Series-parallel connection mixed supercritical drying system and process

Abstract

According to the series-parallel connection mixed supercritical drying system and technology, the novel supercritical drying system is constructed, drying kettles can be called according to the specific amount of dried materials, and therefore the drying kettles can be independently used for drying and can also be used in a series-parallel connection mixed mode; the drying system can be used for drying different products under different conditions according to actual process requirements, and the operation flexibility is greatly improved. Based on the connection characteristic of series-parallel mixing, the operation period of the pressure boosting link and the pressure reducing link of the drying kettle is effectively shortened, and therefore the operation period of the whole system is prolonged by 40%. Due to the fact that the drying kettles can be switched or isolated, supercritical fluid in the kettles can be directly and mutually poured, most fluid does not need to pass through a pressure relief, recovery and circulation device, the supercritical fluid in the system is mainly used for drying circulation, and therefore the situation of resource waste can be effectively restrained.

Description

Technical Field

[0001] The present invention relates to the technical field of supercritical fluid drying, and in particular to a series-parallel mixed supercritical drying system and process. Background Art

[0002] Supercritical fluid drying technology is widely used in industries such as traditional Chinese medicine and spice extraction, aerogels, and precision instrument cleaning. Currently, in the industrial sector, supercritical fluid drying generally utilizes a small number of drying vessels. Each drying vessel is equipped with a separate circulation system, or several drying vessels are equipped with a single supercritical fluid circulation system, and the multiple drying vessels are essentially independent of each other. In actual industrial production, supercritical fluid drying technology involves a large number of equipment and consumes large amounts of supercritical fluid, which is also accompanied by significant energy consumption. During normal operation, the drying vessels and the corresponding supercritical fluid circulation system are operated and shut down simultaneously, making it impossible to switch or isolate one or more drying vessels independently. This makes the entire drying process labor-intensive and inflexible, and the system's operating cycle long. During operation, the drying vessels corresponding to the supercritical fluid circulation system must simultaneously perform feeding, supercritical drying, and pressure relief operations. If a drying vessel is not fed, the equipment will run idle, resulting in associated energy and material waste. Summary of the Invention

[0003] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a supercritical drying system and process with a series-parallel hybrid system, in which drying kettles can be timely adjusted according to the specific amount of material to be dried. That is, the drying kettles can be used for drying alone or in a series-parallel hybrid system, so that the equipment can dry different products under different conditions according to actual process requirements, greatly increasing the operational flexibility, thereby solving the problems in the prior art of supercritical fluid drying systems in which the number of drying kettles is difficult to flexibly adjust, resulting in a large workload for the drying process, a single type of dried product, a long operating cycle, and easy idling of the equipment, resulting in energy and material waste.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: A series-parallel hybrid supercritical drying system, the drying system includes multiple drying kettles, a feed port, a pressure relief port and a pressure relief port are provided on the top of the drying kettle, and a discharge port is provided at the bottom of the drying kettle; the feed port is fluidly connected to one end of the feed pipe through the feed pipe, and the other end of the feed main pipe is fluidly connected to the supercritical circulation recovery system; the pressure relief port is fluidly connected to one end of the pressure relief main pipe through the pressure relief pipe, and the other end of the pressure relief main pipe is fluidly connected to the graded pressure relief main pipe; the discharge port is fluidly connected to one end of the discharge main pipe through the discharge pipe, and the discharge The other end of the material main pipe is fluidically connected to the supercritical circulation recovery system; the equalizing port is fluidically connected to the equalizing main pipe through a equalizing pipe; the pressure relief main pipe is fluidically connected to one end of a plurality of pressure relief branch pipes, and the other end of the pressure relief branch pipe is fluidically connected to the supercritical circulation recovery system; the supercritical circulation recovery system is used to recover the supercritical fluid after the drying process in the drying kettle, and to recycle it, and then pressurize the supercritical fluid obtained after the recycling process, and then enter each drying kettle through the feed main pipe, the feed pipe and the feed port.

[0005] Preferably, a feed valve is provided on the feed pipe to control the switching of the medium in the feed pipe; a pressure relief valve is provided on the pressure relief pipe to control the switching of the medium in the pressure relief pipe; a pressure equalizing valve is provided on the pressure equalizing pipe to control the switching of the medium in the pressure equalizing pipe; a discharge valve is provided on the discharge pipe to control the switching of the medium in the discharge pipe; a pressure relief main pipe valve is provided at one end of the graded pressure relief main pipe close to the pressure relief main pipe to control the switching of the medium in the pressure relief main pipe; a pressure relief branch pipe valve is provided on each pressure relief branch pipe to control the switching of the medium in the pressure relief branch pipe.

[0006] Preferably, the number of the pressure relief branches is consistent with the pressure relief level; and the pressure relief level is set according to the maximum operating pressure of the recovery device in the supercritical circulation recovery system, the drying pressure of the drying kettle and the phase change pressure of the supercritical fluid used.

[0007] Preferably, the feed ports of every two adjacent drying kettles are fluidly connected through a feed main pipe; the pressure relief ports of every two adjacent drying kettles are fluidly connected through a pressure relief main pipe; and the pressure equalization ports of every two adjacent drying kettles are fluidly connected through a pressure equalization main pipe.

[0008] The present invention also provides a series-parallel hybrid supercritical drying process, which uses the above-mentioned supercritical drying system to perform supercritical drying, and the specific steps are as follows: Step 1: Determine the number of drying kettles involved in supercritical drying treatment based on production needs; Step 2: Start the supercritical circulation recovery system and make the system pressure output reach the pressure required by the drying process. At the same time, the product to be dried is loaded into the drying kettle and the lid of the drying kettle is closed; Step 3: Open the feed valve of the drying kettle and control the opening and the flow rate of the supercritical fluid to make the pressure and flow rate inside the drying kettle reach the required drying process, and then control the opening of the discharge valve to make the drying kettle perform cyclic drying under stable pressure and flow rate; Step 4: After the drying kettle has completed drying, open the pressure relief branch valves on multiple pressure relief branches in sequence to gradually reduce the pressure of the drying kettle to meet the conditions for opening the cover, open the drying kettle, and take out the dried product.

[0009] Preferably, in step 4, when the number of drying kettles involved in the supercritical drying process is greater than or equal to 2, a pressure leveling operation is performed before pressure relief, as follows: S1: For the drying kettle that has completed the drying process, close its feed valve and discharge valve; for the drying kettle that has not yet been dried, keep its feed valve and discharge valve in the initial state, that is, all valves are closed; S2: First, open the pressure-equalizing valves of multiple drying kettles that need drying treatment, and then open the pressure-equalizing valves of the drying kettles that have completed the drying treatment to a certain opening, so that the pressure in the drying kettles that need to participate in the drying process rises to equilibrium. After the pressure equalization is completed, close the pressure-equalizing valves of all drying kettles.

[0010] Preferably, when the drying kettle that has completed the drying treatment is subjected to the drying treatment again, it is first subjected to the S1-S2 flat pressure operation, and then the supercritical circulation recovery system is used to increase the pressure and feed the material, thereby carrying out the subsequent drying treatment process.

[0011] Preferably, for a drying kettle that has completed drying, if the supercritical fluid in the drying kettle has not yet reached the maximum solubility, the supercritical fluid in the kettle is directly introduced into the drying kettle that is about to perform drying through the equalization and pressure main pipe for drying.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adds a pressure-equalizing pipe between multiple drying kettles. This design breaks through the traditional supercritical fluid drying process, which requires the drying kettles to perform multiple pressure-increasing and pressure-relieving operations. Through the pressure-equalizing pipe, the drying kettles can quickly and flexibly achieve mutual pressure equalization. This not only significantly shortens the time for pressure increase and pressure relief, but also allows the drying kettles to operate independently of the main system, greatly improving operational flexibility and independence. This design enables the drying kettles to be quickly switched and operated independently according to actual needs, thereby simultaneously processing products of different specifications and drying time requirements without affecting the overall system.

[0013] 2. The present invention also introduces a graded pressure relief mechanism, which enables the pressure of the drying kettle to be gradually reduced in stages, avoiding the problems of sudden pressure drop and material loss caused by the traditional direct pressure relief method; by subdividing the pressure relief process into multiple pressure levels, it not only effectively controls the pressure relief rate, but also significantly reduces the waste of materials and energy, and improves the overall utilization rate of the system; this graded pressure relief method not only increases the pressure increase and decrease rate by about 40%, but also enables the drying kettle to quickly reach the target pressure in a short time, greatly shortening the drying cycle.

[0014] 3. In the present invention, the mutual material pouring function between drying kettles further optimizes the drying process, avoiding the tedious steps of complete pressure relief, recovery and circulation processes required in traditional processes; this design not only reduces unnecessary material and energy waste, but also enables the drying kettle to proceed directly to the next operation after reaching the maximum solubility, thereby improving the overall efficiency and economy of the system, and opening up a new direction for the development of supercritical drying technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of the series-parallel hybrid supercritical drying system of the present invention.

[0016] In the figure: drying kettle 1, feed pipe 2, feed main pipe 3, supercritical circulation recovery system 4, pressure relief pipe 5, pressure relief main pipe 6, graded pressure relief main pipe 7, discharge pipe 8, discharge main pipe 9, equalizing pressure pipe 10, equalizing pressure main pipe 11, pressure relief branch pipe 12, feed valve 13, pressure relief valve 14, equalizing pressure valve 15, discharge valve 16, pressure relief main pipe valve 17, pressure relief branch pipe valve 18. DETAILED DESCRIPTION

[0017] The present invention will be described clearly and completely with reference to the accompanying drawings of 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. All other embodiments derived by persons of ordinary skill in the art based on the present invention are within the scope of protection of the present invention.

[0018] Unless otherwise indicated in specific cases, the numerical ranges listed herein include the upper and lower limits, and all integers and fractions within the range, and are not limited to the specific values ​​listed when defining the range.

[0019] 1. A series-parallel hybrid supercritical drying system The drying system of the present invention is as follows Figure 1As shown, it includes multiple drying kettles 1, a feed port, a pressure relief port and a pressure relief port are provided on the top of the drying kettle, and a discharge port is provided at the bottom of the drying kettle; the feed port is fluidly connected to one end of the feed main pipe 3 through a feed pipe 2, and the other end of the feed main pipe 3 is fluidly connected to the supercritical circulation recovery system 4; the pressure relief port is fluidly connected to one end of the pressure relief main pipe 6 through a pressure relief pipe 5, and the other end of the pressure relief main pipe 6 is fluidly connected to the graded pressure relief main pipe 7, and the number of pressure relief pipes corresponds to the number of drying kettles; the discharge port is fluidly connected to one end of the discharge main pipe 9 through a discharge pipe 8, and the discharge The other end of the main pipe 9 is fluidically connected to the supercritical circulation recovery system 4; the equalizing port is fluidically connected to the equalizing main pipe 11 through the equalizing pipe 10; the graded pressure relief main pipe 7 is fluidically connected to one end of a plurality of pressure relief branch pipes 8, and the other end of the pressure relief branch pipe 8 is fluidically connected to the supercritical circulation recovery system 4; the supercritical circulation recovery system 4 is used to recover the supercritical fluid after the drying treatment in the drying kettle, and recycle it, and then pressurize the supercritical fluid obtained after the recovery treatment, and then transport it through the feed main pipe 3 through the feed pipe 2 and the feed port into the drying kettle 1.

[0020] In some embodiments of the present invention, a feed valve 13 is provided on the feed pipe 2 for controlling the switching of the medium in the feed pipe; a pressure relief valve 14 is provided on the pressure relief pipe 5 for controlling the switching of the medium in the pressure relief pipe; a pressure equalizing valve 15 is provided on the equalizing pressure pipe 10 for controlling the switching of the medium in the pressure equalizing pipe; a discharge valve 16 is provided on the discharge pipe 8 for controlling the switching of the medium in the discharge pipe; a pressure relief main pipe valve 17 is provided at one end of the pressure relief main pipe 6 close to the graded pressure relief main pipe 7 for controlling the switching of the medium in the pressure relief main pipe 6; a pressure relief branch pipe valve 18 is provided on the pressure relief branch pipe 12 for controlling the switching of the medium in the pressure relief branch pipe 12.

[0021] In some embodiments of the present invention, the number of the pressure relief branches is consistent with the pressure relief level, and the pressure relief level is flexibly set according to the maximum operating pressure of the recovery device in the supercritical circulation recovery system, the drying pressure conditions of the drying kettle, and the phase change pressure of the supercritical fluid used. For example, (1) the maximum operating pressures of the recovery devices in the supercritical circulation recovery system are 12 MPaG, 6 MPaG, and 2 MPaG respectively, the drying conditions of the drying kettle are 10 MPaG, and the phase change pressure of the supercritical fluid used is 3 MPaG, then the pressure relief levels are divided into four levels: 10~6 MPaG, 6~3 MPaG, 3~2 MPaG, and 2~0 MPaG; (2) the maximum operating pressures of the recovery devices in the supercritical circulation recovery system are 14 MPaG, 7 MPaG, 4 MPaG, and 1.8 MPaG respectively, the drying conditions of the drying kettle are 9.5 MPaG, and the phase change pressure of the supercritical fluid used is 6 MPaG, then the pressure relief levels are divided into five levels: 9.5~7 MPaG, 7~6 MPaG, 6~4 MPaG, 4~1.8 MPaG, and 1.8~0 MPaG.

[0022] In some embodiments of the present invention, the feed ports of all drying kettles are connected through the feed main fluid pipe; the pressure relief ports of all drying kettles are connected through the pressure relief main fluid pipe; the pressure equalization ports of all drying kettles are connected through the pressure equalization main fluid pipe; and the discharge ports of all drying kettles are connected through the discharge main fluid pipe.

[0023] In some embodiments of the present invention, the supercritical circulation recovery system is a very mature process system in the prior art. It is a complete process flow that can recover and circulate supercritical fluids, and can perform graded recovery and circulation of supercritical fluids of different phases and pressures. It can help the drying kettle to achieve rapid pressure relief while also realizing accurate recovery of supercritical fluids, and can also effectively separate impurities extracted by supercritical fluids.

[0024] 2. A series-parallel hybrid supercritical drying process The above-mentioned supercritical drying system is used for supercritical drying, and the specific steps are as follows: Step 1: According to production needs, determine the number of drying kettles involved in the supercritical drying process. The drying kettles can be flexibly arranged according to the number of products. If the product with high drying pressure is processed first and then the product with low drying pressure is processed, then the product with high drying pressure will be depressurized to the drying pressure value required by the product with low drying pressure after drying, and then the remaining pressure will be depressurized to the supercritical circulation recovery system. If the product with low drying pressure is processed first and then the product with high drying pressure is processed, then the product with low drying pressure will be equalized with the drying kettle that processes the product with high drying pressure after drying, and then the remaining pressure will be depressurized to the supercritical circulation recovery system. At the same time, the drying kettle that processes the product with high drying pressure will continue to increase the pressure from the supercritical circulation recovery system to the pressure required for drying. For example: (1) 8 identical products need to be dried, and 8 drying kettles are used at the same time; (2) 8 identical products need to be dried, and 9 drying kettles are used at the same time, 8 of which are used for differential drying (each drying kettle starts drying at a fixed interval), and 1 is used as an empty kettle for standby. When a drying kettle is finished drying, it is first pressure-equalized to the empty drying kettle through the equalizing main pipe, and then the pressure is released to the supercritical circulation recovery system, so as to save the pressure release time of the drying kettle; (3) It is necessary to dry 4 products A and 4 products B, and the drying time of products A and B is different. 8 drying kettles can be dried at the same time; (4) It is necessary to dry 4 products A and 4 products B, and the drying time of products A and B is different. 8 drying kettles can be divided into two groups for batch drying. If the drying pressure of product A is greater than that of product B, the pressure of group A drying kettle is directly released to the required pressure of group B drying kettle after drying, and the remaining pressure of group A drying kettle is released to the supercritical circulation recovery system. If the drying pressure of product A is less than that of product B, the pressure of group A drying kettle is first equalized with that of group B drying kettle through the equalizing main pipe after drying, and the remaining pressure is released to the supercritical circulation recovery system. At the same time, group B drying kettle continues to increase the pressure from the supercritical circulation recovery system; Step 2: Start the supercritical circulation recovery system and make the system pressure output reach the pressure required by the drying process. At the same time, the product to be dried is loaded into the drying kettle and the lid of the drying kettle is closed; Step 3: Open the feed valve of the drying kettle and control the opening or flow rate so that the pressure and stable flow rate required for the drying process are reached inside the drying kettle. Control the opening of the discharge valve so that the drying kettle can circulate and dry at a stable pressure and flow rate. Step 4: After the drying kettle has completed drying, open the pressure relief branch valves on multiple pressure relief branches in sequence to gradually reduce the pressure of the drying kettle to meet the conditions for opening the cover, open the drying kettle, and take out the dried product.

[0025] In some embodiments of the present invention, in step 4, when the number of drying kettles involved in the supercritical drying process is greater than or equal to 2, a pressure leveling operation is performed before pressure relief, as follows: S1: For the drying kettle that has completed the drying process, close its feed valve and discharge valve; for the drying kettle that has not yet been dried, keep its feed valve and discharge valve in the initial state, that is, all valves are closed; S2: First, open the pressure-equalizing valves of multiple drying kettles that need drying treatment, and then open the pressure-equalizing valves of the drying kettles that have completed the drying treatment to a certain opening, so that the pressure in the drying kettles that need to participate in the drying process rises to equilibrium. After the pressure equalization is completed, close the pressure-equalizing valves of all drying kettles.

[0026] In some embodiments of the present invention, when a drying kettle that has completed drying treatment is subjected to drying treatment again, it is first subjected to the S1-S2 flat pressure operation, and then the supercritical circulation recovery system is used to increase the pressure and feed the material, thereby performing the subsequent drying treatment process.

[0027] In some embodiments of the present invention, if the supercritical fluid in a drying vessel that has already completed drying has not yet reached maximum solubility, the supercritical fluid in that vessel is directly introduced into the drying vessel next to be dried via the equalization and pressure manifold for drying. This eliminates the need for the supercritical fluid to enter a supercritical recycling system before being introduced into the drying vessel to be dried. This process eliminates the need for recycling operations, thereby avoiding unnecessary energy consumption and minimizing material loss during the recycling process.

[0028] 3. Examples and Comparative Examples Example 1 The supercritical drying requirement for a particular product is to dry 40 tons of product within three days. The drying process parameters are: drying pressure of 9.6 MPaG, a capacity of 2 tons per drying vessel, and a drying time of 9 hours. Under these drying process parameters, at least 13 tons of product needs to be dried per day.

[0029] Using the supercritical drying system described in this invention, only six drying kettles are required for the drying process, and the target can be achieved in less than three days. Due to the installation of a pressure-equalizing pipeline and staged pressure relief, the total time required for pressure increase, pressure relief, and product loading and unloading in the drying process is controlled within 1 hour. Therefore, the six drying kettles are set to operate at 3-hour intervals, as shown in the following table: Table 1 The specific operations in this embodiment are as follows: 1. Operate the supercritical circulation recovery system to ensure that the system pressure output condition reaches the required 9.6MPaG; confirm that the No. 1 drying kettle has been loaded with the product to be dried and the cover has been closed.

[0030] 2. Pressure-boosting drying: First, slowly open the feed valve of drying kettle No. 1 to a certain opening, such as 1 / 3 opening. Wait until the pressure of drying kettle No. 1 reaches 9.6MPaG, then slowly open the discharge valve of drying kettle No. 1 to a certain opening, such as 1 / 3 opening, so that drying kettle No. 1 can be dried in a stable cycle. Drying kettles No. 2 to No. 6 are operated in the same way with an interval of 3 hours.

[0031] 3. Flattening after drying: When drying kettle No. 1 completes 9 hours of drying, drying kettle No. 4 begins drying. At this time, flattening operations are performed on drying kettles No. 1 and No. 4 as follows: A. Isolation of the two drying kettles: Close the feed valve and discharge valve of drying kettle No. 1, and feed drying kettle No. 4 for the first time. Accordingly, the feed valve and discharge valve of drying kettle No. 4 are initially closed.

[0032] B. Drying kettle pressure equalization: First fully open the pressure equalization valve of drying kettle No. 4, and then slowly open the pressure equalization valve of drying kettle No. 1 to a certain opening, such as 1 / 4; wait until the pressure inside the two drying kettles reaches equilibrium, if both reach 5.8MPaG, it means that the pressure equalization operation is completed, and at this time, close the pressure equalization valves of the two drying kettles respectively.

[0033] 4. Drying kettle pressure relief: The maximum recovery pressure of the supercritical circulation recovery system is 20 MPaG. Therefore, in this embodiment, the pressure relief is divided into 5 stages, namely, stage 1 pressure relief - 20~12 MPaG, stage 2 pressure relief - 12~7 MPaG, stage 3 pressure relief - 7~3 MPaG, stage 4 pressure relief - 3~1 MPaG, and stage 5 pressure relief - 1~0 MPaG.

[0034] First open the pressure relief main valve of the pressure relief main pipe and the pressure relief branch valve of the 3rd level pressure relief, then slowly fully open the pressure relief valve of the No. 1 drying kettle to relieve the pressure; when the pressure of the drying kettle drops to 3MPaG, close the 3rd level pressure relief valve and open the 4th level pressure relief valve; when the pressure of the drying kettle drops to 1MPaG, close the 4th level pressure relief valve and open the 5th level pressure relief valve; when the pressure of the drying kettle drops to below 0.01MPaG, the No. 1 drying kettle is ready to open the cover, and the product can be taken out by opening the cover.

[0035] 5. Subsequent drying kettle pressure increase: Since the pressure increase of drying kettles No. 1 to 3 is directly pressurized by the supercritical circulation recovery system, when drying kettles No. 1 to 3 are loaded with products and there is no matching drying kettle for leveling operation, drying kettles No. 1 to 3 need to be pressurized from the supercritical circulation recovery system when drying again. The remaining drying kettles No. 4 to 6 can be pressurized by leveling operation. For example, drying kettle No. 6, which has been loaded with products, can continue to level with any other drying kettle No. 1 to 3 that has completed drying to obtain the initial pressure.

[0036] After the leveling operation is completed, the pressure of the No. 4 drying kettle has reached 5.8MPaG. At this time, slowly open the feed valve of the No. 4 drying kettle to a certain opening. When the pressure of the No. 4 drying kettle reaches 9.6MPaG, open the discharge valve of the No. 4 drying kettle to carry out the circulating drying operation of the product.

[0037] Example 2 The company is required to dry three products, A, B, and C. Product A requires a drying pressure of 9.6 MPaG, a drying time of 4 hours, and a drying weight of 6 tons; Product B requires a drying pressure of 8 MPaG, a drying time of 5 hours, and a drying weight of 2 tons; and Product C requires a drying pressure of 8.5 MPaG, a drying time of 7 hours, and a drying weight of 2 tons. Each drying kettle has a capacity of 2 tons.

[0038] Using the supercritical drying system of the present invention, four drying kettles can be set up to participate in the drying process. One of the drying kettles is not loaded with product and is only used for pressure equalization. The other three drying kettles are used to dry products A, B, and C respectively. The specific operation is shown in the following table: Table 2 The specific operations in this embodiment are as follows: 1. Operate the supercritical recycling system to achieve the required pressure output of 9.6 MPaG. Before the first hour, confirm that the No. 1 drying kettle is loaded with Product A and has its cover closed. The No. 4 empty drying kettle is in its initial state, with both its feed and discharge valves closed.

[0039] 2. Pressure-boosting drying: In the first hour, slowly open the feed valve of No. 1 drying kettle to a certain opening, such as 1 / 3 opening. When the pressure of No. 1 drying kettle reaches 9.6MPaG, slowly open the discharge valve of No. 1 drying kettle, such as 1 / 3 opening, to ensure stable circulation drying of No. 1 drying kettle.

[0040] 3. Before the 5th hour, confirm that drying kettle No. 2 has been loaded with product B and the lid is closed.

[0041] Drying kettle pressure equalization: Within the 5th hour, first perform pressure equalization on drying kettles No. 1 and 2. First, fully open the pressure equalization valve of drying kettle No. 2, and then slowly open the pressure equalization valve of drying kettle No. 1 to a certain opening, such as 1 / 4. Wait until the pressure inside drying kettles No. 1 and 2 reaches equilibrium, such as reaching 5.8MPaG, which marks the end of the pressure equalization operation. At this time, close the pressure equalization valves of drying kettles No. 1 and 2 respectively.

[0042] Within the 5th hour, perform the leveling operation on drying kettles 1 and 4. Repeat the above leveling operation, leveling the residual pressure in drying kettle 1 with the empty kettle 4, and transferring the residual pressure in drying kettle 1 to the empty kettle 4 until it reaches equilibrium, such as 3 MPaG.

[0043] 4. After the No. 2 drying kettle has completed the leveling pressure, slowly open the feed valve of the No. 2 drying kettle to a certain opening, such as fully open; wait until the pressure of the No. 1 drying kettle reaches 8MPaG, then slowly open the discharge valve of the No. 2 drying kettle to a certain opening, such as 1 / 4 opening; at the same time, adjust the opening of the feed valve of the No. 2 drying kettle to a certain opening, such as 1 / 4 opening, so that the No. 2 drying kettle can stably circulate and dry.

[0044] 5. In this embodiment, the drying kettle pressure relief: the maximum recovery pressure of the supercritical circulation recovery system is 15 MPaG. In this embodiment, the pressure relief segmentation is 4-level pressure relief, namely, level 1 pressure relief - 15~7.5 MPaG, level 2 pressure relief - 7.5~3 MPaG, level 3 pressure relief - 3~1 MPaG, and level 4 pressure relief - 1~0 MPaG.

[0045] First, open the pressure relief main valve of the pressure relief main pipe and the pressure relief branch valve of the 2nd level pressure relief, and then slowly fully open the pressure relief valve of the No. 1 drying kettle to relieve the pressure; when the pressure of the drying kettle drops to 3MPaG, close the pressure relief branch valve of the 2nd level pressure relief and open the pressure relief branch valve of the 3rd level pressure relief; when the pressure of the drying kettle drops to 1MPaG, close the pressure relief branch valve of the 3rd level pressure relief and open the pressure relief branch valve of the 4th level pressure relief; when the pressure of the drying kettle drops to below 0.01MPaG, the No. 1 drying kettle is ready for opening the cover. After opening the cover and taking out the product, continue to load the A product that needs to be dried.

[0046] 6. Drying kettle leveling: Within the 6th hour, level the drying kettles 1 and 4. Repeat the above-mentioned leveling operation until the pressures of drying kettles 1 and 4 reach equilibrium. If both reach 1.7 MPaG, the leveling operation is completed. At this time, close the leveling valves of drying kettles 1 and 4 respectively.

[0047] 7. Drying kettle pressure boost: Within the 6th hour, repeat the drying kettle pressure boost operation to stabilize the No. 1 drying kettle at 9.6MPaG for cyclic drying.

[0048] 8. Before the 10th hour, confirm that drying kettle No. 3 has been loaded with product C and the lid is closed.

[0049] Drying kettle flat press: A. Within the 10th hour, first perform pressure equalization on drying kettles No. 3 and No. 4. Repeat the above pressure equalization operation until the pressures of drying kettles No. 3 and No. 4 reach equilibrium. If both reach 0.9 MPaG, the pressure equalization operation is completed. At this time, close the pressure equalization valves of drying kettles No. 3 and No. 4 respectively.

[0050] B. After completing the previous step, perform the pressure leveling operation on drying kettles No. 2 and 3. Repeat the above pressure leveling operation on drying kettles No. 3 and 4 until the pressure reaches equilibrium. If both reach 4.3 MPaG, the pressure leveling operation is completed. At this time, close the pressure leveling valves of drying kettles No. 3 and 4 respectively.

[0051] C. After completing the previous step, perform the pressure equalization operation on drying kettles No. 1 and 3. Repeat the above pressure equalization operation on drying kettles No. 1 and 3 until the pressures of drying kettles No. 1 and 3 reach equilibrium. If both reach 7MPaG, the pressure equalization operation is completed. At this time, close the pressure equalization valves of drying kettles No. 1 and 3 respectively.

[0052] Pressure-boosting drying: Within the 10th hour, repeat the pressure-boosting operation of the drying kettle to stabilize the No. 3 drying kettle at 9.6 MPaG for cyclic drying.

[0053] 9. Drying kettle flat press: A. Within the 10th hour, perform pressure equalization on drying kettles No. 2 and No. 4. Repeat the above pressure equalization operation until the pressures of drying kettles No. 2 and No. 4 reach equilibrium. If both reach 2.5 MPaG, the pressure equalization operation is completed. At this time, close the pressure equalization valves of drying kettles No. 2 and No. 4 respectively.

[0054] B. Within the 10th hour, perform pressure equalization on drying kettles 1 and 4. Repeat the above pressure equalization operation until the pressures of drying kettles 1 and 4 reach equilibrium. If both reach 4.7 MPaG, the pressure equalization operation is completed. At this time, close the pressure equalization valves of drying kettles 1 and 4 respectively.

[0055] Drying kettle pressure relief: A. First open the pressure relief main valve 17 and the pressure relief branch valve of the 2nd level pressure relief, then slowly fully open the pressure relief valve of the No. 1 drying kettle to relieve the pressure; when the pressure of the drying kettle drops to 3MPaG, close the pressure relief branch valve of the 2nd level pressure relief, and open the pressure relief branch valve of the 3rd level pressure relief; when the pressure of the drying kettle drops to 1MPaG, close the pressure relief branch valve of the 3rd level pressure relief, and open the pressure relief branch valve of the 4th level pressure relief; when the pressure of the drying kettle drops to below 0.01MPaG, the No. 1 drying kettle is ready for opening. After opening the cover and taking out the product, continue to load the A product that needs to be dried.

[0056] B. First open the pressure relief main valve and the pressure relief branch valve of the 3rd level pressure relief, then slowly fully open the pressure relief valve of the No. 2 drying kettle to relieve the pressure; when the pressure of the drying kettle drops to 1MPaG, close the pressure relief branch valve of the 3rd level pressure relief, and open the pressure relief branch valve of the 4th level pressure relief; when the pressure of the drying kettle drops below 0.01MPaG, the No. 1 drying kettle is ready to open the cover, and the cover is opened to take out Product B.

[0057] 10. Drying kettle pressure leveling: Within the 11th hour, perform pressure leveling on drying kettles No. 1 and 4. Repeat the above pressure leveling operation until the pressures of drying kettles No. 1 and 4 reach equilibrium. If both reach 2.3 MPaG, the pressure leveling operation is completed. At this time, close the pressure leveling valves of drying kettles No. 1 and 4 respectively.

[0058] Pressure-boosting drying: Within the 11th hour, repeat the pressure-boosting operation of the drying kettle to stabilize the No. 1 drying kettle at 9.6 MPaG for cyclic drying.

[0059] Drying kettle pressure relief: During the cycle drying period of drying kettles No. 1 and 3, the pressure relief of drying kettle No. 4 can be carried out in stages. First, open the pressure relief main valve and the pressure relief branch valve of the 3rd-level pressure relief, then slowly fully open the pressure relief valve of drying kettle No. 4 to relieve the pressure. When the pressure of the drying kettle drops to 1MPaG, close the pressure relief branch valve of the 3rd-level pressure relief and open the pressure relief branch valve of the 4th-level pressure relief. When the pressure of the drying kettle drops below 0.01MPaG, the pressure relief of drying kettle No. 4 is completed.

[0060] 11. Drying kettle pressure relief: A. Within the 15th hour, first open the pressure relief main valve and the pressure relief branch valve of the 1st level pressure relief, then slowly fully open the pressure relief valve of the No. 1 drying kettle to relieve the pressure; when the pressure of the drying kettle drops to 7.5MPaG, close the pressure relief branch valve of the 1st level pressure relief, and open the pressure relief branch valve of the 2nd level pressure relief; when the pressure of the drying kettle drops to 3MPaG, close the pressure relief branch valve of the 2nd level pressure relief, and open the pressure relief branch valve of the 3rd level pressure relief; when the pressure of the drying kettle drops to 1MPaG, close the pressure relief branch valve of the 3rd level pressure relief, and open the pressure relief branch valve of the 4th level pressure relief; when the pressure of the drying kettle drops to below 0.01MPaG, the No. 1 drying kettle is ready for opening, and the A product can be taken out of the lid.

[0061] B. Within the 17th hour, first open the pressure relief main valve and the pressure relief branch valve of the 1st level pressure relief, and then slowly fully open the pressure relief valve of the No. 3 drying kettle to relieve the pressure; when the pressure of the drying kettle drops to 7.5MPaG, close the pressure relief branch valve of the 1st level pressure relief, and open the pressure relief branch valve of the 2nd level pressure relief; when the pressure of the drying kettle drops to 3MPaG, close the pressure relief branch valve of the 2nd level pressure relief, and open the pressure relief branch valve of the 3rd level pressure relief; when the pressure of the drying kettle drops to 1MPaG, close the pressure relief branch valve of the 3rd level pressure relief, and open the pressure relief branch valve of the 4th level pressure relief; when the pressure of the drying kettle drops to below 0.01MPaG, the No. 1 drying kettle is ready for opening, and the cover is opened to take out Product C.

[0062] The valves involved in the above-described operation process in Example 2 are all remote-controlled valves. This process can be stably implemented using a control system. For example, a SCADA+PLC / DCS system can be employed. The DCS implements timing control of multiple valves through decentralized control stations, while integrating process control (such as PID regulation). Timing logic can be linked to process parameters, triggering the valve to open or close when process parameters such as pressure and reaction time reach set values, while simultaneously recording a timestamp. Using a SCADA system, remote monitoring and parameter setting can be achieved through host computer software (such as Intouch or WinCC). Operators can modify valve timing parameters (such as adjusting the opening duration) from the central control room and record valve operation logs for easy traceability and optimization. Therefore, the above process can be stably and continuously implemented using control systems commonly used in the chemical industry. Therefore, the present invention does not limit this control system.

[0063] Comparative Example 1 If the traditional supercritical drying process is used, there will only be a system with serial drying kettles. The equipment in the system can only be started and stopped at the same time, resulting in this type of drying process system being able to dry only one product at a time. If the product volume is not large, it will lead to waste of equipment and energy consumption, and increase the operation and maintenance costs of the product.

[0064] Comparative Example 2 If the traditional supercritical drying process is used, there is only a system with parallel drying kettles. The number of drying kettles used is limited by the maximum load of the supercritical pressurizing equipment. If you want to increase the number of drying kettles, you must also increase the number of pressurizing equipment, resulting in an increase in equipment investment, operation and maintenance costs, and energy consumption.

[0065] It can be seen from the comparison of the embodiments and the comparative examples that: (1) Examples 1 and 2 use the equipment and method of the present invention for drying, breaking through the limitation of single product processing of traditional processes and realizing parallel processing of multiple products. Compared with Comparative Example 1, the traditional supercritical drying system has the problem that the equipment needs to be "started and stopped at the same time", and can only dry one product at a time, which cannot adapt to the needs of multiple varieties and differentiated parameters (such as pressure, time, weight), resulting in idle equipment during small batch and multi-variety production, causing energy consumption and cost waste. The system of Example 2 of the present invention uses 4 drying kettles (including 1 flat press spare kettle) to simultaneously process three products A, B, and C with different drying pressures (9.6 MPaG, 8 MPaG, 8.5 MPaG), different drying times (4 h, 5 h, 7 h), and different weights (6 t, 2 t, 2 t), and coordinates pressure adaptation through multiple flat press operations (such as No. 1 and No. 2, No. 3 and No. 4, etc.), realizing parallel processing of multiple products, solving the core limitation of "single product processing" of traditional processes, and greatly improving the versatility and production flexibility of the equipment.

[0066] (2) The present invention can optimize the number and utilization of equipment and reduce equipment investment costs. In Example 2, the number of drying kettles in the traditional parallel drying kettle system is limited by the maximum load of the supercritical pressure equipment. If more drying kettles are needed, the pressure equipment must be added simultaneously, resulting in a significant increase in equipment investment, operation and maintenance costs, and energy consumption. In contrast, Example 1 of the present invention targets the requirement of "drying 40 tons of products within 3 days (at least 13 tons per day)". Each drying kettle has a capacity of 2 tons and a drying time of 9 hours. Through the pressure-scaling pipeline and graded pressure relief, the total time for "pressurization + pressure relief + loading and unloading" is controlled to 1 hour. Only 6 drying kettles are required to operate at a staggered interval of 3 hours to achieve the goal (as shown in Table 1, each drying kettle operates continuously in a cycle without long periods of idle time). In Example 2, only 4 drying kettles (including 1 spare pressure-scaling kettle) are used to process a variety of different product needs. The pressure-scaling operation (such as using the empty kettle No. 4 to transfer pressure) reduces the direct dependence on the pressure equipment, and no additional pressure equipment is required. It can be seen that the present invention greatly reduces the number of required drying kettles while meeting production needs through designs such as staggered operation and pressure recovery, and does not require additional investment in pressurizing equipment due to the addition of equipment, thereby significantly reducing equipment investment costs.

[0067] (3) The method of the present invention uses the equipment to shorten the non-drying time, improve the equipment turnover efficiency, and recover the pressure by flattening operation. For example, in Example 1, the No. 1 drying kettle (drying completed) and the No. 4 drying kettle (loading completed) are flattened to transfer the remaining pressure (9.6 MPaG) of the No. 1 kettle to the No. 4 kettle, so that the initial pressure of the No. 4 kettle reaches 5.8 MPaG, which greatly shortens the time for subsequent pressure increase to the target pressure (9.6 MPaG); in Example 2, the No. 4 empty kettle is used to flatten with other kettles, further reducing the pressure. The system reduces reliance on pressurizing equipment; at the same time, pressure relief is accelerated through a graded approach. For example, Example 1 employs a five-stage pressure relief system (20-12 MPaG to 1-0 MPaG), while Example 2 employs a four-stage pressure relief system (15-7.5 MPaG to 1-0 MPaG). This staged control makes the pressure relief process more efficient. Combined with the pressure leveling operation, the total time for "pressurization + pressure relief + loading and unloading" is controlled within 1 hour (Example 1), significantly reducing equipment idle time and improving the drying kettle's turnover efficiency (number of drying batches per unit time). Ultimately, this overcomes the bottleneck of the traditional process: the traditional process lacks a pressure leveling and graded pressure relief design. Pressure boosting relies on direct pressure supply from pressurizing equipment, and pressure relief has no staged control. This results in excessively long non-drying steps such as "pressurization + pressure relief + loading and unloading," resulting in a low proportion of the equipment's effective drying time and poor turnover efficiency.

[0068] (4) In practical applications, the present invention can reduce energy consumption and operation and maintenance costs and adapt to diversified production needs. In terms of energy consumption, the leveling operation recycles and utilizes the residual pressure (such as the leveling transfer pressure between kettle No. 1 and kettle No. 4 in Example 2), which reduces the energy consumption of the pressurizing equipment; the graded pressure relief avoids the energy loss caused by the sudden drop in pressure, and overall reduces the energy consumption per unit product; in terms of operation and maintenance costs, 10 drying kettles can be pre-designed, so that in actual production, the number of operating drying kettles can be determined according to production needs (such as 6 in Example 1 and 4 in Example 2), without the need for additional pressurizing equipment, which directly reduces the equipment maintenance, depreciation and other operation and maintenance costs; at the same time, the system can adapt to diversified needs such as "large batch single product" (Example 1) and "small batch multiple products" (Example 2), avoiding the cost waste of traditional processes in specific scenarios.

[0069] In summary, the present invention realizes pressure recovery through "smoothing pressure pipeline design", shortens pressure relief time through "graded pressure relief", and improves equipment utilization through "peak-shifting operation". Compared with traditional processes, it has significant improvements in multi-product processing capacity, equipment quantity optimization, turnover efficiency, energy consumption and cost control, etc. It can flexibly adapt to the drying needs of different batches and different types of products, and solves the core limitations of traditional processes.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A series-parallel hybrid supercritical drying system, characterized in that: The drying system comprises a plurality of drying kettles (1), wherein a feed port, a pressure relief port and a pressure relief port are provided at the top of the drying kettle, and a discharge port is provided at the bottom of the drying kettle; The feed port is fluidically connected to one end of the feed main pipe (2), and the other end of the feed main pipe (3) is fluidically connected to the supercritical circulation recovery system (4); the pressure relief port is fluidically connected to one end of the pressure relief main pipe (6) through the pressure relief pipe (5), and the other end of the pressure relief main pipe is fluidically connected to the graded pressure relief main pipe (7); the discharge port is fluidically connected to one end of the discharge main pipe (9) through the discharge pipe (8), and the other end of the discharge main pipe is fluidically connected to the supercritical circulation recovery system; the equalizing pressure port is fluidically connected to the equalizing pressure main pipe (11) through the equalizing pressure pipe (10); The hierarchical pressure relief main pipe (7) is fluidically connected to one end of a plurality of pressure relief branch pipes (12), and the other end of the pressure relief branch pipe is fluidically connected to a supercritical circulation recovery system; the supercritical circulation recovery system is used to recover the supercritical fluid after the drying process in the drying kettle, and to perform a recovery process on the supercritical fluid. Subsequently, the recovered supercritical fluid is pressurized and then enters each drying kettle through the feed main pipe, the feed pipe and the feed port.

2. The supercritical drying system according to claim 1, characterized in that: A feed valve (13) is provided on the feed pipe for controlling the switching of the medium in the feed pipe; a pressure relief valve (14) is provided on the pressure relief pipe for controlling the switching of the medium in the pressure relief pipe; a pressure equalizing valve (15) is provided on the pressure equalizing pipe for controlling the switching of the medium in the pressure equalizing pipe; a discharge valve (16) is provided on the discharge pipe for controlling the switching of the medium in the discharge pipe; a pressure relief main pipe valve (17) is provided at one end of the pressure relief main pipe (6) close to the graded pressure relief main pipe (7) for controlling the switching of the medium in the pressure relief main pipe; and a pressure relief branch pipe valve (18) is provided on each pressure relief branch pipe for controlling the switching of the medium in the pressure relief branch pipe.

3. The supercritical drying system according to claim 1, characterized in that: The number of the pressure relief branches is consistent with the pressure relief level; and the pressure relief level is set according to the maximum operating pressure of the recovery device in the supercritical circulation recovery system, the drying pressure of the drying kettle and the phase change pressure of the supercritical fluid used.

4. The supercritical drying system according to claim 1, characterized in that: The feed ports of each two adjacent drying kettles are fluidly connected through a feed main pipe; the pressure relief ports of each two adjacent drying kettles are fluidly connected through a pressure relief main pipe; and the pressure equalization ports of each two adjacent drying kettles are fluidly connected through a pressure equalization main pipe.

5. A supercritical drying process of series-parallel mixing, characterized in that: Supercritical drying is performed using the supercritical drying system according to any one of claims 1 to 4, and the specific steps are as follows: Step 1: Determine the number of drying kettles involved in supercritical drying treatment based on production needs; Step 2: Start the supercritical circulation recovery system and make the system pressure output reach the pressure required by the drying process. At the same time, the product to be dried is loaded into the drying kettle and the lid of the drying kettle is closed; Step 3: Open the feed valve of the drying kettle and control the opening and the flow rate of the supercritical fluid to make the pressure and flow rate inside the drying kettle reach the required drying process, and then control the opening of the discharge valve to make the drying kettle perform cyclic drying under stable pressure and flow rate; Step 4: After the drying kettle has completed drying, open the pressure relief branch valves on multiple pressure relief branches in sequence to gradually reduce the pressure of the drying kettle to meet the conditions for opening the cover, open the drying kettle, and take out the dried product.

6. The supercritical drying process according to claim 5, characterized in that: In step 4, when the number of drying kettles involved in the supercritical drying process is greater than or equal to 2, a pressure leveling operation is performed before pressure relief, as follows: S1: For the drying kettle that has completed the drying process, close its feed valve and discharge valve; for the drying kettle that has not yet been dried, keep its feed valve and discharge valve in the initial state, that is, all valves are closed; S2: First, open the pressure-equalizing valves of multiple drying kettles that need drying treatment, and then open the pressure-equalizing valves of the drying kettles that have completed the drying treatment to a certain opening, so that the pressure in the drying kettles that need to participate in the drying process rises to equilibrium. After the pressure equalization is completed, close the pressure-equalizing valves of all drying kettles.

7. The supercritical drying process according to claim 5, characterized in that: When the drying kettle that has completed the drying process is subjected to drying process again, it is first subjected to the S1-S2 flat pressure operation, and then the supercritical circulation recovery system is used to increase the pressure and feed the material, so as to carry out the subsequent drying process.

8. The supercritical drying process according to claim 5, characterized in that: For a drying kettle that has completed drying, if the supercritical fluid in the drying kettle has not yet reached the maximum solubility, the supercritical fluid in the kettle is directly introduced into the drying kettle that is about to be dried through the equalization and pressure main pipe for drying.

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