E (HOURS)

Figure 36. Sulfate Concentration in Slurry Wastewater as aFunction of Residence Time and Coal Source

..-

1000

o;j-0 800(/)

1/110

600r--

~!!!:.. 400

OJ+.I

~ 200r--

~ t~B~1S0

0 1 2 3 4 5 6 7 8 9 10

Tlt1E (DAYS)

Figure 37. Sulfate Concentrations ~~-:

in the Slurry Wastewater as aFunction of Residence Time

c

", 54

" ' .

: ,.i

1.0

:=-08-.rnE 0

0.6E~.~ 0 4 'rtI .

oIJ'.-I- 0.2

0.0 ABDS0 10 20 30 40 50 60

.Tlt;IE (HOURS)

Figure 38. Titanium Concentration in SlurryWastewater as a Function of ResidenceTime and Solids Concentration

1.2

1.0 nt

r---rnE 0.8E led Water~ 0.6'.-c:~

.~ 0.4I-

0.2ABOS

0.00 10 20 30 40 50 60

TI~1E (HOURS)

Figure 39. Titanium Concentration in Slurry Wastewateras a Function of Residence Time and Solids 4;";-

Concentration

, ,

55

..' .,

8.0

7.0

6.0

5.0

4.0 .,

:I:a.

3.0

2.0

1.0

O. 0 OB~1S

0 1 2 3 4 5 6 7 8 9 10 11

TI~1E (DAYS)

Figure 40, pH of the Slurry Wastewater as a Function ofResidence Time

120

::;. 100'r-c: .'r--r-- M 80tOO~ur-- toc( u 60r--r--to-+,0)

~5 40

20

00 1 2 3 4 5 6 7 8 9 10 11

TIME (DAYS) .-

Figure 41.. Total Alkalinity Concentrations in the SlurryWastewater as a Function of Residence Time

I" 56

.'\a I, .

600

~ 500 Aerobic

~ 400 Anaerobic IV1 obic :'"..-300ci AnaerobicE

200V1V1Q)

~ 100~'":I: 0 OB ~1S

0 1 2 3 4 5 6 7 8 9 10 11

TI~1E (DAYS)

Figure 42. Calcium and Total Hardness Concentrations in theSlurry Wastewater as a Function of Residence Time

100..-~ 80-0C 60'"EQ)c 40 robiccQ)0)

~ 20C>

~ OBt1S bi cu 0.E 0 1 2 3 4 5 6 7 8 9 10 11Q)

..c:

g TIME (DAYS).r-

caFigure 43. Biochemical Oxygen Demand Concentrations in the -:.-

Slurry l4astewater as a Function of Residence Time

I

", 57

'~ ...

.Aerobic130 .Anaerobic

160r---~140"--

"0c 12roEQ)

"0 10c<IJ0)

;"<' 800

r--

~ 60"-E<IJ-'= 4

L>

2

NBf4S

0 1 2 3 4 5 6 7 8 9 10

TIHE (DAYS)

Figure 44, Chemical Oxygen Demand Concentrations'in theSlurry Wastewater as a Function of Residence

Time

---

--

58',. l. . ..

i

!Some of the Phase II results were included with the Phase I results

for ease of comparison. In general, the use of impaired water does

increase the contaminant concentrations in the slurry wastewater. How-

ever, the resulting contaminant concentrations are not necessarily

additive, that is, the concentration of the contaminants in the slurry,

wastewater are not equal to the sum of the concentrations of the con-

taminant in the distilled water and the treated municipal and industrial

wastewaters. These data are currently being analyzed in detail to

establish the relationships that do occur.

In general, wastewater treatment costs are not linear because of

Ieconomies of scale and other factors. Consequently, although the cost

of water quality restoration would be increased by the use of impaired

water, the increase should not be prohibitively large except possibly

when very poor quality water is used. For example, if lime-soda ash

softening were required for reducing the hardness concentration, the size

of the treatment facilities (basin, etc.) is ordinarily not a function

of the hardness concentration. The chemical costs, however, are depen-

dent on the hardness as are the sludge handling facilities. Thus, the

cost of removing the additional hardness resulting from the use of

impaired water would largely reflect the additional chemical and sludge

handling and treatment costs. This relationship does not strictly hold

true for those concentration intensive processes such as biochemical

oxygen demand removal where oxygen transfer represents a major cost.

However, even in these cases the treatment costs are not linear with

concentration. A mlJch more detailed discussion of this aspect of the ---:,

research program will be included in the final report. .

'-

~

~1 -

I;', 59

"\ ..)

J

Phase III Results

The objective of this phase of the on-going research program was

to determine the treatm~nt measures applicable for restoring the slurry

wastewater quality to acceptable levels, if required. The approach taken

in this phase of the program was to identify those treatment measuresi .applicable for restoring all parameters to acceptable levels. All of .

the treatmert measures would not necessarily De requlrea at eacn liquid-

solids separation site. Similarly, the entire wastewater stream would

not necessarily be treated. For example, a power generation station

firing slurry pipeline delivered coal would have the option of using the

wastewater as part of the circulating water makeup. Thus, both wastewater

streams (the slurry wastewater andcirculating water blowdown) could be

treated on a combined basis, if and when required. The cooling water

makeup requirements are substantially greater than the slurry media water

requirement. For example, a 1600 megawatt (gross) power station requires

about 45 cubic feet per second of makeup water for the cooling system,

whereas the water requirement for the slurry pipeline delivering the

coal required by the station \~ould be about 10 to 15 percent of the cool-

ing water requirement.

The presence of the significant biochemical and chemical oxygen

demand concentrations in the slurry wastewater indicated that biological

treatment for stabilization of the organic material should be investigated.

As previously indicated in the biochemical oxygen demand section of the

Phase I results, the ultimate biochemical oxygen demand curve is unusual.

Substantial acclimation of the microorganisms is apparently required --"":

before a major fraction of the organic material can be stabilized.

However, a portion of the biochemical oxygen demand (that represented

~-

.~ 60

~\ ..,.

.by the first 12-14 days of the ultimate biochemical oxygen demand curve)

was relatively easy to stabilize in the biochemical oxygen demand bottle.

Consequently, this portion of the biochemical oxygen demand would be

expected to be relatively easy to stabilize by biological treatment.

Laboratory activated sludge treatment studies, however, indicated that-,

the biochemical oxygen demand could not be readily stabilized, at least

without remedial measures. To date, the reason for this treatment dif-

ficulty has not been identified. Figure 44 shows the response of a labor

atory activated sludge treatment unit to the slurry wastewater as reflected

by the mixed liquor suspended solids concentration in the activated

sludge aeration basin. Several studies have been conducted to determine

the source of the treatment difficulty without success. These include

addition of the trace elements added in the biochemical oxygen demand

test to the laboratory units, acclimation studies including growth of

microorganisms on synthetic media with gradual addition of the slurry

wastewater, and others. There are several possible reasons for the

treatment difficulty including the lack of a required trace element,

insufficient food supply, !lnd the presence of a toxic material in the

wastewater. Laboratory tests which included the trace elements added

in the biochemical oxygen demand test eliminated the first possibility,

that is, if the required trace elements were present in the biochemical

oxygen demand test and were added to the laboratory activated sludge

units in the same concentration, as was done, the biochemical oxygen

demand should have been stabilized in the laboratory units. The mixed

liquor suspended solids concentration may be used as an indicator of the'-.-,

status of an activated sludge unit.

Studies were conducted to determine if the decreasing suspended

solids concentrations were caused by an insufficient food supply. These

'",..

I..~ 62

'. .,II j-"

studies were negative. Consequently, the presence of a toxic element

or material is the most likely source of the treatment difficulty. In

theory, the toxic material could be either inorganic or organic. Con-

, centrations of the inorganic materials measured all appear to be withinI

acceptable ranges for activated sludge treatment. Although it is pos-

sible that one of the metals, for example, could be concentrated suf-

ficiently to be toxic, the most likely source of toxicity is an organic!! compound in the coal.

Studies have been and are being conducted for determination of the

treatment measures suitable for water quality restoration. The results

to date indicate that current technology is adequate for treatment of

the inorganic contaminants. Additional investigation may be required

concerning the effectiveness of organic contaminant treatment methods

Summary

The current project should provide sufficient data by which the

water quality aspects of coal slurry pipelining can be assessed including

the use of certain categories of impaired water. The use of very poor

quality water, such as raw or primary treated municipal wastewater was

not included in the investigation because of the presence of substantial I

concentrations of pathogenic microorganisms present. Although these

could be deactivated, the work involved in such a program exceeded the

resources of the current project. The use of saline water was not inves-

tigated because the requirement for installing flue gas desulfurization

systems on new electric power plants firing coal appears imminent. Chlo-

ride corrosion is a severe problem in most cases because of the chloride

present in the coal and in the raw water. The additional chlorides from

the saline water that is retained by the coal solids following liquid-

..,I1 ~~~-~~

I"~ 63~ &,.' .'..

tosolids separation would undoubtedly have severe effects on the sulfur

dioxide scrubbing equipment.

The use of secondary-treated municipal and certain industrial waste-

waters appears to be technically feasible. Treatment for removal of the

inorganic contaminants can be accomplished by current technology. Some

increase in treatment costs can be expected but the increase should not

adversely affect a proposed project unless the project economics are

marginal. More complete treatment cost data will be included in the

final project report.

I.

---

I ---

f'f..:"

, i " , .

~

BIBLIOGRAPHY

1. Fryling, Glenn R., Combustion Engineering, Combustion ,

Engineering, Inc., 1966.

2. l~asp, E.J., Progress ~ ~ Slurry Pipelines, Mining

Congress Journal, April, 1976.

3. ~~asp, E.J., and Thompson, T.L., ~ Slurry ~ ~ -EnergyMovers Qf ~ Future, Pipe Line Industry, May, 1974.

4. Hearings BefQre ~ CommitteeQ!).. Interior ~ Insular Affairs

on H.R. 1863, H.R. 2220, J.R. 2553, and H.R. 2986,1975.

5. Hearings Before ~ Subcommittee Q!).. ~ ~ ~ Subcommitteeon Indian Affairs and Public Lands of the Committee on Interior

~-rnSUTar Affairson~1W9;-1977 6. Wasp, E.J., Progress ~ ~ Slurry Pipel'ines, Mining

Congress Journal, April, 1976.

7. Anon, Slurry ~~: ~ ~ Efficient ~ ~ ~Coal, Pipe Line Industry, May, 1975.

8. Frey, D. J., Jonakin, James and Caracristi, V.Z., Utilization

Qi Pipeline~, Combustion, June, 1962.

9. Hanson, V.D., ~ Pipeline~ Completion, Power Engineering,

October 1956.

10. Montfort, J.G., ~ ~ ~ Slurry ~ ~ Eco!!omic ~Technical Success, Pipeline Industry, May, 1972.