11 2 8 liquor clarification

7/29/2019 11 2 8 Liquor Clarification

1/22

11.2.8 Liquor Clarification Process

11.2.8.1 Facility and Process Description

The Liquor Clarification Process in Tayan Bayer Process involves a

number of key steps, including bauxite storage, bauxite grinding,

digestion, heat recovery from digester slurry, mud settling and

mud washing of insoluble residue, liquor filtration for clarification,

liquor cooling and mud filtration for land dumping.

The Liquor Clarification Process is described along the Process Flow

Diagram specified in Subsection 11.2.2 Scheduled maintenanceshut-down will be carried out every three (3) months.

The accumulated capacity of the Washed Bauxite at the Bauxite

Storage Area of 3,000 m2 provided in the Alumina Site shall be

5,760 WMT at maximum, equivalent to an approximately two (2)

days consumption. The Washed Bauxite stocked in the Bauxite

Storage Area shall be periodically carried by the sloping Belt

Conveyer (CBS-BC-101 depicted in Drawing No. CBS-100-0001-A1)

and the Shuttle Conveyer (CBS-BC-102) to the Bauxite Storage

Tanks (CBS-TK-102, CBS-TK-103 and CBS-TK-104 depicted in

Drawing No. CBS-100-0001-A1) with a volume of 300 m3 each,

equivalent to eight (8) hours reserve of the Washed Bauxite for

avoiding midnight feeding.

From the respective Bauxite Storage Tanks (CBS-TK-102, CBS-TK-

103 and CBS-TK-104), the Washed Bauxite shall be continuously

charged to the two (2) operating Rod Mills (BSC-RM-101 and BSC-RM-102 depicted in Drawing No. BSC-100-0001-A1, and BSC-RM-

103 depicted in Drawing No. BSC-100-0002-A1), each rated at 40 -

45 DMT/Hr in operation, by corresponding variable speed Belt

Conveyer with a weight scale (depicted in Drawing Nos. BSC-100-

0001-A1 and BSC-100-0002-A1). The remaining one (1) Rod Mill

shall be down for spare. The Washed Bauxite shall be ground up to

2 mm passing size using the Rod Mills to ensure sufficient solid-

liquid contact during a digestion phase.

T-11.2.8_1/22


2/22

At the inlet of each Rod Mill, the Washed Bauxite shall be mixed

with hot aluminate liquor, often referred to as spent liquor or

mother liquor, which shall be taken from after-mentioned HeatExchanger provided in a heat recovery area, in order to form slurry.

The charging liquor to each Rod Mill shall be pumped from the

Relay Tank (BDH-TK-101 depicted in Drawing No. BDH-100-0001-

A1), whose flow rate shall be controlled with a flow meter in

proportion to a bauxite consumption rate. The ground bauxite

slurry from each Rod Mill shall be charged through each launder to

the Slurry Relay Tank (BSC-TK-201 depicted in Drawing No. BSC-

100-0002-A1).

The 56% (equivalent to approximately 950 gpl) solids slurry shall

be pumped from the Relay Tank (BSC-TK-201) directly to a series of

the three (3) operating Digesters, each furnished with an agitator

(BDH-D-201, BDH-D-202 and BDH-D-203 depicted in Drawing No.

BDH-100-0004-A1). The remaining one (1) Digester shall be down

for cleaning or spare. Heated spent liquor (often, referred to as

mother liquor) shall be simultaneously introduced to the first

Digester (BDH-D-201 or BDH-202) through one (1) operating Heat

Exchanger (BDH-H-105 or BDH-H-106 depicted in Drawing No.

BDH-100-0003-A1) where it shall be indirectly heated to

approximately 180C by a live steam of approximately 1 MPaG

supplied from the Boiler. In this digestion stage, the bauxite slurry

shall be mixed with this heated spent liquor. Three (3) Digester

vessels shall have approximately forty (40) minutes holding time at

an average temperature of 140C which is measured at the inside

of the first Digester. This would be adequate time for extraction of

solid gibbsite in bauxite and for desilication of reactive silica ofmost Tayan bauxites.

The digestion effluent slurry of approximately 135C from the last

Digester (BDH-D203 or BDH-D-204 depicted in Drawing No. BDH-

100-0004-A1) shall be cooled down at temperature of

approximately 102 - 106C through the heat recovery stage.

T-11.2.8_2/22


3/22

In this heat recovery stage where is correspond to a counter

current system between hot digester effluent and hot spent liquor,

three (3) Flash Tanks provided in series (BDH-FT-201, BDH-FT-202and BDH-FT-203 depicted in Drawing No. BDH-100-0004-A1) and

three (3) Heat Exchangers provided in series (three (3) of BDH-H-

101, BDH-H-102, BDH-H-103 and BDH-H-104 depicted in Drawing

No. BDH-100-0002-A1 for operating) shall be employed. Each

flashed steam through a series of three (3) stages flashing shall be

used to heat the incoming spent liquor supplying to each Heat

Exchanger.

The incoming spent liquor, which shall be pumped from after-mentioned vacuum cooling facilities, shall be step-wise heated

from 83C to approximately 112C by the flashed steam generated

in each Flash Tank.

The digestion effluent shall be passed to each Flash Tank provided

in series through an internal downward-streamed piping with a

throttle at its edge, for avoiding flashing at the piping inside and

mitigating entrainment and abrasion to the tank inwards.

The spent liquor flow rate of 650 680 m3/Hr shall be measured

with a flow meter. An approximately 6% of the spent liquor of

approximately 90C at the outlet of the first Heat Exchanger (BDH-

H-101 or BDH-H-102) shall be poured into the Liquor Relay Tank

(BDH-TK-101 depicted in Drawing No. BDH-100-0001-A1) for

preparing the ground bauxite slurry as explained above. The

remaining 94% of the spent liquor shall be flowed into the second

and third Heat Exchanger provided in series to heat up toapproximately 112C by the corresponding flashed steam from

each Flash Tank. The heated spent liquor shall be further heated up

to approximately 180C by live steam through the Heat Exchanger

(BDH-H-105 or BDH-H-106 depicted in Drawing No. BDH-100-0003-

A1), as above mentioned, in order to ensure the digestion

temperature of 140C.

T-11.2.8_3/22


4/22

The four (4) Heat Exchangers (BDH-H-101 to BDH-H-104) shall be

provided for recovery of the flashed steam; three (3) for operating

and one (1) for stand-by in operation. The Heat Exchangers shallbe interchanged for tube cleaning during the scheduled

maintenance shut-down. After cleaning, tube-cleaned Heat

Exchanger shall be provided to allow continuous operation of the

digestion and heat recovery facilities as a spare.

The two (2) Heat Exchangers (BDH-H-105 and BDH-H-106 depicted

in Drawing No. BDH-100-0003-A1) shall be periodically changed in

operation for chemical tube-cleaning, using two (2) automatic

three-way valves provided in spent liquor piping connected tobefore and after the Heat Exchangers. All Heat Exchangers shall be

of the same shell & tube type with four passes.

Three (3) Booster Pumps (BDH-P-103A, BDH-P-103B and BDH-P-

103C depicted in Drawing No. BDH-100-0003-A1) shall be provided

between the live steam heaters and the flashed steam heaters

(depicted in Drawing No. BDH-100-0003-A1). The two (2) Booster

Pumps shall be for operating, and the remaining one (1) shall be

for stand-by or back up for the former Pumps (BDH-P-102A and

BDH-P-102B depicted in Drawing No. BDH-100-0002-A1).

For flashing down of the digestion slurry, the Barometric Condenser

(BDH-FT-401 depicted in Drawing No. BHD-100-0006-A1) with the

two (2) Ejectors (BDH-J-501 and BDH-J-502) shall be provided. A

part of the flashed steam introduced to the first Heat Exchanger

(BDH-H-101 or BDH-H-102) from the last Flash Tank (BDH-FT-203)

shall be fed to the Barometric Condenser for condensation of theflashed steam and shall be condensed by contacting with overflow

liquor from the fourth stage Washer (BRW-TH-104, BRW-TH-105 or

BRW-TH-106 depicted in Drawing Nos. BRW-100-0002-A1 and BRW-

100-0003-A1). Heated liquor discharged from the Barometric

Condenser shall be returned to the Washer (BRW-TH-103 or BRW-

TH-104) for avoiding auto-precipitation.

T-11.2.8_4/22


5/22

And then the slurry in the last Flash Tank (BDH-FT-203) shall be

controlled and maintained to nearly atmospheric pressure with air

injection into the Barometric Condenser. The pressure to becontrolled shall be in the range of -30 to -60 mmHg.

As bauxites usually contain some organic carbons in the form of

humic substances, they will be reacted with hot caustic liquor and

be decomposed to gas and soluble substances. Namely, tenuous

gas containing hydrogen and uncondensed components will be

continuously generated in the Digesters and Flash Tanks, and the

gas will be accumulated in the Digesters and Heat Exchangers.

Therefore, the Digesters shall be periodically degassed by manualto eliminate it. And the gas generated from the Flash Tanks shall be

continuously eliminated through a series of piping provided outside

of the Heat Exchangers, flowed to the Barometric Condenser and

finally degassed by two Ejectors (depicted in Drawing No. BDH-

100-0006-A1).

The condensate drain (DWA) generated from the operating Heat

Exchanger (BDH-H-105 or BDH-H-106 depicted in Drawing No.

BDH-U-0001-A1) shall be directly returned to the Boiler as

condensate water for Boilers after monitored with a conductive

meter. Meanwhile, the condensate drain (DWB) generated from

each flashed steam heater shall be flowed from high temperature

heater to low temperature heater through a level control valve. The

condensate from the last Heat Exchanger shall be pumped to DWB

Tank (DSS-TK-102 depicted in Drawing No. DSS-100-0001-A1) and

primarily used as mud washing water after monitoring with a

conductive meter. When each drain (DWA and DWB) iscontaminated with spent liquor flowing through heater tubes, it

shall be dumped to the washer by changing stream direction of

three way valves (depicted in Drawing No. BDH-U-0001-A1).

T-11.2.8_5/22


6/22

Scale deposited on the wall of the heater tubes equipped in the

digestion and heat recovery areas shall be periodically eliminated

by sulfuric acid cleaning adding corrosion inhibitor (depicted inDrawing No. APS-100-001-A1). The main composition of the scale is

sodalite denoted by rational formula of

3(2SiO2Al2O3Na2O)Na2XnH2O(S).

IWB water shall be firstly charged into the rubber-lined Tank (APS-

TK-101 or APS-TK-102 depicted in Drawing No. APS-100-0001-A1)

for adjusting sulfuric concentration, and then sulfuric acid solution

of 98% packed in a liquid one (1) ton container shall be poured into

the Tank, adding inhibitor. Diluted sulfuric solution of 15% shall be

circulated between specific Heat Exchanger tubes and the Tankthrough rubber-lined piping. After cleaning, the circulating liquid

shall be discharged to the Tank (APS-TK-101 or APS-TK-102). And

spent liquor shall be charged into the Tank (APS-TK-101 or APS-TK-

102 depicted in Drawing No. APS-100-0001-A1) for neutralization of

the rubber-lined piping and tubes. Waste slurries including

neutralized spent liquor shall be transferred to the Mud Slurry Feed

Tank (BRF-TK-102 depicted in Drawing No. BRF-100-0101-A1) for

filtration. Finally, all relating piping including tubes shall be flushed

by drain (DWB) or pressurized air.

Safety sequence shall be provided for protecting from the

unacceptable upper limit of temperature and pressure. In the case

of abnormality of temperature and/or pressure, namely in

emergency cases, all pumps in the digestion area shall be

automatically stopped by interlock sequence and control valves in

the same area shall be simultaneously closed except the flashed

steam control valves for blow off to the atmosphere (depicted inDrawing No. B-P-A-0200-004). This interlock sequence shall be also

worked by operating a corresponding switch manually, if an

operator implements an emergency shut-down.

T-11.2.8_6/22


7/22

Slurry from the bottom of the last Flash Tank (BDH-FT-203) at

temperature of 102 - 106C shall be pumped to the mud settling

area through the Sand Catcher (BDH-SN-301 depicted in DrawingNo. BDH-100-0005-A1). As the slurry contains coarse sand particles

of 1 - 5 mm in size, they shall be separated by an inclined spiral

classifier equipped in the Sand Catcher. Separated sand particles

shall be discharged to an adjoining Tank (BDH-TK-301 depicted in

Drawing No. BDH-100-0005-A1) in which the sand shall be mixed

with mud slurry came from mud washing circuit. The mixed slurry

shall be transported to the mud filtration stage using the inverter

Pump (BDH-P-301A or BDH-P-301B depicted in Drawing No. BDH-

100-0005-A1).

The slurry pumped from an upper zone of the Sand Catcher,

containing approximately 3% solids, shall be continuously charged

to the two (2) single deck Thickeners (or Settlers) operating in

parallel (BOS-TH-101, BOS-TH-102 or BOS-TH-103 depicted in

Drawing No. BOS-100-0001-A1). The remaining one (1) Thickener

(or Settler) shall be for spare or stand-by for manual cleaning. The

three (3) Settlers shall not be converted to mud washer.

Achieving good performance for high compaction of mud and

clarification of liquor in the feed stream by gravity sedimentation,

conventional cable-arm or cable torque thickeners with a central

bottom discharge shall be provided as the settlers and the

succeeding washers. These thickeners shall be supported by a

stationary steel or concrete center column and raking arms shall

be attached to a driving cage which rotates around the center

column.

The settlers called as a conventional cable-arm thickener or cable

torque thickener, in which cables shall be attached to upper

trusses near liquid surface to move two (2) rake arms with plural

blades, which are hinged to drive structure, shall allow the rakes to

be raised when excessive torque is encountered. And also the

settlers shall be furnished with drive assemblies, a drive lifting unit,

feed well, and radial inside launder.

T-11.2.8_7/22


8/22

The slurry from the Sand Catcher shall be tangentially fed to the

feed well through a feeding launder at which bubble entrained in

the slurry during transportation shall be separated. Emulsionflocculants, effective to goethite bauxite, shall be continuously also

added to the slurry existed in the feed well at three (3) feeding

points for forming flocculation. The emulsion flocculants of high

polymer type shall be used as it enters the settlers to aid in

flocculation, compaction and consolidation of mud. Further lime

slurry as a clarification aid shall be occasionally added to the

operating settlers according to turbidity of settler overflow liquor.

All underflow pumps of the settlers shall be located, whereverpossible, in adjacent to a discharging center cone of each settler.

The overflow from the settlers shall be removed in a peripheral

inner launder with level flat weirs provided inside each settler. The

overflow, which contains solids of approximately 100 ppm, shall be

pumped directly from the Overflow Relay Tank (BOS-TK-102

depicted in Drawing No. BOS-100-0001-A1) to mud filtration area

for final clarification.

The underflow from the settlers containing mud solids shall be

combined with overflow from the second mud washing stage and

fed to the first mud washing stage (depicted in Drawing No. BRW-

100-0001-A1).

The mud washing circuit (depicted in Drawing Nos. BRW-100-0001-

A1, BRW-100-0002-A1 and BRW-100-0003-A1) for reduction of soda

content in liquor shall be designed as a four (4) stage, counter-

current decantation system (CCD) utilizing four (4) operating singledeck settlers. A total of six (6) similar washing vessels shall be

provided; four (4) for operating and two (2) for spares for

maintenance or manual cleaning, so that there shall always be a

four (4) stage for the washing. Stream direction of each underflow

and overflow shall be changeable by changing piping when timing

of thickener cleaning.

T-11.2.8_8/22


9/22

Two (2) pump stations consisting of three (3) centrifugal pumps

shall be provided for two (2) washers; one station for overflow

transportation, the other for underflow transportation. Two (2) ofthree (3) centrifugal pumps shall be used for the respective

washers and the remaining one (1) shall be used as common

stand-by.

As described above, the liquor in the second or third stage washer

shall be recycled through the Barometric Condenser located in the

heat recovery areas.

Wash water (DWB) shall be fed to the last stage through theFiltrate Tank (BRF-TK-101 depicted in Drawing No. BRF-100-0101-

A1) for the mud washing. Other miscellaneous liquid containing

soda shall be introduced into intermediate stage. Piping shall be

provided to bypass any washing vessels.

Emulsion flocculants shall be continuously added to all operating

washers (depicted in Drawing No. TAP-100-0001-A1) in the range of

30 100 ppm. The flocculants packed in a one (1) ton liquid

container shall be mixed with the plant drain water (DWC) and

shall be stored in the Stock Tank with an agitator (TAP-TK-101

depicted in Drawing No. TAP-100-0001-A1).

This flocculants shall be diluted to 1 - 3% concentration by mixing

the flocculants handled with a plunger pump and DWC water

measured with a flow meter by means of an inline mixer. The

diluted solution shall be stocked in the stock Tank with a viscosity

meter (TAP-TK-101) and shall be continuously fed to each thickenerin the mud settling and mud washing areas through single

transportation piping for each thickener.

In the operation of the mud settling and mud washing, the rake

torque of each operating thickener shall be continuously monitored

and shall be controlled by changing each rate of the underflow

volumetric flow and flocculants adding, periodically measuring mud

level and overflow turbidity.

T-11.2.8_9/22


10/22

The underflow from the last washer shall be charged to the Mud

Slurry Tank with an agitator (BRF-TK-102 depicted in Drawing No.

BRF-100-0101-A1) through the Tank (BDH-TK-301) at which thesand shall be picked up, as mentioned above. And then the slurry

containing the sand shall be fed to the one (1) operating Pressure

Disc Filter (BRF-F-101A or BRF-F-101B depicted in Drawing No. BRF-

100-0101-A1).

The effluent from the settlers and the first washer shall be flowed

into the Overflow Tank (BOS-TK-102 depicted in Drawing No. BOS-

100-0001-A1) through bridge launders connecting with the three

(3) settlers and pumping of the first washer overflow.

Tri-calcium aluminate particles (3CaOAl2O36H2O or TCA) shall be

added to the Overflow Tank (BOS-TK-102) as a filter aid for

reduction of filtration resistance at the liquor filtration stage.

TCA as a filter aid shall be prepared by reacting slaked lime with

sodium aluminate liquor according to the following reaction:

3Ca(OH)2(s) + 2NaAlO2(l) + 4H2O(l) 3CaOAl2O36H2O(s) +

2NaOH(l)

As the first step, lime packed in a 500 kg bag container shall be

mixed with drain water (DWC) by batch-wise manner in the Re-

slurry Tank with an agitator (LSP-TK-101 depicted in Drawing No.

LSP-100-0001-A1). The resultant lime slurry treated with a constant

concentration of approximately 500 gpl shall be held in the Stock

Tank with an agitator (LSP-TK-102) and shall be continuously fed tothe insulated Tank with an agitator (TCA-TK-101 depicted in

Drawing No. TCA-100-0001-A1), simultaneously adding filtered

liquor (depicted in Drawing No. PFS-100-0004-A1) and pure caustic

liquor (depicted in Drawing No. CSS-100-0001-A1). These three (3)

liquids shall be controlled by a cascade control linking with each

flow meter.

T-11.2.8_10/22


11/22

As liquor discharged from the Overflow Tank (BOS-TK-102 depicted

in Drawing No. BOS-100-0001-A1) contains traces of ultra fine solid

up to approximately 100 ppm, the liquor shall be continuouslypumped to the liquor filtration stage for final clarification (depicted

in Drawing Nos. PFS-100-0003-A1 and PFS-100-0004-A1).

The Pressure Plate Filters (PFS-F-101 to PFS-F-104 depicted in

Drawing No. PFS-100-0003-A1) shall be employed; three (3) for

operating and one (1) for stand-by. The Filters (PFS-F-101 to PFS-F-

104) shall mainly comprise a vessel, vertical filter elements inside

the vessel, a top reservoir for backflushing, five (5) pneumatic

valves for full automatic operation and automatic control system.The Filters shall be automatically operated by opening and/or

closing the pneumatic valves sequentially under the automatic

control system such as the below table Schematic Cycle of

Vertical Filters in Operation. The cycle time shall be approximately

one (1) hour. Each cycle shall be composed of leveling, cake

formation, filtering, decompressing and discharging. For the

leveling, liquor charging pipe through the Feed Valve V1 shall be

vertically inserted near top level of the leaf plates. And for the

decompressing, two (2) pipes, which are independently and

vertically inserted inside the filter, shall be employed through the

Decompressing Valve V3 and the Overflow Valve V4 respectively.

Each length of three (3) inside pipes is as follows; Decompression

Pipe > Overflow Pipe > Liquor Charging Pipe.

The time schedule of three (3) operating Filters shall be set so that

the liquor is continuously poured into the Filter(s) based on flow

rate control.

T-11.2.8_11/22


12/22

Schematic Cycle of Vertical Filters in Operation

Cycle Step 1 2 3 4 5

Cycle Function Leveling Cake

formation

Filtrating Decompressin

g

Discharging

Cycle Time (min.) 0 0 - 2 2 - 58 58 - 59 56 - 60

Valve Valve NameV1 Feed valve Open Open Open Close Close

V2 Backflow valve Close Open Close Close Close

V3 Decompressin

g valve

Close Close Close Open Open

V4 Overflow valve Close Close Close Open Open

V5 Extraction

valve

Close Close Close Close Open

T-11.2.8_12/22


13/22

In the period of cake formation, liquor pumped from the Overflow

Tank (BOS-TK-102) shall be filled into the vessel to form cake

adhered to filter clothes and cloudy filtrate shall be flowed to theTank (PFS-TK-701 depicted in Drawing No. PFS-100-0004-A1)

through the Backflow Valve V2. The discharged liquor with turbidity

shall be recycled through the Overflow Tank (BOS-TK-102 depicted

in Drawing No. BOS-100-0001-A1). In the period of filtrating, solids

shall be blocked onto the filter clothes to form cake, while clear

filtrate (turbidity: less than 15 mg/l) shall be flowed into the top

reservoir above the filter through the external manifold and finally

to the Filtrate Tank (PFS-TK-104 depicted in Drawing No. PFS-100-

0004-A1). In the period of decompressing and discharging,pressure inside the vessel shall be fallen to the normal value, and

then fresh cake shall be fallen off the filter clothes by filtrate

flushed back from the top reservoir and discharged to the Cake Re-

slurry Tank (PFS-TK-101 and PFS-TK-102 depicted in Drawing No.

PFS-100-0003-A1). In the period of leveling, liquid level shall be

adjusted, a cushion of air in the top of vessel shall be reestablished

and then a new filtration shall be started.

The fresh cake collected in the Cake Re-slurry Tank (PFS-TK-101 and

PFS-TK-102) shall be pumped to the third or fourth washing stage in

order to recover the soda associated with the mud (depicted in

Drawing No. BRW-100-0002-A1).

During the stand-by time, the filter clothes shall be cleaned using

hot and high caustic aluminate liquor with 200 grams caustic per

litter at 95C (depicted in Drawing No. PFS-100-0003-A1). The hot

caustic liquor for cleaning shall be circulated between the saidFilter and the Cloth Cleaning Tank (CSS-TK-105 depicted in Drawing

No. PFS-100-0003-A1) for an hour. The caustic liquor for cleaning

shall be always heated by indirect steam and shall be manually

supplemented adding new pure caustic liquor at a low level of the

Cloth Cleaning Tank (CSS-TK-105).

T-11.2.8_13/22


14/22

The precious filtrate from the Filter shall be run to the Filtrate Tank

(PFS-TK-104 depicted in Drawing No. PFS-100-0003-A1), if it is less

than 15 ppm. The precious filtrate shall be charged to the vacuumFlash Tanks (VHI-FT-101, VHI-FT-102, VHI-FT-103 and VHI-FT-104

depicted in Drawing No. VHI-100-0001-A1) provided in the liquor

cooling stage.

At the liquor cooling stage, the precious filtrate at temperature of

approximately 100C from each Filter, namely pregnant liquor,

shall be heat-transferred to the spent liquor of approximately 58C

from the Stock Tanks (PLS-TK-101, PLS-TK-102, PLS-TK-103 and PLS-

TK-104 depicted in Drawing No. PLS-100-0001-A1) by a countercurrent heat-transfer system using a series of the Flash Tanks (VHI-

FT-101, VHI-FT-102, VHI-FT-103 and VHI-FT-104) and the Heat

Exchangers (VHI-H-101, VHI-H-102, VHI-H-103 and VHI-H-104

depicted in Drawing No. VHI-100-0002-A1) of shell and tube type

and shall be cooled down for controlling an initial precipitation

temperature of 66C of the Chain-1 of the Hydrate Production

Process. The system is the same as the heat recovery system in

the bauxite digestion stage.

The pregnant liquor shall be continuously pumped to a series of

four (4) vacuum Flash Tanks (VHI-FT-101, VHI-FT-102, VHI-FT-103

and VHI-FT-104 depicted in Drawing No. VHI-100-0001-A1). Each

flash steam from the three (3) Flash Tanks (VHI-FT-101, VHI-FT-102

and VHI-FT-103) shall be used to heat up the spent liquor in a

series of the three (3) operating indirect Heat Exchangers (VHI-H-

101, VHI-H-102, VHI-H-103 or VHI-104 depicted in Drawing No. VHI-

100-0002-A1).

Flashing at the fourth Flash Tank (VHI-FT-104) shall be used to

control the liquor temperature for the Chain-1s precipitation by

condensing a desired quantity of flashed steam in the Barometric

Condenser (VHI-CD-101 depicted in Drawing No. VHI-100-0001-A1).

T-11.2.8_14/22


15/22

The pregnant liquor from the last Flash Tank (VHI-FT-104) shall be

charged to Precipitators in the Chain-1, Chain-2 and Chain-3

through the Relay Tank (VHI-TK-101). The spent liquor ofapproximately 58C from the Stock Tanks in the Chain-1 (PLS-TK-

101, PLS-TK-102, PLS-TK-103 and PLS-TK-104 depicted in Drawing

No. PLS-100-0001-A1) shall be pumped to the first Heat Exchanger

(VHI-H-101 or VHI-H-102). And the spent liquor of approximately

82C discharged from the last Heat Exchanger (VHI-H-103 or VHI-

H-104) shall be charged to the Digester Pumps (BDH-P-102A and

BDH-P-102B depicted in Drawing No. BDH-100-0002-A1).

A total of the four (4) Heat Exchangers of shell and tube type (VHI-H-101, VHI-H-102, VHI-H-103 and VHI-H-104) shall be provided;

three (3) for operating and one (1) for spare for maintenance and

manual tube bowling. Tubes of the Heat Exchanger shall be

cleaned with caustic liquor from the Heat Exchanger (CSS-H-101

depicted in Drawing No. CSS-100-0002-A1) every scheduled

maintenance shut-down in order to reduce fouling to the heater

tubes.

The pregnant liquor shall be continuously introduced into each

Flash Tank with a tangential stream which shall be passed through

a top-covered circler launder provided inside of each Flash Tank to

form a falling film. In addition, for preventing the entrainments

such as droplets and mist containing caustic soda, an internal

demister made of metal fiber shall be bedded at the upper inside

of each Flash Tank. The demister shall be washed with pure caustic

using internal spray nozzles periodically.

T-11.2.8_15/22


16/22

Noncondensable gas, which is mainly carbon dioxide, generated

from the pregnant liquor during flushing down shall be vented from

each Flash Tank (VHI-FT-101, VHI-FT-102 or VHI-FT-103) to therespective Heat Exchangers (VHI-H-101, VHI-H-102, VHI-H-103 or

VHI-H-104) through its succeeding flash steam line. Furthermore,

the noncondensable gas shall be transferred to the last Flash Tank

(VHI-FT-104) through the flash steam line connected with each

Heat Exchanger, gone to the Barometric Condenser (VHI-CD-101

depicted in Drawing No. VHI-100-0001-A1) and finally eliminated

from the two (2) stage steam Ejectors (VHI-J-101, VHI-J-102 and

VHI-J-103 depicted in Drawing No. VHI-100-0001-A1).

The direct-contact countercurrent Barometric Condenser (VHI-CD-

101) furnished with multi stage impingement plates internally, in

which vapor is condensed by rising against a rain of cooling water,

shall be provided for cooling the pregnant liquor came from the last

Flash Tank (VHI-FT-401). Inner pressure of the last Flash Tank shall

be controlled by an air suction volume using a control valve for

maintaining the precipitation temperature of 66C in the Chain-1.

Sedimentation treatment water (IWA) from the Water Pool-1 shall

be directly pumped to the Barometric Condenser (VHI-CD-101) and

shall be discharged by gravity to the Hot Well (W-TK-101) provided

beneath the Barometric Condenser. The noncondensable gas shall

be also discharged to the Hot Well through the Ejector (VHI-J-103).

Condensate drain from each Heat Exchanger shall be gone to the

Condensate Tank (VHI-TK-103 depicted in Drawing No. VHI-U-0001-

A1) and finally fed to the DWC Relay Tank (DSS-TK-101 depicted inDrawing No. DSS-100-0001-A1). It shall be utilized mainly as

washing water for hydrate filtration. The condensate drain

discharged from the Condensate Tank (VHI-TK-103) shall be

continuously monitored with a conductive meter. If the conductivity

of the condensate drain will be over an upper limit, the

contaminated condensate shall be automatically dumped to the

mud washing stage with three directions valve.

T-11.2.8_16/22


17/22

If the increasing of evaporation capacity is required to maintain the

water balance in the Bayer Process when heavy rain falls, vapor re-

compressive evaporator (VRCE) shall be intermittently operated(described in Drawing No. B-P-A-0200-015). SDK Yokohama Plant

has operated its Bayer Process without evaporation unit. However,

considering heavy tropical rainfall in Indonesia, it shall be provided

in Tayan plant which is estimated as the evaporation capacity of 10

tons per hour.

The VRCE process has designed by Sumiju Plant Engineering Co.,

LTD. The process and equipment will be installed in space beneath

the Flash Tanks in the liquor cooling area.

Spent liquor discharged from the liquor cooling stage shall be

passed to the first evaporation section in the VRCE which shall be

composed of four (4) evaporation sections in a body. The liquor

shall be circulated through the falling film evaporator. As the liquor

shall be flowed down through an inner plate, it shall be heated by

re-compressed vapor which condenses inside the plate and goes to

the sump. The liquor becomes progressively more concentrated as

it passes through the units. Finally, it shall be discharged from the

fourth section. The vapor leaving the evaporator shall be passed

through an internal demister and then entered into a blower where

it shall be adiabatically compressed. The compressed and heated

vapor shall be used as a source of heat for all evaporation sections.

Chemical cleaning shall be periodically performed by H 2SO4 with

corrosion inhibitor for precipitated sodalite scale and water

washing for sodium fluoride scale at the evaporation stage. Thewashing piping shall be equipped in the evaporation section. The

liquor from evaporation shall be supplied to the suction side of the

Digester Pumps (BDH-P-102A and BDH-102B depicted in Drawing

No. BDH-100-0002-A1).

T-11.2.8_17/22


18/22

The underflow slurry from the last washer (BRW-TH-105 or BRW-TH-

106) shall be pumped to the Relay Tank (BRF-TK-102 depicted in

Drawing No. BRF-100-0101-A1) for the mud filtration. At this mudfiltration stage, pressure disk filters shall be adopted to prevent

environmental contamination such as groundwater infiltration and

spill caused by rainfall as possible. The pressure disc filter has

been designed based on laboratory experiments with BOKELA who

is an engineering firm in Germany

A pressure-filtered mud cake with approximately 30% moisture

content, which is corresponding to permeability coefficients of 10 -4

to 10-6, shall be capable of reducing dumping alkalinity andimpounding it into the cake.

Two (2) Pressure Disk Filters (BRF-F-101A depicted in Drawing No.

BRF-100-0101-A1 and BRF-F-101B depicted in Drawing No. BRF-

100-0102-A1) shall be provided. A conventional rotary disk filter

shall be housed inside the respective horizontal pressure vessels

that shall be filled with compressed air up to 4 - 6 kg/cm3 supplied

from air compressors during operation.

The Pressure Disk Filters (BRF-F-101A and BRF-F-101B) shall be

provided for the mud filtration available continuously to achieve

the filtered cake with 30 - 31% moisture content. One (1) Pressure

Disk Filter shall be for operating and the other one shall be for

spare or chemical cloth-cleaning with hot caustic liquor periodically.

The mud slurry from the Relay Tank (BRF-TK-102 depicted in

Drawing No. BRF-100-0101-A1) shall be pumped into the filter vatwithout an agitator via slurry feed pipes in the pressurized vessel.

The main components of variable-speed disk filter shall be disk

filter of approximate 3.2 m in diameter with six (6) filter disks, each

arranged with twenty (20) filter segments, pressure vessel, cake

discharge sluice, filtrate receiver and blow-off tank.

T-11.2.8_18/22


19/22

The filter segments of the disk shall be connected to individual

process zones; namely cake formation zone, dewatering zone, cake

discharge zone by gas blow-back and filter cloth cleaning zone, bymeans of openings in a control plate provided inside a control

head.

Focusing on one single filter segment of the rotary filter under the

main drive activating and disk rotating in normal speed, the

process-steps shall be taken place one after the other. After

submerging a cell of filter in the slurry, the cell shall be connected

to the cake formation zone according to filtration pressure

difference. While, the slurry shall be entered into the filter segmentand the solids shall be kept back by the filter cloth where a filter

cake shall be formed. Mother liquor or filtrate shall be flowed via

filtrate pipes and the control head out of the pressure vessel to the

Filtrate Receiver Tank (BRF-TK-107A and BRF-TK-107B) and be

separated there from accompanying gas.

After the cake formation zone, the dewatering zone shall be

followed where compressed gas displaces pore liquor and flows

through the filter cake. The gas as well as the filtrate from the

dewatering zone shall be also transported to the filtrate receiver.

As the last process step, the cake shall be discharged after

finishing of the cake dewatering. The filter media of the segment

shall be inflated by a sharp gas blow-back so that the filter cake

falls off and is directed to a conveyer with a deflector plate. The

conveyer transports the cake to the discharged sluice where the

cake shall be sluiced out of the pressure vessel periodically. The

cake discharged sluice shall be a chamber sluice consisting of anupper and a lower slide gate. It can be operated with a timer.

A cloth wash spray bar for filter cloth cleaning shall be situated

underneath the deflector plate. The filter cloth, now free of filter

cake, shall be cyclically free from particle adhesion with the cloth

wash spray bar. Afterwards the filter cell shall be submerged again

in the slurry, and the filtration process shall be started anew.

T-11.2.8_19/22


20/22

In this control cycle, the cake formation shall be controlled by

adjusting a filter speed with cascade sequence of feeding flow rate

and level of the cell.

Steam cabin shall cover a part of the filter area and form a

separated room with live steam inside the vessel for reduction of

cake moisture and cloth washing. Although steam injection for

further dewatering shall not be applied at this stage, the steam

cabin and related piping shall be provided.

The filtrate from the Pressure Disk Filter shall be fed to the Filtrate

Tank (BRF-TK-101) via the Filtrate Receiver Tank (BRF-TK-107A andBRF-TK-107B) by gravity and recycled to the last mud washing

stage. Mud cake from the Pressure Disk Filter shall be conveyed to

the Cake Yard by the two (2) Belt Conveyers (BRF-BC-101 and BRF-

BC-102 depicted in Drawing No. BRF-100-0101-A1). The piled cake

in the Cake Yard will be periodically transported to the Bauxite

Residue Dumping Site by trucks. Air Compressors (BRF-CP-101 to

BRF-CP-109 depicted in Drawing No. BRF-100-0103-A1) shall be

provided near the Pressure Disk Filters.

The operation of the mud filtration stage shall be controlled with

local panel switches and shall be monitored at the Central Control

Room (CCR).

The treatment facility for seepage water and rainy sewerage from

area where bauxite residue will be dumped, shall be provided at

the appropriate location in the Bauxite Residue Dumping Site

based on the attached PFD (Drawing No. B-W-A-002-003) andEquipment List. Electric power for this facility shall be supplied

from Substation in Mining Site. Signal of indication and alarm of the

facility shall be sent to CCR.

T-11.2.8_20/22


21/22

11.2.8.2 Plot Plan

Plot Plans for the Liquor Clarification Process are attached inChapter 11.2.4 for the WTNCs reference.

11.2.8.3 Process Flow Diagram

Process Flow Diagrams for the Liquor Clarification Process are

attached in Chapter 11.2.2 for the WTNCs reference.

11.2.8.4 Piping and Instrument Diagram

Piping and Instrument Diagrams for the Liquor Clarification Process

are attached in Chapter 11.2.3 for the WTNCs reference.

11.2.8.5 Heat & Mass Balance Sheet

Heat & Mass Balance for the Liquor Clarification Process shall be

referred to Table 10-3-2-5-1 and 10-3-2-5-2 attached in Chapter

11.2.1 for the WTNCs reference.

11.2.8.6 Equipment List

Equipment List for the Liquor Clarification Process is attached in

Chapter 11.7 for the WTNCs reference.

11.2.8.7 Technical Requirements

1) Technical requirements for all equipment shall be referred toEquipment List attached in Chapter 11.7. And the technical

requirements for main equipment shall be referred to drawings

also attached in Chapter 11.2.5 and 11.2.6.

2) The maintenance manholes and access doors of tanks shall be

provided based on each P&ID.

T-11.2.8_21/22


22/22

3) The height of each outlet of the Flash Tank (BDH-FT-203) and

the Flash Tank (VHI-FT-104) shall be referred to Drawing Nos. B-

P-A-0501-004 and B-P-A-0501-016, respectively.

4) The quantities of piping with 150 mm and larger in nominal

diameter shall be minimized.

5) As no drawings of small tanks with the volume not exceeding

100 m3 and their agitators are attached, the WTNC shall provide

them based on Drawing Nos. B-P-V-0300-023 and B-P-V-0300-

025.

6) The Evaporator described in Subsection 11.2.8.1 is based on

the design basis of VRCE designed and manufactured by Sumiju

Plant Engineering Co., LTD. However, the WTNC may provide

the different type of evaporator designed based on the

following design conditions and manufactured strictly.

a) Steam Pressure of Plant Liquor

P = (0.068046)(10^(6.733(2057.6+0.2084N/0.891.0

106/80)/(273+T))

Where: P: Steam pressure (atm)

N: Caustic concentration (g/l)

T: Temperature (C)

b) Feed Liquor

Temperature T = 85C

Caustic Concentration N (aOH) = 160 gpl

Dissolved Al2O3 (l) = 75 gpl

Solid Al2O3 (s) = 0 gpl

Specific Gravity = 1.220

Specific Heat = 0.850

c) Amount of Evaporation = 10 tons per hour

T-11 2 8 22/22

11 2 8 liquor clarification

Documents