A system for producing aqueous sulphuric acid is provided, the system including a first heat exchanger configured to cool aqueous sulphuric for producing cooled aqueous sulphuric acid; a pre-cooling unit comprising an inlet or inlets for receiving the gas containing sulphur trioxide and the cooled aqueous sulphuric acid, an outlet for letting out aqueous sulphuric acid and the gas containing sulphur trioxide, and a first nozzle for spraying the cooled aqueous sulphuric acid onto the gas containing sulphur trioxide. The system further includes a condensation tower comprising a first inlet for receiving the cooled gas containing sulphur trioxide and aqueous sulphuric acid from the pre-cooling unit and means for circulating the aqueous sulphuric acid within the condensation tower by spraying. An associated method and pre-cooling unit suitable for cooling gas comprising sulphur trioxide from at least 400 C. to at most 150 C. are also provided.

This invention relates to processes for selective removal of contaminants from effluent gases. A sulfur dioxide absorption/desorption process for selective removal and recovery of sulfur dioxide from effluent gases utilizes a buffered aqueous absorption solution comprising weak inorganic or organic acids or salts thereof, to selectively absorb sulfur dioxide from the effluent gas. Absorbed sulfur dioxide is subsequently stripped to regenerate the absorption solution and produce a sulfur dioxide-enriched gas. A process for simultaneous removal of sulfur dioxide and nitrogen oxides (NO.sub.x) from effluent gases and recovery of sulfur dioxide utilizes a buffered aqueous absorption solution including a metal chelate to absorb sulfur dioxide and NO.sub.x from the gas and subsequently reducing absorbed NO.sub.x to form nitrogen. A process to control sulfate salt contaminant concentration in the absorption solution involves partial crystallization and removal of sulfate salt crystals.

This invention relates to processes for selective removal of contaminants from effluent gases. A sulfur dioxide absorption/desorption process for selective removal and recovery of sulfur dioxide from effluent gases utilizes a buffered aqueous absorption solution comprising weak inorganic or organic acids or salts thereof, to selectively absorb sulfur dioxide from the effluent gas. Absorbed sulfur dioxide is subsequently stripped to regenerate the absorption solution and produce a sulfur dioxide-enriched gas. A process for simultaneous removal of sulfur dioxide and nitrogen oxides (NO.sub.x) from effluent gases and recovery of sulfur dioxide utilizes a buffered aqueous absorption solution including a metal chelate to absorb sulfur dioxide and NO.sub.x from the gas and subsequently reducing absorbed NO.sub.x to form nitrogen. A process to control sulfate salt contaminant concentration in the absorption solution involves partial crystallization and removal of sulfate salt crystals.

A system (100) for producing aqueous sulphuric acid. The system (100) comprises a first heat exchanger (410) configured to cool water and/or aqueous sulphuric for producing cooled water and/or cooled aqueous sulphuric acid; a pre-cooling unit (200) configured to pre-cool some gas containing sulphur trioxide, the pre-cooling unit (200) comprising an inlet or inlets (212, 214) for receiving [i] the gas containing sulphur trioxide and [ii] the cooled water and/or the cooled aqueous sulphuric acid, an outlet (216) for letting out aqueous sulphuric acid and the gas containing sulphur trioxide, and a first nozzle (220) for spraying the cooled water and/or the cooled aqueous sulphuric acid onto the gas containing sulphur trioxide to cool the gas containing sulphur trioxide. The system further comprises a condensation tower (300) comprising a first inlet (302) for receiving the cooled gas containing sulphur trioxide and aqueous sulphuric acid from the pre-cooling unit (200) and means (320) for circulating the aqueous sulphuric acid within the

The above mentioned invention describes a process for cooling a gas mixture of SO.sub.2 and/or SO.sub.3 and water, wherein the gas mixture is cooled by means of a first heat exchanger carrying a coolant. The temperature of the coolant lies above the dew point of the gas or gas mixture.

The above mentioned invention describes a process for cooling a gas mixture of SO.sub.2 and/or SO.sub.3 and water, wherein the gas mixture is cooled by means of a first heat exchanger carrying a coolant. The temperature of the coolant lies above the dew point of the gas or gas mixture.

This invention relates to processes for selective removal of contaminants from effluent gases. A sulfur dioxide absorption/desorption process for selective removal and recovery of sulfur dioxide from effluent gases utilizes a buffered aqueous absorption solution comprising weak inorganic or organic acids or salts thereof, to selectively absorb sulfur dioxide from the effluent gas. Absorbed sulfur dioxide is subsequently stripped to regenerate the absorption solution and produce a sulfur dioxide-enriched gas. A process for simultaneous removal of sulfur dioxide and nitrogen oxides (NO.sub.x) from effluent gases and recovery of sulfur dioxide utilizes a buffered aqueous absorption solution including a metal chelate to absorb sulfur dioxide and NO.sub.x from the gas and subsequently reducing absorbed NO.sub.x to form nitrogen. A process to control sulfate salt contaminant concentration in the absorption solution involves partial crystallization and removal of sulfate salt crystals.

This invention relates to processes for selective removal of contaminants from effluent gases. A sulfur dioxide absorption/desorption process for selective removal and recovery of sulfur dioxide from effluent gases utilizes a buffered aqueous absorption solution comprising weak inorganic or organic acids or salts thereof, to selectively absorb sulfur dioxide from the effluent gas. Absorbed sulfur dioxide is subsequently stripped to regenerate the absorption solution and produce a sulfur dioxide-enriched gas. A process for simultaneous removal of sulfur dioxide and nitrogen oxides (NO.sub.x) from effluent gases and recovery of sulfur dioxide utilizes a buffered aqueous absorption solution including a metal chelate to absorb sulfur dioxide and NO.sub.x from the gas and subsequently reducing absorbed NO.sub.x to form nitrogen. A process to control sulfate salt contaminant concentration in the absorption solution involves partial crystallization and removal of sulfate salt crystals.

The above mentioned invention describes a process for cooling a gas mixture of SO.sub.2 and/or SO.sub.3 and water, wherein the gas mixture is cooled by means of a first heat exchanger carrying a coolant. The temperature of the coolant lies above the dew point of the gas or gas mixture.

The above mentioned invention describes a process for cooling a gas mixture of SO.sub.2 and/or SO.sub.3 and water, wherein the gas mixture is cooled by means of a first heat exchanger carrying a coolant. The temperature of the coolant lies above the dew point of the gas or gas mixture.