JPH10184388A - Method and device for obtaining work from high-pressure gas flow abundant in nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the process efficiency in the case where a blast furnace gas of a low calorific value or the like is utilized by indirectly heating the gas flow abundant in nitrogen obtained by a low-temperature air separator by using the heat obtained by the combustion of a fuel so as to produce a high-pressure low, and by expanding the high-pressure flow to perform external work. SOLUTION: The nitrogen flow coming from an inlet 10 is introduced into a heat exchanger 14 through a pipeline 12, and then it is introduced into a second heat exchanger 18 with which a fuel burner 20 is combined so as to be successively heated. The heated nitrogen flow is sent to the inlet of an axial flow turbine 24 through a pipeline 22 from the heat exchanger 18, herein the nitrogen flow is expanded to perform external work. The nitrogen flow after completion of work passes through the opposite side of the heat exchanger 14 through a pipeline 26, and is discharged through an outlet 28. On the other hand, both the air to be used for combustion that is introduced through an inlet 30, and the fuel gas from an inlet 32 after heated through a third heat exchanger 36 are supplied to the burner 20 and burnt, and the combustion gas is discharged from an outlet 46 through the heat exchangers 18 and 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
enic) a process for obtaining work from a nitrogen-rich high-pressure gas stream from an air separation unit or a factory.

[0002]

2. Description of the Related Art In a low-temperature air separation plant, a nitrogen component obtained by separating air passes through a distillation column from a pressure of a distillation column to a pipe or a heat exchanger for high-temperature discharge conditions. Can be designed to produce pressure drop near atmospheric pressure. Alternatively, the nitrogen stream may be intentionally back-pressured to allow all of the product from the air separation unit to be produced at a substantially higher pressure than the atmosphere. High pressure plants are used for applications where the majority of the air to be separated is required as a high pressure product. Such high-pressure factories
Due to the smaller heat exchangers, towers and pretreatment adsorbers, they have lower capital costs and also lower construction costs than factories operating at minimum pressure.

[0003] In the past, proposals have been made to combine such cryogenic air separation plants with other industrial processes to gain work from the pressurized nitrogen produced, and also to produce low pressure nitrogen. Similar proposals have been made for operating air separation devices.

US Pat. No. 2,520,862 states that
It is described to take nitrogen from the high pressure column of a normal minimum pressure air separation unit and mix it with some oxygen. The fuel is then burned with this high pressure gas mixture and the combustion products at about 500 ° C. are expanded to atmospheric pressure with a hot gas expander. Optionally, an economizer heat exchanger is used to recover heat from the expander exhaust and preheat the high pressure nitrogen / oxygen mixture prior to combustion.

[0005] US Pat. No. 3,731,495 describes:
It is described that nitrogen is removed from the high pressure air separation unit, mixed with the combustion products of the pressurized air / fuel stream, and then the hot gas mixture is expanded to atmospheric pressure. The shaft power created is used to compress the air to create pressurized air that is split for use in the air separation unit and the combustion process.

US Pat. No. 5,040,370 discloses that
It is described that the nitrogen extracted from an air separation plant at a pressure of 2 to 7 bara (200 to 700 kPa) is subjected to indirect heat exchange using a phase-change high temperature fluid stream from the process as a heat source. The process of producing this hot fluid stream at temperatures up to 600 ° C. uses oxygen from an air separation unit, where the hot nitrogen is expanded in a turbine to perform external work.

[0007] US Pat. No. 5,078,837 describes:
The heated nitrogen stream is at least 5 bara (500 kP
An essentially similar process is disclosed, except at a) pressure and at a temperature of at least 700 ° C.

[0008] US Pat. No. 5,268,019 discloses:
It is disclosed that the pressurized fuel gas is burned, and the combustion products are expanded by a turbine to generate work. A portion of the nitrogen from the air separation unit is pressurized and supplied to the combustion products before expansion by the turbine. Another nitrogen is heated to a temperature of 400 ° C. by indirect heat exchange with the expanded combustion products and then expanded in another turbine to produce further work. Oxygen from an air separation unit that produces nitrogen is used in processes to produce gaseous fuels, for example, in blast furnace operation.

[0009] GB-A-2266343 discloses the indirect heating of a stream of nitrogen with a low-grade fuel gas produced in a blast furnace. However, in that specification, the fuel gas is compressed before being supplied to the burner.

[0010] GB-A-2 210 455 discloses that high grade fuel gas is burned and expanded to extract work, typically helium, argon,
A working fluid, which is hydrogen or a mixture of hydrogen and methane,
Indirect heating in a closed system is described. The products of combustion are 1-100 bar (100-10,0
00 kPa). The concept of heating the compressed nitrogen from the air separation unit is not disclosed.

[0011] UK Patent Application Publication No. 156,096 describes the regasification of natural gas. Heat is supplied by heating nitrogen as the working fluid, but the nitrogen recirculates in a closed system and is not a compressed gas stream from the air separation unit. The type of heater and fuel used is not clear.

In WO 95/05529, helium is used as a working fluid to be heated indirectly.
Inert gases such as argon or neon are used in closed systems.

EP-A-0 208 162
The specification teaches burning a fuel in a gas turbine and using the exhaust to heat a compressed gas, preferably air.

US Pat. No. 4,228,659 describes:
It is described that the working fluid in a closed system is indirectly heated by a combustor. Using nitrogen from the air separation unit,
The concept of discharging it after use is not disclosed.

[0015] In the context of using nitrogen from an air separation unit, these disclosures fall into two categories with respect to heat sources for nitrogen. In one category, the fuel is combusted with high pressure air to which nitrogen has been added to form a gas mixture, which is then expanded in a turbine and optionally also indirectly heating the nitrogen. The inventors of the present invention have found that this creates a number of disadvantages. The quality of the gas in the expander is less desirable due to the presence of fuel combustion products. The capital cost of the factory is
Increased by the need to compress the fuel gas and the air that burns it. The use of gas turbines for combustion requires significant capital costs. Also, the restriction on the purity of the nitrogen supplied for mixing with the combustion products would eliminate the possibility of safely adding significant amounts of oxygen mixed with the nitrogen. Flammable gases with low calorific values are often only available at near atmospheric pressure from oxygen consuming processes produced in air separation units. Therefore, such fuel gases need to be significantly compressed before use in this type of process.

The other category of disclosure requires that the nitrogen be heated by indirect heat transfer with hot gas produced in another process. Here, only the sensible heat content of the heating gas stream is transmitted, and no chemical energy from other streams of the combustion process is utilized. This means that the flow rate and temperature of the hot stream must be sufficient to supply all the heat required. In practice, this requires very large surface area indirect heat exchangers and high capital costs.

[0017]

According to a first aspect of the present invention, there is provided a method for obtaining work from a nitrogen-rich, high-pressure gas stream obtained from a cryogenic air separation device, comprising: To produce a high-pressure gas stream rich in nitrogen,
Fuel gas up to 5 bara (500 kP
a) supplying a liquid or solid fuel at a pressure up to a), burning said fuel, and indirectly heating said nitrogen-rich stream using the heat obtained from the combustion of said fuel to produce nitrogen Providing a heated high-pressure stream rich in nitrogen, expanding the heated high-pressure stream rich in nitrogen to perform external work, and discharging the nitrogen-rich stream. .

It should be appreciated that "nitrogen-rich streams" may contain gases other than nitrogen, as described further below.

Preferably, the fuel is fuel gas and up to 3 bara (300 kPa) to the burner, more preferably 1.1 to 2.5 bara (110 to 250 kP).
a), even more preferably 1.1 to 2 bara (110
To 200 kPa), for example, 1.1 to 1.2 bara (1
10 to 120 kPa).

Preferably, the fuel gas is obtained from a process for producing the fuel gas and supplied to the burner without pressurization with a compressor, but to the burner used for combustion of the fuel gas. It may be desirable to use a blower to facilitate satisfactory flushing.

Suitably, the fuel gas is supplied at least mainly from a source of fuel gas having a heat content of from 2.5 to 16 MJ / Nm ³ , preferably from 2.5 to 12 MJ / Nm ³ , ie mainly low It is composed of calorific value fuel gas. Such low heat content fuel gases are difficult to burn in burners. To support the combustion of low heat content fuel gases, other higher calorific value gases may be used, for example, in smaller amounts, up to 10% by volume. Suitably, this additional high heat content gas is provided in an amount up to double the heat content of the low heat content gas. For example, the heat content in the case the heat content of the low calorific value of the fuel gas is 2.5~4MJ / Nm ^3, the resulting mixture the gas heat content is mixed with substantially higher sufficient gas Can be increased to ⁴ to 6 MJ / Nm ³ .

The high heat content gas can be used in various ways to promote low heat content combustion. It may simply be mixed with a low heat content gas to make a higher heat content mixture. It may be fed to the burner's own pilot jet, or it may be burned to create a heated gas containing residual oxygen that can be fed to the burner to promote combustion.

Suitable sources of low heat content fuel gas used primarily in the present invention are those having a heat content typically between 2.5 and 6M
Waste gas from a blast furnace at J / Nm ³ , waste gas from COREX having a heat content of typically about 8 MJ / Nm ³ , or typically heavy oil or coal, but possibly waste And other substances such as synthetic gas produced by partial oxidation of solid or liquid fuels. Such gases are available from IGCC (integrated gasification combined cycle).
production cycle)) and is typically around 10-16 MJ
/ Nm ³ .

Generally speaking, the heat content of the fuel gas is between 4 and
If it exceeds 6 MJ / Nm ³ , there is no need to increase it.

However, including high calorific value fuels such as natural gas, LPG, fuel oil and solid fuels,
The use of any fuel is within the scope of the present invention.

The fuel is preferably combusted at a pressure close to the atmospheric pressure, suitably so that the path for discharging exhaust gas from the burner to the atmosphere does not have to be pressurized. This differs from previous proposals using gas turbines in that the exhaust is not manufactured under pressure so that it can extract work by expanding it.

[0027] The high nitrogen-rich stream used in the present invention is obtained from a cryogenic air separation unit. This nitrogen-rich stream may contain, in addition to nitrogen, at least one other gas from the air separation unit. Preferably, the oxygen separated in the air separation unit is supplied to the above-mentioned fuel gas or at least to a process for producing a low heat content component of the fuel gas. Such a process may, for example, operate a blast furnace or may be another fuel gas production process of the type described above. The oxygen product from the air separation unit may not all be available for consumption in the fuel gas production process, in which case some of the separated oxygen can be added back to the separated nitrogen to extract work. It may be advantageous to increase the amount of gas available.

Alternatively, the compressed air from the air separation unit may be added to the nitrogen stream, thus producing a nitrogen stream containing oxygen and other air gases.

Further, the air separation device may be operated so as not to completely separate oxygen and nitrogen. In general, the nitrogen content of the rich gas to the nitrogen then up with pure nitrogen in the air, for example up to 80 to 100 volume% of N _2, for example about 90%.

The work gained by the expansion of the heated, nitrogen-rich, high-pressure stream powers the compression train to compress in the air separator, for example, the compression of the air entering the air separator, the air separator. Compression of nitrogen in the air or compression of oxygen in the air separation unit can be provided. It may be used to operate a generator that can be used for the powering purposes described above, or may generally be used to supply electricity.

The nitrogen-rich stream before the heating step is preferably at a pressure of 2 to 20 bara (200 to 2000 kPa). More preferably, the nitrogen-rich stream is 2-7
bara (200-700 kPa) pressure. Generally, it is 2-5 bara (200-500 bara) when removed from the air separation unit without further compression.
kPa) pressure, for example 3 bara (300 kPa), or 5-7 bara if further compressed
(500-700 kPa).

It is suitably at a temperature between 400 and 1,000 ° C., more preferably between 600 and 800 ° C.

The nitrogen-rich stream may be expanded in a turbine to perform the external work described above, and the turbine may be an axial or radial turbine.

The heat should be recovered from the nitrogen-rich stream after performing the external work in the expansion step described above, and that heat is used to primarily heat the nitrogen-rich stream by burning the fuel gas. It is particularly preferred that this be passed to the incoming nitrogen-rich stream. This can be done simply by heat exchange between the outgoing nitrogen-rich stream and the incoming nitrogen-rich stream. Alternatively,
The outgoing nitrogen-rich stream may be added to the combustion products of the fuel gas that heats the incoming nitrogen-rich stream.
Still another method uses the heat from the emerging flue gas and the nitrogen-rich stream to vaporize a liquid, such as water, in the incoming nitrogen-rich stream to increase the mass flow rate, With or without increasing the temperature of the incoming nitrogen-rich stream, the recoverable energy of the stream may be increased.

The power supply from the combustion of the fuel to the nitrogen-rich stream is preferably between 0.75 and 9 kW / kg-mo.
1 N ₂ / h, for example, _{2 to 4} kW / kg-mol N ₂ / h
Is fine.

The nitrogen-rich stream is discharged to the atmosphere after use or for use in another process.

The first aspect of the invention is an apparatus for obtaining work from a nitrogen-rich high-pressure gas stream, comprising a source of a combustible fuel gas at a pressure of up to 5 bara (500 kPa); Or a source of liquid or solid fuel;
Means for burning the fuel gas or the liquid or solid fuel, a cryogenic air separation device as a source of the nitrogen-rich high-pressure stream, and the heat from the burning fuel to convert the nitrogen Means for indirectly heating the rich stream to produce a heated, high pressure stream rich in nitrogen;
Includes an apparatus that includes means for expanding the nitrogen-rich heated high pressure stream to perform external work, and for discharging the nitrogen-rich stream from the apparatus.

The source of the combustible fuel gas may be any of those described above, including those connected to the blast furnace. The apparatus may further include a source of high calorific value fuel gas as described above, either as a sole heating fuel source or as a regulator for a low calorific value fuel source.

As indicated above, the apparatus includes an air separation unit as a source of the nitrogen-rich stream, and further includes air supplied to the air separation unit for separation. And means for using the work gained by the expansion of the nitrogen-enriched heated high pressure stream to power the compression means.

Means for utilizing the work gained by the expansion of the above-described nitrogen-rich heated high-pressure stream to power other compression-requiring equipment of the air separation unit or to operate a generator. May be provided separately or additionally.

A connection system may be provided for supplying the oxygen separated by the above-mentioned air separation device to the above-mentioned fuel gas or a device for producing the main low heat content component thereof.

The apparatus may include a turbine as a means for expanding the nitrogen-rich heated high-pressure stream to obtain work, and extracting energy from the nitrogen-rich stream after the expansion step. And means for delivering it to the incoming nitrogen-rich stream.

In another aspect, the invention is a method of obtaining work from a high pressure stream rich in nitrogen, comprising supplying fuel to a combustion zone and burning the fuel to substantially increase pressure in the combustion zone. Producing an untreated exhaust gas stream and transferring the heat generated by this combustion to the nitrogen-rich high-pressure stream obtained from the air separation unit without mixing the nitrogen-rich stream and the exhaust gas stream, thereby heating it. Thereby producing a nitrogen-rich heated high-pressure stream, expanding the nitrogen-rich heated high-pressure stream to perform external work, and discharging the nitrogen-rich stream. I do.

The exhaust gas stream is generally at ambient pressure, except for any excess pressure above the ambient pressure required to allow the exhaust gas stream to flow through the device and exhaust to the environment. This flow is generally achieved without expanding the exhaust gas stream with devices that extract useful work therefrom.

According to this aspect of the invention, there is provided an apparatus for obtaining work from a nitrogen-rich, high-pressure stream, comprising: an air separation unit for producing a nitrogen-rich, high-pressure gas stream; Means for supplying to the zone, means for defining the combustion zone and burning the fuel to produce a substantially non-pressurized exhaust gas stream in the combustion zone, and transferring the heat generated by the combustion to the nitrogen Heat exchange means for conveying the nitrogen-rich stream and the exhaust gas stream to the high-pressure rich stream without mixing and heating it, thereby producing a heated high-pressure stream rich in nitrogen; and An apparatus is also provided that includes means for expanding the heated, high pressure stream to perform external work, and for discharging the nitrogen rich stream from the apparatus.

Preferred features of this alternative aspect of the invention include:
As described in relation to the first aspect of the present invention.

The present invention is further described and illustrated with reference to the accompanying drawings.

[0048]

DETAILED DESCRIPTION OF THE INVENTION The apparatus shown in FIG. 1 is connected to a heat exchanger 14 by a line 12 and from an air separation unit to a second heat exchanger 18 combined with a fuel burner 20 by a line 16. Inlet 10 for pressurized nitrogen
Having. The nitrogen flow passes from heat exchanger 18 via line 22 to the inlet of axial turbine 24, where it expands the nitrogen flow to perform external work and provides shaft power from the turbine. I do. Thereafter, the nitrogen travels via line 26 to the opposite side of heat exchanger 14 and is discharged therefrom via outlet 28. An inlet 30 is provided for air to sustain combustion, and an inlet 32 for combustible fuel gas. The inlet 32 is typically
An outlet for waste gas from the blast furnace is connected.

The air passes from inlet 30 via line 34 to a third heat exchanger 36. The fuel gas also travels from inlet 32 via line 38 to heat exchanger 36, where both are heated by heat exchange as described below. Air is supplied from the heat exchanger 36 to the burner 20 via a line 40, and fuel gas is supplied via a line 42. The products of combustion of the fuel gas and air produced in burner 20 travel in heat exchanger 18 in heat exchange with the nitrogen stream, and travel in heat exchanger 36 in heat exchange to supply air and fuel gas. To preheat. The products of combustion are discharged from heat exchanger 36 through outlet 46.

In use, the nitrogen stream coming from the inlet 10 is preheated in the heat exchanger 14 by the outgoing nitrogen stream after expansion of the nitrogen stream in the turbine 24 and then in the burner 20. The fuel gas is further heated in the heat exchanger 18 by the combustion of the air. In general, the nitrogen first travels in a zone where heat transfer is predominantly by convection, and then in a zone where heat transfer is predominantly by radiant burner flame.

The burner may generally be of the type specifically designed for combustion of low heat content fuel gases. It may be a regenerative burner that regeneratively preheats the supply air and / or fuel to the burner with a medium heated by the combustion process. Alternatively, it may be a burner designed to burn other gas, liquid or solid fuels.

In the alternative arrangement shown in FIG. 2, the heat exchanger 14 is omitted and the expanded nitrogen gas stream emerging from the turbine 24 is combined with the combustion products from the burners and, suitably, the heat exchanger. Mixing occurs between the radiation and convection zones of 18a. This combustion product, mixed with the nitrogen, then passes through another area of the heat exchanger 18a to heat the incoming nitrogen stream that goes directly to the heat exchanger 18a.

In another arrangement shown in FIG. 3, the expanded nitrogen gas stream emerging from the turbine is mixed with the products of combustion from the burner upstream of heat exchanger 18b. In this embodiment, the heat exchanger 18b has no radiating portion, and heat transfer is mainly by convection.

FIG. 4 shows yet another embodiment of an apparatus for recovering energy from an expanding nitrogen stream in a third manner, which does not have preheating of air and fuel gas. In this embodiment, air and fuel gas are supplied directly to the burner 20.
Nitrogen introduced from inlet 10 passes through line 12 to a water saturator 50 having an inlet line 52 for the heated water, through which the nitrogen stream becomes saturated. Water is withdrawn from saturator 50 through line 54 and sent to a pump 56 that circulates water and passes through line 58 to heat exchanger 60 where it is heated by the products of combustion from burner 20. You. The heated water passes through valve 62 to line 52, thereby being reintroduced into saturator 50. Make-up water is introduced via line 64 before the pump 56.

The saturated nitrogen exits the saturator 50 through line 65 and is heated in the heat exchanger 14 by heat exchange with the exhaust of the expander. It is further heated in heat exchanger 18 and then expanded in turbine 24, and the expanded nitrogen stream is then fed to the opposite side of heat exchanger 14 to provide additional heat to the incoming nitrogen stream. .

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Typical operating parameters of the apparatus shown in FIG. 1 are shown in Table 1 below, and typical operating parameters of the apparatus shown in FIGS. 2 and 4 are shown in Tables 2 and 3 below.
Shown in The unit of pressure bar in these tables is 10
It corresponds to ⁵ Pascal (Pa).

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

EXAMPLE 1 In a typical example of the operation of the present invention using the apparatus shown in FIG.
ara (600 kPa) and 35 in heat exchanger 14 by indirect heat exchange with a nitrogen stream exiting the turbine cooled from 400 ° C. to 122 ° C.
Heat to 0 ° C. This preheated nitrogen enters the convection section of the heater with burner 20 and heat exchanger 18 and then enters the radiant heat transfer section where it is heated to 700 ° C.

Next, the high-temperature nitrogen flow is transferred to the axial turbine 24.
To generate the shaft power used to supply some of the energy required by the air compressor of the air separation unit.

The fuel gas used in the burner is 4.4
A fuel gas with a true calorific value of MJ / Nm ³ , for example blast furnace gas, possibly mixed with a small amount of coke oven gas or natural gas or LPG to promote combustion. The fuel gas stream and the combustion air stream, both initially at 20 ° C., are preheated to 303 ° C. in heat exchanger 36 before entering burner 20. Flue gas from the burner exits the heat exchanger 36 at 120 ° C. and is released to the atmosphere. The performance achieved in this device is as follows.

Nitrogen flow rate = 4747.6 kgmol / h Nitrogen inlet pressure = 6 bara (600 kPa) Nitrogen inlet temperature = 700 ° C. Generation shaft power = 12.2 MW Fuel gas calorific value (LHV) = 15.83 MW

Although the invention has been described with reference to the above illustrated specific embodiments, it should be recognized that many changes and modifications of the invention are possible within the scope of the invention.

An advantage of the illustrated invention is that the expansion of nitrogen in an expander with high adiabatic efficiency efficiently recovers internal energy from waste nitrogen in an air separation unit that is available at high pressure. Preheating the nitrogen to the highest temperature that can be tolerated by the expander maximizes the amount of shaft power produced. Heat exchange of nitrogen first with the low-pressure expander exhaust and secondly with a flame-heated heater maximizes the efficiency of heat-to-axial energy conversion by indirect heating. This is facilitated by preheating the combustion air and fuel gas with heat exchange with the flue gas of a flame heated heater. The use of a flame-heated heater with indirect nitrogen heating means that compression of the fuel gas or combustion air is not required, thus maximizing the efficiency of the process. This is particularly important when utilizing very low calorific value fuels such as blast furnace gas.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a first embodiment according to the present invention.

FIG. 2 is a schematic explanatory view of a second embodiment according to the present invention.

FIG. 3 is a schematic explanatory view of a third embodiment according to the present invention.

FIG. 4 is a schematic explanatory diagram of a fourth embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Nitrogen inlet 14, 18, 18a, 18b, 36, 60 ... Heat exchanger 20 ... Combustion burner 24 ... Axial flow turbine 30 ... Air inlet 32 ... Fuel gas inlet 50 ... Saturator 56 ... Pump

Continuation of the front page (72) Inventor Anthony Nat James Topham, UK, Slay Katy 12 2 Queue, Walton on Thames, Mayo Road 30 (72) Inventor Rodney John Alam, UK, Slay GU 25 EE, Guild Ford, Gildown Road 33, Westerker

Claims (30)

[Claims] 1. A method for obtaining work from a nitrogen-rich, high-pressure gas stream obtained from a cryogenic air separation unit, comprising:
A low-temperature air separation is performed to produce a nitrogen-rich, high-pressure gas stream and up to 5 bara (500 kP
a) supplying a liquid or solid fuel at a pressure up to a), burning said fuel, and indirectly heating said nitrogen-rich stream using the heat obtained from the combustion of said fuel to produce nitrogen Producing a heated, high-pressure stream rich in nitrogen, expanding the heated, high-pressure stream rich in nitrogen to perform external work, and discharging the nitrogen-rich stream, A way to get work from a high pressure gas stream. 2. When the fuel has a maximum of 3 bara (300 k
2. The method according to claim 1, wherein the fuel gas is supplied to the combustion zone at a pressure up to Pa). 3. The pressure of the fuel gas is 1.1 to 2.5 b.
3. The method according to claim 2, wherein the ara is from 110 to 250 kPa. 4. The fuel gas has a pressure of 1.1 to 1.2 b.
3. The method of claim 2, wherein said ara is from 110 to 120 kPa. 5. The fuel gas having a heat content of 2.5 to 16M.
At least mainly supplied, The method according to any one of claims 1 to 4 from a source of fuel gas which is J / Nm ^3. 6. The method according to claim 5, wherein the fuel gas having a heat content is waste gas from a blast furnace, waste gas of COREX, or synthesis gas from partial oxidation of a solid or liquid fuel. 7. The method of claim 6, wherein the gas is burned without compression. 8. The method according to claim 6, wherein the fuel gas having a heat content is mixed with a smaller amount of gas having a substantially higher heat content. 9. The method of claim 8, wherein the higher heat content gas is coke oven gas, natural gas, or LPG. 10. The heat content is 2.5 to 16 MJ / Nm.
³ , the fuel gas has a heat content of 2.5 to 4 MJ / Nm
³ a and and the gas heat content to raise the heat content of the resulting mixture is mixed with substantially higher sufficient gas to 4~6MJ / Nm ^3, The method of claim 8 or 9, wherein . 11. The method according to claim 8, wherein the lower amount is at most an amount sufficient to double the heat content of the fuel gas to which the higher heat content gas is added. The described method. 12. The method according to claim 1, wherein the fuel is natural gas, LPG, fuel oil or solid fuel. 13. The method according to claim 1, wherein the nitrogen-rich stream contains, besides nitrogen, at least one other gas from the air separation unit. . 14. The process of claim 1, wherein the work obtained by expansion of the nitrogen-rich heated high pressure stream is used to power the compression of gas in the air separation unit.
The method according to any one of the above. 15. The method according to claim 1, wherein oxygen separated in the air separation device is supplied to a process for producing the fuel. 16. Prior to the step of performing the heating, the nitrogen-rich stream is provided with 2 to 20 bara (200 to 200 bara).
16. The method according to claim 1, wherein the pressure is 0 kPa). 17. The method according to claim 1, wherein the nitrogen-rich stream has a flow of 2 to 7 bara (200 to 700 k
17. The method according to claim 16, wherein the pressure is Pa). 18. The method according to claim 1, wherein the nitrogen-rich stream is at a temperature between 400 and 1000 ° C. before the expansion. 19. The method according to claim 19, wherein the nitrogen-rich stream is between 600 and 80.
19. The method of claim 18, wherein the temperature is 0C. 20. The method according to any one of the preceding claims, wherein the nitrogen-rich heated high pressure stream is expanded in a turbine to perform the external work. 21. Transferring heat remaining in the nitrogen-rich stream after performing the external work in the expansion step to the nitrogen-rich high-pressure stream, and then removing the nitrogen-rich stream. 21. The method according to any one of the preceding claims, wherein heating is performed using heat from the combustion of the fuel gas. 22. The method according to claim 1, wherein the power obtained from the combustion of the fuel is 0.75 to 9 kW / kg-mol N ₂ / h. 23. An apparatus for obtaining work from a nitrogen-rich high-pressure stream, comprising up to 5 bara (500 kPa).
A source of combustible fuel gas at a pressure of up to 32 or a source of liquid or solid fuel and means for burning said fuel gas or said liquid or solid fuel (20)
And a cryogenic air separation unit as a source of the nitrogen-rich high pressure stream, and indirectly heating the nitrogen-rich stream using heat from the burning fuel to heat the nitrogen-rich stream Means (18) for producing a regulated high-pressure stream, means (24) for expanding the nitrogen-rich heated high-pressure stream to perform external work, and Means (28) for discharging from said device. 24. The apparatus of claim 23, further comprising another source of a gas having a heat content substantially greater than 4 MJ / Nm ³ . 25. A means for compressing the air supplied for separation in said air separation device and powering the work obtained by expansion of said nitrogen rich heated high pressure stream to said compression means. 25. Apparatus according to claim 23 or claim 24, further comprising means for using to supply. 26. The apparatus according to claim 23, wherein the oxygen separated by the air separation apparatus is supplied to an apparatus for producing the fuel gas. 27. Apparatus according to any one of claims 23 to 26, wherein said means (24) for expanding said nitrogen-rich heated high pressure stream comprises a turbine. 28. The method according to claim 23, comprising means for extracting energy from the nitrogen-rich stream after the step of expanding and transferring this energy to the incoming nitrogen-rich stream. 28. The apparatus according to any one of the preceding claims. 29. A method of obtaining work from a nitrogen-rich, high-pressure stream comprising feeding fuel to a combustion zone and burning the fuel to produce a substantially unpressurized exhaust gas stream in the combustion zone. The heat generated by this combustion is transferred to the nitrogen-rich high pressure stream obtained from the air separation unit without mixing the nitrogen-rich stream and the exhaust gas stream to heat it, thereby heating the nitrogen-rich heating. Producing a controlled high pressure stream, expanding the nitrogen rich heated high pressure stream to perform external work, and discharging the nitrogen rich stream. 30. An apparatus for obtaining work from a nitrogen-rich, high-pressure stream, comprising: an air separation unit for producing a nitrogen-rich, high-pressure gas stream; and means for supplying fuel to a combustion zone. Means for defining the combustion zone and burning the fuel to produce a substantially non-pressurized exhaust gas stream in the combustion zone; and transferring the heat generated by the combustion to the nitrogen-rich stream. Heat exchange means (18) for conveying the nitrogen-rich stream and the exhaust gas stream without mixing to heat it, thereby producing a nitrogen-rich heated high pressure stream; and An apparatus comprising: means (24) for expanding the heated high pressure stream to perform external work; and means (28) for discharging the nitrogen-rich stream from the apparatus.