Ammonium Chloride → Carbon Dioxide

The present invention also provides a process for the substantially total recovery of the alkalinity from soda brine as crystallized sodium bicarbonate without the need for concentrating the soda brine, the soda brine comprising sodium carbonate, sodium bicarbonate and other soluble salts. This process comprises adding sodium chloride to the brine to bring the sodium chloride concentration of the brine to within the range 0.5 to 3.0 equivalents per liter; ammoniating the brine to form ammonium hydroxide by adding ammonia substantially in the amount in accordance with Table II; and carbonating the ammoniated brine to form ammonium bicarbonate by adding carbon dioxide in the amount of one mole of carbon dioxide per mole of ammonia added, plus one mole of carbon dioxide for each mole of sodium carbonate in the brine per liter. This method can also include supersaturating the carbonated brine with sodium bicarbonate and adding sodium bicarbonate seed crystals to relieve the supersaturation of the brine. The supersaturation preferably occurs from the sodium bicarbonate originally present in the brine, from sodium bicarbonate produced as a result of the ammoniating and carbonating reactions, and due to the lowered solubility of sodium bicarbonate resulting from non-alkaline sodium ions which were either present in the brine or added later. Preferably, the ammonium bicarbonate reacts with the sodium bicarbonate in the brine to form sodium bicarbonate and ammonium hydroxide until all of the sodium carbonate present is depleted and whereby the ammonium hydroxide acts as a carbon dioxide carrier. Still more preferably, when the sodium carbonate is exhausted and the supersaturation is relieved by crystallization, the sodium ions present in the brine react with the bicarbonate ions of the ammonium bicarbonate in a double decomposition to form ammonium chloride and sodium bicarbonate, and the solution of sodium bicarbonate suspension is analyzed for its ammonium chloride content and sodium bicarbonate content and the suspension is sent to the separator when the ammonium chloride concentration content exceeds the sodium bicarbonate in solution. Preferably, the reactions of the process occur in a crystallizer and generate a net heat gain, and the temperature of the crystallizer is kept below 40° C. by cooling the brine before processing or during the process, and the crystallized sodium bicarbonate is separated from the saturated mother liquor and portions of the solid bicarbonate are recycled to a slurry tank for use as the seed crystals. and preferably another portion of crystallized sodium bicarbonate is used to regenerate the ammonia from the saturated mother liquor; the rest of the sodium bicarbonate is calcined to form sodium carbonate (soda-ash) and carbon dioxide for the process. In a preferred form this process includes analyzing the separated, saturated mother liquor for its ammonium chloride and sodium bicarbonate content; determining the difference in the equivalent amount of ammonium chloride in solution from the equivalent amount of sodium bicarbonate in the solution; and adding an amount equivalent to the difference of crystallized sodium bicarbonate to the filtered saturated mother liquor. Preferably, the saturated mother liquor with the added sodium bicarbonate in suspension is heated to its boiling point to expedite the liberation of ammonia gas and carbon dioxide using steam, and the method includes heating and cooling the mother liquor using a heat exchanger in a counter current fashion. In a preferred form, there is a total recovery of the ammonia that is recycled, without having to use any of the sodium bicarbonate from the original alkalinity of the brine, there is substantially total recovery of the carbonates and bicarbonates dissolved in the original brine, as sodium bicarbonate crystals, and the final soda free brine is free of contaminants foreign to its original components, additionally comprising further processing the final soda free brine or sending the final soda free brine to waste.

1. concentrationthe ammonium chloride concentration content
2. customis kept below 40° C.
3. temperatureby cooling the brine before processing
4. customduring the process, and the crystallized sodium bicarbonate is separated from the saturated mother liquor and portions of the solid bicarbonate

ORD record

ord-880e4da0b74a48d682d00d646230f21b

Source dataset

uspto-grants-1994_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05275794