JP2007512491A - Method and apparatus for concentrating one component of a gas stream - Google Patents

Abstract

It relates to a method for concentrating one component (A) of a pressurized gas stream. The method of the present invention includes the following steps. The stream is divided into at least a first fraction and a second fraction (2, 3); at least a part of the first fraction is sent to a separation unit (ASU); the separation unit is fed to the separation unit Supply at least two discharges including a first discharge (10) having a higher A content than fraction (2); at least a portion of the first discharge is mixed with at least a portion of the second fraction (3) A pressurized gas mixture (15) is formed. The second fraction is expanded and then mixed with at least a portion of the first discharge.
[Selection] Figure 3

Description

  The present invention relates to a method and apparatus for enriching one component of a gas stream. In particular, it relates to a method of concentrating air with oxygen.

  Oxygen enrichment of air is necessary in the steel industry.

  The reduction or elimination of thermal coke in blast furnaces generally requires this necessary change for the benefit of coal powder input (CPI).

  In order to achieve this enrichment economically, the means known from EP-A-0531182 consists of a cryogenic distillation of part of the blast furnace air stream. The result is a stream rich in nitrogen and a stream rich in oxygen, the latter then being remixed into the air stream downstream of the air separation unit.

  Since the pressure of the oxygen stream is close to the pressure of the air stream supplied to the air separation unit (ASU), a method involving a mixing column has been found to be particularly suitable and economical.

FIG. 1 shows a separation unit described in EP-A-0531182 for concentrating air with oxygen. This is supplied from the air system which constitutes the blast furnace input at pressure P. The air distillation unit has a low purity oxygen, for example 80-97%, at a predetermined pressure slightly higher than the pressure P, for example, preferably at a pressure of 1 × 10 ⁴ Pa abs to 1 × 10 ⁵ Pa abs higher than the pressure P. And preferably is intended to produce oxygen of 85-95% purity.

This unit essentially comprises a heat exchange line 1A, a double distillation column 2A, the double distillation column itself comprises a medium pressure column 3A, a low pressure column 4A, a main condenser-reboiler 5A, and a mixing column 6A. Columns 3A and 4A typically operate at about 5.45 × 10 ⁵ Pa and about 1.5 × 10 ⁵ Pa, respectively.

  As described in detail in document US Pat. No. 4,022,030, the mixing column is a column having the same structure as the distillation column, but is relatively volatile which is introduced into the bottom of the column in a nearly reversible manner. The gas is used to mix the low volatility liquid introduced at the top of the column.

  Such mixing generates cooling energy and thus reduces the energy consumption associated with distillation. In this case, as will be described later, this mixing is also advantageously used for impure oxygen to be produced directly at pressure P.

  In the case of FIG. 1, the air stream is compressed to the pressure of the mixing column by the compressor 14A, cooled in the exchange line 1A, subcooled by the subcooler 21A, and sent to the bottom of the mixing column 6A.

  The “rich liquid” (air rich in oxygen) taken out from the bottom of the column 3A is expanded by the expansion valve 10A and then introduced into the column 4A. The “lean liquid” (impure nitrogen) taken out from the intermediate point 11A of the column 3A is expanded by the expansion valve 12A, and then constitutes the exhaust gas of the apparatus. This gas and medium pressure pure gaseous nitrogen that can be produced at the top of the column 3A are warmed in the exchange line 1A and discharged from the apparatus. These gases are denoted by NI and NG in FIG. 1, respectively.

Depending on the setting of the double column 2A, the liquid oxygen is extracted from the column 4A with a high or low purity, and a pressure P1 slightly higher than the pressure P in order to take account of pressure drop (P1-P is less than 2 × 10 ⁵ Pa). And introduced into the top of the column 6.

  Three liquid streams are withdrawn from the mixing column 6A. From the bottom, a liquid similar to the rich liquid and combined with the rich liquid via a line 15A with an expansion valve 15A ′, from the middle point, the low pressure column 4A via a line 16A with an expansion valve 17A The mixture consisting essentially of oxygen and nitrogen sent to the impeller, and from the top, after being warmed in the heat exchange line, impure discharged from the apparatus via line 18A as production gas OI at substantially pressure P It is oxygen.

  The figure also shows auxiliary heat exchangers 19A, 20A, 21A for recovering available cooling from the fluid circulating through the device.

FIG. 2 schematically shows an integrated device for concentrating a blast furnace air flow according to the prior art. The air flow is compressed by a blower S to form a compressed flow. This stream is divided into two fractions 2 and 3. The first fraction 2 is cooled with a chiller R, for example a water chiller, compressed with a booster C and sent to an air separation unit (ASU). The air separation unit operates, for example, by cryogenic distillation and includes a purification unit and an exchange line upstream of the separation column. An oxygen stream 10 comprising 80-95 mol% oxygen and a nitrogen stream 11 which can be a waste stream are produced. At least a portion of the oxygen rich stream mixes with the second air fraction 3. The mixed stream 15 rich in oxygen is heated by a cowpers W and sent to the blast furnace BF.

  Compressor C is installed to prevent pressure drop in the circuit including the air separation unit (between air intake and oxygen flow reinjection in the blast furnace wind into the separation unit). This increases the pressure of the total air flow for the air separation unit (according to FIG. 2) or (as a variant of FIG. 1) to the mixing column (ie about 30% of the air flow processed in the separation unit). Make it possible to do.

  It is an object of the present invention to produce iron in a more economical and more reliable manner without using a gas flow compressor in an air separation unit other than that connected to the shaft of an expansion turbine to maintain cooling of the separation unit. Is to integrate an air separation unit.

The subject of the present invention is a method for concentrating a pressurized gas stream with its one component A, which comprises the following steps.
i) dividing the stream into at least a first fraction and a second fraction;
ii) sending at least a portion of the first fraction to the separation unit;
iii) supplying from the separation unit at least a first stream and a second stream, the first stream having a higher content of component A than the first fraction;
iv) mixing at least a portion of the first stream with at least a portion of the second fraction to form a pressurized gas mixture;
The method is characterized in that the second fraction is expanded before mixing at least a portion of the first stream.

According to other optional aspects,
The pressurized gas flow and the first fraction are at substantially the same pressure, and in particular, only the pressure drop is responsible for the pressure change between these two fluids,
The first flow and the expanded second fraction are at substantially the same pressure, and in particular, only the pressure drop is responsible for the pressure change between these two fluids,
The separation unit is autonomous with respect to the energy demand for compressing the gas flow produced by the unit or for the unit;
The pressurized gas stream is air and optionally component A is oxygen,
-The pressurized gas flow is blast furnace air,
-The separation unit is a cryogenic distillation separation unit,
The separation unit comprises an intermediate pressure column, a low pressure column thermally coupled to the intermediate pressure column, and a mixing column;
-No part of the first fraction for the distillation column is compressed or any part of the first fraction for the mixing column or medium pressure column is not compressed after the stream has been separated.

According to one particular method of operation, i) in the first operation, at least part of the first fraction is compressed and the second fraction is before at least part of the first fraction is mixed with it. Ii) In the second operation, at least a portion of the first fraction is not compressed (eg, the first fraction is not compressed) in the second operation (eg, when compressor C is not operating), and at least of the first flow The second fraction is expanded before a part is mixed with it.

Another subject of the invention is an apparatus for concentrating a pressurized gas stream with its component A,
i) means for dividing the pressurized gas stream into at least a first fraction and a second fraction;
ii) separation unit,
iii) means for sending at least part of the first fraction to the separation unit;
iv) At least part of the first stream produced in the separation unit and enriched with A compared to the first fraction is mixed with the second fraction to concentrate A compared with the pressurized gas stream. Means to form a stream,
And means for expanding the second fraction upstream of the means for mixing at least a portion of the first stream and downstream of the means for dividing the gas stream.

According to other optional aspects,
The separation unit is an air separation unit comprising a medium pressure column, a low pressure column thermally coupled to the medium pressure column, and a mixing column;
The device does not include means for compressing air for medium pressure columns or mixing columns; and
The device comprises means for compressing the second fraction and means for sending the second fraction mixed with at least a portion of the first stream without passing through the expansion means;

  Advantageously, the separation method uses a mixing column operating at a pressure equal to or higher than that of the intermediate pressure column without the need for additional air compression means.

  Thus, it is proposed to integrate the mixing column unit into a blast furnace blaster without an additional air compressor. Thus, increasing the reliability of delivery of oxygen molecules and thus concentrated air to the blast furnace while minimizing the investment required for this construction.

Another subject of the present invention is the use of an apparatus comprising at least one medium pressure column, a low pressure column thermally connected to the low-medium pressure column, and a mixing column operating at a pressure higher than that of the medium pressure column. Is a method of separating
i) sending air, pressurized and purified air to a medium pressure column;
ii) sending a nitrogen-rich and oxygen-rich stream from the medium pressure column to the low pressure column;
iii) sending an oxygen rich liquid from the low pressure column to the top of the mixing column;
iv) in a method for removing an oxygen-rich gas from the top of the mixing column;
A nitrogen-rich liquid stream is removed from the medium pressure column, pressurized and at least partially evaporated, and at least a portion of the evaporated liquid is fed to the bottom of the mixing column.

  Preferably, the nitrogen rich liquid is evaporated by heat exchange with a portion of the supply air. The liquefied air can be sent to at least one of the medium pressure column and the low pressure column.

  The nitrogen rich liquid is pressurized by a pump and / or static pressure.

Another subject of the invention is an air separation device,
a) medium pressure column,
b) a low pressure column thermally coupled to a low-medium-pressure column;
c) a mixing column operating at a pressure higher than that of the medium pressure column;
d) means for sending compressed and purified air to the medium pressure column;
e) means for sending a stream rich in nitrogen and a stream rich in oxygen from a medium pressure column to a low pressure column;
f) means for sending an oxygen rich liquid from the low pressure column to the top of the mixing column;
g) includes a means for removing an oxygen rich gas from the top of the mixing column;
The apparatus includes means for removing a liquid stream rich in nitrogen from the medium pressure column, means for pressurizing the liquid, means for at least partially evaporating the liquid, and means for supplying at least a portion of the evaporated liquid to the bottom of the mixing column. It is characterized by that.

  The present invention will be described in detail with reference to FIGS. FIGS. 3 and 5 show a unit for concentrating a gas stream according to the invention, and FIG. 4 shows a separation unit particularly suitable for carrying out the invention.

  FIG. 3 schematically shows an integrated unit for enrichment of airflow for a blast furnace according to the prior art.

  The air flow is compressed by the blower S to form a compressed flow 1. This stream is divided into two fractions 2 and 3. The first fraction 2 is cooled by a chiller R, for example a water chiller, and sent to the air separation unit without being compressed between the chiller and the inlet of the air separation unit (ASU). The air separation unit operates, for example, by cryogenic distillation and includes a purification unit and an exchange line upstream of the separation column. This produces an oxygen stream 10 containing 80-95 mol% oxygen and a nitrogen stream 11 which can be a waste stream. The second air fraction 3 is expanded by expansion means V, which can be, for example, a valve, an orifice, a reduced diameter pipe or a turbine. At least a part of the oxygen-rich stream 10 mixes with the expanded second air fraction 3 downstream of the expansion means V. The mixed stream 15 rich in oxygen is heated in the cowper W and sent to the blast furnace BF.

  This solution eliminates the need for an air booster to increase the pressure upstream of the air separation unit. Therefore, the energy consumption of the whole system is good.

  FIG. 4 employs the elements of FIG. 1 that have the same reference numbers, although not described in detail.

  The 5.45 bar medium pressure purified air 7a coming from the main air compressor or expansion turbine for blast furnace wind is split into at least two separate streams before entering the medium pressure column 2A.

  The first stream 100 is in a gaseous state and is supplied directly to the bottom of the intermediate pressure column 2A.

  The second stream 200 is at least partially condensed in the heat exchanger 101A. The liquefied part is introduced into one of the distillation columns (either the medium pressure column 2A or the low pressure column 4A). In FIG. 4, stream 204 is sent to the bottom of the medium pressure column, but stream 204 is sent to the low pressure column after being subcooled in exchanger 19A.

  A liquid stream 300 rich in nitrogen compared to air is taken from the intermediate pressure column 3A, compressed by the pump 400 or at a mere hydrostatic height and evaporated in the heat exchanger 101A against the condensation of medium pressure air to form gaseous nitrogen A stream 500 is formed and then fed to the bottom of the mixing column 6A. Thus, using the difference in composition between the air and the nitrogen-rich stream, the supply for the mixing column 6A takes place at a pressure above the pressure of the air 100 supplying the intermediate pressure column 3A, and the additional compressor Done without using.

  It is also conceivable to warm the gaseous nitrogen 500 in the main exchange line before introducing it into the mixing column.

  In order to produce a gaseous nitrogen stream 500 of 5.9 bar, the heat exchanger 101A has a ΔT of 0.6 ° C.

  Stream 15A coming from the bottom of mixing column 6A is richer in nitrogen than that of FIG. 1 and is sent directly below the top of low pressure column 4A.

  The subcooler 21A is omitted, and the medium-pressure gaseous nitrogen NG is not taken out.

  Optionally, the third stream of air is sent to booster 8A, cooled in exchange line 1A, and expanded in blown turbine 9A, although other cooling means are contemplated, including expansion of air for medium pressure columns.

  When this booster is present, an advantage of the present invention is that there is no need for an air compression step for air for mixing columns or medium pressure columns.

  In the case of FIG. 4, the extraction efficiency is reduced and the separation energy of the system is superior to the basic case.

  However, the integration of the air separation unit of FIG. 4 into the scheme disclosed in the variant shown in FIG. 3 makes it possible to significantly reduce the pressure drop in the valve.

  FIG. 5 schematically shows an integrated unit for concentrating the air flow for a blast furnace according to the prior art.

  The air flow is compressed by the blower S to form a compressed flow 1. This stream is divided into two fractions 2 and 3. The first fraction 2 is cooled by a chiller R, for example a water chiller, compressed by a booster C and sent to an air separation unit (ASU). This air separation unit operates, for example, by cryogenic distillation and includes a purification unit and an exchange line upstream of the separation unit. This produces an oxygen stream 10 containing 80-95 mol% oxygen and a nitrogen stream 11 that can be a waste stream. The second air fraction 3 is expanded by expansion means V, which can be, for example, a valve, an orifice, a reduced diameter pipe or a turbine. At least a portion of the oxygen-rich stream 10 is mixed with the second air fraction expanded downstream of the expansion means V. The oxygen rich mixed stream 15 is heated by the cowper W and sent to the blast furnace BF. Booster C and valve V have short circuiting means. In the first operation of the unit, the first fraction is compressed and the second fraction is not expanded. In the second operation, at least a portion of the first fraction is not compressed and the second fraction is expanded before at least a portion of the first stream is mixed.

Deformation evaluation
Conventional technology

Deformation 1 with expansion valve (Fig. 3)

Modification 2 by expansion method (Fig. 3) and air separation method of Fig. 4

The figure which shows the concentration method by a prior art. The figure which shows typically the apparatus which integrated the apparatus which concentrates the airflow for blast furnaces by a prior art. FIG. 3 shows an integrated unit for concentrating a gas stream according to the invention. 1 shows a separation unit that is particularly suitable for carrying out the present invention. FIG. The figure which shows the unit which concentrates the gas flow by this invention.

Claims (14)

A method of concentrating one component of a pressurized gas stream,
i) dividing the stream (1) into at least a first fraction and a second fraction (2, 3);
ii) sending at least a portion of the first fraction (2) to the separation unit (ASU);
iii) supplying at least first and second streams from the separation unit, the first stream (10) having a higher content of component A than the first fraction;
iv) in a method comprising mixing at least a portion of the first stream with at least a portion of the second fraction to form a pressurized gas mixture (15),
Expanding the second fraction before at least a portion of the first stream is mixed. The pressurized gas stream (1) and the first fraction (2) are at substantially the same pressure, and in particular, only the pressure drop is responsible for the change between the pressures of these two fluids. The method according to 1. The first stream and the expanded second fraction are at substantially the same pressure, and in particular, only the pressure drop is responsible for the change in pressure of these two fluids. The method described. 4. A method according to any one of the preceding claims, wherein the separation unit (ASU) is autonomous with respect to the energy demand arising in the unit or for compression of the gas flow for the unit. A process according to any of claims 1 to 4, wherein the pressurized gas stream (1) is air and optionally component A is oxygen. 6. The method of claim 5, wherein the pressurized gas stream is blast furnace (BF) air. The method according to claim 1, wherein the separation unit is a cryogenic distillation separation unit (ASU). The method according to claim 7, wherein the separation unit (ASU) comprises an intermediate pressure column (2A), a low pressure column (4A) thermally connected to the intermediate pressure column, and a mixing column. No part of the first fraction for the distillation column is compressed or any part of the first fraction for the mixing column or medium pressure column is not compressed after the stream has been divided in step i). 9. The method according to 8. i) in the first operation, at least a portion of the first fraction is compressed and the second fraction is not expanded before at least a portion of the first fraction is mixed; and ii) in the second operation At least a portion of the first fraction is not compressed (the first fraction is not compressed), and the second fraction is expanded before at least a portion of the first stream is mixed;
The method according to claim 1. An apparatus for concentrating one component A of a pressurized gas flow,
i) means for dividing the pressurized gas stream (1) into at least a first fraction and a second fraction (2, 3);
ii) separation unit (ASU),
iii) means for sending at least part of the first fraction (2) to the separation unit; and iv) at least of the first stream (10) produced in the separation unit and enriched with A compared to the first fraction. In an apparatus comprising means for mixing a portion with a second fraction to form a stream (15) enriched in A compared to a pressurized gas stream,
An apparatus comprising means (V) for expanding the second fraction upstream of the means for mixing with at least a portion of the first stream and downstream of the means for dividing the gas stream. The apparatus according to claim 11, wherein the separation unit is an air separation unit (ASU) comprising an intermediate pressure column (3A), a low pressure column (4A) thermally connected to the intermediate pressure column, and a mixing column (6A). . 13. The apparatus of claim 12, wherein the apparatus does not include means for compressing air for a medium pressure column or for a mixing column downstream of the means for dividing the gas stream. 13. Apparatus according to any of claims 11 and 12, comprising means for compressing the second fraction and means for sending the second fraction to be mixed with at least a portion of the first stream without passing through the expansion means. .

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