Co-Combustion tests of coal and biomass using a pilot-scale oxy-fuel

CFB

Yewen Tan, Lufei Jia and Yinghai Wu

Presented at the 3rd IEA Oxyfuel Combustion Conference, September 15, 2013

Oxy-CFB Advantages Fuel flexibility: coal, petcoke, biomass, waste and

co-firing In-situ sulfur capture with limestone Lower requirement for flue gas recycle when

external heat exchanger is used to cool return solids

Easier retrofit for existing CFB units Operation flexibility Co-firing biomass with CCS will have negative

CO2 emission levels

CanmetENERGY Oxy-FBC Research Facilities

A mini CFB test bed: 50 kW, can also be used for calcium/chemical looping cycle studies A pilot-scale CFB test bed: 0.8 MW Several TGAs and tube furnaces Analytical instruments

The 0.8 MWth Pilot-Scale CFB Can operate in air-firing and oxy-firing modes

with smooth transition between them Various fuel feed stocks can be used along

with limestone addition Internal diameter: 40 cm, height: 8 m Four movable water cooled tubes can used

for combustor temperature adjustment External heat exchanger currently being built Tested inlet O2 concentration is up to 30% All auxiliary gas streams are switched to RFG

during oxy-fuel tests

0.8MWth oxy-fuel pilot scale CFBC

Operating Procedure Warm up with natural gas using sand as bed material

until 800 C Start feeding test fuel Ramping up test fuel feed rate while cutting back on

NG until air-firing of test fuel is established Transition from air-firing to oxy-firing by cutting back

air flow while increasing flow rates of oxygen and recycled flue gas

Perform oxy-fuel test Transition back from oxy-firing to air-firing System shut down

Coal and Wood Pellets Analyses Wood pellet Lignite Bituminous Sub-bituminous

Proximate analysis

Moisture 9.52 13.23 6.7 6.08

Ash 0.38 11.33 14.18 24.72

Volatile 76.46 33.86 25.10 26.87

Fixed carbon 13.64 41.58 54.02 42.33

Ultimate analysis

Carbon 44.7 54.6 66.34 52.2

Hydrogen 5.36 3.50 3.64 3.05

Nitrogen 0.12 0.81 1.59 0.79

Sulphur <0.05 0.63 0.56 0.30

Oxygen (diff) 39.91 15.92 7.00 12.85

LHV, MJ/kg 17.49 20.74 25.28 19.98

Test Conditions Bituminous Sub-bituminous Lignite

Coal%/Wood

%

50/50 65/35 80/20 65/35 80/20 65/35

Fuel feed rate,

kg/hr

79.6±4.3 73.4±3.6 63.2±2.8 87.3±0.3 81.3±1.5 88.1±0.3

O2 in feed

gas, %

24.4±0.4 24.1±0.6 23.9±0.4 24.9±0.3 24.9±0.5 24.1±0.5

O2 flow rate,

kg/hr

118.2±4.2 116.9±5.6 100.1±4.8 126.9±4.1 117.1±5.0 115.8±5.3

O2 in flue gas,

%

2.1±0.8 2.6±1.1 1.5±0.9 2.8±0.4 4.0±0.8 2.2±0.9

CO2 in flue

gas, %

85.2±3.1 85.3±4.2 80.0±6.2 92.2±0.5 92.7±0.9 92.6±3.0

Flue gas

recycle ratio,

wt.%

68.3 68.8 65.2 72.6 75.7 70.0

Freeboard

temperature, °C

920 895 893 905 913 874

Superficial

velocity, m/s

4.9 4.7 4.3 4.7 4.7 4.4

Sulfur capture

ratio, %

Issues with SO2 analyzer 76.1 85.7 88.7

Concentrations of O2 and CO2 for 35% wood and 65% Genesee coal

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10

Elapsed Time, h

O2

and

CO

2, %

O2 CO2

Concentrations of CO, NO and SO2 for 35% wood and 65% Genesee coal

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 1 2 3 4 5 6 7 8 9 10

Elapsed Time, h

CO

an

d N

O,

pp

m

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

SO

2, %

CO NO SO2

Concentrations of O2 and CO2 for 35% wood and 65% Boundary Dam coal

0

10

20

30

40

50

60

70

80

90

100

8 9 10 11 12 13 14 15 16

Elapsed time, h

O2

and

CO

2, %

O2 CO2

Combustor freeboard temperature as a function of the amount of co-fired wood pellet in bituminous coal

0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14

Time, hour

Tem

per

atu

re, d

eg. C

35% wood50% wood20% wood

Measured SO3 concentrations

Bituminous coal Measured SO3 concentrations, ppmv

20% wood, 80% coal <0.16

35% wood, 65% coal 2.23

50% wood, 50% coal 1.12

Genesee

100% coal 2.27

20% wood, 80% coal 2.76

35% wood, 65% coal 1.86

Emissions of VOCs for bituminous and wood mixture, (µg/m3) Wood% / bituminous%

VOC 20/80 35/65 50/50 0/100 Dichlorodifluoromethane (FREON 12) < 0.3 < 0.3 < 0.3 < 0.35

Chloromethane 6.25 3.29 5.84 22.0 Vinyl Chloride 0.24 < 0.2 < 0.2 < 0.2 Bromomethane 1.07 4.85 3.45 1.94 Chloroethane 0.22 < 0.15 < 0.15 < 0.16

Trichlorofluoromethane (FREON 11) < 0.15 < 0.16 < 0.17 < 0.18 Acetone (2-Propanone) < 0.67 2.12 0.87 1.23 1,1-Dichloroethylene < 0.15 < 0.16 < 0.17 < 0.2

Iodomethane < 0.22 2.58 0.96 0.35 Carbon Disulfide 13.5 4.31 3.48 4.75

Methylene Chloride(Dichloromethane) < 0.3 < 0.32 < 0.33 < 0.35 1,1-Dichloroethane < 0.18 < 0.19 < 0.2 NA

trans-1,2-Dichloroethylene < 0.15 < 0.16 < 0.17 NA cis-1,2-Dichloroethylene < 0.15 < 0.16 < 0.17 NA

Chloroform < 0.16 < 0.18 < 0.18 < 0.18 1,2-Dichloroethane < 0.1 < 0.11 < 0.12 < 0.1

Methyl Ethyl Ketone (2-Butanone) < 0.54 < 0.58 < 0.59 < 0.7 1,1,1-Trichloroethane < 0.21 < 0.23 < 0.23 < 0.2 Carbon Tetrachloride < 0.24 < 0.26 < 0.26 < 0.35

Benzene 1360 55.8 45.6 31.1 1,1,2-Trichloroethane < 0.24 < 0.26 < 0.26 < 0.16 1,2-Dichloropropane < 0.16 < 0.18 < 0.18 < 0.4

Trichloroethylene < 0.16 < 0.18 < 0.18 < 0.5 Dibromomethane < 0.15 < 0.16 < 0.17 1.94

Bromodichloromethane < 0.16 < 0.18 < 0.18 < 0.2 cis-1,3-Dichloropropene < 0.15 < 0.16 < 0.17 < 0.35

trans-1,3-Dichloropropene < 0.1 < 0.11 < 0.12 < 0.2 Dibromochloromethane < 0.13 < 0.15 < 0.15 < 0.4 Methyl Isobutyl Ketone < 0.3 < 0.32 < 0.33 < 0.2

Methyl Butyl Ketone (2-Hexanone) < 0.45 < 0.49 < 0.5 < 0.4 Toluene 42.6 4.59 2.10 < 0.18

Ethylene Dibromide < 0.15 < 0.16 < 0.17 < 0.2 Tetrachloroethylene < 0.27 < 0.29 < 0.3 < 0.1

Chlorobenzene < 0.16 1.20 0.40 < 0.16 1,1,1,2-Tetrachloroethane < 0.15 < 0.16 < 0.17 < 0.4

Ethylbenzene < 0.21 < 0.23 0.28 < 0.5 m / p-Xylene < 0.22 0.79 0.69 1.94

Styrene < 0.18 < 0.19 < 0.2 < 0.2 o-Xylene < 0.22 < 0.24 < 0.25 < 0.35

Bromoform < 0.21 < 0.23 < 0.23 < 0.2 1,1,2,2-Tetrachloroethane < 0.21 < 0.23 < 0.23 < 0.2

1,2,3-Trichloropropane < 0.22 < 0.24 < 0.25 < 0.2 1,3-Dichlorobenzene < 0.3 < 0.32 < 0.33 < 0.4

Emissions of metals for bituminous and wood mixture, (µg/m3)

Wood% / bituminous% Element 20/80 35/65 50/50

Al 80.6 < 57 < 53 Sb < 2.5 < 2.8 < 2.6 As < 2.5 < 2.8 < 2.6 Ba < 15 < 17 < 16 Be < 0.5 < 0.6 < 0.5 B 148 144 167 Cd 1.8 1.4 0.92 Ca 400 362 250 Cr < 1 < 1.4 < 1.3 Co < 0.5 < 0.6 < 0.5 Cu < 2 < 2.8 < 2.6 Fe < 150 < 170 < 158 Pb < 1.2 < 1.4 < 1.3 Mg 99.4 56.8 < 26 Mn < 2 < 2.8 NA Mo < 2.5 < 2.8 < 2.6 Ni 7.4 2.9 < 2.6 P < 25 < 28 < 26 K < 200 < 227 NA Se < 5 < 5.7 < 5.3 Ag < 1.2 < 1.4 < 1.3 Na 250 206 165 Sr < 1.5 < 1.7 < 1.6 Tl < 2.5 < 2.8 < 2.6 Ti 4.4 7.2 4.1 U < 2.5 < 2.8 < 2.6 V < 2.5 < 2.8 < 2.6 Zn 18.1 15.6 < 2.6 Hg 0.25 0.29 0.11

Conclusions

Stable oxy-cofiring conditions were achieved over relatively long operation hours The effect of wood pellets on CFB

freeboard temperature is minimal Stack sampling showed that SO3

concentrations were very low on our facility

Conclusions

Stack samplings for volatile organic compounds and metals also revealed low emission rates for both pollutants Test results confirmed one of the main

advantages of oxy-fuel CFB, which is its fuel flexibility

Future Work

Install the external heat exchanger Conduct high O2 concentration tests Initiating pressurized oxy-CFB work Fundamental research on specific

aspects of oxy-CFB combustion