A crude benzene hydrogenation sectional evaporator

Abstract

The invention relates to a crude benzene hydrogenation segmented evaporator, comprising a segmented evaporator, a reboiler and a pre-evaporator; the segmented evaporator is divided into an upper segment and a lower segment by an isolation plate, the upper segment is provided with multi-layer tower plates, a spray device and a mist collector from bottom to top, and a crude benzene gas outlet is arranged on the top; the lower part of the lower segment of the evaporator is a crude benzene residual liquid storage tank, a partition is arranged above the crude benzene residual liquid storage tank, and a full-flow connecting pipe is arranged in the middle of the partition; a vent cap is arranged in the middle of the isolation plate, and a connecting pipe is arranged on one side of the isolation plate; a bottom liquid outlet and a second crude benzene residual liquid outlet are arranged at the bottom of the lower segment of the evaporator; the invention can effectively improve the phenomenon of frequent blockage of the reboiler, avoid waste caused by high benzene content in the crude benzene residual liquid, and reduce the gas phase resistance of the segmented evaporator.

Description

Technical Field

[0001] The invention relates to the technical field of benzene hydrogenation in metallurgical coking industry, and in particular to a crude benzene hydrogenation segmented evaporator suitable for a low-pressure crude benzene two-phase gas-phase hydrogenation reaction process. Background Art

[0002] The crude benzene in the coking industry mainly consists of benzene, toluene and xylene. In addition, it also contains 5% to 10% of unsaturated compounds, which are cyclic hydrocarbons and linear olefins with one or two double bonds. They are prone to polymerization reactions. In addition, the boiling points of some unsaturated compounds, sulfides and nitrogen-containing compounds are similar to the boiling points of the corresponding benzene products, and they cannot be separated by distillation. The role of the hydrorefining process is to remove all impurities, mainly thiophene, in the crude benzene by hydrogenation. Among them, all sulfides are converted into H2S, nitrides are converted into NH3, oxides are converted into H2O, and unsaturated hydrocarbons are hydrogenated to saturate. After separating and removing H2S, NH3 and H2O, the remaining hydrogenated oil can easily be produced by extractive distillation to produce high-quality benzene, toluene and xylene.

[0003] The production process of hydrofining benzene is less polluting, and the product quality is comparable to petroleum benzene, so the crude benzene refining process currently used in the coking industry is basically based on the low-pressure crude benzene hydrofining process. The crude benzene hydrofining process has two basic methods: liquid phase first and then gas phase hydrogenation and two-stage gas phase hydrogenation, and the two-stage gas phase hydrogenation is the main method.

[0004] In the present invention, crude benzene hydrogenation or crude benzene gas-phase hydrogenation refers to a reaction process of two-stage gas-phase hydrogenation of crude benzene.

[0005] The crude benzene gas phase hydrogenation process was first introduced from Germany. The crude benzene was directly gasified and hydrogenated after a simple de-weighting process in a segmented evaporator. Later, some domestic companies believed that the de-weighting degree was not enough and modified the process. Before the gas phase hydrogenation, the high-boiling point fraction in the crude benzene was first removed by distillation through a de-weighting tower to obtain light benzene, which was then gasified and hydrogenated. However, this process consumes too much energy and is not economical.

[0006] The core device of crude benzene hydrogenation gasification process is the segmented evaporator. Crude benzene is gasified in two ways. One way is 90% of crude benzene is gasified by the pre-evaporator, and the other way is the remaining 10% of crude benzene as the reflux liquid of the segmented evaporator. Through the segmented evaporator, the refining of crude benzene can continuously separate about 5% of the heavy components containing polymers, namely crude benzene residual liquid. In theory, it can improve the frequent blockage of the reboiler and reduce the impact on the subsequent hydrogenation reaction catalyst. However, the conventional segmented evaporator and its auxiliary structures are relatively complex, the gas phase resistance is large, and the energy waste is relatively serious. In addition, it is found in the actual production process that the crude benzene residual liquid has a low heavy component and a high benzene content (the benzene content is required not to exceed 20%, while the actual production usually contains more than 30%). Since the heavy components and polymers cannot be discharged in a centralized manner, not only a large amount of benzene is wasted, but also the occurrence of reboiler blockage is increased, and the impact on the subsequent hydrogenation reaction catalyst is increased. Summary of the invention

[0007] The invention provides a crude benzene hydrogenation segmented evaporator, which can effectively improve the phenomenon of frequent blockage of a reboiler, avoid waste caused by high benzene content in crude benzene residual liquid, and reduce the gas phase resistance of the segmented evaporator.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A crude benzene hydrogenation segmented evaporator, comprising a segmented evaporator, a reboiler and a pre-evaporator; characterized in that the segmented evaporator is divided into an upper evaporator section and a lower evaporator section by an isolation plate, the upper evaporator section is provided with multiple layers of tower plates, a spray device and a mist collector from bottom to top, and a crude benzene gas outlet is provided at the top; the lower part of the lower evaporator section is a crude benzene residual liquid storage tank, a partition is provided above the crude benzene residual liquid storage tank, and a full-flow connecting pipe is provided in the middle of the partition; a vent cap is provided in the middle of the isolation plate, and a connecting pipe is provided on one side of the isolation plate; a bottom liquid outlet and two crude benzene residual liquid outlets are provided at the bottom of the lower evaporator section; the bottom liquid outlet is connected to the crude benzene liquid inlet of the reboiler, the heating medium inlet of the reboiler is connected to the crude benzene gas pipeline after the hydrogenation reaction, and the heating medium outlet of the reboiler is connected to the crude benzene gas pipeline after the hydrogenation reaction The heating medium inlet of the shell side and the heating medium outlet of the shell side are connected to the crude benzene gas-liquid mixture pipeline after hydrogenation; the tube side of the pre-evaporator is provided with an external circulating hydrogen pipeline, and the external circulating hydrogen pipeline is provided with a jet mixer 1; the crude benzene liquid inlet of the pre-evaporator tube side and the spray device in the sectional evaporator are respectively connected to the crude benzene liquid pipeline; the crude benzene gas-liquid mixture outlet of the pre-evaporator tube side and the crude benzene gas-liquid mixture outlet of the reboiler are respectively connected to the crude benzene gas-liquid mixture inlet of the jet mixer 2, and the crude benzene gas-liquid mixture outlet of the jet mixer 2 is connected to the crude benzene gas-liquid mixture inlet on one side of the lower section of the evaporator between the partition and the isolation plate, and a crude benzene residual liquid outlet 1 is provided on the other side of the lower section of the evaporator between the partition and the isolation plate, and the crude benzene residual liquid outlet 1 and the crude benzene residual liquid outlet 2 are respectively connected to the crude benzene residual liquid pipeline.

[0010] The top surface of the full-flow connecting pipe is higher than the upper surface of the partition plate, and the diameter of the full-flow connecting pipe is equal to the diameter of the ventilation cap riser.

[0011] The top of the connecting pipe is flush with the isolation plate, and the bottom end of the connecting pipe passes through the isolation plate and extends downward and is inserted into the crude benzene residual liquid.

[0012] The bottom liquid outlet is higher than the second crude benzene residual liquid outlet.

[0013] The upper section of the evaporator is provided with at least 10 layers of tower trays.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) After the gas-liquid separation in the lower section of the evaporator, the crude benzene vapor directly enters the upper section of the evaporator through the vent cap, thereby effectively reducing the loss of gas phase pressure.

[0016] 2) The reflux liquid on the upper part of the partition plate can flow directly into the lower section of the evaporator; the lower section of the evaporator is provided with a partition plate to receive the liquid after gas-liquid separation of the crude benzene gas-liquid mixture, which contains polymers produced after heating and has the highest content of heavy components. The liquid is discharged as crude benzene residual liquid, which minimizes the amount of polymer-containing heavy components entering the reboiler again; the crude benzene residual liquid that is not discharged in time on the partition plate enters the crude benzene residual liquid storage tank at the bottom of the segmented evaporator through full flow; thereby effectively improving the frequent blockage of the reboiler and avoiding waste caused by high benzene content in the crude benzene residual liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic structural diagram of a crude benzene hydrogenation staged evaporator.

[0018] In the figure: 1. Pre-evaporator 2. Reboiler 3. Sectional evaporator 4. Jet mixer 1 5. Jet mixer 2 6. Isolation plate 7. Connecting pipe 8. First layer tray 9. Tenth layer tray 10. Mist collector 11. Partition 12. Full flow connecting pipe 13. Vent cap

[0019] A1. Crude benzene gas-liquid mixture inletA2. Crude benzene liquid inletB1. Crude benzene residual liquid outlet 1B2. Crude benzene gas outletB3. Bottom liquid outletB4. Crude benzene residual liquid outlet 2 DETAILED DESCRIPTION

[0020] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0021] like Figure 1As shown, a crude benzene hydrogenation segmented evaporator described in the present invention comprises a segmented evaporator 3, a reboiler 2, and a pre-evaporator 1; the segmented evaporator 3 is divided into an upper segment and a lower segment of the evaporator by an isolation plate 6, and the upper segment of the evaporator is provided with multi-layer tower plates, a spray device and a mist collector 10 from bottom to top, and a crude benzene gas outlet B2 is provided on the top; the lower part of the lower segment of the evaporator is a crude benzene residual liquid storage tank, and a partition 11 is provided above the crude benzene residual liquid storage tank, and a full-flow connecting pipe 12 is provided in the middle of the partition 11; a vent cap 13 is provided in the middle of the isolation plate 6, and a connecting pipe 7 is provided on one side of the isolation plate 6; a bottom liquid outlet B3 and a crude benzene residual liquid outlet B4 are provided at the bottom of the lower segment of the evaporator; the bottom liquid outlet B3 is connected to the crude benzene liquid inlet of the reboiler 2, the heating medium inlet of the reboiler 2 is connected to the crude benzene gas pipeline after the hydrogenation reaction, and the heating medium outlet of the reboiler 2 is connected to the crude benzene gas pipeline after the hydrogenation reaction. The heating medium inlet of the shell side in the pre-evaporator 1 and the heating medium outlet of the shell side are connected to the crude benzene gas-liquid mixture pipeline after hydrogenation; the tube side of the pre-evaporator 1 is provided with an external circulating hydrogen pipeline, and the external circulating hydrogen pipeline is provided with a jet mixer 4; the crude benzene liquid inlet of the pre-evaporator tube side and the spray device in the segmented evaporator 3 are respectively connected to the crude benzene liquid pipeline; the crude benzene gas-liquid mixture outlet of the pre-evaporator tube side and the crude benzene gas-liquid mixture outlet of the reboiler 2 are respectively connected to the crude benzene gas-liquid mixture inlet of the jet mixer 2 5, and the crude benzene gas-liquid mixture outlet of the jet mixer 2 5 is connected to the crude benzene gas-liquid mixture inlet A1 on one side of the lower section of the evaporator between the partition 11 and the isolation plate 6, and a crude benzene residual liquid outlet B1 is provided on the other side of the lower section of the evaporator between the partition 11 and the isolation plate 6, and the crude benzene residual liquid outlet B1 and the crude benzene residual liquid outlet B4 are respectively connected to the crude benzene residual liquid pipeline.

[0022] The top surface of the full-flow connecting pipe 12 is higher than the upper surface of the partition 11, and the diameter of the full-flow connecting pipe 12 is equal to the diameter of the vertical pipe of the ventilation cap 13.

[0023] The top of the connecting pipe 7 is flush with the isolation plate 6, and the bottom end of the connecting pipe 7 passes through the partition plate 11 and extends downward and is inserted into the crude benzene residual liquid.

[0024] The bottom liquid outlet B3 is higher than the crude benzene residual liquid outlet B4.

[0025] The upper section of the evaporator is provided with at least 10 layers of tower trays.

[0026] In the crude benzene hydrogenation staged evaporator described in the present invention, a vent cap 13 is provided in the middle of the isolation plate 6, and the crude benzene gas-liquid mixture enters through the crude benzene gas-liquid mixture inlet A1 of the lower section of the evaporator. The crude benzene vapor generated after gas-liquid separation directly enters the upper section of the evaporator through the vent cap 13, which can effectively reduce the loss of gas phase pressure.

[0027] The top of the connecting pipe 7 is flush with the top surface of the isolation plate 6, and the reflux liquid can flow directly from the upper section of the evaporator to the lower section of the evaporator; the lower section of the evaporator is provided with a layer of partition 11 below the crude benzene gas-liquid mixture inlet A1, which is used to receive the liquid of the crude benzene gas-liquid mixture after gas-liquid separation. The liquid contains polymers produced after heating and has the highest heavy component content. The liquid is discharged as crude benzene residual liquid, which can minimize the amount of heavy components containing polymers entering the reboiler 2 again. Compared with the method adopted by conventional sectional evaporators in which all reflux liquid is discharged from the bottom crude benzene residual liquid outlet, the present invention significantly reduces the benzene content in the crude benzene residual liquid discharged from the bottom crude benzene residual liquid outlet B4; a full-flow connecting pipe 12 with the same diameter as the vertical pipe of the vent cap 13 is provided in the middle of the partition 11, and the crude benzene residual liquid that is not discharged in time flows into the lower residual liquid storage tank, and the upper and lower layers of the partition 11 are kept in gas phase communication.

[0028] The crude benzene gas phase hydrogenation process based on the crude benzene hydrogenation staged evaporator of the present invention is as follows:

[0029] Part of the external crude benzene liquid enters the upper section of the evaporation tower through the crude benzene liquid inlet A2 and is sprayed downward by the spray device; the other part of the crude benzene liquid enters the upper part of the tube side of the pre-evaporator; the circulating hydrogen passes through the jet mixer 1 4 at high speed to form a negative pressure, so that the external crude benzene liquid circulates at high speed in the pre-evaporator 1, and the external crude benzene liquid is preheated and mostly vaporized through the pre-evaporator 1 by using the heat of the crude benzene gas after the hydrogenation reaction to form a crude benzene gas-liquid mixture. The crude benzene gas-liquid mixture passes through the jet mixer 2 5 at high speed to form a negative pressure as a power, forming a closed loop between the residual liquid storage tank at the bottom of the segmented evaporator 3 and the reboiler 2, using the heat of the crude benzene gas after the hydrogenation reaction to provide heat through the reboiler 2, and the crude benzene liquid refluxed from the top of the segmented evaporator 3 is vaporized at the bottom of the segmented evaporator 3, and the vaporization amount is controlled by maintaining the liquid level balance in the residual liquid storage tank.

[0030] The segmented evaporator 3 is provided with at least 10 layers of trays ( Figure 1 Only the first layer of trays 8 and the tenth layer of trays 9 are shown in the figure. The segmented evaporator 3 is divided into an upper section and a lower section of the evaporator by an isolation plate 6. The vaporized crude benzene gas-liquid mixture enters the lower section of the evaporator through the crude benzene gas-liquid mixture inlet A1 for gas-liquid separation. The separated liquid falls on the partition 11. The liquid contains a polymer produced after heating and has the highest content of heavy components. The liquid is continuously discharged as crude benzene residual liquid through the crude benzene residual liquid outlet B1. The liquid that is not discharged in time flows through the full flow connecting pipe 12 to the residual liquid storage tank at the bottom of the segmented evaporator 3. The separated crude benzene vapor enters the upper section of the evaporator through the vent cap 13. The gas flows upward, and transfers mass and heat with the crude benzene liquid refluxed from the top of the segmented evaporator 3 through the multi-layer trays. The mist droplets therein are removed by the mist collector 10 at the top of the segmented evaporator 3, and finally sent to the hydrogenation pre-reactor through the crude benzene gas outlet B2.

[0031] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A crude benzene hydrogenation staged evaporator, comprising a staged evaporator, a reboiler, and a pre-evaporator; characterized in that: The segmented evaporator is divided into an upper section and a lower section of the evaporator by an isolation plate. The upper section of the evaporator is provided with multiple layers of tower plates, a spray device and a mist collector from bottom to top, and a crude benzene gas outlet is provided on the top; the lower part of the lower section of the evaporator is a crude benzene residual liquid storage tank, a partition is provided above the crude benzene residual liquid storage tank, and a full-flow connecting pipe is provided in the middle of the partition; a vent cap is provided in the middle of the isolation plate, and a connecting pipe is provided on one side of the isolation plate; a bottom liquid outlet and two crude benzene residual liquid outlets are provided at the bottom of the lower section of the evaporator; the bottom liquid outlet is connected to the crude benzene liquid inlet of the reboiler, the heating medium inlet of the reboiler is connected to the crude benzene gas pipeline after the hydrogenation reaction, the heating medium outlet of the reboiler is connected to the heating medium inlet of the shell side of the pre-evaporator, and the heating medium outlet of the shell side is connected to the heating medium outlet of the pre-evaporator. The inlet is connected to the crude benzene gas-liquid mixture pipeline after hydrogenation; an external circulating hydrogen pipeline is arranged in the tube side of the pre-evaporator, and a jet mixer 1 is arranged on the external circulating hydrogen pipeline; the crude benzene liquid inlet of the tube side of the pre-evaporator and the spray device in the sectional evaporator are respectively connected to the crude benzene liquid pipeline; the crude benzene gas-liquid mixture outlet of the pre-evaporator tube side and the crude benzene gas-liquid mixture outlet of the reboiler are respectively connected to the crude benzene gas-liquid mixture inlet of the jet mixer 2, the crude benzene gas-liquid mixture outlet of the jet mixer 2 is connected to the crude benzene gas-liquid mixture inlet on one side of the lower section of the evaporator between the partition and the isolation plate, and a crude benzene residual liquid outlet 1 is arranged on the other side of the lower section of the evaporator between the partition and the isolation plate, and the crude benzene residual liquid outlet 1 and the crude benzene residual liquid outlet 2 are respectively connected to the crude benzene residual liquid pipeline.

2. A crude benzene hydrogenation staged evaporator according to claim 1, characterized in that: The top surface of the full-flow connecting pipe is higher than the upper surface of the partition plate, and the diameter of the full-flow connecting pipe is equal to the diameter of the ventilation cap riser.

3. A crude benzene hydrogenation staged evaporator according to claim 1, characterized in that: The top of the connecting pipe is flush with the isolation plate, and the bottom end of the connecting pipe passes through the isolation plate and extends downward and is inserted into the crude benzene residual liquid.

4. A crude benzene hydrogenation staged evaporator according to claim 1, characterized in that: The bottom liquid outlet is higher than the second crude benzene residual liquid outlet.

5. The crude benzene hydrogenation staged evaporator according to claim 1, characterized in that: The upper section of the evaporator is provided with at least 10 layers of tower trays.

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