Hydrogenation device for polypropylene production

Abstract

The utility model relates to the technical field of hydrogenation devices for polypropylene production in the petrochemical industry, in particular to a hydrogenation device for polypropylene production, which comprises a plurality of polymerization kettles, a hydrogenation valve II, a plurality of hydrogen metering tanks and a hydrogen supplementing valve, the hydrogen metering tank is used for storing hydrogen, the hydrogen metering tank is communicated with a plurality of hydrogen supplementing valves, and the device has the effects that hydrogenation operation can be carried out at proper pressure in the hydrogenation process, and the speed and the amount of conveyed hydrogen can be controlled.

Description

Technical Field

[0001] The utility model relates to the technical field of hydrogenation devices used in the production of polypropylene in the petrochemical industry, in particular to a hydrogenation device used in the production of polypropylene. Background Art

[0002] Based on the propylene polymerization reaction mechanism, chain transfer agents can be used to control the molecular weight of the polymer by controlling the molecular weight. This chain transfer agent, or molecular weight regulator, is hydrogen. The melt flow index (MFI) of polypropylene products is a key indicator of their molecular weight, so the correct amount of hydrogen added is directly related to the MFI.

[0003] In the current intermittent bulk polypropylene production process, there are two main hydrogenation methods: mass method and volumetric method. The core measurement method of the former is the use of mass flow meter, while the latter usually uses 40L hydrogen cylinders as the hydrogen source.

[0004] (1) Generally speaking, for 12m 3 For a typical polymerization reactor, producing a material with a melting point range of 3-5g / 10min requires about half a bottle of hydrogen, while producing a material with a melting point range of 20-30g / 10min may require three bottles of hydrogen. This means that the operator needs to install and remove the cylinder three times to complete the hydrogenation process, which is a rather cumbersome process.

[0005] (2) Taking the production of materials with a melt index range of 20-30g / 10min as an example, the hydrogen cylinder has a capacity of only 40L, so it is necessary to record the starting pressure and the ending pressure of each cylinder change, and then add the pressure difference values to get the actual pressure drop of hydrogen added. Since hydrogen molecules are small and have strong permeability, it is difficult to ensure an extremely strict sealing state during actual production operations. During the disassembly and assembly process, there will be obvious hydrogen leakage. Therefore, the hydrogen pressure drop obtained in this way is a very rough value, which causes the actual amount of hydrogen added each time to fluctuate. Of course, the melt index of the product can only be a very wide range, which makes it difficult to achieve precise production and inaccurate measurement.

[0006] (3) From the ideal gas state equation, it can be seen that the temperature T of hydrogen is a variable. The temperature will vary significantly with different seasons, climate changes, and even whether the hydrogen cylinder is directly exposed to sunlight during hydrogenation. If the environmental factors of the hydrogenation process are excluded, the influence of environmental factors will not be conducive to accurate measurement. Utility Model Content

[0007] (1) Technical problems solved

[0008] In view of the shortcomings of the existing technology, the utility model provides a hydrogenation device for polypropylene production, which can perform hydrogenation at a more appropriate pressure during the hydrogenation process, which is beneficial to controlling the rate and amount of hydrogen delivery.

[0009] (2) Technical solution

[0010] To achieve the above-mentioned purpose, the utility model provides the following technical solution: a hydrogenation device for polypropylene production, comprising a polymerization kettle, a second hydrogenation valve, a hydrogen metering tank and a hydrogen replenishing valve, wherein several polymerization kettles and several hydrogen metering tanks are connected by pipelines, and a second hydrogenation valve is installed on the pipeline connecting the polymerization kettle and the hydrogen metering tank. The hydrogen metering tank is used to store hydrogen, and the hydrogen metering tank is connected to several hydrogen replenishing valves.

[0011] Preferably, the hydrogen metering tank is made of stainless steel.

[0012] Preferably, a temperature transmitter is included, and the hydrogen metering tank is installed with a temperature transmitter for detecting the internal temperature of the hydrogen metering tank.

[0013] Preferably, a pressure transmitter is included, and the hydrogen metering tank is equipped with a pressure transmitter for detecting the internal pressure of the hydrogen metering tank.

[0014] Preferably, the internal pressure of the hydrogen metering tank is 2.0 to 3.5 MPa.

[0015] Preferably, the volume of the hydrogen metering tank is 0.8 to 1.6 m 3 .

[0016] Preferably, a hydrogenation valve 1 is included, and the hydrogen inlet end of each polymerization kettle is equipped with a hydrogenation valve 1.

[0017] (3) Beneficial effects

[0018] Compared with the prior art, the present invention provides a hydrogenation device for polypropylene production, which has the following beneficial effects:

[0019] The hydrogenation device for polypropylene production adopts a hydrogen metering tank with a fixed volume as a hydrogenation and metering container. When hydrogen needs to be introduced into the hydrogen metering tank, a hydrogen replenishing valve is opened to inject hydrogen into the hydrogen metering tank, so that the interior of the hydrogen metering tank is maintained within an appropriate pressure range. The hydrogen replenishing valve is closed. When hydrogen needs to be introduced into a polymerization kettle, a second hydrogenation valve is opened to inject hydrogen into the polymerization kettle, so that the interior of the polymerization kettle can be hydrogenated at a relatively appropriate pressure during the hydrogenation process, which is beneficial for controlling the rate and amount of hydrogen transport. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the utility model.

[0021] Markings in the attached figure: 1. Polymerization kettle; 2. Hydrogenation valve 1; 3. Hydrogenation valve 2; 4. Temperature transmitter; 5. Pressure transmitter; 6. Hydrogen metering tank; 7. Hydrogen replenishment valve; 8. On-site pressure gauge; 9. Hydrogen source. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example:

[0024] See also Figure 1 A hydrogenation device for polypropylene production includes a polymerization kettle 1, a hydrogenation valve 2 3, a hydrogen metering tank 6, and a hydrogen replenishment valve 7. Several polymerization kettles 1 and several hydrogen metering tanks 6 are connected by pipelines. The pipeline connecting the polymerization kettle 1 and the hydrogen metering tank 6 is installed with a hydrogenation valve 2 3. The hydrogen metering tank 6 is used to store hydrogen. The hydrogen metering tank 6 is connected to several hydrogen replenishment valves 7. The hydrogen replenishment valve 7 is installed at the port for inputting hydrogen into the hydrogen metering tank 6. The hydrogen replenishment valve 7 is connected to a hydrogen source 9. The pipeline between the hydrogen replenishment valve 7 and the hydrogen source 9 is installed with an on-site pressure gauge 8. The gas source of the hydrogen metering tank 6 is preferably derived from a hydrogen production device that can continuously supply gas or by-product hydrogen from other internal devices of the enterprise. The hydrogen quality needs to meet the conditions for normal propylene polymerization. The pressure of the hydrogen source 9 needs to be ≥2.0MPa, preferably within the range of 2.5 to 3.5MPa. The intermittent bulk polypropylene production process usually uses empty kettle hydrogenation because the system pressure is the lowest at this time, generally ≤0.6MPa. Hydrogenation under this stress state can ensure that the hydrogen metering tank 6 can supply more polymerization kettles 1 with hydrogen after storing hydrogen once. The hydrogenation process and the hydrogen replenishment process are preferably controlled by DCS, which makes the operation accurate and convenient. By using a fixed-volume hydrogen metering tank 6 as a container for hydrogenation and metering, when hydrogen needs to be introduced into the hydrogen metering tank 6, the hydrogen replenishment valve 7 is opened to inject hydrogen into the hydrogen metering tank 6, so that the interior of the hydrogen metering tank 6 is maintained within an appropriate pressure range, and the hydrogen replenishment valve 7 is closed. When hydrogen needs to be input into the polymerization kettle 1, the hydrogenation valve 3 is opened to inject hydrogen into the polymerization kettle 1, so that the interior of the polymerization kettle 1 can be hydrogenated at a more appropriate pressure during the hydrogenation process, which is conducive to controlling the rate and amount of hydrogen delivery.

[0025] Among them, the hydrogen metering tank 6 is made of stainless steel. Considering the hydrogen embrittlement of alloy steel and carbon steel when they come into contact with hydrogen, for the safety of the equipment, the hydrogen metering tank 6, hydrogen pipelines and related facilities are preferably made of stainless steel.

[0026] This hydrogenation device also includes a temperature transmitter 4. The hydrogen metering tank 6 is equipped with a temperature transmitter 4 for detecting the internal temperature of the hydrogen metering tank 6. The setting of the temperature transmitter 4 is conducive to real-time detection of the temperature inside the hydrogen metering tank 6, convenient for collecting data during use, and conducive to monitoring the temperature inside the hydrogen metering tank 6. It is convenient to control the environment of the hydrogenation site according to the temperature condition of the hydrogen metering tank 6 during hydrogenation.

[0027] This hydrogenation device also includes a pressure transmitter 5. A pressure transmitter 5 for detecting the internal pressure of the hydrogen metering tank 6 is installed on the hydrogen metering tank 6. The temperature transmitter 4 and the pressure transmitter 5 are preferably models with communication functions, which are convenient for electrical connection with the controller. The real-time changes in pressure can be accurately displayed through the pressure transmitter 5, which is conducive to making corrections to the planned hydrogenation amount according to the pressure condition of the hydrogen metering tank 6 during hydrogenation, so as to make the hydrogenation amount more accurate, which is conducive to controlling the pressure inside the hydrogen metering tank 6.

[0028] The internal pressure of the hydrogen metering tank 6 is 2.0-3.5 MPa, and the pressure of the hydrogen metering tank 6 is controlled at a set value within the range of 2.0-3.5 MPa, for example, 2.5 MPa, which is the upper limit control value. At the same time, a lower limit setting value needs to be set, such as 1.8 MPa.

[0029] The volume of hydrogen metering tank 6 is 0.8~1.6m 3 Considering the space limitation of hydrogen metering tank 6 and the fact that more hydrogen can be added to polymerization reactor 1 after one-time storage, the volume of hydrogen metering tank 6 is recommended to be controlled within 0.8~1.6m 3 Within the range, preferably 0.8m 3 The volume within this range is more suitable for temporarily storing a more appropriate amount of hydrogen and is convenient for use in a better space.

[0030] This hydrogenation device also includes a hydrogenation valve 2. The hydrogen inlet end of each polymerization kettle 1 is equipped with a hydrogenation valve 2. The hydrogenation valve 3 is installed on the main pipeline that outputs hydrogen from the hydrogen metering tank 6. The hydrogenation valve 2 is installed on the pipeline connecting the main pipeline and the polymerization kettle 1. Through the setting of the hydrogenation valve 2, it is convenient to control the on and off of the hydrogenation part of the polymerization kettle 1, which is more conducive to the control of the hydrogen delivery part.

[0031] ① Hydrogen replenishment process: After the current batch of hydrogenation is completed, if the pressure of the hydrogen metering tank 6 is lower than 1.8 MPa, open the hydrogen replenishment valve 7 and observe the pressure change. After the pressure rises to 2.5 MPa, close the hydrogen replenishment valve 7.

[0032] ② Hydrogenation process: Confirm that the hydrogen replenishment valve 7 is in the closed state. When it is necessary to hydrogenate a certain polymerization kettle 1, open hydrogenation valve 2 and hydrogenation valve 1 in sequence, observe the pressure changes, and when the pressure in the hydrogen metering tank 6 drops to the preset node (such as 2.2MPa) obtained by converting the amount of hydrogenation this time, close hydrogenation valve 2 and hydrogenation valve 1 in sequence. At this point, the hydrogenation of this batch is completed. As long as the pressure in the hydrogen metering tank 6 is still higher than 1.8MPa, you can wait for the instruction of the next batch of hydrogenation. As the hydrogenation process progresses, although the pressure difference between the hydrogen metering tank 6 and the polymerization kettle 1 will become smaller and smaller, and the hydrogenation speed will slow down, the lower limit setting value will ensure that this hydrogenation can be completed normally.

[0033] It should be noted that references in this specification to "one embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not.

[0034] It should be readily understood that “on,” “above,” and “over” in this disclosure should be interpreted in the broadest manner, such that “on” means not only “directly on something,” but also includes “on something” with intervening features or layers therebetween, and “above” or “over” includes not only the meaning of “above” or “over,” but also includes “above” or “over” with no intervening features or layers therebetween (i.e., directly on something).

[0035] Additionally, spatially relative terms, such as "below," "beneath," "beneath," "above," and the like, may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be in other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A hydrogenation device for polypropylene production, characterized in that: The invention comprises a polymerization kettle (1), a second hydrogenation valve (3), a hydrogen metering tank (6) and a hydrogen replenishing valve (7); a plurality of polymerization kettles (1) and a plurality of hydrogen metering tanks (6) are connected via a pipeline; a second hydrogenation valve (3) is installed on the pipeline connecting the polymerization kettle (1) and the hydrogen metering tank (6); the hydrogen metering tank (6) is used for storing hydrogen; and the hydrogen metering tank (6) is connected to a plurality of hydrogen replenishing valves (7).

2. A hydrogenation device for polypropylene production according to claim 1, characterized in that: The hydrogen metering tank (6) is made of stainless steel.

3. The hydrogenation device for polypropylene production according to claim 1, characterized in that: The invention comprises a temperature transmitter (4). The hydrogen metering tank (6) is provided with the temperature transmitter (4) for detecting the internal temperature of the hydrogen metering tank (6).

4. The hydrogenation device for polypropylene production according to claim 1, characterized in that: The invention comprises a pressure transmitter (5), wherein the pressure transmitter (5) for detecting the internal pressure of the hydrogen metering tank (6) is installed on the hydrogen metering tank (6).

5. The hydrogenation device for polypropylene production according to claim 1, characterized in that: The internal pressure of the hydrogen metering tank (6) is 2.0-3.5 MPa.

6. A hydrogenation device for polypropylene production according to claim 1, characterized in that: The volume of hydrogen metering tank (6) is 0.8~1.6m 3 .

7. A hydrogenation device for polypropylene production according to claim 1, characterized in that: It includes a hydrogenation valve (2), and the hydrogen inlet end of each polymerization kettle (1) is equipped with a hydrogenation valve (2).

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