JP2012072734A - Cogeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cogeneration system introduced with a cogeneration device, in a chemical plant.SOLUTION: The cogeneration system is characterized: by introducing the cogeneration system, whcih utilizes waste heat generated with power generation, to the chemical plant; and by utilizing superheat vapor, which is obtained by utilizing the waste heat and a refrigerant, in the chemical plant. Also, a method is provided for producing an ethylene oxide, an acrylic acid, maleic anhydride, phtalic anhydride, or a methacrylic acid.

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.
Patent Document 2 discloses a gas turbine including a compressor that compresses air, a combustor that burns fuel, a turbine that is driven by combustion gas and drives the compressor, and water is evaporated using turbine exhaust as a heat source. There is described a combined steam injection gas turbine that includes an exhaust heat boiler that 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. With this configuration, while maintaining the amount of water vapor injected into the combustor, the steam is superheated to a higher temperature and pressure with a waste heat boiler, and the excess energy is recovered with a steam turbine. It is described that the exchange amount of heat energy per unit increases.

  Patent Document 3 describes 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.

  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. ing. However, since the steam demand balance in factories is mostly covered by exhaust heat steam obtained from reaction heat by promoting energy conservation so far, general cogeneration that uses exhaust heat by generating steam The introduction of the system is often difficult because there is no steam demand in the factory. Even when it was introduced, exhaust heat utilization at the end was insufficient and there was room for review. Furthermore, since the price of crude oil has increased in recent years, fuel has soared and running costs have increased, so it is desirable to reduce the amount of fuel used. In addition, not only to effectively use limited resources, but also to reduce carbon dioxide (CO2) emissions in order to reduce the impact of global warming is strongly demanded.

JP 2003-120418 A JP 11-280493 A JP 2007-154857 A

  Conventionally, in a chemical factory that uses fuel to superheat steam, heat a heat medium, or cools a refrigerant or process fluid using electric power, fuel and electric power by using waste heat from a cogeneration system It aims to contribute to the reduction of CO2, which is a global warming gas, by introducing cogeneration in the form of reducing CO2 and saving energy.

  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 reaction heat generation type oxidation reaction such as ethylene oxide, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid using a cogeneration system.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have generated power using fuel as an energy source and introduced a cogeneration system that uses exhaust heat generated by power generation into a chemical plant. In addition, superheated steam and a cooled heat transfer medium (hereinafter sometimes referred to as “refrigerant”) are generated using the exhaust heat, and the superheated steam and refrigerant are used in a chemical plant to save energy. In addition, the present inventors have found that the amount of CO2 emission can be greatly reduced as compared with the past, and completed the present invention.

  In other words, the present invention (1) obtains superheated steam by using a part of the exhaust heat generated from the cogeneration device for superheating the steam generated from the chemical plant, and further utilizes at least a part of the remaining exhaust heat. A cogeneration system is provided that generates a refrigerant and uses the obtained superheated steam and refrigerant in a chemical plant.

  According to a preferred embodiment of the present invention, as a preferred embodiment, (2) steam and / or hot water is obtained by using at least a part of the remaining exhaust heat in a steam or hot water generator provided in a cogeneration apparatus, and further obtained. There is also provided a cogeneration system characterized in that a refrigerant is generated using the generated steam or hot water, and at least one of the obtained steam, hot water and refrigerant is used in the chemical plant.

In another preferred embodiment of the present invention, (3) the superheated steam is led to a steam turbine and used as a power source for the pump or booster of the plant or a power source for a generator. There is also provided a cogeneration system characterized by using steam as process steam of the plant. Further, the present invention provides ethylene oxide with a reaction heat generation type oxidation reaction using any one of the systems, A process for producing acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid is also provided.

  According to the present invention, the superheated steam and the refrigerant can be obtained by using the exhaust heat generated from the cogeneration apparatus for superheating the steam generated from the chemical plant and further for generating the refrigerant. Since there are many users (demands) in the chemical plant using both the superheated steam and the refrigerant, the exhaust heat can be used efficiently, so that energy saving can be achieved by reducing fuel and power. In addition, in a chemical plant, a refrigerator has been operated by using electricity as a power source to generate refrigerant, so that the amount of electricity used can be greatly reduced due to a decrease in the frequency of use of the refrigerator. As a result, CO2 emission can be significantly suppressed. Furthermore, the cogeneration system of the present invention can be installed in factories where there is much cold demand compared to steam demand.

It is a systematic diagram which shows an example of EO process. It is drawing which shows an example of the flow of the vapor | steam of the cogeneration system of this invention, and a refrigerant | coolant. It is drawing which shows the flow of the vapor | steam of the conventional EO process, and a refrigerant | coolant.

  The cogeneration system of the present invention generates power using fuel as an energy source, generates superheated steam and refrigerant using exhaust heat generated by power generation, and uses the superheated steam and refrigerant in a chemical plant. Features.

  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 cold energy. Specific examples of the chemical plant include a production apparatus for ethylene oxide, 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 is an apparatus that generates power using fuel and can use exhaust heat generated at that time. For example, a gas engine, a diesel engine, a gas turbine Examples of the apparatus include an absorption refrigeration machine and a steam heater that can be used as a driving source for a generator or a driving source for a generator, and at the same time, recover heat of exhaust gas as cold heat and a heat source.

  The superheated steam used in the present invention can be used without limitation as long as it is superheated steam. Moreover, the refrigerant | coolant of this invention can be utilized without a restriction | limiting, if it is a refrigerant | coolant obtained using the exhaust heat generated from a cogeneration apparatus. The apparatus for generating cold using the exhaust heat of the present invention is not particularly limited, and examples thereof include a steam input absorption refrigerator, a hot water input absorption refrigerator, an exhaust gas direct input absorption refrigerator, and the like. Examples of the medium for transferring the generated cold heat include cold water and brine.

  The refrigerant of the present invention is preferably used in the chemical plant or cogeneration apparatus. For example, if it is an ethylene oxide (EO) production plant and a cogeneration system, it can be used as a refrigerant for cooling absorption liquids, condensers for diffusion towers, dehydration towers and light separation towers, cooling products EO, and cooling intake air for cogeneration systems. it can.

  In the cogeneration system of the present invention, steam and / or hot water is obtained by using at least a part of the remaining exhaust heat in a steam or hot water generator provided in the cogeneration apparatus, and the steam or It is preferable to generate a refrigerant using hot water and use at least one of the obtained steam, hot water and refrigerant 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.

  Moreover, the manufacturing method of EO, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid using the cogeneration system of this invention can be provided. Here, EO will be described as a representative example. Here, a conventionally well-known method can be employ | adopted for the manufacturing method of EO.

  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, JP 2001-316308 A, and JP 62-103072 A).
In FIG. 1A, a raw material gas containing ethylene, oxygen and the like is introduced into a shell-and-tube reactor 103 through a blower 101 and a heat exchanger 102, where it is brought into contact with a silver-containing catalyst to convert ethylene into EO. Partially oxidize. The reaction gas is introduced into the EO absorption tower 104 through the heat exchanger 102, and the generated EO is absorbed and recovered. A part of the reaction gas from the EO absorption tower 104 is circulated to the reactor 103. The remainder is introduced into the carbon dioxide absorption tower 105 through the blower 101, and after absorbing and separating the carbon dioxide, it is circulated to the reactor 103. As described above, the reaction gas circulated from the EO absorption tower 104 and the carbon dioxide absorption tower 105 is replenished with ethylene, methane, etc. to adjust the gas composition, and then introduced into the reactor 103 as a raw material gas to continuously undergo oxidation reaction. I do.

  In FIG. 1 (B), the bottom liquid of the EO absorption tower 106 is sent to the heat exchanger 107, heat-exchanged with the bottom liquid of the stripping tower, supplied to the upper part of the EO stripping tower 108, and EO contained in the absorption liquid is supplied. Dissipate. From the bottom of the EO diffusion tower 108, the tower bottom liquid not containing EO is heat-exchanged with the tower bottom liquid of the EO absorption tower by the heat exchanger 107, cooled by the cooler 109, and introduced into the absorption tower 106. The diffused vapor diffused from the top of the EO stripping tower 108 is sent to the condenser 110, the condensed liquid is refluxed to the top of the EO stripping tower 108, and the uncondensed steam is supplied to the dehydrating tower 111. Vapor containing ethylene oxide is sent to the condenser 112 from the top of the dehydrating tower 111, part of the condensate is refluxed to the top of the tower, and the rest is supplied to the light component stripping tower 113. The uncondensed vapor from the condenser 112 was supplied to an EO reabsorption tower (not shown). The EO vapor containing the light component gas is sent to the condenser 114 from the top of the light component diffusion tower 113, the condensate is refluxed to the condenser 112, and the uncondensed vapor is supplied to the EO reabsorption tower (not shown). . The bottom liquid of the light separation tower 113 is supplied to the rectification tower 115. EO vapor is sent to the condenser 116 from the top of the rectifying column 115, and EO is liquefied. A part of the EO is supplied as a reflux liquid to the top of the rectifying column, and the other part is extracted as an EO product.

Next, main steam and energy flows in the EO process will be described.
Since the cogeneration system of the present invention is divided into an EO process portion and a cogeneration device portion, each will be described in turn.

  FIG. 2 is a drawing showing an example of the steam flow in the EO process of the cogeneration system of the present invention. In FIG. 2, since a large amount of reaction heat is generated during the oxidation reaction between ethylene and oxygen in the EO reactor 201, the oxidation reaction heat generated in the EO reactor 201 is removed by boiling heat transfer by hot water circulation. I do. In order to effectively use this heat of reaction, the hot water is guided to the gas-liquid separation tank 202, and saturated vapor is obtained in the gas-liquid separation tank 202.

  This saturated steam is guided to the steam superheater 204 of the cogeneration apparatus via the line 203, where it is converted into superheated steam. The obtained superheated steam is sent via line 205 to a steam turbine 206 that serves as a power source for the EO process. Steam from the steam turbine 206 is used as a process heat source via a line 207.

  FIG. 2 is also a drawing showing an example of the flow of electricity, steam or cold heat in the cogeneration apparatus portion of the cogeneration system of the present invention.

  The cogeneration apparatus includes a combustor 208, an air compressor 209, a gas turbine 210, a generator 211, and the like. With this configuration, fuel is burned using an energy source, and power is generated by the generator 211, and is generated along with power generation. Use waste heat. First, air is sent via line 212 to air compressor 209 where it is compressed. The obtained compressed air is sent to the combustor 208. On the other hand, the fuel is sent to the combustor 208 via the line 213 and burned there. The combustion exhaust gas is sent to the gas turbine 210. The electric power generated by the generator 211 driven by the gas turbine 210 is transmitted via the line 214. The flue gas exiting the gas turbine 210 is sent to the steam superheater 204 via the line 215. The flue gas exiting the steam superheater 204 is sent to the steam generator 217 via the line 216. Here, in the above description, the order of arrangement of the steam superheater 204 and the steam generator 217 is not specified. Steam generated by the steam generator 217 is introduced into the steam absorption refrigerator 219 via the line 218. The refrigerant generated from the vapor absorption refrigerator 219 is sent to the EO process 221 through the line 220.

  The refrigerant after being used as a cold heat source in the EO process 221 is sent to the refrigerator 219 via the line 222. The flue gas exiting the steam generator 217 is sent to the hot water generator 224 using the line 223. Hot water generated by the hot water generator 224 is introduced into the hot water absorption refrigerator 226 through the line 225. The refrigerant generated from the hot water absorption refrigerator 226 is guided to the EO process 221 through the line 227. The refrigerant after being used as cold heat in the EO process 221 is sent to the refrigerator 226 via the line 228.

  On the other hand, as described in Japanese Patent Application Laid-Open No. 2007-154857, the exhaust heat of the exhaust gas emitted from the steam superheater of the cogeneration apparatus (No. 321 described in Japanese Patent Application Laid-Open No. 2007-154857) is converted into a heat medium heater ( It is also possible to collect using 361). If necessary, the heat medium is sent to a heat medium heating furnace (371) through a line (370) and heated there. The heat medium is sent to the EG process (373) through the line (372) and used as a heat source there. The heat medium exiting the EG process (same 373) is sent to the heat medium heater (same 361) via the line (same 374).

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

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. 2, since the cogeneration system is divided into an EO process and a cogeneration apparatus, each will be described in turn.

(EO process)
The heat of oxidation reaction generated in the EO reactor 201 is removed by boiling heat transfer through hot water circulation. The hot water is guided to the gas-liquid separation tank 202, where it is used as saturated steam. The saturated steam is led via line 203 to a steam superheater 204 of the cogeneration apparatus, where it is converted to superheated steam. Superheated steam is sent via line 205 to a steam turbine 206 that powers the EO process. Steam output from the steam turbine 206 is used as a process heat source via a line 207.

(Cogeneration equipment)
The cogeneration apparatus includes a combustor 208, an air compressor 209, a gas turbine 210, a generator 211, and the like, and this configuration uses power generation by the generator 211 and exhaust heat generated at that time. The combustion exhaust gas that has exited the gas turbine is discharged through the steam superheater 204, the steam generator 217, and the hot water generator 225. Steam generated by the steam generator 217 is introduced into the steam absorption refrigerator 219 via the line 218. The refrigerant generated from the vapor absorption refrigerator 219 is guided to the EO process 221 through the line 220. The refrigerant after being used as a cold heat source in the EO process 221 is sent to the refrigerator 219 via the line 222. The flue gas exiting the steam generator 217 is sent to the hot water generator 224 using the line 223. Hot water generated by the hot water generator 224 is introduced into the hot water absorption refrigerator 226 through the line 225. The refrigerant generated in the hot water absorption refrigerator 226 is guided to the EO process 221 through the line 227. The refrigerant after being used as cold heat in the EO process 221 is sent to the refrigerator 226 via the line 228.

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

  FIG. 3 is a diagram showing the steam and refrigerant flow of the conventional EO technology. In FIG. 3, the vapor flow and the refrigerant flow of the EO process will be described in order.

(EO process)
The heat of oxidation reaction generated in the EO reactor 301 is removed by boiling heat transfer through hot water circulation. The hot water is guided to the gas-liquid separation tank 302, where it is converted to saturated steam. Saturated steam is led to a steam superheater 304 via a line 303 where it is converted to superheated steam. Superheated steam is sent via line 305 to a steam turbine 306 that serves as a power source for the EO process. Steam emitted from the steam turbine 306 is used as a process heat source via a line 307.

  The refrigerant is guided to the turbo refrigerator 309 via the line 308, and is cooled by supplying electric power. Further, the refrigerant is guided to the EO process 311 via the line 310. The refrigerant after being used as a cold heat source in the EO process 311 is sent to the refrigerator 309 via the line 308.

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

  Here, (cogeneration system total efficiency) = {(heat conversion amount of gas turbine power generation) + (heat amount received by steam in the steam superheater of the cogeneration unit) + (steam in the steam and hot water generator of the cogeneration unit) And the amount of heat received by the hot water)} / (heat conversion amount of gas turbine fuel consumption). The furnace efficiency of the heating furnace is 90%, the COP (cooling capacity (kWh) ÷ cooling power consumption (kWh)) of the steam absorption refrigerator is 1.5, the COP of the hot water absorption refrigerator is 0.7, turbo The COP of the refrigerator is 4.

  Under the operating conditions shown in Table 1, after the introduction, the fuel can be operated with zero fuel consumption in the heating furnace 304 of FIG. However, if there are fluctuations in the conditions of passing steam, fluctuations in the use conditions of the heat medium, or fluctuations in operating conditions, it is possible to cope with this 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 can be reduced by the amount of heat recovered in the heating furnace of the cogeneration device as compared to before introduction.

  Before the introduction, 7240 kW of gas turbine power generation after the introduction was covered by purchased power.

  As described in Japanese Patent Application Laid-Open No. 2007-154857, the power generated by the gas turbine of the cogeneration apparatus is the power of the motor that supplements the insufficient power in the air compressor, the power of the motor of the oxygen compressor, and the EO process, EG Consumed as process pump power used in the 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 factor, electric power: 0.25 L / kWh and fuel: 0.0258 L / MJ were used based on the conversion factor of the “Act on Rational Use of Energy”.

  (Total energy consumption before introduction) = (purchased power: 7240 kW + 1276 kW) × 0.25 + (fuel: 28338 MJ / h) × 0.0258 = 2905 L / h.

  (Total energy consumption after introduction) = (Gas turbine fuel: 79025 MJ / h) × 0.0258 = 2163 L / h.

  As an effect of introducing this system, energy saving of 25.5% in terms of crude oil equivalent was achieved.

  The overall efficiency of this cogeneration system was 83.1%, which was the same performance efficiency as a general steam generation type cogeneration system in the scale of this gas turbine.

The CO2 emission amount was compared before and after introduction. The calculation of CO2 emissions is based on the conversion factor of the Act on Promotion of Global Warming Countermeasures. Electricity: 0.418kg-CO2 / kWh, fuel: 0.0139C-kg / MJ, CO2 emissions 0.05094 kg-CO2 / MJ converted to γ was used.

  (Discharge amount before introduction) = (purchased power: 7240 kW + 1276 kW) × 0.418 + (fuel: 28338 MJ / h) × 0.05094 = 5003 kg−CO 2 / h.

(Discharge after introduction) = (Gas turbine fuel: 79025 MJ / h) × 0.05094 = 4026 kg−CO 2 / h.
As an introduction effect of this system, CO2 emissions decreased by 19.5%.

Regarding CO2 emission reduction, we verified CO2 emission reduction by introduction. The CO2 emission reduction amount is calculated based on the conversion factor of the Law Concerning Promotion of Global Warming Countermeasures, and 0.05094 kg-CO2 / MJ converted to CO2 emission based on fuel: 0.0139 C-kg / MJ. Was used. Electricity: 0.69 kg-CO2 / kWh was used by the Central Environment Council Global Environment Subcommittee “Completion of Goal Achievement Scenario Subcommittee (June 2001)”. The CO2 emission reduction amount according to the present invention is 3294 kg-CO2 / h. Further, in the example of Japanese Patent Laid-Open No. 2007-154857, when the CO2 emission reduction amount is obtained, it becomes 2800 kg-CO2 / h. From the above, compared with JP 2007-154857 A, the CO2 emission reduction amount of this system has been improved by 17.6%.

  The present invention is a cogeneration system that generates a refrigerant using exhaust heat that has not been used among the exhaust heat generated from a cogeneration apparatus, and uses the refrigerant in a chemical plant, and has been used for generating the refrigerant. Since the amount of electricity used can be greatly reduced, and as a result, CO2 emissions can be greatly suppressed, it makes a great contribution to global warming countermeasures.

Claims (5)

A part of the exhaust heat generated from the cogeneration device is used to superheat the steam generated from the chemical plant to obtain superheated steam, and at least a part of the remaining exhaust heat is used to generate cold, and the superheated steam And cogeneration system using cold energy in chemical plant. At least a part of the remaining exhaust heat is used in a steam or hot water generator provided in a cogeneration device to obtain steam and / or hot water, and further, the obtained steam or hot water is used to generate a refrigerant. The system according to claim 1, wherein at least one of the obtained steam, hot water, and refrigerant is used for 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, acrylic acid, maleic anhydride, phthalic anhydride, or methacrylic acid accompanied by a reaction heat generation type oxidation reaction using the system according to any one of claims 1 to 4.

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