Dipa

Hot Carbonate

DIK Solution M Solution S Solution

Perox Am-gas

Stretford

Takahax

Dry Box

Lime

Dow, U.S.A. Dow, U.S.A. Dow, U.S.A. Dow, U.S.A. Dow, U.S.A.

Am-gas, Canada

W.C. Holmes and Company, U.K. Tokyo Gas Co. and Nittetsu Chemical Engineers Co.

Moderately selective Moderately selective Selective Selective Selective

Moderately selective Selective

Selective

Moderately selective Not selective

Recovers as sulfur Recovers as (NH4)2SO4

Recovers as sulfur

Recovers as sulfur

Precipitates ZnS Ca(SH)2 soluble;

CaS precipitates Sulfur recovery, for ppm H2S streams Useful for ppm H2S;

only mod. selective Product releases H2S on decomp. oxidizes to sulfate Reagent, not adsorbent; forms CuS and H2, but requires expensive regeneration

Table 5.20.12 tabulates the values of S. The values for the factor C are based on the number of boxes in the series being used at the time of operation and on the assumption that the flow is reversed during purification.

The designer must use the appropriate size of iron oxide particles for the required pressure drop across the bed. The empirical relationship was developed for one system (Prasad 1984) and can be used as an approximation for similar systems:

Perry (1984) recommends an allowable pressure drop of 1-2 psi/ft at 800-1000 psig and linear gas velocities of 5-10 ft/min. Typical operating conditions are shown in Table 5.20.13.

Activated Carbon Process

Activated carbon is an effective catalyst for the oxidative conversion of H2S in hydrocarbon gas streams to elemental sulfur under mild conditions. I.G. Farbenindustrie developed the first process to exploit this capability. Such a unit may process up to 200,000 cu ft/hr of water-gas, with a pressure drop of 25in of water.

Reactions of H2S and SO2

The Sulfreen process designed by Lurgi (Germany) and Elf Aquitaine (France) reduces residual sulfur compounds in tail gases from Claus plants for sulfur recovery from natural gas. Alumina or carbon catalysts

TABLE 5.20.11 TECHNICAL ADVANTAGES AND DISADVANTAGES FOR AMINES USED AS H2S ADSORBENTS

Amine

Advantages

Disadvantages

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