Pasteurization device and process with cooperation of expansion refrigeration and microwave heating
By using a pasteurization device and process that combines expansion refrigeration and microwave heating, the problems of high energy consumption, poor temperature control accuracy, and large equipment footprint of traditional pasteurization processes have been solved, achieving high efficiency, energy saving, and improved product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QICHENG SUSPENSION TECH (XIAN) CO LTD
- Filing Date
- 2026-02-13
- Publication Date
- 2026-04-24
AI Technical Summary
Traditional pasteurization processes suffer from high energy consumption, poor temperature control accuracy, large equipment footprint, and the inability to achieve precise coordinated control of heating and cooling processes, resulting in product quality loss and energy waste.
The device and process employ a combination of expansion cooling and microwave heating, and through a three-stage preheating architecture, a two-stage cooling architecture, and an energy closed-loop design, combined with a ring array magnetron microwave heater and a turbine expander, it achieves energy cascade utilization and precise temperature control.
It achieves high efficiency and energy saving (energy consumption reduced by 52%), improved product quality (vitamin C retention rate increased by 18%), and compact equipment (land area reduced by 35%), while avoiding the defects of traditional heating and cooling.
Smart Images
Figure CN121910046A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of food processing technology, specifically relating to a pasteurization device and process that combines expansion refrigeration and microwave heating, which is particularly suitable for continuous sterilization of heat-sensitive fluids such as liquid dairy products and fruit juices. Background Technology
[0002] Traditional pasteurization processes suffer from significant energy waste: the heating stage relies on steam or electric heating, and the cooling stage consumes a large amount of cooling water, resulting in generally low system thermal efficiency. Although existing heat pump or compressor refrigeration solutions can recover some heat energy, they have the following drawbacks: ① The compressor's energy efficiency ratio is significantly affected by ambient temperature; ② Refrigerants pose environmental risks; ③ Precise coordinated control of the heating and cooling stages cannot be achieved. In addition, conventional tubular / plate heaters have problems such as high thermal inertia and significant temperature fluctuations, which can easily lead to overheating of materials or incomplete sterilization. Cooling with cold water or ice water baths is time-consuming, and the sterilized products cool down too slowly, resulting in excessively long residence time in the high-temperature zone, which can lead to irreversible quality losses such as protein denaturation and vitamin decomposition.
[0003] In some complex food processing systems, there may be high-pressure gas resources (such as waste gas from other processes). Turbine expanders can not only consume these gases to generate cooling, but also recover the mechanical energy generated by their expansion work and convert it into heat energy, realizing the cascade utilization of energy. As a highly efficient refrigeration unit, it can precisely control the cooling rate and final temperature, ensuring that the product is removed from the high-temperature environment in the shortest possible time, effectively locking in nutrition and flavor.
[0004] Rapid cooling reduces the time products are exposed to dangerous temperature zones (4-60℃), lowering the risk of bacterial regrowth. Turbine expanders can be perfectly matched with heat exchangers, pumping systems, etc., in pasteurization lines to create more compact and efficient automated production lines. By achieving rapid cooling to ensure quality and save energy, it indirectly improves the efficiency, product quality, and economy of the pasteurization process. Summary of the Invention
[0005] This invention constructs a pasteurization device and process that combines expansion refrigeration and microwave heating, employing the following technical solution, with its core innovation being: Three-stage preheating architecture: The first-stage heat exchanger recovers waste heat from industrial exhaust gas, the precooling heat exchanger recovers waste heat from process liquids, the second-stage heat exchanger recovers heat energy converted from the mechanical energy of the turbine expander to reach the final preheating temperature, and the magnetron microwave completes the final heating, realizing the cascade utilization of energy. Two-stage cooling architecture: It adopts a synergistic mode of pre-cooling with a pre-cooling heat exchanger (using the cold process liquid newly entering the system) and deep cooling at the cold end of the turbine expander, which improves the cooling rate by more than 40% compared with the traditional process. Energy closed-loop design: While the expansion end of the turbo expander generates cooling, its braking end converts mechanical energy into usable thermal energy through frictional heat generation, achieving a comprehensive system energy efficiency of 85%. Process liquid self-circulation: The cooling capacity of the precooling heat exchanger comes from the cold process liquid newly entering the system, and the heat recovery of the process liquid after sterilization preheats the process liquid before sterilization.
[0006] Preferably, the ring array magnetron microwave heater has 5 magnetrons arranged in a 72° circumference, with an operating frequency of 2450MHz±50MHz, and is coupled to the process pipeline through a waveguide to achieve a temperature control accuracy of ±1℃ along the material axis.
[0007] Preferably, the turbine expander adopts a radial flow turbine design with an adjustable expansion ratio of 4:1 to 8:1. The braking end is equipped with a brake wheel coaxially connected to the expansion wheel, which converts mechanical energy with a speed of ≥120000rpm into heat energy of 100~150℃. The turbine expander bearings use fully dynamic pressure bearings. The oil-free characteristics of fully dynamic pressure bearings ensure the cleanliness of the system and do not contaminate the process liquid.
[0008] Preferably, the device integrates a PLC and a PID control module, dynamically adjusts the inlet pressure of the turbine expander through an electromagnetic proportional valve, and achieves closed-loop control of the sterilization temperature within ±0.5℃ in conjunction with an infrared temperature sensor.
[0009] In summary, the present invention has the following beneficial effects: Energy-saving features: Energy consumption is reduced by 52% compared to traditional processes, and a production line with an annual processing capacity of 10,000 tons can reduce carbon emissions by approximately 380 tons; Quality Improvement: The instantaneous nature of microwave heating reduces material heating time to within 15 seconds, increasing vitamin C retention by 18%. Microwaves (2450MHz) cause polar substances such as water molecules to vibrate 2.45 billion times per second, rapidly raising the internal temperature of the material to sterilization temperature (e.g., 72℃). Microwaves can penetrate materials to a depth of 5-10cm, achieving three-dimensional uniform heating and avoiding the "cold center" problem of traditional heating. Turbine expansion refrigeration reduces the product's exposure time in the dangerous temperature range (4-60℃), lowering the risk of bacterial regrowth. Compact structure: The modular design reduces the equipment's footprint by 35%, making it suitable for space-constrained renovation projects; Environmental advantages: The entire system uses air as the working fluid, avoiding the use of Freon refrigerants. Attached Figure Description
[0010] Figure 1System process flow diagram, showing the connection relationship of each component and the direction of medium flow; filter (1), pilot-operated pressure reducing valve (2), primary heat exchanger (3), secondary heat exchanger (4), magnetron annular array heater (5), precooling heat exchanger (6), turbine expander expansion end heat exchanger (7), throttle valve (8), filter (9), turbine expander expansion end outlet (10), turbine expander expansion end inlet (11), turbine expander brake end inlet (12), turbine expander brake end outlet (13), electromagnetic proportional valve (14), turbine expander (15).
[0011] Figure 2 : Schematic diagram of cross section of magnetron ring array microwave heater; magnetron and its waveguide (16), internal process pipeline (17), and reflective cavity (18). Detailed Implementation
[0012] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be noted that the process liquid described in this embodiment is milk, but those skilled in the art can replace it with other liquid food raw materials (such as fruit juice).
[0013] Description of the device structure in this embodiment: Preheating heat exchange system (e.g.) Figure 1 As shown), the first-stage heat exchanger (3): its hot end inlet is connected to the outlet of the pilot-operated pressure reducing valve (2) through a pipe, and is used to receive high-temperature and high-pressure exhaust gas (e.g., 80-100℃) purified by the filter (1). The cold end outlet is connected to the cold end inlet of the precooling heat exchanger (6) through a pipe, so that the milk is preheated to 20-30℃ for the first time; the second-stage heat exchanger (4): its hot end inlet is connected to the outlet of the turbine expander brake end (13), and receives the 100-150℃ high-temperature gas generated by the friction boosting of the turbine brake end; the hot end outlet is open to the atmosphere, and the cold end outlet is connected to the inlet of the annular array magnetron microwave heating device (5); the annular array magnetron microwave heater (5): includes 5 sets of magnetrons (16), which are evenly distributed around the circumference of the circular reflective cavity (18) at a 72° angle, and the process pipeline (17) is set in the center. The microwave frequency is preferably 2450MHz, and the power density is controlled at 0.5-2W / g; Pre-cooling heat exchange system (e.g.) Figure 1As shown), the precooling heat exchanger (6): its cold end is connected in series with the first-stage heat exchanger (3), and its hot end is connected to the expansion end heat exchanger (7) of the turbine expander to realize the recovery of residual heat from the sterilized milk; the expansion end heat exchanger (7): the cold end inlet is connected to the expansion end outlet (10) of the turbine expander, and the milk is deeply cooled by the -7~-5℃ cold energy generated by expansion refrigeration; the throttle valve (8): is set in the outlet pipeline of the expansion end heat exchanger (7) of the turbine expander, and the milk flow rate is controlled to 0.5-1.5m / s by adjusting the opening degree to ensure that the final output temperature is stable at 4±0.5℃; the turbine expander linkage structure: the turbine expander brake end inlet (12) draws in ambient air through the filter (9), and after being compressed and heated by the brake impeller, it is delivered to the hot end of the second-stage heat exchanger (4) from the brake end outlet (13) to form a closed loop for the reuse of brake heat energy.
[0014] The process steps in this embodiment are as follows: S1, Initial preheating stage: Milk enters the cold end of the primary heat exchanger (3) from the storage tank and exchanges heat with the 80°C waste gas introduced at the hot end, raising the temperature to 25°C. After heat exchange, the temperature of the waste gas drops to 30°C and enters the turbine expander (15) through the electromagnetic proportional control valve (14). S2, waste heat recovery stage: the preheated milk flows into the cold end of the precooling heat exchanger (6) and exchanges heat with the sterilized high-temperature milk (72°C) returned from the hot end, and the temperature rises to 45°C; S3, Secondary preheating stage: Milk enters the cold end of the secondary heat exchanger (4) and absorbs the heat of the 100℃ high-temperature gas output from the brake end of the turbine expander, raising the temperature to 58℃. S4, Precision heating stage: The milk flows through the process pipeline (17) of the ring array magnetron microwave heater (5). Under the uniform radiation of 5 sets of magnetrons (16), the temperature rises rapidly to 73°C within 2-3 seconds, reaching the pasteurization temperature and maintaining it for 15 seconds. S5, initial cooling stage: After sterilization, the milk returns to the hot end of the pre-cooling heat exchanger (6) and releases heat to the cold end of the newly entered cold milk, and the temperature drops to 45°C. S6, Deep Cooling Stage: Milk enters the hot end of the expansion end heat exchanger (7) of the turbine expander and exchanges heat with the -5℃ cold air introduced at the cold end. Combined with the flow rate control of the throttle valve (8), the final output temperature is 4℃. Note: The above embodiments should be presented in conjunction with the accompanying drawings (system process flow diagram). All technical features in the claims are supported in this embodiment.
[0015] Through the above-described embodiments, this invention successfully solves the pain points of traditional pasteurization processes, such as high energy consumption, poor temperature control accuracy, and large equipment footprint, providing an innovative solution for the green upgrading of the food industry. In addition, the unpredictability of this invention is also reflected in: the synergistic effect of microwave non-thermal effect and turbine expansion rapid cooling (rapid sterilization and inhibition of bacterial reactivation), and the three-stage preheating architecture that breaks through the bottleneck of heat recovery efficiency.
Claims
1. A pasteurization device and process that combines expansion refrigeration and microwave heating, characterized in that, It includes a preheating heat exchange system, a precooling heat exchange system, and a throttling device. The process liquid (referring to liquid food raw materials flowing through the sterilization system, including but not limited to milk, juice, etc.) enters the preheating heat exchange system and is heated to a preset temperature before entering the precooling heat exchange system to be rapidly cooled to a set temperature. The preheating heat exchange system includes a primary heat exchanger (3), a cold end of a precooling heat exchanger (6), a secondary heat exchanger (4), and a ring array magnetron microwave heater (5). The precooling heat exchange system includes a hot end of a precooling heat exchanger (6) and a turbine expander expansion end heat exchanger (7). The expansion end and braking end of the turbine expander (15) are coaxially connected. The throttling device is composed of a throttling valve (8) to control the flow rate of the process liquid.
2. According to claim 1, the primary heat exchanger (3) is characterized in that... The hot end inlet is connected to the outlet of the pilot-operated pressure reducing valve (2), the hot end outlet is connected to the inlet of the electromagnetic proportional control valve (14), and the high-temperature and high-pressure exhaust gas passes through the filter (1) and is connected to the inlet of the pilot-operated pressure reducing valve (2).
3. According to claim 1, the secondary heat exchanger (4) is characterized in that... The hot end inlet and the turbine expander brake end outlet (13) are connected. The hot end outlet is connected to the atmospheric environment. The turbine expander brake end inlet (12) is connected to the atmospheric environment through the filter (9). The air enters the secondary heat exchanger after being heated and pressurized by the friction of the turbine expander brake end impeller.
4. According to claim 1, the ring array magnetron microwave heater (5) is characterized in that five sets of magnetrons (16) are arranged in a circumferential array at a 72° angle inside a circular reflective cavity (18) and a process liquid pipeline (17) is provided.
5. The precooling heat exchanger (6) according to claim 1 is characterized in that... The cold end inlet is connected to the cold end outlet of the first-stage heat exchanger (3), and the cold end outlet is connected to the cold end inlet of the second-stage heat exchanger (4).
6. The heat exchanger (7) at the expansion end of the turbine expander according to claim 1, characterized in that... Its cold end inlet is connected to the expansion end outlet (10) of the turbine expander, and the outlet is connected to the atmospheric environment.
7. According to claim 1, a temperature measuring device is provided at the connection of the primary heat exchanger (3), the precooling heat exchanger (6), the secondary heat exchanger (4), the annular array magnetron microwave heater (5), and the expansion end heat exchanger (7) of the turbine expander.
8. As described in claim 1, the impeller at the braking end and the impeller at the expansion end of the turbine expander are coaxially connected, and the bearing of the turbine expander is a fully dynamic bearing.
9. The process liquid flow direction of the preheating heat exchange system and the precooling heat exchange system according to any one of claims 1-6 is as follows: cold end of primary heat exchanger (3) → cold end of precooling heat exchanger (6) → cold end of secondary heat exchanger (4) → cold end of annular array magnetron microwave heater (5) → hot end of precooling heat exchanger (6) → hot end of turbine expander expansion end heat exchanger (7) → throttle valve.
10. A pasteurization device and process that combines expansion refrigeration and microwave heating, characterized in that, Includes the following steps: First stage: Initial preheating: The process liquid first enters the cold end of the primary heat exchanger (3) and exchanges heat with the high-temperature and high-pressure exhaust gas from the filter (1) and the pilot pressure reducing valve (2), raising the temperature to 20-30℃; Second stage: Waste heat recovery: Enter the cold end of the precooling heat exchanger (6) to absorb the waste heat from the high-temperature process liquid after sterilization, and the temperature is further raised to 40-50℃; Third stage: Secondary preheating: The gas flows into the cold end of the secondary heat exchanger (4) and exchanges heat with the high-temperature gas output from the brake end outlet (13) of the turbine expander to reach a preheating final temperature of 55-60℃. Fourth stage: Precision heating: Enter the ring array magnetron microwave heating device (5), 5 sets of magnetrons (16) achieve uniform heating through 72° array radiation, and rapidly heat up to 72-75℃ pasteurization temperature in the process pipeline (17) in the circular reflective cavity (18); Fifth stage: Initial cooling: The high-temperature sterilization liquid is returned to the hot end of the pre-cooling heat exchanger (6) to transfer heat to the newly entered cold process liquid, and the temperature drops to 40-50℃; Sixth stage: Deep cooling enters the hot end of the expansion end heat exchanger (7) of the turbine expander and undergoes final heat exchange with the cold energy generated at the expansion end outlet (10) of the turbine expander. The flow rate is controlled by the throttle valve (8), and the final output temperature is stabilized at 4℃.