Recovery of sulfur trioxide heat of absorption

摘要

A contact process for manufacture of sulfuric acid in which the vapor phase heat of formation of sulfuric acid in the sulfur trioxide conversion gas and the heat of absorption of SO3 in sulfuric acid is recovered by transfer of heat from the absorption acid to high pressure boiler feed water that is fed to a waste heat boiler where steam is generated at a pressure of at least 40 bar by transfer of heat from sulfur dioxide combustion gas.

主权项

1. A process for the manufacture of sulfuric acid comprising:
contacting a source gas comprising sulfur trioxide in a primary heat recovery absorption zone with a sulfur trioxide absorption acid stream comprising liquid sulfuric acid, thereby transferring sulfur trioxide from the source gas to the absorption acid stream and heating said absorption acid stream by heat of absorption; transferring heat from said absorption acid stream to a boiler feed water stream in an array of heat exchangers that are in series with respect to the flow of both the boiler feed water stream and the absorption acid stream, and with respect to which array said absorption acid stream and said boiler feed water stream flow countercurrently; allowing said boiler feed water stream to flash in a reduced pressure zone in the boiler feed water flow path between two successive heat exchangers in said series, thereby generating steam and cooling the boiler feed water stream in said reduced pressure zone; separating steam generated in said reduced pressure zone from said cooled boiler feed water stream; recovering in useful form the energy from steam generated in said reduced pressure zone; pressurizing said cooled boiler feed water stream; transferring said pressurized boiler feed water stream to another heat exchanger in said series that is downstream of said reduced pressure zone with respect to the flow of boiler feed water; heating said pressurized boiler feed water stream in said another heat exchanger by transfer of heat from said absorption acid; generating steam from the pressurized liquid water stream at a pressure of at least 40 bar in a boiler that is outside of said array and downstream of said another heat exchanger with respect to the flow of boiler feed water; and circulating said absorption acid stream from said series of heat exchangers back to said heat recovery absorption zone.