Applicable to the food processing industry low-temperature saturated steam waste heat utilization power generation system

Abstract

The present invention relates to a power generation system for utilizing waste heat from low-temperature saturated steam suitable for the food processing industry, comprising a heat source input system and a power generation circulation system, wherein the heat source input system comprises a heat source and an evaporator, wherein the heat source is connected to the evaporator via a heat source input pipeline; the power generation circulation system comprises an evaporator, a generator, an air-cooled condenser, a working fluid pump, a liquid storage tank, a regenerator, a preheater, and a grid-connected inverter, which are used to exchange heat between the working fluid and the heat source, and the generator is used to generate electricity. The present invention recovers the waste heat of directly discharged saturated steam in the food processing industry, converts the thermal energy into mechanical energy and then into electrical energy, thereby realizing heat energy recovery and reducing the greenhouse effect risk brought about by direct discharge.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery and energy conservation technology in the food processing industry. Specifically, it relates to a system based on the Organic Rankine Cycle (ORC) principle and magnetically suspended high-speed permanent magnet radial turbine expansion power generation technology, which utilizes low-temperature saturated steam discharged from the tail of the production process system to generate waste heat power. Background Art

[0002] my country has long suffered from significant waste and loss in the use of energy. Statistics show that the energy utilization rate is less than 40%, which is 10-20 percentage points lower than that of developed countries.

[0003] Waste heat can be categorized into three types based on its temperature: low-temperature waste heat, medium-temperature waste heat, and high-temperature waste heat. Generally, waste heat below 220°C is defined as low-temperature waste heat; waste heat between 220°C and 650°C is defined as medium-temperature waste heat; and waste heat above 650°C is defined as high-temperature waste heat. Low-temperature waste heat accounts for over 50% of industrial waste heat, but its utilization rate is very low.

[0004] ORC is a proven power generation system that converts low-grade thermal energy into electricity. This system uses an evaporator to exchange low-grade thermal energy with an organic working fluid. After absorbing heat, the organic working fluid transforms from a liquid into a gas. The high-pressure organic working fluid vapor drives a turbine expander, converting thermal energy into mechanical energy, which in turn drives a generator to generate electricity. After releasing energy in the expander, the vapor enters the condenser at the expander outlet, where it cools to a liquid state. After being pressurized by a working fluid pump, it re-enters the evaporator, beginning a new cycle.

[0005] The efficient utilization of low-grade thermal energy, including industrial low-temperature waste heat and new energy sources such as geothermal energy, solar energy, and biomass energy, is a key approach to resolving energy challenges. The utilization of low-grade thermal energy not only improves energy efficiency and promotes energy conservation and emission reduction, but also optimizes the energy supply structure, thus possessing significant practical significance.

[0006] In the food processing industry, traditional production systems require 185°C saturated steam to steam flatbreads, primarily to promote starch alpha-strengthening. After passing through the steamer, the saturated steam is directly released into the atmosphere. To avoid energy waste and environmental impact, a low-temperature saturated steam solution was needed. Summary of the Invention

[0007] The purpose of the present invention is to provide a low-temperature saturated steam waste heat utilization power generation system suitable for the food processing industry, so as to avoid the direct discharge of low-temperature saturated steam in the food processing industry into the atmosphere, and to avoid energy waste and environmental impact.

[0008] The technical solution of the present invention:

[0009] A power generation system using waste heat from low-temperature saturated steam in the food processing industry, comprising a heat source input system and a power generation circulation system.

[0010] The heat source input system includes a heat source and an evaporator, wherein the heat source is connected to the hot side inlet of the evaporator through a heat source input pipeline, the hot side outlet of the evaporator is connected to the inlet of the vacuum filter, the outlet of the vacuum filter is connected to the hot side inlet of the preheater, and the hot side outlet of the preheater discharges softened water;

[0011] The power generation cycle system includes an evaporator, a generator, an air-cooled condenser, a working fluid pump, a liquid storage tank, a regenerator, a preheater, and a grid-connected inverter. The water outlet of the liquid storage tank is connected to the working fluid pump through a pipeline, and the other end of the working fluid pump is connected to the water return port of the liquid storage tank through a pipeline. The pipeline between the working fluid pump and the water return port of the liquid storage tank is connected to the cold side inlet of the regenerator through a pipeline, the cold side outlet of the regenerator is connected to the cold side inlet of the preheater, the cold side outlet of the preheater is connected to the cold side inlet of the evaporator, the cold side outlet of the evaporator is connected to the generator inlet, the generator outlet is connected to the hot side inlet of the regenerator, the hot side outlet of the regenerator is connected to the hot side inlet of the air-cooled condenser, the hot side outlet of the air-cooled condenser is connected to the working fluid pump, the electricity generated by the generator is connected to the power grid through the grid-connected inverter, and the pipeline between the cold side outlet of the evaporator and the generator is connected to the hot side inlet of the air-cooled condenser through a branch.

[0012] Beneficial effects of the present invention:

[0013] 1. The present invention is a method for recovering waste heat from direct discharge of saturated steam in the food processing industry. It converts thermal energy into mechanical energy and then into electrical energy, thereby realizing heat energy recovery and reducing the greenhouse effect risk brought about by direct discharge.

[0014] 2. The present invention can realize the efficient utilization of waste heat from saturated steam in the existing food processing industry without reducing the quality of waste heat energy, which can not only save energy and reduce emissions, but also reduce costs for enterprises.

[0015] 3. The power generation cycle system of the present invention uses a magnetic levitation expansion generator. The existing traditional expanders are mostly screw expander generators. The main disadvantages of screw expander generators are:

[0016] ①. The operating noise is relatively loud, and generally, noise reduction equipment needs to be installed.

[0017] ②. The power consumption is relatively high.

[0018] ③. The screw clearance will become larger after long-term operation, and the cost of regular repair or replacement is high.

[0019] The magnetic levitation high-speed permanent magnet radial turbine expansion power generation is:

[0020] ①. High thermal efficiency;

[0021] ② The equipment is compact and the entire system is easy to integrate and skid-mount;

[0022] ③. Low operating noise;

[0023] ④. The bearings are non-contact, low energy consumption, no lubrication system, no seals, components are maintenance-free for life, low cost, and can detect rotor imbalance in real time.

[0024] ⑤. Long service life: the service life of the generator set can reach 10-15 years.

[0025] 4. Conventional condensers usually use water-cooled condensers, but in many cases, there may not be a cold water source for cooling on site, and the cold water source also has the risk of sewage discharge, which increases operating and maintenance costs and requires investment in equipment. Therefore, the condenser in the system of the present invention uses an air-cooled condenser, which directly uses air to cool the working medium.

[0026] 5. This ORC magnetic levitation power generation system, designed for utilizing waste heat from low-temperature saturated steam, was originally intended for use in northern China. While it fully meets design requirements in winter, spring, and autumn, summer temperatures exceeding 30°C prevent air cooling from completely condensing the working fluid, reducing the system's power generation efficiency. Since the system's maximum rated input is 5 t / h of saturated steam, while the unit's actual rated capacity is 3.5 t / h, the reduced summer power generation efficiency can be addressed by increasing the heat source flow rate to adjust the generated power. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1 This is the system flow chart of this application.

[0029] Figure 2 This is the process flow chart of this application.

[0030] Reference numerals:

[0031] Heat source 1; evaporator 2; vacuum filter 3; air-cooled condenser 4; working fluid pump 5; liquid storage tank 6; regenerator 7; preheater 8; grid-connected inverter 9; second valve 10; heat source input pipeline 11; first valve 12; third valve 13; fourth valve 14; fifth valve 15; sixth valve 16; seventh valve 17; eighth valve 18; generator 19. DETAILED DESCRIPTION

[0032] The present invention provides an ORC magnetic levitation power generation system suitable for utilizing waste heat from low-temperature saturated steam in the food processing industry. This system belongs to the field of waste heat recovery and energy conservation technology in the food processing industry. Specifically, it relates to a system based on the Organic Rankine Cycle (ORC) principle and magnetic levitation high-speed permanent magnet radial turbine expansion power generation technology, utilizing low-temperature saturated steam discharged from the production process system to generate waste heat power. The system consists of two parts: saturated steam discharged from the user's process system is input into the system as a heat source, and a power generation cycle system. The food processing industry has a large amount of underutilized saturated steam in its production process systems. Conventional treatment involves direct discharge into the atmosphere, which wastes energy and contributes to the greenhouse effect. By introducing this saturated steam into the power generation cycle system, the generated electricity can be used for self-generation within the factory, achieving energy conservation and emission reduction while also generating significant annual economic benefits. Furthermore, the condensed high-temperature water can be used to heat the factory building. This present invention fully utilizes the waste heat resources of the food processing industry's process systems.

[0033] The following is a detailed description of this application:

[0034] A power generation system utilizing waste heat from low-temperature saturated steam, suitable for the food processing industry, comprises a heat source input system (using saturated steam discharged from the user's process system as the heat source input system) and a power generation cycle system. The heat source input system comprises a heat source 1 and an evaporator 2. The heat source 1 is connected to the hot-side inlet of the evaporator 2 via a heat source input pipeline 11. The hot-side outlet of the evaporator 2 is connected to a vacuum filter 3. The outlet of the vacuum filter 3 is connected to the hot-side inlet of a preheater, which discharges softened water.

[0035] The power generation cycle system includes an evaporator 2, a generator 19, an air-cooled condenser 4 (the air-cooled condenser uses air as a cooling source), a working fluid pump 5, a liquid storage tank 6, a regenerator 7, a preheater 8, and a grid-connected inverter 9. The liquid storage tank 6 has three inlets: a water inlet, a water outlet, and a water return port. The water inlet of the liquid storage tank is used to add working fluid, and a fifth valve is installed on the water inlet pipeline. The water outlet pumps the working fluid into the system via the working fluid pump. The water return port is used to pump the working fluid back to the liquid storage tank when the system is not operating. The water outlet of the liquid storage tank is connected to the working fluid pump 5 through a pipeline (a fourth valve is installed on the pipeline), and the other end of the working fluid pump 5 is connected to the water return port of the liquid storage tank through a pipeline (a third valve is installed on the pipeline), and the pipeline between the working fluid pump 5 and the water return port of the liquid storage tank 6 is connected to the cold side inlet of the regenerator 7 through a pipeline (a sixth valve is installed on the pipeline), the cold side outlet of the regenerator 7 is connected to the cold side inlet of the preheater 8, the cold side outlet of the preheater 8 is connected to the side inlet of the evaporator 2, the side outlet of the evaporator 2 is connected to the inlet of the generator through a pipeline (a seventh valve is installed on the pipeline), the outlet of the generator 19 is connected to the hot side inlet of the regenerator 7, the hot side outlet of the regenerator 7 is connected to the side inlet of the air-cooled condenser 4, the side outlet of the air-cooled condenser 4 is connected to the working fluid pump, the electricity generated by the generator 19 is connected to the power grid through the grid-connected inverter 9, and the pipeline between the cold side outlet of the evaporator 2 and the generator is connected to the hot side inlet of the air-cooled condenser 4 through a branch (an eighth valve is installed on the pipeline). The heat source input pipeline 11 is also provided with a branch line, which is equipped with a second valve 10. The second valve 10 is in a normally closed state. When the power generation system exceeds the rated operating conditions, the second valve 10 is opened to directly drain the excess heat source, thereby preventing the magnetic levitation expansion generator from being damaged by over-rated operation.

[0036] Furthermore, the heat source input to the heat source system is saturated steam containing starch at a temperature between 100-110°C. The saturated steam, serving as the heat source, undergoes heat exchange with the working fluid in the evaporator and is converted into condensed water. Because the saturated steam contains starch, a corresponding vacuum filter 3 is added to the system to ensure long-term, stable operation of the system and to allow the condensed water to be recycled within the system.

[0037] Since the saturated steam in the production process has only a slight positive pressure, the original treatment method is to directly connect it to the atmosphere through a pipeline and exhaust it through a pressure difference. Now it is necessary to collect the saturated steam discharged from the production lines in the entire factory and then transport it as input to the evaporator in the waste heat power generation system. The evaporator itself has pressure resistance, so in order to smoothly introduce the saturated steam into the evaporator, a vacuum filter 3 needs to be added to the system.

[0038] Furthermore, the evaporator 2, air-cooled condenser 4, magnetic expansion generator 19, and working fluid pump 5 are connected by pipelines, and the working fluid circulates in the pipelines of the system. The working fluid is a low-boiling point organic working fluid R245fa and R134a, mixed in a ratio of 8:2.

[0039] Heat exchange is completed within the evaporator between the heat source input system and the circulating fluid within the power generation cycle system; the high-pressure organic fluid vapor drives the turbine expander to perform work, converting thermal energy into mechanical energy and driving the generator to rotate. The power generation cycle system device includes an evaporator 2 preheater, a regenerator, a condenser, a magnetic levitation expansion generator, etc., and the power generation cycle system further includes a regenerator. The calculated regenerator pressure drop design value is 20kPa, resulting in an energy loss of approximately 20.53kW; the energy recovered by the regenerator is approximately 220kW. Considering that the system efficiency is approximately 10.65%, the recovered heat is converted into approximately 23.43kW of usable power. The difference between the two is approximately 2.9kW, which is the increased power generation of the system.

[0040] A variable frequency working fluid pump 5 for pressurizing the working fluid; an air-cooled condenser 4 for condensing the working fluid from gas to liquid; a magnetic levitation expansion generator 19 for converting thermal energy into electrical energy; and a regenerator 7 and a preheater 8 for increasing the thermal cycle efficiency of the overall system.

[0041] The evaporator 2 is a brazed heat exchanger. The evaporator uses at least one heat exchanger, and the heat exchanger types include tubular, brazed, and fully welded. It is best to connect three in parallel, two for use and one for backup.

[0042] All pipelines in the power generation system of this application should be insulated.

[0043] The working fluid pump 5 is a variable frequency working fluid pump, which changes its frequency according to the flow rate of the heat source. The variable frequency working fluid pump is further used to control the evaporation temperature of the evaporator by adjusting the flow rate of the working fluid.

[0044] Optimally, there are three evaporators 2. The heat source in the heat source input system is the saturated steam discharged from the system during process production. Multiple steam discharge straight pipes converge to the heat source input pipe 11. The heat source input pipe 11 leads to three branches (with first valves 12 installed on the branches) connected to the hot side inlet of the evaporator 2. The first valves 12 of two evaporators are in a normally open state, and the first valve 12 of the third evaporator 2 is in a normally closed state. The saturated steam discharged from the user's production process needs to be centrally introduced into the evaporator. Since there are multiple production process lines in the factory, each production line is equipped with a separate steam discharge straight pipe. Therefore, the heat source input system needs to add a tee to the original steam discharge straight pipe, so that the steam discharge straight pipes are connected in parallel and are centrally introduced into the hot side inlet of the evaporator of the power generation cycle system through the heat source input pipe. Furthermore, each steam discharge straight pipe is equipped with a separate valve. When a process production line is shut down for maintenance, the valve of this line is closed to prevent steam backflow.

[0045] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0046] The saturated steam in traditional industries (steel, cement, chemical, etc.) is mostly high-pressure saturated steam provided by power plants for cogeneration. The present invention provides an efficient solution for the direct discharge of low-temperature saturated steam in the food processing industry.

[0047] like Figure 1 As shown, the present invention discloses an ORC magnetic levitation power generation system for utilizing waste heat from low-temperature saturated steam, suitable for the food processing industry. The system comprises a heat source input system and a power generation circulation system. The heat source input system collects saturated steam discharged from the process system via multiple straight steam discharge pipes into a heat source input pipe. This heat source input pipe then leads to three branches connected in series with the evaporators. The three evaporators are connected in parallel, with the first valves of the branches on two evaporators in a normally open state and the first valve of the branch on the third evaporator in a normally closed state.

[0048] The power generation cycle system includes an evaporator for converting the working fluid from liquid to gas; a variable-frequency working fluid pump for pressurizing the working fluid; an air-cooled condenser for condensing the working fluid from gas to liquid; a magnetic levitation expansion generator for converting thermal energy into electricity; a regenerator and preheater to increase the overall system's thermal cycle efficiency; a grid-connected inverter for connecting power to the grid; and a vacuum filter for providing vacuum and filtering saturated steam containing starch. The heat source input pipeline also requires a branch with a second valve. This valve is normally closed. When the power generation system reaches rated operating conditions, the second valve is opened to directly discharge excess heat. This prevents the magnetic levitation expansion generator from operating beyond its rated capacity and causing damage.

[0049] The regenerator is arranged in series between the magnetic levitation expansion generator and the air-cooled condenser, and the cold end outlet of the variable frequency working fluid pump serves as the input of the regenerator; the circulating working fluid flowing out of the working fluid pump returns and flows through the regenerator before flowing into the preheater.

[0050] The present application is equipped with a vacuum filter. Since the heat source is saturated steam containing starch at 100-110°C with a slightly positive pressure, the evaporator has pressure resistance and the steam cannot pass through smoothly under normal circumstances. Therefore, a vacuum filter needs to be introduced at the hot end outlet of the evaporator to meet the state of slightly negative pressure at the evaporator outlet so that the steam can pass through the evaporator smoothly. In addition, this device has a filtering function that can filter the condensed water containing starch condensed from the evaporator and filter out the starch residue in the condensed water.

[0051] Working process:

[0052] Before the system is put into operation, the third valve 13 and the fourth valve 14 are closed, the fifth valve 15 is opened, and the organic working medium is injected into the liquid storage tank 6 through the water inlet.

[0053] When the liquid level in liquid storage tank 6 reaches the required system level, the third valve 13 and the fifth valve 15 are closed, and the fourth valve 14 and the sixth valve 16 are opened. The organic medium, acting as a carrier for steam heat energy transfer, is pumped from liquid storage tank 6 by variable frequency working medium pump 5, and the working medium speed is slowly increased. The second valve 10 is closed, the first valve 12 is opened, and the vacuum pump in vacuum filter 3 is simultaneously turned on, introducing saturated starch-containing steam at 100-110°C into the evaporator. In evaporator 2, the saturated steam exchanges heat with the organic working medium, while simultaneously recording parameters such as temperature and pressure before the evaporator and after the air-cooled condenser. Before operation, the eighth valve in front of the magnetic levitation expansion generator is opened and the seventh valve 17 is closed. When the pressure difference reaches a certain value, the eighth valve 18 is closed and the seventh valve in front of the magnetic levitation expansion generator is opened to transport the high-pressure steam generated by the working medium absorbing heat through the evaporator to the magnetic levitation expansion generator, and expand the working medium through the radial turbine to do work, thereby converting the heat energy into electrical energy output; after completing the above process, the low-pressure gas-liquid mixed working medium after the energy is released will be discharged at the outlet of the expander generator and transported to the air-cooled condenser of the regenerator in turn to be condensed into liquid.

[0054] Under the action of the working fluid circulation pump, the liquid working fluid is pressurized to have a higher evaporation temperature, and enters the evaporator in a liquid state to complete the absorption of energy generated by the high-temperature heat source, and then forms high-pressure steam to enter the expander to perform work; through the infinite cycle of the above process, the process of converting waste heat resources into high-quality electrical energy is realized.

[0055] When the system stops running, close the fourth valve and the sixth valve on the pipeline, open the third valve, and re-inject the working fluid into the liquid storage tank.

[0056] like Figure 2As shown, the heat source first enters the evaporator, undergoes heat exchange, and forms condensed water. This condensed water then enters the vacuum filter and the preheater, ultimately forming softened water at 85-90°C. The softened water from the preheater is then used by a plate heat exchanger to heat the factory, meeting the heating needs of a 3,000-square-meter factory. The circulating water, finally cooled to 50-60°C, is returned to the steam boiler, achieving a closed-loop, efficient use of steam throughout the system. The heat delivery pipeline is used to deliver waste heat to heat users, allowing them to utilize it. After use, the waste heat carrier's temperature drops and is returned to the factory via the return pipeline, completing a complete cycle and fully utilizing the factory's waste heat.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A low-temperature saturated steam waste heat power generation system suitable for the food processing industry, characterized by: include: Heat source input system and power generation cycle system, The heat source input system includes a heat source and an evaporator, wherein the heat source is connected to the hot side inlet of the evaporator through a heat source input pipeline, the hot side outlet of the evaporator is connected to the inlet of the vacuum filter, the outlet of the vacuum filter is connected to the hot side inlet of the preheater, and the hot side outlet of the preheater discharges softened water; The power generation cycle system includes an evaporator, a generator, an air-cooled condenser, a working fluid pump, a liquid storage tank, a regenerator, a preheater, and a grid-connected inverter. The water outlet of the liquid storage tank is connected to the working fluid pump through a pipeline, and the other end of the working fluid pump is connected to the water return port of the liquid storage tank through a pipeline. The pipeline between the working fluid pump and the water return port of the liquid storage tank is connected to the cold side inlet of the regenerator through a pipeline, the cold side outlet of the regenerator is connected to the cold side inlet of the preheater, the cold side outlet of the preheater is connected to the cold side inlet of the evaporator, the cold side outlet of the evaporator is connected to the generator inlet, the generator outlet is connected to the hot side inlet of the regenerator, the hot side outlet of the regenerator is connected to the hot side inlet of the air-cooled condenser, the hot side outlet of the air-cooled condenser is connected to the working fluid pump, the electricity generated by the generator is connected to the power grid through the grid-connected inverter, and the pipeline between the cold side outlet of the evaporator and the generator is connected to the hot side inlet of the air-cooled condenser through a branch.

2. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1, characterized in that: The evaporator adopts at least one heat exchanger, and the evaporator is a tubular heat exchanger, a brazing heat exchanger or a fully welded heat exchanger.

3. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1 is characterized by: The pipelines of this power generation system are all insulated.

4. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1 is characterized by: The working fluid pump adopts a variable frequency working fluid pump, and the frequency is changed according to the flow change of the heat source.

5. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1 is characterized by: There are three evaporators. The heat source in the heat source input system is saturated steam discharged from the system during process production. Multiple steam discharge straight pipes converge into the heat source input pipe. The heat source input pipe leads to three branches connected to the hot side inlet of the evaporator. The first valves of two evaporators are in the normally open state, and the first valve of the third evaporator is in the normally closed state.

6. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1 is characterized by: A branch is also provided on the heat source input pipeline, on which a second valve is installed. The second valve is in a normally closed state. When the power generation system reaches the rated operating condition, the second valve is opened to directly discharge the excess heat source.

7. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1, characterized in that: The generator is a magnetic levitation expansion generator.

8. The low-temperature saturated steam waste heat power generation system suitable for the food processing industry according to claim 1 is characterized by: The working fluid is low-boiling-point organic working fluids R245fa and R134a, which are mixed in a ratio of 8:2.

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