摘要:
Direct reduction process and plant for producing DRI comprising a reduction reactor and at least one reducing gas heater typically comprising a convective heating section and a radiant heating section for raising the reducing gas temperature to a level adequate for iron oxides reduction to metallic iron, typically above 850° C., wherein the reducing gas fed to the reduction reactor comprises a stream of reducing gas recycled from the reduction reactor and a make-up stream of coke oven gas containing carbon compounds which may form carbon deposits in the heating path of said heater, namely BTX and other complex carbon compounds. The heater is provided with means for feeding oxidizing agents, for example steam, steam and air and/or oxygen at predetermined heating tubes successively for eliminating the carbon deposits which may form inside the heating tubes of said heater without interrupting the operation of the plant. The make-up stream of cold COG can be combined with the recycled gas at a point in the gas heating path of the heater where the tubes have a skin wall temperature of at least 700° C., or when the mixture of recycled gas and COG is at a temperature above 700° C. for minimizing clogging or fouling of heating equipment.
摘要:
A method and apparatus for producing direct reduced iron (DRI), also known as sponge iron, by means of direct contact of iron oxides with a stream of recycled and regenerated hot reducing gases containing hydrogen and carbon monoxide. The invention provides a way for decreasing the uncontained emission of CO2 to the atmosphere produced by combustion of carbon-bearing fuels in the reducing gas heater by substituting, at least partially, a gas stream mainly composed of hydrogen in lieu of the usual carbon-bearing fuels. The hydrogen fuel stream, depleted of CO2 by means of a physical gas separation unit (which can be a PSA/VPSA type adsorption unit, a gas separation membrane unit or combination of PSA/VPSA unit and a gas separation membrane unit) is derived from at least a portion of a stream of regenerated reducing gases being recycled to the reduction reactor. The derived hydrogen fuel stream is combusted in the reducing gas heater and/or other thermal equipment in the reduction plant, thus decreasing the CO2 emissions directly to the atmosphere.
摘要:
A direct reduction process for producing direct reduced iron (DRI) in a reduction reactor having a reduction zone for reducing iron-oxides-containing particles, such as iron ore pellets, to DRI by reaction of said iron oxides with a high temperature reducing gas, and a cooling zone for lowering the temperature of the DRI produced in said reduction zone, wherein a stream of cooling gas, usually natural gas, is circulated through said cooling zone, a portion of said cooling gas is withdrawn from the cooling zone, cooled and cleaned in a gas cooler and a portion of the cooled gas is recycled to said reduction zone by means of an ejector utilizing the high-pressure natural gas make-up feed as the ejector's motive fluid. Using an ejector for recycling the cooling gas instead of using a mechanical compressor provides significant savings in electricity and in capital, operational and maintenance costs. A direct reduction plant having a DRI cooling zone which uses at least one ejector in recycling at least a portion of cooling gas to the cooling zone.
摘要:
A process for reducing iron ore particles in a moving bed reduction reactor comprising an upper reduction zone and a lower discharge zone, wherein coke oven gas, preferably forming all the make-up for the reducing gas circulating through and reacting in the reduction zone, is first fed to the discharge (and, optionally, cooling) zone and thereafter, conditioned by the DRI in the lower zone, is withdrawn from the reactor and transferred externally into the recycle reducing gas for injection into the reduction zone; with the heavy hydrocarbons and other components of coke oven gas which cause fouling, corrosion, or deposits in the direct reduction plant being removed from coke oven gas by catalytic and/or adsorptive action of the DRI in the lower zone; preferably the gas flow rate of the coke oven gas and the externally transferred gas differs between about 100 and 200 NCM per ton of DRI produced.
摘要:
A direct reduction process for producing direct reduced iron (DRI) in a reduction reactor having a reduction zone for reducing iron-oxides-containing particles, such as iron ore pellets, to DRI by reaction of said iron oxides with a high temperature reducing gas, and a cooling zone for lowering the temperature of the DRI produced in said reduction zone, wherein a stream of cooling gas, usually natural gas, is circulated through said cooling zone, a portion of said cooling gas is withdrawn from the cooling zone, cooled and cleaned in a gas cooler and a portion of the cooled gas is recycled to said reduction zone by means of an ejector utilizing the high-pressure natural gas make-up feed as the ejector's motive fluid. Using an ejector for recycling the cooling gas instead of using a mechanical compressor provides significant savings in electricity and in capital, operational and maintenance costs. A direct reduction plant having a DRI cooling zone which uses at least one ejector in recycling at least a portion of cooling gas to the cooling zone.