Scrubbing tower system for methanol-to-olefins reaction gas

Abstract

Provided in the present invention is a scrubbing tower system for a methanol-to-olefins reaction gas. A catalyst settled at the bottom of a scrubbing tower is introduced into a waste water tank so as to alleviate the problem of system blockage. When the catalyst blocks a pipe inlet at the bottom of the tower, a solenoid valve b is closed to disconnect a pipe leading to the waste water tank, and a solenoid valve a on a deoxygenated water intake pipe a is then opened, such that deoxygenated water backflushes the pipe inlet at the bottom of the tower, thereby ensuring that the catalyst can continuously flow into the waste water tank. The operation is simple, and the investment cost is low.

Description

A methanol-to-olefins reaction gas scrubbing tower system Technical Field

[0001] This invention belongs to the field of methanol-to-olefins technology, specifically to a methanol-to-olefins reaction gas scrubbing tower system. Background Technology

[0002] The methanol-to-olefins (MTO) unit uses methanol as feedstock. By controlling appropriate reaction conditions and employing specialized catalysts, methanol is reacted to produce a reaction gas rich in low-carbon olefins. The main products are ethylene and propylene. After being washed by a quench tower and a water scrubbing tower, the gas enters the reaction gas compressor. The quench tower and water scrubbing tower systems in the MTO unit are tasked with washing away any small amounts of catalyst entrained in the reaction gas, condensing moisture in the reaction gas, and removing impurities.

[0003] The high-temperature reaction gas from the reactor undergoes heat exchange in a methanol-reaction gas heat exchanger. After heat recovery, the ethylene- and propylene-rich reaction gas enters the lower part of the quench tower. The reaction gas flows upwards and counter-currently contacts the cooling water at the top of the quench tower, washing away any small amount of catalyst carried in the gas and simultaneously lowering its temperature. After quenching, the reaction gas flows from the top of the quench tower into the lower part of the water washing tower. The reaction gas flows upwards and counter-currently contacts the washing water, further reducing its temperature. Finally, the reaction gas enters the compressor in the olefin separation unit for compression and separation.

[0004] Currently, the water system of methanol-to-olefins (MTO) plants, due to the use of quench towers and water washing towers, cannot completely remove the catalyst during washing. This leads to the inability to use the water pump filters, easily damaging the pump seals. Furthermore, the catalyst carried in the water clogs heat exchangers and trays, resulting in poor overall equipment performance, high equipment maintenance and repair costs, high energy consumption, and high operating costs. At present, MTO plants commonly add reagents to the water system to alleviate the clogging problem, but the effect is not good and the cost is expensive. The overall operation of the water system of MTO plants is poor, the investment cost is large, the operation is difficult, and the labor intensity is high. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a methanol-to-olefins reaction gas scrubbing tower system. This system guides the catalyst settled at the bottom of the scrubbing tower into a wastewater tank to alleviate system blockage. When the catalyst blocks the pipe inlet at the bottom of the tower, solenoid valve b is closed, cutting off the wastewater tank pipeline. Then, solenoid valve a on the deoxygenated water inlet pipe a is opened, allowing the deoxygenated water to backflush the pipe inlet at the bottom of the tower, ensuring a continuous flow of catalyst into the wastewater tank. The system is simple to operate and has low investment costs.

[0006] The technical solution adopted in this invention is as follows:

[0007] A methanol-to-olefins reaction gas scrubbing tower system includes a scrubbing tower, the bottom of which is connected to a wastewater tank via a pipe. The pipe at the bottom of the scrubbing tower is connected to a deoxygenated water inlet pipe a. A water pressure sensor a and a solenoid valve a are installed on the deoxygenated water inlet pipe a. A solenoid valve b and a flow sensor a are installed on the pipe at the bottom of the scrubbing tower, located between the deoxygenated water inlet pipe a and the wastewater tank.

[0008] Preferably, the washing tower includes an outer shell, in which a settling zone is provided, and a perforated tray is provided on one side of the settling zone. Below the perforated tray, an overflow tray, a double overflow tray, a perforated tray, a grid, and a settling zone are arranged in sequence.

[0009] Preferably, a bottom extraction port is provided between the bottom sieve tray and the bottom grid, and a bottom pump is connected to the bottom pump via a pipeline. The bottom pump is connected to a bottom heat exchanger that communicates with the washing tower via a pipeline.

[0010] Preferably, the bottom outlet of the tower is connected to the deoxygenated water inlet pipe a via a pipeline, and a water pressure sensor b and a solenoid valve c are installed in the pipeline connecting the bottom outlet of the tower to the deoxygenated water inlet pipe a, and a flow sensor b and a solenoid valve d are installed in the pipeline connecting the bottom outlet of the tower to the bottom pump.

[0011] Preferably, the bottom extraction outlet of the tower is provided with at least two outlets, and each bottom extraction outlet is connected to the same bottom pump through a pipeline.

[0012] Preferably, the settling zone in the tower is provided with a tower extraction outlet, the tower extraction outlet is connected to a tower pump via a pipeline, the tower pump is connected to a tower heat exchanger via a pipeline, and the tower heat exchanger is connected to a cooler communicating with the washing tower via a pipeline.

[0013] Preferably, the cooler is connected to a spray head installed in the sewage tank via a pipe.

[0014] Preferably, the bottom of the settling zone in the tower is connected to the sewage tank via a pipe. The pipe between the settling zone in the tower and the sewage tank is connected to a deoxygenated water inlet pipe b. A water pressure sensor c and a solenoid valve e are installed in the deoxygenated water inlet pipe b. A flow sensor c and a solenoid valve f are installed on the pipe between the settling zone in the tower and the sewage tank. The flow sensor c and the solenoid valve f are located between the deoxygenated water inlet pipe b and the sewage tank.

[0015] Preferably, the outer casing is provided with a liquid level sensor a located below the settling zone in the tower, and the settling zone in the tower is provided with a liquid level sensor b.

[0016] Preferably, the tower base grid has at least two layers, and the aperture of the upper tower base grid is larger than that of the lower tower base grid.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] The catalyst settled at the bottom of the scrubbing tower is introduced into the wastewater tank to alleviate the problem of system blockage. When the catalyst blocks the pipe inlet at the bottom of the tower, the solenoid valve b is closed to cut off the pipe to the wastewater tank. Then, the solenoid valve a on the deoxygenated water inlet pipe a is opened, and the deoxygenated water backflushes the pipe inlet at the bottom of the tower to ensure that the catalyst can continuously flow into the wastewater tank. The operation is simple and the investment cost is low. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 is a flowchart provided in an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of the washing tower structure provided in an embodiment of the present invention.

[0022] Figure reference numerals: 1-Scrubber; 101-Drawout port in the tower; 102-Sieve tray in the tower; 103-Settling zone in the tower; 104-Overflow tray at the bottom of the tower; 105-Sieve tray at the bottom of the tower; 106-Drawout port at the bottom of the tower; 107-Settling zone at the bottom of the tower; 108-Double overflow tray at the bottom of the tower; 109-Bottom grid; 2-Bottom pump; 3-Bottom heat exchanger; 4-Pump in the tower; 5-Heat exchanger in the tower; 6-Cooler; 7-Wastewater tank; 8-Wastewater pump; 9-Reaction gas inlet pipe; 10 11-Reaction gas outlet pipe; 12-Deoxygenated water inlet pipe a; 13-Spray head; 14-Level sensor a; 15-Water pressure sensor b; 16-Water pressure sensor a; 17-Solenoid valve a; 18-Solenoid valve c; 19-Solenoid valve d; 20-Flow sensor a; 21-Solenoid valve b; 22-Level sensor b; 23-Flow sensor c; 24-Solenoid valve f; 25-Water pressure sensor c; 26-Solenoid valve e; 27-Deoxygenated water inlet pipe b. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] In the description of this invention, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0025] The present invention will now be described in detail with reference to Figures 1 and 2.

[0026] Example

[0027] A methanol-to-olefins (MTO) reaction gas scrubbing tower system includes a scrubbing tower 1. A wastewater tank 7 is connected to the bottom of the scrubbing tower 1 via a pipe. A deoxygenated water inlet pipe a11 is connected to the bottom of the scrubbing tower 1. A water pressure sensor a15 and a solenoid valve a16 are installed on the deoxygenated water inlet pipe a11 and the wastewater tank 7. A solenoid valve b21 and a flow sensor a20 are installed on the bottom pipe of the scrubbing tower 1, located between the deoxygenated water inlet pipe a11 and the wastewater tank 7. A reaction gas inlet pipe 9 is connected to the middle of the scrubbing tower 1, and a reaction gas outlet pipe 10 is connected to the top of the scrubbing tower 1. A wastewater pump 8 is connected to the wastewater tank 7, and the wastewater pump 8 pumps the wastewater to a water treatment unit for further treatment.

[0028] The reactant gas enters the scrubbing tower 1 through the reactant gas inlet pipe 9. The scrubbing water washes the catalyst in the reactant gas and cools it. The catalyst flows to the bottom of the scrubbing tower 1 with the scrubbing water. The catalyst settled at the bottom of the scrubbing tower 1 is introduced into the wastewater tank 7 to alleviate the problem of system blockage. When the scrubbing tower 1 is operating normally, when the flow sensor a20 monitors that the water flow rate from the bottom of the tower to the wastewater tank 7 has decreased to 50-60% of the normal flow rate, it indicates that the catalyst has blocked the pipe inlet at the bottom of the tower. At this time, the solenoid valve b21 is closed to cut off the pipe to the wastewater tank 7, and the solenoid valve a16 on the deoxygenated water inlet pipe a11 is opened. The deoxygenated water backflushes the pipe inlet at the bottom of the tower to ensure that the pipe is unobstructed and that the catalyst can flow smoothly into the wastewater tank 7. When the water pressure sensor a15 detects that the pressure drop rate in the deoxygenated water inlet pipe a11 is too fast (i.e., it has been flushed), the solenoid valve b21 is opened and the solenoid valve a16 is closed, and the catalyst delivery operation is resumed.

[0029] The scrubbing tower 1 includes an outer shell, within which a settling zone 103 is provided. A perforated tray 102 is located on one side of the settling zone 103. Below the perforated tray 102, a bottom overflow tray 104, a bottom double overflow tray 108, a bottom perforated tray 105, a bottom grid 109, and a bottom settling zone 107 are arranged sequentially. The bottom settling zone 107 is connected to a wastewater tank 7 via a pipe. The settling height of the bottom settling zone 107 is set to 5–15 meters, the settling height of the settling zone 103 is set to 1–5 meters, and the perforated tray 102 has two layers.

[0030] The washing tower 1 can be equipped with 20 to 40 trays. The lower part of the washing tower 1 can be equipped with 15 to 25 trays with sieve trays to ensure that the trays do not get clogged, reduce wear and adhesion, and extend the tower's operating cycle. The upper part of the washing tower 1 can be equipped with 5 to 15 trays with floating valves to ensure efficient separation and high operational flexibility.

[0031] A bottom outlet 106 is provided between the bottom tray 105 and the bottom grid 109. The bottom outlet 106 is connected to a bottom pump 2 via a pipeline, and the bottom pump 2 is connected to a bottom heat exchanger 3 connected to the washing tower 1 via a pipeline. The bottom water temperature is relatively high, which can directly preheat the methanol feedstock of the methanol-to-olefins unit. The feedstock methanol is generally at room temperature when it arrives at the methanol-to-olefins unit from the tank area. Setting up the bottom heat exchanger 3 to preheat the methanol can reduce energy consumption and reduce production and operating costs.

[0032] The bottom outlet 106 of the tower is connected to the deoxygenated water inlet pipe a11 via a pipeline. A water pressure sensor b14 and a solenoid valve c17 are installed in the pipeline connecting the bottom outlet 106 to the deoxygenated water inlet pipe a11. A flow sensor b18 and a solenoid valve d19 are installed in the pipeline connecting the bottom outlet 106 to the bottom pump 2. At least two bottom outlets 106 are provided, and each bottom outlet 106 is connected to the same bottom pump 2 via a pipeline. Two to four bottom outlets 106 can be provided.

[0033] When the scrubbing tower 1 is operating normally, and the flow sensor b18 detects that the inlet flow of the bottom pump 2 has decreased to 60-80% of the normal level, the solenoid valve d19 of another pipeline is opened. When the flow reaches 100% of the normal level, the original solenoid valve d19 is closed and the original solenoid valve c17 is opened for backwashing. When the water pressure sensor b14 detects that the pressure drop in the deoxygenated water inlet pipe a11 is too fast (i.e., it has been flushed smoothly), the solenoid valve c17 is closed. At this time, this pipeline is on standby, which provides high operational flexibility and low labor intensity.

[0034] The settling zone 103 in the tower is equipped with a tower outlet 101. The tower outlet 101 is connected to a tower pump 4 via a pipeline. The tower pump 4 is connected to a tower heat exchanger 5 via a pipeline. The tower heat exchanger 5 is connected to a cooler 6, which is connected to the washing tower 1, via a pipeline. One or two tower outlets 101 can be installed. The water temperature in the tower is moderate. The tower heat exchanger 5 can be directly used as a reboiler for each tower in the olefin separation process, with significant effect, low energy consumption, and low production and operating costs. The cooler 6 can be a circulating water cooler or an air cooler, and the appropriate cooling method can be selected according to the local environment and cost.

[0035] The extraction outlet 101 in the tower and the extraction outlet 106 at the bottom of the tower adopt the umbrella cap type, and the umbrella cap can be equipped with a filter screen.

[0036] The cooler 6 is connected to a spray head 12 installed in the sewage tank 7 via a pipe. Because the water temperature at the bottom of the tower is high, the water discharged into the sewage tank 7 will produce gas. The low-temperature water cooled by the cooler 6 is used to spray the sewage tank 7 to prevent the gas from entering the atmosphere, which has a good environmental protection effect and is more environmentally friendly.

[0037] The bottom of the settling zone 103 in the tower is connected to the sewage tank 7 via a pipe. A deoxygenated water inlet pipe b27 connects the settling zone 103 and the sewage tank 7. A water pressure sensor c25 and a solenoid valve e26 are installed in the deoxygenated water inlet pipe b27. A flow sensor c23 and a solenoid valve f24 are installed on the pipe between the settling zone 103 and the sewage tank 7. The flow sensor c23 and solenoid valve f24 are located between the deoxygenated water inlet pipe b27 and the sewage tank 7. When the scrubbing tower 1 is operating normally, and the flow sensor c23 detects that the water flow rate from the settling zone 103 to the sewage tank 7 has decreased to 50-60% of the normal flow rate, then the solenoid valve f24 is closed and the solenoid valve e26 is opened for backwashing. When the water pressure sensor c25 detects that the pressure drop rate in the deoxygenated water inlet pipe b27 is too fast (i.e., it has been flushed smoothly), then the solenoid valve f24 is opened and the solenoid valve e26 is closed, and sewage transport begins. The deoxygenated water can be used for backwashing when scrubbing tower 1 malfunctions, and can also be used for water supply to the scrubbing tower during start-up and shutdown, making operation more flexible, easier to control, and reducing labor intensity. The deoxygenated water inlet pipe b27 can share a single pipeline with the deoxygenated water inlet pipe a11.

[0038] A liquid level sensor a13 is installed on the outer casing below the settling zone 103 in the tower, and a liquid level sensor b22 is installed on the settling zone 103 in the tower. The liquid level sensor a13 monitors the liquid level in the settling zone 107 at the bottom of the tower, and the liquid level sensor b22 monitors the liquid level in the settling zone 103 in the tower to ensure that the liquid level meets the production requirements.

[0039] The bottom grid 109 has at least two layers, and the aperture of the upper bottom grid 109 is larger than that of the lower bottom grid 109. The two layers of bottom grid 109 at the bottom of the washing tower 1 act as baffles to buffer the fluctuations after the catalyst enters the bottom, which is beneficial to the sedimentation of the catalyst and has a significant effect.

[0040] The PLC controller can be configured to connect to flow sensors, water pressure sensors, and solenoid valves, and automatically control the opening and closing of the relevant solenoid valves based on the sensor signals to achieve automated operation.

Claims

1. A methanol to olefins reaction gas scrubbing column system comprising a scrubbing column (1), characterized in that, The bottom of the washing tower (1) is connected to a sewage tank (7) via a pipe. The pipe at the bottom of the washing tower (1) is connected to a deoxygenated water inlet pipe a (11). A water pressure sensor a (15) and a solenoid valve a (16) are installed on the deoxygenated water inlet pipe a (11). A solenoid valve b (21) and a flow sensor a (20) are installed on the pipe at the bottom of the washing tower (1) between the deoxygenated water inlet pipe a (11) and the sewage tank (7).

2. A methanol to olefins reaction gas scrubber column system according to claim 1, wherein, The washing tower (1) includes an outer shell, in which a settling zone (103) is provided. A screen tray (102) is provided on one side of the settling zone (103). Below the screen tray (102), an overflow tray (104), a double overflow tray (108), a screen tray (105), a grid (109), and a settling zone (107) are arranged in sequence.

3. A methanol to olefins reaction gas scrubber column system according to claim 2, wherein, A bottom extraction port (106) is provided between the bottom sieve tray (105) and the bottom grid (109). The bottom extraction port (106) is connected to a bottom pump (2) through a pipe. The bottom pump (2) is connected to a bottom heat exchanger (3) that communicates with the washing tower (1) through a pipe.

4. A methanol to olefins reaction gas scrubber column system according to claim 3, wherein, The bottom outlet (106) of the tower is connected to the deoxygenated water inlet pipe a (11) through a pipe. A water pressure sensor b (14) and a solenoid valve c (17) are installed in the pipe connecting the bottom outlet (106) of the tower to the deoxygenated water inlet pipe a (11). A flow sensor b (18) and a solenoid valve d (19) are installed in the pipe connecting the bottom outlet (106) of the tower to the bottom pump (2).

5. A methanol to olefins reaction gas scrubber column system according to claim 4, wherein, At least two bottom extraction ports (106) are provided, and each bottom extraction port (106) is connected to the same bottom pump (2) via a pipeline.

6. A methanol to olefins reaction gas scrubber column system according to claim 2, wherein, The settling zone (103) in the tower is provided with a tower extraction outlet (101), the tower extraction outlet (101) is connected to a tower pump (4) through a pipe, the tower pump (4) is connected to a tower heat exchanger (5) through a pipe, and the tower heat exchanger (5) is connected to a cooler (6) that communicates with the washing tower (1) through a pipe.

7. A methanol to olefins reaction gas scrubber column system according to claim 6, wherein, The cooler (6) is connected to a spray head (12) installed in the sewage tank (7) via a pipe.

8. A methanol to olefins reaction gas scrubber column system according to claim 2, wherein, The bottom of the settling zone (103) in the tower is connected to the sewage tank (7) through a pipe. The pipe between the settling zone (103) in the tower and the sewage tank (7) is connected to a deoxygenated water inlet pipe b (27). A water pressure sensor c (25) and a solenoid valve e (26) are installed in the deoxygenated water inlet pipe b (27). A flow sensor c (23) and a solenoid valve f (24) are installed on the pipe between the settling zone (103) in the tower and the sewage tank (7). The flow sensor c (23) and the solenoid valve f (24) are located between the deoxygenated water inlet pipe b (27) and the sewage tank (7).

9. A methanol to olefins reaction gas scrubber column system according to claim 2, wherein, The outer shell is provided with a liquid level sensor a (13) located below the settling zone (103) in the tower, and a liquid level sensor b (22) is provided on the settling zone (103) in the tower.

10. A methanol to olefins reaction gas scrubber column system according to claim 2, wherein, The tower base grid (109) is provided with at least two layers, and the aperture of the upper tower base grid (109) is larger than the aperture of the lower tower base grid (109).

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