Disclosed are methods and systems for removing submicron particles from a gas stream, in particular from urea prilling off-gas, wherein a Venturi ejector is used. A method comprises contacting a gas stream containing submicron particles in a Venturi ejector with an injected high velocity scrubbing liquid to provide a pumping action, wherein the scrubbing liquid has an initial velocity of at least 2 m/s and wherein the ratio of scrubbing liquid and gas flow is between 0.0005 and 0.0015 (m.sup.3/h)/(m.sup.3/h). The disclosure also pertains to a prilling tower having a gas stream treatment system comprising a Venturi ejector at the top of the prilling tower, and to a method of modifying an existing prilling tower.

Disclosed is an apparatus for separating amine gas from mixed gas, the apparatus including: a washer column through which mixed the gas passes; and a main adsorber column through which the mixed gas passing through the washer column passes. According to the present invention, the apparatus can remove amine gas more effectively and increase the lifetime of an adsorbent by allowing the mixed gas including the amine gas to pass through the washer column and the adsorber column.

An exhaust gas treatment apparatus which includes a denitration device, a dust collector, and a desulfurization device in order, respectively, in a flow path of exhaust gas discharged from a boiler, wherein a heavy-metal component removal device is provided in the exhaust gas flow path between the dust collector and the desulfurization device. This device is provided with: an absorption tower including a nozzle which sprays acidic absorption liquid on the exhaust gas, a tank which stores liquid which has absorbed a heavy metal, and a pump which supplies the nozzle with the liquid in the tank; a neutralizing tank which neutralizes the liquid drawn from the absorption tower; and a separator which separates the neutralized liquid into a solid and a liquid component. Since a small amount of heavy metal can be removed in the absorption tower, re-emission of the heavy metal by the desulfurization device is prevented.

A liquid hydrocarbon desulfurization system having at least one processing unit, and preferably an initial and an end processing unit. Each processing unit having a reactor assembly and a sorption system. An aqueous system directs aqueous into the reactor assembly together with liquid hydrocarbon, wherein the two are mixed using shear mixers. An adsorbent system provides adsorbent to the sorption column to adsorb the oxidized sulfur resulting through the mixing of the liquid hydrocarbon with the aqueous. A system having multiple processing units is disclosed, as well as systems for transferring adsorbent and providing aqueous. A plurality of methods is likewise disclosed.

A complex malodor removing equipment includes: a neutralizing module which dissolves a portion of malodor-causing substances, in malodorous gas introduced from malodor-producing equipment, in liquid water and removes same, which includes an acidity neutralizing module that introduces an alkaline substance from outside and removes an acidic malodor-causing substance from the malodor-causing substances, and an alkaline neutralizing module that introduces an acidic substance from outside and removes an alkaline malodor-causing substance from the malodor-causing substances, and which connects the acidity neutralizing module and the alkaline neutralizing module; and a balancing module which dissolves the remainder of the malodor-causing substances, in the malodorous gas introduced from the neutralizing module, in water and removes same, which includes an oxidation balancing module that introduces an oxidizing agent from outside and balances the malodor-causing substances, and a reduction balancing module that introduces a reducing agent from outside and balances the malodor-causing substances.

Disclosed is a method for the removal of soluble particulate matter from a gas stream, such as urea dust from the off-gas of a finishing section of a urea production plant. The method comprises subjecting the off-gas to at least two quenching stages an aqueous quenching liquid. The quenching liquid used in a first, upstream quench stage, is allowed to have a higher concentration of dissolved particulate matter than the quenching liquid in the second, downstream quench stage. The quenched gas is led through a particle capture zone, typically comprising one or more of a wet scrubber, a Venturi scrubber, and a wet electrostatic precipitator.

A process for preparing sulfuric acid may involve melting elemental sulfur in a melting stage to give molten sulfur. Sulfuric acid is subsequently produced from the molten sulfur. Further, sulfur-containing offgases formed in the melting stage may be subjected to oxidation in a supplementary oxidation stage in which sulfur-containing components of the offgases are oxidized to sulfur dioxide. The process may further involve processing the sulfur dioxide to give at least one reaction product. The melting stage may be operated without emissions by processing all of the offgases from the melting stage. An apparatus may be employed for carrying out such a process.

The present disclosure is directed to methods for treating an organic material, including the steps of transporting the organic material into a first vessel; heating the organic material in the first vessel and applying a negative pressure to the organic material in the first vessel to a boiling point of the organic material, wherein the heat and negative pressure separates a portion of an ammonia from the organic material; removing the portion of the ammonia from the first vessel; transporting the removed portion of the ammonia from the first vessel to an acid solution in a second vessel; and separating a portion of the ammonia from the acid solution.

An absorbent for selective removal of hydrogen sulfide from a fluid stream comprises an aqueous solution of a) a tertiary amine, b) a sterically hindered secondary amine of the general formula (I)

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in which R.sub.1 and R.sub.2 are each independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl, with the proviso that at least one R.sub.4 and/or R.sub.5 radical on the carbon atom bonded directly to the nitrogen atom is C.sub.1-4-alkyl or C.sub.1-4-hydroxyalkyl when R.sub.3 is hydrogen; x and y are integers from 2 to 4 and z is an integer from 1 to 4; where the molar ratio of b) to a) is in the range from 0.05 to 1.0, and c) an acid in an amount, calculated as neutralization equivalent relative to the protonatable nitrogen atoms in a) and b), of 0.05 to 15.0%. One preferred amine of the formula I is 2-(2-tert-butylaminoethoxy)ethanol. The absorbent allows a defined H.sub.2S selectivity to be set at pressures of the kind typical in natural gas processing.

The present invention relates to a method for the catalytic removal of sulfur dioxide from waste gases in two reactors, wherein the first reactor is charged with an activated carbon catalyst. The method comprises: a. provision of a waste gas with a water content of less than 1 g H.sub.2O/Nm.sup.3 and an SO.sub.2 content of at least 5 ppm, b. introduction of the waste gases into a first reactor, c. catalytic conversion of the SO.sub.2 into gaseous SO.sub.3 in the first reactor by the activated carbon catalyst, wherein catalytic conversion on the activated carbon catalyst proceeds at a temperature of below 100 C., d. introduction of the prepurified waste gases from the first reactor into a second reactor, e. conversion of the SO.sub.3 with water into H.sub.2SO.sub.4 in the second reactor.