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.

The present invention provides a dust removal system for a chimney of a mixer. The system includes a dust removal water tank and a first pipeline. One end of the first pipeline is communicated with an outlet of the chimney at a tail of the mixer, and the other end is inserted into the dust removal water tank. A water inlet and a water outlet are provided in the dust removal water tank. An exhaust port for discharging filtered gas is provided in an upper part of the dust removal water tank. The system does not need additional power, and is energy-saving and environmentally friendly. Water vapor discharged facilitates the sedimentation of dust particles in the mixer, thereby reducing loss of raw material mixture, making sintering quality more stable and solving a problem that gas discharged in prior arts contains more powder and pollutes the environment.

Apparatus and methods for denitrification and desulfurization of and dust removal from an FCC tail gas by an ammonia-based process. The apparatus may include a first-stage waste heat recovery system, a denitrification system, a dust removal and desulfurization system, a tail gas exhaust system, and an ammonium sulfate post-processing system. The dust removal and desulfurization system may include a dedusting tower and an absorption tower disposed separately. The top and the bottom of the absorption tower may be connected respectively to the tail gas exhaust system and the ammonium sulfate post-processing system. The absorption tower may include sequentially, from bottom to top, an oxidation section, an absorption section, and a fine particulate control section. The methods may be implemented with the apparatus.

There is provided an active coke regeneration mixed vapor treatment method. The method comprises the following process steps of: A) performing a first water condensation on a mixed vapor produced during an active coke regeneration process by spray water in a first condensation zone; B) performing a second water condensation on the mixed vapor that is after the first water condensation by spray water in a second condensation zone, to further condensate and purify the mixed vapor; C) eliminating moisture in a gas through mist elimination from the gas fraction in the mixed vapor that is after the second water condensation, and discharging the remaining gas from the upper of the second condensation zone; and, D) discharging active coke micro powder in the mixed vapor that is after the second water condensation, with condensation water. In the present invention, an apparatus for implementing the abovementioned method is also provided.

There is provided an active coke regeneration mixed vapor treatment method. The method comprises the following process steps of: A) performing a first water condensation on a mixed vapor produced during an active coke regeneration process by spray water in a first condensation zone; B) performing a second water condensation on the mixed vapor that is after the first water condensation by spray water in a second condensation zone, to further condensate and purify the mixed vapor; C) eliminating moisture in a gas through mist elimination from the gas fraction in the mixed vapor that is after the second water condensation, and discharging the remaining gas from the upper of the second condensation zone; and, D) discharging active coke micro powder in the mixed vapor that is after the second water condensation, with condensation water. In the present invention, an apparatus for implementing the abovementioned method is also provided.

The invention concerns a method for unblocking pores in a metal zeolite based selective catalytic reduction (SCR) catalyst. The method includes filling, at least partially, the SCR catalyst with a liquid, the liquid being preferably distilled water. The method includes letting said liquid inside the SCR catalyst enough time to allow said liquid to dissolve, at least partially, the obstructions and to penetrate into the pores. The method includes heating the SCR catalyst at a temperature above the ebullition temperature of the liquid so as to vaporize the part of the liquid remained into the pores, and generate steam flows through the obstructions, the steam flows removing the obstructions and unblocking the pores, wherein no hydrocarbons are injected during the step of heating.

The invention concerns a method for unblocking pores in a metal zeolite based selective catalytic reduction (SCR) catalyst. The method includes filling, at least partially, the SCR catalyst with a liquid, the liquid being preferably distilled water. The method includes letting said liquid inside the SCR catalyst enough time to allow said liquid to dissolve, at least partially, the obstructions and to penetrate into the pores. The method includes heating the SCR catalyst at a temperature above the ebullition temperature of the liquid so as to vaporize the part of the liquid remained into the pores, and generate steam flows through the obstructions, the steam flows removing the obstructions and unblocking the pores, wherein no hydrocarbons are injected during the step of heating.

A high-efficiency gradient hierarchy complex desulfurizing tower includes a tower body. The tower body tower includes an oxidization and crystallization stage, a coarse desulfurization and dedusting stage, a fine desulfurization and dedusting stage, and a horizontal demisting stage from the bottom up. The oxidization and crystallization stage tower includes a pond and a separation mechanism provided in the pond and separating the pond into an upper area and a lower area. The coarse desulfurization and dedusting stage tower includes a gas distributing board and a multi-layer spray layer that are placed above a gas import, the spray layer being in connection with the pond. The fine desulfurization and dedusting stage tower includes a tube demister, a flushing layer, a film liquid holdup layer, a liquid holdup layer recycling can, the pH of slurry in the liquid holdup layer recycling can being higher than the pH of slurry in the pond.

A high-efficiency gradient hierarchy complex desulfurizing tower includes a tower body. The tower body tower includes an oxidization and crystallization stage, a coarse desulfurization and dedusting stage, a fine desulfurization and dedusting stage, and a horizontal demisting stage from the bottom up. The oxidization and crystallization stage tower includes a pond and a separation mechanism provided in the pond and separating the pond into an upper area and a lower area. The coarse desulfurization and dedusting stage tower includes a gas distributing board and a multi-layer spray layer that are placed above a gas import, the spray layer being in connection with the pond. The fine desulfurization and dedusting stage tower includes a tube demister, a flushing layer, a film liquid holdup layer, a liquid holdup layer recycling can, the pH of slurry in the liquid holdup layer recycling can being higher than the pH of slurry in the pond.

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.