CN118408336A - Disinfection storage process system and control method thereof - Google Patents

Abstract

The invention provides a disinfection storage process system and a control method thereof. The disinfection and storage process system comprises a control module, a high-temperature side unit for disinfecting products and a low-temperature side unit for refrigerating or freezing and storing the products, wherein a buffer water tank is arranged between the high-temperature side unit and the low-temperature side unit and is connected with a cooling tower of the low-temperature side unit in parallel; the control module controls the buffer water tank to recover heat of the condensation side of the low-temperature side unit, and simultaneously provides the heat recovered by the buffer water tank to the evaporation side of the high-temperature side unit. The invention improves the energy utilization rate of the disinfection storage process system, and can also cope with the fluctuation of the running water temperature caused by untimely adjustment of the load change of the secondary unit.

Description

Disinfection storage process system and control method thereof

Technical Field

The present invention relates to the technical field of disinfection storage process systems, and in particular to a disinfection storage process system capable of saving energy.

Background technique

As a traditional disinfection method, high temperature disinfection has been used for thousands of years. With the continuous improvement of technology, modern technology has introduced heat pump units for high temperature disinfection, and heat pump units or other units are used to store products after high temperature disinfection at low temperatures. The application of this technology has significantly improved the efficiency and effect of disinfection and storage.

Taking the disinfection and storage of milk as an example, this article discusses the application of heat pump technology in high-temperature disinfection and low-temperature storage, and analyzes the shortcomings and improvement directions of existing technologies.

At present, pasteurization is the main sterilization technology for milk. Pasteurization kills pathogens by controlling the temperature and holding time, taking advantage of the different reproduction rates of bacteria at different temperatures, while retaining some harmless or beneficial heat-resistant bacteria. This method can not only effectively kill harmful microorganisms in milk, but also retain the nutrients and flavor in milk to the greatest extent.

In addition to milk, other liquid beverages are also widely sterilized by pasteurization. The advantage of this method is that it can kill pathogens while maintaining the original quality and nutritional components of the beverage. It is a sterilization technology that takes into account both safety and taste.

The prior art with application number 201911280942.9 proposes a method for pasteurization of frozen concentrated milk, which provides refrigeration and heating for frozen concentrated milk and pasteurized milk respectively based on heat pump technology, thereby providing a pasteurization method with low energy consumption, high efficiency and good concentrated quality for the production of concentrated milk products, providing a low temperature environment of -0.5℃~-1℃ during refrigeration and a high temperature environment of 62~65℃ during heating. However, the system has certain limitations. Since it uses a single heat pump unit for cooling and heating, it cannot be flexibly adjusted according to changes in the system's cooling and heating loads. This results in low system energy efficiency and inevitable waste of some heat. The design of a single heat pump unit also limits the flexibility and adaptability of the system.

The prior art with application number 201110163144.5 proposes a transcritical carbon dioxide heat pump milk disinfection and cooling system, which is formed by connecting a compressor, a gas separator, a heat regenerator, an expansion valve, an evaporator, a gas-liquid separator and a pipeline in series. This system also has similar problems: a single heat pump is used for heating and cooling, and it cannot be adjusted according to the changes in the system's cold and hot loads, resulting in low system energy efficiency and unavoidable waste of some heat. In addition, the load adaptability of a single heat pump is poor, and the operating stability of the system is also difficult to ensure when facing different working conditions.

The prior art with application number 202211432983.7 proposes a pasteurization system and method based on high-temperature heat pump technology, which utilizes waste heat and combines heat pump technology to significantly reduce steam consumption in production through electric energy substitution, while improving system energy efficiency and reducing operating costs. Although the system uses two units, namely heat pump units and refrigeration units, the system uses the form of direct series connection of heat pump units and refrigeration units, which makes it difficult to effectively solve the risk of unstable water temperature and unstable unit operation caused by load mismatch between the two units.

Therefore, how to provide a secondary unit that can achieve cooling and heating to meet the process requirements while avoiding the energy waste problem of the secondary unit.

Summary of the invention

In order to solve the technical problem of energy waste in a secondary unit, the present invention proposes a disinfection storage process system and a control method thereof.

The disinfection storage process system proposed in the present invention comprises a control module, a high temperature side unit for disinfecting products and a low temperature side unit for refrigerating or freezing the products, a buffer water tank arranged between the high temperature side unit and the low temperature side unit, and the buffer water tank is connected in parallel with the cooling tower of the low temperature side unit;

The control module controls the buffer water tank to recover heat from the condensing side of the low-temperature side unit, and provides the heat recovered by the buffer water tank to the evaporating side of the high-temperature side unit.

Furthermore, the buffer water tank is connected to the precooling process heat exchanger through a precooling circulation pump. After the product is disinfected by the high-temperature side unit through a conveying pipeline, it exchanges heat with the precooling process heat exchanger, recovers part of the heat to the buffer water tank, and then is sent to the low-temperature side unit for storage.

Further, the control module controls the exhaust heat of the condensing side of the low-temperature side unit to be supplied to the buffer water tank first;

When the heat rejection of the condensing side of the low-temperature side unit is greater than the heat absorption required by the evaporation side of the high-temperature side unit, or the sum of the heat rejection of the condensing side of the low-temperature side unit and the heat recovered through the precooling process heat exchanger is greater than the heat absorption required by the evaporation side of the high-temperature side unit, the cooling tower is controlled to recover excess heat rejection of the condensing side of the low-temperature side unit.

Furthermore, a first circulation pump is provided on the condensing side water outlet pipe of the low-temperature side unit, a cooling tower regulating valve is provided on the water inlet pipe connecting the cooling tower and the first circulation pump, and a first regulating valve is provided on the first water inlet pipe connecting the buffer water tank and the first circulation pump.

Furthermore, the evaporation side of the low-temperature side unit exchanges heat with the terminal low-temperature process heat exchanger, a second circulation pump is provided on the evaporation side water outlet pipeline of the low-temperature side unit, and a first switching valve is provided on the water inlet pipe of the terminal low-temperature process heat exchanger connected to the second circulation pump; the water outlet side of the second circulation pump is connected to the buffer water tank through the first bypass branch and the first bypass valve.

Further, the condensing side of the high-temperature side unit exchanges heat with the terminal disinfection process heat exchanger, a third circulation pump is provided on the outlet water pipeline of the condensing side of the high-temperature side unit, and a second switching valve is provided on the water inlet pipe of the terminal disinfection process heat exchanger connected to the third circulation pump;

The water outlet side of the third circulation pump is connected to the buffer water tank through a second bypass branch and a second bypass valve.

Furthermore, a fourth circulation pump is provided on the evaporation side water inlet pipeline of the high temperature side unit.

The control method of the disinfection storage process system of the present invention is based on the above technical solution. In each control cycle, the frequency of the corresponding circulation pump is controlled and the opening of the corresponding valve is controlled in sections, so that the heat absorption water inlet temperature output by the buffer water tank is within the temperature range based on the water tank temperature set by the user.

Furthermore, when the inlet water temperature on the heat absorption side output by the buffer water tank is within a temperature range based on the water tank temperature set by the user, the set value of the heat rejection return water temperature and/or the set value of the pre-cooling recovery heat return water temperature are adjusted according to the real-time change of the inlet water temperature on the heat absorption side output by the buffer water tank.

Further, controlling the frequency of the corresponding circulation pump includes:

When the temperature difference corresponding to the heat rejection of the low-temperature side unit is less than the set temperature difference of the heat rejection, the first circulation pump is controlled to reduce the frequency, otherwise the first circulation pump is controlled to increase the frequency. The set temperature difference of the heat rejection is the difference between the set value of the heat rejection water outlet temperature and the set value of the heat rejection return water temperature.

Further, controlling the frequency of the corresponding circulation pump includes:

When the temperature difference corresponding to the heat absorption of the high-temperature side unit is less than the set temperature difference of the heat absorption, the fourth circulation pump is controlled to reduce the frequency, otherwise the fourth circulation pump is controlled to increase the frequency. The set temperature difference of the heat absorption is the difference between the heat absorption inlet water temperature and the heat absorption return water temperature setting value.

Furthermore, when the temperature difference corresponding to part of the heat recovered by the precooling process heat exchanger is less than the preset recovery temperature difference, the precooling circulation pump is controlled to reduce the frequency, otherwise the precooling circulation pump is controlled to increase the frequency. The preset recovery temperature difference is the difference between the set value of the precooling recovery heat return water temperature and the precooling recovery heat outlet water temperature.

Furthermore, the segmented control of the opening of the corresponding valve includes:

When the outlet water temperature of the buffer water tank supplied to the high temperature side unit is greater than T5 _max within a certain period of time, = T5 _set + △T, T5 _{is set to} the water tank temperature set by the user, 0＜△T＜15;

If the opening of the cooling tower regulating valve is less than the preset larger opening at this time, the opening of the cooling tower regulating valve is controlled to increase an opening adjustment range; otherwise, the first regulating valve is controlled to close an opening adjustment range.

Furthermore, when the outlet water temperature supplied by the buffer water tank to the high-temperature side unit is greater than T5 _max for a certain period of time and the opening of the corresponding valve is controlled in a segmented manner, the set value of the heat rejection return water temperature and/or the set value of the pre-cooling recovery heat return water temperature is set to the maximum value of the temperature range based on the water tank temperature set by the user, so that the frequency control of the corresponding circulation pump can be dynamically adjusted.

Further, after the corresponding temperature is set to the maximum value of the temperature range based on the water tank temperature set by the user, the heat absorption inlet temperature output by the buffer water tank is monitored; if the rising rate of the heat absorption inlet temperature decreases, the set value of the pre-cooling heat recovery return water temperature is reduced by one level until it drops to the water tank temperature set by the user; if the rising rate of the heat absorption inlet temperature remains unchanged or increases, a certain time is delayed to determine whether the outlet water temperature supplied by the buffer water tank to the high-temperature side unit is greater than T5 _max . If so, the set value of the pre-cooling heat recovery return water temperature is set to the water tank temperature set by the user. If not, enter the next control cycle.

Further, the opening degree of the corresponding valve is controlled by:

When the outlet water temperature of the buffer water tank supplied to the high temperature side unit is less than T5 _min within a certain period of time, = T5 _{is set} - △T; T5 _{is set to} the water tank temperature set by the user, 0＜△T＜15;

The first regulating valve is controlled to be in an open state, the cooling tower regulating valve is closed, and the set value of the heat rejection return water temperature and/or the set value of the pre-cooling recovery heat return water temperature is set to the minimum value of the temperature range based on the water tank temperature set by the user.

The present invention adopts a two-stage refrigeration heat pump unit in series, and adds a buffer water tank in the middle, which can not only effectively improve the utilization rate of energy, but also buffer and offset the risk of operating water temperature fluctuations caused by untimely load changes of the first and second stage units, thereby causing the unit to shut down for protection. The present invention can be applied to pasteurization processes and other process production processes with both cooling and heating requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

FIG. 1 is a diagram showing the overall system structure of the present invention.

FIG. 2 is a system structure diagram of the high temperature side unit of the present invention.

FIG3 is a system structure diagram of the low temperature side unit of the present invention.

FIG. 4 is an overall control flow chart of an embodiment of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although some features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

The disinfection storage process system of the present invention comprises a control module, a high temperature side unit for disinfecting products, a low temperature side unit for refrigerating or freezing products, and a buffer water tank.

The buffer water tank is arranged between the high temperature side unit and the low temperature side unit. It is a water tank shared by the high temperature side unit and the low temperature side unit. The buffer water tank is connected in parallel with the cooling tower of the low temperature side unit. The control module controls the buffer water tank to recover the heat on the condensing side of the low temperature side unit, and at the same time, provides the recovered heat to the evaporation side of the high temperature side unit. Through this setting, the present invention not only adopts a two-stage refrigeration heat pump unit in series, reduces the compression ratio of the compressor of each stage unit, and improves the energy efficiency of the unit operation, but also adopts an intermediate buffer water tank connection between the two-stage units to recover the excess heat of the low temperature side unit and supply it to the high temperature side, saving the energy consumption of the entire disinfection storage process system and improving the energy efficiency ratio.

In a further embodiment, the buffer water tank of the present invention is connected to the precooling process heat exchanger through a precooling circulation pump. After the product is sterilized by the high-temperature side unit through the delivery pipeline, it exchanges heat with the precooling process heat exchanger, recovers part of the heat to the buffer water tank, and then is sent to the low-temperature side unit for storage. In the prior art, the product after high-temperature sterilization is usually directly stored at low temperature through the terminal heat exchanger of the low-temperature side unit. However, the temperature of the product after high-temperature sterilization is usually high, and direct low-temperature storage will also cause energy waste. The present invention can not only recover part of the heat of the product after high-temperature sterilization through the precooling process heat exchanger, but also is more conducive to the next step of low-temperature storage.

Based on the above two embodiments, in a further embodiment, the control module of the present invention controls the heat rejection on the condensing side of the low-temperature side unit to be supplied to the buffer water tank first. When the heat rejection on the condensing side of the low-temperature side unit is greater than the heat absorption required on the evaporation side of the high-temperature side unit, or the sum of the heat rejection on the condensing side of the low-temperature side unit and the heat recovered by the precooling process heat exchanger is greater than the heat absorption required on the evaporation side of the high-temperature side unit, the cooling tower is controlled to recover the excess heat rejection on the condensing side of the low-temperature side unit. The cooling tower can remove the excess condensation heat (heat rejection) of the low-temperature side unit in a timely manner to prevent insufficient heat use of the high-temperature side unit during the production process, excessive refrigeration of the low-temperature side unit resulting in excessive condensation heat, and the high-temperature side unit being unable to effectively remove the condensation heat of the low-temperature unit, resulting in system failure.

In a specific embodiment, the present invention sets a first circulating pump on the condensing side water outlet pipeline of the low-temperature side unit, sets a cooling tower regulating valve on the water inlet pipe connected to the cooling tower and the first circulating pump, and sets a first regulating valve on the first water inlet pipe connected to the buffer water tank and the first circulating pump. The first circulating pump extracts water that absorbs the heat rejection of the condensation measurement of the low-temperature side unit and sends it to the cooling tower and/or the buffer water tank. The cooling tower regulating valve is used to adjust the excess heat rejection sent to the cooling tower, and the first regulating valve is used to adjust the heat rejection sent to the buffer water tank. By monitoring the temperature at the corresponding pipeline or the inlet and outlet, the frequency of the first circulating pump and the opening of the valve are adjusted to avoid excessive condensation heat caused by excessive refrigeration of the low-temperature side unit, and the high-temperature side unit cannot effectively eliminate the condensation heat of the low-temperature unit, resulting in system failure.

In one embodiment, the evaporation side of the low-temperature side unit exchanges heat with the terminal low-temperature process heat exchanger, and the terminal low-temperature process heat exchanger is used to provide a suitable low temperature for the product to be stored. A second circulation pump is provided on the outlet water pipeline of the evaporation side of the low-temperature side unit, and a first switching valve is provided on the water inlet pipe of the terminal low-temperature process heat exchanger connected to the second circulation pump. At the same time, the outlet water side of the second circulation pump is connected to the buffer water tank through the first bypass branch and the first bypass valve. In this embodiment, by setting the first bypass branch, water with unqualified temperature in the terminal low-temperature process heat exchanger can be extracted into the buffer water tank, thereby avoiding affecting the storage temperature of the product.

In a specific embodiment, the condensing side of the high-temperature side unit exchanges heat with the terminal disinfection process heat exchanger, a third circulation pump is provided on the outlet water pipeline of the condensing side of the high-temperature side unit, and a second switching valve is provided on the water inlet pipe of the terminal disinfection process heat exchanger connected to the third circulation pump; the outlet water side of the third circulation pump is connected to the buffer water tank through the second bypass branch and the second bypass valve. In this embodiment, by setting the second bypass branch, water with unqualified temperature in the terminal disinfection process heat exchanger can be extracted into the buffer water tank, thereby avoiding affecting the disinfection process temperature of the product.

In one embodiment, a fourth circulation pump is provided on the evaporation side water inlet pipeline of the high temperature side unit, and the heat absorption amount of the high temperature side unit is controlled by controlling the frequency of the fourth circulation pump.

In specific applications, the high temperature side unit may be a heat pump unit, and/or the low temperature side unit may be a refrigeration unit. By recycling the excess condensation heat of the refrigeration unit, it can be used for the evaporation heat absorption of the heat pump unit, thereby improving the energy utilization rate. Of course, in some application occasions, those skilled in the art can also use a heat pump unit for the low temperature side unit as needed.

Based on the above disinfection storage process system, the present invention also proposes a control method for the disinfection storage process. The control method controls the frequency of the corresponding circulation pump and the opening of the corresponding valve in each control cycle, so that the heat absorption water inlet temperature output by the buffer water tank is within the temperature range based on the water tank temperature set by the user. Different from the prior art, the temperature control of the buffer water tank of the present invention is not a fixed value, but around a fixed value (water tank temperature) set by the user, the temperature of the buffer water tank is controlled within a temperature range, so that the buffer water tank can buffer and offset the operating water temperature fluctuation caused by the untimely adjustment of the load changes of the first and second level units, thereby causing the risk of unit shutdown protection.

Referring to FIG4, when the heat absorption side inlet water temperature T5 output by the buffer water tank is within the temperature range [T5 _min , T5 _max ] based on the water tank temperature set by the user, _the set value T3 of the heat rejection return water temperature and/or the set value T7 of the precooling heat recovery return water temperature are _adjusted according to the real-time change of the heat absorption side inlet water temperature T5 output by the buffer water tank. For example, if the user sets the water tank temperature T5 _to 50°C and △T is 5°C, then the heat absorption side inlet water temperature T5 actually fluctuates within the range of [45, 55], which is normal. When the heat absorption side inlet water temperature T5 is 52°C, _the set value T3 of the heat rejection return water temperature and/or the set value T7 _of the precooling heat recovery return water temperature are also set to 52°C, which can improve the heat recovery capacity of the buffer water tank, thereby playing a buffering role when the heat absorption and heat rejection are inconsistent.

The present invention uses PID control to control the frequency of all circulating pumps. The specific control method is as follows:

;

in:

At the present moment The control module output corresponds to the frequency increment of the circulation pump.

is the frequency deviation at time k.

e(k-1) and e(k-2) are the frequency deviations at the previous moment and two moments before, respectively.

,and are proportional, integral and derivative gains respectively, ,and The value of is adjusted according to the actual working conditions. The default initial value is 0.1. The default initial value is 0.01. The initial value is 0. It is the sampling time interval, and it is recommended to be set to 30s.

Controlling the frequency of the corresponding circulation pump includes but is not limited to the following control methods.

When the temperature difference corresponding to the heat discharge of the low-temperature side unit is less than the set temperature difference of the heat discharge, the first circulation pump is controlled to reduce the frequency, otherwise the first circulation pump is controlled to increase the frequency, and the set temperature difference of heat discharge △T1 _{is set to the} difference between the heat discharge water temperature T1 and _the set value of the heat discharge return water temperature T3, △T1 ₌ T1-T3. By calculating the temperature difference on the corresponding official pipeline, it is determined whether the temperature difference corresponding to the heat discharge is less than the set temperature difference of the heat discharge. If it is less, the first circulation pump needs to be controlled to reduce the frequency, otherwise it needs to be increased, so as to buffer the temperature fluctuation of the water tank to meet the corresponding temperature range.

When the temperature difference corresponding to the heat absorption of the high-temperature side unit is less than the set temperature difference of the heat absorption, the fourth circulation pump is controlled to reduce the frequency, otherwise the fourth circulation pump is controlled to increase the frequency, and the set temperature difference of the heat absorption △T2 _{is set to the} difference between the heat absorption inlet temperature T5 and the heat absorption return water temperature set _value T4, △T2 ₌ T5-T4. This embodiment controls the frequency of the fourth circulation pump used by the high-temperature side unit to extract the heat absorption, so that the temperature fluctuation of the buffer water tank meets the corresponding temperature range.

When the temperature difference corresponding to the part of the heat recovered by the precooling process heat exchanger is less than the preset recovery temperature difference, the precooling circulation pump is controlled to reduce the frequency, otherwise the precooling circulation pump is controlled to increase the frequency, and the preset recovery temperature difference △T3 _{is set as} the difference between the set value T7 of the precooling recovery heat return water temperature and the precooling recovery heat outlet water temperature T6, △T3 ₌ T7 -T6. This is the control of another heat recovery circulation pump of the buffer water tank, and it is also to make the temperature fluctuation of the buffer water tank meet the corresponding temperature range.

The opening of the corresponding valve is controlled in sections, including:

When the outlet water temperature of the buffer water tank supplied to the high-temperature side unit is greater than T5 _max within a certain period of time, =T5 _set + △T, T5 _{is set to} the water tank temperature set by the user, 0＜△T＜15; if the opening of the cooling tower regulating valve is less than the preset larger opening at this time, the opening of the cooling tower regulating valve is controlled to increase an opening adjustment range; otherwise, the first regulating valve is controlled to close an opening adjustment range. In this embodiment, if the outlet water temperature of the buffer water tank supplied to the high-temperature side unit is greater than T5 _max , it means that the heat rejection of the low-temperature side unit recovered by the buffer water tank is greater than the heat absorption required by the high-temperature side unit. At this time, the opening of the cooling tower regulating valve needs to be further increased. If the opening of the cooling tower regulating valve is already very large, then the opening of the first regulating valve needs to be reduced to avoid overheating of the buffer water tank.

When the outlet water temperature of the buffer water tank supplied to the high temperature side unit is greater than T5 _max for a certain period of time, the corresponding valve opening is controlled in stages, and the set value of the heat rejection return water temperature and/or the set value of the precooling recovery heat return water temperature is set to the maximum value of the temperature range based on the user- _set water tank temperature, so that the control of the corresponding circulation pump frequency is dynamically adjusted. When T5>T5 _max , it means that the heat recovered by the buffer water tank is more than the heat consumed by the high temperature side unit. At this time, if the compliance _of T3 and T7 is also improved, the load change adjustment between the two-stage units can be buffered.

After setting the corresponding temperature to the maximum value of the temperature range based on the user-set water tank temperature, monitor the heat absorption inlet water temperature output by the buffer water tank; if the rising rate of the heat absorption inlet water temperature decreases, the set value of the pre-cooling heat recovery return water temperature is reduced by one level until it drops to the user-set water tank temperature; if the rising rate of the heat absorption inlet water temperature remains unchanged or increases, delay for a certain period of time to determine whether the outlet water temperature T5 supplied by the buffer water tank to the high-temperature side unit is greater than T5 _max . If so, _set the set value T7 of the pre-cooling heat recovery return water temperature to the user-set water tank temperature T5; if not, enter the next control cycle. After the buffer capacity of the buffer water tank is increased by one gear, if the water temperature of the buffer water tank still rises quickly, the set value T7 of the precooling heat recovery return water temperature is _set to the water tank temperature T5 set by the user. In this embodiment, the present invention only adjusts the set temperature of the precooling side, that is, only changes the heat absorption size of the precooling process heat exchanger, thereby affecting the heat absorption size of the terminal low-temperature process heat exchanger. The terminal low-temperature process heat exchanger needs to generate more heat to reduce the temperature of the product by the same temperature difference. When the temperature of the buffer water tank is rising, adjusting the set temperature of the precooling side can allow the precooling process heat exchanger to absorb more heat, thereby reducing the heat generated by the low-temperature side unit, so that less heat enters the buffer water tank. When the outlet water temperature of the buffer water tank supplied to the high-temperature side unit is greater than the upper limit of the water tank temperature, and the upper limit of the water tank temperature is greater than T5 _max , the cooling tower regulating valve is controlled to be fully opened, and then the first regulating valve is closed. The upper limit of the water tank temperature can be set, such as T5 _max +2 degrees, etc. By limiting the upper limit of the water tank temperature, the water tank temperature can be prevented from being too high.

When the outlet water temperature of the high-temperature side unit supplied by the buffer water tank is less than T5 _min within a certain period of time, =T5 _{is set} -△T; the first regulating valve is controlled to be in the open state, the cooling tower regulating valve is closed, and the set value of the heat rejection return water temperature and/or the set value of the pre-cooling recovery heat return water temperature is set to the minimum value of the temperature range based on the water tank temperature set by the user. In this embodiment, the outlet water temperature of the high-temperature side unit supplied by the buffer water tank is less than T5 _min , which means that either the heat rejection is not enough or the heat absorption is large. Therefore, the cooling tower can reduce the consumption of heat rejection and the buffer water tank can increase the recovery of heat rejection. The present invention adopts segmented control when the water temperature of the buffer water tank is high, and does not adopt segmented control when the temperature of the buffer water tank is low, because the buffer water tank has the function of storing heat energy in addition to the buffering effect. Therefore, when the temperature of the buffer water tank does not exceed the maximum value of the temperature range, the higher the temperature of the buffer water tank, the better.

When the outlet water temperature of the buffer water tank supplied to the high temperature side unit is lower than the lower limit of the water tank temperature, and the lower limit of the water tank temperature is lower than T5 _min , the first regulating valve is controlled to be fully opened, and then the cooling tower regulating valve is closed. This means that the buffer water tank should absorb all the heat to meet the temperature requirements of the buffer water tank, so the first regulating valve is fully opened first, and then the consumption channel of the cooling tower is closed.

Some specific embodiments of the present invention are described below with reference to the accompanying drawings.

As shown in Figures 1 to 3, the disinfection storage process system of the present invention includes a low-temperature side unit 1, a high-temperature side unit 6, a buffer water tank 9, a cooling tower 4, a terminal low-temperature process heat exchanger 8-1, a precooling process heat exchanger 8-2, a terminal disinfection process heat exchanger 8-3, a first circulation pump 2, a second circulation pump 7-1, a precooling circulation pump 7-2, a fourth circulation pump 5, a third circulation pump 7-3, a cooling tower regulating valve 3-1, a first regulating valve 3-2, a first bypass valve 3-3, a first switching valve 3-4, a second bypass valve 3-5, and a second switching valve 3-6.

The low temperature side unit includes a first compressor 10 , an evaporation side 11 of the low temperature side unit, a condensation side 12 of the low temperature side unit, and a first throttling device 13 .

The high temperature side unit includes a second compressor 17 , an evaporation side 15 of the high temperature side unit, a condensation side 14 of the high temperature side unit, and a second throttling device 16 .

The condensing side of the low-temperature side unit is connected in series with the evaporating side of the high-temperature side unit, and a buffer water tank is connected in series in the middle. The pipelines of the two units are connected to the inside of the buffer water tank, and the inside of the buffer water tank is in a mixed water state. The heat source of the high-temperature side unit comes from the buffer water tank. The hot water in the buffer water tank is pumped to the high-temperature side unit through the fourth circulation pump 5, and is sent back to the buffer water tank after heat absorption and cooling. The buffer water tank does not have an auxiliary heating function, and its stored heat all comes from the pre-cooling process heat exchanger 8-2 and the exhaust heat of the low-temperature side unit.

The water flow entering the buffer water tank and the cooling tower can be regulated in sections or simply switched by the corresponding regulating valves. The milk transport pipeline first passes through the terminal sterilization process heat exchanger 8-3, then passes through the precooling process heat exchanger 8-2, and finally reaches the terminal low-temperature process heat exchanger 8-1.

Temperature sensors are installed on the inlet and outlet pipes of each device. A temperature sensor for detecting the heat rejection water outlet temperature T1 is provided on the condensing side water outlet pipe of the low temperature side unit. A temperature sensor for detecting the mixed return water temperature T11 is provided on the condensing side return water pipe of the low temperature side unit. A temperature sensor for detecting the low temperature side terminal secondary outlet temperature T10 is provided at the secondary side outlet of the terminal low temperature process heat exchanger 8-1. A temperature sensor for detecting the cooling tower outlet water temperature T2 is provided on the cooling tower outlet water pipe. A temperature sensor for detecting the heat rejection return water temperature T3 is provided on the pipe from the buffer water tank to the condensing side return water pipe of the low temperature side unit. A temperature sensor for detecting the first bypass outlet water temperature T12 is provided on the first bypass branch. A temperature sensor for detecting the precooling recovery heat outlet water temperature T6 is provided on the pipe connecting the buffer water tank to the precooling circulation pump, and a temperature sensor for detecting the precooling recovery heat return water temperature T7 is provided on the pipe from the precooling process heat exchanger to the buffer water tank. A temperature sensor for detecting the precooling recovery heat return water temperature T7 is provided on the secondary side outlet of the precooling process heat exchanger 8-2. A temperature sensor for detecting the precooling side terminal secondary outlet temperature T9 is provided at the secondary side outlet of the precooling process heat exchanger 8-2. A temperature sensor for detecting the heat absorption water inlet temperature T5 is provided on the evaporation side water inlet pipe of the high temperature side unit. A temperature sensor for detecting the heat absorption water return temperature T4 is provided on the evaporation side water return pipe of the high temperature side unit. A temperature sensor for detecting the second bypass water outlet temperature T13 is provided on the second bypass branch. A temperature sensor for detecting the high temperature side terminal secondary outlet temperature T8 is provided at the secondary side outlet of the terminal disinfection process heat exchanger 8-3.

The low temperature side unit 1 produces 0~1℃ chilled water to supply the terminal low temperature process heat exchanger 8-1, and quickly cools the fluid flowing through the terminal low temperature process heat exchanger 8-1. The second circulation pump 7-1 on its pipeline is adjusted according to the outlet temperature of the secondary side fluid of the terminal low temperature process heat exchanger 8-1. The temperature setting value is related to the system process flow and can generally be 2~8℃.

The first circulating pump 2 on the condensing side of the low temperature side unit 1 is responsible for controlling the temperature difference of the inlet and outlet pipelines on the condensing side of the low temperature side unit to ensure that all the condensation heat of the low temperature side unit is discharged by its cooling water. The temperature difference control is generally 5°C.

The cooling water inlet temperature T11 of the low-temperature side unit 1 is determined by the outlet water temperature of the heat storage buffer water tank 9 (i.e., the heat rejection return water temperature T3). The heat rejection return water temperature T3 should be consistent with the design inlet water temperature of the evaporation side of the high-temperature side unit 6 (i.e., the heat absorption inlet water temperature T5), and the set value of this temperature should be slightly lower than the temperature required by the precooling process. If the precooling process has no temperature control requirements, its temperature setting value should consider the intermediate temperature that can make the high-temperature side unit 6 and the low-temperature side unit 1 operate with the highest energy efficiency. Generally, this temperature can be considered as the average of the low-temperature water supply temperature and the high-temperature water supply temperature, usually 40~60℃.

The outlet water temperature of the cooling tower 4 of the low-temperature side unit 1 (i.e., the cooling tower outlet water temperature T2) should be controlled by the variable frequency fan. The water tank outlet temperature and the cooling tower temperature should also be consistent, that is, T2 and T3 should also be consistent. If T2 and T3 are inconsistent, assuming that the cooling tower outlet water temperature is too low, then the water temperature entering the condenser of the low-temperature side unit will also decrease. If the temperature fluctuates too much, it will cause a host failure.

The fourth circulation pump 5 on the evaporation side of the high temperature side unit 6 controls the inlet and outlet temperature difference, which is generally 5°C, that is, T5-T4 is usually equal to 5°C.

The third circulation pump 7-3 on the condensing side of the high-temperature side unit 6 controls the secondary side outlet fluid temperature of its terminal disinfection process heat exchanger 8-3, and its temperature setting value is related to the process flow, which is generally 80~110℃; the evaporation side outlet temperature of the low-temperature side unit 1 and the condensing side outlet temperature of the high-temperature side unit 6 are independently controlled by their corresponding units, and their temperature setting values are determined by their corresponding process requirement temperatures.

The precooling circulation pump 7-2 controls the secondary side outlet fluid temperature of the precooling process heat exchanger 8-2. The temperature setting value is related to the process flow and can generally be 40~70℃.

The first bypass valve 3-3 and the first switching valve 3-4 control the water supply direction of the low-temperature side unit 1. When the water supply temperature of the low-temperature side unit 1 reaches the set target, the first bypass valve 3-3 is closed and the first switching valve 3-4 is opened to supply qualified water to the terminal low-temperature process heat exchanger 8-1. When the water supply target of the low-temperature side unit 1 does not meet the set target, the first bypass valve 3-3 is opened and the first switching valve 3-4 is closed to lead the unqualified water to the buffer water tank 9 to prevent the water temperature from not meeting the standard and affecting the terminal control process.

In the prior art, the liquid working medium at room temperature or low temperature is first heated to 80°C by the terminal disinfection process heat exchanger 8-3, and then quickly cooled to 0~2°C after a short storage. The present invention adds a precooling process heat exchanger 8-2 during this period to recover the higher quality heat source in the system. The recovered hot water at 40~50°C is temporarily stored in the buffer water tank through the precooling circulation pump 7-2.

After the preliminary cooling of the pre-cooling process heat exchanger 8-2, the working fluid flows into the terminal low-temperature process heat exchanger 8-1 and is quickly cooled to 0~2℃. The low-temperature cold water of the terminal low-temperature process heat exchanger 8-1 comes from the low-temperature side unit. The condensation exhaust heat of the low-temperature side unit is discharged to the buffer water tank first.

When the heat rejection of the low-temperature side unit and the recovered heat of the precooling process heat exchanger 8-2 are greater than the heat absorption of the high-temperature side unit (i.e. the temperature of the buffer water tank rises), the excess condensation heat rejection of the low-temperature side unit is discharged by the cooling tower 4.

It should be noted that the initial temperature of the liquid working fluid that needs to be pasteurized is generally higher than the temperature of the liquid after sterilization. The overall process is a cooling process, and the cooling capacity in the process is greater than the heating capacity. On the cold and hot source side of the process, there is electrical power input to drive the compressor to perform cooling and heating. Therefore, the heat absorption of the high-temperature side unit is always less than the heat discharge of the low-temperature side unit, and the system can maintain stable operation.

The chilled water outlet temperature setting value of the low-temperature side unit is set to 0.5℃, the water outlet temperature setting value of the high-temperature side unit is set to 90℃, the temperature setting value T5 of the buffer water tank _{is set to} 50℃, and the temperature fluctuation of the buffer water tank is set to ±5℃. The heating temperature setting value T8 of the liquid working medium in the disinfection process _{is set to} 80℃, and the low-temperature storage process temperature T10 after disinfection _{is set to} 2℃. The chiller and heat pump unit have self-regulation functions. The equipment automatically adjusts its own load according to its own control target to meet the operation requirements.

The first circulating pump 2 controls the inlet and outlet water temperature difference △T1 on the condensing side of the low-temperature side unit, that is, △T1 is the temperature difference corresponding to the heat rejection of the low-temperature side unit, △T1=T1-T11, △T1 _setting =T1-T3 _setting , where 3<△T1 _setting <8. When △T1<△T1 _setting , the first circulating pump 2 reduces the frequency. When △T1>△T1 _setting , the first circulating pump 2 increases the frequency;

The fourth circulating pump 5 controls the inlet and outlet water temperature difference △T2 on the heat source side (evaporation side) of the high temperature side unit, that is, △T2 is the temperature difference corresponding to the heat absorption of the high temperature side unit, △T2=T5-T4, △T2 _setting =T5-T4 _setting , where 3<△T2 _setting <8. When △T2<△T2 _setting , the fourth circulating pump 5 reduces the frequency. When △T2>△T2 _setting , the fourth circulating pump 5 increases the frequency;

The second circulating pump 7-1 controls the secondary outlet temperature T10 of the terminal heat exchange device 8-1, and the setting value of T10 is 2°C. _When T10<T10, the frequency of the second circulating pump 7-1 is reduced, and _when T10>T10, the frequency of the second circulating pump 7-1 is increased;

The precooling circulation pump 7-2 controls the inlet and outlet temperature difference of the primary side of the precooling process heat exchanger 8-2, △T3 ₌ T7 _- T6, that is, △T3 is the temperature difference corresponding to the part of the heat recovered by the precooling process heat exchanger, △T3 = T7-T6, where 3<△T3 _< 8. _When △T3<△T3, the precooling circulation pump 7-2 reduces the frequency. _When △T3>△T3, the precooling circulation pump 7-2 increases the frequency;

The third circulating pump 7-3 controls the secondary side outlet water temperature T8 of the terminal disinfection process heat exchanger 8-3 to be 80°C. _When T8< T8, the third circulating pump 7-3 increases the frequency. _When T8> T8, the third circulating pump 7-3 decreases the frequency.

The cooling tower regulating valve 3 - 1 and the first regulating valve 3 - 2 jointly control the temperature of the buffer water tank 9 to prevent the temperature of the buffer water tank 9 from exceeding the range of [45,55].

When controlling the temperature of the buffer water tank to be within a predetermined temperature range, the present invention adopts segmented control for the corresponding valve, as follows.

_T5setmax = _T5set +5, _T5setmin = _T5set -5.

When the outlet water temperature of the buffer water tank, that is, the inlet water temperature T5 of the heat absorption detection is greater than T5 _{set max} , when the opening of the cooling tower regulating valve 3-1 is judged to be less than 90%, the opening of the cooling tower regulating valve 3-1 is increased by 10%; when the opening of the cooling tower regulating valve 3-1 is judged to be greater than 90%, the opening of the first regulating valve 3-2 is closed by 10%. This specific embodiment uses 90% as the specific value of the preset larger opening, and 10% as the specific value of the opening adjustment range. It should be noted that this specific value is only used for example, and technicians in this field can set the corresponding value according to needs.

When the outlet water temperature of the buffer water tank T5< _T5setmin within a certain period of time, the first regulating valve 3-2 is opened and the cooling tower regulating valve 3-1 is closed.

When T5>the upper limit of the water tank temperature, for example, T5 _{is set to max} +2°C, the cooling tower regulating valve 3-1 is fully opened. After the cooling tower regulating valve 3-1 is fully opened, the first regulating valve 3-2 is closed.

When T5 is less than the lower limit of the water tank temperature, for example, T5 _{is set to min} -2°C, the first regulating valve 3-2 is fully opened. After the first regulating valve 3-2 is fully opened, the cooling tower regulating valve 3-1 is closed.

The above technical solution of the present invention realizes a process energy system for simultaneous cooling and heating, which can be applied to pasteurization processes and other process production processes with simultaneous cooling and heating requirements. The above technical solution adopts a two-stage refrigeration heat pump unit in series to reduce the compression ratio of the compressor of each stage unit and improve the unit operation energy efficiency. At the same time, the two-stage units are connected in the form of an intermediate buffer water tank, which can buffer and offset the operating water temperature fluctuation caused by the untimely adjustment of the load changes of the first and second stage units, thereby causing the risk of unit shutdown protection; further, the buffer water tank can directly recycle the high-grade heat source in the production process, and while cooling the production products, the heat is directly used for the high-temperature heat pump to avoid the heat being recovered by the low-temperature refrigeration unit, thereby improving the system operation energy efficiency; moreover, the cooling tower of the low-temperature side unit of the system can timely remove the excess condensation heat of the low-temperature side unit to prevent insufficient heat use on the high-temperature side during the production process, excessive refrigeration of the low-temperature side unit resulting in excessive condensation heat that cannot be matched, and the high-temperature side unit cannot effectively remove the condensation heat of the low-temperature unit, resulting in system failure.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (16)

1. The disinfection and storage process system comprises a control module, a high-temperature side unit for disinfecting products and a low-temperature side unit for refrigerating or freezing and storing the products, and is characterized by also comprising a buffer water tank arranged between the high-temperature side unit and the low-temperature side unit, wherein the buffer water tank is connected with a cooling tower of the low-temperature side unit in parallel;

The control module controls the buffer water tank to recover heat of the condensation side of the low-temperature side unit, and simultaneously provides the heat recovered by the buffer water tank to the evaporation side of the high-temperature side unit.

2. The disinfection storage process system of claim 1, wherein the buffer water tank is connected with a precooling process heat exchanger through a precooling circulating pump, the product is disinfected by the high-temperature side unit through a conveying pipeline, exchanges heat with the precooling process heat exchanger, recovers part of heat to the buffer water tank, and then is sent to the low-temperature side unit for storage.

3. The sterilization storage process system of claim 1 or 2, wherein the control module controls the amount of heat rejected from the condensing side of the low temperature side unit to be preferentially supplied to the buffer tank;

And when the heat rejection of the condensing side of the low-temperature side unit is larger than the heat rejection required by the evaporating side of the high-temperature side unit, or the sum of the heat rejection of the condensing side of the low-temperature side unit and the heat recovered by the pre-cooling process heat exchanger is larger than the heat rejection required by the evaporating side of the high-temperature side unit, controlling the cooling tower to recover redundant heat rejection of the condensing side of the low-temperature side unit.

4. A disinfection storage process system according to claim 3, wherein a first circulating pump is arranged on a condensation side water outlet pipeline of the low temperature side unit, a cooling tower regulating valve is arranged on a water inlet pipe communicated with the first circulating pump, and a first regulating valve is arranged on a first water inlet pipe communicated with the first circulating pump.

5. The disinfection storage process system of claim 4, wherein the evaporation side of the low temperature side unit exchanges heat with a terminal low temperature process heat exchanger, a second circulating pump is arranged on an outlet pipeline of the evaporation side of the low temperature side unit, and a water inlet pipe of the terminal low temperature process heat exchanger communicated with the second circulating pump is provided with a first switching valve; the water outlet side of the second circulating pump is connected with the buffer water tank through a first bypass branch and a first bypass valve.

6. A disinfection storage process system according to claim 3, wherein the condensation side of the high temperature side unit exchanges heat with a terminal disinfection process heat exchanger, a third circulating pump is arranged on a water outlet pipeline of the condensation side of the high temperature side unit, and a second switching valve is arranged on a water inlet pipe of the terminal disinfection process heat exchanger communicated with the third circulating pump;

And the water outlet side of the third circulating pump is connected with the buffer water tank through a second bypass branch and a second bypass valve.

7. The disinfection storage process system of claim 6, wherein a fourth circulation pump is provided on the evaporation side inlet line of said high temperature side unit.

8. A control method of a sterilization storage process system according to any one of claims 1 to 7, wherein the temperature of the heat absorption water input from the buffer tank is set in a temperature range based on the tank temperature set by a user by controlling the frequency of the corresponding circulation pump and controlling the opening of the corresponding valve in a sectional manner or on-off control in each control period.

9. The control method of a sterilization and storage process system according to claim 8, wherein when the temperature of the heat absorption side water outputted from the buffer tank is within a temperature range based on the tank temperature set by a user, the set value of the heat removal amount water return temperature and/or the set value of the pre-cooling recovered heat water return temperature are adjusted according to the real-time change of the heat absorption side water intake temperature outputted from the buffer tank.

10. The method of controlling a sterilization storage process system according to claim 9, wherein controlling the frequency of the corresponding circulation pump comprises:

And when the temperature difference corresponding to the heat removal amount of the low-temperature side unit is smaller than the set temperature difference of the heat removal amount, controlling the first circulating pump to reduce the frequency, otherwise controlling the first circulating pump to increase the frequency, wherein the set temperature difference of the heat removal amount is the difference of the heat removal water temperature minus the set value of the heat removal amount backwater temperature.

11. The method of controlling a sterilization storage process system according to claim 9, wherein controlling the frequency of the corresponding circulation pump comprises:

and when the temperature difference corresponding to the heat absorption quantity of the high-temperature side unit is smaller than the heat absorption quantity set temperature difference, controlling the fourth circulating pump to reduce the frequency, otherwise controlling the fourth circulating pump to increase the frequency, wherein the heat absorption quantity set temperature difference is the difference of the heat absorption quantity water inlet temperature minus the heat absorption quantity water return temperature set value.

12. The method of claim 9, wherein when the temperature difference corresponding to the part of heat recovered by the pre-cooling process heat exchanger is smaller than a preset recovery temperature difference, the pre-cooling circulation pump is controlled to perform down-conversion, otherwise, the pre-cooling circulation pump is controlled to perform up-conversion, and the preset recovery temperature difference is a difference obtained by subtracting the pre-cooling recovery heat water outlet temperature from a set value of the pre-cooling recovery heat water return temperature.

13. A method of controlling a sterilization storage process system according to any one of claims 8 to 12, wherein the step of controlling the opening of the corresponding valve in a stepwise manner comprises:

When the water outlet temperature of the buffer water tank supplied to the high-temperature side unit is greater than the water tank temperature set by a user T5 _max,=T5 _{Is provided with} +△T,T5 _{Is provided with} within a certain period of time, delta T is more than 0 and less than 15;

if the opening of the cooling tower regulating valve is smaller than the preset larger opening, controlling the opening of the cooling tower regulating valve to increase by one opening regulating amplitude; otherwise, the first regulating valve is controlled to close an opening regulating amplitude.

14. The control method of a disinfection and storage process system according to claim 13, wherein when the outlet water temperature of the buffer water tank supplied to the high temperature side unit is greater than T5 _max for a certain period of time, the setting value of the heat removal amount backwater temperature and/or the setting value of the pre-cooling recovered heat backwater temperature is set to a maximum value of a temperature range based on the water tank temperature set by a user, so that the control of the frequency of the corresponding circulation pump is dynamically adjusted.

15. The control method of a sterilization storage process system according to claim 14, wherein after setting the corresponding temperature to a maximum value of a temperature range based on a user-set water tank temperature, the heat absorption amount water inflow temperature outputted from the buffer water tank is monitored; if the rising rate of the heat absorption water inlet temperature is reduced, the set value of the precooling recovery heat backwater temperature is reduced by one gear until the set value is reduced to the water tank temperature set by a user; if the rising rate of the heat absorption water inlet temperature is unchanged or rises, delaying for a certain time, judging whether the water outlet temperature of the buffer water tank supplied to the high temperature side unit is greater than T5 _max, if so, setting the set value of the pre-cooling recovered heat backwater temperature as the water tank temperature set by a user, and if not, entering the next control period.

16. A method of controlling a sterilization storage process system according to any one of claims 8 to 12, wherein the opening and closing control of the corresponding valve comprises:

When the water outlet temperature of the buffer water tank supplied to the high-temperature side unit is smaller than the water tank temperature set by T5 _min,=T5 _{Is provided with} -△T;T5 _{Is provided with} for a user within a certain period of time, deltaT is more than 0 and less than 15;

And controlling the first regulating valve to be in an open state, closing the cooling tower regulating valve, and setting a set value of the heat removal quantity backwater temperature and/or a set value of the precooling recovered heat backwater temperature to be a minimum value of a temperature range taking the water tank temperature set by a user as a reference.