Carbon capture method and apparatus for a ferrous metal production unit

Abstract

Title: Carbon capture process and apparatus from a ferrous metal production unit In a carbon capture process from a ferrous metal production unit, the waste gas (GG) from a ferrous metal production unit (HF) is compressed and separated by adsorption (PSA) forming a CO2-enriched gas (TG) and a CO2-depleted gas (PG), part of the CO2-depleted gas is returned to the production unit, part of the CO2-depleted gas is compressed to between 20 and 40 bar and is sent to a combustion chamber of a gas turbine (GT), at least part of the CO2-enriched gas is sent to a CO2 separation unit (CC) by partial condensation and / or distillation and / or solidification producing a CO2-rich fluid or solid and a second CO2-depleted gas (CO2lg) is sent from the CO2 separation unit to the combustion chamber. Figure from the summary: Fig. 2

Description

Title of the invention: Method and apparatus for capturing carbon from a ferrous metal production unit

[0001] The present invention relates to a method and apparatus for capturing carbon from a ferrous metal production unit.

[0002] The blast furnace is the main processing unit of a steelworks where fossil fuels (coke, coal, natural gas, oil, etc.) are consumed. Its main objective is to generate reducing gas which will allow the reduction and melting of iron ore into hot metal (or "cast iron" into pig iron). This hot metal is then transformed by converters to become steel.

[0003] Blast furnace gas is generally composed of 20-25 mol% CO, 0-10 mol% H2, 20-30 mol% CO2, the remainder being N2 and argon. Other ferrous metal production units produce gases of similar composition.

[0004] In order to reduce the carbon footprint of the blast furnace, a complete recycling process has been studied in depth (oxygen blast furnace type or in English "Top Gas Recycling Blast Fumace"), entirely replacing the injection of air with oxygen and recycling the blast furnace gas after removal of CO2.

[0005] In conventional steel mills, blast furnace gas is used as:

[0006] - fuel in the stove (to heat the air sent to the blast furnace to a temperature >1000°C)

[0007] - Fuel in reheating furnaces (possibly with air enriched in O2)

[0008] - Fuel in the power plant

[0009] Generally speaking, integrated steel mills are close to self-sufficiency in terms of energy balance. One of the obstacles to better efficiency of the steel mill's electricity production is the low calorific value (GCV) of the gas (typically 4 to 5 MJ / Nm3), which prevents its efficient use in a gas turbine.

[0010] In order to capture part of the CO2 it contains, it is known to separate the blast furnace gas by a physicochemical absorption process using an amine solution, or a pressure swing adsorption process called PSA (Pressure Swing Adsorption), or an adsorption process with vacuum regeneration called VPSA (Vacuum Pressure Swing Adsorption), these processes being able to be associated or not with an additional cryogenic step intended to produce pure CO2 ready to be stored or to be used in specific applications such as the food industry or the enhanced recovery of hydrocarbons in deposits at the end of their useful life. operating.

[0011] It is known from FR2889971 to separate a blast furnace top gas by pressure swing adsorption, a depressurization gas being sent to a gas turbine.

[0012] According to an object of the invention, there is provided a method for capturing carbon from a ferrous metal production unit in which a. The waste gas from a ferrous metal production unit is compressed and separated by adsorption, forming a CO2-enriched gas and a CO2-depleted gas. b. Part of the CO2-depleted gas is returned to the production unit c. At least some of the CO2-depleted gas is compressed to between 20 and 40 bars and is sent to a combustion chamber of a gas turbine d. A portion of the CO2-enriched gas is sent to a CO2 separation unit by partial condensation and / or distillation and / or solidification producing a CO2-rich fluid or solid and e. A second CO2-depleted gas sent from the CO2 separation unit to the combustion chamber.

[0013] Thus a gas with a calorific value and a gas with a lower calorific value are sent to the combustion chamber.

[0014] According to other optional aspects - The part of the gas returned to the ferrous metal production unit is reheated to a temperature between 300°C and 1300°C, preferably between 300°C and 400°C.

[0015] -Natural gas and / or COG and / or H2 is mixed with the portion of the gas returned to the ferrous metal production unit upstream of the unit and optionally the mixture formed is heated as above

[0016] -at least a portion of the CO2-enriched gas is used as fuel to heat the portion of the gas sent to the unit

[0017] -at least a portion of the CO2-enriched gas is burned in air or oxygen-enriched air

[0018] -the gas turbine is connected to a steam generator

[0019] -the part of the CO2-depleted gas sent to the combustion chamber is not cooled after compression before being sent to the combustion chamber

[0020] - the compression of the part of the gas depleted in CO2 sent to the combustion chamber is adiabatic

[0021] -a portion of the CO2-enriched gas is injected at the outlet of the gas turbine and burned with the oxygen in the gas coming from the gas turbine

[0022] -the separation of step a) is carried out by pressure rocking adsorption

[0023] The invention will be described in more detail with reference to the figures:

[0024] [Fig. 1] represents a comparative method

[0025] [Fig.2] represents a method according to the invention

[0026] [Fig. 1] shows a comparative process for carbon capture from a ferrous metal production unit HF, which may be a blast furnace. The waste gas (top gas) GG from a ferrous metal production unit is compressed and separated by pressure swing adsorption PSA forming a CO2-enriched gas TG containing more than 50 mol% CO2 and a CO2-depleted gas PG containing less than 3 mol% CO2. - A portion of the CO2-depleted gas is compressed to between 20 and 40 bars and is sent to a combustion chamber of a gas turbine. The remainder of this CO2-depleted gas PG is returned to the HF production unit after heating to a temperature between 300°C and 1300°C, preferably between 300°C and 400°C. Natural gas and / or COG and / or H2 is mixed with the portion of the gas returned to the ferrous metal production unit upstream of the unit and optionally the mixture formed is heated as above.

[0027] CO2-enriched gas is injected at the outlet of the gas turbine and burned with oxygen in the gas from the gas turbine.

[0028] [Fig.2] represents a process which is a variant of [Fig.l]. Here the gas enriched in CO2 TAG is separated by partial condensation and / or distillation and / or solidification in a CC unit to form a CO2-rich fluid or solid. A second CO2-depleted gas CO21g is mixed upstream of the adsorption with the GG gas and / or sent to the combustion chamber at a pressure above 15 bars.

[0029] A portion of the CO2 TG enriched gas may be used as fuel to heat the portion of the gas sent to the HF unit, by burning it in air or oxygen-enriched air.

[0030] The gas turbine GT is connected to a water steam generator HRSG.

[0031] The portion of the CO2-depleted gas sent to the combustion chamber is not cooled after compression before being sent to the combustion chamber and the compression of the part of the CO2-depleted gas sent to the combustion chamber is preferably adiabatic.

[0032] A portion of the CO2-enriched gas TG is injected at the outlet of the gas turbine and burned with oxygen in the gas from the gas turbine GT.

Claims

Claims

1. A method of capturing carbon from a ferrous metal production unit wherein a. The waste gas (GG) from a ferrous metal (HF) production unit is compressed and separated by adsorption (PSA) forming a CO2-enriched gas (TG) and a CO2-depleted gas (PG) b. Part of the CO2-depleted gas is returned to the production unit c. A portion of the CO2-depleted gas is compressed to between 20 and 40 bars and sent to a combustion chamber of a gas turbine (GT) d. At least a portion of the CO2-enriched gas is sent to a CO2 separation unit (CC) by partial condensation and / or distillation and / or solidification producing a CO2-rich fluid or solid and e. A second CO2-depleted gas (CO21g) is sent from the CO2 separation unit to the combustion chamber.

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