Device for reducing impurities in sewage steam stripping feed

Abstract

The utility model discloses a device for reducing sewage steam stripping feed impurities, and belongs to the technical field of methanol to olefin. The first stop valve, the first pressure gauge, the first basket filter, the second pressure gauge and the second stop valve are sequentially connected in series and then connected with the third stop valve in parallel to form a first filter loop; a fifth stop valve, a third pressure gauge, a second basket filter, a fourth pressure gauge and a sixth stop valve are sequentially connected in series and then are connected with a seventh stop valve in parallel to form a second filter loop; the settling tank, the first filtering loop, the sewage stripping feeding pump, the regulating valve, the second filtering loop, the heat exchanger and the sewage stripping tower are sequentially connected in series to form the device for reducing the sewage stripping feeding impurities. According to the utility model, the external first basket filter, the centrifugal pump and the external second basket filter respectively adopt filters with different pore diameters, so that three-stage filtration of sewage steam stripping feeding is realized, impurities of the sewage steam stripping feeding can be reduced to the greatest extent, and meanwhile, the problem that the filter at a certain part is frequently blocked is avoided.

Description

Technical Field

[0001] This utility model belongs to the field of methanol-to-olefins technology, specifically relating to a device for reducing impurities in wastewater stripping feed. Background Technology

[0002] In the methanol-to-olefins (MTO) process, the vaporized methanol undergoes chain growth under high temperature and catalyst conditions to produce low-carbon alkanes and olefins. Due to the high reaction temperature, the product gas needs to be cooled before entering the separation unit; therefore, a complete water system is required for cooling in the MTO process. During the cooling process, the water inevitably contains a large amount of solid catalysts, oily and waxy substances, and some organic matter, among other impurities. The wastewater containing these impurities is collected in a settling tank and then pumped by a wastewater stripping feed pump to a heat exchanger for heating before being sent to a wastewater stripping tower for preliminary stripping purification. Because the wastewater in the settling tank contains a large amount of impurities, it easily forms sludge. Therefore, in current MTO industrial engineering, the wastewater stripping process generally suffers from the following problems:

[0003] 1. The presence of a large amount of impurities and sludge can easily cause blockage of the filters, pipelines and heat exchangers of the wastewater stripping feed pump, increasing the frequency of cleaning and affecting process stability.

[0004] 2. A large amount of impurities and sludge in the feed of the wastewater stripping tower can easily clog the tower trays. It is difficult to clean the tower trays during normal production, which leads to reduced stripping efficiency and increased steam consumption, thereby reducing economic benefits. Utility Model Content

[0005] The purpose of this invention is to provide a device for reducing impurities in wastewater stripping feed, used in the methanol-to-olefins process to reduce blockage of pump filters, heat exchangers, pipelines and trays, equipment damage, and maintain process stability.

[0006] The device for reducing impurities in wastewater stripping feed according to this utility model consists of a settling tank, a first shut-off valve, a second shut-off valve, a third shut-off valve, a fifth shut-off valve, a sixth shut-off valve, a seventh shut-off valve, a first basket filter, a second basket filter, a first pressure gauge, a second pressure gauge, a third pressure gauge, a fourth pressure gauge, a wastewater stripping feed pump, a regulating valve, a heat exchanger, and a wastewater stripping tower.

[0007] The first shut-off valve, the first pressure gauge, the first basket filter, the second pressure gauge, and the second shut-off valve are connected in series and then in parallel with the third shut-off valve to form the first filtration circuit; the fifth shut-off valve, the third pressure gauge, the second basket filter, the fourth pressure gauge, and the sixth shut-off valve are connected in series and then in parallel with the seventh shut-off valve to form the second filtration circuit; the settling tank, the first filtration circuit, the wastewater stripping feed pump, the regulating valve, the second filtration circuit, the heat exchanger, and the wastewater stripping tower are connected in series to form the device for reducing impurities in wastewater stripping feed as described in this utility model.

[0008] Furthermore, a fourth shut-off valve is installed in parallel with the regulating valve. The fourth shut-off valve is a branch line of the regulating valve, and the flow rate can be temporarily adjusted by adjusting the opening degree of the fourth shut-off valve when the regulating valve fails.

[0009] To address the aforementioned problems with wastewater stripping feed in existing methanol-to-olefins (MTO) processes, this invention employs tiered filtration by adding basket filters of different sizes to the inlet and outlet pipelines of the wastewater stripping feed pump. This reduces clogging of pump filters, downstream pipelines, heat exchangers, and trays. The external filter before the pump uses a larger pore size to effectively filter out most of the larger catalyst particles and sludge in the wastewater, minimizing pump switching frequency. The external filter after the pump uses a smaller pore size to filter out as much catalyst and sludge as possible, significantly reducing the impact of impurities during wastewater stripping feed on downstream heat exchangers, pipelines, and the wastewater stripping tower. By adding these two sets of external filters, the impurities in the wastewater stripping feed are reduced, thereby decreasing pump switching frequency, stabilizing subsequent process production, and reducing clogging of downstream pipelines, heat exchangers, and trays, as well as equipment damage.

[0010] The working process of this utility model:

[0011] Close the third, fourth, and seventh shut-off valves, and open the first, second, fifth, sixth shut-off valves and the regulating valve; Figure 1 As shown, the wastewater containing oil sludge and other impurities generated in the methanol-to-olefins process enters the settling tank. After passing through the first shut-off valve, the wastewater pressure, measured by the first pressure gauge, is 1.40 MPa to 1.60 MPa. It then enters the external first basket filter to filter out large particles and oil sludge. After filtration, the wastewater pressure, measured by the second pressure gauge, is 1.35 MPa to 1.55 MPa. It then enters the wastewater stripping feed pump through the second shut-off valve, which pumps out the wastewater while simultaneously regulating the flow rate using a regulating valve. After passing through the fifth shut-off valve, the wastewater pressure, measured by the third pressure gauge, is 0.65 MPa to 0.85 MPa. It then enters the external second basket filter for further filtration, filtering out small particles and remaining oil sludge. The wastewater pressure, measured by the fourth pressure gauge, is 0.60 MPa to 0.80 MPa. After passing through the sixth shut-off valve, it flows into the heat exchanger for heat exchange. Finally, the wastewater after heat exchange enters the wastewater stripping tower.

[0012] When the pressure difference between the first and second pressure gauges or between the third and fourth pressure gauges is greater than 0.2 MPa, it can be determined that the external first or second basket filter is clogged due to excessive impurities and sludge filtered out. In this case, close the first and second shut-off valves and open the third shut-off valve to remove the external first basket filter and clean it. After cleaning, open the first and second shut-off valves and close the third shut-off valve to put the external first basket filter back into use. Alternatively, close the fifth and sixth shut-off valves and open the seventh shut-off valve to remove the external second basket filter and clean it. After cleaning, open the fifth and sixth shut-off valves and close the seventh shut-off valve to put the cleaned external second basket filter back into use.

[0013] The settling tank mentioned is a 144m³ tank used in the methanol-to-olefins process. 3 Vertical settling tank.

[0014] The first shut-off valve, second shut-off valve, third shut-off valve, fourth shut-off valve, fifth shut-off valve, sixth shut-off valve, seventh shut-off valve and regulating valve DN50 straight-through shut-off valve are mentioned above.

[0015] The first, second, third, and fourth pressure gauges are field pressure gauges with a range of 1.6 MPa.

[0016] The first basket filter is a 5-15 mesh basket filter;

[0017] The wastewater stripping feed pump is an OH2 type centrifugal pump containing a 30-40 mesh filter;

[0018] The second basket filter is a 50-80 mesh basket filter;

[0019] The heat exchanger is a BES type shell-and-tube heat exchanger with a wastewater side heat exchange temperature of 70.6–130℃ and a purified water side heat exchange temperature of 88.3–148℃.

[0020] The wastewater stripping tower is a 240m³ unit used in the methanol-to-olefins process. 3 A sieve tray tower with 52 trays;

[0021] A first basket filter with a mesh size of 5-15 is used because its large pore size can filter out large solid particles and large sludge in the wastewater before the centrifugal pump, which can effectively reduce the frequency of pump switching blockage and reduce process fluctuations caused by pump switching. A second basket filter with a mesh size of 50-80 is used to effectively filter out residual small particles and small pieces of sludge to prevent them from flowing into subsequent pipelines, heat exchangers and wastewater stripping towers, which can significantly reduce pipeline, heat exchanger and tower tray blockage, thereby reducing the frequency of heat exchanger cleaning and improving the stripping efficiency of wastewater stripping towers.

[0022] Advantages of this utility model:

[0023] The external basket filter before the wastewater stripping feed pump can filter out most of the impurities in the fluid and the sludge generated by the upstream process, effectively reducing the frequency of pump blockage and reducing the resulting process fluctuations and damage to the pump.

[0024] 2. The second basket filter installed after the sewage stripping feed pump is a basket filter with a smaller pore size, which can filter out residual small particulate impurities and sludge to prevent them from flowing into subsequent pipelines, heat exchangers and sewage stripping towers, greatly reducing pipeline and heat exchanger blockage, thereby reducing the frequency of heat exchanger cleaning and the blockage of the sewage stripping tower trays.

[0025] 3. The pressure gauges installed before and after the external basket filter can intuitively show the clogging status of the filter based on the pressure difference, which can provide an important basis for the filter to be cut out and cleaned, and avoid process fluctuations caused by the clogging of the external filter.

[0026] The three external basket filters (5-15 mesh) before the pump, the centrifugal pump containing a 30-40 mesh filter, and the external 50-80 mesh basket filter after the pump all use filters with different pore sizes to achieve three-stage filtration of the sewage stripping feed. This can minimize impurities in the sewage stripping feed and avoid frequent clogging of filters in certain parts. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a schematic diagram of the device for reducing impurities in wastewater stripping feed according to the present invention.

[0029] Figure 2 The diagram shows the pump switching frequency before and after installing an external filter on the wastewater stripping feed pump in a 1.8 million tons / year methanol-to-olefins process, as well as the cleaning frequency of the downstream heat exchanger. Detailed Implementation

[0030] Example 1

[0031] The device for reducing impurities in wastewater stripping feed according to this utility model comprises a settling tank 1, a first shut-off valve 2, a second shut-off valve 6, a third shut-off valve 7, a fifth shut-off valve 11, a sixth shut-off valve 15, a seventh shut-off valve 16, a first basket filter 4, a second basket filter 13, a first pressure gauge 3, a second pressure gauge 5, a third pressure gauge 12, a fourth pressure gauge 14, a wastewater stripping feed pump 8, a regulating valve 9, a heat exchanger 17, and a wastewater stripping tower 18.

[0032] The first shut-off valve 2, the first pressure gauge 3, the first basket filter 4, the second pressure gauge 5, and the second shut-off valve 6 are connected in series and then in parallel with the third shut-off valve 7 to form the first filtration circuit; the fifth shut-off valve 11, the third pressure gauge 12, the second basket filter 13, the fourth pressure gauge 14, and the sixth shut-off valve 15 are connected in series and then in parallel with the seventh shut-off valve 16 to form the second filtration circuit; the settling tank 1, the first filtration circuit, the sewage stripping feed pump 8, the regulating valve 9, the second filtration circuit, the heat exchanger 17, and the sewage stripping tower 18 are connected in series to form the device for reducing impurities in sewage stripping feed as described in this utility model.

[0033] Furthermore, a fourth shut-off valve 10 is set in parallel with the regulating valve 9. The fourth shut-off valve 10 is a branch line of the regulating valve 9. When the regulating valve 9 fails, the flow rate can be temporarily adjusted by adjusting the opening of the fourth shut-off valve 10.

[0034] This invention utilizes the wastewater stripping feed process in a 1.8 million tons / year methanol-to-olefins (MTO) process. The wastewater in the MTO process includes quench water containing a large amount of catalyst and wash water containing oily sludge. The third shut-off valve 7, the fourth shut-off valve 10, and the seventh shut-off valve 16 are closed, while the first shut-off valve 2, the second shut-off valve 6, the fifth shut-off valve 11, the sixth shut-off valve 15, and the regulating valve 9 are opened. Figure 1As shown, the wastewater containing oil sludge and other impurities generated in the methanol-to-olefins process enters the settling tank 1. After passing through the first shut-off valve 2, the wastewater pressure measured by the first pressure gauge 3 is 1.60 MPa. Then, it enters the external 10-mesh first basket filter 4 to filter out large particulate impurities and oil sludge. After filtration, the oil sludge solid content in the wastewater is reduced from 30% to 22%. After filtration, the wastewater pressure measured by the second pressure gauge 5 is 1.55 MPa. Then, it enters the wastewater stripping feed pump 8 containing a 30-mesh filter through the second shut-off valve 6. After filtration by the pump filter, the oil sludge solid content is reduced to about 15%. Wastewater stripping feed pump 8 pumps out wastewater, and at the same time, the wastewater flow rate is adjusted to 200T / H using regulating valve 9. After passing through the fifth shut-off valve 11, the wastewater pressure is measured to be 0.85MPa by the third pressure gauge 12. Then, it enters the external 60-mesh second basket filter 13 for further filtration, filtering out small particulate impurities and remaining oil sludge. After filtration, the oil sludge solid content in the wastewater is reduced to about 5%. The wastewater pressure is measured to be 0.80MPa by the fourth pressure gauge 14. After passing through the sixth shut-off valve 15, it flows into the heat exchanger 17 for heat exchange. The wastewater temperature is raised from 70.6℃ to 130℃ before entering the wastewater stripping tower 18.

[0035] like Figure 2 As shown, without the external first basket filter 4 and second basket filter 13 installed, the sewage stripping feed pump 8 is cleaned 36 times a year, and the heat exchanger 17 is cleaned 6 times a year; after the external first basket filter 4 and second basket filter 13 are installed, the sewage stripping feed pump 8 is cleaned 4 times a year, and the heat exchanger 17 is cleaned 3 times a year.

[0036] As can be seen from the above description, the embodiments of this utility model achieve the following technical effects:

[0037] 1. After installing the device to reduce impurities in the wastewater stripping feed, the cleaning frequency of the wastewater stripping feed pump 8 is reduced from 36 times a year to 4 times after the solid impurities and sludge in the wastewater are removed by the pre-filter. The pump switching frequency is reduced to 11% of the original frequency. This solves the problem of frequent pump switching caused by a lot of impurities and sludge in the wastewater stripping feed process, and avoids the impact of pump switching on the stability of subsequent processes.

[0038] 2. After installing the device to reduce impurities in the wastewater stripping feed, the wastewater entering the wastewater stripping tower undergoes three-stage filtration through external filters before and after the wastewater stripping feed pump and the pump's own filter. This reduces the cleaning frequency of heat exchanger 17 from 6 times per year to 3 times, a reduction of 50% of the original cleaning frequency. This slows down the clogging rate of impurities such as oil sludge in the wastewater on the heat exchanger, process pipelines, and wastewater stripping tower trays, ensuring the long-term stable operation of the subsequent process system.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 apparatus for reducing impurities in wastewater stripping feed, characterized in that: The first filter circuit is formed by connecting the first stop valve (2), the first pressure gauge (3), the first basket filter (4), the second pressure gauge (5) and the second stop valve (6) in series and connecting the third stop valve (7) in parallel; the second filter circuit is formed by connecting the fifth stop valve (11), the third pressure gauge (12), the second basket filter (13), the fourth pressure gauge (14) and the sixth stop valve (15) in series and connecting the seventh stop valve (16) in parallel; the first filter circuit, the second filter circuit, the sewage stripping feed pump (8), the regulating valve (9), the heat exchanger (17) and the sewage stripping tower (18) are connected in series.

2. An apparatus for reducing impurities in a feed to a sour water stripping unit as in claim 1, wherein: The fourth stop valve (10) is arranged in parallel with the regulating valve (9), and the fourth stop valve (10) is a backup line of the regulating valve (9), so that the flow rate can be temporarily adjusted by the opening of the fourth stop valve (10) when the regulating valve (9) fails.

3. An apparatus for reducing impurities in a feed to a sour water stripping unit as in claim 1, wherein: The settling tank (1) is a vertical settling tank.

4. An apparatus for reducing impurities in a feed to a sour water stripping unit as in claim 1, wherein: The first stop valve (2), the second stop valve (6), the third stop valve (7), the fourth stop valve (10), the fifth stop valve (11), the sixth stop valve (15), the seventh stop valve (16) and the regulating valve (9) are DN50 straight-through stop valves.

5. An apparatus for reducing impurities in a feed to a sour water stripping unit as in claim 1, wherein: The first pressure gauge (3), the second pressure gauge (5), the third pressure gauge (12) and the fourth pressure gauge (14) are field pressure gauges with a range of 1.6 MPa.

6. An apparatus for reducing impurities in a feed for a sour water stripping unit as in claim 1, wherein: The first basket filter (4) is a 5-15 mesh basket filter, and the sewage stripping feed pump (8) is an OH2 type centrifugal pump containing a 30-40 mesh filter; the second basket filter (13) is a 50-80 mesh basket filter.

7. An apparatus for reducing impurities in a feed for a sour water stripping unit as defined in claim 1, wherein: The heat exchanger (17) is a BES type shell-and-tube heat exchanger with a sewage side heat exchange temperature of 70.6-130℃ and a purified water side heat exchange temperature of 88.3-148℃.

8. An apparatus for reducing impurities in a feed for a sour water stripping unit as in claim 1, wherein: The sewage stripping tower (18) is a sieve plate tower containing 52 layers of tower plates.

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