Waste heat warming large-scale vacuum freeze drying system and method

Abstract

The invention relates to a waste heat warming large vacuum freeze drying system which comprises a waste heat warming unit, a refrigeration unit and a vacuum unit which are connected with one another. The waste heat warming unit comprises a carbon dioxide compressor, a first plate heat exchanger, a heat storage tank, an electric auxiliary heater and a freeze-drying bin; the refrigeration unit comprises a two-stage screw compressor, a cold storage tank, an evaporative cooling tower, a second plate heat exchanger, a freezer and a third plate heat exchanger; the vacuum unit comprises a cold trap, a pre-pumping pump set and a maintaining pump set. The invention further relates to a waste heat warming large-scale vacuum freeze drying method. The method comprises the following steps: S1, a pre-cooling process; s2, a drying process; and S3, a defrosting process. High-temperature heating of the partition plate in the one-time drying process is achieved through waste heat warming, the product quality and the drying efficiency are guaranteed, and energy consumption of the freeze dryer can be greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of freeze drying, and in particular relates to a large-scale vacuum freeze drying system and method using waste heat to increase temperature. Background Art

[0002] In the field of modern food processing, preserving the flavor and nutrients of food and extending the shelf life are crucial issues. Vacuum freeze-drying technology has therefore been widely used. This technology freezes food at low temperatures and then sublimates it under vacuum conditions, directly converting ice into water vapor, thereby greatly reducing the moisture in the food while retaining the nutrients, color and flavor of the food.

[0003] At present, vacuum freeze drying equipment has been widely used in industries such as food, medicine and biological products. However, traditional vacuum freeze drying equipment has some shortcomings, such as high energy consumption, low efficiency, long drying process time, etc. Especially for large vacuum freeze drying equipment, these shortcomings are particularly obvious, becoming a major bottleneck restricting its widespread application.

[0004] The energy-saving design of large-scale vacuum freeze-drying equipment needs to consider multiple complex factors, including the optimization of the heating system, the utilization of waste heat of the refrigeration system, and the heat transfer efficiency. Since large-scale equipment involves a larger freeze-drying bin and a larger water capture capacity, the compressor generates a large amount of low-temperature waste heat (below 50°C). Traditional freeze dryers often use water cooling or air cooling to dissipate the heat of the refrigeration unit, which wastes the waste heat. How to utilize waste heat and reduce energy consumption on large-scale freeze-drying equipment while maintaining efficient drying effects is an urgent problem to be solved.

[0005] In recent years, the application of waste heat recovery and reuse technology in industrial equipment has become increasingly common. This technology recovers the waste heat generated during the operation of the equipment through equipment such as heat exchangers, and reuses it to improve the overall energy efficiency. At present, there are freeze dryers that use the condensation heat generated by the refrigeration system to reuse it in the heating system of the freeze dryer, and convert it into the heat energy required for the drying process through the heat exchanger, so that the overall energy efficiency of the system can be improved. However, large-scale food freeze dryers are usually heated indirectly, and the materials are located between the heating partitions, mainly relying on radiation heat transfer. The highest heating temperature in a sublimation drying process is usually between 60℃ and 95℃, the water capture capacity of the cold trap accounts for about 70% of the total drying cycle, and the sublimation drying time accounts for about 30% of the total drying cycle. The compressor condenser inlet temperature of a general freeze dryer is usually less than 50℃, which cannot supply enough heat for the freeze-drying sublimation stage. In addition, the compressor efficiency generally decreases with the increase of the difference between the condensation temperature and the evaporation temperature. By connecting the carbon dioxide heat pump in series with the refrigeration compressor, on the one hand, the condensation temperature of the refrigeration compressor can be reduced and the refrigeration capacity can be increased; on the other hand, the partition temperature can be increased to accelerate the drying rate.

[0006] Therefore, developing a new large-scale vacuum freeze-drying equipment with waste heat heating is an effective way to solve the problems of high energy consumption and low efficiency in the existing technology. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a large-scale vacuum freeze-drying system and method using waste heat to increase temperature. From the perspective of waste heat recovery, the system and method combine with carbon dioxide heat pump technology to greatly improve heat utilization and reduce freeze-drying energy consumption. By recovering and utilizing waste heat, the system optimizes energy use and improves overall drying efficiency.

[0008] The present invention solves the technical problem by the following technical solutions:

[0009] A large-scale vacuum freeze-drying system using waste heat heating, comprising a waste heat heating unit, a refrigeration unit and a vacuum unit connected to each other;

[0010] The waste heat warming unit includes a carbon dioxide compressor, a first plate heat exchanger, a heat storage tank, an electric auxiliary heater and a freeze-drying bin. The condensing end of the carbon dioxide compressor is connected in parallel to the first plate heat exchanger and the heat storage tank. A fourth valve is arranged between the first plate heat exchanger and the heat storage tank. The first plate heat exchanger and the heat storage tank are connected to the electric auxiliary heater through a ninth valve and a first three-way valve, respectively. The electric auxiliary heater is connected to a heating plate arranged at intervals on the left side of the freeze-drying bin through a second valve. A material tray is arranged above the heating plate, and the heating plate is connected to the first plate heat exchanger through a tenth valve. A cold trap bottom heater is arranged at the bottom end of the cold trap on the right side of the freeze-drying bin. The cold trap bottom heater is connected to the electric auxiliary heater through a seventh valve and a first valve. An eighth valve is arranged on the heat storage tank.

[0011] The refrigeration unit includes a two-stage screw compressor, a cold storage tank, an evaporative cooling tower, a second plate heat exchanger, a freezer and a third plate heat exchanger, the evaporation end of the carbon dioxide compressor is connected to the two-stage screw compressor through the second plate heat exchanger and the second three-way valve, the second three-way valve is connected to the evaporative cooling tower, the second plate heat exchanger and the lower end of the evaporative cooling tower are commonly connected to the third plate heat exchanger, the third plate heat exchanger is connected to the freezer through the third three-way valve, the lower end of the third plate heat exchanger is connected to the cold storage tank through the fifth valve, and the cold storage tank is provided with a sixth valve;

[0012] The vacuum unit includes a cold trap, a pre-pumping pump group and a maintaining pump group. A cold trap coil is arranged in the cold trap, and the cold trap coil is connected to the first circulation pump. A drain valve is arranged at the bottom of the cold trap, and an exhaust valve is arranged at the top of the cold trap. The upper part of the cold trap is connected in parallel to the maintaining pump group, the first pre-pumping pump group and the second pre-pumping pump group. The maintaining pump group, the first pre-pumping pump group and the second pre-pumping pump group are respectively connected to the third vacuum solenoid valve, the first vacuum solenoid valve and the second vacuum solenoid valve.

[0013] Moreover, a second circulation pump is arranged between the first plate heat exchanger and the heat storage tank, the lower end of the third plate heat exchanger is connected to the first circulation pump through a fifth valve, the first circulation pump is connected to the vacuum unit, and the heating plate is connected to the first plate heat exchanger through the third circulation pump.

[0014] Moreover, the lower end of the first plate heat exchanger is connected in parallel to the second plate heat exchanger and the evaporation end of the carbon dioxide compressor through a first heat regenerator, and a first electronic expansion valve is arranged between the first heat regenerator and the second plate heat exchanger.

[0015] Moreover, the lower end of the second plate heat exchanger is connected in parallel to the third plate heat exchanger, the two-stage screw compressor and the freezer through a second heat regenerator, and a second electronic expansion valve is arranged between the second heat regenerator and the third plate heat exchanger.

[0016] Furthermore, the outlet end of the heating plate and the outlet end of the cold trap coil are commonly connected to a third valve.

[0017] A waste heat heating large-scale vacuum freeze drying method, characterized in that: the drying system is used, and the steps of the method are:

[0018] S1, precooling process: connecting the two-stage screw compressor and the second plate heat exchanger, connecting the second heat regenerator and the freezer, the heat storage tank and the second circulation pump, turning on the two-stage screw compressor and the carbon dioxide compressor, so that the temperature of the heat storage tank reaches the primary drying starting temperature;

[0019] S2, Drying process:

[0020] Precooling of the cold trap, the third plate heat exchanger is connected to the second regenerator, waiting for the cold trap temperature to drop to -35℃~~45℃ and maintain,

[0021] (1) Place the frozen material into the material tray of the freeze-drying chamber and evacuate the cold trap to a pressure below 100 Pa;

[0022] (2) The precooled heat transfer oil in the heat storage tank is transported to the heating plate until the heating plate is filled with the heat transfer oil, and the carbon dioxide compressor is used to heat the heat by utilizing the waste heat of the two-stage screw compressor. If the temperature of the heat transfer oil at the inlet of the heating plate does not reach the set drying heating temperature, the electric auxiliary heater is started;

[0023] (3) When the material temperature is consistent with the temperature of the heat transfer oil at the heating plate inlet and remains unchanged, the drying is completed, the two-stage screw compressor and the carbon dioxide compressor are turned off, and the air inlet valve is opened to a pressure of 133 Pa;

[0024] S3, defrosting process:

[0025] (1) Close the fourth valve and the ninth valve, open the eighth valve, the second valve, and the tenth valve, and connect the second circulation pump and the electric auxiliary heater with the first three-way valve to pump all the heat transfer oil into the heat storage tank;

[0026] (2) Close the eighth valve, the second valve, and the tenth valve, open the sixth valve, close the fifth valve, and pump all the cold heat transfer oil into the cold storage tank;

[0027] (3) Open the third valve, the ninth valve and the first valve, and start the second circulation pump to reduce the heat transfer oil in the cold storage tank to 0°C; close the third valve, the ninth valve and the first valve, and connect the second circulation pump and the electric auxiliary heater with the first three-way valve, and turn on the electric auxiliary heater until the ice on the surface of the cold trap coil melts and falls off;

[0028] (4) Open the seventh valve, close the first valve, heat the heater at the bottom of the cold trap, melt the ice water at the bottom of the cold trap into condensed water, and discharge the condensed water from the drain valve.

[0029] The advantages and beneficial effects of the present invention are:

[0030] 1. The present invention recovers and utilizes waste heat, optimizes energy use, and improves overall drying efficiency, providing a more efficient and energy-saving solution for the modern food processing field.

[0031] 2. The one-time drying of the present invention is a short-time high-energy consumption process. The waste heat of the compressor is recovered by the heat increase of the carbon dioxide heat pump, and the appropriate heating temperature of the material is ensured, the condensation temperature of the cold trap is reduced, the efficiency of the compressor is improved, and the total energy consumption is reduced. This process can save 100% of the heating energy consumption, which is about 40% energy saving compared with the traditional freeze dryer.

[0032] 3. The present invention can realize the drying process of raw materials suitable for high-temperature heating in the secondary drying stage.

[0033] 4. The present invention utilizes the heat medium of the hot liquid storage tank to perform defrosting operation. The freeze dryer can perform defrosting and quick freezing operations at the same time. Compared with the traditional freeze dryer, the drying cycle is shortened by about 3 hours, and the waste heat of the refrigeration unit in the pre-freezing process is recovered at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the present invention.

[0035] Description of Reference Numerals

[0036] Maintaining pump group 1, first pre-pumping pump group 2, second pre-pumping pump group 3, third vacuum solenoid valve 4, first vacuum solenoid valve 5, second vacuum solenoid valve 6, air inlet valve 7, cold trap coil 8, cold trap 9, drain valve 10, cold trap bottom heater 11, first valve 12, electric auxiliary heater 13, heating plate 14, material tray 15, second valve 16, freeze drying chamber 17, third valve 18, first circulation pump 19, fourth valve 20, first three-way valve 21, heat storage tank 22, first plate heat exchanger 23, first The second circulation pump 24, the first regenerator 25, the first electronic expansion valve 26, the carbon dioxide compressor 27, the second plate heat exchanger 28, the second three-way valve 29, the second regenerator 30, the two-stage screw compressor 31, the evaporative cooling tower 32, the second electronic expansion valve 33, the third plate heat exchanger 34, the fifth valve 35, the cold storage tank 36, the sixth valve 37, the seventh valve 38, the third three-way valve 39, the freezer 40, the eighth valve 41, the ninth valve 42, the third circulation pump 43, and the tenth valve 44. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0038] A waste heat heating large vacuum freeze drying system, the innovation of which is: comprising a waste heat heating unit, a refrigeration unit and a vacuum unit connected to each other;

[0039] The waste heat warming unit includes a carbon dioxide compressor 27, a first plate heat exchanger 23, a heat storage tank 22, an electric auxiliary heater 13 and a freeze-drying bin 17. The condensing end of the carbon dioxide compressor 27 is connected in parallel to the first plate heat exchanger 23 and the heat storage tank 22. A fourth valve 20 is arranged between the first plate heat exchanger 23 and the heat storage tank 22. The first plate heat exchanger 23 and the heat storage tank 22 are connected to the electric auxiliary heater 13 through a ninth valve 42 and a first three-way valve 21, respectively. The electric auxiliary heater 13 is connected to a heating plate 14 arranged at intervals on the left side of the freeze-drying bin 17 through a second valve 16. A material tray 15 is arranged above the heating plate 14. The heating plate 14 is connected to the first plate heat exchanger 23 through a tenth valve 44. A cold trap bottom heater 11 is arranged at the bottom end of the cold trap 9 on the right side of the freeze-drying bin 17. The cold trap bottom heater 11 is connected to the electric auxiliary heater 13 through a seventh valve 38 and a first valve 12. An eighth valve 41 is arranged on the heat storage tank 22.

[0040] Temperature probes are installed at the condensing end of the carbon dioxide compressor and the inlet end of the heating plate. The heat exchange medium in the first, second and third plate heat exchangers, the heat medium in the heat storage tank, the heating plate, the cold trap water collection pipeline and the heat transfer medium in the bottom heating pipe is heat transfer oil, which circulates through the first, second and third circulation pumps.

[0041] The refrigeration unit includes a two-stage screw compressor 31, a cold storage tank 36, an evaporative cooling tower 32, a second plate heat exchanger 28, a freezer 40 and a third plate heat exchanger 34. The evaporation end of the carbon dioxide compressor 27 is connected to the two-stage screw compressor 31 through the second plate heat exchanger 28 and the second three-way valve 29. The second three-way valve 29 is connected to the evaporative cooling tower 32. The lower ends of the second plate heat exchanger 28 and the evaporative cooling tower 32 are commonly connected to the third plate heat exchanger 34. The third plate heat exchanger 34 is connected to the freezer 40 through the third three-way valve 39. The lower end of the third plate heat exchanger 34 is connected to the cold storage tank 36 through the fifth valve 35. The cold storage tank 36 is provided with a sixth valve 37.

[0042] The vacuum unit includes a cold trap 9, a pre-pumping pump group and a maintaining pump group. A cold trap coil 8 is arranged in the cold trap 9, and the cold trap coil 8 is connected to the first circulating pump 19. A drain valve 10 is arranged at the bottom of the cold trap 9, and an exhaust valve 7 is arranged at the top of the cold trap 9. The upper part of the cold trap 9 is connected in parallel to a maintaining pump group 1, a first pre-pumping pump group 2 and a second pre-pumping pump group 3. The maintaining pump group 1, the first pre-pumping pump group 2 and the second pre-pumping pump group 3 are respectively connected to a third vacuum solenoid valve 4, a first vacuum solenoid valve 5 and a second vacuum solenoid valve 6.

[0043] Preferably, a second circulation pump 24 is arranged between the first plate heat exchanger 23 and the heat storage tank 22, the lower end of the third plate heat exchanger 34 is connected to the first circulation pump 19 through a fifth valve 35, the first circulation pump 19 is connected to the vacuum unit, and the heating plate 14 is connected to the first plate heat exchanger 23 through a third circulation pump 43.

[0044] Preferably, the lower end of the first plate heat exchanger 23 is connected in parallel to the second plate heat exchanger 28 and the evaporation end of the carbon dioxide compressor 27 through a first heat regenerator 25 , and a first electronic expansion valve 26 is arranged between the first heat regenerator 25 and the second plate heat exchanger 28 .

[0045] Preferably, the lower end of the second plate heat exchanger 28 is connected in parallel to the third plate heat exchanger 34 , the two-stage screw compressor 31 and the freezer 40 through a second heat regenerator 30 , and a second electronic expansion valve 33 is arranged between the second heat regenerator 30 and the third plate heat exchanger 34 .

[0046] Preferably, the outlet end of the heating plate 14 and the outlet end of the cold trap coil 8 are connected to a third valve 18 .

[0047] This embodiment takes the drying procedure as follows: pre-freezing at -35°C for 3 hours, drying temperature at 90°C for 5 hours, and drying temperature at 60°C for 10 hours, and the carbon dioxide waste heat recovery and heating system meets the heating process.

[0048] The invention discloses a large-scale vacuum freeze-drying method using waste heat to increase temperature, and its innovation lies in that the steps of the method are:

[0049] 1. Precooling process

[0050] Step 1: Open the first electronic expansion valve 26, open the second electronic expansion valve 33, and the second three-way valve 29, connect the two-stage screw compressor 31 and the second plate heat exchanger 28, open the third three-way valve 39, connect the second heat exchanger 30 and the freezer coil 40, open the first three-way valve 21 to connect the second circulation pump 24 and the heat storage tank 22, open the fourth valve 20, start the second circulation pump 24, start the two-stage screw compressor 31, and the carbon dioxide compressor 27. The lowest temperature of the material after freezing does not exceed its eutectic point temperature, the eutectic point temperature is -10℃~-35℃, and the time required for all materials to complete freezing is about 3 hours. At 1 hour, the temperature of the heat storage tank 22 reaches the primary drying temperature starting temperature of 90℃, close the second circulation pump 24, the carbon dioxide compressor 27, and the first electronic expansion valve 26, and the second three-way valve 29 connects the two-stage screw compressor 31 with the evaporative cooling tower 32 for 3 hours.

[0051] 2. Drying process

[0052] Step 2: Precooling the cold trap, the third three-way valve 39 connects the third plate heat exchanger 34 with the second regenerator 30, opens the fifth valve 35, turns on the first circulation pump 19, waits for the cold trap temperature to drop to -35°C ~ 45°C and maintains it, closes the second circulation pump 24, the carbon dioxide compressor 27, the first electronic expansion valve 26, and the second three-way valve 29 to connect the two-stage screw compressor 31 with the evaporative cooling tower 32.

[0053] Step 3: The frozen material enters the freeze-drying chamber 17.

[0054] Step 4: Open the first vacuum solenoid valve 5, the second vacuum solenoid valve 6, the first pre-pumping pump group 2, the second pre-pumping pump group 3. When the pressure of the cold trap 9 reaches below 100 Pa, open the maintenance pump group 1 and the third vacuum solenoid valve 4.

[0055] Step 5: Drying process: Open the eighth valve 41, the ninth valve 42, and the second valve 16 to transport the preheated heat transfer oil in the heat storage tank 22 to the heating plate 14 until the heating plate 14 is filled with the heat transfer oil.

[0056] Step 6: Close the eighth valve 41 , the ninth valve 42 , and the first three-way valve 21 to connect the second circulation pump 24 to the electric auxiliary heater 13 , and heat the carbon dioxide compressor 27 by utilizing the waste heat of the two-stage screw compressor 31 .

[0057] At 5 hours, the temperature starts to rise and exceeds the set temperature, the ninth valve 42 and the first three-way valve 21 are opened to connect the second circulation pump 24 with the heat storage tank 22 for heat storage, and if the heat storage temperature reaches the current program temperature, the carbon dioxide compressor 27 is stopped, the second circulation pump 24 is stopped, the fourth valve 20 and the ninth valve 42 are closed, and the third circulation pump 43 is turned on. The second three-way valve 29 connects the two-stage screw compressor 31 with the evaporative cooling tower 32.

[0058] Step 7: At the 15th hour, the material temperature is close to the temperature of the heat transfer oil at the inlet of the heating plate 14 and remains unchanged, indicating that the drying is completed. At this time, the two-stage screw compressor 31 and the carbon dioxide compressor 27 are turned off, and the air intake valve 7 is opened to a pressure of 133Pa. The maintenance pump group 1 and the third vacuum solenoid valve 4 are closed.

[0059] 3. Defrosting process

[0060] Step eight: close the fourth valve 20 and the ninth valve 42 , open the eighth valve 41 , the second valve 16 , and the tenth valve 44 , and connect the second circulation pump 24 and the electric auxiliary heater 13 through the first three-way valve 21 to pump all the heat transfer oil into the heat storage tank 22 .

[0061] Step nine: close the eighth valve 41, the second valve 16, and the tenth valve 44, open the sixth valve 37, close the fifth valve 35, and after all the cold heat transfer oil is pumped to the cold storage tank 36, close the first circulation pump 19, the fifth valve 35, and the sixth valve 37.

[0062] Step 10: The first three-way valve 21 connects the circulation pump and the liquid storage tank, the third valve 18 , the first valve 12 , and the ninth valve 42 are opened, and the circulation pump 24 is turned on.

[0063] Step 11: Open the seventh valve 38 , close the first valve 12 , heat the heater 11 at the bottom of the cold trap, melt the ice water at the bottom of the cold trap into condensed water, and discharge the condensed water from the drain valve 10 .

[0064] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate 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 and drawings.

Claims

1. A large-scale vacuum freeze-drying system using waste heat to increase temperature, characterized in that: It includes a waste heat heating unit, a refrigeration unit and a vacuum unit which are interconnected; The waste heat warming unit comprises a carbon dioxide compressor (27), a first plate heat exchanger (23), a heat storage tank (22), an electric auxiliary heater (13) and a freeze-drying chamber (17); the condensing end of the carbon dioxide compressor (27) is connected in parallel to the first plate heat exchanger (23) and the heat storage tank (22); a fourth valve (20) is arranged between the first plate heat exchanger (23) and the heat storage tank (22); the first plate heat exchanger (23) and the heat storage tank (22) are connected to the electric auxiliary heater (13) via a ninth valve (42) and a first three-way valve (21), respectively; the electric auxiliary heater The heater (13) is connected to a heating plate (14) arranged at intervals on the left side of the freeze-drying bin (17) through a second valve (16); a material tray (15) is arranged above the heating plate (14); the heating plate (14) is connected to the first plate heat exchanger (23) through a tenth valve (44); a cold trap bottom heater (11) is arranged at the bottom end of the cold trap (9) on the right side of the freeze-drying bin (17); the cold trap bottom heater (11) is connected to the electric auxiliary heater (13) through a seventh valve (38) and a first valve (12); an eighth valve (41) is arranged on the heat storage tank (22); The refrigeration unit comprises a two-stage screw compressor (31), a cold storage tank (36), an evaporative cooling tower (32), a second plate heat exchanger (28), a freezer (40) and a third plate heat exchanger (34); the evaporation end of the carbon dioxide compressor (27) is connected to the two-stage screw compressor (31) via the second plate heat exchanger (28) and a second three-way valve (29); the second three-way valve (29) is connected to the evaporative cooling tower (32); the lower ends of the second plate heat exchanger (28) and the evaporative cooling tower (32) are connected to the third plate heat exchanger (34); the third plate heat exchanger (34) is connected to the freezer (40) via a third three-way valve (39); the lower end of the third plate heat exchanger (34) is connected to the cold storage tank (36) via a fifth valve (35); and a sixth valve (37) is provided on the cold storage tank (36); The vacuum unit comprises a cold trap (9), a pre-pumping pump group and a maintenance pump group. A cold trap coil (8) is arranged in the cold trap (9), and the cold trap coil (8) is connected to the first circulation pump (19). A drain valve (10) is arranged at the bottom of the cold trap (9), and an exhaust valve (7) is arranged at the top of the cold trap (9). The upper part of the cold trap (9) is connected in parallel to a maintenance pump group (1), a first pre-pumping pump group (2) and a second pre-pumping pump group (3). The maintenance pump group (1), the first pre-pumping pump group (2) and the second pre-pumping pump group (3) are respectively connected to a third vacuum solenoid valve (4), a first vacuum solenoid valve (5) and a second vacuum solenoid valve (6).

2. The waste heat heating large-scale vacuum freeze-drying system according to claim 1 is characterized in that: A second circulation pump (24) is arranged between the first plate heat exchanger (23) and the heat storage tank (22); the lower end of the third plate heat exchanger (34) is connected to the first circulation pump (19) via a fifth valve (35); the first circulation pump (19) is connected to the vacuum unit; and the heating plate (14) is connected to the first plate heat exchanger (23) via a third circulation pump (43).

3. The waste heat heating large-scale vacuum freeze-drying system according to claim 1 is characterized in that: The lower end of the first plate heat exchanger (23) is connected in parallel to the second plate heat exchanger (28) and the evaporation end of the carbon dioxide compressor (27) through a first heat regenerator (25), and a first electronic expansion valve (26) is arranged between the first heat regenerator (25) and the second plate heat exchanger (28).

4. The waste heat heating large-scale vacuum freeze-drying system according to claim 1 is characterized in that: The lower end of the second plate heat exchanger (28) is connected in parallel to the third plate heat exchanger (34), the two-stage screw compressor (31) and the freezer (40) through a second heat regenerator (30), and a second electronic expansion valve (33) is arranged between the second heat regenerator (30) and the third plate heat exchanger (34).

5. The waste heat heating large-scale vacuum freeze-drying system according to claim 1 is characterized in that: The outlet end of the heating plate (14) and the outlet end of the cold trap coil (8) are connected to a third valve (18).

6. A large-scale vacuum freeze-drying method using waste heat to increase temperature, characterized in that: Using the drying system according to any one of claims 1 to 5, the steps of the method are: S1, precooling process: connecting the two-stage screw compressor (31) and the second plate heat exchanger (28), connecting the second heat regenerator (30) and the freezer (40), the heat storage tank (22) and the second circulation pump (24), starting the two-stage screw compressor (31) and the carbon dioxide compressor (27), so that the temperature of the heat storage tank (22) reaches the primary drying starting temperature; S2, Drying process: (1) Precooling the cold trap, the third plate heat exchanger (34) is connected to the second regenerator (30), and the temperature of the cold trap is waited to drop to -35°C to 45°C and maintained. (2) placing the frozen material into the material tray (15) of the freeze-drying chamber (17), and evacuating the cold trap (9) to a pressure below 100 Pa; (3) The precooled heat transfer oil in the heat storage tank (22) is transported to the heating plate (14) until the heating plate (14) is filled with the heat transfer oil, and the heat transfer oil is heated by the carbon dioxide compressor (27) using the waste heat of the two-stage screw compressor (31). If the temperature of the heat transfer oil at the inlet of the heating plate (14) does not reach the set drying and heating temperature, the electric auxiliary heater (13) is started; (4) When the material temperature is consistent with the temperature of the heat transfer oil at the inlet of the heating plate (14) and remains unchanged, the drying is completed, the two-stage screw compressor (31) and the carbon dioxide compressor (27) are turned off, and the air inlet valve (7) is opened to a pressure of 133 Pa; S3, defrosting process: (1) The fourth valve (20) and the ninth valve (42) are closed, and the eighth valve (41), the second valve (16), and the tenth valve (44) are opened. The first three-way valve (21) connects the second circulation pump (24) and the electric auxiliary heater (13) to pump all the heat transfer oil into the heat storage tank (22); (2) closing the eighth valve (41), the second valve (16), and the tenth valve (44), opening the sixth valve (37), closing the fifth valve (35), and pumping all the cold heat transfer oil into the cold storage tank (36); (3) Open the third valve (18), the ninth valve (42) and the first valve (12), and start the second circulation pump (24) to reduce the temperature of the heat transfer oil in the cold storage tank (36) to 0°C; close the third valve (18), the ninth valve (42) and the first valve (12), connect the second circulation pump (24) and the electric auxiliary heater (13) through the first three-way valve (21), and start the electric auxiliary heater (13) until the ice on the surface of the cold trap coil (8) melts and falls off; (4) Open the seventh valve (38), close the first valve (12), heat the heater (11) at the bottom of the cold trap, melt the ice water at the bottom of the cold trap into condensed water, and discharge the condensed water from the drain valve (10).

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