Method and system for comprehensive utilization of waste heat and pressure energy in chemical process

Abstract

The present application relates to a method and system for comprehensive utilization of waste heat and pressure energy in a chemical process, wherein the method comprises: (a1) heating water to produce water vapor by heat exchange using heat energy from a liquid phase of a material stream produced by the chemical process; (a2) converting pressure energy from a gas phase of the material stream produced by the chemical process into mechanical energy; (b) boosting the pressure of the water vapor, wherein the energy for boosting the pressure of the water vapor is at least partially from the mechanical energy and / or at least partially from electrical energy, and optionally, the mechanical energy is at least partially converted into electrical energy. The method and system of the present application achieve systematic and collaborative utilization of reaction waste heat and pressure, improve the availability of low-grade heat energy, and achieve the matching of intermittent reaction and continuous energy recovery working conditions.

Description

Technical Field

[0001] This application belongs to the field of energy conservation and comprehensive energy utilization technology in chemical processes, specifically involving methods and systems for the comprehensive utilization of waste heat and pressure energy in chemical processes. Background Technology

[0002] Benzotriazole (BTA) is an important fine chemical product widely used in metal corrosion inhibition, surface treatment, and functional materials. Its industrial synthesis process typically takes place in a reactor under high temperature and pressure conditions. After the reaction, it requires depressurization, cooling, and subsequent separation and purification steps to complete the product preparation. This type of process is characterized by harsh reaction conditions and a high energy concentration at the end of the reaction.

[0003] In actual industrial operations, the synthesis of benzotriazole is mostly carried out in a batch operation mode. After the reaction is completed, the reaction system releases pressure from a high temperature and high pressure state in a short period of time, and then enters the depressurization and cooling stage. This makes the reaction stream exhibit obvious batch and strong fluctuation characteristics on a time scale, and its temperature, pressure and flow rate change significantly with the reaction cycle.

[0004] To address the significant energy generated at the end of the reaction, existing production facilities typically employ the following methods: First, pressure is released through a pressure-reducing valve, converting the pressure energy contained within the system into low-grade heat energy for direct consumption. Second, the reaction liquid is cooled using a cooling water system, directly dissipating the sensible heat released by the reaction liquid. These methods result in the ineffective recovery and utilization of the sensible heat and pressure energy generated during the reaction, leading to low energy utilization efficiency.

[0005] Furthermore, existing energy recovery and utilization equipment (such as flash steam generators, pressure energy recovery devices, steam compression or heat pump systems, etc.) is usually designed and operated under continuous and stable conditions. When intermittent reactive streams are directly introduced into these devices, it can easily cause fluctuations in operating conditions, unstable steam production, and frequent deviations from the design operating conditions of the equipment, increasing the risk of system operation and the difficulty of control.

[0006] To address the energy waste problem in the synthesis of benzotriazole, existing technologies have proposed solutions such as recovering sensible heat of the reaction by flash evaporation, recovering pressure energy by replacing pressure reducing valves with expanders, and improving the grade of low-grade heat energy through vapor compression or heat pump technology. However, these technologies are mostly localized optimizations for a single energy form or a single operating unit, lacking a systematic design for the entire reaction process.

[0007] Especially in the context of the intermittent operation of the benzotriazole synthesis reaction, existing technologies generally assume that the material flow conditions are continuous and stable, and fail to fully consider the actual working conditions of concentrated energy release and drastic fluctuations in material flow parameters after the reaction ends. This makes it difficult for related energy recovery technologies to operate stably and efficiently in practical applications.

[0008] Meanwhile, existing technologies typically design and operate the pressure energy recovery during the reaction decompression stage and the sensible heat recovery during the reaction liquid cooling stage separately. This fails to establish a functional connection between the two energy forms within the same system, preventing the pressure energy recovery results from directly participating in the process of upgrading the grade of low-grade thermal energy. This limits the further improvement of the overall energy recovery efficiency at the system level.

[0009] Therefore, from the perspective of the overall process and energy flow, the existing technology in the field of benzotriazole synthesis still has obvious technological gaps and deficiencies, such as the lack of continuous energy recovery system design for intermittent operation and the lack of a path for the synergistic utilization of waste heat and waste pressure.

[0010] Based on the existing technologies and their shortcomings, the comprehensive energy utilization of benzotriazole synthesis systems still faces the following key technical problems that urgently need to be solved: (1) Without changing the intermittent operation mode of the benzotriazole synthesis reaction itself, how to reasonably smooth the high temperature and high pressure reaction stream generated after the reaction is completed, so as to realize the transformation from intermittent reaction stream to continuous energy recovery operation mode; (2) How to simultaneously recover the pressure energy generated during the reaction decompression stage and the sensible heat released during the reaction liquid cooling stage at the system level, and avoid the separation of the two types of energy in time and space; (3) How to couple the pressure energy recovery process with the utilization process of low-grade thermal energy so that the pressure energy recovery result can directly participate in the grade improvement of low-grade steam, thereby stably outputting steam energy that can be directly used in the process system. (4) Under the premise of ensuring safe operation and process stability, how to construct an energy comprehensive utilization method and system that is suitable for the synthesis of benzotriazole, has good engineering applicability and modification feasibility.

[0011] (5) Although the existing technologies disclose the unit technologies of flash evaporation to recover heat, expander to recover pressure energy and steam compression to improve energy level, they do not address the characteristics of strong fluctuations in energy release under intermittent synthesis reaction conditions, nor do they design a coordinated path for waste heat and waste pressure, nor do they solve the matching problem between the two in terms of time scale and energy level. Summary of the Invention

[0012] The primary objective of this application is to overcome the mismatch between the intermittent reaction operation and the requirement for continuous and stable operation of energy recovery devices in the existing benzotriazole synthesis process. The application provides a method and system for comprehensive energy utilization in the benzotriazole synthesis system, aiming to achieve a smoothing of the high-temperature and high-pressure reaction stream generated after the reaction without changing the intermittent operation mode of the synthesis reaction itself, thereby realizing the transformation from intermittent reaction stream to continuous energy recovery operation.

[0013] Another objective of this application is to address the problem of the simultaneous failure to coordinate the utilization of reaction waste heat and depressurization residual pressure during the synthesis of benzotriazole. By constructing a coupled path for waste heat recovery and residual pressure recovery, the pressure energy during the depressurization stage and the low-grade heat energy released during the cooling stage can be coordinated and utilized in stages. The recovered low-grade energy can be stably converted into steam energy that can be directly used in the process system, thereby reducing the overall energy consumption of the benzotriazole production process.

[0014] A further objective of this application is to provide a system for implementing the above-described method. This system has a clear structure and high integration, and can be configured as a bypass unit of the existing benzotriazole synthesis unit. Under the premise of ensuring production safety and process stability, it has good engineering applicability and modification feasibility.

[0015] On the one hand, this application provides a method for comprehensive utilization of waste heat and waste pressure energy in chemical processes, the method comprising: (a1) The heat energy of the liquid phase of the material flow produced by the chemical process is used to heat water through heat exchange to generate water vapor; (a2) Converting the pressure energy of the gas phase of the material flow originating from a chemical process into mechanical energy; (b) Pressurize the water vapor. The energy that pressurizes the water vapor comes at least partially from mechanical energy and / or at least partially from electrical energy, optionally, at least partially of the mechanical energy is converted into electrical energy.

[0016] In some embodiments, the energy to pressurize the water vapor comes entirely from the mechanical energy; and if there is a surplus of mechanical energy, the excess mechanical energy is converted into electrical energy.

[0017] In some implementations, part of the energy that pressurizes the water vapor comes from mechanical energy and another part comes from electrical energy.

[0018] In some embodiments, the energy to pressurize the water vapor comes from electrical energy, and all the mechanical energy is converted into electrical energy.

[0019] In some embodiments, the chemical process is a benzotriazole synthesis reaction.

[0020] In some embodiments, the pressure energy of the gas phase is converted into mechanical energy by an expander.

[0021] In some embodiments, the steam pressure is increased by a compressor.

[0022] In some embodiments, the method further includes: (a01) conditioning the material stream produced by the chemical process prior to steps (a1) and (a2) to balance material and energy fluctuations.

[0023] In some embodiments, the method further includes: (a02) flash evaporating the material stream produced by the chemical process prior to steps (a1) and (a2).

[0024] In some embodiments, the method further includes: (a03) prior to steps (a1) and (a2), conditioning the material stream produced by the chemical process to balance material and energy fluctuations, and then flash evaporating the material stream produced by the chemical process.

[0025] In some embodiments, the method further includes: (c1) the gas phase being absorbed or further processed after pressure energy is converted into mechanical energy.

[0026] In some embodiments, the method further includes: (c2) using pressurized steam for internal needs of the chemical process or for external steam supply networks.

[0027] On the other hand, this application provides a comprehensive energy utilization system for waste heat and waste pressure in chemical processes, the system comprising: The waste heat recovery unit is configured to receive the liquid phase of the material stream produced from the chemical process and use the heat energy of the liquid phase to heat water through heat exchange to generate water vapor. The residual pressure recovery unit is configured to receive the gas phase of a material stream originating from a chemical process and convert the pressure energy of the gas phase into mechanical energy. A pressurization unit configured to receive the water vapor and pressurize the water vapor; Optional power generation device; Optional electric motor, The pressurization unit is connected to the residual pressure recovery unit and / or an optional electric motor, using the mechanical energy and / or optional electrical energy to drive the pressurization of the water vapor. The residual pressure recovery unit is connected to an optional power generation device to convert the mechanical energy into electrical energy.

[0028] In some embodiments, the system includes a preparation unit, wherein: The preparation unit includes a transition vessel configured to receive the material stream produced by the chemical process and configured to be in fluid communication with the waste heat recovery unit and the waste pressure recovery unit, respectively, to provide liquid and gas phases to the waste heat recovery unit and the waste pressure recovery unit, respectively; or The preparatory unit includes a flash evaporator configured to receive a material stream produced by a chemical process, flash-treat the material stream in the flash evaporator, and is configured to be fluidly connected to a waste heat recovery unit and a waste pressure recovery unit, respectively, to provide liquid and gas phases to the waste heat recovery unit and the waste pressure recovery unit, respectively; or The preparation unit includes a transition vessel and a flash evaporator. The transition vessel is configured to receive the material stream produced by the chemical process. The flash evaporator is configured to be in fluid communication with the transition vessel so that the material stream produced by the chemical process is flash-treated in the flash evaporator. It is also configured to be in fluid communication with the waste heat recovery unit and the waste pressure recovery unit respectively, so as to provide the waste heat recovery unit and the waste pressure recovery unit with liquid phase and gas phase respectively.

[0029] In some embodiments, the flash evaporator is preferably an adiabatic flash evaporator.

[0030] In some embodiments, the waste heat recovery unit includes a heat exchange device, which is preferably a partition wall heat exchanger, a cooling vessel equipped with coils, a heat exchange jacket, or a hot water circuit.

[0031] In some embodiments, the residual pressure recovery unit includes an expander.

[0032] In some embodiments, the booster unit includes a compressor.

[0033] In some embodiments, the residual pressure recovery unit includes an expander, the pressure boosting unit includes a compressor, and the output shaft of the expander is drively connected to the input shaft of the compressor.

[0034] In some embodiments, the system includes a power generation device, the booster unit includes a compressor, and the power generation device is connected to the drive mechanism of the compressor.

[0035] Compared with the energy-intensive methods of cooling and depressurization used in the existing synthesis of benzotriazole, this application has at least the following advantages: (1) Realize the synergistic utilization of waste heat and waste pressure in the system, and break through the energy efficiency bottleneck of the traditional single recovery method.

[0036] This application no longer treats reaction waste heat and reaction waste pressure as independent recovery objects, but instead couples them functionally at the system level. This allows the pressure recovered during the reaction depressurization stage to participate in the process of improving the grade of reaction waste heat in the form of mechanical work, thereby establishing a synergistic utilization path of "waste pressure supporting waste heat upgrading". This fundamentally changes the energy utilization mode of "waste heat loss and waste pressure dissipation" in traditional processes and improves the overall energy recovery efficiency of the system. Figure 2 This demonstrates different pathways for utilizing residual pressure in the reaction. Figure 3 This demonstrates the energy pathway by which waste heat and waste pressure from the reaction work together to enhance the steam energy level.

[0037] (2) Improve the availability of low-grade heat energy through the steam carrier recovery path.

[0038] This application utilizes controlled heat exchange and flash evaporation to convert the sensible heat carried by the reaction liquid phase into the latent heat of phase change of low-grade steam. This allows the waste heat from the reaction to be centrally recovered in a unified and controllable steam carrier form, avoiding the problems of heat dispersion and difficulty in utilization in direct cooling methods. This provides a good engineering foundation for subsequent steam compression and pressurization and steam system grid connection.

[0039] (3) Combined with de-temperature control, steam quality improvement and steam quantity optimization are achieved, reducing dependence on external high-grade energy.

[0040] This application controls the superheat of the compressed steam by supplementing a desuperheating working fluid during the steam compression process, so that the sensible heat of superheat generated during compression is converted into the latent heat of vaporization of the desuperheating working fluid. Thus, without introducing an additional high-grade heat source, it achieves synergistic optimization of increasing the steam pressure level and the usable steam mass flow rate, and significantly reduces the dependence on externally supplied steam and externally supplied power during the steam grade improvement process.

[0041] (4) Shorten the energy conversion path and reduce irreversible losses and additional heat load of the system.

[0042] In a preferred embodiment, this application directly drives the booster unit through an expander, so that the pressure energy recovered during the reaction depressurization stage can directly participate in the upgrading process of low-grade steam without intermediate electrical energy conversion, thereby reducing irreversible losses caused by multiple energy form conversions. At the same time, due to the improvement of energy utilization efficiency, the additional heat dissipation requirements of the system are reduced accordingly, which helps to reduce the power load and cooling load simultaneously and improve the overall operating efficiency of the system.

[0043] (5) Achieve working condition matching between intermittent reaction and continuous energy recovery, and improve the feasibility of the project.

[0044] This application buffers and shapes the release of materials and energy at the end of the batch synthesis reaction by setting up a transition unit, so that energy recovery processes such as flash evaporation, expansion and vapor compression can operate continuously under near steady-state conditions, avoiding the instability caused by reaction load fluctuations and improving the feasibility of long-term stable operation of the system under industrial conditions.

[0045] (6) At the system level, the consumption of steam, electricity and cooling is reduced simultaneously, demonstrating significant comprehensive economic benefits. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the process flow of a method and system for comprehensive utilization of waste heat and waste pressure energy in a chemical process according to one embodiment of this application. Figure 2 This is a schematic diagram comparing two paths for utilizing residual pressure. Figure 3 This is a schematic diagram of the waste heat and waste pressure co-utilization path.

[0047] Figure label: 1-Synthesis vessel; 2-Transition vessel; 3-Adiabatic flash evaporator; 4-Expander; 5-Cooling vessel; 6-Compressor; 7-Electric motor; 8-Power generation unit; A-Reactant; B-Synthesis liquid; D-Flash vapor phase; E-Tail gas; F-Flash liquid phase; G-Cooling material; H-Water; I-Low-grade steam; J-Process steam; K-Spray water; ①-Example 1; ②Example 2 Detailed Implementation

[0048] The "range" disclosed herein is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified in this application, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0050] Unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0051] In this application, unless otherwise specified or there is no inherent sequential relationship, all steps mentioned herein may be performed sequentially or randomly, preferably sequentially, but some steps may also be performed in parallel. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc., and it is also possible that (c) is performed in parallel with (a) or (b).

[0052] In this application, unless otherwise specified, the terms "comprising" and "including" as used herein are open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0053] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0054] In this description, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0055] Unless otherwise specified, percentages (%), ppm, or parts are all expressed by weight.

[0056] Unless otherwise specified, the term "a" as used in this specification means "at least one".

[0057] In the description of this article, "fluid connectivity" means that a fluid (such as gas, liquid, gas-liquid mixture, gas-solid mixture, solid-liquid mixture, or gas-solid-liquid mixture) can flow from one component or part to another. It indicates the connection relationship and relative positional relationship between the two components or parts, but does not mean that there is always a fluid flow between the two components or parts. For example, there may be valves on the pipeline between the two components or parts to control the flow of fluid or prevent it from flowing.

[0058] In this description, "upstream" and "downstream" refer to the direction of fluid flow in the device and process. For any two fluid-connected components or parts in the device and process, the component or part through which the fluid flows first is upstream, and the component or part through which the fluid flows later is downstream.

[0059] Although this article will mainly describe the method and system for comprehensive utilization of waste heat and pressure energy in chemical processes in conjunction with the synthesis of benzotriazole, it will be easy to understand from reading this article that the method and system described are also applicable to other chemical processes with available waste heat and pressure, including chemical reactions, processing, treatment and other processes, which typically generate high-temperature and / or high-pressure materials.

[0060] The following description, in conjunction with the accompanying drawings, illustrates the system and method for the comprehensive utilization of waste heat and waste pressure energy from chemical processes.

[0061] (I) System

[0062] The system for the comprehensive utilization of waste heat and waste pressure energy in chemical processes, as described in this application, includes: an optional preparatory unit, a waste heat recovery unit, a waste pressure recovery unit, a booster unit, an optional power generation device, and an optional electric motor.

[0063] like Figure 1 As shown, in an exemplary system, the system includes a preparatory unit comprising a transition vessel 2 and a flash vessel, such as an adiabatic flash vessel 3; a residual pressure recovery unit comprising an expander 4; a residual heat recovery unit comprising a heat exchange device, such as a cooling vessel 5; and a pressurization unit comprising a compressor 6.

[0064] To illustrate the source of material flows with unrecovered waste heat and / or waste pressure, Figure 1 Synthesis vessel 1 is also illustrated. As shown in the figure, in a preferred embodiment, transition vessel 2 is disposed between synthesis vessel 1 and flash vessel (e.g., adiabatic flash vessel 3) to temporarily store and condition or smooth the high-temperature and high-pressure reaction stream (more generally referred to as material stream) discharged after the synthesis reaction is completed. Through volume buffering and liquid level adjustment, the intermittently discharged reaction stream is transformed into a continuous and stable feeding state, thereby balancing material and energy fluctuations and providing stable material and energy boundary conditions for the subsequent continuously operating energy recovery unit.

[0065] like Figure 1 As shown, the adiabatic flash evaporator 3 is fluidly connected to the transition vessel 2 and is used to perform depressurization flash evaporation on the reaction stream after the working condition has been smoothed. Under the condition of not introducing an external heat source, a portion of the liquid phase in the reaction stream undergoes phase change vaporization, thereby forming a liquid stream and a gaseous stream carrying pressure energy.

[0066] Systems excluding the preparatory unit, or including only the transition vessel 2, or only the flash evaporator, are also included within the scope of this application, but preferably include the transition vessel 2 or the flash evaporator, more preferably including both the transition vessel 2 and the flash evaporator. Without the preparatory unit, the material stream originating from the chemical process is simply the material stream produced by the chemical process, such as the reaction stream from the synthesis vessel 1, with the gas phase passed to the residual pressure recovery unit and the liquid phase passed to the waste heat recovery unit. With only the transition vessel 2, the material stream originating from the chemical process is also the material stream produced by the chemical process, such as the reaction stream from the synthesis vessel 1. In this case, the transition vessel 2 is in fluid communication with the synthesis vessel 1, receiving the reaction stream from the synthesis vessel 1. After conditioning in the transition vessel 2, the gas phase of the reaction stream is passed to the residual pressure recovery unit, and the liquid phase is passed to the waste heat recovery unit. In the case where only a flash evaporator is included, the flash evaporator is in fluid communication with the synthesis vessel 1 and receives the reaction stream from the synthesis vessel 1. The reactants are flashed in the flash evaporator, producing a flash liquid phase (also referred to as the liquid phase of the material stream originating from the chemical process) and a flash vapor phase (also referred to as the gas phase of the material stream originating from the chemical process). The gas phase is fed into the residual pressure recovery unit, and the liquid phase is fed into the waste heat recovery unit. In the case where both a transition vessel 2 and a flash evaporator are included, as follows... Figure 1 As shown, the reaction stream from synthesis vessel 1 enters transition vessel 2, and then enters flash vessel for flash evaporation, generating flash liquid and flash vapor phases. The vapor phase is fed into a residual pressure recovery unit, and the liquid phase is fed into a waste heat recovery unit. Preferably, both transition vessel 2 and flash vessel are included. This embodiment enables continuous recovery of waste heat and residual pressure, unaffected by intermittent chemical engineering (such as chemical reactions).

[0067] The expander 4 of the residual pressure recovery unit can be connected to the depressurization line of the synthesis vessel 1 (in the absence of a preparatory unit), or to the depressurization line of the transition vessel 2 (in the absence of a flash evaporator), or to the adiabatic flash evaporator 3 (which may or may not have a transition vessel 2, but preferably does), to perform work on the expansion of the gas phase generated during flash evaporation or depressurization, converting the pressure energy contained in the gas phase into mechanical energy output. In a preferred embodiment, such as Figure 1 As shown, the system includes a preparatory unit, which includes a transition vessel 2 and a flash vessel, with an expander 4 connected to the flash vessel (e.g., an adiabatic flash vessel 3).

[0068] like Figure 1As shown, the cooling vessel 5 of the waste heat recovery unit is connected to the liquid phase outlet of the adiabatic flash evaporator 3, used to further cool the liquid phase stream after flash evaporation, and under controlled pressure conditions, transfer the sensible heat in the liquid phase stream to low-grade steam in the form of latent heat of phase change, thereby realizing the steam recovery of reaction waste heat. The cooling vessel 5 can be equipped with a coil, and water (preferably softened water) is introduced into the coil. While cooling the high-temperature liquid phase material in the cooling vessel 5, the water is heated and vaporized, and then enters the compressor 6 for compression and pressurization. In addition to the cooling vessel 5, the heat exchange device can also be other types of heat exchange devices, as long as they can be used to continuously generate low-grade steam while cooling the reaction stream, such as various indirect heat exchangers, heat exchange jackets, and other hot water loops. When using an indirect heat exchanger, the high-temperature liquid phase material can be introduced into the shell side or tube side, and water can be introduced into the tube side or shell side accordingly. In the absence of a preparatory unit, the cooling vessel 5 of the waste heat recovery unit is connected to the depressurization pipeline of the synthesis vessel 1; in the case of only including the transition vessel 2, the cooling vessel 5 of the waste heat recovery unit is connected to the depressurization pipeline of the transition vessel 2 to receive the liquid phase generated during the depressurization process.

[0069] The compressor 6 of the booster unit is connected to the low-grade steam outlet of the cooling vessel 5 and is used to compress and boost the low-grade steam. The input power of the compressor 6 can be at least partially derived from the mechanical energy output of the residual pressure recovery unit, so that the pressure energy recovered during the depressurization stage can directly participate in the process of upgrading the grade of the low-grade steam, thereby forming an energy conversion path for the synergistic utilization of residual heat and residual pressure.

[0070] The boosting unit may also include a desuperheating device (not shown) configured to supply a desuperheating working fluid (e.g., spray water K), preferably softened water, to the compressor 6 to control the superheat during the steam compression process. For example, the desuperheating device may include a desuperheating working fluid storage tank and spray heads.

[0071] The steam outlet of compressor 6 can be connected to the plant's steam network to continuously supply usable steam that meets the pressure and temperature requirements of the process system.

[0072] Preferably, the system further includes an electric motor 7 connected to the compressor 6. The electric motor 7 and the expander 4 form a dual-drive structure for steam and electricity, which is used to provide power compensation or power feedback to the booster unit when there are fluctuations in pressure energy recovery.

[0073] Preferably, the expander 4 can be a turbine expander or a screw expander to meet the pressure energy recovery requirements under different gas flow and pressure conditions.

[0074] Preferably, the expander 4 can be connected to the generator 8 to drive the generator 8 to generate electricity, thereby converting mechanical energy into electrical energy. This electrical energy can be used to drive the electric motor 7 or connected to the power grid.

[0075] (II) Methods

[0076] The method for comprehensive utilization of waste heat and pressure energy in chemical processes according to this application includes: using the heat energy of the liquid phase of the material flow produced by the chemical process to heat water through heat exchange to generate water vapor; converting the pressure energy of the gas phase of the material flow produced by the chemical process into mechanical energy; and increasing the pressure of the water vapor.

[0077] like Figure 1 As shown, in one exemplary embodiment, after the reaction of reactant A in synthesis reactor 1 is completed, the high-temperature and high-pressure reaction stream (synthesis liquid B) discharged from the synthesis reactor can be introduced into transition reactor 2 for temporary storage. Through the volume buffering and discharge regulation of transition reactor 2, the intermittently discharged reaction stream is subjected to condition smoothing (i.e., conditioning), ensuring that the reaction stream is continuously and stably delivered to the subsequent energy recovery unit. Preferably, the transition reactor uses level control and discharge regulation to smooth the intermittently discharged reaction stream, maintaining relative stability in temperature, pressure, and flow rate of the stream delivered to the subsequent adiabatic flash evaporation unit.

[0078] Transition vessel 2 redistributes the reaction stream over time, spreading the concentrated release of materials and energy during the batch reaction process, thereby reducing the instantaneous fluctuations in temperature, pressure, and flow rate at the end of the reaction. This smoothing process enables subsequent energy recovery units to operate under near-steady-state conditions, providing stable material and energy boundary conditions for continuous processes such as adiabatic flash evaporation, pressure energy recovery, and vapor compression. This improves the operational stability and energy recovery efficiency of the flash evaporation, expansion, and vapor compression processes, avoiding reduced energy recovery efficiency or frequent equipment start-ups and shutdowns due to batch switching.

[0079] The reaction stream (synthesis liquid B) after the working condition is smoothed is introduced into a flash evaporator (e.g., an adiabatic flash evaporator 3) for depressurization flash evaporation, so that the reaction stream forms a liquid stream (flash liquid phase F) and a gas stream (flash vapor phase D) during the flash evaporation process. The gas phase generated during the flash evaporation enters the residual pressure recovery unit to expand and do work, so as to recover the pressure energy contained in the depressurization stage of the reaction stream.

[0080] Under adiabatic depressurization conditions, a portion of the liquid water in the reaction stream undergoes a phase change and vaporizes. The system achieves pressure equilibrium by consuming its own sensible heat, thereby generating a gaseous phase carrying pressure energy without introducing an external heat source. This process converts the energy that originally existed in the "static pressure form" in the reaction system into kinetic energy that can be used to do mechanical work, providing a thermodynamic basis for subsequent pressure energy recovery.

[0081] Preferably, the final flash pressure of the adiabatic flash reactor is 0.05–0.5 MPa (absolute pressure), and the temperature of the reaction stream after flash is 110–160°C.

[0082] Within the aforementioned pressure and temperature range, the reaction stream can undergo sufficient flash evaporation without the introduction of an external heat source, allowing some of the sensible heat in the system to be released as latent heat of phase change and form a gas phase, while retaining sufficient pressure energy for subsequent expansion and recovery, thus balancing flash evaporation efficiency and pressure energy recovery effect.

[0083] The gaseous stream obtained after adiabatic flash evaporation (flash vapor phase D) is introduced into the residual pressure recovery unit (including expander 4). In the residual pressure recovery unit, expansion and work are performed, converting the pressure energy in the gaseous stream into mechanical energy, thereby achieving pressure energy recovery. Preferably, the expander is a turbine expander or a screw expander. The expander can efficiently convert the pressure energy contained in the gas phase into mechanical energy output, significantly reducing irreversible losses compared to throttling methods, and providing a stable source of mechanical work for the subsequent pressurization unit.

[0084] The liquid stream obtained after adiabatic flash evaporation (flash liquid F) is introduced into the waste heat recovery unit (including the cooling vessel 5) for further cooling. During the cooling process, by controlling the heat exchange conditions between the liquid stream and the cooling-side working medium (water, such as softened water H) in the waste heat recovery unit, the cooling-side working medium undergoes a phase change under controlled pressure after absorbing the sensible heat of the liquid stream, continuously generating low-grade steam I, thereby achieving the steam recovery of the reaction waste heat.

[0085] After adiabatic flash evaporation, the liquid phase stream remains in a temperature range above ambient. If the sensible heat it carries is directly discharged through cooling water or other cooling media, it will be difficult to achieve effective utilization. This application addresses this by transferring the sensible heat of the liquid phase stream to the cooling-side working fluid under controlled pressure conditions. This causes the cooling-side working fluid to change from a liquid state to a gaseous state (water vapor), converting the originally dispersed and difficult-to-collect low-grade thermal energy into low-grade steam I existing in the form of latent heat of phase change. This provides an energy carrier that can be collected centrally and used for subsequent grade enhancement.

[0086] Preferably, the cooling vessel 5 operates at 70–100°C and 0.02–0.1 MPa (absolute pressure), where the working fluid on the cooling side absorbs heat and vaporizes under controlled pressure to form ultra-low-pressure steam. Under the above temperature and pressure conditions, the medium- and low-temperature sensible heat carried in the reaction stream can be converted into ultra-low-pressure steam in the form of latent heat of phase change, thereby transforming the originally dispersed and difficult-to-utilize low-grade heat energy into an energy carrier that can be collected and subsequently utilized.

[0087] The generated low-grade steam I is introduced into a booster unit (including compressor 6) for compression and pressurization. During steam compression, a desuperheating working fluid (e.g., spray water K), preferably softened water, is added to the compressed steam to control the superheat, ensuring that the compressed steam remains in a saturated or slightly superheated state. The driving force of the booster unit is at least partially derived from the mechanical energy generated in the pressure energy recovery step, allowing the pressure energy recovered during the depressurization stage to participate in the grade enhancement process of the low-grade steam in the form of mechanical work, thereby upgrading the low-grade steam into usable steam that can be directly integrated into the process steam network.

[0088] The essence of steam compression lies in increasing the enthalpy and pressure of steam through external mechanical work input. Proper control of steam superheat helps improve steam quality and reduce additional system heat load. This application introduces desuperheating control during steam compression, converting the sensible superheat generated during compression into the latent heat of vaporization of the desuperheating working fluid. This achieves synergistic optimization of steam grade improvement and increased steam mass flow rate without introducing an additional high-grade heat source. By converting the pressure energy recovered during the depressurization stage into mechanical work and using it to drive the booster unit, a synergistic utilization mechanism of "residual pressure supporting waste heat upgrade" is constructed at the system level. This reduces the dependence of the steam grade improvement process on external energy sources and improves the overall energy efficiency of the system.

[0089] Preferably, in the driving force of the booster unit, the mechanical energy recovered by the expander accounts for 5% to 60% of the total power demand of the booster unit. Within this range, it can be ensured that the pressure energy recovery results provide substantial support for the steam compression process, and the stable operation of the booster unit can be avoided due to fluctuations in the expander output, thus balancing energy utilization and system reliability.

[0090] Preferably, the absolute pressure of the usable steam output by the booster unit is 0.25–0.9 MPa. This pressure range covers the low- and medium-pressure steam grades commonly used in fine chemical plants, enabling the recovered steam to be directly integrated into the existing process steam network, avoiding the need for secondary heat exchange or pressure reduction due to steam grade mismatch.

[0091] Preferably, the temperature of the compressed steam is regulated by supplementing with spray water (preferably softened water) or spray condensate, or by using heat exchange, to maintain it as saturated steam or slightly superheated steam with a superheat of no more than 10°C. By regulating the steam state, it is possible to avoid the reduction in efficiency or increase in safety risks of downstream steam-using equipment due to steam overheating, while improving the applicability of steam in pipeline transportation and terminal utilization.

[0092] Preferably, when the mechanical energy recovered by the expander is insufficient to meet the driving requirements of the booster unit, the electric motor supplements the power; when the mechanical energy recovered by the expander is surplus, power is fed back through a power generation device, thus forming a dual-drive steam-electric operation mode. This dual-drive structure can adapt to load fluctuations caused by batch switching in chemical processes such as benzotriazole synthesis, enabling the booster unit to operate stably under different operating conditions and improving the system's adaptability and reliability.

[0093] Preferably, provided that the steam demand of the unit itself is met, the generated usable steam can be used in addition to being incorporated into the internal steam network of the unit, and can also be sent to the steam network of the plant area as needed, so that the synthesis unit has the ability to operate with steam self-balancing or steam external transmission.

[0094] The reaction stream after flash evaporation and cooling (cooled material G), and the tail gas E after expansion and work done by the residual pressure recovery unit, enter the original material post-processing system (such as the material purification system) and tail gas treatment system respectively, without affecting the original synthesis process.

[0095] By placing the energy recovery process after the reaction process and decoupling it from the original material handling path, comprehensive energy utilization can be achieved without changing the chemical reaction conditions and product quality control logic, thereby improving the system's engineering adaptability and feasibility for modification.

[0096] In one specific embodiment, the synthesis reaction of benzotriazole is carried out in a batch manner in synthesis reactor 1; after the reaction is completed, a transition reactor is set up to achieve a smooth switch from batch operation to continuous energy recovery unit, so that the residual pressure recovery, residual heat recovery and steam grade improvement processes can be operated stably in a continuous manner.

[0097] Step 1: Transition and continuous discharge process after batch reaction ends (batch reaction → continuous energy recovery operating condition shaping)

[0098] like Figure 1 As shown, after the reaction feed A enters the synthesis reactor 1, the synthesis reactor 1 is heated and pressurized to carry out the synthesis reaction. After a predetermined reaction time, the synthesis reaction ends, and at this time, a high-temperature and high-pressure synthesis liquid B is obtained in the synthesis reactor 1, with a temperature of about 200-300 ℃ and a pressure under high pressure.

[0099] After the synthesis reaction is completed, the discharge pipeline connecting synthesis vessel 1 and transition vessel 2 is opened to discharge the high-temperature and high-pressure synthesis liquid B into the transition vessel. The transition vessel is used to buffer and stabilize the intermittent discharge process, and maintains the synthesis liquid within the set temperature range through a jacket or coil. At the same time, through liquid level control and discharge regulation, the transition vessel continuously and stably outputs the synthesis liquid downstream, thereby providing stable operating boundary conditions for the subsequent adiabatic flash evaporation and energy recovery processes.

[0100] Step 2: Continuous adiabatic flash evaporation and residual pressure recovery process (pressure energy → mechanical work / electrical energy)

[0101] The high-temperature and high-pressure synthesis liquid B, continuously output from the transition vessel, enters the adiabatic flash evaporator 3. The synthesis liquid undergoes controlled pressure reduction flash evaporation under adiabatic conditions, producing a flash vapor phase D and a flash liquid phase F. The flash vapor phase is mainly water vapor, carrying significant pressure energy.

[0102] The flash vapor phase is introduced into a residual pressure recovery unit for expansion and work to recover pressure energy. The residual pressure recovery unit includes an expander 4, such as a turbo expander or a screw expander. After expansion in the expander 4, the pressure of the flash vapor phase D is significantly reduced, forming a depressurized gas phase (exhaust gas), which is then processed in the existing exhaust gas condensation and absorption system.

[0103] During the expansion process, the output shaft of expander 4 outputs mechanical work. This mechanical work is used for subsequent steam grade enhancement processes, depending on the system configuration and operating conditions. (1) In one embodiment, the output shaft of the expander 4 is connected to the input shaft of the compressor 6 of the booster unit through a mechanical transmission structure to directly drive the vapor compression process; (2) In another embodiment, the output shaft of the expander 4 is used to drive the generator 8 to generate electricity. The generated electricity is connected to the grid through the grid connection system, and the grid provides driving power to the boost unit.

[0104] The above methods enable the recovery and utilization of residual pressure from the reaction, and provide a power source for upgrading the grade of low-grade steam.

[0105] Step 3: Further waste heat recovery and low-grade steam generation process of flash liquid phase (sensible heat → steam carrier)

[0106] The liquid phase stream after adiabatic flash evaporation is still in a temperature range higher than the ambient temperature. If cooling water is used directly for cooling, the low-grade heat energy will be difficult to reuse. The flashed liquid phase is introduced into a cooling unit for further cooling. During the cooling process, by controlling the heat exchange conditions of the cooling unit, the working fluid on the cooling side absorbs the sensible heat of the flashed liquid phase and undergoes a phase change, continuously generating low-grade steam.

[0107] In a preferred embodiment, softened water H enters the cooling vessel 5 of the waste heat recovery unit and exchanges heat with the flash liquid phase; the heated water is flashed under controlled low pressure to generate low-grade steam I; the system water balance is maintained by continuously replenishing the softened water H.

[0108] Step 4: Grade enhancement of low-grade steam and steam grid connection (steam upgrading)

[0109] The low-grade steam I generated in step three is introduced into the heat pump compressor 6 in the booster unit for compression and pressurization, upgrading the low-grade steam into usable process steam J. The compressed steam is then fed into the low-pressure steam network for use by other process units. Simultaneously, to ensure that the usable process steam J meets the requirements for process steam and pipeline transportation, temperature control is achieved by supplementing the steam compression process with spray water K. The spray water is preferably softened water or recycled condensate to absorb the excess sensible heat generated during compression, maintaining the compressed steam as saturated steam or slightly superheated steam with a superheat not exceeding a predetermined range.

[0110] Through the above methods, the waste heat from the reaction is converted from low-grade heat energy into usable steam and its energy level is improved, thus avoiding the direct emission of low-grade heat energy.

[0111] Stable operation mechanism under combined electric and gas drive (preferred implementation method)

[0112] In a preferred embodiment, the system is equipped with an electric motor 7, which is connected to the booster unit and together with the expander 4, forms a steam-electric co-drive structure.

[0113] When the mechanical work output by expander 4 is insufficient to meet the operating requirements of the booster unit, the required power is supplemented by the power grid supplied by motor 7 using electricity from the electric grid. When the output power of expander 4 exceeds the requirements of the booster unit, the excess energy can be fed back to the grid through power generation and grid connection, provided that the compressor drive requirements are met. Through the above methods, the system can adapt to the load fluctuations caused by the intermittent operation of the synthesis reaction and maintain the continuous and stable operation of the steam grade improvement process.

[0114] System reconnection and process compatibility description

[0115] The flash liquid phase after waste heat recovery and the tail gas after pressure energy recovery are respectively entered into the original downstream material processing system and tail gas treatment system; the entire energy comprehensive utilization process does not change the reaction mechanism, product quality control method and safety control logic of the original benzotriazole synthesis process.

[0116] Not limited to any particular theory, the applicant proposes the following mechanism: First, the mechanism of waste heat recovery and energy level construction.

[0117] This application utilizes a controlled heat exchange and flash evaporation process to convert the sensible heat of the high-temperature materials at the end of the benzotriazole synthesis reaction into the latent heat of phase change of low-pressure steam, thus transforming the residual heat from a dispersed sensible heat form into a centrally usable steam carrier. This carrier process reduces irreversible losses during heat recovery and provides a unified and stable energy foundation for subsequent steam grade enhancement, fundamentally overcoming the limitation of traditional cooling methods in outputting usable energy.

[0118] Second, the driving mechanism of mechanical work recovery and thermal energy grade improvement of residual pressure.

[0119] To address the pressure potential energy contained in the high-pressure tail gas during the reaction depressurization stage, this application utilizes an expander to convert it into mechanical work, thus avoiding pressure energy dissipation caused by throttling and depressurization. The obtained mechanical work is used to drive the steam compression process, enabling the low-pressure steam to achieve enthalpy and pressure level increases without relying on external high-grade energy sources. This facilitates the energy level transition from low-grade thermal energy to usable process steam, directly driving the waste heat upgrading process through residual pressure.

[0120] Third, the mechanism of system-level coordination and reduction of irreversible losses.

[0121] By synergistically coupling waste heat recovery as a carrier with waste pressure recovery at the system level, this application constructs a closed-loop energy utilization path of "waste heat to steam—waste pressure to drive compression—steam grade improvement". This synergistic mechanism reduces intermediate energy conversion links and additional heat loads, and achieves condition matching between intermittent reaction and continuous energy recovery through units such as transition vessels, thereby reducing irreversible losses at the system level. Ultimately, this is reflected in the simultaneous reduction of external steam consumption, external power supply, and cooling load, and a significant improvement in overall economic efficiency.

[0122] Example

[0123] To make the technical solution of this application clearer, the technical solution of this application will be further described below with reference to some specific embodiments. The described embodiments are for further illustrative purposes and should not be construed as limiting the scope of protection of this application.

[0124] Example 1 (Synchronous Example of Residual Pressure Expansion Power Generation + Electric Driven Steam Compression)

[0125] In this embodiment, the benzotriazole synthesis reaction is carried out intermittently in a synthesis reactor. After the reaction is completed, the high-temperature and high-pressure synthesis liquid in the synthesis reactor recovers the waste heat through a hot water flash evaporation system. The system continuously generates low-grade steam that enters the pressurization unit, with a mass flow rate of approximately 1.4–1.6 t / h.

[0126] The low-grade steam enters the pressurization unit for compression and pressurization. To control the superheat of the compressed steam below 10°C, approximately 0.7 t / h of softened water is sprayed into the steam at the compressor outlet for de-cooling. The softened water vaporizes under the sensible heat of the steam and mixes with it, resulting in usable slightly superheated steam at the compressor outlet with a mass flow rate of approximately 2.1–2.3 t / h.

[0127] The slightly superheated steam is integrated into the process steam network. Under typical operating conditions, the process steam load of the unit at this capacity scale is consistent with the comparative example below, and the baseline steam supply demand of the external low-pressure steam network is approximately 1.4–1.6 t / h. In this embodiment, through hot water flash evaporation and steam compression pressurization combined with spray cooling, approximately 2.1–2.3 t / h of usable slightly superheated steam can be integrated into the steam network, which can equivalently replace the above-mentioned baseline steam supply demand. After offsetting the unit's own steam load, approximately 0.5–0.9 t / h of surplus steam can still be generated and sent to the plant's low-pressure steam network, with a net external steam consumption of approximately 0 t / h.

[0128] During the reaction depressurization stage, the high-pressure exhaust gas in the flash reactor enters the expander to expand and perform work. The mechanical work output by the expander drives the generator to generate electricity, which is then fed into the plant's power grid to provide partial power support for the booster unit and related electrical equipment. Considering the energy conversion losses during the expansion power generation and motor drive process, and because the booster unit has a large power demand under full-load conditions, the expansion power generation can only cover part of its power demand. Therefore, the system still requires a certain amount of external power supply to maintain stable operation. The system's external power supply is approximately 400–480 kW.

[0129] The expanded exhaust gas enters the existing exhaust gas condensation and absorption treatment system. Before entering the exhaust gas absorption unit, it needs to be condensed by cooling water. Therefore, the system has a certain cooling demand, and its cooling load is approximately (3.0~4.5)×10 5 kcal / h.

[0130] Under typical operating conditions, the use of slightly superheated steam in this embodiment demonstrates a significant energy substitution effect, essentially completely covering the original external steam consumption; the annual utility costs of the system are approximately 2.3 to 2.7 million yuan. Compared to the traditional solution using cold heat transfer oil for cooling and pressure relief, this embodiment can achieve annual utility cost savings of approximately 1.8 to 2.3 million yuan. With an additional equipment investment of approximately 9 to 12 million yuan, the static investment payback period of the system is approximately 4.5 to 6 years.

[0131] The energy consumption level, annual operating cost, and economic evaluation in this embodiment are all based on a 10,000-ton-per-year benzotriazole plant, calculated based on approximately 8,000 hours of annual operation, and converted in conjunction with the enterprise's utility settlement unit price.

[0132] Example 2 (Highly Synergistic Example of Residual Pressure Expansion Direct-Drive Steam Compression)

[0133] In this embodiment, the benzotriazole synthesis reaction and the waste heat recovery method are the same as in Example 1. After the reaction is completed, the waste heat is recovered through a hot water flash evaporation system. The system continuously generates low-grade steam that enters the pressurization unit, with a mass flow rate of approximately 1.4–1.8 t / h.

[0134] The low-grade steam enters the pressurization unit for compression and pressurization. To control the superheat of the compressed steam to within 10°C, softened water is sprayed into the compressed steam for de-heating, so that usable slightly superheated steam is formed at the compressor outlet, with a mass flow rate of approximately 2.1–2.4 t / h.

[0135] The slightly superheated steam is integrated into the process steam network. Under typical operating conditions, the process steam load of the unit at this capacity scale is consistent with the following comparative example, where the baseline steam supply demand of the external low-pressure steam network is approximately 1.4–1.6 t / h. In this embodiment, through steam compression pressurization and combined with spray desuperheating, approximately 2.1–2.4 t / h of usable slightly superheated steam can be integrated into the steam network, effectively replacing the aforementioned baseline steam supply demand. After offsetting the unit's own steam load, approximately 0.5–1.0 t / h of surplus steam can still be generated and sent to the plant's low-pressure steam network, resulting in a net external steam consumption of approximately 0 t / h.

[0136] Unlike Example 1, in this example, the pressure energy recovered during the depressurization stage is not converted into electricity. Instead, it is directly driven by the expander output shaft through a mechanical transmission structure to drive the steam compressor. This allows the pressure energy to directly participate in the grade enhancement process of low-grade steam in the form of mechanical work, thereby reducing energy conversion steps and improving pressure energy utilization efficiency. Since there is no power generation and motor re-drive process, the external power supply of the system is further reduced to approximately 350–420 kW.

[0137] In this embodiment, the treatment path of the expanded exhaust gas is the same as in Embodiment 1, still entering the original exhaust gas condensation and absorption system, where condensation treatment is required before entering the absorption unit. Due to the reduction in overall system energy conversion stages and the decrease in additional heat load, the heat required to be removed in the exhaust gas condensation section is correspondingly reduced, and its cooling load is approximately (2.0~3.0)×10⁻⁶. 5 kcal / h, lower than in Example 1.

[0138] Under typical operating conditions, the annual utility costs of this embodiment are approximately RMB 1.9 million to 2.3 million. Compared with the traditional solution, the annual utility costs can be reduced by RMB 2.2 million to 2.8 million. With an additional equipment investment of approximately RMB 8 million to 10 million, the static investment payback period of the system is approximately 3.0 to 4.5 years, making it more economical than Embodiment 1.

[0139] The energy consumption level, annual operating cost, and economic evaluation in this embodiment are all based on a 10,000-ton-per-year benzotriazole plant, calculated based on approximately 8,000 hours of annual operation, and converted in conjunction with the enterprise's utility settlement unit price.

[0140] Comparative example (traditional energy treatment solution of cooling with heat transfer oil + throttling and pressure relief)

[0141] In this comparative example, after the benzotriazole synthesis reaction is completed, the high-temperature synthesis liquid in the synthesis vessel is cooled by a cold heat transfer oil system. The residual heat of the reaction is dissipated in the form of low-grade heat through the heat transfer oil cooler, and no usable steam energy carrier is formed. The system does not produce by-product steam.

[0142] During the depressurization stage of the reaction, the high-pressure tail gas in the synthesis reactor is throttled and depressurized through a pressure reducing valve before entering the tail gas treatment system. The pressure energy generated during the depressurization process is not recovered. The process steam required for the production process is entirely dependent on the external steam pipeline network, and the baseline steam supply demand of the external low-pressure steam pipeline network is approximately 1.4–1.6 t / h.

[0143] In this comparative example, the external power supply is mainly used for auxiliary utilities such as the heat transfer oil circulation pump and cooler fan, and does not involve power-consuming units such as steam compression. The external power supply is approximately 80–150 kW. Since the waste heat from the reaction is mainly removed by the cold heat transfer oil system, the system has a high cooling load, which is approximately (8.0–12.0) × 10⁻⁶. 5 kcal / h.

[0144] Under typical operating conditions, the annual utility costs for the comparative example are approximately RMB 4.2 million to 5.1 million, which is significantly higher than those in the embodiments of this application.

[0145] The energy consumption level, annual operating cost, and economic evaluation of this comparative example are based on a 10,000-ton-per-year benzotriazole plant, with an annual operating time of approximately 8,000 hours, and are converted in conjunction with the unit price of the enterprise's public works settlement.

[0146] Table 1 lists the comparison of various parameters for Example 1, Example 2, and the comparative example.

[0147] Table 1

[0148] Note: Annual cost savings are calculated based on a comparative ratio.

[0149] By comparing the systems of Example 1, Example 2 and the comparative example, it can be seen that this application introduces a synergistic recovery mechanism of reaction waste heat and waste pressure in the benzotriazole synthesis system. Without changing the process conditions of the synthesis reaction itself and the product quality control method, it achieves a fundamental optimization of the energy consumption structure of the device and significantly improves the overall energy efficiency and economy of the system.

[0150] In the comparative example, after the synthesis reaction, the synthesis liquid is mainly cooled through a cold heat transfer oil system, and the waste heat from the reaction is dissipated as low-grade heat, without forming a usable steam energy carrier. Simultaneously, the depressurization stage of the reaction is completed using a throttling method, and the pressure energy contained in the high-pressure tail gas is not recovered. In this scheme, the process steam for the unit relies entirely on an external low-pressure steam network, with a baseline external steam demand of approximately 1.4–1.6 t / h. Furthermore, the system's cooling load is high, resulting in a high overall utility cost.

[0151] Example 1 utilizes a hot water flash evaporation system and a pressurization unit to convert waste heat from the reaction into low-grade steam. After compression and desuperheating, this steam becomes usable steam that can be integrated into the steam network. The resulting usable steam not only effectively replaces the unit's baseline external steam demand but also generates a certain amount of surplus steam for external transmission after meeting the unit's steam load. This transforms the unit from a traditional steam-consuming unit into a steam-self-balancing or even steam-output unit. Simultaneously, an expander is introduced during the reaction depressurization stage to recover pressure energy and provides partial electrical support to the pressurization unit through power generation, significantly reducing the system's overall energy consumption. However, because pressure energy requires an intermediate "mechanical-electrical-mechanical" conversion process, some energy conversion losses still exist, and the corresponding external power supply demand and tail gas condensation cooling load remain.

[0152] Example 2, building upon Example 1, further optimizes the utilization path of pressure energy. The pressure energy recovered during the reaction depressurization stage is directly used by the expander output shaft to drive the steam compressor in the form of mechanical work. This allows the pressure energy to directly participate in the grade enhancement process of low-grade steam without intermediate electrical energy conversion. Compared to Example 1, this scheme significantly reduces energy conversion steps and shortens the energy transfer path. While maintaining the scale of by-product steam and process applicability, it further reduces the system's external power supply requirements. Simultaneously, due to the reduction in additional heat load, the cooling load during the tail gas condensation stage is also reduced, achieving a higher degree of energy synergy at the system level.

[0153] In summary, compared with the traditional solution of using cold heat transfer oil for cooling and throttling pressure relief, both Embodiment 1 and Embodiment 2 of this application can achieve effective recovery and cascade utilization of waste heat and waste pressure from the reaction. Among them, Embodiment 2, which directly drives the booster unit through waste pressure, further optimizes the energy utilization path, system synergy, and engineering economy, and is a more preferred implementation method of this application, with more significant energy-saving effect and better economic return.

[0154] Through a systematic study of the embodiments and comparative examples, this application arrives at the following inductive conclusions and engineering points: (1) The system synergy of waste heat and waste pressure is the key to improving overall energy efficiency.

[0155] The comparative results show that simply relying on cooling to remove waste heat and throttling to release waste pressure leads to the irreversible dissipation of a large amount of usable energy. This application addresses this by converting waste heat into a steam carrier and waste pressure into mechanical work, and by achieving synergistic coupling between the two at the system level. This makes waste pressure the energy source driving the improvement of waste heat quality, which is the core mechanism for achieving a leap in energy efficiency.

[0156] (2) Steam carrier is the basic engineering path for efficient utilization of reaction waste heat.

[0157] Example studies show that by converting the sensible heat of reactants into the latent heat of phase change of low-pressure steam through controlled heat exchange and flash evaporation, irreversible losses in the heat recovery process can be significantly reduced, and a unified and stable energy carrier can be provided for subsequent energy level enhancement. Compared with direct cooling, this path is more suitable for converting waste heat from the reaction into high-value energy that can be incorporated into public utility systems.

[0158] (3) Pressure can directly participate in the improvement of steam grade, resulting in better system efficiency.

[0159] Regarding the residual pressure recovery method, the comparative examples show that directly using the mechanical work output by the expander to drive the steam compression process can effectively reduce intermediate energy conversion links, reduce external power supply requirements and additional heat load; compared with the method of re-driving through power generation, the direct drive path has more obvious advantages in terms of system efficiency and economy.

[0160] (4) Shortening the energy conversion path helps to reduce the electricity and cooling loads simultaneously.

[0161] The system study results show that reducing the number of energy conversion stages not only reduces electrical energy loss but also lowers the additional heat dissipation requirements caused by energy conversion, thereby reducing the cooling load required for exhaust gas condensation and system heat dissipation. This "electricity-cooling linkage" effect is an important manifestation of system-level energy efficiency improvement.

[0162] (5) A working condition matching design is required between batch reaction and continuous energy recovery.

[0163] Since the synthesis reaction of benzotriazole is intermittent, while flash evaporation, expansion and vapor compression processes are more suitable for continuous operation, this application sets up buffer units such as transition vessels to achieve time-scale condition shaping, ensuring the stable and efficient operation of the energy recovery system, which is a key point for the feasibility of the project.

[0164] (6) System integration is superior to unit optimization and is the fundamental way to achieve economy.

[0165] The comprehensive economic comparison between the examples and the comparative examples shows that improving the efficiency of a single device is not enough to significantly reduce the overall energy cost. However, by integrating the system to achieve the synergistic utilization of waste heat and waste pressure, reductions can be achieved simultaneously in the three dimensions of steam, electricity, and cooling, ultimately resulting in significant savings in utility costs and good investment recovery characteristics.

[0166] The system comparison results of the examples and comparative examples show that, without changing the process conditions of the synthesis reaction itself and the product quality control method, this application can significantly reduce the overall dependence of the device on external steam, electricity and cooling resources through the synergistic recovery and cascade utilization of reaction waste heat and waste pressure. This transforms the device from a traditional utility consumption unit into an energy-friendly unit with steam self-balancing or even steam external transmission capabilities, thereby effectively reducing utility costs and achieving significant energy-saving effects and good economic returns.

[0167] The above embodiments are merely preferred embodiments of this application. It should be noted that the above preferred embodiments should not be considered as limitations on this application, and the scope of protection of this application should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for comprehensive utilization of waste heat and waste pressure energy in chemical processes, characterized in that, The method includes: (a1) The heat energy of the liquid phase of the material flow produced by the chemical process is used to heat water through heat exchange to generate water vapor; (a2) Converting the pressure energy of the gas phase of the material flow originating from a chemical process into mechanical energy; (b) Pressurize the water vapor. The energy that pressurizes the water vapor comes at least partially from mechanical energy and / or at least partially from electrical energy.

2. The method according to claim 1, characterized in that, The chemical process described is the synthesis reaction of benzotriazole.

3. The method according to claim 1, characterized in that, The pressure energy of the gas phase is converted into mechanical energy by an expander; and / or The steam pressure is increased by a compressor; and / or The mechanical energy is at least partially converted into electrical energy.

4. The method according to claim 1, characterized in that, The method further includes: (a01) Prior to steps (a1) and (a2), the material flow produced by the chemical process is conditioned to balance material and energy fluctuations; or (a02) Before steps (a1) and (a2), the material stream produced by the chemical process is flash-evaporated; or (a03) Before steps (a1) and (a2), the material stream produced by the chemical process is conditioned to balance material and energy fluctuations, and then the material stream produced by the chemical process is flashed.

5. The method according to any one of claims 1-4, characterized in that, The method further includes: (c1) The gas phase is absorbed or further processed after the pressure energy is converted into mechanical energy; and / or (c2) Use pressurized steam for internal needs of the chemical process or for external steam network.

6. A comprehensive energy utilization system for waste heat and pressure in chemical processes, characterized in that, The system includes: The waste heat recovery unit is configured to receive the liquid phase of the material stream produced from the chemical process and use the heat energy of the liquid phase to heat water through heat exchange to generate water vapor. The residual pressure recovery unit is configured to receive the gas phase of a material stream originating from a chemical process and convert the pressure energy of the gas phase into mechanical energy. A pressurization unit is configured to receive the water vapor and pressurize it. The pressurization unit is connected to the residual pressure recovery unit and is used to drive the water vapor to pressurize using the mechanical energy.

7. The system according to claim 6, characterized in that, The system includes a preparatory unit, wherein: The preparation unit includes a transition vessel configured to receive the material stream produced by the chemical process and configured to be in fluid communication with the waste heat recovery unit and the waste pressure recovery unit, respectively, to provide liquid and gas phases to the waste heat recovery unit and the waste pressure recovery unit, respectively; or The preparatory unit includes a flash evaporator configured to receive a material stream produced by a chemical process, flash-treat the material stream in the flash evaporator, and is configured to be fluidly connected to a waste heat recovery unit and a waste pressure recovery unit, respectively, to provide liquid and gas phases to the waste heat recovery unit and the waste pressure recovery unit, respectively; or The preparation unit includes a transition vessel and a flash evaporator. The transition vessel is configured to receive the material stream produced by the chemical process. The flash evaporator is configured to be in fluid communication with the transition vessel so that the material stream produced by the chemical process is flash-treated in the flash evaporator. It is also configured to be in fluid communication with the waste heat recovery unit and the waste pressure recovery unit respectively, so as to provide the waste heat recovery unit and the waste pressure recovery unit with liquid phase and gas phase respectively.

8. The system according to claim 6 or 7, characterized in that, The waste heat recovery unit includes a heat exchange device; and / or The residual pressure recovery unit includes an expander; and / or The booster unit includes a compressor; and / or The system also includes a power generation device, and a residual pressure recovery unit is connected to the power generation device to convert the mechanical energy into electrical energy; and / or The system also includes an electric motor connected to a booster unit for using electrical energy to boost the pressure of the water vapor.

9. The system according to claim 6 or 7, characterized in that, The residual pressure recovery unit includes an expander, and the pressure boosting unit includes a compressor. The output shaft of the expander is connected to the input shaft of the compressor.

10. The system according to claim 6 or 7, characterized in that, The system includes a power generation device, and the booster unit includes a compressor. The power generation device is connected to the drive mechanism of the compressor.

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