Process for drying and regenerating propane dehydrogenation raw material

Abstract

The invention relates to the technical field of propane dehydrogenation raw material drying, in particular to a propane dehydrogenation raw material drying regeneration process which comprises the following steps: a propane dehydrogenation raw material sequentially flows through a front dryer and a rear dryer which are connected in series in a lower-in and upper-out manner; the front dryer is isolated and equalized in pressure; carrying out liquid-phase cyclic regeneration treatment on the bed layer of the front dryer; carrying out gas-phase cyclic regeneration treatment on the bed layer of the front dryer, and fully removing moisture in the filler of the bed layer; carrying out gas phase cooling and liquid phase cooling; and the regeneration process is closed, the front dryer is pressurized, and the front dryer is merged into the rear dryer, so that series operation is realized. In order to achieve the purpose of convenient and energy-saving operation of the on-line dehydration raw material self-regeneration dryer, the two dryers are connected in series for operation, and full dehydration of propane in the later period is guaranteed by detecting the water content of an outlet of the rear dryer in real time and automatically regenerating a drying bed layer through a regeneration system.

Description

Technical Field

[0001] The invention relates to the technical field of propane dehydrogenation raw material drying, in particular to a propane dehydrogenation raw material drying and regeneration process. Background Art

[0002] Propane is widely found in natural gas and petroleum. It is generally used as a fuel with low utilization value. As propylene is widely used in high value-added chemical products such as polypropylene, acetone, and propylene oxide, the demand for propylene is increasing. Traditional processes such as steam cracking and catalytic cracking are difficult to meet the demand for propylene supply. At present, the propane dehydrogenation process has been widely studied and applied as an alternative route for producing propylene. The propane dehydrogenation process for producing propylene requires that the propane raw material be fully dried. Otherwise, water in the feed will lead to a variety of adverse consequences, such as causing fluctuations in the operation of the heating furnace, harming the catalyst, and causing pressure fluctuations. Pre-drying the propane raw material can also prevent the freezing phenomenon after the material is fed in, avoiding damage to the equipment and affecting production. Based on this, a propane dehydrogenation raw material drying and regeneration process is proposed. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention provides a propane dehydrogenation raw material drying and regeneration process, which can better remove the water content of propane and realize the online automatic regeneration of the dryer bed.

[0004] To achieve the above object, the present invention provides the following technical solution: a propane dehydrogenation raw material drying and regeneration process, comprising the following steps:

[0005] (1) The propane dehydrogenation feedstock flows through a pre-dryer and a post-dryer connected in series in a bottom-in-top-out manner, and the moisture in the liquid propane is removed by using the drying bed;

[0006] (2) Isolate the pre-dryer in series and release the pressure to the coalescer through the condenser until the pressure is equalized to form a regeneration path;

[0007] (3) Liquid propane is drawn out from the outlet of the post-dryer, flows through the evaporator, superheater, pre-dryer, condenser and coalescer in sequence, and finally flows back to the inlet of the post-dryer to achieve liquid phase recycling and regeneration, and initially remove moisture from the drying bed in the pre-dryer; the liquid propane flows through the pre-dryer in a top-in and bottom-out manner;

[0008] (4) After the liquid phase circulation regeneration is completed, steam is introduced into the evaporator to convert the liquid propane after heat exchange into gaseous state. After the gaseous propane is heated by the superheater, it passes through the pre-dryer in an upper-in-lower-out manner. The water-containing gaseous propane is condensed by the condenser and separated by the coalescer. The obtained liquid propane is refluxed to the inlet of the post-dryer, realizing gas phase circulation regeneration and removing moisture from the drying bed in the pre-dryer for the second time;

[0009] (5) After the gas phase circulation regeneration is completed, the gas phase is cooled first and then the liquid phase is cooled. During the liquid phase cooling process, the flow mode of the liquid propane in the pre-dryer is switched from top-in and bottom-out to bottom-in and top-out;

[0010] (6) After the liquid phase is cooled down, the regeneration process is closed, the pre-dryer is pressurized, and the pre-dryer is merged into the post-dryer to realize series operation.

[0011] Preferably, in step (1), the adsorbent used in the drying bed is activated alumina.

[0012] Preferably, in step (3), in the coalescer, liquid propane and water are separated from each other, and the separated liquid propane is refluxed to the inlet of the post-dryer through a condensate pump.

[0013] Preferably, in step (3), the liquid phase circulation regeneration time is 240 minutes.

[0014] Preferably, in step (4), the gas phase circulation regeneration is divided into a heating stage and a constant temperature stage, the heating stage lasts for 420 minutes, and the constant temperature stage lasts for 240 minutes.

[0015] Preferably, in step (5), the gas phase cooling is to first gradually reduce the superheater load and shut down the superheater; then gradually reduce the evaporator load and stop introducing steam.

[0016] The present invention provides a propane dehydrogenation raw material drying and regeneration process, which has the following beneficial effects compared with the prior art:

[0017] The liquid-phase raw material drying system of the present invention is provided with two molecular sieve dryers. Propane enters from the bottom and exits from the top through the dryers to achieve the purpose of removing moisture, which can reduce the water content of propane to below 1ppm. In order to make the online self-regenerating dryer for dehydrating raw materials realize convenient and energy-saving operation, the two dryers are operated in series. By real-time detection of the water content at the outlet of the post-dryer, when the water content is high and regeneration is required, the drying bed is automatically regenerated through the regeneration system to ensure sufficient dehydration of propane in the later stage. A regeneration condensate pump is added to achieve system material balance, and the regular or on-demand online regeneration of the dryer is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0019] Figure 1 This is a schematic diagram of a propane dehydrogenation raw material drying and regeneration system of the present invention;

[0020] Figure 2 For the present invention Figure 1 Schematic diagram of middle area A;

[0021] Figure 3 For the present invention Figure 1 Schematic diagram of middle area B;

[0022] Figure 4 For the present invention Figure 1 Schematic diagram of area C in the middle.

[0023] In the figure: D201A / B-pre / post-dryer, E218-condenser, V202-coalescer, E217-evaporator, H201-superheater, P201-condensate pump. DETAILED DESCRIPTION

[0024] The following examples are used to explain the implementation methods of the present application in detail, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0025] A propane dehydrogenation raw material drying and regeneration process comprises the following steps:

[0026] (1) The propane dehydrogenation feedstock flows through the pre-dryer A and the post-dryer B connected in series in a bottom-in and top-out manner, and the moisture in the liquid propane is removed by using a drying bed (the bed material is activated alumina) to reduce the water content in the propane to less than 1 ppm;

[0027] (2) When the drying bed in the pre-dryer A needs to be regenerated, the pre-dryer A in series is isolated and the pressure is released to the coalescer through the condenser until the pressure is equalized to form a regeneration path;

[0028] (3) Liquid propane is drawn out from the outlet of post-dryer B, flows through the evaporator, superheater, pre-dryer A, condenser and coalescer in sequence, and finally flows back to the inlet of post-dryer B. The liquid phase is circulated and regenerated for 240 minutes to preliminarily remove the moisture from the drying bed in pre-dryer A. The liquid propane flows through pre-dryer A in an upper-in-lower-out manner. In the coalescer, liquid propane and water are separated from each other, and the separated liquid propane flows back to the inlet of post-dryer B through the condensate pump.

[0029] (4) After the liquid phase circulation regeneration is completed, steam is introduced into the evaporator to convert the liquid propane after heat exchange into gaseous state. After the gaseous propane is heated by the superheater, it passes through the pre-dryer A in an upper in and lower out manner. The water-containing gaseous propane is condensed by the condenser and separated by the coalescer. The obtained liquid propane is refluxed to the inlet of the post-dryer B, realizing gas phase circulation regeneration and removing moisture from the drying bed in the pre-dryer A for the second time.

[0030] Gas phase circulation regeneration is divided into a heating stage and a constant temperature stage. The heating stage lasts 420 minutes, and the constant temperature stage lasts 240 minutes.

[0031] (5) After the gas phase cycle regeneration is completed, the gas phase is cooled first, that is, the superheater load is gradually reduced and the superheater is shut down; then the evaporator load is gradually reduced and the steam is stopped; then the liquid phase is cooled. During the liquid phase cooling process, the flow mode of the liquid propane in the pre-dryer A is switched from top-in and bottom-out to bottom-in and top-out;

[0032] (6) After the liquid phase is cooled, the regeneration process is closed, the pre-dryer A is pressurized, and the pre-dryer A is merged into the post-dryer B to realize series operation.

[0033] The regeneration operation of the drying bed in the pre-dryer A is as follows. Each step has a time limit. The steps without special markings are 2 minutes.

[0034] first step:

[0035] The discharge valve XV12B at the inlet of post-dryer B is closed;

[0036] Regeneration timer reset;

[0037] All valve positions are correct.

[0038] Step 2: 60 minutes

[0039] The regeneration timer starts counting;

[0040] XV11B and XV13B are open;

[0041] After confirmation, open the post-dryer B and start the timer; all valve positions are correct.

[0042] Step 3:

[0043] XV17B opens;

[0044] XV17A is closed;

[0045] All valve positions are correct.

[0046] Step 4:

[0047] The pre-dryer A is offline, and the post-dryer B is running alone. All valve positions of XV11A, XV13A, XV24A, and XV26A are closed correctly.

[0048] Step 5:

[0049] XV12A, XV25A open;

[0050] All valve positions are correct.

[0051] Step 6:

[0052] XV15A is closed;

[0053] All valve positions are correct.

[0054] Step 7: Pressure Equalization

[0055] XV14A, XV16A, XV32 open

[0056] All valve positions are correct.

[0057] Step 8:

[0058] XV19A Close

[0059] All valve positions are correct.

[0060] Step 9:

[0061] XV18A, XV20A open;

[0062] All valve positions are correct.

[0063] Step 10:

[0064] XV29 opens;

[0065] All valve positions are correct.

[0066] Step 11:

[0067] Establish propane liquid phase circulation for 240 min

[0068] Create a loop timer and start timing;

[0069] Rev. P201;

[0070] Open LV2001 and FV2005;

[0071] The timer expires;

[0072] All valve positions are correct.

[0073] Step 12:

[0074] Heating stage 420min

[0075] Introduce LS low-pressure steam into E217 to heat propane;

[0076] When TIC2007 and TI2005 show the same value (within 5°C error, TIC2007 measures the outlet temperature of superheater H201, and TI2005 measures the inlet temperature of superheater H201), start H201;

[0077] The temperature was raised to 238°C at a heating rate of 70°C / h;

[0078] TI2003 (TI2003 mainly measures the temperature of gas / liquid propane) reaches 230℃ (error 10℃);

[0079] The heating timer ends;

[0080] All valve positions are correct.

[0081] Step 13:

[0082] Constant temperature stage 240min

[0083] The constant temperature timer starts timing;

[0084] The constant temperature timer ends;

[0085] All valve positions are correct.

[0086] Step 14:

[0087] Gas phase cooling 60min

[0088] The cooling timer starts;

[0089] TIC2007 = 175°C;

[0090] The timer ends;

[0091] All valve positions are correct.

[0092] Step 15:

[0093] Stop H201 (After this step meets the conditions, please turn off the power to the superheater in time)

[0094] All valve positions are correct.

[0095] Step 16: 60 minutes

[0096] Gradually reduce the E217 steam input and maintain the TI2005 temperature at 45℃±5℃.

[0097] And maintain TI2005 = TI2003 for at least 5 minutes; (TI2005 temperature cannot exceed 55℃ and directly go to liquid phase cooling program)

[0098] Stop LS;

[0099] The gas phase cooling timer ends;

[0100] All valve positions are correct.

[0101] Step 17:

[0102] Liquid phase cooling 180min

[0103] The liquid phase cooling timer starts timing;

[0104] XV30, XV31 are open;

[0105] TI2003 is less than 40℃ but not less than 30℃;

[0106] All valve positions are correct.

[0107] Step 18:

[0108] XV29 and XV32 are closed;

[0109] TI2003 is less than 40℃;

[0110] The timer is the end;

[0111] All valve positions are correct.

[0112] Step 19:

[0113] FV2005 is closed;

[0114] Stop P201;

[0115] All valve positions are correct.

[0116] Step 20:

[0117] XV30 and XV31 are closed;

[0118] All valve positions are correct.

[0119] Step 21:

[0120] XV18A and XV20A are closed;

[0121] All valve positions are correct.

[0122] Step 22:

[0123] XV19A opens;

[0124] All valve positions are correct.

[0125] Step 23:

[0126] XV14A and XV16A are closed;

[0127] All valve positions are correct.

[0128] Step 24:

[0129] XV15A opens;

[0130] All valve positions are correct.

[0131] Step 25:

[0132] XV12A open;

[0133] All valve positions are correct.

[0134] Step 26: Charge for 30 minutes and open XV11A;

[0135] Open the XV13A bypass valve on site to charge the pressure, and close the bypass valve when the pressures of A / B dryers are equal;

[0136] XV13A opens;

[0137] Timer ends

[0138] All valve positions are correct.

[0139] Step 27:

[0140] Charge and wait for 30 minutes

[0141] XV11A and XV13A are closed;

[0142] The charging waiting time timer starts timing;

[0143] All valve positions are correct.

[0144] Step 28:

[0145] XV12A open;

[0146] All valve positions are correct.

[0147] Step 29:

[0148] XV22A and XV25B are closed;

[0149] All valve positions are correct.

[0150] Step 30:

[0151] XV21A, XV23A, XV24B, XV26B are open;

[0152] All valve positions are correct.

[0153] Step 31:

[0154] XV21B and XV23B are closed;

[0155] All valve positions are correct.

[0156] Step 32:

[0157] XV22B open;

[0158] At this time, the pre-dryer A is placed at the rear, and the post-dryer B is placed at the front.

[0159] The other steps 32 to 63 correspond to steps 64 to 31, that is, 64 to 31 correspond to the regeneration of the pre-dryer A, and 32 to 63 correspond to the regeneration of the post-dryer B.

[0160] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A propane dehydrogenation raw material drying and regeneration process, characterized in that: The following steps are involved: (1) The propane dehydrogenation feedstock flows through a pre-dryer and a post-dryer connected in series in a bottom-in-top-out manner, and the moisture in the liquid propane is removed by using the drying bed; (2) Isolate the pre-dryer in series and release the pressure to the coalescer through the condenser until the pressure is equalized to form a regeneration path; (3) Liquid propane is drawn out from the outlet of the post-dryer, flows through the evaporator, superheater, pre-dryer, condenser and coalescer in sequence, and finally flows back to the inlet of the post-dryer to achieve liquid phase recycling and regeneration, and initially remove moisture from the drying bed in the pre-dryer; the liquid propane flows through the pre-dryer in a top-in and bottom-out manner; (4) After the liquid phase circulation regeneration is completed, steam is introduced into the evaporator to convert the liquid propane after heat exchange into gaseous state. After the gaseous propane is heated by the superheater, it passes through the pre-dryer in an upper-in-lower-out manner. The water-containing gaseous propane is condensed by the condenser and separated by the coalescer. The obtained liquid propane is refluxed to the inlet of the post-dryer, realizing gas phase circulation regeneration and removing moisture from the drying bed in the pre-dryer for the second time; (5) After the gas phase circulation regeneration is completed, the gas phase is cooled first and then the liquid phase is cooled. During the liquid phase cooling process, the flow mode of the liquid propane in the pre-dryer is switched from top-in and bottom-out to bottom-in and top-out; (6) After the liquid phase is cooled down, the regeneration process is closed, the pre-dryer is pressurized, and the pre-dryer is merged into the post-dryer to realize series operation.

2. The process for drying and regenerating propane dehydrogenation raw materials according to claim 1, characterized in that: In step (1), the adsorbent used in the drying bed is activated alumina.

3. The process for drying and regenerating propane dehydrogenation raw materials according to claim 1, characterized in that: In step (3), in the coalescer, liquid propane and water are separated from each other, and the separated liquid propane is refluxed to the inlet of the post-dryer through a condensate pump.

4. The process for drying and regenerating propane dehydrogenation raw materials according to claim 1, characterized in that: In step (3), the liquid phase circulation regeneration time is 240 minutes.

5. The process for drying and regenerating propane dehydrogenation raw materials according to claim 1, characterized in that: In step (4), the gas phase circulation regeneration is divided into a temperature rising stage and a constant temperature stage, the temperature rising stage lasts for 420 minutes, and the constant temperature stage lasts for 240 minutes.

6. The process for drying and regenerating propane dehydrogenation raw materials according to claim 1, characterized in that: In step (5), the gas phase temperature reduction is firstly to gradually reduce the superheater load and shut down the superheater; then to gradually reduce the evaporator load and stop the steam supply.

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