Abstract: A process for producing large, regularly-shaped crystalline gypsum solids in a wet calcium-based flue gas desulfurization system is provided. A chemical crystal modifier, preferably an organophosphonate, is added to the gypsum-containing solids slurry produced by the FGD process under forced oxidation conditions at an addition level which promotes the formation of large, regular gypsum crystals that are easily dewatered. The dewatered gypsum is useful in producing gypsum-based building products and the like.

Abstract: Fuel gas streams containing oxygen are treated by a process that performs simultaneous sweetening and absorption of mercaptan compounds. The mercaptan oxidation catalyst and an aqueous alkaline solution and a low vapor pressure liquid hydrocarbon stream contact the fuel gas feed in a mixing vessel to sweeten the mercaptans and absorb resulting disulfides from the gas stream into the liquid hydrocarbon stream. A separation vessel receives the dual phase effluent from the mixing vessel and settles the effluent into three component phases. An upper gas phase provides a treated fuel gas stream, an intermediate hydrocarbon phase provides liquid hydrocarbons containing disulfides for removal from the process, and recycle to the mixing vessel and an alkaline solution drains from the bottom of the settler. The aqueous alkaline solution is pumped back to the mixing vessel in combination with the mercaptan oxidation catalyst.

Abstract: A method for conditioning flue gas to improve the removal of fly ash by an electrostatic precipitator employs a relatively high concentration (4-71/2%) of SO.sub.3 conditioning agent. The SO.sub.3 is formed by combusting sulfur and excess air in a sulfur burner to produce a mixture of air and SO.sub.2 and converting the SO.sub.2 to SO.sub.3 in a catalytic converter. The ratio of air to sulfur is maintained constant over a wide range of SO.sub.3 production rates, and the air is unheated during most production rates. The mixture of air and SO.sub.2 from the sulfur burner is cooled without increasing the volume of the gaseous mixture.

Abstract: This invention relates to methods and apparatus for reducing NOx in combustion effluent gases which comprise a two-stage injection process. NHi precursors (such as liquid-phase urea or ammonium hydroxide, or the like) are injected into the flue gas at temperatures greater than 1400.degree. F. in a first injection zone to reduce NO to nitrogen. This step is followed by injecting a peroxyl initiator, such as a hydrocarbon material (for example, methanol) into the flue gas at temperatures less than 1400.degree. F. to oxidize residual NO to NO.sub.2 in a second injection zone.

Abstract: A method is disclosed for the addition of an oxygen-containing gas under certain defined process conditions, to an off-gas stream derived from an FCC regenerator which is operated in a partial mode of combustion. The off-gas from the regenerator contains 1-6% CO by volume and at least 300 ppm nitrogen compounds comprising NH.sub.3 and HCN. Without the addition of an oxygen-containing gas, roughly 25 percent of the NH.sub.3 and HCN are converted to NO.sub.x in downstream CO boilers. A preferable method of this invention comprises the addition of heated air (20% O.sub.2) into the regenerator off gas to produce an off gas stream having a temperature of 1260.degree. F. to 1500.degree. F.

Abstract: The present invention relates to a process for the in-line hydrolysis of urea. More particularly, the process involves heating an aqueous solution of urea while flowing through a conduit to a temperature and for a time effective to hydrolyze urea to produce hydrolysis products comprising ammonium carbamate, ammonium carbonate, ammonium bicarbonate, and ammonia. The hydrolysis products are useful for the reduction of nitrogen oxides in combustion effluents without the generation of substantial amounts of nitrous oxide.

Abstract: A process for desulfurization of fuel combustion gases and a new reactor wherein the primary flue gas stream containing sulfur oxides and alkaline oxide solids flows into the reactor vessel. A plurality of baffle columns is positioned at the top of the reactor vessel which serve to separate the primary stream into a plurality of first streams containing substantially all of the alkaline oxide solids and a plurality of second streams comprising substantially solids-free gas. The first streams are wetted after which they recombine with the second streams to produce reaction product sulfates and sulfites. The reaction product is substantially dry because the hot second streams cause evaporation of substantially all of the moisture from the wetted first streams.

Abstract: An improved method is described for reducing the nitrogen oxide content of an effluent gas stream wherein the temperature of the gas varies. The improvement comprises alternately, depending upon the temperature of the gas, contacting the gas with(A) formaldehyde when the gas is at an elevated temperature which is sufficient to promote the reaction of formaldehyde with the nitrogen oxide in the gas and to reduce the nitrogen oxide content in the gas to a desired level, or(B) formaldehyde-derived free radicals capable of reacting with nitrogen oxide when the temperature of the gas is lower than the temperature in (A) and the reaction with formaldehyde does not reduce the nitrogen oxide content to the desired level, whereby the nitrogen oxide content of the gas is reduced to the desired level. The free radicals may be generated by reacting formaldehyde with nitrogen or nitrogen oxide in the presence of a catalyst. Preferred catalysts comprise zirconium, cerium, phosphorus, vanadium, or mixtures thereof.

Abstract: A process is described for reducing the nitrogen content of a post combustion gas which comprises the steps of(A) generating NCO free radicals, and thereafter(B) adding the free radicals to the gas whereby the NCO free radicals react with the nitrogen oxide in the gas to form nitrogen and carbon dioxide.The NCO free radicals may be obtained from a variety of sources such as by the catalytic decomposition of cyanuric acid; the reaction of formaldehyde with nitrogen or nitric oxide; the reaction of carbon monoxide with nitrogen oxide or nitrogen or mixtures thereof; or the reaction of methanol with nitrogen in the presence of a catalyst. The NCO free radicals thus generated are effective for reducing the nitrogen oxide content of combustion gases in accordance with the process of the present invention at temperatures from ambient temperature up to about 2000.degree. F.

Abstract: For generating heat, with reduced emission of sulphur and nitrogen oxides, a fuel containing sulphur oxides and nitrogen is effected, the combustion burned and particles of a fresh absorbent are fed into a turbulent zone (9) upstream of an adiabatic desulphurisation zone (8); and the mixture produced is passed into a heat recovery zone (16). Part of the absorbent is recycled to the desulphurisation zone, and the flow rate of fresh absorbent and recycled absorbent is adjusted so that the temperature of that zone is from 750.degree. to 1000.degree. C.

Abstract: An apparatus for removing vanadium from phosphoric acid includes a precipitator that receives vanadium-containing process-feed phosphoric acid and adds an oxidant to the process-feed phosphoric acid, whereupon precipitates containing phosphorus and vanadium are formed in a phosphoric acid filter feed slurry. The solid precipitate is removed by a filter. The filtrate, after optional further oxidation, is contacted to an ion exchange resin to remove additional vanadium from the filtrate to produce a phosphoric acid product of reduced vanadium content. A first portion of the phosphoric acid product is removed from the apparatus for further use. A reducing agent is added to a second portion of the phosphoric acid product, and the reduced acid is used to strip vanadium from the loaded ion exchange resin. The vanadium-loaded second portion of the phosphoric acid is mixed with fresh phosphoric acid and fed to the precipitator.

Abstract: A system and method of converting flue gas pollutants to marketable byproducts of ammonium bisulfite and ammonium bisulfate, which are collected, and to other harmless byproducts which may be safely discharged is provided. The system removes as much particulate material and reaction inhibiting coal tar components as possible via an electrostatic precipitator and then passes the flue gas through a heat exchanger, wherein it is cooled by boiler feedwater. A suds producing detergent is introduced to the flue gas in order to separate any remaining coal tar components from the condensing moisture. Due to the removal of the tar components, sulfur dioxide and nitrous oxide readily dissolve in the condensing moisture when sufficiently cooled.

Abstract: A system for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel is presented. This system utilizes means for determining the lowest achievable nitrogen oxides concentration with respect to a treatment agent to be introduced into the effluent; means for determining whether the baseline nitrogen oxides concentration at the point of introduction is above the lowest achievable nitrogen oxides concentration; and means for introducing the treatment agent into the effluent under conditions effective to reduce the effluent nitrogen oxides concentration.

Abstract: A process is disclosed for removing sulfur from tail-gas emitted from a Claus sulfur recovery process. First, the tail-gas is oxidized so as to convert sulfur therein to sulfur oxides. Oxidized tail-gas is directed into an absorber where a solid absorbent absorbs substantially all the sulfur oxides thereon. After allowing sufficient time for a desired amount of sulfur oxides to be absorbed, absorption is ceased. Next, the solid absorbent containing the absorbed sulfur oxides is contacted with a reducing gas so as to release an off gas containing hydrogen sulfide and sulfur dioxide. Upon releasing sulfur from the solid absorbent, the solid absorbent is regenerated and redirected into the absorber. Sulfur in the off gas emitted by regeneration is concentrated to an extent sufficient for use within a Claus sulfur recovery process for conversion to elemental sulfur. By combining this process with a Claus sulfur recovery process, sulfur dioxide emissions can be reduced to less than about two parts per million.

Abstract: A process for removing nitrogen oxides from an exhaust gas by bringing the exhaust gas containing nitrogen oxides into contact with at least one catalyst selected from a polyvalent metal phosphate, a polyvalent metal sulfate or an aluminate of a transition metal of the 4th period of the Periodic Table in an oxidizing atmosphere containing excess oxygen and in the presence of a hydrocarbon or an oxygen containing organic compound. There is also disclosed a process for removing nitrogen oxides from an exhaust gas which comprises bringing the exhaust gas into contact with the above catalyst and then with an oxidation catalyst.

Abstract: Nitrogen-sorbing and -desorbing compositions and methods of using the same are disclosed, which are useful for the selective separation of nitrogen from other gases, especially natural gas.

Abstract: A waste gas from a chemical process is treated to remove undesirable substances, especially sulphur dioxide, by contacting said waste gas with acidic solution, e.g. industrial waste solution, at pH less than 2 to effect pre-cleaning, and then contacting said waste gas with alkaline solution e.g. seawater.

Abstract: The invention comprises a method and a system for separating very fine particulates from gaseous effluents resulting from the burning of coal or other fossil fuels, or from other combustion processes, such particulates being too small for typical methods to separate. The method utilizes the SO.sub.2, which normally occurs in such gaseous effluents, as a vehicle to enlarge the particles. The gaseous effluent is mixed with water droplets whereby some of the water evaporates; a gaseous ammonia is then injected into the mixture under conditions such as to cause ammonium sulfite to form and to condense on the particles, thus enlarging the particles, and water to condense on the particles, thus further enlarging them; and the now enlarged particles are separated from the gaseous effluent by known methods. DeNO.sub.x and DeSO.sub.x procedures may also be performed on the gaseous effluent prior to the process noted above. Likewise heat recovery may be effected.

Abstract: A process for removing the sulfur oxides from a gas stream by sorbing the sulfur oxide gases in a zeolite and subsequently purging the previously-sorbed sulfur oxide gases by exposing the zeolite to water or water vapor, which is preferentially sorbed on the zeolite. The zeolite is then regenerated by desorbing the water or water vapor from the zeolite. A gas stream having a reduced volume and an increased sulfur oxide gas concentration is isolated and directed to sulfur oxide removal and processing apparatuses.

Abstract: A catalyst and a method for catalytically decomposing nitrogen oxides, wherein the catalyst comprises a zeolite having a mole ratio of SiO.sub.2 /Al.sub.2 O.sub.3 of at least 20, and containing (i) copper ions and (ii) (a) transition metal ions other than copper ions, (b) at least one alkaline earth metal ion selected from calcium, strontium and barium ions, (c) yttrium ions, or (a) silver ions.