Cryogenic separation, purification and denitrification tower

Abstract

The utility model discloses a cryogenic separation purification denitrification tower which comprises an upper tower body and a lower tower body which are stacked up and down, a condenser is arranged in the upper tower body, a reboiler is arranged in the lower tower body, an air outlet pipe is arranged at the top of the upper tower body, a feeding pipe is arranged on one side of the lower tower body, and discharging pipes are arranged at the bottoms of the upper tower body and the lower tower body. A liquid discharging pipe and a backflow pipe are arranged between the upper tower body and the lower tower body, a gas-liquid mixed material entering the lower tower body from the feeding pipe is gasified again through the reboiler and then is subjected to gas-liquid separation, separated liquid enters the bottom of the reboiler to be discharged, separated gas enters the upper tower body through the backflow pipe to be condensed and then is subjected to gas-liquid separation, and the separated gas enters the lower tower body through the backflow pipe. The separated gas is discharged through the gas outlet pipe, and the separated liquid enters the bottom of the upper tower body to be discharged. Methane and carbon monoxide can be better liquefied and separated, so that the content of CO contained in discharged gas is lower, and the situation that methane is discharged along the gas outlet pipe after being gasified is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of H2 / CO cryogenic separation and purification process, and specifically relates to a cryogenic separation and purification denitrification tower. Background Art

[0002] The H2 / CO cryogenic separation is to separate the net process gas mainly composed of carbon monoxide, hydrogen, methane and nitrogen sent from the conversion and purification device into a hydrogen-rich fluid, which is sent to the PSA device for purification and then sent to the H2 compression section for use. A stream of carbon monoxide fluid is sent to the downstream carbon monoxide compression section for use; a stream of methane-rich fluid is pressurized by a methane-rich gas compressor and then sent to the conversion device; a stream of nitrogen-rich fluid is used as the incinerator in the ethylene glycol workshop.

[0003] The PSA tail gas compressor compresses and boosts the analytical gas of the PSA-H2 hydrogen production device and the flash gas from the cryogenic separation, and uses it as the regeneration gas of the adsorber in the cryogenic separation device. After the regeneration is completed, it is sent to the upstream conversion and purification section for recovery, thereby improving the total recovery rate of the effective gas in the process gas.

[0004] Generally, when the concentrations and purities required by users for products are different, there are differences in the selection of the flow rate and pressure of the raw material gas by the manufacturer, and the selection of raw materials and the internal components of the raw materials are even more diverse. This process aims to use natural gas as the raw material gas to achieve the low-temperature flash distillation separation of different gases to produce product gases of CO and H2 and send them to the downstream section to prepare ethylene glycol.

[0005] The existing process gas mainly includes hydrogen, carbon monoxide, a small amount of nitrogen and methane. Since hydrogen is more difficult to liquefy than carbon monoxide and nitrogen, the process gas is gradually cooled in the cold box to liquefy most of the carbon monoxide and nitrogen, and most of the hydrogen is separated through a flashing process. At the same time, through optimization, a stripping tower is further set up to dehydrogenate, which is beneficial to the stable operation of the denitrification tower and the demethanation tower.

[0006] The denitrification tower is mainly used for the gas-liquid separation of carbon monoxide, methane and nitrogen. The existing denitrification tower is generally set for single separation. After the gas-liquid mixed material enters the denitrification tower, it directly undergoes gas-liquid separation and then is transported outwards, resulting in part of the nitrogen and CO gases being discharged outwards along the exhaust pipe, and the purity of demethanation and CO is low, and the separation effect needs to be improved. Summary of the Invention

[0007] In order to solve certain or some technical problems existing in the prior art, the purpose of this application is to provide a cryogenic separation and purification denitrification tower, which can better perform liquefaction separation on methane and carbon monoxide, make the CO content in the discharged gas less, and avoid methane gasifying and discharging along the outlet pipe.

[0008] To solve the above-mentioned existing technical problems, the present application adopts the following technical solutions:

[0009] A cryogenic separation and purification denitrification tower, comprising an upper tower body and a lower tower body stacked up and down. A condenser is provided inside the upper tower body, and a reboiler is provided inside the lower tower body. An air outlet pipe is provided at the top of the upper tower body, and a feed pipe is provided on one side of the lower tower body. Discharge pipes are provided at the bottoms of both the upper tower body and the lower tower body. A liquid discharge pipe and a reflux pipe are provided between the upper tower body and the lower tower body. The gas-liquid mixture material entering the lower tower body through the feed pipe is gasified again by the reboiler and then undergoes gas-liquid separation. The separated liquid enters the bottom of the reboiler for discharge, and the separated gas enters the upper tower body through the reflux pipe for condensation and then gas-liquid separation. The separated gas is discharged through the air outlet pipe, and the separated liquid enters the bottom of the upper tower body for discharge.

[0010] Preferably, from top to bottom, the upper tower body and the lower tower body sequentially include an exhaust area, a packing area, a buffer area, and a liquid storage area. One end of the air outlet pipe is communicated with the exhaust area at the top of the upper tower body. Both ends of the reflux pipe are respectively communicated with the buffer area inside the upper tower body and the exhaust area inside the lower tower body. Both ends of the liquid discharge pipe are respectively communicated with the liquid storage area inside the upper tower body and the packing area inside the lower tower body. The reboiler is arranged in the liquid storage area inside the lower tower body, and the condenser is arranged in the buffer area inside the upper tower body.

[0011] Preferably, a regulating valve is provided on the reflux pipe, and the liquid level inside the upper tower body is controlled by the regulating valve to accelerate the formation of accumulated liquid.

[0012] Preferably, when the liquid level in the liquid storage area inside the upper tower body is high, the opening degree of the regulating valve is adjusted smaller, and when the liquid level in the liquid storage area inside the upper tower body is low, the opening degree of the regulating valve is adjusted larger.

[0013] Preferably, the operating pressure of the upper tower body is 800 - 860 KPa.A, and the operating pressure of the lower tower body is 930 - 1000 KPa.A.

[0014] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0015] To solve the above-mentioned existing technical problems, the present application adopts the following technical solutions:

[0016] By setting up the upper tower body and the lower tower body stacked vertically, it is possible to better liquefy and separate methane and carbon monoxide, making the CO content in the discharged gas less and preventing methane from vaporizing and discharging along the outlet pipe. Add a regulating valve to the reflux pipeline from the lower tower body to the upper tower body. When the opening degrees of the tower kettle liquid supply valve and the feed valve to the upper tower body are kept constant, adjust the opening degree of this newly added regulating valve to maintain the liquid level stability in the upper tower body, making it easier to adjust and stabilize the denitrification tower. In case of non-condensable gas blockage, this regulating valve can be closed slightly to maintain the liquid level in the lower tower body and stabilize the CO product gas output, and timely avoid the phenomenon of "gas-liquid separation". Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0018] In the figure: 1, discharge pipe; 2, reboiler; 3, lower tower body; 4, drain pipe; 5, condenser; 6, upper tower body; 7, outlet pipe; 8, exhaust area; 9, packing area; 10, buffer area; 11, liquid storage area; 12, regulating valve; 13, reflux pipe; 14, feed pipe. Specific Embodiments

[0019] Next, in combination with the drawings and specific embodiments, the present application will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined with each other to form new embodiments.

[0020] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0021] The terms "first", "second", etc. in the present application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are usually of the same category, and the number of objects is not limited. For example, the first object can be one or multiple. In addition, "and / or" in the description and claims indicates at least one of the connected objects, and the character " / " generally indicates an "or" relationship between the associated objects before and after.

[0022] As Figure 1As shown in the figure, a cryogenic separation and purification denitrification tower includes an upper tower body 6 and a lower tower body 3 stacked up and down. A condenser 5 is provided in the upper tower body 6, and a reboiler 2 is provided in the lower tower body 3. An air outlet pipe 7 is provided at the top of the upper tower body 6, and a feed pipe 14 is provided on one side of the lower tower body 3. Discharge pipes 1 are provided at the bottoms of both the upper tower body 6 and the lower tower body 3. A liquid discharge pipe 4 and a reflux pipe 13 are provided between the upper tower body 6 and the lower tower body 3. The gas-liquid mixture material entering the lower tower body 3 through the feed pipe 14 is gasified again by the reboiler 2 and then undergoes gas-liquid separation. The separated liquid enters the bottom of the reboiler 2 and is discharged. The separated gas enters the upper tower body 6 through the reflux pipe 13, is condensed and then undergoes gas-liquid separation. The separated gas is discharged through the air outlet pipe 7, and the separated liquid enters the bottom of the upper tower body 6 and is discharged.

[0023] Existing denitrification towers are mainly used for gas-liquid separation of carbon monoxide, a small amount of nitrogen and methane. Since it is difficult for a single denitrification tower to effectively liquefy and separate carbon monoxide and methane, the denitrification tower is improved to be composed of an upper tower body 6 and a lower tower body 3 stacked up and down. A reboiler 2 is installed in the lower tower body 3, and a condenser 5 is installed in the upper tower body 6. When performing cryogenic separation and purification on the gas-liquid mixture material of carbon monoxide, methane and nitrogen, the mixture material first enters the lower tower body 3 through the feed pipe 14. After being heated and insulated twice by the reboiler 2, nitrogen can be in a gasified state, while most of the methane and carbon monoxide can form condensate through the lower tower body 3. For gaseous nitrogen and part of methane and CO, they enter the upper tower body 6 again through the reflux pipe 13 and are further slowly cooled down by the condenser 5, so that most of the carbon monoxide and methane are liquefied, so that CO and methane in nitrogen can be effectively condensed into liquid and stored at the bottom of the upper tower body 6. Especially for the separation effect of methane is better, so that the gas rising in the upper tower body 6 no longer contains methane and the content of CO contained is less. Among them, the condensate after condensation in the upper tower body 6 is transported to the lower tower body 3 as condensed water through the liquid discharge pipe 4, which can make the separation effect of the lower tower body 3 better. The nitrogen-rich gas (nitrogen and CO) separated by condensation in the upper tower body 6 is discharged outward through the air outlet pipe 7, and the accumulated liquid formed by condensation can be transported outward through the discharge pipe 1. Through the combination of the upper and lower tower bodies 3, nitrogen can be better separated and CO can be further liquefied. At the same time, the liquid phase discharged through the discharge pipe 1 of the upper tower body 6 can also be used as the reflux liquid of the demethanizer to improve the purity of the product CO.

[0024] Further improvement is made as follows: the upper tower body 6 and the lower tower body 3 successively include an exhaust area 8, a packing area 9, a buffer area 10, and a liquid storage area 11 from top to bottom. One end of the gas outlet pipe 7 communicates with the exhaust area 8 at the top of the upper tower body 6. Both ends of the reflux pipe 13 communicate with the buffer area 10 in the upper tower body 6 and the exhaust area 8 in the lower tower body 3 respectively. Both ends of the liquid discharge pipe 4 communicate with the liquid storage area 11 in the upper tower body 6 and the packing area 9 in the lower tower body 3 respectively. The reboiler 2 is arranged in the liquid storage area 11 in the lower tower body 3, and the condenser 5 is arranged in the buffer area 10 in the upper tower body 6.

[0025] When the mixed material enters the upper tower body 6 and the lower tower body 3, the gaseous material rising upward will first pass through the packing area 9 for liquid filtration, thus avoiding the problem of liquid in the gas discharged from the gas outlet pipe 7. Both ends of the reflux pipe 13 communicate with the buffer area 10 in the upper tower body 6 and the exhaust area 8 in the lower tower body 3 respectively, which can make the liquid particles in the mixture entering the upper tower body 6 fewer, and the condensation efficiency in the upper tower body 6 is higher. Moreover, the gas is directly transported to the cooling and condensing area of the condenser 5 for cooling and condensation, and the condensation effect on the condensate of CO is better. Both ends of the liquid discharge pipe 4 communicate with the liquid storage area 11 in the upper tower body 6 and the packing area 9 in the lower tower body 3 respectively. When the condensate at the bottom of the upper tower body 6 is discharged downward through the liquid discharge pipe 4, the packing area 9 in the lower tower body 3 can be directly cooled, avoiding a large amount of vaporized CO and methane flowing into the upper tower body 6 due to too high temperature.

[0026] During the process of process production, it is found that the setting of the upper and lower towers of the denitrification tower has the phenomenon that it is difficult to control stably for a long time. The non-condensable gas caused by the temperature change at the front end of the cold box in the denitrification tower will accumulate in the denitrification tower, resulting in a significant increase in the pressure change of the denitrification tower, deviating from the normal working pressure and unable to achieve the normal operating condition. And because the non-condensable gas blocks between the upper tower body 6 and the lower tower body 3, causing the phenomenon of "gas supporting liquid", it is difficult for the gas and liquid in the lower tower body 3 to reach the upper tower, the liquid in the upper tower body 6 is blocked above and cannot flow back to the lower tower body 3, the liquid level of the lower tower body 3 drops sharply because it is continuously sent to the demethanation tower but does not get the reflux from the upper tower, and the liquid level of the upper tower body 6 continues to rise, resulting in a continuous increase in the pressure difference between the upper tower body 6 and the product gas outlet, losing the normal condition of the denitrification tower and being difficult to adjust back quickly, resulting in H2 in the rich nitrogen gas separated by the denitrification tower and the CO gas and CH4 gas separated by the subsequent demethanation tower and methane separator, reducing the production of product CO and H2. Therefore, further improvement is made to the above technical solution: a regulating valve 12 is provided on the reflux pipe 13, and the liquid level in the upper tower body 6 is controlled by the regulating valve 12 to accelerate the formation of liquid accumulation.

[0027] When the cold energy of the denitrification tower is stable, the overall pressure of the denitrification tower is adjusted by the level of the reflux liquid level in the upper tower. Since there is a heat exchanger at the top of the denitrification tower, the circulating nitrogen and the process gas exchange cold and heat, so the denitrification tower is cooled from the upper tower first and then to the lower tower. When the liquid level in the upper tower is between 30% and 40%, the overall pressure of the denitrification tower will gradually decrease. If the liquid level in the upper tower is allowed to be too high all the time, the overall pressure of the tower will drop below the working pressure, resulting in a low pressure difference between the lower tower and the demethanizer, so that the process liquid sent to the demethanizer becomes less. At this time, the opening degrees of the tower kettle liquid level valve and the feed valve sent to the upper tower need to be adjusted frequently. A regulating valve 12 is added to the reflux pipe 13 line between the upper tower body 6 and the lower tower body 3 of the denitrification tower. When the opening degrees of the liquid supply valve of the lower tower body 3 and the feed valve sent to the upper tower body 6 are kept constant, the opening degree of this newly added regulating valve 12 is adjusted to maintain the stability of the liquid level in the upper tower, making the denitrification tower easier to adjust and stabilize. It is beneficial to quickly accumulate the liquid level of the upper tower body 6 of the denitrification tower during the precooling and liquid accumulation process, accelerating the liquid accumulation process; during the deep cooling separation and load increase process, it can avoid the liquid level in the lower tower body 3 being too high, causing flooding of the lower tower body 3; it can also avoid the liquid level in the upper tower body 6 being too low, resulting in insufficient reflux liquid for the demethanizer and unqualified products; effectively adjust the liquid levels of the upper tower body 6 and the lower tower body 3 of the denitrification tower, which has a certain effect on stabilizing the operating conditions of the denitrification tower; it can also appropriately control the pressures of the upper and lower towers of the denitrification tower, effectively control the liquid levels of the upper and lower towers, and accelerate the liquid accumulation process during startup.

[0028] Further improvement is that when the liquid level in the liquid storage area 11 in the upper tower body 6 is high, the opening degree of the regulating valve 12 is reduced, and when the liquid level in the liquid storage area 11 in the upper tower body 6 is low, the opening degree of the regulating valve 12 is increased.

[0029] When the liquid level in the upper tower body 6 is high, close the regulating valve 12, and when the liquid level in the upper tower body 6 is low, open the regulating valve 12 to maintain the stability of the reflux in the upper and lower towers, so that the liquid level in the upper tower remains stable.

[0030] Further improvement is that the operating pressure of the upper tower body 6 is 800 - 860 KPa.A, and the operating pressure of the lower tower body 3 is 930 - 1000 KPa.A.

[0031] Maintain the normal operating pressure of the upper tower body 6 at 800 - 860 KPa.A and the operating pressure of the lower tower body 3 at 930 - 1000 KPa.A; when non-condensable gas blockage occurs, observe the various indicators of the denitrification tower in time, close the regulating valve 12 in advance, and cooperate with slightly opening the angle valve for discharging non-condensable gas to maintain the normal liquid level of 80% - 100% in the lower tower and the stable production of CO product gas.

[0032] The above embodiments are only the preferred embodiments of the present application and cannot be used to limit the scope of protection of the present application. Any non-substantive changes and substitutions made by those skilled in the art based on the present application belong to the scope of protection required by the present application.

Claims

1. A cryogenic separation and purification denitrification tower, characterized in that: It includes an upper tower body (6) and a lower tower body (3) stacked up and down. A condenser (5) is provided in the upper tower body (6), and a reboiler (2) is provided in the lower tower body (3). An air outlet pipe (7) is provided at the top of the upper tower body (6), and a feed pipe (14) is provided on one side of the lower tower body (3). Discharge pipes (1) are provided at the bottoms of both the upper tower body (6) and the lower tower body (3). A liquid discharge pipe (4) and a reflux pipe (13) are provided between the upper tower body (6) and the lower tower body (3). The gas-liquid mixture material entering the lower tower body (3) through the feed pipe (14) is vaporized again by the reboiler (2) and then undergoes gas-liquid separation. The separated liquid enters the bottom of the reboiler (2) for discharge, and the separated gas enters the upper tower body (6) through the reflux pipe (13) for condensation and then gas-liquid separation. The separated gas is discharged through the air outlet pipe (7), and the separated liquid enters the bottom of the upper tower body (6) for discharge.

2. The cryogenic separation and purification denitrification tower according to claim 1, wherein: The upper tower body (6) and the lower tower body (3) sequentially include an exhaust area (8), a packing area (9), a buffer area (10), and a liquid storage area (11) from top to bottom. One end of the air outlet pipe (7) is communicated with the exhaust area (8) at the top of the upper tower body (6), and both ends of the reflux pipe (13) are respectively communicated with the buffer area (10) in the upper tower body (6) and the exhaust area (8) in the lower tower body (3). Both ends of the liquid discharge pipe (4) are respectively communicated with the liquid storage area (11) in the upper tower body (6) and the packing area (9) in the lower tower body (3). The reboiler (2) is provided in the liquid storage area (11) in the lower tower body (3), and the condenser (5) is provided in the buffer area (10) in the upper tower body (6).

3. A cryogenic separation and purification denitrification tower according to claim 2, characterized in that: A regulating valve (12) is provided on the reflux pipe (13), and the liquid level in the upper tower body (6) is controlled by the regulating valve (12) to accelerate the formation of accumulated liquid.

4. A cryogenic separation and purification denitrification tower according to claim 3, characterized in that: When the liquid level in the liquid storage area (11) in the upper tower body (6) is high, the opening degree of the regulating valve (12) is reduced; when the liquid level in the liquid storage area (11) in the upper tower body (6) is low, the opening degree of the regulating valve (12) is increased.

5. A cryogenic separation and purification denitrification tower according to claim 4, characterized in that: The operating pressure of the upper tower body (6) is 800 - 860 KPa.A, and the operating pressure of the lower tower body (3) is 930 - 1000 KPa.A.

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