A microchannel catalyst metering and delivery system

Abstract

The present invention provides a microchannel catalyst metering and conveying system, which comprises a catalyst unit, which is sequentially connected to a feed metering unit and a conveying unit; the feed metering unit comprises a pipe resistance module, and the outlet of the catalyst unit is connected to the inlet of the pipe resistance module. The system achieves precise control of feed by enlarging the pressure regulation range and reducing feed flow fluctuation.

Description

Technical Field

[0001] The invention belongs to the field of polymerization technology and relates to a microchannel catalyst metering and conveying system. Background Art

[0002] At present, most of the catalysts used in industrial polymerization reactions are solid particles. There are usually two ways to add solid catalysts. One is to add directly with a specially designed complex catalyst feeding device, such as the solid catalyst feeding device used in the Unipol polyethylene process unit; the other is to prepare the catalyst into a slurry of a certain concentration or heat it to melt through a complex process, and then feed it into the reactor with a complex metering feeding system. For the above two methods, the equipment investment for the former is very high, and there is no accurate and effective way to know the catalyst inventory in the feeder. The operation process of the latter is extremely complicated, and it is transported by a metering pump, which is easy to cause flow fluctuations and uneven feeding, which affects the reaction.

[0003] Catalysts are usually highly active and require to be added to the polymerization reactor at a very stable and precisely controlled minimum flow rate. Otherwise, the polymerization reaction will be unstable, resulting in product quality fluctuations or agglomeration in the reactor. Therefore, the key problem to be solved in the actual application of this type of catalyst is how to add it evenly and accurately to the polymerization system.

[0004] For example, the polycarbonate process requires that the catalyst be continuously and stably added to the reactor at a very small flow rate with precise control, otherwise the reaction will be unstable and result in fluctuations in product quality.

[0005] For example, CN1927440A discloses a slurry feeding device, which includes a slurry catalyst tank, a delivery pump, at least one six-way valve and a metering tube. When feeding is required, the position of the six-way valve is changed once, and the catalyst in the metering tube is absorbed into the polymerization reaction system. The feeding of slurry or liquid catalyst is achieved by operating the six-way valve. However, the invention still uses a metering pump for delivery. Even if the pump outlet is equipped with a pulse damper, the pulse fluctuation cannot be ignored in the case of small flow delivery, which will still affect the accuracy of feeding and further affect the stability of the reaction. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a microchannel catalyst metering and delivery system, which can achieve precise control of feed by enlarging the pressure regulation range and reducing feed flow fluctuation.

[0007] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0008] The present invention provides a microchannel catalyst metering and conveying system, which comprises a catalyst unit, wherein the catalyst unit is sequentially connected to a feed metering unit and a conveying unit;

[0009] The feed metering unit comprises a pipe resistance module, and the outlet of the catalyst unit is connected to the inlet of the pipe resistance module.

[0010] As a preferred technical solution of the present invention, the pipe resistance module is composed of at least one section of bent pipe, and each section of the bent pipe is detachably connected.

[0011] As a preferred technical solution of the present invention, the ratio of the total length L of each section of the elbow to the inner diameter D of the elbow is L / D=10 to 100. The value of L / D can be 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100, etc.

[0012] As a preferred technical solution of the present invention, the ratio of the radius of curvature r of each section of the curved pipe to the inner diameter D of the curved pipe is r / D=1.5 to 5. The value of r / D can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, etc.

[0013] As a preferred technical solution of the present invention, the pressure drop of the pipe resistance module accounts for 50-95% of the total pressure drop of the feed metering unit, and can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, etc.

[0014] As a preferred technical solution of the present invention, the feed metering unit also includes a flow meter.

[0015] As a preferred technical solution of the present invention, the delivery unit includes a venturi tube, and the venturi tube is connected to the outlet of the catalyst unit.

[0016] As a preferred technical solution of the present invention, the catalyst unit is provided with a gas inlet for adjusting the feed pressure by gas.

[0017] As a preferred technical solution of the present invention, the microchannel catalyst metering and delivery system further includes a monomer distribution unit, and the outlet of the monomer distribution unit is connected to the venturi tube.

[0018] As a preferred technical solution of the present invention, the feeding direction of the monomer distribution unit is parallel to the Venturi tube, and the feeding direction of the feed metering unit is perpendicular to the Venturi tube.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] (1) The present invention provides a microchannel catalyst metering and delivery system, which uses a pipe resistance module to enlarge the pressure control range and achieve precise control of feed flow, and is suitable for various small flow conditions.

[0021] (2) The present invention provides a microchannel catalyst metering and delivery system, which does not require the use of a metering pump and has no risk of flow pulse fluctuations.

[0022] (3) The present invention provides a microchannel catalyst metering and delivery system, which uses pressure to control the extraction flow rate. Since the venturi tube is under negative pressure, the nitrogen pressure of the catalyst tank is the nitrogen sealing pressure under normal working conditions to meet the working requirements. The process control is simple and the pressure regulation is accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a microchannel catalyst metering and delivery system provided in Example 1 of the present invention;

[0024] Figure 2 A schematic structural diagram of a detachable elbow group in a microchannel catalyst metering and delivery system provided in Example 1 of the present invention;

[0025] Figure 3 A schematic structural diagram of a catalyst metering and delivery system provided in Comparative Example 1 of the present invention;

[0026] Figure 4 A schematic diagram of the structure of a catalyst metering and delivery system provided in Comparative Example 2 of the present invention;

[0027] Figure 5 It is a feed flow fluctuation diagram of application example 1 of the present invention and comparative application example 3;

[0028] Figure 6 It is a feed flow fluctuation diagram of Application Example 1 of the present invention and Comparative Application Example 4;

[0029] In the figure: V-01 / V-02 is a catalyst tank; R-01 / R-02 is a reactor; L-01 is a pipe resistance module; Z-01 is a venturi tube; P-02 is a metering pump.

[0030] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below through specific implementation methods.

[0032] The specific embodiment of the present invention provides a microchannel catalyst metering and conveying system, which includes a catalyst unit, which is sequentially connected to a feed metering unit and a conveying unit;

[0033] The feed metering unit comprises a pipe resistance module, and the outlet of the catalyst unit is connected to the inlet of the pipe resistance module.

[0034] The conventional catalyst metering and delivery means is that after the solid (liquid) catalyst is configured by adding a certain amount of solvent, it is delivered to the reactor through a metering pump. However, in the present invention, the pressure regulation range of the catalyst tank is enlarged by the pipe resistance module. When the operating conditions change, the pressure of the catalyst tank can have a wide adjustment range. According to the Bernoulli equation, after the medium passes through the pipe resistance module, the greater the flow rate, the greater the overall pressure drop of the pipe resistance module, and thus the pressure variation range of the catalyst unit will be wider. The enlarged pressure range can achieve accurate control of the catalyst extraction after the pipe resistance module, achieving the purpose of high-precision flow control. At the same time, since the system does not use a metering pump, the stable extraction of the catalyst can also be achieved simultaneously without the phenomenon of flow fluctuation.

[0035] In a specific embodiment of the present invention, the pipe resistance module is composed of at least one section of curved pipe, and each section of the curved pipe is detachably connected. The number of sections of the curved pipe in the pipe resistance module can be 1 section, 2 sections, 3 sections, 4 sections, 5 sections, 6 sections, 7 sections, 8 sections, 9 sections, 10 sections, 15 sections or 20 sections, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The number of sections of the curved pipe in the pipe resistance module can be selected according to the feed flow rate and pressure drop requirements, and the detachable connection facilitates adjustment. The average length of each section of the curved pipe is equal and can be used as a backup for each other.

[0036] In a specific embodiment of the present invention, the inner wall of the pipe resistance module, that is, the inner wall of each section of the elbow pipe should be polished to Ra≤0.4 μm to prevent the accumulation of media and the formation of dead zones, which may cause pipe blockage.

[0037] In a specific embodiment of the present invention, no pipe fittings are provided in the entire catalyst delivery pipeline (including the pipe resistance module), and equal-diameter pipes are used to strengthen the square relationship between pressure drop and flow velocity, which is beneficial for adjustment.

[0038] In a specific embodiment of the present invention, the ratio of the total length L of each section of the elbow to the inner diameter D of the elbow is L / D=10~100, such as 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In a specific embodiment of the present invention, the ratio of the radius of curvature r of each section of the curved pipe to the inner diameter D of the curved pipe is r / D=1.5~5, such as 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In a specific embodiment of the present invention, all the delivery pipelines of the system require a stable pressure drop change. In order to avoid the eddy current caused by the sudden increase of the reducer or the diameter of the pipe, the elbows required on the pipeline do not use conventional 90° elbows, but use more gentle elbows (preferably with a bending radius of 5 times the diameter of the elbow). This ensures that the pressure change of the entire pipe resistance is continuous and stable, which is beneficial for the operation of pressure control flow.

[0041] In a specific embodiment of the present invention, the pressure drop of the pipe resistance module accounts for 50-95% of the total pressure drop of the feed metering unit, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, etc., and is not limited to the listed values. Other values ​​not listed in the numerical range are also applicable. It is helpful to adjust the square relationship between the pressure drop and the flow rate. The pipe resistance pressure drop can be calculated by the pressure measurement point on the pipeline.

[0042] In one embodiment of the present invention, the feed metering unit further comprises a flow meter to adjust the pressure of the catalyst unit by setting different flow rates.

[0043] In one specific embodiment of the present invention, the delivery unit includes a venturi tube, which is connected to the outlet of the catalyst unit. The venturi tube is a throttling flow sensor developed based on the venturi effect, and is also a standard throttling device. Its working principle is based on the venturi effect, that is, when a fluid (gas or liquid) flows through a gradually shrinking pipe, the flow rate will increase, and the static pressure will decrease, thereby generating a pressure difference between the inlet and outlet of the pipe. This pressure difference is proportional to the flow rate of the fluid, so the flow rate of the fluid can be measured by measuring the pressure difference.

[0044] In one embodiment of the present invention, the catalyst unit is provided with a gas inlet for adjusting the feed pressure by gas, and the gas is preferably nitrogen.

[0045] In a specific embodiment of the present invention, the pressure of the catalyst unit is preferably controlled at 0.01~0.1MPaG, and more preferably controlled at 0.02~0.05MPaG. In the process flow, since the catalyst unit (catalyst tank) is generally nitrogen-sealed and the pressure is not too high, when the pipe resistance module is set, its pressure share in the pipeline is magnified. Therefore, the change of the nitrogen sealing pressure of the catalyst tank can adjust the flow rate in a large range and achieve precise control.

[0046] In a specific embodiment of the present invention, in the catalyst unit, a PIC pressure control module is provided on the top of the catalyst tank, and the catalyst extraction amount is adjusted by controlling the nitrogen feed pressure.

[0047] In a specific embodiment of the present invention, the microchannel catalyst metering and delivery system further includes a monomer distribution unit, and the outlet of the monomer distribution unit is connected to the venturi tube.

[0048] In a specific embodiment of the present invention, the feeding direction of the monomer distribution unit is parallel to the venturi tube, and the feeding direction of the feed metering unit is perpendicular to the venturi tube.

[0049] In a specific embodiment of the present invention, in the delivery unit, the catalyst feed point is the diameter change point of the venturi tube, and after being mixed with the monomer (or solvent) passing through at a high flow rate, it is delivered to the reactor.

[0050] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0051] Example 1

[0052] This embodiment provides a microchannel catalyst metering and delivery system, the structure of which is as follows: Figure 1 As shown, the microchannel catalyst metering and conveying system includes a catalyst unit, which is sequentially connected to a feed metering unit and a conveying unit;

[0053] The catalyst unit includes a catalyst tank V-01, which is provided with a catalyst inlet and a gas inlet, the gas inlet is connected to a nitrogen inlet pipeline, a PIC pressure control module is provided on the nitrogen inlet pipeline, and the outlet of the catalyst tank V-01 is connected to the inlet of the pipe resistance module L-01;

[0054] The pipe resistance module L-01 includes two detachable elbow groups (the detachable elbow group structure is as follows Figure 2 As shown in the figure, the starting end of the first detachable elbow group and the tail end of the second detachable elbow group are provided with a pressure gauge PC, and the connection between the pipe resistance module L-01 and the feed metering unit is provided with a flow meter FIC; the pipe connection in the pipe resistance module L-01 adopts an elbow, and the bending radius of the elbow is 5 times the diameter of the elbow;

[0055] The feed metering unit includes a venturi tube Z-01, the outlet of the pipe resistance module L-01 is connected to the reduced diameter of the venturi tube Z-01, and the feed direction is perpendicular to the venturi tube Z-01. A pressure gauge PC is provided on the pipeline at the connection between the pipe resistance module L-01 and the venturi tube Z-01;

[0056] The microchannel catalyst metering and delivery system also includes a monomer distribution unit, the outlet of the monomer distribution unit is connected to the venturi tube, and the feed direction is parallel to the venturi tube, and the outlet of the venturi tube Z-01 is connected to the material inlet of the reactor R-01.

[0057] Application Examples 1-5 and Comparative Application Examples 1-2 use the microchannel catalyst metering and delivery system provided in Example 1 for feeding, and monitor the flow stability. The conditions and flow stability are shown in Table 1.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, from Application Example 1 to Application Example 2, the flow rate increases by 100%, that is, the change from 1L / hr to 2L / hr, and the pressure control value increases by 4.69kPa. Obviously, the increased pressure difference is very easy to achieve for daily operations. When the flow rate continues to increase to 3L / hr (Application Example 3), the number of groups of pipe resistance modules is reduced, and the pressure is adjusted appropriately, and a stable flow rate and a precise control method can still be obtained. On the contrary, in Comparative Application Examples 1 and 2 that exceed the scope of the claims of the present invention, it can be seen that the pressure from Comparative Application Example 1 to Comparative Application Example 2 only increases by 0.77kPaG, but the flow rate increases by 4L / hr, which is not suitable for precise regulation of small flow rates. Therefore, if the scope of the claims of the present invention is not met, it is very difficult to operate the flow rate to obtain more precise control.

[0061] Comparative Example 1

[0062] This comparative example provides a microchannel catalyst metering and delivery system. The system has the same structure as Example 1 except that the pipe connection in the pipe resistance module L-01 uses a right-angle elbow. Figure 3 shown.

[0063] Comparative Application Example 3

[0064] This comparative application example adopts the microchannel catalyst metering and delivery system provided in comparative example 1. The conditions of application example 1 are used for feeding. The flow rate of the catalyst is relatively stable as a whole, but there are still some fluctuations compared with application example 1. The flow fluctuations of application example 1 and comparative application example 3 are as follows: Figure 5 shown. Figure 5 In the figure, flow 1 represents the flow fluctuation of application example 1, and flow 2 represents the flow fluctuation of comparative application example 3.

[0065] Comparative Example 2

[0066] This comparative example provides a microchannel catalyst metering and delivery system. The system has the same structure as Example 1 except that the pipe resistance module L-01 is replaced by a metering pump P-02, and the elbow in the connecting pipeline between the metering pump P-02, the catalyst tank V-02 and the reactor R-02 is a right-angle elbow. Figure 4 shown.

[0067] Comparative Application Example 4

[0068] This comparative application example adopts the microchannel catalyst metering and delivery system provided in comparative example 2. It adopts the conditions of application example 1 for feeding. The flow rate of the catalyst still fluctuates and the extraction volume cannot be accurately controlled. The flow fluctuations of application example 1 and comparative application example 4 are as follows: Figure 6 shown. Figure 6 , flow 1 represents the flow fluctuation of application example 1, and flow 3 represents the flow fluctuation of comparative application example 4.

[0069] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0070] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0071] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0072] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A microchannel catalyst metering and delivery system, characterized in that: The microchannel catalyst metering and conveying system comprises a catalyst unit, which is sequentially connected to a feed metering unit and a conveying unit; The feed metering unit includes a pipe resistance module, and the outlet of the catalyst unit is connected to the inlet of the pipe resistance module; The pressure drop of the pipe resistance module accounts for 50-95% of the total pressure drop of the feed metering unit; The catalyst unit is provided with a gas inlet for adjusting the feed pressure by gas.

2. The microchannel catalyst metering and delivery system according to claim 1, characterized in that: The pipe resistance module is composed of at least one section of bent pipe, and each section of the bent pipe is detachably connected.

3. The microchannel catalyst metering and delivery system according to claim 2, characterized in that: The ratio of the total length L of each section of the curved pipe to the inner diameter D of the curved pipe is L / D=10~100.

4. The microchannel catalyst metering and delivery system according to claim 2, characterized in that: The ratio of the curvature radius r of each section of the curved pipe to the inner diameter D of the curved pipe is r / D=1.5~5.

5. The microchannel catalyst metering and delivery system according to claim 1, characterized in that: The feed metering unit further comprises a flow meter.

6. The microchannel catalyst metering and delivery system according to claim 1, characterized in that: The delivery unit includes a venturi tube, and the venturi tube is connected to the outlet of the catalyst unit.

7. The microchannel catalyst metering and delivery system according to claim 1, characterized in that: The microchannel catalyst metering and delivery system further comprises a monomer distribution unit, and an outlet of the monomer distribution unit is connected to a venturi tube.

8. The microchannel catalyst metering and delivery system according to claim 7, characterized in that: The feeding direction of the monomer distribution unit is parallel to the Venturi tube, and the feeding direction of the feed metering unit is perpendicular to the Venturi tube.

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