Heat recovery energy-saving system and method for forced cooling process of powder curing workpiece

Abstract

The invention belongs to the technical field of industrial energy saving, and discloses a heat recovery energy-saving system and method in the forced cooling process of a powder curing workpiece. According to the device, online heat energy conversion and direct utilization can be achieved. Recycled heat is efficiently converted into heat energy which can be directly utilized by a production line, the heat energy is directly applied to the following key links to replace primary energy consumption, and heat energy is provided for a hot pure water direct injection system and a pure water tank in the last process of pretreatment in normal shifts in summer. And normal shifts in winter are used for preheating tap water entering the pure water preparation system.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial energy conservation, and in particular relates to a heat recovery energy-saving system and method for a forced cooling process of a powder solidified workpiece. Background Art

[0002] In powder coating processes (such as plastic spraying and powder coating), the workpiece is heated in a curing oven to a set temperature (usually 180-220°C or higher) to melt, level, and crosslink the powder. After curing, the hot workpiece must be quickly cooled to a workable temperature (≤60°C) to meet the needs of subsequent processes (such as inspection, packaging, and shipping) or to improve production efficiency.

[0003] Currently, forced air cooling is commonly used in production lines. This involves using a high-power fan to blow ambient air or simply treated outdoor air onto the surface of the high-temperature workpiece for forced convection cooling. The cooled high-temperature air is usually discharged directly into the environment.

[0004] Powder-cured workpieces (especially large, thick-walled parts) absorb a large amount of heat energy in the curing furnace. After curing, the workpieces need to be cooled rapidly to meet the requirements of subsequent processes. Forced air cooling, currently widely used, uses a large flow of air to blow directly across the surface of the hot workpiece for convective heat transfer. After heat exchange, the high-temperature air (usually with an initial temperature >180°C) is usually discharged directly into the environment without any effective utilization. This means that a considerable portion of the energy input during the curing process (often up to 20%-40% or even more of the total energy consumption) is completely wasted, resulting in extremely serious energy waste.

[0005] Although there are many types of industrial waste heat recovery technologies (such as heat exchangers, heat pipes, etc.), their application in the specific scenario of forced air cooling of powder solidified workpieces faces significant challenges, resulting in very few actual application cases: rapid temperature decay and sudden drop in heat energy: the workpiece is at a high temperature (>180°C) when it comes out of the furnace, but in the early stage of forced air cooling, its surface temperature drops very quickly. This means that in the area near the outlet of the cooling chamber, the exhaust gas temperature has been greatly reduced (to below 100°C). The recovery efficiency and economy of existing general waste heat recovery technologies for large flows in this low-temperature section will drop sharply, making it difficult to efficiently capture the heat energy released in the initial high-temperature stage.

[0006] Therefore, it is urgent to design a heat recovery and energy-saving system for the forced cooling process of powder solidified workpieces, which is optimized for the characteristics of the forced cooling process of powder solidified workpieces such as initial high temperature, rapid cooling, and large flow, and is efficient, reliable, and easy to integrate into the existing production line.

[0007] In addition, the related equipment in the existing technology often finds it difficult to take into account high recovery rate, system compactness, operational reliability and online integration convenience. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a heat recovery and energy-saving system and method for the forced cooling process of a powder solidified workpiece.

[0009] The technical solution adopted by the present invention to solve its technical problem is:

[0010] A heat recovery and energy-saving system for the forced cooling process of a powder solidified workpiece, the system comprising a forced cooling heat exchanger, a raw water tank, pure water preparation equipment, a pure water tank, a boiler, and a hot pure water direct injection device, wherein the input end of the forced cooling heat exchanger is connected to tap water via a first solenoid valve, so that tap water can be input into the forced cooling heat exchanger, the input end of the raw water tank is also connected to tap water via a second solenoid valve, so that tap water can also be input into the raw water tank, and the output end of the forced cooling heat exchanger is also connected to the input end of the raw water tank via the first valve. The raw water tank, the pure water preparation equipment, and the pure water tank are connected in sequence. The output end of the pure water tank is connected to the input end of the forced cooling heat exchanger through the second valve and the first water pump. The output end of the forced cooling heat exchanger is also connected to the pure water tank through the third valve. The output port of the pure water tank is also connected to the hot pure water direct injection device through the fourth valve and the second water pump. The output port of the pure water tank is also connected to the input end of the boiler through the second water pump and the fifth valve. The output end of the boiler is connected to the hot pure water direct injection device.

[0011] The forced cooling heat exchanger can convert the heat of the powder solidified workpiece during the forced cooling process into the liquid inside it. The raw water tank can provide tap water for the pure water preparation equipment. The pure water preparation equipment can prepare tap water into pure water. The pure water tank can store the pure water produced by the pure water preparation equipment. The boiler can heat the liquid. The hot pure water direct injection device can spray the liquid directly onto the workpiece to be painted.

[0012] Furthermore, plate heat exchangers are provided on both the output end and the input end of the boiler.

[0013] Furthermore, the forced cooling heat exchanger, the raw water tank, the pure water preparation equipment, the pure water tank, the boiler and the hot pure water direct injection device are connected by water pipes.

[0014] Furthermore, the hot pure water direct injection device includes a solenoid valve, a ball valve 7, a pressure gauge, a direct injection pipe and a fan-shaped nozzle. The solenoid valve and the ball valve are arranged in parallel, the ball valve and the direct injection pipe are connected through a water pipe, the direct injection pipe and the fan-shaped nozzle are threadedly engaged and connected together, the pressure gauge is arranged on the direct injection pipe, the solenoid valve and the ball valve can control the switch and flow rate of the hot fan-shaped nozzle, and the fan-shaped nozzle can spray hot pure water to the surface of the workpiece.

[0015] Furthermore, the direct injection pipe is made of SUS304 stainless steel, and the solenoid valve and the ball valve are both made of anti-corrosion materials.

[0016] Furthermore, the pure water preparation equipment is a reverse osmosis RO system.

[0017] Furthermore, the forced cooling heat exchanger adopts an efficient shell and tube structure verified by engineering, controls the liquid flow rate to be ≤0.8m / s, and maintains a stable local heat transfer coefficient of ≥2000kcal / (m 2 ·h·℃).

[0018] The heat recovery and utilization method of the heat recovery and energy-saving system in the forced cooling process of the powder solidified workpiece as described above comprises the following steps:

[0019] Step 1: Place the forced cooling heat exchanger in the high-temperature curing zone during the forced cooling process of the powder solidified workpiece. This allows the hot air in the curing furnace to pass through the forced cooling heat exchanger and then be discharged directly to the outside. The exhaust system in the high-temperature curing zone is converted to a variable frequency type, and the air volume is adjusted according to the temperature requirements to match the waste heat utilization demand.

[0020] Step 2: During normal winter shifts, the pure water preparation equipment has clear requirements for the tap water inlet temperature, usually 25°C. If the winter temperature is 5°C, the actual water output is only half of the design value of 25°C. Therefore, it is necessary to preheat the tap water in winter to increase the water output of the pure water preparation equipment:

[0021] The working principle of waste heat utilization during normal working hours in winter is as follows:

[0022] (1) Open the first solenoid valve and the first valve, close the second solenoid valve, and heat the tap water through the forced cooling heat exchanger to increase its temperature and flow into the raw water tank until the liquid meets the working water temperature of the pure water preparation equipment. The liquid in the raw water tank is converted into pure water by the pure water preparation equipment and stored in the pure water tank;

[0023] (2) Open the fifth valve and the second water pump, close the second valve, the third valve and the first water pump, and the pure water in the pure water tank flows into the boiler for heating and heating to reach the working temperature of the hot pure water direct injection device of 50-60℃, so as to prepare for the line body direct injection and the pure water tank;

[0024] (3) The pure water heated in the boiler flows into the hot pure water direct injection device for direct injection. The boiler input end is adjusted so that the direct injection pressure meets the process requirements.

[0025] Step 3: During normal working hours in summer, the temperature meets the working water temperature of the pure water preparation equipment, so the device provides heat energy for the last hot pure water direct injection system and pure water tank in the pre-treatment process:

[0026] The working principle of waste heat utilization during normal working hours in summer is as follows:

[0027] (1) Open the second solenoid valve and close the first solenoid valve. Tap water flows into the raw water tank. The liquid in the raw water tank is made into pure water by the pure water preparation equipment and stored in the pure water tank.

[0028] (2) Open the second valve, the third valve and the first water pump, close the first valve, and the pure water in the pure water tank flows into the forced cooling heat exchanger through the water pump for heating and then flows back to the pure water tank for use until it reaches the working temperature of the hot pure water direct injection device of 50-60°C, so as to prepare for the line body direct injection and the pure water tank;

[0029] (4) Open the fourth valve and the second water pump, close the fifth valve, and the pure water in the pure water tank flows into the hot pure water direct injection device for direct injection. Adjust the fourth valve so that the direct injection pressure meets the process requirements.

[0030] The advantages and positive effects achieved by the present invention are:

[0031] 1. The present invention can efficiently recycle waste heat. For the first time, a seasonal dual-mode heat exchange system is used to target and capture the sensible heat released by the workpiece during the initial high-temperature stage of 180℃-220℃ after curing, achieving a breakthrough waste heat recovery rate of >40%; in the winter mode, high-temperature waste heat above 80-120℃ is transferred to 5-10℃ tap water in a cascade manner, raising its temperature to the applicable temperature of 20-25℃ pure water equipment, directly replacing the electricity consumption of constant temperature air-conditioned rooms; in the summer mode, medium- and high-temperature waste heat of 100-130℃ is used to heat 25-30℃ pure water to the process temperature of 50-60℃ in one step, completely replacing boiler steam heating. According to actual measurements, the system can achieve the recovery of about 110k of heat per 10,000 air volume exhaust at the strong cooling point. Compared with the original situation without any recovery, the comprehensive recovery rate is >40%, which creatively solves the dual contradiction of low-level heat energy waste and high-level heat energy supply that has long existed in the coating field.

[0032] 2. This invention enables online heat energy conversion and direct utilization. Recovered heat is efficiently converted into heat energy that can be directly utilized by the production line and directly applied to the following key links, replacing primary energy consumption. During normal summer shifts, heat is provided to the final stage of pre-treatment, the hot pure water direct injection system and the pure water tank. During normal winter shifts, it is used to preheat tap water entering the pure water preparation system.

[0033] 3. The present invention has system integration and reliability, and is compact, reliable, and easy to integrate into the cooling station system of an existing or newly built powder spray curing production line, ensuring synchronization with the production line rhythm and stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1A structural connection diagram of the system of the present invention;

[0035] Figure 2 for Figure 1 The working status diagram of the system in normal shift waste heat utilization in winter;

[0036] Figure 3 for Figure 1 The working status diagram of the system in normal working hours during summer when the waste heat is utilized;

[0037] Figure 4 for Figure 1 A three-dimensional schematic diagram of the structural connection of a medium-heat pure water direct injection device. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the following examples. The following examples are descriptive rather than restrictive, and the scope of protection of the present invention cannot be limited by the following examples.

[0039] The various experimental operations involved in the specific embodiments are all routine techniques in the field. For parts not specifically annotated in this document, ordinary technicians in this field can refer to various commonly used reference books, scientific literature or related instructions, manuals, etc. before the filing date of this invention to implement them.

[0040] Example 1

[0041] A heat recovery and energy-saving system for the forced cooling process of a powder solidified workpiece, such as Figures 1 to 3 As shown, the system includes a forced cooling heat exchanger 1, a raw water tank 3, a pure water preparation device 4, a pure water tank 5, a boiler 6 and a hot pure water direct injection device 7. The input end of the forced cooling heat exchanger is connected to the tap water 2 through a first solenoid valve 8, and the tap water can be input into the forced cooling heat exchanger. The input end of the raw water tank is also connected to the tap water through a second solenoid valve 9, and the tap water can also be input into the raw water tank. The output end of the forced cooling heat exchanger is also connected to the input end of the raw water tank through a first valve 10. The raw water tank, the pure water preparation device, The pure water tanks are connected in sequence, the output end of the pure water tank is connected to the input end of the forced cooling heat exchanger through the second valve 11 and the first water pump 12, the output end of the forced cooling heat exchanger is also connected to the pure water tank through the third valve 13, the output port of the pure water tank is also connected to the hot pure water direct injection device through the fourth valve 14 and the second water pump 15, the output port of the pure water tank is also connected to the input end of the boiler through the second water pump 15 and the fifth valve 16, and the output end of the boiler is connected to the hot pure water direct injection device;

[0042] The forced cooling heat exchanger can convert the heat of the powder solidified workpiece during the forced cooling process into the liquid inside it, so that the thermal energy of the air during the forced cooling of the powder solid is converted into the temperature of the liquid in the heat exchanger, reducing energy consumption and improving energy utilization efficiency; the raw water tank can provide tap water for the pure water preparation equipment, the pure water preparation equipment can prepare tap water into pure water, and the pure water tank can store the pure water produced by the pure water preparation equipment, so that the hot pure water direct injection device in the pre-treatment equipment of the coating line can perform direct injection operation, the boiler can heat the liquid, and the hot pure water direct injection device can spray the liquid directly onto the workpiece to be painted. As the last step of pre-treatment before coating, the hot pure water direct injection device eliminates the chemical ions and impurities remaining on the surface of the workpiece through physical flushing of high-purity water, ensuring that the substrate reaches a "zero pollution" state before spraying.

[0043] The system significantly recovers the significant waste heat released during the forced cooling of high-temperature workpieces after curing, with a target heat recovery rate of >40%. This effectively captures the high-temperature heat released during the initial high-temperature phase. This recovered heat is efficiently converted into thermal energy that can be directly utilized by the production line. This system offers system integration and reliability. The compact, reliable design allows for easy integration into the cooling stations of existing or newly constructed powder coating and curing production lines, ensuring stable operation in sync with the production line's cycle time.

[0044] In this embodiment, plate heat exchangers (not shown in the figure) are provided on both the output end and the input end of the boiler to improve the thermal efficiency of boiler conversion and reduce energy waste.

[0045] In this embodiment, the forced cooling heat exchanger, raw water tank, pure water preparation equipment, pure water tank, boiler and hot pure water direct injection device are connected by water pipes, which is easy to install, low in cost and improves work efficiency.

[0046] In this embodiment, if Figure 4 As shown, the hot pure water direct injection device includes a solenoid valve 7-1, a ball valve 7-2, a pressure gauge 7-3, a direct injection pipe 7-4 and a fan-shaped nozzle 7-5. The solenoid valve and the ball valve are arranged in parallel, and the ball valve and the direct injection pipe are connected by a water pipe (not numbered in the figure). The direct injection pipe and the fan-shaped nozzle are threadedly engaged and connected together. The pressure gauge is arranged on the direct injection pipe. The solenoid valve and the ball valve can control the switch and flow rate of the hot fan-shaped nozzle. The fan-shaped nozzle can spray hot pure water to the surface of the workpiece. The device realizes 0.1-0.15MPa pressure-adjustable injection of pure water to ensure that the surface coverage of the workpiece reaches more than 98%.

[0047] Preferably, the direct injection pipe is made of SUS304 stainless steel, and the solenoid valve and the ball valve are both made of anti-corrosion materials.

[0048] In this embodiment, the forced cooling heat exchanger adopts an efficient shell-and-tube structure verified by engineering. By optimizing the flow channel layout and heat transfer surface enhancement technology, countercurrent heat transfer between the hot air side and the liquid side is achieved. The liquid flow rate is controlled to be ≤0.8m / s, so that the local heat transfer coefficient is stably maintained at ≥2000kcal / (m 2 ·h·℃), ensuring efficient transfer of gradient energy between high-temperature waste heat and liquid.

[0049] In this embodiment, the pure water preparation equipment is a reverse osmosis RO system.

[0050] A heat recovery and utilization method of a heat recovery and energy-saving system utilizing the aforementioned forced cooling process of a powder solidified workpiece comprises the following steps:

[0051] Step 1: Place the forced cooling heat exchanger 1 in the high-temperature curing zone during the forced cooling process of the powder solidified workpiece, so that the hot air in the curing furnace passes through the forced cooling heat exchanger 1 and is then directly discharged to the outside. The exhaust system in the high-temperature curing zone is converted to a variable frequency type, and the air volume is adjusted according to the temperature requirement to match the heat demand for waste heat utilization;

[0052] Step 2: During normal winter operation, pure water preparation equipment (especially reverse osmosis RO systems) has clear requirements for the tap water inlet temperature (usually 25°C). If the winter temperature is 5°C, the actual water output is only about half of the design value (25°C benchmark). Therefore, it is necessary to preheat the tap water in winter to increase the water output of the pure water preparation equipment:

[0053] like Figure 2 As shown, the working principle of waste heat utilization during normal working hours in winter is:

[0054] (1) Open the first solenoid valve 8 and the first valve 10, close the second solenoid valve 9, and heat the tap water through the forced cooling heat exchanger to increase its temperature and flow into the raw water tank until the liquid meets the working water temperature of the pure water preparation equipment. The liquid in the raw water tank is converted into pure water by the pure water preparation equipment 4 and stored in the pure water tank 5;

[0055] (2) Open the fifth valve 14 and the second water pump 15, close the second valve 11, the third valve 13 and the first water pump 12, and the pure water in the pure water tank flows into the boiler for heating and heating to reach the working temperature of the hot pure water direct injection device of 50-60°C, so as to prepare for the line body direct injection and the pure water tank;

[0056] (3) The pure water heated in the boiler flows into the hot pure water direct injection device for direct injection. The boiler input end is adjusted so that the direct injection pressure meets the process requirements.

[0057] Step 3: During normal working hours in summer, the temperature meets the working water temperature of the pure water preparation equipment, so the device provides heat energy for the last hot pure water direct injection system and pure water tank in the pre-treatment process:

[0058] The working principle of waste heat utilization during normal working hours in summer is as follows:

[0059] (1) Open the second solenoid valve 9 and close the first solenoid valve 8. Tap water flows into the raw water tank. The liquid in the raw water tank is converted into pure water by the pure water preparation device 4 and stored in the pure water tank 5.

[0060] (2) Open the second valve 11, the third valve 13 and the first water pump 12, close the first valve 10, and the pure water in the pure water tank 5 flows into the forced cooling heat exchanger 1 through the water pump 12 for heating and then flows back to the pure water tank 5 for use until it reaches the working temperature of 50-60°C of the hot pure water direct injection device 7, so as to prepare for direct injection of the line body and the pure water tank;

[0061] (4) Open the fourth valve 14 and the second water pump 15, close the fifth valve 16, and the pure water in the pure water tank flows into the hot pure water direct injection device for direct injection. Adjust the fourth valve 14 so that the direct injection pressure meets the process requirements.

[0062] The pure water preparation equipment 4 installed in the coating line works in conjunction with the forced cooling heat exchanger 1 to form a heat recovery system. During winter operation, tap water is directly introduced into the forced cooling, high-temperature zone. Frequency conversion is used to control the exhaust volume in this zone, allowing the hot air generated by the workpiece to undergo a large-surface, low-velocity countercurrent heat exchange with the tap water in the coils. This prolongs the residence time of the hot air within the coils, achieving sufficient heat exchange and ensuring a stable inlet temperature of above 10°C for the pure water system, with an optimal temperature of around 25°C. During summer operation, a water pump pumps ambient-temperature water from the pure water tank to the forced cooling, high-temperature coils. Frequency conversion is also used to adjust the exhaust volume, allowing the hot air generated by the workpiece to efficiently exchange heat with the pure water, raising the outlet water temperature to the required 50-60°C. This solution achieves a cascaded utilization of waste heat from the forced cooling zone by switching between seasonal modes: preheating the inlet water in a constant-temperature air-conditioned room in winter and heating the pure water in a boiler in summer, simultaneously addressing the issues of maintaining the pure water system temperature and providing heat energy for the process.

[0063] Example 2

[0064] Verify that the system operates normally during winter shifts as follows:

[0065] (1) Operating parameters

[0066] The average temperature of the workpiece after solidification: 185℃, the average temperature after solidification cooling: 115℃, the average temperature of the workpiece after final cooling is 60℃, the weight of the workpiece kg / h: 10000, the specific heat of the workpiece: 0.115Kcal / kg·℃, the heating tap water volume: 5.35m3 / h, the initial heating temperature: 10℃, the final heating temperature: 22℃, the specific heat of tap water: 1Kcal / kg·℃.

[0067] (2) Thermal effects of the calculation system

[0068] The heat used per hour in the high-temperature stage of the workpiece is: Q = workpiece specific heat * workpiece weight * (average temperature of the workpiece after solidification - average temperature after solidification and cooling) = 0.115 * 10000 * 70 = 80500 Kcal / h.

[0069] The workpiece cooling heat is: Q = workpiece specific heat * workpiece weight * (average workpiece temperature after solidification - average workpiece final cooling temperature) = 0.115 * 10000 * 125 = 143750 Kcal / h.

[0070] The heat absorbed by tap water is: Q = specific heat of tap water * amount of tap water heated * density of water * (final heating temperature - initial heating temperature) = 1*1000*5.35*12 = 64200Kcal / h.

[0071] (3) Calculate the thermal efficiency of the system

[0072] The heat transfer efficiency of the heat exchanger is: heat absorbed by tap water / heat utilized in the high-temperature stage of the workpiece = 64200 / 80500 = 0.80.

[0073] The waste heat recovery efficiency is: tap water absorption heat / workpiece cooling heat = 64200 / 143750 = 44.66%.

[0074] This experiment is the test result conducted under winter conditions, which verifies that the recovery rate of solidification heat in the strong cooling stage is greater than 40%.

[0075] Example 3

[0076] Verify that the system operates as follows during normal summer shifts:

[0077] (1) Operating parameters

[0078] The average temperature of the workpiece after curing is 185°C, the average temperature after curing cooling is 125°C, the average temperature of the workpiece after final cooling is 60°C, the weight of the workpiece kg / h is 10,000, the specific heat of the workpiece is 0.115Kcal / kg·°C, the direct injection volume of pure water for heating is 3m3 / h, the initial heating temperature is 30°C, the final heating temperature is 50°C, and the specific heat of pure water is 1Kcal / kg·°C.

[0079] (2) Thermal effects of the calculation system

[0080] The heat used per hour in the high-temperature stage of the workpiece is: Q = workpiece specific heat * workpiece weight * (average temperature of the workpiece after solidification - average temperature after solidification and cooling) = 0.115 * 10000 * 60 = 69000 Kcal / h.

[0081] The workpiece cooling heat is: Q = workpiece specific heat * workpiece weight * (average workpiece temperature after solidification - average workpiece final cooling temperature) = 0.115 * 10000 * 125 = 143750 Kcal / h.

[0082] The heat absorbed by pure water is: Q = specific heat of pure water * amount of pure water * density of water * (final heating temperature - initial heating temperature) = 1*1000*3*20 = 60000Kcal / h.

[0083] (3) Calculate the thermal efficiency of the system

[0084] The heat exchange efficiency of the heat exchanger is: the heat absorbed by tap water / the heat used in the high temperature stage of the workpiece = 60000 / 69000 = 0.87

[0085] The waste heat recovery efficiency is: tap water absorption heat / workpiece cooling heat = 60000 / 143750 = 41.7%

[0086] This experiment is the test result conducted under summer conditions, which verifies that the recovery rate of solidification heat in the strong cooling stage is greater than 40%.

[0087] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A heat recovery and energy-saving system for the forced cooling process of a powder solidified workpiece, characterized by: The system includes a forced cooling heat exchanger, a raw water tank, a pure water preparation device, a pure water tank, a boiler and a hot pure water direct injection device, wherein the input end of the forced cooling heat exchanger is connected to tap water through a first solenoid valve, and tap water can be input into the forced cooling heat exchanger. The input end of the raw water tank is also connected to tap water through a second solenoid valve, and tap water can also be input into the raw water tank. The output end of the forced cooling heat exchanger is also connected to the input end of the raw water tank through a first valve. The raw water tank, the pure water preparation device and the pure water tank are connected in sequence. The output end of the pure water tank is connected to the input end of the forced cooling heat exchanger through a second valve and a first water pump. The output end of the forced cooling heat exchanger is also connected to the pure water tank through a third valve. The output port of the pure water tank is also connected to the hot pure water direct injection device through a fourth valve and a second water pump in sequence. The output port of the pure water tank is also connected to the input end of the boiler through a second water pump and a fifth valve in sequence. The output end of the boiler is connected to the hot pure water direct injection device. The forced cooling heat exchanger can convert the heat of the powder solidified workpiece during the forced cooling process into the liquid inside it. The raw water tank can provide tap water for the pure water preparation equipment. The pure water preparation equipment can prepare tap water into pure water. The pure water tank can store the pure water produced by the pure water preparation equipment. The boiler can heat the liquid. The hot pure water direct injection device can spray the liquid directly onto the workpiece to be painted.

2. The system according to claim 1, wherein: Plate heat exchangers are provided on both the output end and the input end of the boiler.

3. The system according to claim 1, wherein: The forced cooling heat exchanger, the raw water tank, the pure water preparation equipment, the pure water tank, the boiler and the hot pure water direct injection device are connected by water pipes.

4. The system according to claim 1, wherein: The hot pure water direct injection device includes a solenoid valve, a ball valve 7, a pressure gauge, a direct injection pipe and a fan-shaped nozzle. The solenoid valve and the ball valve are arranged in parallel. The ball valve and the direct injection pipe are connected through a water pipe. The direct injection pipe and the fan-shaped nozzle are threadedly engaged and connected together. The pressure gauge is arranged on the direct injection pipe. The solenoid valve and the ball valve can control the switch and flow rate of the hot fan-shaped nozzle. The fan-shaped nozzle can spray hot pure water onto the surface of the workpiece.

5. The system according to claim 4, characterized in that: The direct injection pipe is made of SUS304 stainless steel, and the solenoid valve and the ball valve are both made of anti-corrosion materials.

6. The system according to claim 1, wherein: The pure water preparation equipment is a reverse osmosis RO system.

7. The system according to any one of claims 1 to 6, characterized in that: The forced cooling heat exchanger adopts a high-efficiency shell and tube structure verified by engineering, which controls the liquid flow rate to ≤0.8m / s and the local heat transfer coefficient to be stable and maintain ≥2000kcal / (m 2 ·h·℃).

8. A heat recovery and utilization method using the heat recovery and energy-saving system for the forced cooling process of a powder solidified workpiece according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: Place the forced cooling heat exchanger in the high-temperature curing zone during the forced cooling process of the powder solidified workpiece. This allows the hot air in the curing furnace to pass through the forced cooling heat exchanger and then be discharged directly to the outside. The exhaust system in the high-temperature curing zone is converted to a variable frequency type, and the air volume is adjusted according to the temperature requirements to match the waste heat utilization demand. Step 2: During normal winter shifts, the pure water preparation equipment has clear requirements for the tap water inlet temperature, usually 25°C. If the winter temperature is 5°C, the actual water output is only half of the design value of 25°C. Therefore, it is necessary to preheat the tap water in winter to increase the water output of the pure water preparation equipment: The working principle of waste heat utilization during normal working hours in winter is as follows: (1) Open the first solenoid valve and the first valve, close the second solenoid valve, and heat the tap water through the forced cooling heat exchanger to increase its temperature and flow into the raw water tank until the liquid meets the working water temperature of the pure water preparation equipment. The liquid in the raw water tank is converted into pure water by the pure water preparation equipment and stored in the pure water tank; (2) Open the fifth valve and the second water pump, close the second valve, the third valve and the first water pump, and the pure water in the pure water tank flows into the boiler for heating and heating to reach the working temperature of the hot pure water direct injection device of 50-60℃, so as to prepare for the line body direct injection and the pure water tank; (3) The pure water heated in the boiler flows into the hot pure water direct injection device for direct injection. The boiler input end is adjusted so that the direct injection pressure meets the process requirements. Step 3: During normal working hours in summer, the temperature meets the working water temperature of the pure water preparation equipment, so the device provides heat energy for the last hot pure water direct injection system and pure water tank in the pre-treatment process: The working principle of waste heat utilization during normal working hours in summer is as follows: (1) Open the second solenoid valve and close the first solenoid valve. Tap water flows into the raw water tank. The liquid in the raw water tank is made into pure water by the pure water preparation equipment and stored in the pure water tank. (2) Open the second valve, the third valve and the first water pump, close the first valve, and the pure water in the pure water tank flows into the forced cooling heat exchanger through the water pump for heating and then flows back to the pure water tank for use until it reaches the working temperature of the hot pure water direct injection device of 50-60°C, so as to prepare for the line body direct injection and the pure water tank; (4) Open the fourth valve and the second water pump, close the fifth valve, and the pure water in the pure water tank flows into the hot pure water direct injection device for direct injection. Adjust the fourth valve so that the direct injection pressure meets the process requirements.

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