Aqueous Carbonate process

The pH-swing process, which was developed in Japan (and later also presented in a patent by Yogo et al. [60]) is another two-step aqueous carbonation process where at first the pH of the solution is lowered so as to enhance the extraction of divalent metal ions. In the second step, the pH is raised to enhance the precipitation of carbonates. A schematic representation of a process utilizing the pH-swing is shown in Figure 14.3 (taken from Ref. [61]), where the principal reactions... 

Sulfur dioxide Aqueous carbonate process (ACP) Sodium carbonate solulien (in spray dryer)... 

Regenerative Aqueous Carbonate Process for Utility and Industrial Sulfur Dioxide Removal... 

Tihe aqueous carbonate process (ACP) has been under development at Atomics International for the last 4% yr. The program aims to establish a technology which eliminates or minimizes the major problems encountered in operating most other sulfur dioxide removal processes. That technology includes the use of sodium carbonate as the scrubbant in the modified spray dryer and the complete regeneration of the sulfur dioxide removal products to recover elemental sulfur and produce sodium carbonate for reuse in the spray dryer-scrubber. 

Aqueous Carbonate Process, 606 Lime Slurry Spray Dryer Processes, 607 Duct Spray Dryer Process, 614 Gas Suspension Spray Dryer Process, 614 Spray Dryer Byproduct Disposal and Use, 615... 

To avoid the cost and disposal problems of once-through processes employing alkali metal compounds, a considerable amount of research and development effort has been expended on techniques for regenerating this type of absorbent. Processes used employ precipitation of insoluble compounds (double alkali), and thermal decomposition (Wellman-Lord and Elsorb). Processes under development or which have been investigated include precipitation of insoluble compounds (zinc oxide), low-temperature reduction of sulfite (citrate and potassium formate processes), high-temperature reduction (aqueous carbonate process), electro-dialysis (SOXAL), and electrolytic (Stone Webster/Ionics Process). Descriptions of some of these processes are provided in subsequent sections. 

The Aqueous Carbonate Process (AGP) was developed by Rockwell International and is now licensed by ABB PlSkt. In this process, the SO2 is removed by passing the flue gases through a spray dryer where efficient contact with a fine mist of an aqueous sodium carbonate is achieved. The SO2 reacts with the sodium carbonate (Na2C03) to form sodium sulfite (Na2S03), some of which is further oxidized to sodium sulfate (Na2S04>. 

Binns, D., and Aldrich, R. G., 1977, Design of the 100 MW Atomics International Aqueous Carbonate Process Regeneration FGD Demonstration Plant, paper presented at the EPA Symposium on Flue Gas Desulfurization, Hollywood, FL, Nov. 8-11. 

Gehri, D. C., and Gylfe, J. D., 1973, The Atomics International Aqueous Carbonate Process for SO2 Removal—Process Description and Pilot Test Results, paper No. 73-306, presented at the APCA Meeting in Chicago, IL. 

In the commonly used Welland process, calcium cyanamide, made from calcium carbonate, is converted to cyanamide by reaction with carbon dioxide and water. Dicyandiamide is fused with ammonium nitrate to form guanidine nitrate. Dehydration with 96% sulfuric acid gives nitroguanidine which is precipitated by dilution. In the aqueous fusion process, calcium cyanamide is fused with ammonium nitrate ia the presence of some water. The calcium nitrate produced is removed by precipitation with ammonium carbonate or carbon dioxide. The filtrate contains the guanidine nitrate that is recovered by vacuum evaporation and converted to nitroguanidine. Both operations can be mn on a continuous basis (see Cyanamides). In the Marquerol and Loriette process, nitroguanidine is obtained directly ia about 90% yield from dicyandiamide by reaction with sulfuric acid to form guanidine sulfate followed by direct nitration with nitric acid (169—172). 

A.lkali Carbonates. The hot carbonate process was originally developed by the U.S. Bureau of Miaes, usiag aqueous 25—30 wt % solutions of potassium carbonate for the removal of hydrogen sulfide and carbon dioxide. 

GirhotolAmine Process. This process developed by the Girdler Corporation is similar in operation to the alkali carbonate processes. However, it uses aqueous solutions of an ethanolamine, ie, either mono-, di-, or triethanolamine. The operation of the Girbotol process depends on the reversible nature of the reaction of CO2 with monoetbanolamine [141-43-5] to form monoethanolamine carbonate [21829-52-7]. 

Developing agents must also be soluble in the aqueous alkaline processing solutions. Typically such solutions are maintained at about pH 10 by the presence of a carbonate buffer. Other buffers used include borate and, less frequendy, phosphate. Developer solubiUty can be enhanced by the presence of hydroxyl or sulfonamide groups, usually in the A/-alkyl substituent. The solubilization also serves to reduce developer allergenicity by reducing partitioning into the lipophilic phase of the skin (46). 

Schwel-vorgang, m. low-temperature process of carbonization, -wasser, n. an aqueous liquid from the low-temperature carbonizing process, containing ammonia, phenols, etc. foiil water, -werk, n. low-temperature carboniza tion plant. 

Molten salt extraction residues are processed to recover plutonium by an aqueous precipitation process. The residues are dissolved in dilute HC1, the actinides are precipitated with potassium carbonate, and the precipitate redissolved in nitric acid (7M) to convert from a chloride to a nitrate system. The plutonium is then recovered from the 7M HNO3 by anion exchange and the effluent sent to waste or americium recovery. We are studying actinide (III) carbonate chemistry and looking at new... 

Quintelas, C., Sousa, E., Silva, F., Neto, S., and Tavares, T., Competitive biosorption of ortho-cresol, phenol, chlorophenol and chromium (VI) from aqueous solution by a bacterial film supported on granular activated carbon, Process Biochemistry, 4, 2087-2091, 2006. 

Accent [Aqueous carbon compound effluent treatment] A process for oxidizing organic contaminants in aqueous streams by catalyzed oxidation with sodium hypochlorite. The catalyst is promoted nickel oxide, which retains active oxygen at its surface, as well as adsorbing the organics. Developed by ICI Katalco and first offered in 1998. 

To test the validity of the extended Pitzer equation, correlations of vapor-liquid equilibrium data were carried out for three systems. Since the extended Pitzer equation reduces to the Pitzer equation for aqueous strong electrolyte systems, and is consistent with the Setschenow equation for molecular non-electrolytes in aqueous electrolyte systems, the main interest here is aqueous systems with weak electrolytes or partially dissociated electrolytes. The three systems considered are the hydrochloric acid aqueous solution at 298.15°K and concentrations up to 18 molal the NH3-CO2 aqueous solution at 293.15°K and the K2CO3-CO2 aqueous solution of the Hot Carbonate Process. In each case, the chemical equilibrium between all species has been taken into account directly as liquid phase constraints. Significant parameters in the model for each system were identified by a preliminary order of magnitude analysis and adjusted in the vapor-liquid equilibrium data correlation. Detailed discusions and values of physical constants, such as Henry s constants and chemical equilibrium constants, are given in Chen et al. (11). 

ZJ at 293.15°K and the K2CO3-CO2 aqueous solution of tTTe Hot Carbonate Process with temperatures from 343.15°K to 413.15°K and concentrations up to 40 weight percent equivalent potassium carbonate. The success of the correlations suggests the validity of the model for aqueous electrolyte systems of industrial interest. 

Related to the fixation of C02, electrochemical carbon , which is prepared by converting carbon halides (e.g. polytetrafluoroethylene) to carbon, is recently attracting attention for its technological applicabilities. Non-aqueous electrolyte solutions are often used in the electrochemical carbonization processes [13]. The use of non-aqueous electrolyte solutions is also popular in electrochemical organic syntheses, as is apparent in Ref. [14], although not dealt with in this book. 

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