Potassium carbonate solutions regeneration

FIGURE 6.1-5 Equilibrium pressures of CCt. over equeous aminonicotiol and potassium carbonate solutions at regenerator conditions (100 C, 212°F). (From Aslarita et al,23 copyright 1983. Reproduced with permission of Johu Wiley Sons, New York.) SI conversion I psia = 6.895 X Id3 N/m. 

Another widely used stripping operation is the regeneration of a rich potassium carbonate solution from an absorber that removes H2S or CO2 from a gas stream. This process typically uses a 25 wt% K2CO3 aqueous... 

Arsenite Solutions. Addition of essentially stoichiometric proportions of arsenic trioxide to aqueous sodiiun or potassium carbonate solutions results in a marked increase in the rate of absorption and desorption of carbon dioxide, as compared with conventional carbonate solutions. Figure 5-31 illustrates this phenomenon by comparing, qualitatively, the rate of absorption of carbon dioxide at 1 atm partial pressure and room temperature in 40% potassium carbonate and in a typical solution used in the Giarrunarco-Vetrocoke process (Riesen-feld and Mullowney, 1959). The effects of the more rapid absorption and desorption are appreciable savings in regeneration heat, reduction in equipment size, and production of treated gas of higher purity than is possible with ordinary hot carbonate solutions. 

It is claimed that the addition of arsenic tiioxide not only increases the rate of carbon dioxide absorption, but also the carrying capacity of the solution. Jenett (1962) reports that an arsenite solution of 30% equivaloit potassium carbonate content, regenerated with 0.43 lb of steam per gallon, has about 25% more carrying capacity for carbon dioxide than a potassium carbonate solution of the same equivalent concentration. The carbon dioxide content of the gas treated with the arsenite solution is substantially lower than that of the gas treated with the carbonate solution. These observations indicate that arsenic trioxide increases the rate of hydration of carbon dioxide to carbonic acid in the absorption step and also the shift of pH... 

The chemistry of the H2S removal cycle is uniquely based on an arsenic-activated potassium carbonate solution, and is quite complex. The overall reaction mechanism of the absorption-regeneration cycle can be represented in a simplified form by the following equations ... 

Surface oxidation short of combustion, or using nitric acid or potassium permanganate solutions, produces regenerated humic acids similar to those extracted from peat or soil. Further oxidation produces aromatic acids and oxaUc acid, but at least half of the carbon forms carbon dioxide. 

C02 removal is accomplished employing high-pressure potassium carbonate wash with solution regeneration.4... 

Hydrogen peroxide is extracted with water from the reaction liquor the final product so obtained contains some 20 per cent of hydrogen peroxide. Extraction is carried out in a tower in which the water flows in a downward direction over trays while the solution of quinone passes countercurrently upwards. The small amount of water remaining in the quinone phase is removed in another tower by extraction with a concentrated solution of potassium carbonate (33 to 50 per cent) finally all traces of hydrogen peroxide are eliminated by allowing the liquor to pass over a porous material on the surface of which metallic nickel and silver were deposited following this the liquor is filtered and regenerated. 

The monosubstituted sulfonamide from a primary amine has an acidic hydrogen attached to nitrogen. Reaction with potassium hydroxide converts this amide into a soluble salt which, if the amine contained fewer than eight carbons is at least partly soluble. Acidification of this solution regenerates the insoluble amide. 

In the molten carbonate process a molten eutectic mixture of lithium, sodium, and potassium carbonates removes sulfur oxides from power plant stack gases. The resulting molten solution of alkali metal sulfites, sulfates, and unreacted car bonate is regenerated in a two-step process to the alkali carbonate for recycling. Hydrogen sulfide, which is evolved in the regeneration step, is converted to sulfur in a conventional Claus plant. A 10 MW pilot plant of the process has been constructed at the Consolidated Edison Arthur KiU Station on Staten Island, and startup is underway. 

When dealing with unpurified isolates it is not practical to attempt the direct crystallization of chelidonine from the ether mother hquor. It is best to convert the bases into their hydrochlorides and let the sparingly soluble chelidonine salt crystallize from an aqueous solution and recrystallize until it is colorless. Traces of protopine do not interfere in the next step. The regenerated free base is again taken up in ether, and the dried solution (potassium carbonate) is evaporated to a thin sirup. Hot methanol—about five milliliters per gram of residue—is added, the remaining ether is expelled, and the solution inoculated while hot. Chelidonine in large monoclinic tablets separates very rapidly, and since protopine is more soluble in methanol than in ether it is not a contaminant. 

The potassium carbonate system operates mainly isothermal-COg absorption at high pressure and COg release at low pressure. In the absorptim step the pressure is typically about 3.0 MPa (reformer pressure minus pressure losses), and the temperature may be 100°C. The COg is absorbed chemically by the conversion of potassium carbonate to bicarbonate. When the solution pressure is reduced to about atmospheric pressure, part of the COg and water vapor escape. COg release is assisted by steam stripping. The steam is raised in the regenerator reboiler heated by the gas from the LTS shift converter thus, some or most of the heat required by the COg removal process is derived from the heat in the incoming gas. The regenerated solution is returned to the absorber. 

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