An apparatus and method for wet cleaning a gas stream has a housing with a gas inlet and a gas outlet, wherein, in the housing, there is at least a first washing segment that serves to clean the gas stream with a washing liquid and that is arranged in the flow path of the gas stream. Inside the housing of the apparatus, there is at least one fan that regulates air pressure along the flow path of the gas stream. A bypass channel for bypassing the flow path through the at least one washing segment as well as a regulator that is arranged in the bypass and that serves to discharge the gas stream being conveyed via the bypass channel are arranged inside the housing.

An apparatus and method for wet cleaning a gas stream has a housing with a gas inlet and a gas outlet, wherein, in the housing, there is at least a first washing segment that serves to clean the gas stream with a washing liquid and that is arranged in the flow path of the gas stream. Inside the housing of the apparatus, there is at least one fan that regulates air pressure along the flow path of the gas stream. A bypass channel for bypassing the flow path through the at least one washing segment as well as a regulator that is arranged in the bypass and that serves to discharge the gas stream being conveyed via the bypass channel are arranged inside the housing.

An exhaust gas purification device includes an exhaust gas discharge unit having an exhaust gas passage, and a plurality of smoke purifying units. Each smoke purifying unit includes a smoke purifying module disposed outside of the exhaust gas discharge unit and including an elongated smoke purifying holder defining a channel, and at least one water spray pipe for spraying water into the channel. An exhaust gas capture module includes a first exhaust gas capture pipe communicating the exhaust gas passage with the channel and having a first smoke trap extending into the exhaust gas passage.

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 25 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).

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 25 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).

A process for purifying exhaust air from a granulation plant for producing a urea-containing granulate may involve causing a gas stream containing a urea-containing dust and ammonia to contact a sulfuric acid solution or a nitric acid solution in a scrubbing process. The scrubbing process may comprise scrubbing the gas stream with a first weakly acidic scrubbing solution in a first scrubbing stage and then scrubbing the gas stream exiting the first scrubbing stage with a second scrubbing solution having a lower pH than the first weakly acidic scrubbing solution in a second scrubbing stage. The acidic scrubbing solution generated in the second scrubbing stage may be recycled into the first scrubbing stage via a conduit and used therein as the first weakly acidic scrubbing solution. A pre-scrubbing stage where dust is scrubbed out of the gas stream may additionally be arranged upstream of the first scrubbing stage.

A process for purifying exhaust air from a granulation plant for producing a urea-containing granulate may involve causing a gas stream containing a urea-containing dust and ammonia to contact a sulfuric acid solution or a nitric acid solution in a scrubbing process. The scrubbing process may comprise scrubbing the gas stream with a first weakly acidic scrubbing solution in a first scrubbing stage and then scrubbing the gas stream exiting the first scrubbing stage with a second scrubbing solution having a lower pH than the first weakly acidic scrubbing solution in a second scrubbing stage. The acidic scrubbing solution generated in the second scrubbing stage may be recycled into the first scrubbing stage via a conduit and used therein as the first weakly acidic scrubbing solution. A pre-scrubbing stage where dust is scrubbed out of the gas stream may additionally be arranged upstream of the first scrubbing stage.

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 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 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.