Methanol synthesis dewaxing coupling waste heat recovery system, power generation system and power generation method

Abstract

The invention relates to a methanol synthesis wax removal coupling waste heat recovery system, a power generation system and a power generation method.The methanol synthesis wax removal coupling waste heat recovery system comprises an evaporator before wax removal, an evaporator after wax removal and a waste heat utilization device; the pre-wax-removal evaporator is used for being communicated with an inflow channel of a wax remover and used for absorbing heat of gas before wax removal, and the post-wax-removal evaporator is used for being communicated with a gas outflow channel of the wax remover and used for absorbing heat of the gas after wax removal. The waste heat utilization device is communicated with the pre-wax-removal evaporator and the post-wax-removal evaporator through a pipeline, and a heat exchange agent is arranged in the pipeline. According to the methanol synthesis wax removal coupling waste heat recovery system, waste heat generated before and after methanol synthesis wax removal can be well recycled, so that energy waste in the methanol synthesis wax removal process is reduced, energy consumption can be reduced, and the energy conservation and environmental protection properties are relatively good.

Description

Technical Field

[0001] The present application relates to the technical field of methanol synthesis, and in particular to a methanol synthesis dewaxing coupled waste heat recovery system, a power generation system and a power generation method. Background Art

[0002] In industry, methanol is usually synthesized by pressurized catalytic hydrogenation of carbon monoxide and carbon dioxide. The methanol synthesis catalyst is sensitive to temperature changes, hydrogen-carbon ratio composition, and the content of carbonyl compounds in the system, and is prone to generate high-carbon chain hydrocarbons and paraffin hydrocarbons, namely paraffin. If the paraffin is not removed in time, on the one hand, the paraffin will condense in the heat exchanger, causing the heat exchange efficiency of the distillation system to decrease and the consumption of circulating water to increase; on the other hand, the generated paraffin will condense in the methanol final condenser, resulting in a decrease in heat exchange efficiency and a decrease in methanol yield. Therefore, a dewaxing tank needs to be set in the methanol synthesis loop.

[0003] In the existing technology, a dewaxing device is generally installed at the outlet of the methanol thermostat. The medium operating temperature is 100-130°C. At this time, the paraffin is in the liquid phase and part of the paraffin is discharged from the system. The dewaxing process gas is cooled by the air cooler and the water cooler and then enters the methanol separation tank. The traditional methanol synthesis dewaxing process is detailed as follows Figure 1 As shown, the process gas 10 from the methanol synthesis reactor 1 is cooled to 120-160°C by the heat exchanger 2, and the cooled process gas 11 is cooled to 100-130°C by the air cooler 3 (or water cooler) and then enters the dewaxing device 4 through the inflow channel of the dewaxing device 4 for dewaxing to remove C33 and below polycarbon paraffin components in the crude methanol. The process gas 13 at the outlet of the gas outflow channel of the dewaxing device 4 is cooled to ~40°C by the water cooler 6 and then enters the methanol separator 7 to complete the gas-liquid separation of the product; the liquid methanol 14 at the bottom of the dewaxing device 4 flows out from the liquid outflow channel and is cooled to ~40°C by the water cooler 5. The cooled liquid methanol 15 is mixed with the liquid methanol 16 at the bottom of the methanol separator 7 and then enters the methanol expansion tank 9. However, in the traditional methanol synthesis dewaxing process, the air cooler and water cooler cooling system have large power consumption and circulating water consumption, especially when the ambient temperature is high, the system power consumption and circulating water consumption are greater, and the energy saving and environmental protection are relatively poor. Summary of the invention

[0004] Based on this, it is necessary to provide a methanol synthesis dewaxing coupled waste heat recovery system, a power generation system and a power generation method that can reduce energy consumption and have relatively good energy conservation and environmental protection.

[0005] In the first aspect, the present application provides a methanol synthesis dewaxing coupled waste heat recovery system, including a pre-dewaxing evaporator, a post-dewaxing evaporator and a waste heat utilization device, wherein the pre-dewaxing evaporator is used to be connected to the inflow channel of the dewaxing device and used to absorb the heat of the gas before dewaxing, the post-dewaxing evaporator is used to be connected to the gas outflow channel of the dewaxing device and used to absorb the heat of the gas after dewaxing, and the waste heat utilization device is connected to the pre-dewaxing evaporator and the post-dewaxing evaporator through a pipeline, and a heat exchanger is provided in the pipeline. For example, the methanol synthesis dewaxing coupled waste heat recovery system is a methanol synthesis dewaxing waste heat recovery system.

[0006] The above-mentioned methanol synthesis dewaxing coupled waste heat recovery system, the evaporator before dewaxing is used to be connected to the inflow channel of the dewaxing device, and is used to recover the waste heat of the process gas coming out of the methanol synthesis reactor before dewaxing through a heat exchanger, and the evaporator after dewaxing is used to be connected to the gas outflow channel of the dewaxing device, and is used to recover the waste heat of the gas after dewaxing through a heat exchanger. The waste heat can be coupled and further utilized by the waste heat utilization device. In this way, the waste heat before and after methanol synthesis dewaxing can be better recovered and utilized, thereby reducing the energy waste in the methanol synthesis dewaxing process, reducing energy consumption, and having relatively good energy saving and environmental protection.

[0007] In one embodiment, the methanol synthesis dewaxing coupled waste heat recovery system also includes a liquid waste heat evaporator, which is connected to the waste heat utilization device through a pipeline, and the liquid waste heat evaporator is used to be connected to the liquid outflow channel of the dewaxing device and to absorb the heat of the dewaxed liquid.

[0008] In one embodiment, the waste heat utilization device has an output end and a recovery end opposite to each other;

[0009] The output end of the waste heat utilization device is connected to the recovery end of the waste heat utilization device through the liquid waste heat evaporator and the pre-dewaxing evaporator in sequence, and / or the output end of the waste heat utilization device is connected to the recovery end of the waste heat utilization device through the post-dewaxing evaporator and the pre-dewaxing evaporator in sequence.

[0010] In one embodiment, the waste heat utilization device is a heat exchange device, a heat-to-work conversion device or a heat pump system.

[0011] In the second aspect, the present application provides a methanol synthesis dewaxing coupled waste heat power generation system, including the methanol synthesis dewaxing coupled waste heat recovery system as described in any of the above embodiments, the waste heat utilization device includes a turbine and a condenser, the input end of the turbine is connected to the output end of the evaporator before dewaxing and the output end of the evaporator after dewaxing through a pipeline, the condenser has a relative input end and output end, the output end of the turbine is connected to the input end of the condenser, the output end of the condenser is connected to the input end of the evaporator before dewaxing and the input end of the evaporator after dewaxing through a pipeline, the turbine is used to convert the heat energy of the heat exchanger into mechanical energy, and at the same time drive power generation and output electrical energy to the outside. For example, the dewaxing coupled waste heat power generation system is a dewaxing waste heat power generation system.

[0012] The above-mentioned methanol synthesis dewaxing coupled waste heat power generation system can utilize the waste heat of the gas after dewaxing through a heat exchanger to recover the waste heat, and further utilize the waste heat through a waste heat utilization device. In this way, the waste heat before and after the methanol synthesis dewaxing can be better recovered and utilized for power generation, thereby reducing the energy waste in the methanol synthesis dewaxing process, reducing energy consumption, and having relatively good energy saving and environmental protection properties.

[0013] In one embodiment, the turbine is an organic fluid turbine expander.

[0014] In one embodiment, the turbine machine adopts a single-stage turbine expander and a direct-drive explosion-proof DC excitation generator.

[0015] In one embodiment, the turbine uses a 1500rpm single-stage turbine expander and a direct-drive 1500rpm explosion-proof DC excitation generator.

[0016] In one embodiment, the heat exchanger is refrigerant R245fa or a similar functional organic working fluid.

[0017] In one embodiment, the pre-dewaxing evaporator, the post-dewaxing evaporator and / or the liquid waste heat evaporator are finned shell and tube heat exchangers.

[0018] In one embodiment, it also includes a dewaxing device, which includes a methanol synthesis reactor, a first heat exchanger, a dewaxing device, a second heat exchanger, a methanol separator and a methanol expansion tank. The methanol synthesis reactor, the first heat exchanger, the evaporator before dewaxing and the dewaxing device are connected in sequence, the gas outflow channel of the dewaxing device, the evaporator after dewaxing, the second heat exchanger, the methanol separator and the methanol expansion tank are connected in sequence, and the liquid outflow channel of the dewaxing device is connected to the methanol expansion tank.

[0019] In a third aspect, the present application also provides a method for generating electricity by coupling waste heat from methanol synthesis and dewaxing, which uses a methanol synthesis and dewaxing coupled waste heat power generation system as described in any of the above embodiments to generate electricity and output electrical energy. For example, the method for generating electricity by coupling waste heat from methanol synthesis and dewaxing is a method for generating electricity by coupling waste heat from methanol synthesis and dewaxing.

[0020] The above-mentioned method of utilizing methanol synthesis and dewaxing coupled with waste heat for power generation adopts the above-mentioned methanol synthesis and dewaxing coupled with waste heat for power generation system to generate electricity and output electric energy to the outside, which can better recycle the waste heat before and after methanol synthesis and dewaxing and use it for power generation, thereby reducing energy waste in the methanol synthesis and dewaxing process, can reduce energy consumption, and has relatively good energy saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the traditional methanol synthesis dewaxing process;

[0022] Figure 2 A schematic diagram of a methanol synthesis dewaxing process using a methanol synthesis dewaxing coupled waste heat recovery system and a power generation system according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present application, in order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application, and the preferred implementation methods of the present application are given in the accompanying drawings. However, the present application can be implemented in many different forms and is not limited to the implementation methods described herein. On the contrary, the purpose of providing these implementation methods is to make the disclosure of the present application more thoroughly and comprehensively understood. The present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited to the specific embodiments disclosed below. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined. It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a central element at the same time. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0024] In the first aspect, the present application provides a methanol synthesis dewaxing coupled waste heat recovery system, please combine Figure 2, which is a schematic diagram of a methanol synthesis dewaxing process using a methanol synthesis dewaxing coupled waste heat recovery system and a power generation system according to an embodiment of the present application. Specifically, the dewaxing coupled waste heat recovery system includes a pre-dewaxing evaporator 3, a post-dewaxing evaporator 5, and a waste heat utilization device A. The pre-dewaxing evaporator 3 is used to be connected to the inflow channel of the dewaxing device 4 and used to absorb the heat of the gas before dewaxing. The post-dewaxing evaporator 5 is used to be connected to the gas outflow channel of the dewaxing device 4 and used to absorb the heat of the gas after dewaxing. The waste heat utilization device A is connected to the pre-dewaxing evaporator 3 and the post-dewaxing evaporator 5 through a pipeline, and a heat exchanger is provided in the pipeline. That is, the process gas from the methanol synthesis reactor 1 first passes through the pre-dewaxing evaporator 3 for heat exchange before flowing through the dewaxing device 4. Since the heat exchanger flows in the pre-dewaxing evaporator 3, the corresponding heat of the process gas is partially absorbed by the heat exchanger in the pre-dewaxing evaporator 3, which is used to recover the waste heat of the process gas from the methanol synthesis reactor 1 before dewaxing. The temperature of the process gas at the outlet of the dewaxing device 4 after dewaxing is relatively high, and waste heat can be recovered. In the present application, the evaporator 5 after dewaxing is connected to the gas outflow channel of the dewaxing device 4, which is used to recover the waste heat of the gas 20 after dewaxing through a heat exchanger, and further utilize the waste heat through a waste heat utilization device A. In this way, the waste heat before and after dewaxing in methanol synthesis can be better recovered and utilized, thereby reducing energy waste in the methanol synthesis dewaxing process, reducing energy consumption, and being relatively energy-saving and environmentally friendly.

[0025] Specifically, the waste heat utilization device A is a heat exchange device, a heat-to-work conversion device or a heat pump system. When the waste heat utilization device is a heat exchange device, it can be directly used as a heat source for heating. When the waste heat utilization device is a thermal conversion device, it can be used directly to do work or generate electricity. When the waste heat device is a heat pump system, such as a bromide refrigerator, it is not limited to this. Preferably, the heat utilization device is a heat-to-work conversion device, such as waste heat recovery using the organic Rankine cycle process principle to convert thermal energy into mechanical energy, which is finally converted into electrical energy through a generator, and the energy conversion efficiency is high.

[0026] In the above-mentioned methanol synthesis dewaxing coupled waste heat recovery system, the evaporator 3 before dewaxing is used to be connected to the inflow channel of the dewaxing device 4, and is used to recover the waste heat of the process gas coming out of the methanol synthesis reactor 1 before dewaxing through a heat exchanger, and the evaporator 5 after dewaxing is used to be connected to the gas outflow channel of the dewaxing device 4, and is used to recover the waste heat of the gas after dewaxing through a heat exchanger, and further utilize the waste heat through a waste heat utilization device. In this way, the waste heat before and after methanol synthesis dewaxing can be better recovered and utilized, thereby reducing the energy waste in the methanol synthesis dewaxing process, reducing energy consumption, and having relatively good energy saving and environmental protection.

[0027] Considering that the liquid phase temperature of the liquid outflow channel of the dewaxing device 4 is relatively high, in order to further recover the remaining heat, in one embodiment, refer to Figure 2 , the methanol synthesis dewaxing coupled waste heat recovery system also includes a liquid waste heat evaporator 6, which is connected to the waste heat utilization device A through a pipeline, and the liquid waste heat evaporator 6 is used to be connected to the liquid outflow channel of the dewaxing device 4, and is used to recover the waste heat of the liquid phase of the liquid outflow channel of the dewaxing device 4. In this way, on the basis of utilizing the waste heat of the process gas at the outlet of the dewaxing device 4, the waste heat of the liquid phase of the dewaxing device 4 can also be better utilized. From the perspective of waste heat recovery, the present application takes into account the high temperatures of the process gas 20 at the outlet of the dewaxing device 4 and the liquid phase 15 of the dewaxing device 15, and can recover waste heat together with the process gas at the outlet of the methanol thermostat. The operating temperature of the process gas after recovering the waste heat is 80 to 130°C, which can remove the long-chain hydrocarbon paraffin components of C40 and below in the crude methanol.

[0028] Of course, the waste heat utilization device usually needs to be set as a circulating communication channel. In one embodiment, the waste heat utilization device A has a relative output end and a recovery end; the output end of the waste heat utilization device A is connected to the recovery end of the waste heat utilization device A through the liquid waste heat evaporator 6 and the pre-dewaxing evaporator 3 in sequence, and / or, the output end of the waste heat utilization device A is connected to the recovery end of the waste heat utilization device A through the post-dewaxing evaporator 5 and the pre-dewaxing evaporator 3 in sequence. In other words, since the heat absorbed at the pre-dewaxing evaporator 3 is relatively higher than the heat of the post-dewaxing evaporator 5 and the liquid waste heat evaporator 6, the pre-dewaxing evaporator 3 further absorbs heat from the heat exchanger that has absorbed heat after passing through the post-dewaxing evaporator 5 and the liquid waste heat evaporator 6, thereby improving the recovery of waste heat, facilitating the subsequent use of waste heat for work, thereby improving the thermal entropy, and the isentropic efficiency is about 80%.

[0029] In one embodiment, the heat exchange agent is refrigerant R245fa. In this embodiment, refrigerant R245fa is a non-flammable refrigerant, which is used as an intermediate medium to extract heat. Of course, the heat exchange agent can also be other heat exchange agents known in the art. The applicant has found through research that by using the heat exchange agent as refrigerant R245fa and selecting the waste heat utilization device A as a thermal conversion device, the waste heat utilization can increase the thermal entropy, and the isentropic efficiency is about 80%.

[0030] In the above-mentioned methanol synthesis dewaxing coupled waste heat recovery system, the evaporator 3 before dewaxing is used to be connected to the inflow channel of the dewaxing device 4, and is used to recover the waste heat of the process gas coming out of the methanol synthesis reactor 1 before dewaxing through a heat exchanger, and the evaporator 5 after dewaxing is used to be connected to the gas outflow channel of the dewaxing device 4, and is used to recover the waste heat of the gas after dewaxing through a heat exchanger, and further utilize the waste heat through a waste heat utilization device. In this way, the waste heat before and after methanol synthesis dewaxing can be better recovered and utilized, thereby reducing the energy waste in the methanol synthesis dewaxing process, reducing energy consumption, and having relatively good energy saving and environmental protection.

[0031] In the second aspect, the present application provides a methanol synthesis dewaxing coupled waste heat power generation system, including the methanol synthesis dewaxing coupled waste heat recovery system as described in any of the above embodiments. In other words, when the waste heat utilization device A of the methanol synthesis dewaxing coupled waste heat recovery system is used for power generation, the methanol synthesis dewaxing coupled waste heat recovery system is the methanol synthesis dewaxing coupled waste heat power generation system. Please continue to combine Figure 2 , which is a schematic diagram of a methanol synthesis dewaxing process using a methanol synthesis dewaxing coupled waste heat recovery system and a power generation system according to an embodiment of the present application. The waste heat utilization device A includes a turbine 10 and a condenser 11. The input end of the turbine 10 is connected to the output end of the pre-dewaxing evaporator 3 and the output end of the post-dewaxing evaporator 5 through a pipeline. Preferably, the output end of the post-dewaxing evaporator 5 is connected to the input end of the turbine 10 through the pre-dewaxing evaporator 3. The turbine 5 is used to convert the heat energy of the heat exchanger into mechanical energy, while driving power generation and outputting electrical energy to the outside. In the specific embodiment of the present application, by selecting the heat exchanger as R245fa, it is converted into a gaseous state after absorbing heat, and after the heat and work conversion of the turbine 5 and used for discharge, it is cooled into a liquid state through the condenser 11, and then circulated again for passing through the post-dewaxing evaporator 5, the liquid waste heat evaporator 6, and the pre-dewaxing evaporator 3 for waste heat absorption. Specifically, the condenser 11 has a relative input end and an output end. The output end of the turbine 10 is connected to the input end of the condenser 11, and the output end of the condenser 11 is connected to the input end of the pre-dewaxing evaporator 3 and the input end of the post-dewaxing evaporator 5 through a pipeline. Preferably, the output end of the condenser 11 is connected to the input end of the pre-dewaxing evaporator 3 through the post-dewaxing evaporator 5. More preferably, the output end of the condenser 11 is also connected to the input end of the pre-dewaxing evaporator 3 through the liquid waste heat evaporator 6.

[0032] The above-mentioned methanol synthesis and dewaxing coupled waste heat power generation system can utilize the waste heat of the gas after dewaxing through a heat exchanger to recover the waste heat, and further utilize the waste heat through a waste heat utilization device A. In this way, by adopting a turbine 10, the waste heat before and after methanol synthesis and dewaxing can be better recovered and utilized for power generation, thereby reducing energy waste in the methanol synthesis and dewaxing process, reducing energy consumption, and having relatively good energy-saving and environmental protection properties.

[0033] In one embodiment, the turbine 5 is an organic working fluid turbine expander. That is, it can convert the heat of the organic working fluid into heat work. For another example, the organic working fluid includes but is not limited to R245fa and similar functional organic working fluids or other similar heat exchangers. It can also be understood that the heat exchanger is an organic working fluid heat exchanger. Of course, it is not limited to this. It can also be other heat exchangers known in the art. When it is other heat exchangers, the corresponding turbine expander can be selected. For example, the turbine 5 adopts a single-stage turbine expander and a direct-drive explosion-proof DC excitation generator. For another example, the turbine adopts a 1500rpm single-stage turbine expander and a direct-drive 1500rpm explosion-proof DC excitation generator, that is, the turbine 5 adopts a 1500rpm single-stage turbine expander + (direct drive) 1500rpm explosion-proof DC excitation generator. In this way, the thermal conversion entropy of the system can be better provided, reaching about 80%. For example, the evaporator before dewaxing, the evaporator after dewaxing and / or the liquid waste heat evaporator are finned shell and tube heat exchangers. Of course, it should be noted that the evaporator before dewaxing, the evaporator after dewaxing and / or the liquid waste heat evaporator are used to absorb heat and evaporate the heat exchanger to become a gaseous state, or to further heat other things. The evaporator before dewaxing, the evaporator after dewaxing and / or the liquid waste heat evaporator are all evaporators or heat exchangers. The addition of "before dewaxing", "after dewaxing", "liquid waste heat" and the like here is mainly for the convenience of distinction. That is, the heat exchanger preferably used in this application usually has two states of gas and liquid, and can be converted from gas to liquid when absorbing heat. Of course, the heat exchanger of this application is not limited to this. In addition, the finned shell and tube heat exchanger given in this application is also only a specific example. It should be understood that it is not limited to this. The evaporator before dewaxing, the evaporator after dewaxing and / or the liquid waste heat evaporator may also be other heat exchangers known in the art.

[0034] In one embodiment, please combine Figure 2The methanol synthesis and dewaxing coupled waste heat power generation system also includes a dewaxing device, which includes a methanol synthesis reactor 1, a first heat exchanger 2, a dewaxing device 4, a second heat exchanger 7, a methanol separator 8 and a methanol expansion tank 9. The methanol synthesis reactor A, the first heat exchanger 2, the pre-dewaxing evaporator 3 and the dewaxing device 4 are connected in sequence, the gas outflow channel 20 of the dewaxing device 4, the post-dewaxing evaporator 5, the second heat exchanger 7, the methanol separator 8 and the methanol expansion tank 9 are connected in sequence, and the liquid outflow channel 15 of the dewaxing device 4 is connected to the methanol expansion tank 9. Furthermore, the methanol synthesis dewaxing process of the methanol synthesis dewaxing coupled waste heat power generation system is as follows: the process gas 13 coming out of the methanol synthesis reactor 1 is cooled to 120-160°C by the first heat exchanger 2, and the cooled process gas 14 is passed through the pre-dewaxing evaporator 3 to recover the waste heat by the heat exchanger 19 (refrigerant R245fa) and cooled to 80-130°C before entering the dewaxing device 4 for dewaxing to remove the C40 and below polycarbon paraffin components in the crude methanol. The process gas 20 at the outlet of the gas outflow channel of the dewaxing device 4 is passed through the post-dewaxing evaporator 5 to recover the waste heat by the heat exchanger 21 and cooled to 45-60°C, and the cooled process gas 16 is cooled to 40-45°C by the second heat exchanger 7 and then enters the methanol separator 8 to complete the gas-liquid separation of the product. At the same time, considering the partial heat recovery of the liquid methanol 15 at the bottom of the dewaxing device 4, the heat exchanger 22 recovers the waste heat through the liquid waste heat evaporator 6 and cools down to 40-50°C, and the cooled liquid methanol 17 is mixed with the liquid methanol 18 at the bottom of the methanol separator 8 and enters the methanol expansion tank 9. In this embodiment, the heat exchanger 19, the heat exchanger 21, and the heat exchanger 22 are all the same heat exchanger, and the different numbers are only for the convenience of description. Furthermore, the methanol synthesis dewaxing coupled waste heat power generation system of the present application can be understood as including a dewaxing channel and a waste heat recovery channel respectively. The dewaxing channel includes a methanol synthesis reactor 1, a first heat exchanger 2, a dewaxing device 4, a second heat exchanger 7, a methanol separator 8 and a methanol expansion tank 9, a pre-dewaxing evaporator 3, a post-dewaxing evaporator 5 and a liquid waste heat evaporator 6, and the waste heat recovery channel includes a pre-dewaxing evaporator 3, a post-dewaxing evaporator 5 and a liquid waste heat evaporator 6 and a waste heat utilization device A. The pre-dewaxing evaporator 3, the post-dewaxing evaporator 5 and the liquid waste heat evaporator 6 have independent process gas flow channels and heat exchange channels for heat exchange agent circulation. The dewaxing channel is used for dewaxing, and the waste heat recovery channel is used for waste heat recovery before and after dewaxing and for power generation. In one embodiment, the first heat exchanger 2 and the second heat exchanger 7 are water-cooled heat exchangers. Of course, it is also possible to further utilize the heat of the first heat exchanger 2 and the second heat exchanger 7 by using a heat exchanger to exchange heat with the first heat exchanger and the second heat exchanger 7 and connecting them to a waste heat utilization device.That is, the heat exchange channels of the first heat exchanger 2 and the second heat exchanger 7 can also be connected to the waste heat utilization device. In specific applications, the influence of the temperature gradient needs to be considered. The absorption temperature of the second heat exchanger is relatively low, and the absorption temperature of the first heat exchanger is relatively high. It is necessary to consider it as appropriate when connecting the positions. In the illustrated embodiments given in this application, the waste heat absorbed by the first heat exchanger 2 and the second heat exchanger 7 is not considered. It should be understood that it should not be used as a limitation on the protection scope of this application. Regardless of whether the waste heat absorbed by the first heat exchanger 2 and the second heat exchanger 7 is utilized, it should be within the protection scope of this application.

[0035] In one embodiment, the methanol synthesis dewaxing coupled waste heat power generation system further includes a working fluid pump 12 (also called a liquid pump), or in other words, the dewaxing channel includes a working fluid pump 12, and the output end of the condenser 11 is connected to the input end of the pre-dewaxing evaporator 3 and the input end of the post-dewaxing evaporator 5 through the working fluid pump 12. Preferably, the output end of the condenser 11 is connected to the input end of the pre-dewaxing evaporator 3 through the working fluid pump 12 and the post-dewaxing evaporator 5 in sequence. More preferably, the output end of the condenser 11 is also connected to the input end of the pre-dewaxing evaporator 3 through the working fluid pump 12 and the liquid waste heat evaporator 6 in sequence. In this way, by providing the working fluid pump 12, the liquid heat exchanger cooled by the condenser can be better input into the liquid waste heat evaporator 6 or the post-dewaxing evaporator 5, and the flow rate can be controlled as needed. Furthermore, in order to better control the heat exchange effect of each evaporator, in a specific embodiment, the input and output ports of the pre-dewaxing evaporator 3, the post-dewaxing evaporator 5 and the liquid waste heat evaporator 6 are respectively provided with temperature probes. The temperature probes can better monitor the heat exchange conditions of each evaporator, thereby facilitating further control of the flow rate.

[0036] Furthermore, the power generation method of the methanol synthesis dewaxing coupled waste heat power generation system of the present application specifically includes: the heat exchange medium that absorbs the waste heat of the process gas in the evaporator 3 before dewaxing becomes a saturated or superheated refrigerant vapor 24 and enters the turbine 10, converting the thermal energy of the refrigerant vapor 24 into mechanical energy, while driving power generation and outputting electrical energy to the outside; the superheated refrigerant vapor 25 at the outlet of the turbine 10 enters the condenser 11 and is condensed into a liquid after being cooled by circulating water, Figure 2In the embodiment, the condenser 11 has a corresponding circulating water inlet CWS and a circulating water outlet CWR, and then the liquid heat exchanger is pressurized by a working fluid pump 12 (also called a liquid pump) and is divided into two streams: one stream of liquid heat exchanger 21 enters the post-dewaxing evaporator 5, and recovers the process waste heat of the process gas 20 at the outlet of the dewaxing device 4 through evaporation and heat absorption of the heat exchanger 21; the other stream of liquid heat exchanger 22 enters the liquid waste heat evaporator 6, and recovers the process waste heat of the liquid methanol 15 at the bottom outlet of the dewaxing device 4 through evaporation and heat absorption of the heat exchanger 22. Specifically, they flow into the liquid waste heat evaporator 6 and the post-dewaxing evaporator 5 respectively through the three-way ORC. The gas-liquid two-phase heat exchanger 26 at the outlet of the evaporator 5 after dewaxing is combined with the gas-liquid two-phase heat exchanger 23 at the outlet of the liquid waste heat evaporator 6 to form a gas-liquid two-phase heat exchanger 19 and enter the evaporator 3 before dewaxing. The liquid phase heat exchanger in the heat exchanger 19 evaporates and absorbs heat to recover the process waste heat of the process gas 14. The saturated or superheated heat exchanger steam 24 at the outlet of the evaporator 3 before dewaxing returns to the turbine 10 for circulation.

[0037] The above-mentioned methanol synthesis and dewaxing coupled waste heat power generation system can utilize the waste heat of the gas after dewaxing through a heat exchanger to recover the waste heat, and further utilize the waste heat through a waste heat utilization device A. In this way, by adopting a turbine 10, the waste heat before and after methanol synthesis and dewaxing can be better recovered and utilized for power generation, thereby reducing energy waste in the methanol synthesis and dewaxing process, reducing energy consumption, and having relatively good energy-saving and environmental protection properties.

[0038] In a third aspect, the present application also provides a method for power generation using waste heat from methanol synthesis and dewaxing, which uses the methanol synthesis and dewaxing coupled waste heat power generation system as described in any of the above embodiments to generate electricity and output electrical energy.

[0039] Specifically, the method of using methanol synthesis dewaxing coupled with waste heat power generation specifically includes a dewaxing process and a waste heat power generation method, wherein the dewaxing process includes: the process gas 13 coming out of the methanol synthesis reactor 1 is cooled to 120-160°C by the first heat exchanger 2, and the cooled process gas 14 is passed through the pre-dewaxing evaporator 3 to recover the waste heat by the heat exchanger 19 (refrigerant R245fa) and cooled to 80-130°C before entering the dewaxing device 4 for dewaxing to remove C40 and below polycarbon paraffin components in crude methanol. The process gas 20 at the outlet of the gas outflow channel of the dewaxing device 4 is passed through the post-dewaxing evaporator 5 to recover the waste heat by the heat exchanger 21 and cooled to 45-60°C, and the cooled process gas 16 is cooled to 40-45°C by the second heat exchanger 7 and then enters the methanol separator 8 to complete the gas-liquid separation of the product. At the same time, considering partial heat recovery of the liquid methanol 15 at the bottom of the dewaxing device 4, the heat exchanger 22 recovers the waste heat through the liquid waste heat evaporator 6 and cools it to 40-50°C. The cooled liquid methanol 17 is mixed with the liquid methanol 18 at the bottom of the methanol separator 8 and enters the methanol expansion tank 9. The gas phase part of the liquid methanol 17 is recycled. The liquid phase part of the methanol expansion tank 9 is crude methanol, which can be subsequently entered into the methanol distillation system, and the gas phase part can be used as expansion gas for subsequent process treatment.

[0040] The waste heat power generation method includes: the heat exchange medium that absorbs the waste heat of the process gas in the evaporator 3 before dewaxing becomes a saturated or superheated refrigerant vapor 24 and enters the turbine 10, converting the thermal energy of the refrigerant vapor 24 into mechanical energy, while driving power generation and outputting electrical energy to the outside; the superheated refrigerant vapor 25 at the outlet of the turbine 10 enters the condenser 11 and is condensed into liquid after being cooled by circulating water, Figure 2 In the embodiment, the condenser 11 has a corresponding circulating water inlet CWS and a circulating water outlet CWR. Then, the liquid heat exchanger is pressurized by the working fluid pump 12 (also called a liquid pump) and is divided into two streams: one stream of liquid heat exchanger 21 enters the post-dewaxing evaporator 5, and recovers the process waste heat of the process gas 20 at the outlet of the dewaxing device 4 by evaporating and absorbing heat of the heat exchanger 21, and the other stream of liquid heat exchanger 22 enters the liquid waste heat evaporator 6, and recovers the process waste heat of the liquid methanol 15 at the bottom outlet of the dewaxing device 4 by evaporating and absorbing heat of the heat exchanger 22. The gas-liquid two-phase heat exchanger 26 at the outlet of the post-dewaxing evaporator 5 and the gas-liquid two-phase heat exchanger 23 at the outlet of the liquid waste heat evaporator 6 are combined into a gas-liquid two-phase heat exchanger 19 and enter the pre-dewaxing evaporator 3, and recover the process waste heat of the process gas 14 by evaporating and absorbing heat of the liquid phase heat exchanger in the heat exchanger 19. The saturated or superheated heat exchanger steam 24 at the outlet of the pre-dewaxing evaporator 3 returns to the turbine 10 for circulation.

[0041] The above-mentioned method of utilizing methanol synthesis and dewaxing coupled with waste heat for power generation adopts the above-mentioned methanol synthesis and dewaxing coupled with waste heat for power generation system to drive power generation and output electric energy to the outside, which can better recycle the waste heat before and after methanol synthesis and dewaxing and use it for power generation, thereby reducing energy waste in the methanol synthesis and dewaxing process, can reduce energy consumption, and has relatively good energy saving and environmental protection.

[0042] It should be further explained that the methanol synthesis dewaxing coupled waste heat recovery system, power generation system and power generation method provided in this application provide a dewaxing and waste heat recovery coupled power generation system for the current operation status of the existing methanol synthesis technology, eliminating the traditional air cooler, which can avoid the influence of weather temperature difference on medium heat exchange to a certain extent, and complete the dewaxing in the methanol synthesis loop while recovering the system waste heat and using it for power generation, thereby improving the economic benefits of the methanol synthesis device. Moreover, the biggest drawback of the current traditional dewaxing device is that the heat energy is not well utilized. The conventional design adopts an air-cooled + water-cooled cooling system, and the cooling equipment consumes a large amount of utilities, which increases the operating cost; the air cooler is greatly affected by the ambient temperature, and the circulating water consumption of the water cooler after the air cooler in high temperature weather increases significantly. The optimization of the present invention is mainly based on the perspective of waste heat recovery. Considering that the process gas at the outlet of the dewaxing device and the liquid phase temperature of the dewaxing device are relatively high, waste heat recovery can be carried out together with the process gas at the outlet of the methanol thermostat. The operating temperature of the process gas after the waste heat is recovered is 80-130°C, which can remove the C40 and below long-chain hydrocarbon paraffin components in crude methanol. Waste heat recovery utilizes the principle of organic Rankine cycle process to convert thermal energy into mechanical energy, which is finally converted into electrical energy through a generator, with high energy conversion efficiency. The methanol synthesis dewaxing coupled waste heat power generation process provided in this application also has the following advantages:

[0043] 1. The methanol synthesis dewaxing coupled waste heat power generation process is a process technology that integrates dewaxing process and heat energy recovery power generation. At the same time, it considers recovering waste heat from the process gas at the outlet of the dewaxing device, part of the heat energy of liquid methanol and the process gas entering the dewaxing device, and uses the principle of organic Rankine cycle process to convert the recovered heat energy into mechanical energy, and then converts the mechanical energy into electrical energy through a generator.

[0044] 2. After the synthesis gas from the methanol synthesis reactor is cooled to 120-160°C by heat exchange, it is cooled to 80-130°C by the evaporator 3 of the waste heat recovery power generation circuit, and enters the dewaxing device to remove the C40 and below long-chain hydrocarbon paraffin components in the crude methanol;

[0045] 3. The process gas at the outlet of the dewaxing device is cooled to 45-55°C through the dewaxing evaporator 5 of the waste heat recovery power generation circuit, and the crude methanol at the outlet of the dewaxing device is cooled to 45-55°C through the liquid waste heat evaporator 5 of the waste heat recovery power generation circuit;

[0046] 4. The process gas 14 is cooled by grades and enters the dewaxing device and the methanol separator at low temperature, which improves the dewaxing effect.

[0047] 5. During the graded cooling of the process gas 14, the pre-dewaxing evaporator 3 for recovering waste heat is connected in series with the dewaxing device 4, the dewaxing device 4 is connected in series with the post-dewaxing evaporator 5 and the liquid waste heat evaporator 6, and the post-dewaxing evaporator 5 and the liquid waste heat evaporator 6 are connected in parallel.

[0048] 6. The organic Rankine cycle process is used to convert the heat energy recovered from the waste heat of the methanol synthesis process gas into mechanical energy, which is finally converted into electrical energy through a generator. The energy conversion efficiency is high and has good economic benefits.

[0049] The present application achieves at least the following advantages: 1) Compared with traditional schemes, the methanol synthesis dewaxing coupled waste heat power generation process of the present invention can recover process waste heat for power generation, reduce device energy consumption, and have good economic benefits; 2) The scheme of graded cooling and low-temperature dewaxing is adopted. Compared with the traditional dewaxing scheme, the operating temperature of the dewaxing device is lower, which improves the dewaxing effect, reduces the impact of by-product paraffin (higher alkanes) on the crude methanol heat exchanger, and reduces public utility consumption; 3) Compared with the traditional dewaxing scheme, the air cooler can be omitted, which can avoid the impact of weather temperature differences to a certain extent.

[0050] In order to further illustrate the economic benefits brought by the present application, specific examples are given below for further explanation. 1. Specific embodiment 1:

[0052] like Figure 2 The figure shows a flow diagram of a methanol synthesis dewaxing coupled waste heat power generation method, and takes a single methanol synthesis unit with a methanol synthesis capacity of 2.2 million tons / year as an example to illustrate the economic benefits of the present invention.

[0053] The process gas 13 coming out of the methanol synthesis reactor 1 is cooled to 126°C through the first heat exchanger 2. The cooled process gas 14 is passed through the pre-dewaxing evaporator 3 to recover the waste heat by the heat exchanger 19 (refrigerant) and is cooled to 85°C before entering the dewaxing device 4 for dewaxing. The temperature of the process gas 20 at the outlet of the dewaxing device is ~85°C. The refrigerant uses non-flammable refrigerant R245fa as an intermediate medium to extract heat, and the temperature of the process gas 16 is reduced to 50°C before entering the heat exchanger 7; the heat of the liquid phase of the dewaxing device 4 is recovered, and the same refrigerant heat extraction scheme is used to reduce the liquid phase outlet temperature of the dewaxing device from 85°C to 50°C.

[0054] Considering that the process gas at the outlet of the dewaxer 4 and the liquid phase temperature of the dewaxer are relatively high (85°C), waste heat recovery can be carried out simultaneously with the process gas 14 at the outlet of the first heat exchanger 2 at 126°C. The Rankine cycle is used to convert thermal energy into mechanical energy, and the thermal energy is converted into mechanical energy through the turbine expander 10, and then the mechanical energy is converted into electrical energy, with a final power generation of 8400KW. The energy conversion efficiency of this technology is relatively high, and the isentropic efficiency is about 80%. Therefore, the process gas 16 at the outlet of the dewaxer 4 is cooled to 50°C by using R245fa, and then enters the second heat exchanger 7 to cool to 40°C, and then enters the methanol separator 8 to complete the gas-liquid separation of the product. The liquid methanol 15 at the outlet of the dewaxer 4 is cooled to 50°C by R245fa and mixed with the liquid phase of the methanol separator 8 before entering the methanol expansion tank 9.

[0055] The evaporator of this embodiment uses 21 high-efficiency heat exchangers, and initially uses a finned shell and tube heat exchanger. Methanol synthesis gas enters the evaporator shell side, and refrigerant R245fa enters the evaporator tube side. The generator set uses a 1500rpm single-stage turbine expander + (direct drive) 1500rpm explosion-proof DC excitation generator.

[0056] The benefits of waste heat utilization are as follows:

[0057] (1) Annual net power generation and emission reduction benefits of the waste heat power generation system

[0058] 1) Annual waste heat power generation income

[0059] ① Annual power generation of expander

[0060] The power of the expander is 8.4MW. Considering the bearing loss of 5% and the wheel loss of 3%, then:

[0061] Net power generation: 8.4×0.92=7.73MW

[0062] Power generation per hour (assuming motor efficiency of 97%): 7.5MW

[0063] Annual power generation income: 7.5x8000x1000=59.97 million kWh / year

[0064] ② Annual power consumption of expander and waste heat power generation system

[0065] Power consumption: 1275kw

[0066] Annual power consumption: 1275x8000=10.192 million kWh / year

[0067] ③ Net power generation income of waste heat power generation system per year

[0068] Annual net power generation: 5997-1019.2=49.78 million kWh / year

[0069] Annual power generation income: 0.39x4978=19.41 million yuan.

[0070] 2) Annual carbon emission reduction benefits

[0071] ① Total amount of standard coal saved each year (due to power generation):

[0072] 4978x0.36=14934 tons / year

[0073] ②The total amount of CO2 emissions reduced each year (due to power generation):

[0074] 14934x2.7=40322 tons / year

[0075] ③ Carbon index trading equity income obtained from reducing CO2 emissions each year

[0076] 40322x50=2.016 million yuan / year

[0077] The income from waste heat power generation is 19.41 million yuan / year, the income from carbon emission reduction is 2.016 million yuan / year, and the total income is 21.426 million yuan / year.

[0078] (2) Waste heat recovery consumption cost

[0079] The waste heat recovery system mainly consumes circulating water, and the annual cost of circulating water consumption is 0.38x3500=10.64 million yuan.

[0080] (3) Economic benefits of waste heat recovery

[0081] The income from waste heat utilization is 21.426 million yuan / year, and after deducting the circulating water consumption cost of 10.64 million yuan / year, the net profit is 10.786 million yuan / year.

[0082] Compared with the traditional methanol synthesis dewaxing process, the investment in the 2.2 million tons / year methanol synthesis dewaxing coupled waste heat power generation process increases by ~32 million yuan. The investment cost can be recovered in 3 years, with significant economic benefits.

[0083] It can be seen from the above that the methanol synthesis dewaxing coupled waste heat power generation method provided in the present application can make good use of waste heat for power generation, has significant economic benefits and is highly environmentally friendly.

[0084] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. It should be noted that "in one embodiment", "for example", "for example", etc. in this application are intended to illustrate the present application, rather than to limit the present application. The above-described embodiments only express several implementation methods of the present application, and the description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the patent application. It should be pointed out that for a person of ordinary skill in the art, without departing from the concept of the present application, several variations and improvements can also be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be subject to the attached claims.

Claims

1. A methanol synthesis dewaxing coupled waste heat recovery system, characterized in that: It includes a pre-dewaxing evaporator, a post-dewaxing evaporator and a waste heat utilization device. The pre-dewaxing evaporator is used to be connected to the inlet channel of the dewaxing device and is used to absorb the heat of the gas before dewaxing. The post-dewaxing evaporator is used to be connected to the gas outflow channel of the dewaxing device and is used to absorb the heat of the gas after dewaxing. The waste heat utilization device is connected to the pre-dewaxing evaporator and the post-dewaxing evaporator through a pipeline, and a heat exchanger is provided in the pipeline.

2. The methanol synthesis dewaxing coupled waste heat recovery system according to claim 1, characterized in that: It also includes a liquid waste heat evaporator, which is connected to the waste heat utilization device through a pipeline. The liquid waste heat evaporator is used to be connected to the liquid outflow channel of the dewaxing device and to absorb the heat of the liquid after dewaxing.

3. The methanol synthesis dewaxing coupled waste heat recovery system according to claim 2, characterized in that: The waste heat utilization device has an output end and a recovery end opposite to each other; The output end of the waste heat utilization device is connected to the recovery end of the waste heat utilization device through the liquid waste heat evaporator and the pre-dewaxing evaporator in sequence, and / or the output end of the waste heat utilization device is connected to the recovery end of the waste heat utilization device through the post-dewaxing evaporator and the pre-dewaxing evaporator in sequence.

4. The methanol synthesis dewaxing coupled waste heat recovery system according to claim 3, characterized in that: The waste heat utilization device is a heat exchange device, a heat-to-work conversion device or a heat pump system.

5. A methanol synthesis dewaxing coupled waste heat power generation system, characterized in that: It includes a methanol synthesis dewaxing coupled waste heat recovery system as described in any one of claims 1 to 3, wherein the waste heat utilization device includes a turbine and a condenser, the input end of the turbine is connected to the output end of the evaporator before dewaxing and the output end of the evaporator after dewaxing through a pipeline, the condenser has a relative input end and output end, the output end of the turbine is connected to the input end of the condenser, and the output end of the condenser is connected to the input end of the evaporator before dewaxing and the input end of the evaporator after dewaxing through pipelines, respectively, and the turbine is used to convert the thermal energy of the heat exchanger into mechanical energy, while driving power generation and outputting electrical energy to the outside.

6. The methanol synthesis dewaxing coupled waste heat power generation system according to claim 5, characterized in that: The turbine is an organic working fluid turbine expander.

7. The methanol synthesis dewaxing coupled waste heat power generation system according to claim 6, characterized in that: The turbine includes a single-stage turbine expander and a direct-drive explosion-proof DC excitation generator; And / or, the heat exchange agent is refrigerant R245fa.

8. The methanol synthesis dewaxing coupled waste heat power generation system according to claim 7, characterized in that: The pre-dewaxing evaporator, the post-dewaxing evaporator and / or the liquid waste heat evaporator are finned shell and tube heat exchangers.

9. The methanol synthesis dewaxing coupled waste heat power generation system according to claim 5, characterized in that: The methanol synthesis and dewaxing coupled waste heat power generation system also includes a dewaxing device, which includes a methanol synthesis reactor, a first heat exchanger, a dewaxing device, a second heat exchanger, a methanol separator and a methanol expansion tank. The methanol synthesis reactor, the first heat exchanger, the evaporator before dewaxing and the dewaxing device are connected in sequence, the gas outflow channel of the dewaxing device, the evaporator after dewaxing, the second heat exchanger, the methanol separator and the methanol expansion tank are connected in sequence, and the liquid outflow channel of the dewaxing device is connected to the methanol expansion tank.

10. A method for generating electricity by coupling waste heat from methanol synthesis and wax removal, characterized in that: The methanol synthesis dewaxing coupled waste heat power generation system as described in any one of claims 5 to 9 is used to generate electricity and output electrical energy.

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