Abstract: A process of using solutions containing thiosulfate and/or chloride salt reagents to remove SO3 and H2SO4 acid gases from a flue gas. The solution is injected into a moving volume of flue gas to achieve a droplet size that enables the solution to dry on contact with the flue gas, generating dried particles of the reagent that react with the SO3 and H2SO4 acid gases yielding a salt precipitate. SO2 present in the flue gas may also be absorbed with the solution, with a subsequent reaction yielding bisulfite species that, upon drying of the droplet, react with the SO3 and H2SO4 acid gases to form salts that are removed from the gas. The removal of these acid gases from a flue gas reduce corrosion of equipment used in coal or oil fired power plants downstream of the injection cite.

Abstract: A process of using sodium carbonate and sodium bicarbonate solutions to remove SO3 and other acidic gases or vapors from a flue gas without substantially decreasing the amount of sulfur dioxide also present in the flue gas. Very limited quantities of such solutions are injected into the flue gas in a manner that achieves a controlled droplet size, such that the solution dries on contact with the flue gas and the resulting dry particles of sodium carbonate/bicarbonate are sufficiently small as to have adequate surface area for reacting with SO3, as well as any H2SO4 and, to some extent, HCl vapors in the flue gas.

Abstract: A process of using sodium carbonate and sodium bicarbonate solutions to remove SO3 and other acidic gases or vapors from a flue gas without substantially decreasing the amount of sulfur dioxide also present in the flue gas. Very limited quantities of such solutions are injected into the flue gas in a manner that achieves a controlled droplet size, such that the solution dries on contact with the flue gas and the resulting dry particles of sodium carbonate/bicarbonate are sufficiently small as to have adequate surface area for reacting with SO3, as well as any H2 SO4 and, to some extent, HCl vapors in the flue gas.

Abstract: A hydroseparator for separating particles based on the differences in settling rates such as for separating fly ash from gypsum includes a substantially cylindrical side wall closed at its bottom end by a floor. A laminar upflow is created through the hydroseparator by adding dilution water to the bottom of the hydroseparator and removing most of the added dilution water from the top of the hydroseparator. The remaining volume of liquid is removed in an underflow. The hydroseparator is divided into at least two sections by a baffle that extends about the interior of the side wall. An inlet is disposed in the center of the hydroseparator slightly above the baffle such that the material added to the hydroseparator to be separated is inserted into the section of the hydroseparator completely surrounded by the baffle.

Abstract: A method is provided for removing contaminants, such as sulfur trioxide, sulfur dioxide and hydrogen halides, out of a gas, such as an exhaust gas from a coal or oil fired burner, by injecting a bisulfite containing solution into the gas so that the bisulfite reacts with the sulfur trioxide and/or hydrogen halides in the gas to produce salts and sulfur dioxide, or by injecting a sulfite containing solution into the gas so that the sulfite reacts the sulfur dioxide in the gas to produce bisulfite and this bisulfite reacts with the sulfur trioxide and/or hydrogen halides to result in the formation of salts and sulfur dioxide. The sulfur dioxide in the gas can be washed out of the gas in a downstream wet scrubber. By removing the sulfur trioxide and/or hydrogen halides out of the gas, corrosion of the gas scrubbing apparatus can be reduced.

Abstract: An efficient and cost-effective flue gas desulfurization apparatus for removing sulfur dioxide from waste gases is provided. The apparatus employs a substantially solids-free clear liquor scrubbing liquid and an, organic acid additive capable of maintaining a process pH of 4.5 to 6.0 under inhibited oxidation conditions in the absorber to accomplish sulfur dioxide removal while avoiding scale formation and encrustation. Calcium sulfite relative saturation is controlled to a desired low optimum level by maintaining the circulating calcium ion concentration at a corresponding, optimum low level. A smaller thickener unit area is required to produced calcium sulfite crystals with optimum settling and dewatering characteristics. A reactor system that promotes the formation of small, efficiently dewatered calcium sulfite solids is also provided.

Abstract: An efficient and cost-effective flue gas desulfurization process for removing sulfur dioxide from waste gases is provided. The process employs a substantially solids-free clear liquor scrubbing liquid and an organic acid additive capable of maintaining a process pH of 4.5 to 6.0 under inhibited oxidation conditions in the absorber to accomplish sulfur dioxide removal while avoiding scale formation and encrustation. Calcium sulfite relative saturation is controlled to a desired low optimum level by maintaining the circulating calcium ion concentration at a corresponding optimum low level. A smaller thickener unit area is required to produce calcium sulfite crystals with optimum settling and dewatering characteristics. A reactor system that promotes the formation of small, efficiently dewatered calcium sulfite solids is also provided.

Abstract: A flue gas desulfurization process and system employing a clear scrubbing liquor and an organic acid buffer conducted under forced oxidation conditions to produce a usable gypsum by-product without scrubber scaling and abrasion is provided. Calcium ion concentration and chloride concentration are suppressed to improve limestone utilization, reduce the consumption of organic acids and improve crystal growth. The FGD system includes a limestone reactor for precipitating gypsum separate from the scrubber system which allows the recovery of pure carbon dioxide and a clarifier/softener tank which allows the production of gypsum-free clear scrubbing liquor and a drier gypsum filter cake.

Abstract: A flocculation control system for controlling a feed rate of a flocculant into an aqueous slurry comprises an elongate settling tube having an open lower end for placing into the slurry. An air eductor creates a subatmospheric pressure within the settling tube to thereby draw a sample of the slurry therein to a predetermined location above the slurry level. A control valve hermetically seals an upper end of the settling tube to maintain the subatmospheric pressure therein such that the sample is retained in a quiescent state and in fluid communication with the slurry body. A pressure sensor senses the subatmospheric pressure within the settling tube, and measurements thereof are taken at selectable intervals to develop an initial measurement of said pressure and intermediate lower magnitude measurements of said pressure resulting from the settling of particles from the sample. The pressure measurements enable calculation of the weight concentration and settling velocity of said suspended particulates.

Abstract: An improved magnesium-enhanced lime flue gas desulfurization system is provided which produces the high sulfur dioxide removal level of previous magnesium-enhanced lime flue gas desulfurization systems and additionally produce waste solids that have significantly better properties and are more easily dewatered than the solids produced by known systems. The magnesium-enhanced lime flue gas desulfurization system of the present invention includes a crystallizer-clarifier reaction tank (CCRT) which receives scrubber effluent and functions as a combined reaction tank and thickener. Clear liquor from the CCRT is sent to a scrubber to scrub the flue gas, and a portion of the CCRT--thickened solids are directed to a high pH premix slurry tank (PMST) where the crystallization environment can be controlled by reagent addition and pH. The PMST contents are circulated to the CCRT and are separated to produce a waste solids fraction that is easily dewatered.

Abstract: An improved wet magnesium-enhanced lime flue gas desulfurization system and process are provided. The magnesium-enhanced lime slurry process for removing sulfur dioxide from flue gas to produce gas that is substantially free from sulfur dioxide and calcium and sulfite-containing waste solids is modified to include the addition of process reagents to a separate premix slurry tank which has a controlled, high pH. The addition of slurry formed from the scrubber effluent to the premix slurry tank is controlled to maintain the pH above 10. The premix slurry tank mixture is circulated to a reaction tank for reaction with the scrubber effluent to produce large crystal, easily dewatered waste solids.

Abstract: An improved magnesium-enhanced lime flue gas desulfurization system and process are provided which produce the high sulfur dioxide removal level of previous magnesium-enhanced lime flue gas desulfurization systems and additionally produce waste solids that have significantly better properties and are more easily dewatered than the solids produced by known systems. The magnesium-enhanced lime flue gas desulfurization system of the present invention includes a crystallizer-clarifier reaction tank (CCRT) which receives scrubber effluent and functions as a combined reaction tank and thickener. Clear liquor from the CCRT is sent to a scrubber to scrub the flue gas, and a portion of the CCRT-thickened solids are directed to a high pH premix slurry tank (PMST) where the crystallization environment can be controlled by reagent addition and pH. The PMST contents are circulated to the CCRT and are separated to produce a waste solids fraction that is easily dewatered.

Abstract: High efficiency scrubbing of SO.sub.2 from stack gases by contact with a sodium based liquor is achieved by adjusting the pH of the scrubber liquor supplied to be in the range of 7.00 to 8.00; and a source of such liquor in a dual alkali system is disclosed in which a mixture of slaked lime and limestone is reacted with spent liquor in two stages one of which is at pH above 8.00, the other of which is at a pH below about 6.8 and the pH of the resulting regenerated liquor is adjusted to the desired pH range.

Abstract: A process for the recovery of gypsum as a product of a dual alkali system for regeneration of a sodium base alkaline scrubber liquor in which the liquor reacts with ground limestone in two serially connected sludge blankets containing from 15%-40% solids in a liquor matrix and overlain by a relatively clear supernatant pool. Upon completion of regeneration the liquor is discharged from the second blanket to the scrubber cycle while a proportionate amount of the slurry is further treated to reduce its pH and/or increase its density and/or to displace regenerated scrubber from the matrix after which the slurry is transferred to a separate tank and there oxidized to gypsum then it is filtered. The filtrate is returned to the liquor regeneration cycle and the gypsum recovered as product.

Abstract: A process of regeneration of scrubber bleed liquor discharged from SO.sub.2 gas scrubber in which there are provided two serially connected sludge blankets containing 15-40% finely divided solids in liquor overlain by a relatively clear supernatant liquor. The bleed liquor is introduced into the first blanket along with an aqueous slurry of ground limestone, liquor and limestone partially react in the first blanket then they are transferred to the second blanket for further reaction, after which the liquor is recycled to the scrubber and a proportional amount of reacted limestone is wasted. The liquor has a relatively short residence time in the system on the order of 30-180 minutes while solids residence in the system is on the order of 6 to 24 hours. A special embodiment is provided for use when the first sludge blanket is in a relatively small tank in which only a portion of the bleed liquor is supplied to the first sludge blanket and the balance is injected directly into the second sludge blanket.

Abstract: A dual alkali process and an apparatus for the removal of sulfur oxides from a gas stream containing such sulfur oxides, is disclosed.

Abstract: In a cooperative combination of two scrubbing systems, the first scrubbing system operates upon combustion gases with an aqueous solution to remove hydrogen chloride gas and other chlorine components. The second scrubbing system subsequently operates upon the combustion gases with a sodium-base solution to absorb sulfur oxides. The products of the two scrubbing systems are treated in combination to form a material for disposal and to generate the aqueous scrubbing solution for the chloride scrubbing system.