FR2825452A1 - Air separation device integrated with a gas turbine, uses the hot gases from a blast furnace throat to produce oxygen - Google Patents

Abstract

Compressed air is sent from an air compressor (1) at the inlet or outlet of the combustion chamber (9) to an air separation device (3) and at least one fluid rich in nitrogen is sent from the air separation device to the inlet or outlet of the combustion chamber. A fuel with high calorific power (21) is also sent to the combustion chamber. Air separation device comprises an air compressor (1), a combustion chamber (9) in which at least one chemical reaction occurs producing a very hot gas, an expansion machine (11) for the hot gas and means for sending a fuel of low calorific power (19) to the combustion chamber. All the air for the air separation device comes from the compressor. The means of transferring a fluid rich in nitrogen from the air separation device to the combustion chamber is an expansion machine and all the fluid rich in nitrogen comes from the air separation device. The combustion chamber only receives the two fuels, air from the compressor and/or fluid from the air separation device. The low calorific power fuel comes from a metal production unit such as a blast furnace fed by air from the compressor and/or a fluid enriched in oxygen or nitrogen or argon from the air separation device. An Independent claim is also included for the process for operating this device, by compressing the air, sending a low calorific power fuel to a combustion chamber and sending gas from the combustion chamber to an expansion machine, where the air from the compressor goes to an air separation device and compressed air and/or a fluid enriched in nitrogen from the air separation device is sent to the combustion chamber and/or the expansion machine, and a high calorific power fuel is also sent to the combustion chamber. The two fuels are sent to the combustion chamber simultaneously. The high calorific power fuel is natural gas and the low calorific power fuel is a gas from the throat of a blast furnace, a coking oven or gasification of carbon or petroleum residue, or a biogas. The high calorific power fuel has a calorific value greater than 7000 kcal/Nm<3>, preferably greater than 9000 kcal/Nm<3> and the low calorific power fuel has a calorific value less than 1000 kcal/Nm<3>, preferably between 200 and 750 kcal/Nm<3>. 50-60% of the energy supplied to the combustion chamber is from the high calorific power fuel and the proportion of the two fuels can be varied, decreasing the proportion of high calorific power fuel as the temperature of the air sent to the compressor rises.

Description

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The present invention relates to an air separation apparatus integrated with a gas turbine and to a method of operating this apparatus.

It is known to operate a gas turbine by sending natural gas or top gas from a blast furnace to the combustion chamber of the gas turbine.

If the air from the compressor is sent in part to the combustion chamber in order to obtain a very hot gas which is re-mixed with the other part of the air to adjust its temperature before entering the turbine, the latter temperature being significantly greater than that of the compressor, the power of the turbine is greater than that of the compressor, which leaves useful energy.

If part of the compressed air is separated to form oxygen and nitrogen, the nitrogen being sent to the combustion chamber, it is necessary to send additional air to the device. air separation to balance the flow rates.

In cases where the combustion chamber is supplied with a low calorific value blast furnace gas containing approximately 20% carbon dioxide, 20% carbon monoxide and 60% nitrogen, this gas may burn with air. hot tablet. However, to reach the normal temperature of the turbine, it takes about twenty times more flow than in the case where the fuel is natural gas. The total gas flow rate to be expanded is then 40 to 50% greater than the nominal flow rate, which makes it impossible with a normally sized turbine. In addition, as the gas from the blast furnace is close to atmospheric pressure, it must be compressed to the pressure of the combustion chamber.

NL-C2-1005439 describes the case in which a combustion chamber is supplied with top gas which can be replaced by natural gas.

'Developments in Ironmaking and Opportunities for Power Generation' by G. Wingrove et al, 1999 Gasification Technologies Conference, October 17-20, 1999 describes the use of waste gas from an appliance of various metallurgical production appliances as fuel for a gas turbine.

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It is known to feed the air separation apparatus by a gas turbine either from a dedicated compressor or from the compressor which compresses the air for the combustion chamber or from a dedicated compressor. and the compressor which compresses the air for the combustion chamber (EP-
A-0538118).

The use of a dedicated compressor obviously requires additional expenses. However, if all the air in the air separation device comes from the compressor of the gas turbine and the nitrogen from the air separation device is sent to the combustion chamber or directly to the turbine, this destabilizes the gas turbine because only 80% of the air consists of nitrogen.

It therefore becomes necessary to add gas from a source other than the air separation device as described in the patent application.
S4990.

An object of the invention is to provide an air separation apparatus allowing the production of oxygen by air separation at very low cost.

According to one object of the invention, there is provided an integrated air separation device comprising an air compressor, a combustion chamber, in which at least one chemical reaction is carried out producing at least one very hot gas, a machine for expanding the gas produced by the chemical reaction mixed with other gases and means for sending a fuel of low calorific value to the combustion chamber, characterized in that it comprises means for sending compressed air from the air compressor to the inlet or the outlet of the combustion chamber in which at least one chemical reaction takes place, an air separation device, means for sending air from the air compressor to the air separation apparatus, means for sending at least one nitrogen enriched fluid from the air separation apparatus to the inlet or the outlet of the combustion chamber and means for sending high fuel calorific value of the appliance in which the kills at least one chemical reaction.

According to other optional aspects of the invention: all the air intended for the air separation apparatus comes from the air compressor dedicated to the gas turbine;

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the apparatus may comprise means for sending a nitrogen-enriched gas from the air separation apparatus to the apparatus in which at least one chemical reaction is carried out and / or to the expansion machine.

It can also include means for sending all the nitrogen-enriched gas coming from the air separation device to the combustion chamber in which a chemical reaction takes place.

Preferably the combustion chamber in which a chemical reaction takes place receives only the two fuels of high and low calorific value, air coming from the air compressor and / or fluids coming from the gas separation apparatus. air.

In certain cases the fuel of low calorific value comes from a unit supplied with air coming from the compressor and / or by a fluid enriched in oxygen or nitrogen or argon coming from the air separation device, for example example a metallurgical production unit, such as a blast furnace.

According to another aspect of the invention there is provided an air separation process comprising the steps of: a) compressing air in an air compressor b) sending a fuel of low calorific value to a combustion chamber in which at least one chemical reaction takes place c) sending at least one gas from the combustion chamber to an expansion machine characterized in that it comprises the steps of: d) sending compressed air to a air separation e) sending compressed air to the combustion chamber, and / or sending at least one nitrogen enriched fluid from the air separation device to the combustion chamber and / or to the combustion machine expansion, and send a fuel of high calorific value to the combustion chamber.

According to other optional aspects: - all the air intended for the air separation apparatus comes from the air compressor;

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a nitrogen-enriched gas from the air separation apparatus is sent to the combustion chamber and / or to the expansion machine; all the nitrogen-enriched gas sent to the combustion chamber comes from the air separation apparatus; the combustion chamber receives only the two fuels of high and low calorific value, air from the air compressor and / or fluids from the air separation device; the low calorific fuel comes from a unit supplied with air coming from the compressor and / or by at least one fluid enriched with oxygen or nitrogen or argon from the air separation device; high and low calorific fuels are simultaneously sent to the combustion chamber; the high calorific fuel is natural gas and / or the low calorific fuel is a top gas from a blast furnace, a coke oven gas, a gas obtained by gasification of coal or petroleum residue or a biogas; the high calorific fuel has a calorific value greater than that of the low calorific fuel and possibly greater than 7000kcal / Nm3 and / or the low calorific fuel has a calorific value less than 1000 kcal / Nm3; the high calorific value fuel has a calorific value greater than 9000kcal / Nm3 and / or the low calorific value fuel has a calorific value less than 750kcal / Nm3 and greater than 200 kcal / Nm3; 50 to 60% of the energy supplied by the mixture of fuels to the combustion chamber comes from the high calorific fuel and / or 40 to 50% of the energy supplied by the mixture of fuels to the combustion chamber comes from low calorific fuel; - We vary the proportions of fuels with high and low calorific values sent to the combustion chamber;

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- the proportion of fuel with low calorific value is increased (19) and the proportion of fuel with high calorific value is reduced if the temperature of the air sent to the compressor increases.

With an air separation device coupled to a gas turbine supplied with natural gas, there is a deficit of hot gas at the inlet of the expansion machine.

With an air separation apparatus coupled to a gas turbine supplied with blast furnace gas, there is excess hot gas at the inlet of the expansion machine.

The solution consists in supplying the turbine only partially with blast furnace gas, therefore of low calorific value. The quantity of fuel of low calorific value will be regulated so that there is no topping up of compressed air necessary for the air separation device, nor of surplus gas to be expanded, due to the molecules of inert gases constituting the gas with low calorific value. Thus all the compressed air for the air separation apparatus comes from the compressor of the gas turbine only, without unbalancing the gas turbine.

The invention will be described in more detail with reference to the figure which shows a separation apparatus integrated with a gas turbine.

In the figure, 1000 Nm3 / h of air are compressed to between 8 and 20 bar in the air compressor 1. This compressor 1 is coupled to an expansion machine 11 and integrated with a combustion chamber 9 to form a turbine gas.

600 Nm3 / h of air 5 are sent from the compressor 1 to the air separation apparatus 3 which is a double column or a triple cryogenic distillation column, for example with an oxygen pump; this air constitutes the only air flow which supplies the air separation apparatus. A nitrogen-enriched gas 7 (480 Nm3 / h) is withdrawn from a column of the apparatus 3, compressed in a compressor (not shown) and sent to an expansion machine 11. No flow enriched in nitrogen coming from other than the air separation apparatus is sent to the expansion machine. Part of the compressed air 13 is also sent to the expansion machine and the rest 15 from

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the air from the compressor 3 is sent to a unit in which a chemical reaction for the oxidation of fuels takes place, a combustion chamber 9.

The combustion chamber 9 is fed with a mixture of 15 Nm3 / h of high calorific fuel 21, for example natural gas, and
160 Nm3 / h of low calorific fuel 19, for example compressed top gas from a blast furnace. This blast furnace (not shown) can be supplied with compressed air by the compressor 1 and / or with oxygen-enriched gas 23 coming from the air separation device which produces 120 Nm3 / h of oxygen-enriched gas.

The high calorific fuel could also be a gas produced by gasification of coal or other petroleum residue. It can also be coke oven gas.

The combustion gases from the chamber 9 are expanded with the air and the nitrogen-enriched gas in the expansion machine 11, which allows the production of energy. Steam may also be produced by the low pressure exhaust gases from the turbine (not shown).

As a variant, the nitrogen-enriched gas 7 and / or the air 13 can be sent to the combustion chamber 9.

The low calorific fuel 19 has a calorific value of 600-700 kcallNm3 in this example. Its calorific value value depending on its source can range from 200 to 1200 kcal / Nm3, preferably from 400 to 1000 kcallNm3.

The proportions of the fuels sent to the combustion chamber can be varied in order to maintain or slightly increase the volume of gas expanded in the turbine. For example by sending 11 Nm3 / h of natural gas and 275 Nm3 / h of top gas compressed at between 8 and 20 bar to the combustion chamber, the volume of gas expanded in the expansion machine goes from 1030 Nm3 / h to the previous case at 1130 Nm3 / h.

This also makes it possible to maintain the turbine flow rate in the event of a variation in the ambient air temperature supplying the air compressor of the gas turbine. As the temperature increases, the mass flow sucked by the compressor decreases, causing the power of the gas turbine to decrease.

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By increasing the proportion of fuel with low calorific value, such as top gas, the output of the gas turbine can be maintained or even increased as needed, which makes it possible to maintain energy production in the summer for example, because in a gas turbine approximately 1% of useful energy is lost per degree of air temperature at the additional inlet.

Claims (21)

Claims 1. Integrated air separation apparatus comprising an air compressor (1), a combustion chamber (9), in which at least one chemical reaction takes place producing at least one very hot gas, an expansion machine (11) gas produced by the chemical reaction mixed with other gases and means for sending a fuel of low calorific value (19) to the combustion chamber, characterized in that it comprises means for sending compressed air (15) from the air compressor at the inlet or outlet of the combustion chamber in which at least one chemical reaction takes place, an air separation device (3), means for sending l air (5) from the air compressor to the air separation apparatus, means (7) for sending at least one nitrogen enriched fluid from the air separation apparatus to the inlet or the outlet of the combustion chamber and means for sending a fuel of high calorific value (21) to the combustion chamber. 2. Apparatus according to claim 1 wherein all the air (5) for the air separation apparatus comes from the air compressor (1). 3. Apparatus according to claim 1 or 2 comprising means for sending a nitrogen-enriched gas (7) from the air separation apparatus to the combustion chamber and / or to the expansion machine. 4. Apparatus according to claim 3 wherein all of the nitrogen-enriched gas sent to the combustion chamber originates from the air separation apparatus. 5. Apparatus according to one of the preceding claims wherein the combustion chamber (9) receives only the two fuels of high and low calorific value, air from the air compressor and / or fluids from the. air separation device. 6. Apparatus according to one of the preceding claims wherein the low calorific fuel comes from a unit supplied with air from the compressor and / or a fluid enriched with oxygen or nitrogen or argon from the air separation device. <Desc / Clms Page number 9> 7. Apparatus according to claim 6 wherein the unit from which the low calorific fuel originates is a metallurgical production unit. 8. Apparatus according to claim 7 wherein the metallurgical production apparatus is a blast furnace. 9. A method of air separation comprising the steps of: a) compressing air in an air compressor (1); b) supplying low calorific fuel (19) to a combustion chamber (9); c) sending at least one gas from the combustion chamber to an expansion machine (11) characterized in that it comprises the steps of: d) sending compressed air (5) to an air separation device ; e) sending compressed air to the combustion chamber, and / or sending at least one nitrogen enriched fluid from the air separation device to the combustion chamber and / or to the expansion machine; and f) supplying high calorific fuel (21) to the combustion chamber. 10. The method of claim 9 wherein all the air (5) intended for the air separation apparatus (3) comes from the air compressor. 11. The method of claim 9 or 10 wherein a nitrogen-enriched gas from the air separation apparatus is sent to the combustion chamber (9) and / or to the expansion machine (11). 12. The method of claim 11 wherein all the nitrogen-enriched gas sent to the combustion chamber (9) comes from the air separation apparatus (3). 13. Method according to one of claims 9 to 12 wherein the combustion chamber (9) receives only the two fuels of high and low calorific value, air from the air compressor and / or fluids from the air separation device. 14. Method according to one of claims 9 to 13 wherein the low calorific fuel (19) comes from a unit supplied by <Desc / Clms Page number 10> air from the compressor and / or by a fluid (23) enriched with oxygen or nitrogen or argon from the air separation device (3). 15. Method according to one of claims 9 to 14 wherein the fuels (21,19) of high and low calorific value are sent simultaneously to the combustion chamber. 16. Method according to one of claims 9 to 15 wherein the high calorific fuel (21) is natural gas and / or the low calorific fuel (19) is top gas from a blast furnace, a coke oven gas, a gas obtained by gasification of coal, petroleum residue or a biogas. 17. Method according to one of claims 9 to 16 wherein the high calorific fuel (21) has a higher calorific value than that of the low calorific fuel fuel and optionally greater than 7000kcallNm3 and / or the low calorific fuel. (19) has a calorific value of less than 1000 kcallNm3. 18. The method of claim 17 wherein the high calorific fuel (21) has a calorific value greater than 9000kcal / Nm3 and / or the low calorific fuel (19) has a calorific value less than 750kcal / Nm3 and greater. at 200 kcal / Nm3. 19. The method of claim 9 to 18 wherein 50 to 60% of the energy supplied by the mixture of fuels to the combustion chamber (9) comes from the high calorific value fuels and 40 to 50% of the energy supplied. by the mixture of fuels in the combustion chamber (9) results from the fuel with low calorific value. 20. Method according to one of claims 9 to 19, in which the proportions of the high and low calorific value fuels sent to the combustion chamber (9) are varied. 21. The method of claim 20 wherein the proportion of low calorific fuel is increased (19) and the proportion of high calorific fuel is reduced if the temperature of the air sent to the compressor (1) increases.