Drying method, drying device and production system

Abstract

The embodiment of the invention provides a drying method, a drying device and a production system.The drying method comprises the following steps that a to-be-dried product is subjected to first-stage drying treatment through an intermediate heat medium, and a first-stage dried product and a low-temperature medium are obtained; performing second-stage drying treatment on the first-stage dried product by adopting a thermal medium to obtain a final product and the intermediate thermal medium; and returning the intermediate heat medium to participate in the primary drying treatment. The drying method is more efficient and energy-saving, and the drying effect is uniform and thorough.

Description

TECHNICAL FIELD

[0001] The present application relates to the chemical industry field, and in particular to a drying method, a drying device and a production system. BACKGROUND

[0002] Polyoxymethylene (POM) is a kind of high polymer engineering plastic with excellent comprehensive performance. It has been widely used in many industrial fields due to its high mechanical strength, excellent rigidity, excellent fatigue resistance, excellent creep resistance, good chemical resistance and low friction coefficient. It is widely used in the manufacture of precision gears, bearings, cams, pump body parts, valve parts, fasteners, automobile fuel system components, electronic and electrical structural parts, medical device parts, etc. Especially in the occasions requiring high dimensional stability, wear resistance, repeated impact resistance and dynamic load bearing, it becomes one of the ideal materials to replace metal. With the development of high-end manufacturing and precision instruments, more stringent requirements are put forward for the dimensional accuracy, surface finish, long-term stability and mechanical property consistency of polyoxymethylene parts, and its application depth and breadth continue to expand.

[0003] It is worth noting that polyoxymethylene itself is extremely sensitive to moisture. The ether bond in the molecular chain is easily hydrolyzed under the action of trace moisture and heat, resulting in molecular chain degradation. This characteristic determines that drying treatment is an indispensable key pretreatment step before polyoxymethylene is processed and formed. Polyoxymethylene raw materials that have not been sufficiently dried are prone to cause a series of serious defects such as molecular weight reduction, unstable melt viscosity, internal bubbles, silver lines, rough surface and poor gloss during subsequent melt extrusion or injection molding. More importantly, moisture-induced thermal degradation can significantly degrade the physical and mechanical properties of the final product, such as a significant decrease in impact strength and tensile strength, poor dimensional stability, and may shorten the service life of the product. Therefore, the drying effect directly determines whether polyoxymethylene can exhibit its inherent excellent performance, and ultimately affects the quality grade and application reliability of the product, and has a decisive influence in the entire processing chain.

[0004] However, the polyoxymethylene drying process commonly used in current industrial production often has unsatisfactory drying effect and high energy consumption. This contradiction between high energy consumption and unstable and incomplete drying effect has become a common technical bottleneck restricting the high-quality, high-efficiency and low-cost processing and application of polyoxymethylene. SUMMARY

[0005] The embodiments of the present application provide a drying method, which is more efficient, energy-saving and has uniform and complete drying effect.

[0006] The embodiments of the present application provide a drying device, which helps to realize the above drying method and has simple structure and low equipment cost.

[0007] The embodiment of the present application provides a production system, which can obtain a product with lower solvent content at lower production energy consumption.

[0008] The embodiment of the present application provides a drying method, which comprises the following steps:

[0009] The intermediate heat medium is used to perform primary drying treatment on the product to be dried, so as to obtain the primary drying product and low-temperature medium.

[0010] The heat medium is used to perform secondary drying treatment on the primary drying product, so as to obtain a final product and the intermediate heat medium.

[0011] The intermediate heat medium is returned to participate in the primary drying treatment.

[0012] The drying method as described above, wherein before the intermediate heat medium is returned to participate in the primary drying treatment, the method further comprises:

[0013] The intermediate heat medium is used to perform heat exchange treatment on an initial medium, and the initial medium is heated to the heat medium.

[0014] The drying method as described above, wherein the heat exchange treatment comprises:

[0015] The low-pressure steam is used to perform first heat exchange treatment on the initial medium, and the initial medium is heated to intermediate initial medium; and the intermediate heat medium is used to perform second heat exchange treatment on the intermediate initial medium, and the intermediate initial medium is heated to the heat medium.

[0016] The drying method as described above, wherein before the heat exchange treatment, the method further comprises: performing gas-solid separation treatment on the intermediate heat medium; and / or,

[0017] After the low-temperature medium is heated, the low-temperature medium is returned to perform the secondary drying treatment on the primary drying product.

[0018] The drying method as described above, wherein the product to be dried is polyformaldehyde.

[0019] The temperature of the heat medium is 142-148 DEG C.

[0020] The temperature of the intermediate heat medium before the heat exchange treatment is not lower than 125 DEG C, and the temperature of the intermediate heat medium after the heat exchange treatment is not lower than 115 DEG C.

[0021] The application provides a drying device for performing the drying method described in any of the above, wherein the drying device comprises a first drying unit and a second drying unit; the first drying unit comprises a first drying inlet, a first drying outlet, a first medium inlet and a first medium outlet; the second drying unit comprises a second drying inlet, a second drying outlet, a second medium inlet and a second medium outlet;

[0022] The first drying outlet is communicated with the second drying inlet, and the second medium outlet is communicated with the first medium inlet.

[0023] The drying device described above further comprises a heat exchange unit, wherein the heat exchange unit comprises a low-temperature medium inlet, a high-temperature medium outlet, a heat exchange medium inlet and a heat exchange medium outlet;

[0024] The high-temperature medium outlet is communicated with the second medium inlet, and the second medium outlet is communicated with the first medium inlet in sequence through the heat exchange medium inlet and the heat exchange medium outlet.

[0025] The drying device described above further comprises a heat exchange unit, wherein the heat exchange unit comprises a first heat exchange subunit and a second heat exchange subunit; the first heat exchange subunit comprises a first medium channel and a first heat exchange channel surrounding at least part of the outer surface of the first medium channel, and the first medium channel comprises a low-temperature medium inlet and an intermediate medium outlet; the second heat exchange subunit comprises a second medium channel and a second heat exchange channel surrounding at least part of the outer surface of the second medium channel, and the second medium channel comprises an intermediate medium inlet and a high-temperature medium outlet; the intermediate medium outlet is communicated with the intermediate medium inlet;

[0026] The first heat exchange channel comprises a low-pressure steam inlet and a condensate outlet;

[0027] The second heat exchange channel comprises a heat exchange medium inlet and a heat exchange medium outlet.

[0028] The drying device described above further comprises a gas-solid separation unit, wherein the gas-solid separation unit comprises a separation inlet, a gas phase outlet and a solid phase outlet; the second medium outlet is communicated with the heat exchange medium inlet in sequence through the separation inlet and the gas phase outlet; and / or,

[0029] The drying device described above further comprises a heat-driven unit, wherein the heat-driven unit comprises a heat-driven inlet and a heat-driven outlet; the heat-driven inlet is communicated with the first medium outlet, and the heat-driven outlet is communicated with the second medium inlet.

[0030] The application further provides a production system, wherein the production system comprises a preparation device and the drying device described in any of the above.

[0031] The crude product outlet of the preparation device is connected to the primary drying inlet of the drying device.

[0032] In the drying method provided in this application embodiment, since the solvent content of the first-stage dried product is lower than that of the product to be dried, a heat medium is used to first perform a second-stage drying treatment on the first-stage dried product. This is equivalent to using a higher-heat heat medium to preferentially heat the product with the lower solvent content. At this time, the high-quality heat contained in the higher-heat heat medium can provide a strong thermodynamic driving force, efficiently breaking the solvent's binding force on the product, achieving rapid and deep removal of the solvent, and obtaining the final product and intermediate medium. At the same time, the intermediate heat medium also retains more residual heat, which can provide a large amount of evaporation heat for the product to be dried, thereby helping to efficiently complete the first-stage drying treatment and obtain the first-stage dried product for the second-stage drying treatment. Therefore, the drying method of this application embodiment not only has higher energy utilization but also has a better drying effect. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the drying apparatus according to an embodiment of this application;

[0034] Figure 2 This is another schematic diagram of the drying apparatus according to an embodiment of this application;

[0035] Figure 3 This is another schematic diagram of the drying apparatus according to an embodiment of this application;

[0036] Figure 4 This is another schematic diagram of the drying apparatus according to an embodiment of this application;

[0037] Figure 5 This is a schematic diagram of a comparative drying apparatus according to this application. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] As mentioned above, the current drying effect of polyoxymethylene is poor and the energy consumption is high. In order to reduce energy consumption and the amount of polyoxymethylene solvent, the inventors have studied thermodynamic efficiency, mass and heat transfer and medium flowability, and proposed the drying method of the embodiment of this application.

[0040] The first aspect of this application provides a drying method, including the following steps:

[0041] An intermediate heat medium is used to perform a primary drying process on the product to be dried, resulting in a primary dried product and a low-temperature medium.

[0042] A heat medium is used to perform a secondary drying process on the primary dried product to obtain the final product and an intermediate heat medium.

[0043] The intermediate heat medium is returned to participate in the primary drying process.

[0044] The drying method described in this application is applicable to drying any product, and there are no limitations on the type of product or solvent in the product. For example, the product to be dried may be polyoxymethylene, and the solvent may include at least one of water, formaldehyde, trioxymethylene, and methanol. Furthermore, the composition of the heat medium is not limited in this application; for example, it may be heated air.

[0045] The drying method of this application optimizes the flow direction of the heat medium. Following a drying sequence where the heat medium undergoes a secondary drying process followed by a primary drying process, a high-calorific-value heat medium is preferentially used for the secondary drying process (final drying process), while a lower-calorific-value medium (intermediate heat medium) is reused for the primary drying process. Specifically, a heat medium with a higher calorific value is first used to perform a secondary drying process on the primary dried product. The solvent in the primary dried product absorbs the heat from the heat medium to complete the final drying, resulting in the final product. Simultaneously, the heat of the heat medium decreases, becoming an intermediate heat medium. This intermediate heat medium then performs a primary drying process on the product to be dried. After some of the solvent in the dried product absorbs the heat from the intermediate heat medium, the solvent content decreases, resulting in a primary dried product, and the intermediate heat medium decreases in temperature, becoming a low-temperature medium. This application does not limit the treatment method of the low-temperature medium; for example, it can be directly discharged.

[0046] Specifically, the primary dried product is the product after the primary drying process, and therefore has a lower solvent content than the product to be dried. During their research, the inventors discovered that the key to effectively utilizing the heat carried by the heat transfer medium lies in the precise matching of its quality with the difficulty of solvent removal from the product to be dried. When the high-temperature heat transfer medium first contacts the primary dried product with a low solvent content, the solvent in the primary dried product is more tightly bound to the product, especially when the solvent includes water, which mainly exists as bound water. Therefore, solvent removal requires overcoming higher intermolecular forces, making removal more difficult. The drying method of this application uses a heat transfer medium with higher heat for the secondary drying process. The high-quality heat contained in the heat transfer medium provides a strong thermodynamic driving force, efficiently breaking down solvent bonds and achieving rapid and deep solvent removal. During this process, the heat transfer medium's temperature moderately decreases due to the evaporation of a small amount of solvent, becoming an intermediate heat transfer medium, but its residual heat still has considerable value.

[0047] Subsequently, this intermediate heat medium, which has cooled but is not yet saturated, is used by the product to be dried, which has a high solvent content. The product contains a large amount of easily evaporating free solvent. The solvent removal process mainly consumes a large amount of latent heat of vaporization but has relatively low temperature requirements, while the intermediate heat medium can provide the necessary large amount of heat for evaporation. Therefore, the drying method in this embodiment, which involves a two-stage drying process followed by a single-stage drying process with a high-heat heat medium, avoids the rapid consumption and devaluation of the high-quality heat medium during the evaporation of free solvent. This achieves the tiered utilization of heat from high to low temperatures, significantly reducing the waste of high-grade thermal energy and improving overall energy utilization.

[0048] Furthermore, as the low-solvent product with the most difficult solvent removal, the primary dried product in this embodiment is dried using a high-temperature, dry heat medium with the strongest drying potential to ensure it receives sufficient driving force to meet the requirements of deep drying. More importantly, this also effectively avoids "contamination" of the heat medium by the product to be dried, thereby ensuring the overall drying quality of both the primary dried product and the final product.

[0049] It should be particularly noted that the drying method proposed in this application, by optimizing the heat energy cascade utilization path and the drying kinetic matching mechanism, achieves a significant improvement in energy utilization efficiency and an optimization and upgrade of the dried product quality. Based on this advantage, the heat and mass transfer intensity can be dynamically adjusted during the drying process. For example, the wind speed of the heat medium can be appropriately increased in the secondary drying process to increase mass transfer, and the wind speed of the intermediate heat medium can be appropriately reduced in the primary drying process to extend the primary drying time. While ensuring drying uniformity, this effectively reduces the operating load of the fans in the primary and secondary drying processes, which not only directly reduces power consumption and achieves significant energy-saving benefits, but also slows down the mechanical wear rate of the equipment and extends the maintenance cycle of the fan components and transmission system by reducing the fan operating intensity.

[0050] The embodiments of this application do not limit the specific method of obtaining the heat medium. In one specific implementation, before returning the intermediate heat medium to participate in the first-stage drying process, it further includes: using the intermediate heat medium to perform heat exchange treatment on the initial medium, so that the initial medium is heated to become a heat medium.

[0051] In detail, the heat medium is obtained by heat exchange treatment of the initial medium. That is, during the heat exchange treatment between the intermediate heat medium and the initial medium, the low-temperature initial medium absorbs the heat of the intermediate heat medium and rises to become the heat medium. After heat exchange treatment, the intermediate heat medium continues to participate in the primary drying treatment to dry the product.

[0052] In this process, the intermediate heat medium undergoes heat exchange and primary drying treatment sequentially. By adding heat exchange treatment, the heat carried by the intermediate heat medium is deeply extracted and fully utilized, achieving efficient cascade recovery of thermal energy. Simultaneously, during the stage where the initial medium is heated and transformed into a heat medium, the intermediate heat medium pre-bears part of the heat load from heating the initial medium, significantly reducing the heat demand from external heat sources. This synergistic effect of thermal energy recycling and reduced external heat demand effectively optimizes the overall thermodynamic efficiency, thereby achieving the goals of reducing energy consumption indicators and controlling drying operation costs.

[0053] Furthermore, in order to meet the heat demand of the heat medium, the heat exchange treatment includes: using low-pressure steam to perform a first heat exchange treatment on the initial medium, thereby raising the initial medium to become an intermediate initial medium; and using an intermediate heat medium to perform a second heat exchange treatment on the intermediate initial medium, thereby raising the intermediate initial medium to become a heat medium.

[0054] That is, firstly, the initial medium is subjected to a first heat exchange treatment using external low-pressure steam. The initial medium absorbs the heat of the low-pressure steam and becomes an intermediate initial heat medium. Then, the intermediate initial heat medium is subjected to a second heat exchange treatment using an intermediate heat medium from the second drying treatment to obtain a heat medium that meets the requirements of the second drying treatment.

[0055] In the drying method of this application embodiment, the above-mentioned two-pass heat exchange mode achieves significant optimization of heat energy utilization efficiency by constructing a gradient heat energy recovery system. In the first stage, when using low-pressure steam for the first heat exchange treatment, the initial medium rapidly absorbs the sensible and latent heat of the steam to complete the temperature rise. Subsequently, in the second heat exchange treatment stage, it is deeply heated by the waste heat of the intermediate heat medium. This staged heat recovery mechanism not only allows the enthalpy of the low-pressure steam to be fully released, but also transforms the consumption of high-grade energy that originally needed to be supplied externally into internal waste heat recycling, greatly reducing the overall heat energy preparation cost. At the same time, the synergistic effect of the two heat sources effectively improves the process stability. Specifically, the low-pressure steam heat exchange provides basic heat load guarantee, and the waste heat exchange achieves precise temperature regulation. The complementarity of the two significantly narrows the fluctuation range of the heat medium outlet parameters. Even in the face of dynamic changes in the second drying treatment, it can still respond quickly by adjusting the steam flow rate to ensure the stability of the heat medium quality.

[0056] In one specific embodiment, in order to reduce the contamination of the intermediate heat medium on the product to be dried and to avoid damage to the heat exchange unit during the heat exchange process, the intermediate heat medium is further subjected to gas-solid separation treatment before the heat exchange process.

[0057] During the process of the heat medium coming into contact with the primary dried product and transforming into an intermediate heat medium, it inevitably carries some solid particles from the primary dried product. Therefore, after the secondary drying process, to ensure that the solid particles in the intermediate heat medium do not affect the heat exchange process and the primary drying process, this embodiment further performs gas-solid separation treatment on the intermediate heat medium before the heat exchange process, reducing the amount of solid particles carried by the intermediate heat medium. On the one hand, the implementation of this gas-solid separation treatment reduces the degree of solid contamination of the intermediate heat medium on the product to be dried during the primary drying process, which helps to improve the purity and quality stability of the final product. On the other hand, it also avoids the deposition and adhesion of solid particles on the inner wall of the heat exchange unit (wall adhesion phenomenon) and the blockage of the pipeline system during the heat exchange process. This ensures the efficient heat transfer performance of the heat exchange process and extends the fault-free operation cycle of the heat exchange unit, thereby reducing the frequency of equipment maintenance and optimizing the control of operation and maintenance costs.

[0058] Furthermore, although the temperature of the cryogenic medium is lower than that of the thermal medium, it still retains residual heat. For the purpose of energy conservation and emission reduction, this application embodiment also includes a step of recovering and recycling the residual heat in the cryogenic medium. Specifically, the cryogenic medium is heated and then returned to the primary dried product for secondary drying. During the heating process, the heat in the cryogenic medium increases. Using the heated cryogenic medium as a drying medium in the secondary drying process of the primary dried product effectively utilizes the heat of the cryogenic medium, reducing environmental pollution from its emissions. This heated cryogenic medium can also operate in parallel with the thermal medium, reducing the heat loss from the external environment when the initial medium is converted to a thermal medium, thus improving the operational stability of the drying method in the cryogenic region.

[0059] Furthermore, before returning the heated low-temperature medium to the primary dried product for secondary drying, a gas-solid separation process can be performed to reduce its contamination of the final product. This gas-solid separation process can be performed before or after the heating process, as long as it is completed before the secondary drying process.

[0060] As mentioned above, this application does not limit the product to be dried. When drying, the process parameters, including drying temperature and drying pressure, can be determined according to the chemical composition of different products to be dried.

[0061] In one specific embodiment, the product to be dried is polyoxymethylene (POM). When drying POM using the drying method of this application embodiment, the temperature of the heat medium is 142°C-148°C; the temperature of the intermediate heat medium before heat exchange treatment is not lower than 125°C, and the temperature of the intermediate heat medium after heat exchange treatment is not lower than 115°C.

[0062] In detail, by controlling the temperature of the heat transfer medium between 142℃ and 148℃, the solvent content of polyoxymethylene (POM) is minimized while ensuring that it does not undergo thermal degradation, thus guaranteeing the drying effect. Furthermore, to further ensure a reasonable and effective heat gradient transfer during the drying process, the temperature of the intermediate heat transfer medium is controlled to be no lower than 125℃ before exchanging heat with the initial medium, and no lower than 115℃ after the heat exchange treatment. This provides sufficient heat to the initial medium while maximizing the removal of most of the solvent from the product to be dried in the first-stage drying process, laying the foundation for the efficient second-stage drying process.

[0063] A second aspect of this application also provides a drying apparatus for performing the drying method of the first aspect described above.

[0064] Figure 1 This is a schematic diagram of the drying apparatus according to an embodiment of this application. Figure 1 As shown, the drying device includes a primary drying unit 1 and a secondary drying unit 2. The primary drying unit 1 includes a primary drying inlet 1a, a primary drying outlet 1b, a primary medium inlet 1c, and a primary medium outlet 1d. The secondary drying unit 2 includes a secondary drying inlet 2a, a secondary drying outlet 2b, a secondary medium inlet 2c, and a secondary medium outlet 2d. The primary drying outlet 1b and the secondary drying inlet 2a are connected, and the secondary medium outlet 2d and the primary medium inlet 1c are connected.

[0065] Specifically, the primary drying unit 1 is used to perform the aforementioned primary drying process. In the primary drying unit 1, the primary drying inlet 1a is used to input the product to be dried into the primary drying unit 1, the primary drying outlet 1b is used to output the primary dried product, the primary medium inlet 1c is used to input the intermediate heat medium into the primary drying unit 1, and the primary medium outlet 1d is used to output the low temperature medium.

[0066] The secondary drying unit 2 is used to perform the aforementioned secondary drying process. In the secondary drying unit 2, the secondary drying inlet 2a is connected to the primary drying outlet 1b and is used to receive the product to be dried. The secondary drying outlet 2b is used to output the final product. The secondary medium inlet 2c is used to input the heat medium into the secondary drying unit 2. The secondary medium outlet 2d is connected to the primary medium inlet 1c and is used to input the intermediate heat medium into the primary drying unit 1.

[0067] In the drying apparatus provided in this application embodiment, the heat medium first contacts the primary drying product in the secondary drying unit 2 to undergo secondary drying treatment. Subsequently, it cools down to become an intermediate heat medium, which then sequentially enters the primary drying unit 1 through the secondary medium outlet 2d and the primary medium inlet 1c, where it contacts the product to be dried to complete the primary drying treatment. The resulting primary dried product then sequentially enters the secondary drying unit 2 through the primary drying outlet 1b and the secondary drying inlet 2a. Thus, the drying apparatus of this application embodiment helps to achieve efficient utilization of heat in the heat medium, ultimately obtaining a high-quality final product.

[0068] This application does not limit the specific form of the primary drying unit 1 and the secondary drying unit 2. Exemplarily, the primary drying unit 1 and the secondary drying unit 2 can be any of the common airflow dryers, fluidized bed dryers, or rotary dryers in the art. Furthermore, the number of primary medium inlets 1c and secondary medium inlets 2c is not specifically limited; there can be one or more. When multiple inlets are included, they can be evenly distributed on the peripheral wall surfaces of the primary drying unit 1 and the secondary drying unit 2, thereby facilitating the dispersion and entry of the intermediate heat medium. In addition, to improve the efficiency of the primary and secondary drying processes, guide plates or porous distribution plates communicating with the primary medium inlets 1c and the secondary medium inlets 2c can be provided inside the primary drying unit 1 and the secondary drying unit 2.

[0069] Figure 2 This is another schematic diagram of the drying apparatus according to an embodiment of this application. Figure 2 As shown, the drying apparatus of this application embodiment further includes a heat exchange unit 3, which includes a low-temperature medium inlet 3a, a high-temperature medium outlet 3b, a heat exchange medium inlet 3c, and a heat exchange medium outlet 3d; the high-temperature medium outlet 3b is connected to the secondary medium inlet 2c, and the secondary medium outlet 2d is connected to the primary medium inlet 1c in sequence through the heat exchange medium inlet 3c and the heat exchange medium outlet 3d.

[0070] The heat exchange unit 3 is used for heat exchange treatment. The low temperature medium inlet 3a is used to receive the initial medium (e.g., room temperature air) from outside the interface. The high temperature medium outlet 3b is used to input the heat medium into the secondary drying unit 2 through the secondary medium inlet 2c. The heat exchange medium inlet 3c is used to receive the intermediate heat medium from the secondary medium outlet 2d. The heat exchange medium outlet 3d is used to input the intermediate heat medium after heat exchange treatment into the primary drying unit 1 through the primary medium inlet 1c.

[0071] By adding heat exchange unit 3, the heat carried by the intermediate heat medium can be deeply extracted and fully utilized, achieving efficient cascade recovery of heat energy and significantly reducing the heat demand from external heat sources. Therefore, the drying device of this application embodiment effectively optimizes the overall thermodynamic efficiency, thereby achieving the goal of reducing the energy consumption index of the drying method and controlling the drying operation cost.

[0072] For example, the heat exchange unit 3 described above can be a heat exchanger commonly used in the art.

[0073] Furthermore, the heat exchange unit 3 includes a first heat exchange subunit and a second heat exchange subunit; the first heat exchange subunit includes a first medium channel and a first heat exchange channel surrounding at least part of the outer surface of the first medium channel, the first medium channel including a low-temperature medium inlet 3a and an intermediate medium outlet; the second heat exchange subunit includes a second medium channel and a second heat exchange channel surrounding at least part of the outer surface of the second medium channel, the second medium channel including an intermediate medium inlet and a high-temperature medium outlet 3b; the intermediate medium outlet and the intermediate medium inlet are connected.

[0074] The first heat exchange channel includes a low-pressure steam inlet and a condensate outlet;

[0075] The inlet of the second heat exchange channel is the inlet of the heat exchange medium, and the outlet of the second heat exchange channel is the outlet of the heat exchange medium.

[0076] In detail, the heat exchange unit 3 has dual heat exchange medium channels. The initial medium enters the first medium channel through a low-temperature medium inlet 3a. The heat exchange medium (low-pressure steam) in the first heat exchange channel performs a first heat exchange treatment on the initial medium, raising its temperature to form an intermediate initial medium. This intermediate initial medium enters through the low-pressure steam inlet 3e of the first heat exchange channel and, after cooling (e.g., cooling to condensate), exits from the condensate outlet 3f of the first heat exchange channel. The intermediate initial medium sequentially enters the second medium channel through the intermediate medium outlet and intermediate medium inlet. The intermediate hot medium in the second heat exchange channel performs a second heat exchange treatment on the intermediate initial medium, ultimately raising its temperature to a hot medium, which then enters the secondary drying unit 2 through the high-temperature medium outlet 3b and the secondary medium inlet 2c. It can be understood that the inlet of the second heat exchange channel is the aforementioned heat exchange medium inlet 3c, and the outlet of the second heat exchange channel is the aforementioned heat exchange medium outlet 3d. For example, this heat exchange unit can be a two-way heat exchanger. The drying device in this embodiment can perform the method provided in the above-described method embodiments, and its implementation principle and technical effect are similar. Therefore, it will not be described in detail here.

[0077] Figure 3 This is another schematic diagram of the drying apparatus according to an embodiment of this application. Figure 3As shown, the drying apparatus of this application embodiment further includes a gas-solid separation unit 41, which includes a separation inlet 41a, a gas phase outlet 41b, and a solid phase outlet; the secondary medium outlet 2d is sequentially connected through the separation inlet 41a, the gas phase outlet 41b, and the heat exchange medium inlet 3c.

[0078] The gas-solid separation unit 41 is used to perform the aforementioned gas-solid separation process. The intermediate hot medium output from the secondary medium outlet 2d enters the gas-solid separation unit 41 through the separation inlet 41a for gas-solid separation. After gas-solid separation, the intermediate hot medium is output through the gas phase outlet 41b and enters the heat exchange unit 3 through the heat exchange medium inlet 3c. The separated solid particles are periodically discharged through the solid phase outlet. The drying device of this application embodiment can perform the method provided in the above method embodiment, and its implementation principle and technical effect are similar. It will not be described in detail here.

[0079] For example, the gas-solid separation unit 41 described above may be at least one of a cyclone separator and a bag filter.

[0080] Figure 4 This is another schematic diagram of the drying apparatus according to an embodiment of this application. Figure 4 As shown, the thermal drive unit 5 in this embodiment enables the heating of a low-temperature medium. Specifically, the thermal drive unit 5 includes a thermal drive inlet 5a and a thermal drive outlet 5b. The thermal drive inlet 5a is connected to the primary medium outlet 1d, and the thermal drive outlet 5b is connected to the secondary medium inlet 2c. The thermal drive inlet 5a receives the low-temperature medium from the primary medium outlet 1d of the primary drying unit 1, heats it, and then inputs it to the secondary drying unit 2 via the thermal drive outlet 5b and the secondary medium inlet 2c for secondary drying. The drying device in this embodiment can execute the method provided in the above-described method embodiments, and its implementation principle and technical effects are similar; therefore, further details are omitted here.

[0081] For example, the thermal drive unit 5 may be a thermal drive pump.

[0082] Furthermore, it also includes a gas-solid separation unit 42, whose heat-driven outlet 5a is connected to the secondary medium inlet 2c of the secondary drying unit 2 via the separation inlet 42a and the gas phase outlet 42b of the gas-solid separation unit 42. The gas-solid separation unit 42 can be selected from at least one of a cyclone separator and a bag filter.

[0083] A third aspect of this application also provides a production system, which includes a preparation device and a drying device of the second aspect; the crude product outlet of the preparation device and the primary drying inlet of the drying device are connected.

[0084] The preparation apparatus is used to prepare the product, for example, it can be an apparatus for preparing polyoxymethylene (POM) using formaldehyde or trioxymethylene as raw materials. The prepared POM is output through the crude product outlet of the preparation apparatus, and the POM output through the crude product outlet is the product to be dried. The product to be dried enters the primary drying unit of the drying apparatus through the primary drying inlet, and is dried in the drying apparatus according to the drying method described in the first aspect.

[0085] The production system of this application embodiment can integrate product preparation and drying, and can efficiently produce high-quality products, with more outstanding operational safety and reliability.

[0086] The production system of this application embodiment achieves deep integration and unified production of product preparation and drying. With its scientifically designed process, the system not only efficiently completes the product production process and produces high-quality products, but also demonstrates excellent safety and reliability during operation, providing a solid guarantee for stable product production.

[0087] Example 1

[0088] This embodiment adopts Figure 3 The apparatus shown is used to dry the polyoxymethylene product (with a moisture content of 20 wt%) to be dried according to the drying method of this application. The temperature of the heat medium (air) is 146°C, the temperature of the intermediate heat medium before the heat exchange treatment is 128°C, and the temperature of the intermediate heat medium after the heat exchange treatment is 118°C.

[0089] Ultimately, the moisture content of the final polyoxymethylene product in this embodiment is 0.1 wt%. Based on cost calculations, the drying method in this embodiment requires 320 kg of 6 kg of saturated steam (0.6 MPa, 159°C, used to heat air to obtain the heat medium) and 6.8 kW of electricity to dry each ton of polyoxymethylene product.

[0090] Comparative Example 1

[0091] Figure 5 This is a schematic diagram of a comparative drying apparatus according to this application. The drying method in this comparative example employs... Figure 5 The device shown is used for execution.

[0092] The polyoxymethylene product A to be dried (same as in Example 1) and the heat medium B (air) are respectively introduced into the first airflow dryer 100 for the first drying process to obtain intermediate polyoxymethylene product A1 (moisture content of 9wt%) and intermediate medium B1;

[0093] Intermediate medium B1 enters cyclone separator 200 for the first gas-solid separation, yielding low-solids-content intermediate medium B2. A portion of the low-solids-content intermediate medium B2 is compressed by steam compressor 201 to obtain compressed intermediate medium B3. The remaining low-solids-content intermediate medium B2 enters heat exchanger 202 and is heated by steam (6 kg of saturated steam (0.6 MPa, 159°C)) to become high-temperature intermediate medium B4. High-temperature intermediate medium B4 enters first airflow dryer 100 for the first drying process. A portion of the compressed intermediate medium B3 enters second airflow dryer 300, and the remaining compressed intermediate medium B3 enters heat exchanger 203 as a heating medium for heat exchange, where it is cooled into condensate.

[0094] Intermediate polyoxymethylene (POM) product A1 enters the second airflow dryer 300, where it undergoes a second drying process using compressed intermediate medium B3 to obtain final POM product A2 (moisture content 5 wt%). The compressed intermediate medium B3 is then cooled to a low-temperature intermediate medium B5. A portion of the low-temperature intermediate medium B5 is discharged, while the remaining B5 enters the cyclone separator 204 for gas-solid separation, yielding a low-solids-content low-temperature intermediate medium B6. This low-solids-content low-temperature intermediate medium B6 enters the heat exchanger 203 and is heated by the compressed intermediate medium B3, becoming a low-solids-content high-temperature intermediate medium B7. This high-temperature intermediate medium B7 then recirculates in the second airflow dryer 300 to participate in the second drying process, further drying the intermediate POM product A1.

[0095] After cost accounting, the comparative drying method requires 460 kg of 6 kg of saturated steam (0.6 MPa, 159°C, used to heat the air to obtain heat medium B and to provide heat in heat exchanger 202) and approximately 9 kW of electricity to dry each ton of polyoxymethylene product.

[0096] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A drying method, characterized in that, Includes the following steps: The product to be dried is subjected to a primary drying process using an intermediate heat medium to obtain the primary dried product and a low-temperature medium. The primary dried product is subjected to a secondary drying process using a heat medium to obtain the final product and the intermediate heat medium. The intermediate heat medium is returned to participate in the primary drying process.

2. The drying method according to claim 1, characterized in that, Before returning the intermediate heat medium to participate in the primary drying process, the process further includes: An intermediate heat medium is used to perform heat exchange treatment on the initial medium, and the initial medium is heated to become the heat medium.

3. The drying method according to claim 2, characterized in that, The heat exchange treatment includes: The initial medium is subjected to a first heat exchange treatment using low-pressure steam, and the initial medium is heated to become an intermediate initial medium; the intermediate initial medium is subjected to a second heat exchange treatment using the intermediate heat medium, and the intermediate initial medium is heated to become the heat medium.

4. The drying method according to claim 2 or 3, characterized in that, Prior to the heat exchange treatment, the process further includes: performing gas-solid separation treatment on the intermediate heat medium; and / or, After the low-temperature medium is heated, it is returned to the primary dried product for the secondary drying process.

5. The drying method according to any one of claims 2-4, characterized in that, The product to be dried is polyoxymethylene; The temperature of the heat medium is 142℃-148℃; The temperature of the intermediate heat medium before the heat exchange treatment is not lower than 125°C, and the temperature of the intermediate heat medium after the heat exchange treatment is not lower than 115°C.

6. A drying apparatus for performing the drying method according to any one of claims 1-5, characterized in that, It includes a primary drying unit and a secondary drying unit; the primary drying unit includes a primary drying inlet, a primary drying outlet, a primary media inlet, and a primary media outlet, and the secondary drying unit includes a secondary drying inlet, a secondary drying outlet, a secondary media inlet, and a secondary media outlet; The primary drying outlet and the secondary drying inlet are connected, and the secondary medium outlet and the primary medium inlet are connected.

7. The drying apparatus according to claim 6, characterized in that, It also includes a heat exchange unit, which includes a low-temperature medium inlet, a high-temperature medium outlet, a heat exchange medium inlet, and a heat exchange medium outlet; The high-temperature medium outlet and the secondary medium inlet are connected, and the secondary medium outlet is connected to the primary medium inlet in sequence through the heat exchange medium inlet and the heat exchange medium outlet.

8. The drying apparatus according to claim 7, characterized in that, The heat exchange unit includes a first heat exchange subunit and a second heat exchange subunit; the first heat exchange subunit includes a first medium channel and a first heat exchange channel surrounding at least a portion of the outer surface of the first medium channel, the first medium channel including the low temperature medium inlet and the intermediate medium outlet; The second heat exchange subunit includes a second medium channel and a second heat exchange channel surrounding at least a portion of the outer surface of the second medium channel. The second medium channel includes an intermediate medium inlet and a high-temperature medium outlet; the intermediate medium outlet and the intermediate medium inlet are connected. The first heat exchange channel includes a low-pressure steam inlet and a condensate outlet; The inlet of the second heat exchange channel is the inlet of the heat exchange medium, and the outlet of the second heat exchange channel is the outlet of the heat exchange medium.

9. The drying apparatus according to claim 7 or 8, characterized in that, It also includes a gas-solid separation unit, which includes a separation inlet, a gas phase outlet, and a solid phase outlet; the secondary medium outlet is sequentially connected to the separation inlet, the gas phase outlet, and the heat exchange medium inlet. And / or, It also includes a thermal drive unit, which includes a thermal drive inlet and a thermal drive outlet. The thermal drive inlet is connected to the primary medium outlet, and the thermal drive outlet is connected to the secondary medium inlet.

10. A production system, characterized in that, Includes a preparation apparatus and a drying apparatus as described in any one of claims 6-9; The crude product outlet of the preparation device is connected to the primary drying inlet of the drying device.

Images