JP2007154857A - Cogeneration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cogeneration system wherein a cogeneration device is provided in a chemical plant. <P>SOLUTION: Steam generated from a chemical plant is supplied to a steam superheater of the cogeneration device. Superheated steam obtained from the steam superheater is used in the chemical plant. Further, by using the system, an ethylene oxide, ethylene glycol, an acrylic acid, a maleic anhydride, a phthalic anhydride, or a methacrylic acid are produced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cogeneration system used in a chemical plant.

  A cogeneration system or a cogeneration system is an energy saving system that generates power using fuel and effectively uses exhaust heat generated at that time for applications such as air conditioning, hot water supply, and steam.

  For example, in Patent Document 1, in a cogeneration system that generates both power and heat by providing an exhaust heat recovery boiler in a gas turbine, a gas engine, or a diesel engine, the demand for heat is reduced and surplus steam / surplus warm water is generated. In this case, a method for lowering the temperature of exhaust gas in water or steam is described in the exhaust heat recovery boiler.

Further, Patent Document 2 discloses a gas turbine including a compressor that compresses air, a combustor that combusts fuel, a turbine that is driven by combustion gas and drives the compressor, and water is supplied using turbine exhaust as a heat source. A combined steam injection gas turbine is described that includes an exhaust heat boiler that evaporates and superheats, and a steam turbine that is driven by superheated steam generated in the exhaust heat boiler, and injects the exhaust steam of the steam turbine into a combustor of the gas turbine. Yes. With this configuration, while maintaining the amount of steam injected into the combustor, the steam is heated to a higher temperature and pressure than before with a waste heat boiler, and the excess energy is recovered with a steam turbine, so that per unit steam volume is recovered. It is described that the amount of heat energy exchange increases.
JP 2003-120418 A JP 11-280493 A

  Generally, in a chemical factory having a reactor that is an exothermic reaction, steam is generated using the reaction heat and used as process steam in the factory, and the shortage is generated by a steam generation boiler or the like. Is going. However, in many cases, the balance of steam demand in factories is largely covered by waste heat steam obtained from reaction heat, as a result of promoting energy conservation. In this case, it is often difficult to introduce a general cogeneration system that uses exhaust heat by generating steam because there is no demand for steam in the factory.

  Conventionally, in chemical factories that use fuel and overheat steam or heat the heating medium, cogeneration is introduced in the form of reducing fuel by using exhaust heat from the cogeneration system, saving energy and global warming gas The purpose is to contribute to the reduction.

  Then, it aims at providing the cogeneration system which introduced the cogeneration apparatus in the chemical plant.

  It is another object of the present invention to provide a production method involving a reaction heat generation type oxidation reaction such as ethylene oxide and ethylene glycol, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid using a cogeneration system.

  The present invention relates to a cogeneration system characterized by supplying steam generated from a chemical plant to a steam superheater of a cogeneration apparatus and using the superheated steam obtained by the steam superheater in the chemical plant.

  The present invention also relates to a production method involving reaction heat generation type oxidation reaction such as ethylene oxide and ethylene glycol, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid using the system.

  According to the present invention, energy saving can be achieved, and emission of global warming gas can be suppressed.

  In addition, a cogeneration system can be introduced at factories where there is no demand for steam.

  The cogeneration system of the present invention is characterized in that steam generated from a chemical plant is supplied to a steam superheater of a cogeneration apparatus, and superheated steam obtained by the steam superheater is used in the chemical plant.

  The chemical plant that can be used in the present invention is not particularly limited as long as it is a plant that utilizes a chemical reaction. For example, it is preferable that there is a certain demand for electric power and a demand for heat other than steam. Specific examples of the chemical plant include a production apparatus such as ethylene oxide and ethylene glycol, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid.

  The cogeneration apparatus that can be used in the present invention is not particularly limited as long as it generates power using fuel and can use waste heat generated at that time. For example, a gas engine, a diesel engine, a gas turbine An apparatus provided with a steam heater that can be used as a driving source for a generator or a driving source for a generator and simultaneously recovers the heat of exhaust gas.

  The superheated steam used in the present invention can be used without limitation as long as it is superheated steam.

  Further, the cogeneration system of the present invention is provided with a heat medium used in the chemical plant, a combustion air used in the combustion furnace used in the chemical plant, or both, in addition to the above-described steam overheating, respectively. It is preferable to supply the heated medium and use the heated medium in the chemical plant.

  Examples of the heat medium that can be used in the present invention include steam, molten salt such as Dowsum (a product of heat transfer medium manufactured by Dow) or nighter. Further, the combustion air of the combustion furnace that can be used in the present invention can be exemplified by the combustion air of facilities that burn and heat fuel such as a steam boiler, a heat medium heating furnace, and a waste incinerator in the chemical plant. .

  The cogeneration system of the present invention further directs the superheated steam to a steam turbine and uses it as a power source for a pump or booster of the plant, and uses steam at the outlet of the steam turbine as process steam of the plant. Is preferred.

  In addition, a method for producing ethylene oxide and ethylene glycol (EOG), acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid using the cogeneration system of the present invention can be provided. Here, ethylene oxide (EO) and ethylene glycol (EG) will be described as representative examples. Here, a conventionally well-known method can be employ | adopted for the manufacturing method of EO and EG.

  An outline of the manufacturing process of EO will be described below.

FIG. 1 is a system diagram showing an example of an EO process. (For example, refer to JP 2001-187788 A and JP 2001-316308 A)
In FIG. 1A, an ethylene source gas containing ethylene, oxygen and the like is introduced into a shell-and-tube reactor 107 through a blower 104 and a heat exchanger 105, where it is brought into contact with a silver-containing catalyst to produce ethylene. Partially oxidize to EO. The reaction gas is introduced into the EO absorption tower 108 via the heat exchanger 105, and the generated EO is absorbed and recovered. A part of the reaction gas from the EO absorption tower 108 is circulated to the reactor 107. Then, the remainder is introduced into the carbon dioxide absorption tower 109 through the blower 104, and after absorbing and separating the carbon dioxide, it is circulated to the reactor 107. As described above, the reaction gas circulated from the EO absorption tower 108 and the carbon dioxide absorption tower 109 is replenished with ethylene, methane, and the like to adjust the gas composition, and then introduced into the reactor 107 as an ethylene source gas and continuously oxidized. Perform the reaction.

  FIG. 1B illustrates the process of separating oxygen from air. In FIG. 1B, air is sent to the air compressor 181 for compression, the compressed air is sent to the air separation device 183 to separate oxygen, and the separated oxygen is compressed by the oxygen compressor 185, and then EO. Send to EO process as raw material for production.

  FIG. 2 is a flow sheet showing an example of an EG manufacturing process.

In FIG. 2, the obtained EO together with water is sent to the hydrolysis reactor 291 to be reacted. The obtained EG aqueous solution is sent to the concentration step 292 and then to the dehydration step 293 to evaporate the moisture, and then sent to the mono-EG distillation column 294 to separate mono-EG (MEG) from the top of the column. The bottom liquid of the mono-EG distillation tower is sent to the di-EG distillation tower 295, di-EG (DEG) is separated from the top of the tower, and the bottom liquid is sent to the tri-EG distillation tower 296, and then the -Separate EG (TEG). (For example, see JP 2001-316308 A)
Thus, when producing EG from ethylene via EO, operations such as EO rectification operation, by-product EG concentration dehydration operation, and rectification of mono-, di-, tri-EG, etc. are required. A large amount of heat source is consumed. A large amount of power is required, such as a compressor for taking in air to obtain oxygen as a raw material for EO, a compressor for circulating reaction gas, an oxygen compressor, and other process pumps.

  Next, the main steam and energy flows in the EOG process will be described.

  FIG. 3 is a drawing showing an example of the steam flow of the cogeneration system of the present invention. In FIG. 3, since a large amount of reaction heat is generated during the oxidation reaction between ethylene and oxygen in the EO reactor 307, saturated vapor is obtained in the gas-liquid separation tank 308 by effectively using this reaction heat.

  This saturated steam is divided into two parts, a first saturated steam and a second saturated steam. The first saturated steam is sent to the steam heating furnace 311 via the line 310, where the fuel is combusted with the combustion air and heated, and then sent to the first steam turbine 313 via the line 312. The first steam turbine 313 has a function of compressing (circulating) reaction gas introduced into the EO reactor 307. The steam that exits the first steam turbine 313 is used as a first process steam for a process heat source via a line 314. On the other hand, the second saturated steam is sent via a line 320 to a steam superheater 321 provided in the cogeneration apparatus, where the steam is converted into superheated steam. The obtained superheated steam is sent to the second steam turbine 323 via the line 322. The second steam turbine 323 has a function of compressing air in order to obtain oxygen which is one of EO raw materials. Specifically, the air is compressed by an air compressor 324 driven by the second steam turbine. Compressed air is sent to air separation device 326 via line 325. Oxygen separated by the air separation device 326 is sent via a line 327 to an oxygen compressor 329 that is operated by a motor 328. The compressed oxygen is supplied to the EO reactor 307 together with ethylene and a reaction gas as a raw material for producing EO. The steam exiting the second steam turbine 323 is utilized as a second process steam for a process heat source via a line 330. Although the steam sent to the second steam turbine is heated in a cogeneration steam superheated furnace, it is not limited to either the first steam turbine or the second steam turbine.

  The cogeneration apparatus has the following configuration. Air is sent through line 350 to air compressor 351 where it is compressed. The resulting compressed air is sent to combustor 353 via line 352. On the other hand, the fuel is sent to the combustor 353 via the line 354 and burned there. The combustion exhaust gas is sent to the gas turbine 356 via the line 355. Electric power generated by the generator 357 driven by the gas turbine 356 is transmitted via a line 358. The flue gas exiting the gas turbine 356 is sent to the steam superheater 321 via the line 359. The combustion exhaust gas that has exited the steam superheater 321 is sent to the heat medium heater 361 via the line 360. The exhaust from the heat medium heater 361 is discharged out of the system through a line. Here, in the above description, the order of arrangement of the steam superheater 321 and the heat medium superheater 361 is not specified.

  On the other hand, the exhaust heat of the exhaust gas from the steam superheater 321 of the cogeneration apparatus is recovered using the heat medium heater 361. If necessary, the heat medium is sent to the heat medium heating furnace 371 via the line 370 and heated there. The heat medium is sent via line 372 to the EG process 373 where it is utilized as a heat source. The heat medium leaving the EG process 373 is sent to the heat medium heater 361 via the line 374.

  As described above, the main energy that can be used in the present invention is steam generated from the reactor of EO, electric power generated by in-house power generation obtained from the cogeneration apparatus, and heat of the combustion exhaust gas generated from the gas turbine of the cogeneration apparatus. .

  On the other hand, the energy is used as the EO raw material air compressor, the compressor for circulating the EO reaction gas, the process pump, the heating of the EG distillation tower, the fuel burned in the combustion furnace, etc. It is.

  The electric power generated by the in-house power generation is supplied to an EO raw material air compressor, an EO raw material oxygen compressor, and a process pump. The steam generated from the EO reactor uses the heat of the combustion exhaust gas generated from the gas turbine of the cogeneration apparatus, further increases the utility value as superheated steam, and is used for the second steam turbine of EO. Further, the heat medium is heated using the heat of the combustion exhaust gas of the gas turbine, and is used as a heating source such as an EG distillation tower. Alternatively, the heat of combustion exhaust gas is used to preheat the combustion air in the combustion furnace to reduce the combustion fuel in the combustion furnace. Alternatively, both methods utilize the heat of the gas turbine flue gas.

  The energy thus obtained can be consumed in a balanced manner.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to an Example.

Example 1
The cogeneration system of the present invention will be described with reference to the drawings.

  In FIG. 3, the cogeneration system is divided into an EO process, a cogeneration apparatus, and an EG process.

(EO process)
The heat of oxidation reaction generated in the EO reactor 307 is removed by boiling heat transfer through hot water circulation. The hot water is guided to the gas-liquid separation tank 308, where it is converted to saturated steam. The saturated steam is divided into two, one being led to the steam heating furnace 311 via the line 310, where it further superheats. Superheated steam is sent via line 312 to the first steam turbine 313 which is the power source for the EOG process. Steam output from the first steam turbine 313 is used as a process heat source via a line 314. The remaining saturated steam is led to the steam superheater 321 of the cogeneration apparatus via the line 320, where it is converted to superheated steam. Superheated steam is sent via line 322 to a second steam turbine 323 that serves as the power source for the EOG process. The steam emitted from the second steam turbine 323 is used as a process heat source via the line 330. A motor 331 is additionally provided because the power using the steam turbine as a driving source is insufficient.

(Cogeneration equipment)
The cogeneration apparatus includes a combustor 353, an air compressor 351, a gas turbine 356, a power generator 357, and the like. With this configuration, power generation by the power generator 357 and waste heat generated at that time are used. The combustion exhaust gas exiting the gas turbine is discharged through a steam heater 321, a denitration device (not shown), and a heat medium heater 361 as necessary.

(EG process)
The heat medium is led to the heat medium heater 361 via the line 374, where the heat medium is heated. The heated heat medium is led to the EG process 373 as a process heat source via the line 372. The heat medium discharged from the EG process is sent to the heat medium heater 361 via the line 374.

(Comparative Example 1)
A conventional steam flow will be described with reference to the drawings.

  FIG. 4 is a diagram showing a steam flow of the conventional EOG technology. In FIG. 4, the steam flow will be described in order by dividing it into an EO process and an EG process.

(EO process)
The heat of oxidation reaction generated in the EO reactor 407 is removed by boiling heat transfer through hot water circulation. The hot water is led to the gas-liquid separation layer 408, where it is saturated steam. The saturated steam is divided into two and one is led to the first steam heating furnace 411 via the line 410 and further superheated there. Superheated steam or superheated steam is sent via line 412 to a first steam turbine 413 that serves as a power source for the EOG process. The steam emitted from the first steam turbine 413 is used as a process heat source of a process (not shown) via a line 414. The remaining saturated steam is led via line 441 to the second steam furnace 442 where it is further superheated. Superheated steam is sent via line 422 to a second steam turbine 423 that serves as the power source for the EOG process. A motor 431 is additionally provided because the power using the steam turbine as a driving source is insufficient. Specifically, the air is compressed by an air compressor 424 driven by the second steam turbine. The compressed air is sent to the air separation device 426 via line 425. The oxygen separated by the air separation device 426 is sent to an oxygen compressor 429 that is moved by a motor 431 via a line 427. The compressed oxygen is supplied to the EO reactor 407 together with ethylene and the reaction gas as a raw material for producing EO. Steam from the second steam turbine is used as a process heat source for a process (not shown) via line 440.

(EG process)
The heat medium is guided to the heat medium heating furnace 471 via the line 470, and fuel is added to heat the heat medium. The heated heat medium is directed to the EG process 473 via line 472. The heat medium after being used as a heat source in the EG process 473 is sent to the heat medium heating furnace 471 via the line 470.

(Energy balance)
Table 1 shows an example of operating conditions before and after the introduction of the cogeneration system.

  Where (cogeneration system overall efficiency) = {(heat conversion amount of gas turbine power generation amount) + (heat amount received by steam in the steam superheated furnace of the cogeneration unit) + (heat in the heating medium heating furnace of the cogeneration unit) The amount of heat received by the medium)} / (heat conversion amount of gas turbine fuel consumption). The furnace efficiency of the heating furnaces 442 and 471 is 90%.

  Under the operating conditions shown in Table 1, the fuel can be operated with zero fuel consumption in the heating furnace 442 and the heating furnace 471 in FIG. 4 before and after introduction. However, when there is a change in steam conditions, a change in heat medium conditions, or a change in operating conditions, it can be dealt with by performing a combined operation with a conventional heating furnace and adding an insufficient heat source. In this case, it is natural that the fuel used in the heating furnace (442 or 471) can be reduced by the amount of heat recovered in the heating furnace of the cogeneration device, compared to before the introduction.

  Before the introduction, 6960 kW of gas turbine power generation after the introduction was covered by purchased power.

  The electric power generated by the gas turbine is consumed as the electric power of the motor 431 that supplements the insufficient power in the air compressor 424, the electric power of the motor 428 of the oxygen compressor 429, and the electric power of the process pump used in the EO process and EG process. .

  Electricity and fuel were converted into crude oil equivalents and compared as total energy consumption before and after introduction. As the crude oil conversion coefficient at that time, electric power: 0.254 L / kWh and fuel: 0.0258 L / MJ were used.

  (Total energy consumption before introduction) = (purchased power: 6960 kW) × 0.254 + (fuel: 27269 + 10152 MJ) × 0.0258 = 2733 L / h.

  (Total energy consumption after introduction) = (Gas turbine fuel: 76727) × 0.0258 = 1980 L / h.

  As an introduction effect of this system, energy saving of 27.6% in terms of crude oil equivalent was achieved.

  The overall efficiency of this cogeneration system was 76.6%, which was the same performance efficiency as a general steam generation type cogeneration system in the scale of this gas turbine.

Carbon dioxide emissions reduction effect Carbon dioxide emissions before and after introduction (carbon equivalent) were compared. For calculation of the carbon dioxide emission, electric power: 0.103 kg-C / kWh and fuel: 0.0130 kg-C / MJ were used. As a result, the reduction rate before and after introduction was 17.3%.

It is a systematic diagram which shows an example of EO process. It is a flow sheet which shows an example of the manufacturing process of EG. It is drawing which shows an example of the steam flow of the cogeneration system of this invention. It is drawing which shows the steam flow of the conventional EOG technique.

Explanation of symbols

104: Blower
105: heat exchanger,
107: reactor,
108: EO absorption tower,
109: Carbon dioxide absorption tower.

Claims (5)

  A cogeneration system characterized in that steam generated from a chemical plant is supplied to a steam superheater of a cogeneration apparatus, and the superheated steam obtained by the steam superheater is used in the chemical plant.   2. The system according to claim 1, wherein the heat medium used in the chemical plant, the combustion air of the combustion furnace used in the chemical plant, or both are supplied to a heater provided in a cogeneration apparatus and used in the chemical plant. .   The superheated steam is guided to a steam turbine, used as a power source for a pump or booster of the plant, or as a drive source for a generator, and further, steam at the outlet of the steam turbine is used as a process steam of the plant. 2. The system according to 2.   The system according to any one of claims 1 to 3, wherein the chemical plant is a manufacturing plant involving a reaction heat generation type oxidation reaction.   A method for producing ethylene oxide and ethylene glycol, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid with a reaction heat generation type oxidation reaction using the system according to any one of claims 1 to 4.

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