Table 812

Flue Gas Desulfurization Operating Conditions OPERATING VARIABLE UNITS

SULFITE EVAPORATOR

TEMPERATURE °F 300

PRESSURE psia 30

SULFATE REDUCTION REACTOR

TEMPERATURE °F 660

PRESSURE psia 32

SULFUR CONVERSION REACTOR

TEMPERATURE °F 300

PRESSURE psia 18.4

SOLVENT (POLYETYLENE GLYCOL), FOR SULFUR CONVERSION REACTOR

MOLECULAR WEIGHT 380-420

FREEZING POINT °F 39-46

SPECIFIC GRAVITY 1.125

VISCOSITY 122°F, est 28

SULFUR SOLUBILITY

68°F, gm/liter 2-10 248°F, gm/liter 27 248°F, gm/liter 35

S03 CONVERSION REACTOR CO-MO ON

CATALYST ALUMINA BASE

TEMPERATURE °F 660

PRESSURE psia 31

Table 8-13

Utility Consumption, per Tons Sulfur Recovered

Table 8-13

Utility Consumption, per Tons Sulfur Recovered

UTILITY

UNITS

AMMONIA SCRUBBING

CONVERSION

TOTAL

ELECTRICITY

kWhr

1883

974

2857

FUEL, mm Btu

mmBtu

14.2

41.2

55.4

STEAM

mmBtu

0

-36.7

-36.7

DISTILLED WATER

MIG

0

0.057

0.057

COOLING WATER

MIG

0

2.86

2.86

PROCESS WATER

MIG

0.095

0

0.095

Table 8-14 Feed and Product Properties

FEED FLUE TREATED SULFUR

Table 8-14 Feed and Product Properties

FEED FLUE TREATED SULFUR

PROPERTY

UNITS

GAS

FLUE GAS

so2

ppm

1600

200

so3

ppm

75

0

AMMONIA LOSSES

ppm

10

CARBONILE MATTER

ppm

<1000

SULFUR PURITY

Wt%

99.7

COLOR

YELLOW

prevent condensation of gas, which results in foaming in the absorber or hydrocarbon contamination of the H2S product.

Rich amine solution is fed to a flash and surge drum. The object of the flash drum is to separate liquid hydrocarbons and dissolved gases from rich amine solution. A hydrocarbon skim is provided to remove any liquid hydrocarbons. This prevents foaming in the amine regenerator and contamination of the sulfur plant where the sulfur plant catalyst is coked. The drum also serves as surge volume for circulating the amine solution. Pressure in this drum is maintained as low as possible to release hydrocarbons from the rich amine solution.

H2S is removed from the amine solution in an amine regenerator, where high temperature and low pressure are used to strip H2S from amine solution.

At low temperature (<180°F), aqueous amine solutions are not too corrosive to carbon steel. Organic acids and decomposition products of DE A contribute to corrosion where surface temperatures are high enough to decompose the salts and release acid.

Table 8-15 Product Composition

COMPOSITION

AMMONIA SOLUTION (RECYCLE) TO AMMONIA

SCRUBBER, WT%

(NH4)2C03 18.9

NH4OH 2.2

HzO 78.6

SULFITIC BRINE FROM AMMONIA SCRUBBER, WT%

NH4HSO3 17.39

(NH4)2S03 12.12

(NH4)2S203 13.40

(NH4)2S04 7.10

H20 49.99

TOTAL 100.00

TREATED VENT GAS, VOL%

H2S 0.47

HzO 11.70

NH3 0.12

C02 22.20

UNCONDENSABLES 65.51

TOTAL 100.00

In amine plants, provisions are made to allow additions of chemicals such as sodium carbonate to neutralize acids and reduce acid-type corrosion. Sometimes, a DEA solution can promote severe H2S corrosion. A filming amine corrosion inhibitor is usually added to prevent contact between corrosive material and metal.

THE AMINE TREATMENT PROCESS

Most refineries have more than one amine contactor, one for low pressure H2S contaminated gases for treating refinery fuel gas and another for treating high pressure recycle gas from units such as hydrocrackers and hydrotreaters.

In LP absorber V-104, the gas feed enters the absorber at the bottom and the circulating amine solution enters the column at top (see Figure 8-4). The amine absorber has approximately 24 plates or a packed column of equivalent length. An aqueous amine solution (18%) enters the column at top, while

LP ABSORBER

DEA REGENERATOR OBA REGENERATOR TRIM COOLER

LP ABSORBER

DEA REGENERATOR OBA REGENERATOR TRIM COOLER

Boiler Feed Water Bfw

Figure 8-4. Amine treatment unit. B.F.W. = boiler feedwater; O.W.S. = oily water sewer.

Figure 8-4. Amine treatment unit. B.F.W. = boiler feedwater; O.W.S. = oily water sewer.

sour gas enters the column at the bottom. Treated gas leaves the column at the top after passing through knockout drum V-105 and is sent out of battery limits. Rich amine solution is collected in flash and surge drum V-103. HP sour gas is similarly treated in column V-101 with 24 plates.

Rich amine from both columns V101 and V-104 is collected in V-103, which acts both as a flash and a surge drum. Liquid from V-103 exchanges heat with regenerator column V-104 bottoms in E-104 and E-105 and enters the amine regenerator column V-104 at the top. The regenerator column has 24 plates and a steam reboiler. In this column, acid gases, such as H2S and C02, are separated as the overhead stream while the regenerated amine solution is pumped with recirculation pump P-103 to high- and low-pressure absorber columns V-101 and V-104. Acid gas from amine regeneration is sent to the sulfur recovery plant as feed. Liquid collected after condensation of V-106 vapor in E-106 is collected in V-107 and sent back to the column as reflux.

The amine solution is cooled in exchangers E-101 and E-102 before entering contactor V-104. The circulating amine solution is dosed with sodium carbonate and antifoaming additives to prevent foaming and corrosion in the contactors.

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  • Harry
    What color yellow means in amine destillation?
    6 years ago

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