Abstract: A flue-gas scrubbing-liquor regeneration process that is based on contacting N-S compounds contained in a flue-gas scrubbing liquor with a lime/limestone solution in a double draw-off crystallizer under suitable pH conditions for precipitating calcium salts of N-S compounds. The precipitated crop is filtered and then hydrolyzed in a sulfuric acid environment to produce gypsum and ammonium sulfate in solution. The hydrolyzed slurry is filtered and the filtrate is neutralized with lime to liberate ammonia gas that is then sparged through a sulfuric acid solution to cause the precipitation of commercial-grade ammonium sulfate.

Abstract: A crystallizer control method and apparatus that generate control signals to manipulated process parameters on the basis of on-line information derived from the measurement of the crystal population in a selected size range in the crystallizer slurry. According to one embodiment of the invention, a particle counter probe is immersed directly into the fines removal circuit of the crystallizer for on-line measurement of crystal population in the 16 to 32 micron size range. The data so collected are then used directly in a standard proportional controller apparatus to manipulate certain operating parameters, such as fines removal rate and feed rate, to effect the desired result. Applying this model-independent control method to a KCl crystallizer, the steady-state conditions of the crystal size distributions were reestablished after an upset in approximately half the time required when no control was applied.

Abstract: The flue gas desulfurization process using a lime or limestone slurry scrubbing solution producing used liquor containing calcium sulfite or sulfate (typically gypsum). Precipitated particles are removed by feeding the used scrubbing liquor to an agitated crystallization zone to grow crystals and directing part of the used scrubbing liquor from that zone to a quiescent crystallization zone, in which particles are settled back into the agitated zone. An underflow stream from the agitated zone containing large crystals is combined with an overflow stream from the quiescent zone, which combined stream is clarified with the fines being returned to the scrubber and the large crystals being removed as a waste product. Apparatus for performing the above process in which the agitated and quiescent crystallization zones form part of a single crystallization vessel, and the two zones are separated by a baffle.

Abstract: A control method and apparatus is provided for the on-line control of crystallizer apparatus and the like to maintain predetermined operating parameters including crystal size distribution and growth rate to achieve stable, predetermined optimum continuous crystallizer operation for optimum crystal product output and purity and to avoid process transients, undesirable cycling behavior, system malfunctions and crystallizer downtime. The control method and apparatus develops on-line control signals for the process control of predetermined manipulated process variables in a closed-loop fashion. The control signals are obtained by the on-line measurement of a preconditioned, classified sample of the population distribution of the crystallizer. A zone sensing or light scattering particle analyzer is utilized by the on-line control apparatus to provide population distribution data to the control apparatus.

Abstract: An apparatus and method for determining crystallization properties of urine to study stone formation therein. A continuous crystallizer is loaded with a fluid, or mother liquor, containing synthetic urine and an aliquot of natural urine. The mother liquor is recirculated from an output of the continuous crystallizer back to an input thereof. After stabilization has been achieved in the crystallizer, the crystal populations of the fluid are measured. Measurement is performed by sampling the contents of the continuous crystallizer and measuring the crystal populations of the sample. In the preferred embodiment of the method, calcium and oxalate ions are added to the fluid to study the formation of calcium oxalate in urine. The recirculating fluid is saturated with calcium and oxalate ions using a saturator loaded with calcium oxalate crystals.