An oxide washing recycling device

Abstract

An oxide washing recycling device belongs to the technical field of methanol to olefin, which is composed of an oxide washing tower, an oxide washing tower stripping water pump, a stripping water buffer tank, a washing water buffer tank, a washing water feeding pump, a washing water feeding heat exchanger, a stripping tower, a stripping water pump, a stripping water air cooler, a stripping gas heat exchanger, a stripping tower backflow tank, a stripping tower backflow pump and a stripping tower bottom reboiler. The device adopts the ordinary stripping mode to strip out the oxygen-containing compounds in the washing water and return them to a methanol to olefin reactor for recycling, and the stripped stripping water is returned to the oxide washing tower as the washing water for recycling, so that the utility consumption of the device is reduced; the oxide washing tower always uses the cleaner stripping water after stripping as the washing water, so that the oxide washing tower will not be blocked, the generation amount of the butter in the subsequent system is reduced, and the economic efficiency and the competitiveness of the device are improved.

Description

Technical Field

[0001] This utility model belongs to the field of methanol-to-olefins technology, specifically relating to an oxide washing and recycling device. Background Technology

[0002] Methanol-to-olefins (MTO) plants, serving as a crucial link between petrochemical and coal chemical industries, have become essential processes for producing ethylene and propylene. In the MTO unit, methanol, under the action of a catalyst, generates product gas which, after being washed in a quench tower and a water scrubbing tower, enters the product gas compressor in the separation unit. The product gas is then pressurized by the compressor, undergoes preliminary dehydration and oil removal, and enters an oxide scrubbing tower. After being washed with water in the oxide scrubbing tower, it is sent to subsequent distillation towers for further distillation to separate qualified products.

[0003] Currently, oxide scrubbing towers in methanol-to-olefins (MTO) industrial plants often use purified water or steam condensate from the wastewater stripping tower of the MTO unit as scrubbing water. This leads to problems such as packing blockage in the oxide scrubbing tower causing decreased scrubbing efficiency, increased dimethyl ether content in propane products, and increased energy consumption due to the use of steam condensate. The main problems are as follows: 1. Because the purified water in the MTO unit wastewater stripping tower contains catalyst particles, after being used as washing water in the oxide washing tower of the separation unit, it will clog the packing of the oxide stripping tower, causing the washing efficiency of the oxide stripping tower to decrease. During long-term operation, it is necessary to inject chemical agents to slow down the clogging rate of the oxide stripping tower, which increases the cost of the agents and also increases the difficulty of wastewater treatment. 2. As a key piece of equipment for removing oxygen-containing compounds from methanol-to-olefins product gas, the oxide scrubbing tower will experience a decrease in scrubbing efficiency. This will result in incompletely scrubbed oxygen-containing compounds from the product gas entering the subsequent alkaline scrubbing tower and the propane product. The oxygen-containing compounds in the product gas will accelerate condensation and form butter in the alkaline scrubbing tower, increasing the amount of hazardous waste produced. At the same time, incompletely scrubbed dimethyl ether will enter the final propane product, causing the product to be substandard. 3. In order to ensure the washing effect of the oxide scrubbing tower, some units switch the washing water of the oxide scrubbing tower to fresh deoxygenated water or steam condensate. Although the washing effect can be guaranteed, it increases the energy consumption of public works and reduces the overall competitiveness of the unit. Summary of the Invention

[0004] To address the problems that oxide washing towers often use purified water or steam condensate from MTO unit wastewater stripping towers as washing water, which leads to reduced washing efficiency due to packing blockage, increased dimethyl ether content in propane products, and increased energy consumption due to the use of steam condensate, this invention provides an oxide washing and recycling device.

[0005] To achieve the above objectives, this utility model is implemented through the following technical solution: An oxide washing and recycling device comprises an oxide washing tower, an oxide washing tower stripping water pump, a stripping water buffer tank, a washing water buffer tank, a washing water feed pump, a washing water feed heat exchanger, a stripping tower, a stripping water pump, a stripping water air cooler, a stripping gas heat exchanger, a stripping tower reflux tank, a stripping tower reflux pump, and a stripping tower bottom reboiler.

[0006] The oxide washing system comprises an oxide washing tower, an oxide washing tower stripping water pump, and a stripping water buffer tank. A product gas inlet is located at the bottom of the oxide washing tower, and a product gas outlet is located at the top. The bottom of the stripping water buffer tank is connected to the top of the oxide washing tower via the oxide washing tower stripping water pump. The bottom of the oxide washing tower is connected to the top of the washing water buffer tank. The stripping water in the buffer tank is pressurized by the oxide washing tower stripping water pump and enters the oxide washing tower. The product gas enters the tower from the bottom and flows upwards, contacting the stripping water counter-currently for washing. The washed product gas leaves from the top of the oxide washing tower and enters the subsequent system of the separation unit. The washed washing water is sent from the bottom of the oxide washing tower to the washing water buffer tank after being pressurized by the tower itself.

[0007] The wash water stripping system comprises a wash water buffer tank, a wash water feed pump, a wash water feed heat exchanger, a stripping tower, a stripping gas heat exchanger, a stripping tower reflux tank, a stripping tower reflux pump, and a stripping tower bottom reboiler. The bottom of the wash water buffer tank is connected to the inlet of the wash water feed heat exchanger via the wash water feed pump. The outlet of the wash water feed heat exchanger is connected to the middle of the stripping tower. The top of the stripping tower is connected to the top of the stripping tower reflux tank via the stripping gas heat exchanger. The bottom of the stripping tower reflux tank is connected to the top of the stripping tower via the stripping tower reflux pump. The stripping tower bottom reboiler is installed at the bottom of the stripping tower. The bottom of the wash water buffer tank is connected to the middle of the stripping tower via the wash water feed pump and the wash water feed heat exchanger. Wash water from the bottom of the wash water buffer tank is pressurized by the wash water feed pump and then enters the feed heat exchanger. The stripping water, heated by the stripping water in the shell side of the wash water feed heat exchanger, flows downwards into the middle of the stripping tower. At the bottom of the stripping tower, the reboiler uses saturated steam as a heat source to heat the wash water, producing stripping water and stripping gas. The stripping water collects at the bottom of the stripping tower, while the oxygen-containing compounds in the wash water mix with the stripping gas and flow towards the top of the stripping tower. The stripping gas at the top of the stripping tower is cooled and liquefied by the stripping gas heat exchanger and then enters the stripping tower reflux tank, where it is converted into liquid and non-condensable gas containing oxygen-containing compounds. The liquid in the stripping tower reflux tank is pressurized by the stripping tower reflux pump and sent to the upper part of the stripping tower. The non-condensable gas containing oxygen-containing compounds in the stripping tower reflux tank is returned to the methanol-to-olefins reactor for reprocessing via the top of the stripping tower reflux tank, thus stripping away the oxygen-containing compounds from the wash water.

[0008] The stripping water pump, the washing water feed heat exchanger, and the stripping water air cooler constitute the stripping water reuse system. The bottom of the stripping tower is connected to the shell side of the washing water feed heat exchanger via the stripping water pump, and then to the top of the stripping water buffer tank via the stripping water air cooler. The stripping water from the bottom of the stripping tower is pressurized by the stripping water pump and then cooled step by step through the shell side of the washing water feed heat exchanger and the stripping air cooler before entering the stripping water buffer tank. The stripping water is pressurized by the stripping water pump of the oxide scrubbing tower and then enters the oxide scrubbing tower as washing water. Thus, a closed water cycle is formed.

[0009] Specifically, four stripping water air coolers are connected in parallel, which can be used simultaneously or as needed for cooling.

[0010] Compared with the prior art, the advantages of this utility model are as follows: (1) Taking full account that the oxide washing tower is still relatively clean after being washed with stripping water, the oxygen-containing compounds in the washing water are stripped out by ordinary stripping and returned to the methanol-to-olefins reactor for reprocessing. The stripping water is returned to the oxide washing tower as washing water for reuse, which saves a lot of water resources. At the same time, it also produces less wastewater and reduces the consumption of public works in the unit. (2) The system process of the stripping tower was optimized, the stripping effect of the stripping tower was improved, the removal effect of oxygen-containing compounds in the washing water was guaranteed, and the dimethyl ether content in propane was kept at a low level. (3) Since the oxide washing tower always uses the cleaner stripping water as washing water, the oxide washing tower will not clog the packing and will also reduce the amount of grease generated in the subsequent system, thereby improving the economic efficiency and competitiveness of the equipment. Attached Figure Description

[0011] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0012] Figure 1 : A schematic diagram of the structure of an oxide washing and recycling device according to this utility model; In the diagram: 1. Oxide washing tower; 2. Oxide washing tower stripping water pump; 3. Stripping water buffer tank; 4. Washing water buffer tank; 5. Washing water feed pump; 6. Washing water feed heat exchanger; 7. Stripping tower; 8. Stripping water pump; 9. Stripping water air cooler; 10. Stripping gas heat exchanger; 11. Stripping tower reflux tank; 12. Stripping tower reflux pump; 13. Stripping tower bottom reboiler.

[0013] The oxide scrubbing tower 1 is equipped with three layers of stainless steel saddle-shaped packing to enhance gas-liquid scrubbing efficiency. This packing is used to wash away oxygen-containing compounds in the product gas generated from the methanol-to-olefins reaction, ensuring a reduction in butter production in the subsequent alkaline scrubbing tower and maintaining the dimethyl ether content in the propane product within acceptable limits. The oxide scrubbing tower stripping water pump 2 is a centrifugal pump used to pressurize the stripping water and return it to the oxide scrubbing tower. The stripping water buffer tank 3 is a vertical tank with a volume of 100m³, used to store and buffer the cleaner stripping scrubbing water. The stripping water; the wash water buffer tank 4 is a vertical storage tank with a volume of 100m³, used to store and buffer the wash water after washing in the oxide washing tower 1; the wash water feed pump 5 is a centrifugal pump used to pressurize the wash water, which is then heated by the wash water feed heat exchanger 6 and sent to the stripping tower 7; the wash water feed heat exchanger 6 is a common shell-and-tube heat exchanger, which transfers the heat of the stripped water at the bottom of the stripping tower 7 to the wash water; the upper and lower sections of the stripping tower 7 have different diameters, with the upper section having a smaller inner diameter and 11 layers of floating valve trays, and the lower section having a larger inner diameter and 42 layers of floating valve trays, used to transfer the heat of the stripped water to the washing water. Oxygen-containing compounds in the water are stripped away; the stripping water pump 8 is a centrifugal pump used to pressurize the stripping water at the bottom of the stripping tower 7 and send it to the shell side of the washing water feed heat exchanger 6 and the stripping water air cooler 9 for cooling; the stripping water air cooler 9 is an air cooler with a variable frequency motor (such as model YP2-250M-2), which can cool the stripping water to meet the temperature requirements of the water used in the oxide washing tower 1; the stripping gas heat exchanger 10 is a floating head heat exchanger, which cools the stripping gas containing oxygen-containing compounds at the top of the stripping tower 7; the stripping tower reflux tank 11 is a horizontal storage tank. The 20m³ volume is used to store and buffer the liquid cooled by the stripper gas heat exchanger 10; the stripper reflux pump 12 is a centrifugal pump used to pressurize the liquid in the stripper reflux tank 11 and return this part of the liquid to the top of the stripper 7; the stripper bottom reboiler 13 is a floating head heat exchanger that uses 1.0MPa steam as a heat source to heat the wash water in the lower part of the stripper 7 to obtain stripper water and stripper gas. The stripper water flows to the bottom of the stripper 7, and the oxygenated compounds in the wash water are mixed with the stripper gas and flow to the top of the stripper 7. Detailed Implementation

[0014] Example 1 like Figure 1 As shown, it includes an oxide washing system, a washing water stripping system, and a stripping water reuse system.

[0015] In this embodiment, the oxide washing system includes an oxide washing tower 1, an oxide washing tower stripping water pump 2, and a stripping water buffer tank 3. Product gas enters the oxide washing tower 1 from the bottom and flows upwards. It comes into countercurrent contact with the stripping water, which is pressurized by the oxide washing tower stripping water pump 2 and enters the tower, for washing. The washed product gas is discharged from the top of the oxide washing tower 1 and enters the alkaline washing system to remove acidic gases before entering the subsequent compression distillation system. The washed water, containing oxygenated compounds, is pumped under pressure to the washed water buffer tank 4; the stripping water comes from the stripping water buffer tank 3.

[0016] The wash water stripping system includes a wash water buffer tank 4, a wash water feed pump 5, a wash water feed heat exchanger 6, a stripping tower 7, a stripping gas heat exchanger 10, a stripping tower reflux tank 11, a stripping tower reflux pump 12, and a stripping tower bottom reboiler 13. The wash water in the wash water buffer tank 4 is pressurized by the wash water feed pump 5 and enters the tube side of the wash water feed heat exchanger 6. After being heated by the stripped water in the shell side of the wash water feed heat exchanger 6, it enters the middle section of the stripping tower 7.

[0017] The reboiler 13 at the bottom of the stripping tower uses 1.0 MPa saturated steam as a heat source and is connected to the lower part of the stripping tower 7 to heat the wash water at the bottom of the stripping tower 7 to obtain stripping water and stripping gas. The stripping water flows to the bottom of the stripping tower 7, while the oxygen-containing compounds in the wash water are mixed with the stripping gas and flow to the top of the stripping tower 7.

[0018] The stripping gas at the top of stripper 7 is cooled and liquefied by stripping gas heat exchanger 10 and then enters stripper reflux tank 11, where it is converted into liquid and non-condensable gas containing oxygen-containing compounds. The liquid in stripper reflux tank 11 is pressurized by stripper reflux pump 12 and sent to the upper part of stripper 7. The non-condensable gas containing oxygen-containing compounds in stripper reflux tank 11 is returned to methanol-to-olefins reactor for reprocessing.

[0019] The stripping water reuse system includes a stripping water pump 8, a wash water feed heat exchanger 6, and a stripping water air cooler 9. Stripping water from the bottom of the stripping tower 7 is pressurized by the stripping water pump 8 and then cooled in stages through the shell side of the wash water feed heat exchanger 6 and the stripping air cooler 9 before entering the stripping water buffer tank 3. The high-temperature stripping water flows through the shell side of the wash water feed heat exchanger 6, exchanging heat with the wash water flowing through the tube side of the wash water feed heat exchanger 6.

[0020] The stripping water in the stripping water buffer tank 3 is pressurized by the stripping water pump 2 of the oxide washing tower and then enters the oxide washing tower 1 as washing water, thus forming a closed water cycle.

[0021] Specifically, four stripping water air coolers 9 are installed, each equipped with a variable frequency motor.

[0022] The following is a detailed description of the process flow and operation of the oxide washing and recycling device provided in this embodiment: The product gas generated from the methanol-to-olefins reaction in the MTO unit is pressurized to 0.7 MPa by the first and second stages of the compressor and then enters the lower part of the oxide scrubbing tower 1. It comes into countercurrent contact with the stripping water pressurized by the oxide scrubbing tower stripping water pump 2 at 1.5 MPa, 35~40℃, and 60 t / h. After the oxygen-containing compounds in the product gas are fully removed, it is discharged from the top of the oxide scrubbing tower 1 and then enters the alkaline washing system to remove the acidic gases in the product gas before entering the subsequent compression and distillation system. The washing water containing oxygenated compounds at the bottom of the oxide washing tower 1 enters the washing water buffer tank 4 at a flow rate of 60t / h under self-pressure. The washing water in the washing water buffer tank 4 is pressurized to 1.0MPa by the washing water feed pump 5 and heated to 95~110℃ in the tube side of the washing water feed heat exchanger 6 before entering the middle of the stripping tower 7. The stripping tower 7 operates at a pressure of 0.25~0.35MPa. The 1.0MPa steam from the reboiler 13 at the bottom of the stripping tower heats the wash water at the bottom of the stripping tower 7 to 135~145℃, turning it into a gas-liquid mixture. This gas-liquid mixture comes into countercurrent contact with the wash water pressurized by the wash water feed pump 5 at the bottom of the stripping tower 7 for gas-liquid exchange. Then, it comes into countercurrent contact with the liquid pressurized by the stripping tower reflux pump 12 at the top of the stripping tower 7 for gas-liquid exchange. Through the countercurrent contact between the upper and lower parts of the stripping tower 7, stripping water and stripping gas are obtained. The stripping water flows towards the bottom of the stripping tower 7, while the oxygen-containing compounds in the wash water mix with the stripping gas and flow towards the top of the stripping tower 7, thereby stripping away all the oxygen-containing compounds in the wash water.

[0023] The stripping gas at 125-135℃ from the top of stripper 7 is cooled to 80-95℃ by stripping gas heat exchanger 10 and then enters stripper reflux tank 11 to obtain liquid and non-condensable gas containing oxygen-containing compounds. The liquid in stripper reflux tank 11 is pressurized to 1.0MPa by stripper reflux pump 12 and then returned to the upper part of stripper 7 at a rate of 10-20t / h. The non-condensable gas containing oxygen-containing compounds in stripper reflux tank 11 is returned to the methanol-to-olefins reactor for reprocessing reaction to generate olefin products at a flow rate of 500-2000Nm³ / h.

[0024] The stripping water at 120-130℃ at the bottom of stripping tower 7 is pressurized to 1.0MPa by stripping water pump 8 and then enters the shell side of the washing water feed heat exchanger 6 to exchange heat with the washing water in the tube side. After being cooled to 75-80℃, it is cooled to 35-40℃ by stripping water air cooler 9 and then enters the stripping water buffer tank 3. Finally, it is returned to the upper part of oxide washing tower 1 by oxide washing tower stripping water pump 2, thus completing the purification of the washing water and enabling its reuse.

[0025] Through the oxide washing and recycling device described in this embodiment, oxide washing tower 1 can save 60 t / h of steam condensate and reduce wastewater production by 60 t / h. Based on an annual operating time of 8000 hours, with steam condensate costing 6 yuan / ton and wastewater costing 13 yuan / ton, the cumulative cost reduction and efficiency improvement is approximately 9.12 million yuan, demonstrating considerable economic benefits. Simultaneously, the dimethyl ether content in the propane product from the subsequent compression distillation system can be maintained below 8%, meeting external sales requirements.

[0026] The technical solution of this utility model solves the problems of decreased washing efficiency caused by packing blockage in the oxide stripping tower, increased dimethyl ether content in propane products, and increased energy consumption of the unit due to the use of steam condensate in the current equipment.

[0027] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various variations and modifications can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

[0028] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0029] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, this utility model will not describe the various possible combinations separately.

[0030] Furthermore, various different embodiments of this utility model can be combined in any way, as long as they do not violate the spirit of this utility model, they should also be regarded as the content disclosed by this utility model.

Claims

1. An oxide washing and recycling device, characterized in that: It consists of an oxide scrubbing tower (1), an oxide scrubbing tower stripping water pump (2), a stripping water buffer tank (3), a washing water buffer tank (4), a washing water feed pump (5), a washing water feed heat exchanger (6), a stripping tower (7), a stripping water pump (8), a stripping water air cooler (9), a stripping gas heat exchanger (10), a stripping tower reflux tank (11), a stripping tower reflux pump (12), and a stripping tower bottom reboiler (13); among which, the oxide scrubbing tower (1), the oxide scrubbing tower stripping water pump (2), and the stripping water buffer tank (3) are... The oxide washing system consists of a washing water buffer tank (4), a washing water feed pump (5), a washing water feed heat exchanger (6), a stripping tower (7), a stripping gas heat exchanger (10), a stripping tower reflux tank (11), a stripping tower reflux pump (12), and a stripping tower bottom reboiler (13); the stripping water pump (8), the washing water feed heat exchanger (6), and the stripping water air cooler (9) constitute the stripping water reuse system; a product gas inlet is provided at the bottom of the oxide washing tower (1), and the oxide washing tower (1) is... The top is equipped with a product gas outlet. The bottom of the stripping water buffer tank (3) is connected to the upper part of the oxide washing tower (1) via the oxide washing tower stripping water pump (2). The bottom of the oxide washing tower (1) is connected to the upper part of the washing water buffer tank (4). The bottom of the washing water buffer tank (4) is connected to the inlet of the washing water feed heat exchanger (6) via the washing water feed pump (5). The outlet of the washing water feed heat exchanger (6) is connected to the middle of the stripping tower (7). The top of the stripping tower (7) is connected to the stripping tower reflux tank (11) via the stripping gas heat exchanger (10). The top of the stripping tower is connected to the top of the stripping tower (7) via the stripping tower reflux pump (12). The bottom of the stripping tower reboiler (13) is installed at the bottom of the stripping tower (7). The bottom of the washing water buffer tank (4) is connected to the middle of the stripping tower (7) via the washing water feed pump (5) and the tube side of the washing water feed heat exchanger (6). The bottom of the stripping tower (7) is connected to the shell side of the washing water feed heat exchanger (6) via the stripping water pump (8), and then connected to the top of the stripping water buffer tank (3) via the stripping water air cooler (9).

2. The oxide washing and recycling device as described in claim 1, characterized in that: The stripping water in the stripping water buffer tank (3) is pressurized by the stripping water pump (2) of the oxide washing tower and enters the oxide washing tower (1). The product gas enters the tower from the bottom of the oxide washing tower (1). The product gas flowing from bottom to top comes into countercurrent contact with the stripping water for washing. The washed product gas leaves from the top of the oxide washing tower (1) and enters the subsequent system of the separation unit. The washed washing water is sent from the bottom of the oxide washing tower (1) to the washing water buffer tank (4) after being pressurized by the tower itself.

3. The oxide washing and recycling device as described in claim 1, characterized in that: Wash water from the bottom of the wash water buffer tank (4) is pressurized by the wash water feed pump (5) and enters the tube side of the feed heat exchanger (6). After being heated by the stripping water in the shell side of the wash water feed heat exchanger (6), it enters the middle of the stripping tower (7) and flows downward. The reboiler (13) at the bottom of the stripping tower uses saturated steam as a heat source to heat the wash water at the bottom of the stripping tower (7) to obtain stripping water and stripping gas. The stripping water collects at the bottom of the stripping tower (7), and the oxygen-containing compounds in the wash water mix with the gas. The stripping gas flows to the top of the stripping tower (7); the stripping gas at the top of the stripping tower (7) is cooled and liquefied by the stripping gas heat exchanger (10) and then enters the stripping tower reflux tank (11) to be converted into liquid and non-condensable gas containing oxygen-containing compounds. The liquid in the stripping tower reflux tank (11) is pressurized by the stripping tower reflux pump (12) and sent to the upper part of the stripping tower (7). The non-condensable gas containing oxygen-containing compounds in the stripping tower reflux tank (11) is returned to the methanol-to-olefins reactor for reprocessing through the top of the stripping tower reflux tank (11).

4. The oxide washing and recycling device as described in claim 1, characterized in that: The stripping water from the bottom of the stripping tower (7) is pressurized by the stripping water pump (8) and then cooled step by step by the shell side of the washing water feed heat exchanger (6) and the stripping air cooler (9) before entering the stripping water buffer tank (3). The stripping water is pressurized by the oxide washing tower stripping water pump (2) and then enters the oxide washing tower (1) as washing water.

5. The oxide washing and recycling device as described in claim 1, characterized in that: Four stripping water air coolers (9) are set up in parallel, and each is an air cooler with a variable frequency motor.

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