A non-disturbance online purging and ash removal method for a detoxification tank inlet pipeline

Abstract

The application discloses a kind of non-disturbance online purging and ash removal methods of detoxification tank inlet pipeline, it is related to methanol device pulverized coal gasification process technical field, it is applied to the first detoxification tank and the second detoxification tank of parallel operation, method includes the following steps: S1: gradually close the opening degree of first detoxification tank inlet valve to reduce its gas amount and improve the gas amount of second detoxification tank, high flow rate purging is carried out to second detoxification tank inlet pipeline;S2: the pressure rise rate of the pressure of upstream pipeline at the inlet shared by two parallel detoxification tanks is controlled to be less than preset rate threshold during purging process, and the pressure does not exceed preset pressure;S3: observe the differential pressure of second detoxification tank, if differential pressure drops more than preset differential pressure threshold, then indicate that ash block of second detoxification tank inlet pipeline falls off, and single purging maintains set time;S4: repeat steps S1 to S3 a total of N times;S5: again gradually close the inlet valve of second detoxification tank, repeat all steps S1 to S4 described above to the first detoxification tank inlet pipeline;The method greatly reduces system resistance drop, prolongs device operation cycle, and maintains high load production.

Description

Technical Field

[0001] This invention relates to the field of pulverized coal gasification technology for methanol plants, and in particular to a non-disturbing online purging and ash removal method for the inlet pipeline of a detoxification tank. Background Technology

[0002] A coal-to-methanol plant's pulverized coal gasification process includes a detoxification tank to remove catalyst poisons such as coal ash from the crude syngas. However, due to poor ash washing technology in the pulverized coal process, the ash content in the crude syngas is as high as 3.9 mg / Nm3, exceeding the ash-holding capacity of the protective agent bed in the detoxification tank (design specification: dust content in the crude syngas after washing should be ≤1 mg / Nm3).

[0003] During a major overhaul in 2022, a detoxification tank was added to the coal-to-methanol plant and put into operation alongside the original detoxification tank in order to increase ash holding capacity, reduce the frequency of reagent replacement, and extend the plant's operating cycle. After being put into operation, it was found that the inlet pipelines of the two detoxification tanks experienced ash blockage and gas flow distribution deviation due to a decrease in the amount of crude syngas and a decrease in flow velocity. This led to an increase in the system pressure differential and an increase in the upstream pressure of the detoxification tanks, exceeding the operating pressure range that the upstream units could withstand. As a result, the plant had to operate at reduced load and had to shut down to clean the detoxification tank pipelines. The frequent shutdowns and maintenance led to a decline in the economic benefits of the coal-to-methanol plant. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a non-disturbing online purging and ash removal method for the inlet pipeline of the detoxification tank, which greatly reduces the system resistance drop, extends the operating cycle of the device, and maintains high-load production.

[0005] This invention proposes a non-disturbing online purging and ash removal method for the inlet pipeline of a detoxification tank, applied to a first and second detoxification tank operating in parallel. The method includes the following steps: S1: Gradually reduce the opening of the inlet valve of the first detoxification tank to reduce its gas volume and increase the gas volume of the second detoxification tank, and purge the inlet pipeline of the second detoxification tank at a high flow rate. S2: During the purging process, the pressure rise rate at the upstream inlet pipe shared by the two parallel detoxification tanks is controlled to be less than the preset rate threshold and the pressure does not exceed the preset pressure. S3: Observe the pressure difference of the second detoxification tank. If the pressure difference drops beyond the preset pressure difference threshold, it indicates that the ash block in the inlet pipeline of the second detoxification tank has fallen off. The single purging is maintained for the set time. S4: Repeat steps S1 to S3 a total of N times; S5: Gradually reduce the opening of the inlet valve of the second detoxification tank, and repeat all the above steps S1 to S4 for the inlet pipeline of the first detoxification tank.

[0006] Furthermore, the preset rate threshold is set to (0.05-0.2) MPa / min.

[0007] Furthermore, the preset pressure is set to (3-4.5) MPa.

[0008] Furthermore, the preset rate threshold is set to 0.1 MPa / min.

[0009] Furthermore, the preset pressure is set to 3.9 MPa.

[0010] Further, in step S3, the preset differential pressure threshold is (50-100) kPa.

[0011] Furthermore, in step S3, the set time is (20-50) minutes.

[0012] Furthermore, the set time is 30 minutes.

[0013] Furthermore, before the purging operation, communicate with upstream and downstream units to inform them that the pressure at the crude syngas boundary will increase.

[0014] Furthermore, after the purging is completed, communication is established with upstream and downstream units to restore stable operation.

[0015] The advantages of the non-disturbing online purging and ash removal method for the inlet pipeline of the detoxification tank provided by this invention are as follows: The method in this embodiment is effective, reducing the pressure difference by 50-100 kPa each time, greatly reducing system resistance, extending the operating time and maintenance cycle of the unit, maintaining high-load production, improving the economic efficiency of coal-to-methanol unit operation, and also reducing the safety and environmental risks and maintenance costs caused by frequent shutdowns for maintenance; in addition, the method is simple and easy to standardize; the production fluctuations during the online non-disturbing purging and ash removal process are controllable; and the unit operating cycle is extended to more than one year. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the parallel operation process of the detoxification tanks of the present invention; Figure 2 This is a schematic diagram comparing the loads before and after undisturbed purging. Detailed Implementation

[0017] The technical solution of the present invention will now be described in detail through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] like Figure 1 and 2As shown, the present invention proposes a non-disturbing online purging and ash removal method for the inlet pipeline of a detoxification tank, applied to a first detoxification tank A and a second detoxification tank B operating in parallel. The method includes the following steps: S1: Gradually reduce the opening of the inlet valve of the first detoxification tank A to reduce its gas volume and increase the gas volume of the second detoxification tank B, and purge the inlet pipeline of the second detoxification tank B at a high flow rate. In this embodiment, the crude syngas itself is used to purge the inlet pipeline of the second detoxification tank B at a high flow rate. The flow distribution of the parallel detoxification tanks is adjusted by: reducing the opening of the inlet valve of the first detoxification tank A, allowing more crude syngas to flow into the second detoxification tank B, thereby increasing the gas velocity in the inlet pipeline of the second detoxification tank B. The impact and carrying effect of the high-velocity airflow then causes the scale on the pipe wall to detach.

[0019] Similarly, high-velocity purging of the first detoxification tank A can be achieved by reducing the opening of the inlet valve of the second detoxification tank B.

[0020] S2: During the purging process, the pressure rise rate at the upstream inlet pipe shared by the two parallel detoxification tanks is controlled to be less than the preset rate threshold and the pressure does not exceed the preset pressure. In this embodiment, the preset rate threshold is set to (0.05-0.2) MPa / min, and the preset pressure is set to (3-4.5) MPa. Preferably, the preset rate threshold is set to 0.1 MPa / min and the preset pressure is set to 3.9 MPa.

[0021] S3: Observe the pressure difference of the second detoxification tank B. If the pressure difference drops beyond the preset pressure difference threshold, it indicates that the ash block in the inlet pipeline of the second detoxification tank has fallen off. The single purging is maintained for the set time. The time setting in this embodiment is (20-50) minutes, preferably 30 minutes.

[0022] S4: Repeat steps S1 to S3 a total of N times; In this embodiment, N can be selected according to actual needs, and preferably N=3.

[0023] S5: Gradually reduce the opening of the inlet valve of the second detoxification tank B, and repeat all the above steps S1 to S4 for the inlet pipeline of the first detoxification tank A.

[0024] This embodiment, through long-term exploration and practical verification, has mastered the ash blockage pattern of the detoxification tank inlet pipeline, explored and determined the relationship between ash block loosening and falling and gas velocity, and gradually solidified into a method for undisturbed online purging of the detoxification tank inlet pipeline. In addition, before performing steps S1 to S4, communication is made with upstream and downstream units to inform them that the pressure in the crude syngas boundary zone will rise; after purging, communication is made with upstream and downstream units to restore stable operation and avoid abnormal fluctuations in production operation.

[0025] In this embodiment, during normal and stable operation of the device, the gas flow distribution between the two parallel detoxification tanks is periodically adjusted to increase the gas velocity in one of the tanks, thereby purging its inlet pipe and causing ash deposits to fall off the pipe wall. This reduces the system pressure differential, maintaining the device's stable and efficient operation without affecting normal operation. A schematic diagram of the detoxification tank process and markings for easily clogged pipe sections are shown below. Figure 1 PI indicates the upstream pressure of the detoxification tank, while PDI indicates the differential pressure caused by ash blockage in the adsorbent bed and inlet pipeline of the detoxification tank.

[0026] Practice has proven that the method in this embodiment is effective, reducing the pressure difference by 50-100 kPa each time, greatly reducing system resistance, extending the operating time and maintenance cycle of the unit, maintaining high-load production, improving the economic efficiency of coal-to-methanol unit operation, and also reducing the safety and environmental risks and maintenance costs caused by frequent shutdowns for maintenance.

[0027] Example 1 The coal-to-methanol unit commenced operation on February 24, 2025, after completing the detoxification tank replacement and inlet pipeline cleaning and maintenance. The initial pressure differential was 65 kPa, which rose to 170 kPa by June 3. After online undisturbed purging and ash removal, the pressure differential decreased to 90 kPa. Subsequent online purging and ash removal were implemented on July 6, August 24, September 28, and October 27, resulting in a pressure differential reduction of 50-100 kPa each time, demonstrating good effectiveness.

[0028] Comparative experiment: Scheme 1, existing technology: such as Figure 1 As shown, one of the detoxification tanks experienced ash blockage in its bed and inlet pipeline. The inlet and outlet valves of this detoxification tank were closed, and refrigerant replacement and inlet pipeline cleaning were performed. In Scheme 1, because the refrigerant replacement maintenance of one detoxification tank lasted approximately 4 days, the other detoxification tank experienced high gas volume and high pressure differential, resulting in high pressure in the upstream gasification unit. This necessitated reduced load operation during the refrigerant replacement maintenance period.

[0029] Option 2: Using the purging and ash removal method of this embodiment, gradually reduce the opening of the inlet valve of the first detoxification tank A to decrease its gas volume and increase the gas volume of the second detoxification tank B, and perform high-velocity purging on the inlet pipeline of the second detoxification tank B; or, gradually reduce the opening of the inlet valve of the second detoxification tank B to decrease its gas volume and increase the gas volume of the first detoxification tank A, and perform high-velocity purging on the inlet pipeline of the first detoxification tank A.

[0030] In 2024, Scheme 1 was adopted for purging and ash removal. During this period, due to blockage in the inlet pipeline of the detoxification tank, three agent replacement maintenance operations were required. Each maintenance operation required reduced load operation to achieve the desired results. Figure 2 The load curve for 2024 is shown below.

[0031] In 2025, Option 2 was adopted for purging and ash removal. No maintenance or downtime was required; online purging was achieved solely through gradual valve adjustments, yielding the desired results. Figure 2 The load curve for 2025 is shown below.

[0032] Analysis of the 2024 load curve revealed a significant trough during the maintenance period, reflecting load reduction operations. The 2025 load curve showed overall stable operation with no significant load decrease. Regarding the effects before and after implementing undisturbed online purging: each purging and ash removal operation of the detoxification tank inlet pipeline achieved undisturbed and stable operation of the unit, ensuring stable operation under high load for extended periods.

[0033] Analysis shows that from February 24 to May 31, 2025, the average load of the coal-to-methanol unit remained at 103.5%; from June 3 to November 15, the average load remained at 103.2%. In 2024, due to three refrigerant replacement maintenance operations in the detoxification tank (during which load reduction was required, resulting in significant load fluctuations and a clear downward trend), the annual average load was 99.8%. The annual average load in 2025 (approximately 103.3%) increased by about 3.5 percentage points compared to 2024 (99.8%), directly improving the unit's capacity and economic benefits.

[0034] The load remained above 103% throughout 2025, with no load drop due to purging operations, verifying the non-disruptive technical effect of this embodiment.

[0035] Comparison of the effects of this embodiment with traditional methods: The method described in this embodiment is simple and easy to standardize; the production fluctuations during the online, undisturbed purging and ash removal process are controllable; and the operating cycle of the device is extended to more than one year. Traditional method: Frequent blockage of the inlet pipeline of the detoxification tank. Six months after maintenance and commissioning, the calculated pressure difference rises to about 200 kPa, requiring shutdown to clean the inlet pipeline of the detoxification tank, which affects the long-term high-load operation of the unit.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for undisturbed online purging and ash removal of the inlet pipeline of a detoxification tank, characterized in that, Applied to a first and second detoxification tanks operating in parallel, the method includes the following steps: S1: Gradually reduce the opening of the inlet valve of the first detoxification tank to reduce its gas volume and increase the gas volume of the second detoxification tank, and purge the inlet pipeline of the second detoxification tank at a high flow rate. S2: During the purging process, the pressure rise rate at the upstream inlet pipe shared by the two parallel detoxification tanks is controlled to be less than the preset rate threshold and the pressure does not exceed the preset pressure. S3: Observe the pressure difference of the second detoxification tank. If the pressure difference drops below the preset pressure difference threshold, it indicates that the ash block in the inlet pipeline of the second detoxification tank has fallen off. The single purging is maintained for the set time. S4: Repeat steps S1 to S3 a total of N times; S5: Gradually reduce the opening of the inlet valve of the second detoxification tank, and repeat all the above steps S1 to S4 for the inlet pipeline of the first detoxification tank.

2. The method according to claim 1, characterized in that, The preset rate threshold is set to (0.05-0.2) MPa / min.

3. The method according to claim 1, characterized in that, The preset pressure is set to (3-4.5) MPa.

4. The method according to claim 2, characterized in that, The preset rate threshold is set to 0.1 MPa / min.

5. The method according to claim 3, characterized in that, The preset pressure is set to 3.9 MPa.

6. The method according to claim 1, characterized in that, In step S3, the preset differential pressure threshold is (50-100) kPa.

7. The method according to claim 1, characterized in that, In step S3, the set time is (20-50) minutes.

8. The method according to claim 5, characterized in that, The set time is 30 minutes.

9. The method according to claim 1, characterized in that, Before the purging operation, communicate with the upstream and downstream units to inform them that the pressure in the crude syngas boundary area will increase.

10. The method according to claim 1, characterized in that, After the purging is completed, communication is made with upstream and downstream units to restore stable operation.

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