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CN-121986212-A - Waste heat recovery system for producing industrial steam

CN121986212ACN 121986212 ACN121986212 ACN 121986212ACN-121986212-A

Abstract

The invention relates to a waste heat recovery system for producing steam for a chemical industry plant, comprising a discontinuously operating chemical industry plant having at least one coolable reactor (2) connected to a primary circuit, wherein the at least one reactor (2) is designed such that during operation of the reactor (2) a reaction of the reaction mixture takes place and waste heat produced by the cooling of the reactor (2) flows through the primary circuit in the form of a heating liquid or in the form of the reaction mixture itself as a first heat transfer fluid, wherein the primary circuit fluidly connects the reactor (2) to the first heat exchanger (9) in such a way that the first heat transfer fluid is cooled in the first heat exchanger (9) and then returns to the reactor (2) to cool the reactor (2), and a secondary circuit comprising a separate second heat transfer fluid and being coupled to the first heat exchanger (9) in such a way that during operation of the at least one reactor (2) the second heat transfer fluid is heated by the first heat transfer fluid and the secondary circuit (9) is fluidly connected downstream of the first heat storage unit (14), the first heat storage unit (14) and the second heat storage unit (13) downstream of the first heat storage unit (14) from the first heat exchanger (9) and downstream of the second heat storage unit (13) from each other, wherein the evaporator unit (13) is designed such that steam is generated during operation of the waste heat recovery system and is preferably supplied to the at least one compressor (18).

Inventors

  • U. S. Kohler
  • J. F. house
  • A. E.F. Buyaswag
  • A. Milioni

Assignees

  • 巴斯夫欧洲公司

Dates

Publication Date
20260505
Application Date
20240930
Priority Date
20231010

Claims (15)

  1. 1. A waste heat recovery system for generating steam for a chemical industrial facility, the waste heat recovery system comprising A non-continuously operable chemical industry plant having at least one coolable reactor (2) connected to a primary circuit, wherein the at least one reactor (2) is designed such that during operation of the reactor (2) a reaction of a reaction mixture takes place and waste heat generated by the cooling of the reactor (2) flows through the primary circuit as a first heat transfer fluid in the form of a heated liquid or in the form of the reaction mixture itself, wherein the primary circuit fluidly connects the reactor (2) to a first heat exchanger (9) in such a way that the first heat transfer fluid is cooled in the first heat exchanger (9) and then returned to the reactor (2) to cool the reactor (2), A secondary circuit comprising a separate second heat transfer fluid and being coupled to the first heat exchanger (9) such that during operation of the at least one reactor (2) the second heat transfer fluid is heated by the first heat transfer fluid and the secondary circuit fluidly connects a first heat storage unit (10) downstream from the first heat exchanger (9), an evaporator unit (13) downstream from the first heat storage unit (10), a second heat storage unit (14) downstream from the evaporator unit (13) and the first heat exchanger (9) downstream from the second heat storage unit (14) to each other, which completes the secondary circuit, Wherein the evaporator unit (13) is designed such that steam is generated during operation of the waste heat recovery system and is preferably supplied to at least one compressor (18).
  2. 2. Waste heat recovery system according to claim 1, wherein the at least one reactor (2) has at least one cooling element, preferably comprising at least one integrated cooling coil, an integrated tube bundle, and/or a heat exchanger external or internal to the at least one reactor (2), and wherein the at least one cooling element is fluidly connected to the primary loop and configured such that during operation of the industrial facility the first heat transfer fluid passes through the at least one cooling element.
  3. 3. Waste heat recovery system according to claim 1 or 2, wherein the second heat transfer fluid is water and the evaporator unit (13) is a flash tank unit having an inlet for filling the flash tank with the second heat transfer fluid, an inlet for filling the flash tank with water, preferably desalinated water, a water outlet for discharging water to the second heat storage unit (14), a steam outlet, and an expansion nozzle, which is designed such that during operation of the waste heat recovery system, expansion steam is generated as steam and is supplied to the at least one compressor (18) through the steam outlet.
  4. 4. Waste heat recovery system according to any one of the preceding claims, wherein the evaporator unit (13) is a heat exchanger unit having an inlet and an outlet for passing the second heat transfer fluid, an inlet for passing water, and a steam outlet, wherein the heat exchanger unit is designed such that during operation of the waste heat recovery system water in the heat exchanger unit evaporates and is fed to the at least one compressor (18) through the steam outlet.
  5. 5. A method of operating a waste heat recovery system for generating steam for a chemical industrial facility, the chemical industrial facility comprising A non-continuously operable chemical industry plant having at least one coolable reactor (2), wherein the at least one reactor (2) is designed such that during operation of the reactor (2) a reaction of the reaction mixture takes place and waste heat generated by the cooling of the reactor (2) flows as a heating liquid or as the reaction mixture itself through a primary circuit as a first heat transfer fluid, wherein the primary circuit fluidly connects the reactor (2) to a first heat exchanger (9) in such a way that the first heat transfer fluid is cooled in the first heat exchanger (9) and then returned to the reactor (2) to cool the reactor (2), A secondary circuit comprising a separate second heat transfer fluid and being thermally coupled to the first heat exchanger (9) in such a way that during operation of the at least one reactor (2) the second heat transfer fluid is heated by the first heat transfer fluid, and The secondary circuit fluidly connects a first heat storage unit (10) downstream from the first heat exchanger (9), an evaporator unit (13) downstream from the first heat storage unit (10), a second heat storage unit (14) downstream from the evaporator unit (13) and the first heat exchanger (9) downstream from the second heat storage unit (14) to each other, which completes the secondary circuit, The method comprises the following steps when the at least one reactor (2) is operated: feeding reactants into said at least one reactor (2), The reaction is carried out in the at least one reactor (2), Cooling the at least one reactor (2) by means of the first heat transfer fluid, which preferably flows through the first heat exchanger (9), Transferring a portion of the heat of the first heat transfer fluid to the second heat transfer fluid by means of the first heat exchanger (9), wherein, The second heat transfer fluid at the inlet of the first heat exchanger (9) is at a temperature in the range of 10 to 1450 ℃ and an absolute pressure in the range of 0.1 to 400 bar, and the second heat transfer fluid at the outlet of the first heat exchanger (9) is at a temperature in the range of 30 to 1500 ℃ and an absolute pressure in the range of 0.1 to 400 bar, And the first heat transfer fluid at the inlet of the first heat exchanger (9) is at a temperature in the range of 35 ℃ to 1500 ℃ and an absolute pressure in the range of 0.1 bar to 400 bar, and the first heat transfer fluid at the outlet of the first heat exchanger (9) is at a temperature in the range of 30 ℃ to 1500 ℃ and an absolute pressure in the range of 0.1 bar to 400 bar, Feeding the heated second heat transfer fluid to the first heat storage unit (10), wherein the second heat transfer fluid within the first heat storage unit (10) is at a temperature in the range of 30 to 1500 ℃ and an absolute pressure in the range of 0.1 to 400 bar, Feeding the second heat transfer fluid from the first heat storage unit (10) to the evaporator unit (13), wherein the flow rate of the second heat transfer fluid is determined in dependence of both the heat flow rate transferred by the evaporator unit (13) and the filling level of the first heat storage unit (10) and is regulated by a first valve (12) located between the first heat storage unit (10) and the second heat storage unit (14) in the main flow direction, And the temperature of the second heat transfer fluid at the inlet of the evaporator unit (13) is in the range of 30 ℃ to 1500 ℃ and the absolute pressure at the inlet of the evaporator unit (13) is in the range of 0.1 bar to 400 bar, And the temperature of the second heat transfer fluid at the outlet of the evaporator unit (13) is in the range of 10 ℃ to 1450 ℃ and the absolute pressure at the outlet of the evaporator unit (13) is in the range of 0.1 bar to 400 bar, Feeding water(s) to the evaporator unit (13) through a feed (p) outside the secondary circuit, wherein the water(s) at the inlet of the evaporator unit (13) is at a temperature in the range of 5 ℃ to 400 ℃ and an absolute pressure in the range of 0.001 bar to 300 bar, Generating steam in the evaporator unit (13) by heat supplied from the second heat transfer fluid, wherein the steam at the steam outlet of the evaporator unit (13) is at a temperature in the range of 5 to 373 ℃ and at an absolute pressure in the range of 0.001 to 220 bar, Feeding steam from the steam outlet of the evaporator unit (13) through a conduit (q) outside the secondary circuit to at least one compressor (18) compressing the steam (r) to an absolute pressure in the range of 0.5 bar to 220 bar, and the temperature of the steam (r) at the outlet of at least one compressor (18) is correspondingly in the range of 5 ℃ to 373 ℃, Feeding the second heat transfer fluid from the evaporator unit (13) to the second heat storage unit (14), wherein the second heat transfer fluid in the second heat storage unit (14) is at a temperature in the range of 10 to 1450 ℃ and an absolute pressure in the range of 0.1 to 400 bar, and Feeding the second heat transfer fluid from the second heat storage unit (14) to the first heat exchanger (9), And comprising the following steps when one reactor (2) is not operating or when there are no reactors operating in the case of a plurality of reactors: Feeding the second heat transfer fluid from the first heat storage unit (10) to the evaporator unit (13), wherein the flow rate of the second heat transfer fluid is determined from both the heat flow rate transferred by the evaporator unit (13) and the filling level of the first heat storage unit (10) and is regulated by a first valve (12) located between the first heat storage unit (10) and the second heat storage unit (14) in the main flow direction, and the temperature of the second heat transfer fluid at the inlet of the evaporator unit (13) is in the range of 30 to 1500 ℃ and the absolute pressure at the inlet of the evaporator unit (13) is in the range of 0.1 to 400 bar, Feeding water(s) to the evaporator unit (13) through a feed (p) outside the secondary circuit, wherein the water(s) at the inlet of the evaporator unit (13) is at a temperature in the range of 5 ℃ to 400 ℃ and an absolute pressure in the range of 0.001 bar to 300 bar, Generating steam in the evaporator unit (13) by heat supplied from the second heat transfer fluid, wherein the steam at the outlet of the evaporator unit (13) is at a temperature in the range of 5 to 373 ℃ and at an absolute pressure in the range of 0.001 to 220 bar, Feeding the steam from the evaporator unit (13) to at least one compressor (18) compressing the steam (r) to an absolute pressure in the range of 0.5 bar to 373 bar, and the temperature of the steam (r) at the outlet of the at least one compressor (18) is correspondingly in the range of 80 ℃ to 220 ℃, Feeding the second heat transfer fluid from the evaporator unit (13) to the second heat storage unit (14), wherein the second heat transfer fluid in the second heat storage unit (14) is at a temperature in the range of 10 to 1450 ℃ and an absolute pressure in the range of 0.1 to 400 bar, and Blocking the flow of the second heat transfer fluid in the main flow direction between the second heat storage unit (14) and the first heat storage unit (10) by cutting off the flow via a second valve (16) located between the second heat storage unit (14) and the first heat storage unit (10) in the main flow direction.
  6. 6. Method of operating a waste heat recovery system according to claim 5, wherein the evaporator unit (13) is a heat exchanger unit and the at least one compressor (18) is a mechanical vapor compressor and the water at the inlet of the evaporator unit (13) is at a temperature in the range of 5 to 400 ℃ and an absolute pressure in the range of 0.001 to 300 bar, and furthermore the vapor (r) is compressed by the at least one compressor (18) to an absolute pressure in the range of 0.5 to 220 bar and the temperature of the vapor (r) at the outlet of the at least one compressor (18) is correspondingly in the range of 80 to 373 ℃.
  7. 7. Method of operating a waste heat recovery system according to claim 5, wherein the evaporator unit (13) is a flash tank unit and the at least one compressor (18) is a mechanical vapor compressor and the water at the inlet of the flash tank unit is at a temperature in the range of 5 to 400 ℃ and an absolute pressure in the range of 0.001 to 300 bar, and furthermore, the vapor (r) is compressed by the at least one compressor (18) to an absolute pressure in the range of 0.5 to 220 bar and the temperature of the vapor (r) at the outlet of the at least one compressor (18) is correspondingly in the range of 80 to 373 ℃.
  8. 8. Method of operating a waste heat recovery system according to any of the claims 5 to 7, wherein the temperature of the second heat transfer fluid at the inlet of the first heat storage unit (10) is regulated by a first closed loop temperature controller (TC, T3) with its associated temperature sensor (T3) between the second and the first heat storage unit (14, 10) in the main flow direction in combination with a first closed loop flow controller (FC, F1) with its associated flow sensor (F1), wherein the first closed loop temperature controller (TC, T3) determines a difference between a predetermined setpoint value and the temperature of the second heat transfer fluid at the inlet of the first heat storage unit (10) detected by the first closed loop temperature controller (TC, T3), And wherein the first closed-loop temperature controller (TC, T3) transmits a setpoint value to the first closed-loop flow controller (FC, F1) based on the determined difference, and the first closed-loop flow controller (FC, F1) adjusts the flow from the second heat storage unit to the first heat storage unit (14, 10) in accordance with the setpoint value and the measured flow of the second heat storage unit to the first heat storage unit (14, 10).
  9. 9. Method of operating a waste heat recovery system according to any of the claims 5 to 8, wherein the temperature of the second heat transfer fluid at the inlet of the second heat storage unit (14) is regulated by a second closed loop temperature controller (TC, T4) with its associated temperature sensor (T4) in combination with a second closed loop flow controller (FC, F3) with its associated flow sensor (F3) in the feed (p) of the evaporator unit (13), Wherein the second closed loop temperature controller (TC, T4) determines a difference between a predetermined setpoint value and the temperature of the second heat transfer fluid at the inlet of the second heat storage unit (14) detected by the second closed loop temperature controller (TC, T4), and Wherein the second closed-loop temperature controller (TC, T4) transmits a setpoint value to the second closed-loop flow controller (FC, F3) based on the determined difference, and the second closed-loop flow controller (FC, F3) adjusts the flow of the water(s) into the conduit (p) of the evaporator unit (13) by means of a valve (17) as a function of the setpoint value and a measured flow into the conduit (p) of the evaporator unit (13).
  10. 10. Method of operating a waste heat recovery system according to claim 9, wherein the operating load of the at least one compressor (18) is adjusted according to the valve position of the valve (17) to a value in the range of 30% to 100%, preferably 60% to 100% based on its maximum operating load.
  11. 11. Method of operating a waste heat recovery system according to any of the preceding claims 5-10, wherein a first closed loop fill level controller (LC, l1_1) with its associated fill level sensor (l1_1) is used as a higher level closed loop controller for the first heat storage unit (10), and if the fill level sensor (l1_1) detects a value exceeding a defined maximum fill level of the first heat storage unit (10), the valve 8 is throttled and the valve 6 is opened in order to cool at least some of the mass flow of the first heat transfer fluid in the conduit (d) in the process heat exchanger (7).
  12. 12. The method of operating a waste heat recovery system according to any one of claims 5 to 11, wherein a closed loop load controller (UC) with its associated sensor: a flow sensor (F2) comprised in the conduit (o) and/or the conduit (n), a temperature sensor (T4) in the conduit (o), and a temperature sensor (T1) for detecting the temperature in the first heat storage unit (10), Detecting a difference in heat flow between the heat flow of the second heat transfer fluid in the conduit (o) and the heat flow of the second heat transfer fluid in the conduit (n) and using the difference in heat flow to calculate a difference between the measured difference in heat flow and a defined load set point, Wherein the setpoint value based on the difference is delivered to a third closed loop flow controller (FC, F2) as a slave controller having its associated flow sensor F2, And the difference between the flow of the second heat transfer fluid in the conduit (o) or the conduit (n) to be calculated by the third closed loop flow controller (FC, F2) and a setpoint value determined by the closed loop load controller (UC) is used as a basis for closed loop control of the second secondary loop valve (12), which adjusts the flow of the second heat transfer fluid in the conduit (o) accordingly.
  13. 13. The method of operating a waste heat recovery system according to claim 12, wherein the defined load set point is determined by a second closed loop fill level controller (LC, l1_2) with its associated fill level sensor (l1_2) within the first heat storage unit (10), wherein the second closed loop fill level controller (LC, l1_2) is a master controller and preferably a P controller, and wherein the second closed loop fill level controller (LC, l1_2) calculates a difference between the fill level of the first heat storage unit (10) and a defined set point value and transmits a load set point to the closed loop load controller (UC) based on the difference.
  14. 14. The method of operating a waste heat recovery system according to claim 13, wherein the second closed loop fill level controller (LC, l1_2) detects a continuous fill level value in the first heat storage unit (10) and determines a load set point of the closed loop load controller (UC) from the detected fill level value, wherein the detected fill level value is limited in a range from a defined minimum fill level value to a defined maximum fill level value.
  15. 15. Method of operating a waste heat recovery system according to claim 13, wherein the defined load set point is determined by the filling level sensor (l1_2), wherein the load set point can take on discrete values only and preferably can be switched between a first value corresponding to minimum steam generation and a second value corresponding to maximum steam generation only.

Description

Waste heat recovery system for producing industrial steam The invention relates to a waste heat recovery system for generating steam for a chemical industry plant, comprising a non-continuously operable chemical industry plant having at least one coolable reactor connected to a primary loop, wherein the at least one reactor is designed such that during operation of the reactor a reaction of the reaction mixture takes place and waste heat generated by the cooling of the reactor flows through the primary loop as a first heat transfer fluid in the form of a heating liquid or in the form of the reaction mixture itself, wherein the primary loop fluidly connects the reactor to a first heat exchanger in such a way that the first heat transfer fluid is cooled in the first heat exchanger and then returned to the reactor for cooling the reactor. It is known from the general prior art that waste heat recovery systems can increase the efficiency of chemical processes. In the case of batch processes or in the case of continuous processes which have to be interrupted relatively frequently, for example due to maintenance, there is the general problem that waste heat cannot be recovered during the interruption. At this time, the heat storage medium can at least compensate for the gap caused by the specific interruption time. However, the integration of the heat storage medium is very complex and varies considerably in implementation depending on the particular application. KR-2015-0032241A discloses a waste heat recovery system that uses discontinuously generated waste heat from a batch reactor to generate steam as needed. The system includes a heat transfer fluid in the loop that cools the reactor and releases its absorbed heat from the reactor by heat transfer. Here, the heat is transferred by a heat exchanger heating a further heat transfer fluid (and which is fed to the flash tank to generate steam) or by heat transfer directly at the water level of the flash tank. A steam storage device as a heat storage device is connected downstream of the flash tank steam outlet so that there is still available steam in case of an interruption of the reactor operation. However, this embodiment has the disadvantage that the steam occupies a large volume with respect to its energy content and that the steam storage must be correspondingly large. In addition, the vapor storage device must also be capable of withstanding vapor pressures. US 2010/0319348 A1 discloses a waste heat recovery system of another technical field in which a hot waste fluid of a combustion furnace, such as flue gas, flows through a heat exchanger configured such that energy in the form of heat can be transferred to a heat transfer fluid. The energy in the heat transfer fluid is used to generate electrical energy. Waste heat recovery systems are used in batch processes where the energy produced is continuously available. This is achieved by a first heat storage means before the energy generation and a second heat storage means after the energy generation, wherein it is possible to store a heat transfer fluid in both heat storage means. In case of a process interruption, the stored heat transfer fluid flows from the first heat storage means to the second heat storage means in order to thereby generate electric power. However, a limitation of this embodiment is that energy from the hot waste fluid is recovered only in the form of usable electricity. The waste fluid cooled by the heat exchanger is not used further in the current process. A disadvantage of the current process is that the cooled waste fluid is not used further. The problem to be solved is therefore to provide a waste heat recovery system for generating steam for a chemical industrial installation, wherein the waste heat taken for cooling a intermittently operated reactor is also used for generating steam, it being possible to continue the continuous generation of steam even in case of an interruption of the reactor operation. Another problem to be solved is to be able to operate the waste heat recovery system efficiently and stably. According to the present invention, these problems are solved by a waste heat recovery system according to claim 1 and a method of operating a waste heat recovery system according to claim 5. Advantageous embodiments of the waste heat recovery system of the invention are given in claims 2 to 4. Furthermore, advantageous embodiments of the method for operating a waste heat recovery system of the invention are given in claims 6 to 15. The waste heat recovery system for producing steam for a chemical industrial plant according to the invention comprises a discontinuously operating chemical industrial plant having at least one coolable reactor connected to a primary circuit, wherein the at least one reactor is designed such that during operation of the reactor a reaction of the reaction mixture takes place and waste heat produced by the cooling of the reactor flows through the