Hot potassium carbonate process

Hot potassium carbonate processes are intended for the removal of carbon dioxide, or the co-removal of hydrogen sulfide and carbon dioxide. As a result of the regeneration chemistry, these hot-pot processes are not suitable for the removal of hydrogen sulfide without significant carbon dioxide also in the untreated gas stream. 

In gas reforming plants, e.g. the hot potassium carbonate process for CO removal, sodium metavanadate is used to prevent mild-steel corrosion". Banks reports" that this treatment does not reduce the rather high corrosion rate of Cu-30Ni in these plants. 

It is useful to consider reactive absorbents in the aqueous solution other than amines, e.g. K2CO3. In the hot potassium carbonate process widely practiced for CO2 and H2S removal, the absorbent is simply K2CO3, which ionizes to give Kr " and CO3. When CO2 is present in the gas phase, we have dissolved CO2. Of course, HCOj, OH and H ions are also present... 

Since operation of the hot potassium carbonate process is based primarily on the difference in the solubility of CO2 at high partial pressure (absorber conditions) and that at low partial pressure (stripper conditions), it would be expected to be more efficient with increased CO2 partial pressure in the feed gas. The magnitude of this effect for the pilot-plant operations is shown in Figure 5-25, which includes curves for two outlet-gas compositions. 

The principal advantages of the Catacarb process are production of higher purity product gas than the uncatalyzed hot potassium carbonate process, consumption of less steam than either the potassium carbonate or monoethanolamine systems, and use of smaller equipment (resulting in 20 to 30% savings in capital investment) than the conventional monoethanolamine process (Morse, 1968). 

The Flexsorb HP Process is a promoted hot potassium carbonate process developed and licensed by Exxon Research and Engineering Company. Four commercial plants using the process were reported to be in operation in 1992 (Exxon, 1992). The proeess is similar, with regard to flow schemes and general applications, to the activated Benfield and Cataearb proeesses. It is characterized by the use of a sterieally hindered amine as the activator. 

Corrosion problems and required control methods appear to be quite similar in the Flex-sorb HP and other amine activated hot potassium carbonate processes. During pilot plant tests the corrosion rate was monitored by the use of conoaon coupons and Conosometer probes. In many of the tests a small amount of H2S, ranging from 0.1 to 0.5 mole %, was present in the feed gas. This amount proved adequate to form a protective sulfide layer that inhibited corrosion of carbon steel equipment In tests without H2S or inhibitor, severe corrosion was observed (Say et al. 1984). 

An economic comparison of the Flexsotb HP Process with a conventional amine-promoted hot potassium carbonate process has been made by Goldstein et al. (1984). The basis of comparison was a 20 MM scfd hydrogen plant with a 250 psia absorber. Assumed gas compositions were 19.9 mole % CO2 for the feed and 0.2 mole % CO2 for the product. The calculated results showed a 19% higher solution circulation rate and 11% higher reboUer duty for the conventional amine-promoted hot potassium carbonate design. 

Allied Chemical Coiporation, Solvay Process Division, 1961, TJie Hot Potassium Carbonate Process for Acid Gas Absorption, TechVSer. Kept. No. 6.61. 

An economic study comparing the Fluor Solvent process with the activated hot potassium carbonate process for the removal of carbon dioxide from synthesis gas for the production of ammonia and urea has been reported by Cook and Tennyson (1969). The authors concluded that the process is more economical than activated hot potassium carbonate in all cases stud-... 

The first conunercial scale membrane installation used with CO2 flood EOR was the Sacroc project in West Texas. Injection of CO2 into the field at volumes up to 200 MM.scfd began in 1972. To handle the anticipated increase in the associated gas CO2 concentration, Sacroc installed three C02-removal facilities. The plants were installed in conjunction with three existing processing facilities operated by Sun Exploration Production Co., Chevron U.S.A., and Monsanto. The Sun and Chevron facilities use the Benfield hot potassium carbonate process, and the Monsanto facility uses the monoethanolamine (MEA) process. The Sun hot potassium carbonate plant was designed to reduce the CO2 content of 160 MMscfd of associated gas from 24 to 0.5% CO2, while the Chevron plant was designed to reduce the CO2 concentration of 46 MMscfd of associated gas from 24 to 1.0% CO2. The Monsanto MEA plant was designed to treat 16.5 MMscfd of the 24% CO2 feed gas, reducing its CO2 concentration to 0.01% (Parro, 1984). 

---