Apparatus for supplying catalyst slurry to polymerization reactor
By using a catalyst mixing tank and a diluent mixing system, the problem of catalyst fragility during transportation was solved, achieving stable delivery of catalyst slurry and improving product quality, thus ensuring the efficient operation of the reactor.
Patent Information
- Application Number
- CN202520221169.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-12
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2035-02-12
AI Technical Summary
In polymerization reactors, catalysts are fragile during transport, leading to product quality and process operability issues, particularly increased fineness, altered molecular weight distribution, and reduced bulk density.
An apparatus was designed to mix catalyst and diluent via a catalyst mixing tank, providing a continuous catalyst slurry flow, and ensuring accurate assessment and control of catalyst slurry concentration through a loading unit and agitator, while optimizing the delivery process using a catalyst feed pump and a buffer container.
This achieved stable catalyst delivery, prevented catalyst damage, ensured product quality and process stability, and improved reactor operating efficiency.
Smart Images
Figure CN223915340U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a device, specifically for supplying catalyst slurry to a polymerization reactor. Background Technology
[0002] In a typical slurry polymerization reactor, monomer, diluent, and particulate catalyst are supplied to the reactor, where the monomer polymerizes. The diluent does not react, but the amount supplied to the reactor is typically used to control the solids concentration in the reactor and also provides a convenient mechanism for introducing particulate solid catalyst into the reactor. Also in typical gas-phase reactions, particulate catalyst is usually delivered to the reactor using an inert gas carrier; however, a typical inert diluent can also be used, where the amount introduced can be balanced with the requirements for gas-phase component control. In gas-phase reactions, the introduced inert diluent is typically introduced to optimize heat removal from the reaction system.
[0003] Catalysts are typically solid and fragile. In many processes, the quality of the produced product and the operability of the process depend on the particle size and particle size distribution of the (often fragile) catalyst. If the catalyst is damaged during its introduction into the process, it can have adverse effects on the process, such as increased fines level, altered molecular weight distribution, and decreased bulk density. Typically, the catalyst must be changed from a low-pressure (atmospheric or near-atmospheric) state to a high-pressure state to be able to enter the reactor (20-50 barg, but can be much larger). This usually needs to be done at a consistent, specific flow rate without damaging the catalyst (i.e., maintaining particle size without crushing it, etc.). Utility Model Content
[0004] We have developed a device that avoids many of the problems mentioned above by providing a system in which the catalyst mixing tank is supplied with catalyst and diluent in batches, but provides a continuous flow of catalyst slurry to the reactor, and allows for accurate assessment of both the catalyst slurry concentration in the mixing tank and the catalyst slurry concentration supplied to the reactor.
[0005] Therefore, in a first aspect, the present invention provides an apparatus for supplying a catalyst slurry to a polymerization reactor, the apparatus comprising:
[0006] (a) A catalyst day tank for receiving catalyst from a catalyst storage container, and the catalyst day tank having an outlet to allow the catalyst to flow out of the bottom;
[0007] (b) A load cell supported thereon or other device for determining the weight of the contents of the catalyst daily use tank;
[0008] (c) Catalyst feed tank (pot) having an inlet for receiving catalyst from the catalyst day tank, the catalyst feed tank also having a volume of 5 to 250 liters;
[0009] (d) A catalyst mixing tank having an inlet for catalyst from a catalyst feed cylinder and an inlet for a diluent, and the catalyst mixing tank having a capacity of at least 5m³. 3 A vertical cylindrical tank of volume, and also includes a stirrer for mixing the catalyst and diluent, and
[0010] (e) A reactor connected to a catalyst mixing tank. Attached Figure Description
[0011] Figure 1 The apparatus for supplying catalyst slurry to a polymerization reactor according to the present invention is shown schematically. Detailed Implementation
[0012] The containers and equipment used in the devices described above can be limited as follows:
[0013] Catalyst storage container (catalyst carrier) This container is located upstream of the catalyst storage tank and supplies the catalyst to it. The catalyst storage container is typically designed to handle the catalyst in the form it receives from the catalyst preparation unit. Therefore, it is adapted to the physical state of the catalyst upon arrival at the plant before feeding. In an embodiment, it may be a portable container in which the catalyst is transported to the plant.
[0014] Dry catalyst support This refers to the form of catalyst storage container suitable for catalysts in a dry state. Typically, it is a relatively simple container designed to have or allow overpressure of a dry inert gas (often nitrogen) to avoid atmospheric contamination of the catalyst. The container may have a conical bottom to facilitate the outflow of solid catalyst from the bottom.
[0015] Catalyst daily use canisterThe canister receives catalyst from a catalyst storage container and has an outlet to allow solid catalyst to drain from the bottom. The canister is often under a dry, inert gas overpressure (often nitrogen) to protect the catalyst from atmospheric contamination. Devices are provided for determining the weight of the contents of the catalyst day canister. In one embodiment, the canister is supported on a loading unit so that the canister and its contents can be weighed. In other embodiments, the catalyst day canister is provided with different devices for determining the weight of the contents. One example would be a level measurement device, which provides a value that can be converted into a weight measurement of the contents, such as using its density. The purpose of the catalyst day canister is to receive catalyst from a catalyst storage container and provide a feed of solid catalyst (e.g., gravity feed) into a feed cylinder, the amount of which can be determined by the weight difference of the contents before and after discharge. The catalyst day canister may have a conical bottom, but this is not necessary.
[0016] Catalyst feed cylinder The catalyst feed tank is a relatively small container. In this invention, its volume ranges from 5 to 250 liters, more commonly from 20 to 200 liters. A preferred volume within this range depends on the nature of the supplied catalyst, the production process, and the required productivity. The container preferably has a conical top and bottom. The conical bottom facilitates catalyst outflow from the tank. The conical top is designed to maximize the filling of solid catalyst.
[0017] Catalyst mixing tank The tank is a vertical cylindrical tank with an inlet for the catalyst from the catalyst feed cylinder and an inlet for the diluent. The tank also has a stirrer for mixing the catalyst and diluent. The stirrer is preferably designed to minimize mechanical impact on the catalyst. In this invention, the tank has a minimum diameter of 5 m. 3 The volume of the mixing tank is often less than 15 m³. 3 Preferably, the mixing tank has a volume of at least 7 m³. 3 For example, in 8 to 12 m 3 Within the range.
[0018] reactor The reactor can be any suitable reactor used for the polymerization of olefins. Examples include slurry-phase, solution-phase, and gas-phase reactors, such as slurry loop reactors, and gas-phase fluidized bed or stirred bed reactors.
[0019] The device may, and preferably includes, one or more of the following:
[0020] Buffer containerThis is a small, vertical cylindrical tank, typically with a conical bottom, and is provided / positioned between a catalyst mixing tank and a reactor. The tank may have pressure measuring devices and a level indicator. Its purpose is to mix the slurry from the mixing tank with additional (fresh or recycled) diluent, and then pump the resulting slurry to the reactor. A buffer vessel may be used optionally when using a catalyst feed pump.
[0021] Catalyst feed pump The pump is optional and can be used to pump the catalyst slurry into the reactor. (Alternatively, overpressure in the slurry tank can be used to push the catalyst into the reactor.) The catalyst feed pump (if present) can be a diaphragm pump with an inlet at the top and an outlet at the bottom. In a preferred alternative, the valves of any such pump must be spring-loaded to ensure they do not hang open when solid catalyst enters between the valve and the valve seat.
[0022] Essentially, the device consists of two systems that operate together to supply catalyst to the reactor: a batch catalyst refilling and dilution system for feeding the mixing tank, and a continuous catalyst slurry flow (optionally, and typically via a catalyst pump) from the mixing tank to the reactor.
[0023] There are several ways to operate the equipment, which typically involves batch refilling the catalyst mixing tank from the catalyst feed cylinder when the level (volume) of the catalyst slurry in the mixing tank is relatively low.
[0024] The initial slurry concentration in the mixing tank is known based on previously measured catalyst mass and diluent volume.
[0025] The catalyst is added to the mixing tank from the catalyst feed cylinder. The mass of the added catalyst is determined by the mass of the catalyst discharged from the catalyst feed cylinder (and specifically from the catalyst day tank) into the tank. Additional diluent is added via the diluent inlet to ensure that the catalyst concentration after refilling is the same as it was initially. More specifically, the concentration is updated during the steps of refilling the catalyst and diluting with additional diluent as follows.
[0026] - After catalyst refilling, the new mass of catalyst in the mixing tank is determined by directly measuring the mass of catalyst discharged into it and adding it to the mass of catalyst present in the mixing tank before refilling.
[0027] - Given the known volume of diluent in the tank, use this new mass to update the slurry concentration.
[0028] Then add the measured amount of diluent until the concentration is reduced to its initial level.
[0029] Once dilution is complete, the new catalyst slurry concentration is recorded for calculations regarding the next refill. In a preferred embodiment, the mass of the catalyst is measured before it is mixed with any diluent.
[0030] Another feasible approach is to provide a device for measuring the actual mass flow rate of the catalyst discharged into the reactor, for example, by measuring the density and mass flow rate leaving the mixing tank. This device may include, for example, a Coriolis flow meter. The instantaneous mass flow rate of the catalyst can be calculated by calculating the theoretical density of the diluent at the temperature and pressure in the mixing tank and comparing it with the slurry density measured in the flow meter. While this invention is particularly suitable for slurry polymerization reactions, it can also be used for gas-phase polymerization, in which case the amount of fresh diluent used is typically much smaller, but the principle of the invention remains unchanged.
[0031] When it is necessary to minimize the amount of fresh diluent used in this process for efficiency and / or quality balance requirements, it is feasible to use comonomers recovered from the reaction loop or degassing system of the polymerization reactor, or monomer-depleted recycled condensable material, as diluent supplementation. The main limitation of this use is to avoid any fouling caused by catalyst polymerization. This recycled stream has also been found suitable for assisting in conveying the diluted catalyst stream to the reactor after it leaves the mixing tank.
[0032] The refilling of the catalyst mixing tank can be specifically performed as follows:
[0033] Preparation of daily-use containers The solid (dry) catalyst is introduced into a dry catalyst storage container. The catalyst storage container is connected to a catalyst day tank. The catalyst is pneumatically transferred to the day tank (which is often higher than the storage container). During the pneumatic transfer, care must be taken to use low pressure and low flow rate, otherwise the catalyst may be damaged. Once the transfer is complete, the catalyst storage container is disconnected and removed to the catalyst preparation area. The weight of the contents of the catalyst day tank is determined and recorded. The day tank is under a slight overpressure of dry inert gas (approximately 4 barg of nitrogen, but the pressure can vary significantly).
[0034] When operating with a dry catalyst, the mixing tank has two different refill and dilution modes: the so-called "dry / dry" and "dry / wet".
[0035] Dry / Dry ModeIn this operating mode, the catalyst begins in the catalyst day tank under approximately 4.0 barg of nitrogen. From here, the catalyst feed cylinder is refilled with dry catalyst, the weight of which is determined by the weight change of the contents of the catalyst day tank, and is typically pneumatically conveyed to the mixing tank using nitrogen purging. The measured volume of diluent is then added directly to the mixing tank. The advantage of the dry / dry mode is that the refilling of the catalyst feed cylinder is generally excellent because the catalyst is always dry; and it is theoretically optimal for valve life. A potential disadvantage is that the catalyst is not properly wetted in the mixing tank and may form lumps during pneumatic conveying or may be blown out from the nitrogen vent of the mixing tank.
[0036] Dry / Wet Mode In this operating mode, a weighed amount of dry catalyst is discharged into the catalyst feed tank, as in the dry / dry mode, but then the catalyst is wetted with a small amount of diluent, which is added slowly, preferably from the bottom of the feed tank. The wetted catalyst is then rinsed into the mixing tank using the measured amount of diluent. All the diluent added to the mixing tank can be used for rinsing, or some of the diluent can be added directly to the mixing tank (and its quantity is also measured), in which case both lots of diluent are used for concentration calculation. The advantage of the dry / wet mode is that the catalyst is wetted in a slow and controlled manner. A potential disadvantage of this operating mode is that the catalyst feed tank may not be properly refilled, as the liquid diluent can cause the catalyst to stick or fluidize during refilling.
[0037] Mixing tank mass balance and catalyst flow control To maintain a consistent catalyst feed to the reactor, a continuous mass balance of catalyst and diluent is calculated in the mixing tank. This mass balance is used to calculate the slurry concentration (g / L) in the mixing tank, and this concentration is used to adjust the catalyst flow rate so that a constant catalyst flow rate to the reactor is maintained even during dilution of the mixing tank with additional diluent.
[0038] There are two aspects to mass balance: the amount of catalyst and the amount of diluent. The diluent volume can be determined by measuring the slurry level in the mixing tank. The volume of catalyst in the slurry is ignored. (The diluent volume can also be determined by totaling the diluent flow rate during dilution and subtracting the catalyst slurry flow rate leaving the mixing tank since the last refill.) As described above, the method used to determine catalyst mass is to check the actual weight of catalyst entering the catalyst feed tank by measuring the weight loss in the catalyst day tank. The weight loss in the catalyst day tank during catalyst feed tank filling represents the amount of catalyst that will ultimately be injected into the catalyst mixing tank during refilling. This enables a true mass balance system for the catalyst.
[0039] Calculation of slurry concentration in mixing tank As an example, if the mixing tank is refilled at 50% level, the calculation is as follows.
[0040] First, determine the volume of diluent and the mass of catalyst in the vessel before refilling. Then, using the diluent volume in the catalyst mixing tank, calculate the mass of catalyst in the mixing tank using the current slurry concentration. For example, if the mixing tank contains 3 m³ of diluent before refilling... 3 slurry (6 m 3 If the mixing tank is filled to 50% capacity and the slurry concentration is 3 g / L, then the mass of the catalyst before refilling will be: 3 m 3 *(1000 l / m 3 )*3 g / l = There is 9000 g of catalyst in the mixing tank.
[0041] Record both the initial volume and the initial catalyst mass.
[0042] Once catalyst refilling begins, determine the mass of catalyst injected into the mixing tank as mentioned above, and add this amount to the mass of catalyst calculated above that was present prior to refilling. For example, 1800g of catalyst may be added. The weight of the catalyst is verified by the weight loss of the catalyst day tank during refilling.
[0043] In this case, the total mass of the catalyst in the mixing tank is: 1800 g injected + 9000 g existing mass = 10800 g.
[0044] Then, use this new mass to continuously update the slurry concentration until the concentration is significantly higher than the set point by 3 g / L after adding diluent.
[0045] 10800 g catalyst / 3000 l diluent = 3.6 g / l catalyst slurry concentration.
[0046] The dilution of the slurry in the mixing tank begins and continues until the catalyst concentration reaches its set point. In this case, if the catalyst concentration set point is 3 g / L, the diluent will be refilled until the total volume of the slurry in the mixing tank is 3600 liters: (10800 / 3600 = 3 g / L).
[0047] This example corresponds to filling to 60% of the total volume of the mixing tank. It will be apparent that larger fills can be obtained by repeating the above steps or by adding a larger amount of catalyst followed by a correspondingly larger amount of diluent. Preferably, each single fill is performed with at least 15 minutes between each subsequent fill. Typically, fills may be repeated no more than three times per hour and no less than once every three hours, but the specific frequency will depend on the nature of the catalyst and the slurry used. (And often, fills will be repeated at a frequency between 50% and 10% of the average residence time.)
[0048] Once refilling is complete, the catalyst slurry concentration is stored in a register for calculations during the next refill.
[0049] Note that in this scenario, it is assumed that refilling is relatively rapid, and the fact that some of the slurry in the mixing tank is discharged into the reactor during the refilling operation is ignored. (If necessary, the discharge of catalyst slurry from the mixing tank can be paused during this operation. For example, if a buffer vessel, as further described below, is present, the volume of catalyst slurry present therein can be used to supply catalyst to the reactor during the refilling of the mixing tank described above.)
[0050] It should also be noted that although the catalyst is added first and then diluted in this example, the reverse is also possible. It will be seen that the amount of diluent to be added can be calculated immediately once the existing slurry concentration and the mass of catalyst in the feed tank (both of which will be added to the mixing tank) are known.
[0051] Continuous catalyst feeding from catalyst mixing tank to reactor The catalyst is preferably continuously supplied (discharged) from the mixing tank to the reactor. This part of the process has the following characteristics, and is the same for all types of catalysts and refill / dilution modes:
[0052] • Flow control of the catalyst slurry flowing out of the mixing tank via a control valve
[0053] • (Optional) Add catalyst diluent (typically before the optional catalyst pump). This improves the flow properties of the catalyst in the pipeline leading to the reactor and reduces the likelihood of catalyst damage in the (optional) catalyst feed pump.
[0054] • (Optional, if the mixing tank pressure is lower than the reactor pressure) Pumping of diluted catalyst slurry, preferably using a vertically oriented diaphragm pump, preferably having an intake valve at the top and an exhaust valve at the bottom.
[0055] As shown above, the slurry concentration is temporarily changed during the refilling of the mixing tank until both the catalyst and diluent are fully refilled. It is noted above that the discharge of catalyst slurry from the mixing vessel can be suspended during refilling. However, continued discharge during refilling is also feasible.
[0056] When the catalyst is added first, the concentration will rise briefly and then fall back to the set level once the diluent has been added. Because the concentration can be accurately calculated, the flow rate control of the slurry flowing from the mixing tank to the reactor can be temporarily adjusted to maintain a constant mass flow rate of catalyst to the reactor. Therefore, when the catalyst is added to the mixing tank first, the rise in the mixing tank concentration is compensated by a corresponding decrease in the flow rate from the mixing tank, so that the mass of catalyst delivered to the reactor remains constant. The extent of this change depends on the relative dimensions of the various components of the system; however, even when relatively large changes in slurry concentration occur in the catalyst mixing tank (e.g., an increase in slurry concentration of up to 30%), the accurate knowledge of the actual slurry concentration provided by this invention allows for satisfactory control of the actual catalyst flow rate to the polymerization reactor.
[0057] One advantage of maintaining a constant catalyst mass flow rate to the reactor is that the proportion of slurry renewed during each refill in the mixing tank can be significant. This proportion depends in part on the working concentration of the slurry in the mixing tank and also on the maximum possible peak concentration during refill. These, in turn, vary depending on catalyst properties such as bulk density, particle density, diluent density, the interaction between the agitator and the slurry (excessive concentration requires excessive agitator power, which can lead to catalyst damage), and the fragility of the catalyst particles. Another limiting factor is the minimum controllable flow rate that can be reliably delivered to the reactor through the control valve at the outlet of the mixing tank. If the peak slurry concentration during refill is too high, the agitator may struggle to adequately distribute the catalyst through the slurry.
[0058] The device is schematically displayed Figure 1 middle, Figure 1 An apparatus is shown comprising a catalyst day tank (1) for receiving catalyst from a catalyst storage container (2). In this specific example, the catalyst day tank (1) is supported on a load unit (3) which provides means for determining the weight of the contents. Figure 1 Also shown are a catalyst feed tank (4) and a catalyst mixing tank (5), the catalyst mixing tank (5) having an inlet (6) for the catalyst from the catalyst feed tank (5) and an inlet (7) for the diluent. The catalyst mixing tank (5) is connected to a reactor (8) (not shown).
Claims
1. An apparatus for supplying catalyst slurry to a polymerization reactor, characterized by, The apparatus comprises: (a) a catalyst day tank for receiving catalyst from a catalyst storage vessel and having an outlet to allow catalyst to flow out the bottom; (b) a load cell or other means for determining the weight of the contents of the catalyst day tank on which the catalyst day tank is supported; (c) a catalyst feed cylinder having an inlet for receiving catalyst from the catalyst day tank, the catalyst feed cylinder further having a volume of 5 to 250 liters; (d) a catalyst mixing tank having an inlet for catalyst from the catalyst feed cylinder and an inlet for diluent, and the catalyst mixing tank is a vertical cylindrical tank having at least 5 m 3 volume, and further comprising an agitator for mixing catalyst and diluent, and (d) a catalyst mixing tank having an inlet for catalyst from the catalyst feed cylinder and an inlet for diluent, and the catalyst mixing tank is a vertical cylindrical tank having at least 5 m 3 volume, and further comprising an agitator for mixing catalyst and diluent, and (e) a reactor connected to the catalyst mixing tank.
2. The apparatus of claim 1, wherein, The apparatus further comprises a surge vessel between the catalyst mixing tank and the reactor, the surge vessel having an inlet for catalyst from the catalyst mixing tank and an inlet for diluent, and the surge vessel is a vertical cylindrical tank having a conical bottom, a pressure measuring device, and a level indicator.
3. The apparatus of claim 2, wherein, The apparatus further comprises a catalyst feed pump after the surge vessel and before the polymerization reactor.
4. The apparatus of claim 3, wherein, The catalyst feed pump is a diaphragm pump having a suction inlet on the top and a discharge outlet on the bottom.