Chemical solvent heating device and heating method

Abstract

The invention discloses a chemical solvent heating device which comprises a box body, a heat exchange pipe, a plurality of low-precision heaters, a plurality of high-precision heaters, a temperature collector and a controller, the heat exchange pipe is coiled into at least four coil pipes in the box body, and the coil pipes are arranged in an array manner; a liquid inlet and a liquid outlet of the heat exchange pipe extend out of the box body; the temperature collectors are arranged in the liquid inlet and the liquid outlet and used for collecting the temperature of flowing liquid; a plurality of low-precision heaters are arranged in the hollow area of the coil pipe from the liquid inlet one by one; a plurality of high-precision heaters are arranged in the hollow area of the rest coil pipe one by one; the controller is connected with the low-precision heater, the high-precision heater and the temperature collector and used for controlling the heating states of the low-precision heater and the high-precision heater according to the collected temperature. Through cooperation of a simple structure and a reasonable heating method, the manufacturing cost of the device is effectively reduced, and the reliability of the system is optimized; and the heating effect is good, the precision is high, and temperature overshoot caused by excessive heating or late heating is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical solvent heating, and in particular to a chemical solvent heating device and a heating method. Background Art

[0002] When heating and maintaining a constant temperature for chemical solvents, especially highly corrosive chemical solvents, higher-level anti-corrosion measures and highly clean containers and pipelines are required. Commonly used heating rods cannot be placed in the pipeline to heat the organic solution, so direct heating is not possible. The organic solution in the pipeline can only be heated and maintained at a constant temperature through external heat exchange.

[0003] Existing equipment is too expensive, and heating components need to be shut down for replacement when damaged. The replacement process is complicated and the replacement cost is too high. At the same time, in order to provide more precise temperature control, existing equipment uses a large number of high-precision instruments and complex temperature control algorithms, which invisibly increases the cost of the equipment.

[0004] During the heating process, existing technologies only consider the temperature captured by the sensor. This temperature only reflects the temperature of the heated liquid. However, the specific heat capacity and heat exchange rate of metals or non-metals during the heating process can cause a delay in temperature change, resulting in a delayed heater response. Existing technologies do not consider this delayed heater response, which can lead to overheating or heating time lag during the heating process. Both overheating and heating time lag can cause the liquid temperature to fluctuate beyond the acceptable range. Temperature requirements are particularly stringent during the constant temperature heating of highly corrosive chemical solvents, generally allowing only a ±3° temperature deviation. If overheating or heating time lag occurs, it will be difficult to meet temperature requirements. Furthermore, some specialized chemical solvents are supplied using intermittent, pulsed, or variable flow methods, resulting in large heating temperature differences and high heating response speed requirements. Existing heating methods, which mostly use a single-stage heating method, cannot simply achieve both heating speed and accuracy requirements. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a chemical solvent heating device and heating method to solve the technical problems in the prior art such as high equipment cost, complex heating control process, and easy occurrence of overheating and late heating.

[0006] The present invention provides a chemical solvent heating device, comprising: a box, a heat exchange tube, several low-precision heaters, several high-precision heaters, a temperature collector and a controller;

[0007] The heat exchange tubes are wound into at least four coils in the box, and the coils are arranged in an array; the liquid inlet and outlet of the heat exchange tubes both extend out of the box; a temperature collector is set in the liquid inlet and outlet to collect the temperature of the liquid flowing through; several low-precision heaters are placed one by one in the hollow area of ​​the coil starting from the liquid inlet; several high-precision heaters are placed one by one in the hollow area of ​​the remaining coils; a controller is connected to the low-precision heater, the high-precision heater and the temperature collector respectively, and is used to control the heating status of the low-precision heater and the high-precision heater according to the temperature collected by the temperature collector.

[0008] Furthermore, the low-precision heater is a low-precision electric heating tube heater or a low-precision electric heating wire heater.

[0009] Furthermore, the high-precision heater is a PTC heater.

[0010] The present invention also provides a heating method of a chemical solvent heating device, comprising:

[0011] Set the target temperature and the first-stage heating target temperature, and obtain the liquid flow rate and liquid flow duty cycle according to the working state, wherein the working state includes: online working state and offline working state; when in the online working state, the liquid flow rate and liquid flow duty cycle are set by setting mode; when in the offline working state, the liquid flow rate and liquid flow duty cycle are obtained by local calculation mode;

[0012] When the liquid is flowing, a first heating duty cycle is obtained, and a first-stage closed-loop heating is performed according to the first heating duty cycle, and the liquid temperature is heated to a first-stage heating target temperature through the first-stage closed-loop heating method;

[0013] Heating the liquid to the target temperature through a second-stage closed-loop heating method;

[0014] When the liquid flow is stopped, the liquid temperature is maintained by the second stage closed loop heating method.

[0015] Among them, the second-level closed-loop heating method also includes: obtaining the advance heating time and the advance stop heating time, stopping heating according to the advance stop heating time during the liquid heating process; and starting heating according to the advance heating time or preset temperature during the liquid cooling process.

[0016] Furthermore, the calculation formula of the liquid flow rate is:

[0017]

[0018] Where, P 加 is the heating power; K is the conversion efficiency; P is the loss power; T k is the heating slope during the second stage closed-loop heating; C is the specific heat capacity.

[0019] Furthermore, the method for obtaining the liquid flow duty ratio is:

[0020] The liquid flow duty cycle is obtained based on the interval time when the liquid inlet temperature drops and rises significantly.

[0021] Furthermore, the calculation formula of the first heating duty cycle is:

[0022]

[0023] Where F is the liquid flow rate; K1 = V / 100, where 100 is the temperature, i.e. 100°C; K2 = V / 1000, where 1000 is the flow rate, i.e. 1000 ml / min; V is the maximum output voltage of the temperature sensor; T x is the current liquid outlet temperature; T o is the target temperature; C x is the specific heat capacity of the liquid to be heated; C h is the specific heat capacity of water.

[0024] Furthermore, the calculation formula for the advanced stop heating time is:

[0025]

[0026] Where, K1 = V / 100, where 100 is the temperature, i.e. 100°C; K2 = V / 1000, where 1000 is the flow rate, i.e. 1000 ml / min; F is the liquid flow rate; V is the maximum output voltage of the temperature sensor; T x is the current liquid outlet temperature; T o is the target temperature; C x is the specific heat capacity of the liquid to be heated; C h is the specific heat capacity of water.

[0027] Furthermore, the method for obtaining the advanced heating time is:

[0028]

[0029] Where C is the specific heat capacity; M is the mass of liquid passing through the heating tube within a period of time after the system is started; ΔT is the temperature change; and P is the heater power.

[0030] Furthermore, the second-stage closed-loop heating method further includes: performing step-by-step heating to gradually approach the target temperature.

[0031] Beneficial effects of the present invention:

[0032] The present invention combines a simple structure with a reasonable heating method, which, firstly, effectively reduces the manufacturing cost of the device and optimizes the reliability of the system; secondly, although the device is simplified, combined with the method of the present invention, the heating effect and accuracy are significantly higher than those of existing devices, and can effectively avoid temperature overshoot caused by excessive heating or late heating.

[0033] The present invention adopts a two-stage heating method and sets two types of heaters to perform rough and precise two-stage heating, which can achieve precise control of the heating temperature. At the same time, the redundant design of the heater can continue to maintain the heating function when some heaters are damaged. The present invention optimizes the heating time. At the beginning of each heating cycle, preheating is performed in advance to ensure that the liquid can quickly reach the first target temperature; in the secondary heating process, heating is stopped in advance during the heating process and heated in advance during the cooling process, which can effectively compensate for the response delay of the heating device and avoid overheating and late heating. The present invention can reasonably calculate the liquid flow rate through the heating slope, instead of designing a high-cost and high-demand flow meter in the device, reducing the complexity of the device and reducing the cost of the device. The present invention adopts a two-stage, multi-stage heating method, which can adapt to the heating needs of special chemical solvents and can meet the requirements of heating speed and accuracy at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0035] Figure 1 Schematic diagram of a coil of heat exchange tubes in a specific embodiment of the present invention;

[0036] Figure 2 is a second schematic diagram of a coil of heat exchange tubes in a specific embodiment of the present invention;

[0037] Figure 3 is a three-dimensional schematic diagram of a chemical solvent heating device in a specific embodiment of the present invention;

[0038] Figure 4 is a graph showing the relationship between the first heating duty cycle and the flow rate at a fixed temperature in a specific embodiment of the present invention;

[0039] Figure 5 is a graph showing the relationship between the first heating duty cycle and the temperature at a fixed flow rate in a specific embodiment of the present invention;

[0040] Figure 6 1 is a graph showing the relationship between the advance stop heating time and the flow rate at a fixed temperature in a specific embodiment of the present invention;

[0041] Figure 73 is a graph showing the relationship between the advance stop heating time and the temperature at a fixed flow rate in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0042] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] The present invention will be further described below with reference to specific examples. Those skilled in the art will appreciate that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention, and that modifications to various equivalent forms of the present invention fall within the scope defined by the appended claims.

[0044] like Figure 1-4 As shown, the present invention provides a chemical solvent heating device, comprising: a box, a heat exchange tube, several low-precision heaters, several high-precision heaters, a temperature collector, and a controller;

[0045] The box body is heat-insulating and has liquid inlet and outlet holes for the extension of liquid inlet and outlet pipes; the heat exchange tube is coiled into four coils in the box body, and the coils are arranged in an array; the liquid inlet and liquid outlet of the heat exchange tube extend out of the box body from the liquid inlet and outlet holes; the temperature collector is arranged in the liquid inlet and liquid outlet to collect the temperature of the liquid flowing through; several low-precision heaters are placed one by one in the hollow area of ​​the coil starting from the liquid inlet to constitute the first-level heating; several high-precision heaters are placed one by one in the hollow area of ​​the remaining coils to constitute the second-level heating; placing the heater in the center of the coil can increase the heat exchange area. At the same time, the gap between the heater and the coil is matched to reduce the heat exchange distance, thereby realizing a high-efficiency heat exchange structure with maximized heat exchange area, minimized heat exchange distance and minimized surface heat dissipation area; the controller is connected to the low-precision heater, high-precision heater and temperature collector respectively, and is used to control the heating status of the low-precision heater and the high-precision heater according to the temperature collected by the temperature collector.

[0046] The flow rate is 900 ml / min with an interval of 1 min. A 1 / 4 diameter stainless steel tube with a wall thickness of 0.89 mm is used. Each coil has 14 turns, a total height of 150 mm, and a tube spacing of 4.3 mm.

[0047] Comparative Example 1: Double coil;

[0048] The amount of insulation liquid stored in the tube is:

[0049] V1(13,13)=8.843×10 -5

[0050] The number of seconds required for the liquid to provide normal flow is:

[0051]

[0052] The heat exchange area is:

[0053] S1(13,13)=0.108

[0054] Example 1: Four coils;

[0055] The amount of insulation liquid stored in the tube is:

[0056] V2(15,4)=8.039×10 -5

[0057] The number of seconds required for the liquid to provide normal flow is:

[0058]

[0059] The heat exchange area is:

[0060] S1(15,4)=0.098

[0061] The low-precision heater is preferably a low-precision electric heating tube heater or a low-precision electric heating wire heater.

[0062] The high-precision heater is preferably a PTC ceramic heater; a high-precision electric heating tube heater or a high-precision electric heating wire heater may also be preferred.

[0063] The present invention also provides a heating method of a chemical solvent heating device, comprising:

[0064] Set the target temperature and the first-stage heating target temperature. The first-stage heating target temperature is generally set to 10% lower than the target temperature. Obtain the liquid flow rate and liquid flow duty cycle according to the working status, where the working status includes: online working status and offline working status. When in the online working status, the liquid flow rate and liquid flow duty cycle are set manually by the host computer; when in the offline working status, the liquid flow rate and liquid flow duty cycle are obtained through local calculation. The local calculation process is to calculate the liquid flow rate and liquid flow duty cycle based on the relevant data collected during several liquid flow cycles.

[0065] The formula for calculating liquid flow rate is:

[0066]

[0067] Where, P 加is the heater power; K is the conversion efficiency; P is the loss power; T k is the heating slope during the first stage closed-loop heating; C is the specific heat capacity;

[0068] Since there are intervals between liquid flow, these intervals are reflected by the liquid flow duty cycle, which is generally 50%. When liquid flow is in progress, the liquid inlet is open, the liquid in the pipeline is heated, and the temperature of the liquid inlet rises rapidly. Because high-power heating is used, the temperature rise slope is very large. When liquid flow is stopped, the liquid inlet is closed, and the liquid inlet temperature quickly returns to the initial temperature of the liquid, then drops rapidly with a very large temperature drop slope. Therefore, the liquid flow duty cycle can be obtained by the interval between two adjacent large rising slopes and large falling slopes. At this time, the starting point of the large rising rate can also be used as the starting point of the heating time.

[0069] When the liquid is flowing, the first heating duty cycle is obtained, and the first-level closed-loop heating is performed according to the first heating duty cycle. The liquid temperature is heated to the first-level heating target temperature through the first-level closed-loop heating method. The first-level closed-loop heating method is an extensive, high-power heating process. The purpose is to quickly raise the liquid temperature to a certain height to provide a basic temperature for subsequent precise temperature adjustment.

[0070] Since it takes a process for the heater to heat up, there will be a delay in the heating process. If the heater heating is controlled at the initial starting point each time, delayed heating will occur, resulting in untimely heating. The temperature of the liquid just flowing in is relatively low, which can easily quickly lower the temperature maintained in the pipeline during the period of stopping liquid flow, causing temperature fluctuations to exceed the limit range.

[0071] The present invention adopts an advance preheating method, first calculates the time required for advance heating, and preheats the heater in advance based on the initial time starting point, which can effectively avoid delayed heating.

[0072] like Figure 4 、 5 As shown, the first heating duty cycle is related to the flow rate when the temperature is fixed, and is related to the temperature when the flow rate is fixed.

[0073] The calculation formula for the first heating duty cycle is:

[0074]

[0075] Where F is the liquid flow rate; K1 = V / 100, where 100 is the temperature, i.e. 100°C; K2 = V / 1000, where 1000 is the flow rate, i.e. 1000 ml / min; V is the maximum output voltage of the temperature sensor; T x is the current liquid outlet temperature; T o is the target temperature; Cx is the specific heat capacity of the liquid to be heated; C h is the specific heat capacity of water.

[0076] When the liquid temperature reaches the first-stage heating target temperature, the liquid temperature is heated to the target temperature through the second-stage closed-loop heating method;

[0077] When the liquid flow is stopped, the temperature in the current pipeline needs to be maintained. The liquid temperature is maintained by the second-stage closed-loop heating method.

[0078] Among them, the second-level closed-loop heating method is a process of precisely adjusting the temperature. During the process, the start and stop of heating are controlled according to the rising and falling slopes of the liquid outlet temperature. The specific process includes: obtaining the advance heating time and the advance stop heating time, stopping heating according to the advance stop heating time during the liquid heating process; and starting heating according to the advance heating time or preset temperature during the liquid cooling process.

[0079] like Figure 6 、 7 As shown, the advance stop heating time is related to the flow rate when the temperature is fixed, and is related to the temperature when the flow rate is fixed.

[0080] The calculation formula for the advance stop heating time is:

[0081]

[0082] Where, K1 = V / 100, where 100 is the temperature, i.e. 100°C; K2 = V / 1000, where 1000 is the flow rate, i.e. 1000 ml / min; F is the liquid flow rate; V is the maximum output voltage of the temperature sensor; T x is the current liquid outlet temperature; T o is the target temperature; C x is the specific heat capacity of the liquid to be heated; C h is the specific heat capacity of water.

[0083] The rising slope of the outlet temperature can be used to deduce how many seconds it takes to heat from the current temperature to the target temperature. Since the heater has heating inertia, when the target temperature is reached, the temperature will continue to rise due to the heating inertia of the heater. If the calculated heating time is used directly, the temperature may exceed the limit range. Therefore, the calculated heating time is subtracted from the advance stop heating time to obtain the accurate heating time required. Then, the temperature is gradually brought to the target temperature through the heating inertia of the heater to compensate for the negative impact of the heating inertia of the heater.

[0084] The method for obtaining the advance heating time is:

[0085]

[0086] Where C is the specific heat capacity; M is the mass of liquid passing through the heating pipe within a period of time after the system is started. The time is the approximate time required for the system heat exchange, in seconds, which is 6-8 seconds in this embodiment; ΔT is the temperature change; P 加 is the heater power.

[0087] Similar to the first-stage heating, the heater has a response delay. Regardless of whether the liquid is flowing or not, the heater switches between heating and stopping heating. When the heating stops, the liquid temperature will drop. According to the heat dissipation of the system, the time required to cool down to a certain temperature can be deduced. At this time, the timing starts when the temperature drops, and the heating can be turned on when the calculated time is reached. Early heating can be carried out to avoid the response delay of the heater causing the liquid temperature to be lower than the limit temperature range.

[0088] Since the heating process is to transfer the heat of the heater to the aluminum tube wall through water and then to the internal liquid to be heated, the aluminum tube wall will store a certain amount of thermal energy during the heat exchange process. This part of the thermal energy needs to be reasonably utilized. Preheating is to store the thermal energy in the aluminum tube wall first and then transfer it to the liquid. Similarly, early shutdown is to use up the thermal energy on the aluminum tube wall to prevent temperature overshoot.

[0089] In order to improve the accuracy of the second-stage closed-loop heating method, the first-stage heating target temperature to the target temperature can be divided into multiple stages, and step-by-step heating can be performed to gradually approach the target temperature. For example: the target temperature is 90°, the first-stage heating target temperature is 70°, and starting from 70°, it is divided into four stages: 70°~75°; 75°~80°; 80°~85°; 85°~90°. Each stage adopts the above-mentioned second-stage closed-loop heating method to improve the accuracy of the heating process.

[0090] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A chemical solvent heating device, characterized in that: include: Box, heat exchange tubes, several low-precision heaters, several high-precision heaters, temperature collector and controller; The heat exchange tubes are wound into at least four coils in the box, and the coils are arranged in an array; the liquid inlet and outlet of the heat exchange tubes both extend out of the box; a temperature collector is set in the liquid inlet and outlet to collect the temperature of the liquid flowing through; several low-precision heaters are placed one by one in the hollow area of ​​the coil starting from the liquid inlet; several high-precision heaters are placed one by one in the hollow area of ​​the remaining coils; a controller is connected to the low-precision heater, the high-precision heater and the temperature collector respectively, and is used to control the heating status of the low-precision heater and the high-precision heater according to the temperature collected by the temperature collector.

2. The chemical solvent heating device according to claim 1, characterized in that: The low-precision heater is a low-precision electric heating tube heater or a low-precision electric heating wire heater.

3. The chemical solvent heating device according to claim 1 or 2, characterized in that: The high-precision heater is a PTC heater.

4. A heating method for a chemical solvent heating device according to any one of claims 1 to 3, characterized in that: include: Set the target temperature and the first-stage heating target temperature, and obtain the liquid flow rate and liquid flow duty cycle according to the working state, wherein the working state includes: online working state and offline working state; when in the online working state, the liquid flow rate and liquid flow duty cycle are set by setting mode; when in the offline working state, the liquid flow rate and liquid flow duty cycle are obtained by local calculation mode; When the liquid is flowing, a first heating duty cycle is obtained, and a first-stage closed-loop heating is performed according to the first heating duty cycle, and the liquid temperature is heated to a first-stage heating target temperature through the first-stage closed-loop heating method; Heating the liquid to the target temperature through a second-stage closed-loop heating method; When the liquid flow is stopped, the liquid temperature is maintained by the second stage closed loop heating method. Among them, the second-level closed-loop heating method also includes: obtaining the advance heating time and the advance stop heating time, stopping heating according to the advance stop heating time during the liquid heating process; and starting heating according to the advance heating time or preset temperature during the liquid cooling process.

5. The heating method of the chemical solvent heating device according to claim 4, characterized in that: The calculation formula of the liquid flow rate is: Where, P 加 is the heating power; K is the conversion efficiency; P is the loss power; T k is the heating slope during the second stage closed-loop heating; C is the specific heat capacity.

6. The heating method of the chemical solvent heating device according to claim 4, characterized in that: The method for obtaining the liquid flow duty ratio is: The liquid flow duty cycle is obtained based on the interval time when the liquid inlet temperature drops and rises significantly.

7. The heating method of the chemical solvent heating device according to claim 4, characterized in that: The calculation formula of the first heating duty cycle is: Where F is the liquid flow rate; K1 = V / 100, where 100 is the temperature, i.e. 100°C; K2 = V / 1000, where 1000 is the flow rate, i.e. 1000 ml / min; V is the maximum output voltage of the temperature sensor; T x is the current liquid outlet temperature; T o is the target temperature; C x is the specific heat capacity of the liquid to be heated; C h is the specific heat capacity of water.

8. The heating method of the chemical solvent heating device according to claim 4, characterized in that: The calculation formula for the advanced stop heating time is: Where, K1 = V / 100, where 100 is the temperature, i.e. 100°C; K2 = V / 1000, where 1000 is the flow rate, i.e. 1000 ml / min; F is the liquid flow rate; V is the maximum output voltage of the temperature sensor; T x is the current liquid outlet temperature; T o is the target temperature; C x is the specific heat capacity of the liquid to be heated; C h is the specific heat capacity of water.

9. The heating method of the chemical solvent heating device according to claim 4, characterized in that: The method for obtaining the advanced heating time is: Where C is the specific heat capacity; M is the mass of liquid passing through the heating tube within a period of time after the system is started; ΔT is the temperature change; and P is the heater power.

10. The heating method of the chemical solvent heating device according to any one of claims 4 to 9, characterized in that: The second-stage closed-loop heating method further includes: performing step-by-step heating to gradually approach the target temperature.

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