JP2008143770A - Waste heat recovery system and waste heat recovery device - Google Patents

Abstract

A high-efficiency energy recovery system and a waste heat recovery apparatus are provided.
Carbon dioxide gas or water vapor is added to dimethyl ether, a reforming reaction is performed by waste heat to obtain synthesis gas or hydrogen gas, and pressure energy of the obtained synthesis gas or hydrogen gas is converted into mechanical energy or electrical energy. Convert to energy. For example, in FIG. 1, a gas generated by a reforming reaction and volume-expanded is introduced into an expansion turbine 2 from a reforming reactor 1, and the expansion turbine 2 rotates the turbine by the pressure energy of the introduced gas. , Convert to mechanical energy for power generation. On the other hand, the synthesis gas or hydrogen gas that has passed through the expansion turbine 2 is introduced into a by-product gas line of a blast furnace or a caulk factory as usual, and stored in the gas holder 5 as fuel energy, and as fuel energy in a power plant or factory. Used.
[Selection] Figure 1

Description

  The present invention relates to a waste heat recovery system and a waste heat recovery apparatus that recovers energy from waste heat using a reforming reaction of dimethyl ether.

For example, some exhaust heat at steelworks, etc., is recovered by technologies such as a sintered cooler exhaust heat recovery facility and a coke dry fire extinguishing facility, but a large amount of exhaust heat is not recovered and waste heat is recovered. It has become. The reason for this is that the exhaust heat obtained from granulated slag production or the rapid cooling process of the rolling process is hot water of several tens of degrees and has no use, or a part of the exhaust heat is recovered with low-pressure steam. This has already been done in the steelworks, but the demand for low-pressure steam is not so large as to meet the amount of exhaust heat. For this reason, most of the exhaust heat from the equipment such as sintering equipment and coke production equipment, and the sensible heat such as coke oven gas and blast furnace gas, which is exhaust heat at a temperature that is recovered with low-pressure steam, is recovered. The current situation is not.
Therefore, among these waste heats, as a technique for effectively utilizing waste heat of about 200 ° C. or 300 ° C., a method of obtaining a gas composed of hydrogen and carbon monoxide by reacting dimethyl ether with carbon dioxide gas or water vapor (hereinafter referred to as modified). It is well known that a so-called quality reaction has been proposed.

  For example, Patent Document 1 discloses a method in which dimethyl ether is reformed by adding steam or carbon dioxide gas to dimethyl ether to cause a catalytic reaction to obtain synthesis gas or hydrogen gas, and this gas is used as a fuel for a prime mover. Yes.

In Patent Document 2, water is first evaporated by exhaust heat of 200 ° C. class, and then the resulting mixed gas of water vapor and dimethyl ether is converted to hydrogen rich gas by exhaust heat of 300 ° C. class using a catalyst. A method of converting to is disclosed.
And since the gas obtained by the reforming reaction of patent documents 1 and 2 contains a component which can be used as fuels, such as hydrogen or carbon monoxide, existing by-product gas (blast furnace gas, coke oven gas, etc.) After being mixed in the line and once stored in the gas holder, it is sent to the power plant or each factory. Since the pressure of the gas stored in the gas holder is around 500 mmAq (0.005 MPa) in terms of gauge pressure, the gas obtained by the reforming reaction is decompressed and introduced into the byproduct gas line. The above outline is shown in FIG. 3 as a system diagram showing the configuration of a conventional waste heat recovery system.
According to FIG. 3, dimethyl ether is mixed with carbon dioxide or water (steam) via a pump 4 and supplied to the reforming reactor 1 filled with the reforming reaction catalyst. In the reforming reactor 1, the reforming reaction proceeds by the waste heat from the factory and the action of the catalyst. The synthesis gas or hydrogen gas generated by the reforming reaction is depressurized to the extent that it can be stored in the gas holder 5 by the pressure reducing valve 7, and then introduced into the byproduct gas line 8. The synthesis gas or hydrogen gas introduced into the byproduct gas line 8 is stored in the gas holder 5 and used as fuel in a power plant, factory, or the like. Here, the reason why the generated gas is stored in the gas holder is to cope with the load fluctuation on the side (for example, power plant) that uses the gas. In other words, the usage of blast furnace and coke oven on the generation side cannot be changed according to the fluctuation on the demand side, even though the usage amount of gas and electricity fluctuates during the night and daytime throughout the day and throughout the day. It is because.
JP-A-11-106770 JP 2004-144018 A

  As described above, as a method for recovering waste heat, a method has been conventionally proposed in which fuel gas such as hydrogen gas or synthesis gas is obtained by using waste heat in a reforming reaction of dimethyl ether and used as fuel energy. However, the use of energy other than fuel energy is not considered at all for the recovery of waste heat energy, and the waste heat recovery method must rely only on recovery as fuel energy. It was not expensive.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a high-efficiency energy recovery system and a waste heat recovery apparatus that fully utilize the characteristics of the reforming reaction.

The inventors of the present invention have made extensive studies in order to solve the above problems by paying attention to the reforming method developed previously. As a result, the following knowledge was obtained.
The synthesis gas or hydrogen gas generated by the reforming reaction is generated as a volume-expanded gas due to the characteristics of the reforming reaction. However, conventionally, the pressure energy generated by the volume expansion has not been effectively used, for example, when the volume expanded gas is used under reduced pressure when introduced into a by-product gas line. And it has not been considered at all to effectively use this pressure energy. Therefore, in the present invention, paying attention to the pressure of the synthesis gas or hydrogen gas obtained by the reforming reaction and volume-expanded, a system using this pressure energy has been devised. As a result, the recovery energy can be increased by combining both the conventional fuel energy and the pressure energy of the present invention, and the efficiency of waste heat recovery can be further improved.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A waste heat recovery system that recovers energy from waste heat by a reforming reaction of dimethyl ether, adding carbon dioxide or steam to the dimethyl ether, performing the reforming reaction by the waste heat, and syngas or hydrogen gas And converting the pressure energy of the obtained synthesis gas or the hydrogen gas into mechanical energy or electrical energy.
[2] The waste according to [1], wherein any one or more of the dimethyl ether, the carbon dioxide gas, and the water vapor used in the reforming reaction is heated by waste heat before the reforming reaction. Heat recovery system.
[3] The waste heat recovery system according to [1] or [2], wherein the waste heat is less than 600 ° C., and the reforming reaction is performed using a catalyst.
[4] The waste heat recovery system according to [1] or [2], wherein the waste heat is 600 ° C. or higher, and the reforming reaction is performed without using a catalyst.
[5] The waste heat recovery system according to any one of [1] to [4], wherein the waste heat is waste heat of a steelworks.
[6] In any one of the above [1] to [5], the pressure of the synthesis gas or the hydrogen gas obtained by the reforming reaction is converted into power, and the power is used for power generation. Waste heat recovery system.
[7] A reforming reactor for generating synthesis gas or hydrogen gas by reacting dimethyl ether with carbon dioxide gas or water vapor by waste heat, and pressure energy of the synthesis gas or hydrogen gas generated in the reforming reactor The waste heat recovery apparatus having an expansion turbine that is rotated by the rotation turbine and a converter that converts mechanical energy or electrical energy by rotation of the expansion turbine.
[8] In the above [7], the waste further having a heat exchanger that heats any one or more of the dimethyl ether, the carbon dioxide gas, and the water vapor by waste heat before being introduced into the reforming reactor. Heat recovery device.
[9] The waste heat recovery apparatus according to [7] or [8], wherein a boiler of a coke dry fire extinguishing facility is used as the reforming reactor.

According to the waste heat recovery system of the present invention, waste heat energy can be recovered efficiently. And it is possible to effectively recover and utilize the medium and low temperature waste heat of less than 600 ° C. and the waste heat of 600 ° C. or more, such as steelworks, and it is possible to further improve the heat utilization efficiency.
As an example, when power generation is performed using waste heat energy using the waste heat recovery system of the present invention, an increase in power amount of about 12% can be expected compared to the power generation amount obtained by the conventional method. When this increase in electricity is converted into coal, for example, when applied to a steel mill with annual crude steel production of 10 million tons, it is equivalent to saving 200,000 tons of coal annually, and carbon dioxide emissions are annual. A reduction of about 450,000 tons can be expected.

Below, the detail of the waste-heat recovery system of this invention is demonstrated.
For example, when energy is to be recovered by using a reforming reaction of dimethyl ether to recover waste heat from a steel mill, pressure energy due to volume expansion is generated in addition to fuel energy such as synthesis gas and hydrogen gas. The present invention is characterized in that a highly efficient energy recovery system is constructed by recovering the pressure energy that has not been recovered so far. That is, the present invention is a waste heat recovery system that recovers energy from waste heat using a reforming reaction of dimethyl ether, and a synthesis gas is obtained by adding carbon dioxide gas or steam to the dimethyl ether and performing the reforming reaction by waste heat. Alternatively, hydrogen gas is obtained and, in addition to using the obtained synthesis gas or the hydrogen gas as fuel energy, the pressure energy of the obtained synthesis gas or the hydrogen gas is converted into mechanical energy or electrical energy. .
Thus, by converting the pressure energy that has not been used at all to mechanical energy or electrical energy, the energy recovery rate is improved compared to the conventional case, and highly efficient waste heat recovery is possible.

FIG. 1 is a system diagram showing an outline of a waste heat recovery system according to an embodiment of the present invention. As shown in FIG. 1, the waste heat recovery system of the present invention mainly includes a reforming reactor 1, an expansion turbine 2, and a generator 3.
In the reforming reactor 1, carbon dioxide gas or water vapor is added to dimethyl ether, and the reforming reaction is performed, for example, by giving waste heat from a factory or the like. Dimethyl ether is supplied into the reforming reactor 1 through the pump 4 while mixing carbon dioxide or steam. The reforming reactor 1 is filled with a catalyst. In the reforming reactor 1, a catalytic reaction proceeds by waste heat, and synthesis gas or hydrogen gas is generated from dimethyl ether and carbon dioxide gas or steam.
The gas generated by the reforming reaction and expanded in volume is introduced into the expansion turbine 2 from the reforming reactor 1, and the expansion turbine 2 is used for power generation by rotating the turbine by the pressure energy (pressure) of the gas. To mechanical energy (power).
The generator 3 generates power by receiving mechanical energy (power) of the expansion turbine 2.
Furthermore, in FIG. 1, the synthesis gas or hydrogen gas that has passed through the expansion turbine 2 is introduced into a by-product gas line of a blast furnace or a caulk factory as usual, and is accumulated in the gas holder 5 as fuel energy. Used as fuel energy.
Thus, in the present invention, the pressure difference due to the volume expansion of the gas obtained by the reforming reaction is used. For example, one method is to generate electricity using an expansion turbine. Waste heat is recovered by the reforming reaction, and the turbine is rotated using the pressure energy of the gas generated by the reforming reaction to obtain energy such as electric power.

Here, the reforming reaction of dimethyl ether used in the waste heat recovery system of the present invention will be described in detail below.
In the reforming reactor 1, dimethyl ether and carbon dioxide or water (steam) react to mainly produce carbon monoxide, hydrogen and carbon dioxide. In the reaction formula, it is expressed as follows.
CH ₃ OCH ₃ + CO ₂ → 3CO + 3H ₂ (1)
CH ₃ OCH ₃ + H ₂ O → 2CO + 4H ₂ (2)
CH ₃ OCH ₃ + 3H ₂ O → 2CO ₂ + 6H ₂ (3)
It can be seen that in any reaction of the above formulas (1) to (3), the number of molecules increases and volume expansion occurs, and at the same time, volume expansion due to heating of the gas by waste heat is added here. In the present invention, the volume expansion characteristic of the reforming reaction, that is, the pressure difference before and after the reaction is effectively used as described above.
In the present invention, dimethyl ether may contain methanol and ethanol. When methanol and ethanol are contained in dimethyl ether, the reforming reaction of methanol and ethanol in dimethyl ether proceeds simultaneously with dimethyl ether according to the following reaction formula to generate gas. And the gas produced | generated by the reforming reaction of methanol and ethanol is utilized as energy similarly to the gas produced | generated by the reforming reaction of dimethyl ether.
Reforming reaction of methanol CH ₃ OH + H ₂ O → CO ₂ + 3H ₂
CH ₃ OH → CO + 2H ₂
Reforming reaction of ethanol C ₂ H ₅ OH + CO ₂ → 3CO + 3H ₂
C ₂ H ₅ OH + H ₂ O → 2CO + 4H ₂
C ₂ H ₅ OH + 3H ₂ O → 2CO ₂ + 6H ₂
In addition, when the waste heat used for the waste heat recovery system of this invention is less than 600 degreeC, in order to produce the said reforming reaction, it is preferable to carry out using a catalyst.

Any catalyst can be used as the catalyst charged in the reforming reactor 1 as long as it undergoes a reforming reaction, but generally used copper-based catalyst, iron-based catalyst, cobalt-based catalyst, palladium-based catalyst. Etc. are desirable.
The copper-based catalyst is made of metallic copper, copper oxide or a mixture thereof, and the copper oxide is cuprous oxide (Cu ₂ O), cupric oxide (CuO) or a mixture thereof. .
The iron-based catalyst is made of metallic iron, iron oxide, or a mixture thereof, and the iron oxide is ferrous oxide (FeO), ferric oxide (Fe ₂ O ₃ ), or a mixture thereof.
The cobalt-based catalyst is made of cobalt metal, cobalt oxide or a mixture thereof, and the cobalt oxide is cobalt oxide (CoO), cobalt oxide (Co ₂ O ₃ ) or a mixture thereof. .
The copper-based catalyst, iron-based catalyst or cobalt-based catalyst is generally used by being supported on a catalyst carrier such as alumina, silica gel, silica / alumina, or zeolite.
The palladium-based catalyst is obtained by supporting palladium on a basic metal oxide such as an alkali metal oxide, an alkaline earth metal oxide, or a rare earth element oxide.

  Carbon dioxide or water (steam) is introduced into the reforming reactor 2 filled with these catalysts together with dimethyl ether. The composition of the introduced dimethyl ether and carbon dioxide or water (steam) is preferably 1: 1 to 1:10 (molar ratio) of dimethyl ether: carbon dioxide or water (steam). If the molar ratio of carbon dioxide or water (steam) is too small compared to dimethyl ether, the reaction rate of the reforming reaction will decrease and the reaction of methane formation will become significant, so the endotherm will decrease and waste heat will Recovery efficiency is relatively reduced. On the other hand, when the molar ratio of carbon dioxide or water (steam) is larger than that of dimethyl ether, there is an advantage that the reforming reaction can be performed at a lower temperature. Not economical.

The pressure of dimethyl ether and carbon dioxide or water (steam) introduced into the reforming reactor 1 is preferably about 0.1 to 1 MPa in terms of gauge pressure. If the pressure is too low, the gas pressure after the reforming reaction is too low. On the other hand, when the pressure is too high, the reaction rate of the reforming reaction decreases.
As an example, FIG. 4 shows the relationship between the pressure (absolute pressure) and the carbon dioxide / dimethyl ether ratio in the reaction between dimethyl ether and carbon dioxide and the temperature at which the equilibrium reaction rate is 95%. FIG. 4 shows that the temperature at which the equilibrium reaction rate becomes 95% increases as the reaction pressure increases. That is, if the reaction temperature is the same, the reaction rate of the reforming reaction decreases as the reaction pressure increases. On the other hand, it can be seen that this temperature shifts to a lower temperature side when the carbon dioxide / dimethyl ether ratio increases.

The feed rate of dimethyl ether is introduced into the reforming reactor 1 and carbon dioxide or water (steam), in space velocity is the gas feed rate per volume of catalyst ^{(m 3) (Nm 3 /} hr), 1000~5000m 3 / M ³ · hr is desirable. If the space velocity is smaller than this, the volume of the reactor becomes large, which is not economical. On the other hand, when the space velocity is larger than this, the reaction rate of the reforming reaction decreases.

  By introducing factory waste heat (preferably less than 600 ° C.) as a heat source into the reforming reactor 1, waste heat can be effectively used. The temperature in the reforming reactor is preferably 250 to 500 ° C. When the temperature is lower than this, the rate of the reforming reaction is reduced, and when the temperature is higher than this, the catalyst may be deteriorated. The waste heat introduced to cause such a reforming reaction is preferably 300 ° C. or higher.

  The method for introducing dimethyl ether and carbon dioxide or water (steam) introduced into the reforming reactor 1 is not particularly limited. As shown in FIG. 1, the water and dimethyl ether may be mixed with water before being pressurized with the pump and pressurized with the pump 4 and supplied to the reforming reactor 1, or dimethyl ether and water may be respectively supplied. After being pressurized by the pump, the mixture may be mixed and supplied to the reforming reactor 1. Alternatively, steam or carbon dioxide gas may be pressurized with a compressor, mixed with dimethyl ether pressurized with a pump 4, and supplied to the reforming reactor 1.

Next, a second embodiment of the present invention will be described.
FIG. 2 is a system diagram showing an outline of the waste heat recovery system according to the second embodiment of the present invention. In addition to the system shown in FIG. 1, one or more of dimethyl ether, carbon dioxide, and water vapor used as raw materials are heated by waste heat before the reforming reaction. This heating is preferably performed to a temperature necessary for the reforming reaction. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
Usually, factory waste heat that has not been used for the reforming reaction is discharged from the reforming reactor 1 to the outside of the system. However, in FIG. 2, the waste heat that has not been used for the reforming reaction is used by the heat exchanger 6 to heat any one or more of dimethyl ether, carbon dioxide gas, and water vapor used as raw materials.

Next, a third embodiment of the present invention will be described.
FIG. 5 is a system diagram showing an outline of the waste heat recovery system according to the third embodiment of the present invention. In addition to the system shown in Fig. 1, dimethyl ether used as a raw material is produced as a raw material by using gas (coke oven gas, converter gas, blast furnace gas, etc.) produced as a by-product at the steelworks, and the produced dimethyl ether is liquefied and stored. This is a case where supply is possible when necessary for the reforming reaction. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
In FIG. 5, converter gas, blast furnace gas, coke oven gas, and the like are mixed at a predetermined mixing ratio and introduced into the dimethyl ether production apparatus 9. Next, the dimethyl ether produced in the production device 9 is liquefied and stored in the storage device 10 and supplied into the reforming reactor 1 via the pump 4 as necessary.
In FIG. 5, converter gas, blast furnace gas, coke oven gas, and the like are mixed as they are and introduced into the dimethyl ether production apparatus 9, but an apparatus for separating and purifying these gases separately, for example, PSA (pressure swing adsorption). Carbon dioxide, nitrogen, methane, or the like may be separated and reduced by an apparatus or the like, and introduced into the dimethyl ether production apparatus 9 as a gas in which the concentrations of hydrogen and carbon monoxide, which are raw materials for producing dimethyl ether, are increased. In this separation and purification, the converter gas, the blast furnace gas, and the coke oven gas may be separately separated and purified, or two or more gases may be mixed and separated and purified in advance.
Further, the synthesis gas or hydrogen gas generated in the reforming reactor 1 is divided into a fuel gas and an unreacted liquid component by the gas-liquid separator 11, and the liquid component is returned to the storage device 10. By introducing the fuel gas separated by the gas-liquid separator 7 into the expansion turbine 2 in a pressurized state, the input amount of energy necessary for boosting the fuel gas can be reduced.
In the third embodiment, dimethyl ether is used as a liquefiable fuel. However, the dimethyl ether may contain other components, and the present invention is not limited to this. At steelworks, coke ovens, blast furnaces, converters, and other equipment generate gas called by-product gas, and in addition to components that can be used as fuels such as hydrogen, carbon monoxide, and methane, nitrogen, carbon dioxide Contains. It is also possible to synthesize and store a fuel that can be stored as a liquid obtained by converting methanol, dimethyl ether, or ethanol into a polymer, using carbon monoxide or hydrogen in the byproduct gas as a raw material. For example, it can be used as a backup fuel for the reforming reaction when the gas is insufficient.

FIG. 6 shows the production of dimethyl ether, which is used as a raw material for the reforming reaction, by a by-product gas (coke oven gas, converter gas, blast furnace gas, etc., hereinafter sometimes referred to as by-product gas). It is a figure which shows the outline of the system which liquefies and stores the obtained dimethyl ether. According to FIG. 6, after the converter gas, the blast furnace gas, and the coke oven gas are mixed at a predetermined mixing ratio, dust, tar mist, and the like are removed by two filters 12 that are used alternately, and then desulfurized. Introduced into device 13. The gas desulfurized by the desulfurization apparatus 13 is pressurized by the compressor 14 and introduced into the dimethyl ether production apparatus 9.
In the dimethyl ether production apparatus 9, hydrogen or carbon monoxide in the by-product gas is introduced into the reaction apparatus to produce dimethyl ether (including the case where methanol and ethanol are mixed). These production methods can be applied to any conventionally known method, but as an example, there is a method utilizing a catalytic reaction, which requires high pressure and high temperature as reaction conditions, but is a method that is industrially easy to apply. is there.
The gas discharged from the dimethyl ether production apparatus 9 is depressurized by the compressor 14 that can use the energy at the time of depressurization, and is introduced into the condenser / gas-liquid separator 15 to be separated into dimethyl ether and other gas components. The separated dimethyl ether is sent to the storage device 10. On the other hand, other gas components are returned to the byproduct gas line.
In this way, it is possible to manufacture and store a liquefiable and storable fuel containing dimethyl ether from the by-product gas of the steelworks and supply it as necessary.

Next, a fourth embodiment of the present invention will be described.
FIG. 7 is a system diagram showing an outline of the waste heat recovery system according to the fourth embodiment of the present invention. In addition to the system shown in FIG. 5, any one or more of dimethyl ether, carbon dioxide gas, and water vapor used as a raw material is heated by waste heat. This heating is preferably performed to a temperature required for the reforming reaction. In FIG. 7, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted.
Usually, factory waste heat that has not been used for the reforming reaction is discharged out of the system from the reforming reactor. However, in FIG. 7, the waste heat that has not been used for the reforming reaction is used by the heat exchanger 6 to heat any one or more of dimethyl ether, carbon dioxide gas, and water vapor used as a raw material.
In the present invention, a catalyst may be used for the reforming reaction as described above and a waste heat of less than 600 ° C. may be used, or a system using a waste heat of 600 ° C. or more may be used. Moreover, it is preferable that this waste heat is exhaust heat of a steel mill. This is because a large amount of energy can be recovered as described above. Furthermore, when waste heat of 600 ° C. or higher is used, the reforming reaction proceeds with only heat without using an expensive catalyst, which is preferable. Any heat source may be used as long as the heat source is 600 ° C. or higher. For example, exhaust heat from a coke dry fire extinguishing facility can be used.

Next, a fifth embodiment of the present invention will be described.
FIG. 8 is a fifth embodiment of the present invention for recovering waste heat of 600 ° C. or higher. In the system of FIG. 1, a system diagram in the case where the reforming reaction is performed using the exhaust heat of the coke dry digestion facility. It is. In FIG. 8, heat generated when coke is produced and cooled by a dry fire extinguishing equipment (CDQ) is used for the reforming reaction.
In FIG. 8, dimethyl ether stored in the storage device 10 is supplied by the pump 4, and water, which is another raw material for the reforming reaction, is supplied by the pump 4 ′, mixed in the middle, and introduced into the CDQ boiler 16. In the CDQ boiler 16, heat is supplied from a gas containing nitrogen as a main component which is heated to 800 to 900 ° C. by heat exchange with red hot coke in the CDQ chamber 17, so that the reforming reaction between dimethyl ether and water is performed by a catalyst. It progresses without it.
The hydrogen gas and synthesis gas generated by the reforming reaction are introduced into the expansion turbine 2 as in FIG. 1, and the expansion turbine 2 is mechanically used for power generation by rotating the turbine with the pressure energy of the gas. Convert to energy.
From the expansion turbine 2, water and gas generated by the reforming reaction come out, but these are separated by the gas-liquid separator 11. The water is recycled and the gas is sent to the gas holder 5 as fuel gas.
When the exhaust heat of CDQ is used as waste heat as in the fifth embodiment shown in FIG. 8, a liquefied fuel containing dimethyl ether is generated from a power generation facility that supplies only the water vapor of normal CDQ to the expansion turbine. The reforming reaction with water makes it possible to use much higher pressure energy, which is very effective because more pressure energy can be used. In this case, it is economical because it can be implemented by partial modification of the existing equipment without using a catalyst.
In addition, in FIG. 8, exhaust heat is general heat released by heating or cooling raw materials or products in a coke dry fire extinguishing facility, and includes waste heat. Further, for example, the waste heat used in FIG. 1 and the like is heat that is dissipated to the atmosphere without being reused.

  As described above, the present invention is characterized in that pressure energy, which has not been effectively used conventionally, is converted into mechanical energy and used effectively. Although FIG. 1 shows an example of an expansion turbine and a generator driven by the expansion turbine, it is used for power generation. However, it can also be used as auxiliary power for a compressor, a pump, etc. in addition to power generation.

  Since the waste heat recovery system of the present invention can efficiently recover waste heat energy, it is optimal as a waste heat recovery system in an ironworks. Moreover, it is possible to recover medium-low temperature waste heat of less than 600 ° C. and waste heat of 600 ° C. or more, and it can be expected to be used as an efficient energy recovery system.

It is a systematic diagram which shows the outline | summary of the waste heat recovery system by this invention. It is a systematic diagram which shows the outline | summary of the 2nd waste heat recovery system by this invention. It is a systematic diagram which shows the structure of the conventional waste heat recovery system. It is a figure which shows the relationship between the pressure in the reaction of dimethyl ether and carbon dioxide, the carbon dioxide / dimethyl ether ratio, and the temperature at which the equilibrium reaction rate is 95%. It is a systematic diagram which shows the outline | summary of the 3rd waste heat recovery system by this invention. 1 is a schematic diagram of a system for liquefying and storing dimethyl ether according to the present invention. It is a systematic diagram which shows the outline | summary of the 4th waste heat recovery system by this invention. It is a systematic diagram which shows the outline | summary of the 5th waste heat recovery system by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reforming reactor 2 Expansion turbine 3 Generator 4, 4 'pump 5 Gas holder 6 Heat exchanger 7 Pressure reducing valve 8 By-product gas line 9 Dimethyl ether production apparatus 10 Storage apparatus 11 Gas-liquid separator 12 Filter 13 Desulfurization apparatus 14 Compression Machine 15 Condenser / Gas-Liquid Separator 16 CDQ Boiler 17 CDQ Chamber

Claims (9)

A waste heat recovery system that recovers energy from waste heat by a reforming reaction of dimethyl ether,
Carbon dioxide gas or water vapor is added to the dimethyl ether, the reforming reaction is performed by the waste heat, and synthesis gas or hydrogen gas is obtained,
A waste heat recovery system that converts pressure energy of the obtained synthesis gas or hydrogen gas into mechanical energy or electrical energy.   The waste heat recovery system according to claim 1, wherein any one or more of the dimethyl ether, the carbon dioxide gas, and the water vapor used for the reforming reaction is heated by waste heat before the reforming reaction. . The waste heat recovery system according to claim 1 or 2, wherein the waste heat is less than 600 ° C, and the reforming reaction is performed using a catalyst.   The waste heat recovery system according to claim 1 or 2, wherein the waste heat is 600 ° C or higher, and the reforming reaction is performed without using a catalyst.   The waste heat recovery system according to any one of claims 1 to 4, wherein the waste heat is waste heat of a steel mill.   The waste heat according to any one of claims 1 to 5, wherein the pressure of the synthesis gas or the hydrogen gas obtained by the reforming reaction is converted into power, and the power is used for power generation. Collection system. A reforming reactor that reacts dimethyl ether with carbon dioxide gas or water vapor by waste heat to generate synthesis gas or hydrogen gas;
An expansion turbine that is rotated by pressure energy of the synthesis gas or the hydrogen gas generated in the reforming reactor;
A waste heat recovery apparatus having a converter for converting into mechanical energy or electrical energy by rotation of the expansion turbine.   The waste heat recovery apparatus according to claim 7, further comprising a heat exchanger that heats at least one of the dimethyl ether, the carbon dioxide gas, and the water vapor by waste heat before being introduced into the reforming reactor. . The waste heat recovery apparatus according to claim 7 or 8, wherein a boiler of a coke dry fire extinguishing equipment is used as the reforming reactor.

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