Oil-containing waste alkali liquor treatment system for MTO (methanol to olefin) device

Abstract

The oil-containing waste alkali liquor treatment system of the MTO device comprises an alkaline washing tower, a waste alkali liquor blending burner and a boiler, the alkaline washing tower is connected with a waste alkali liquor buffer tank, the output end of the waste alkali liquor buffer tank is connected with a booster pump, the booster pump is connected with the boiler through the waste alkali liquor blending burner, a heater is arranged in the waste alkali liquor buffer tank, and the boiler is connected with the waste alkali liquor blending burner. Steam is conveyed into the waste alkali liquor blending burner, and oil-containing waste alkali liquor discharged from the alkaline washing tower enters the waste alkali liquor blending burner to be mixed with the steam and then jetted into the boiler. The oil-containing waste alkali liquor is directly conveyed to the waste alkali liquor buffer tank to be heated, then is pressurized by the pressure pump to the waste alkali liquor blending burner to be mixed with steam, and then is sprayed into the boiler to be blended and burnt, and the oil-containing waste alkali liquor is not in contact with air in the conveying process; therefore, the problem of blockage of equipment such as pipelines, valves and pumps caused by butter precipitation and coalescence is prevented, the maintenance and cleaning cost of the equipment is reduced, and the blending combustion effect of the oil-containing waste alkali liquid is improved after the butter is mixed with steam.

Description

Technical Field

[0001] The utility model belongs to the technical field of treatment of oily waste alkali liquor of an MTO device, and specifically relates to a treatment system of oily waste alkali liquor of an MTO device. Background Art

[0002] In an MTO (methanol to olefins) unit, the primary function of the water / caustic scrubber is to remove acidic gases, such as carbon dioxide, from the reaction gases. However, during the caustic scrubbing process, a large amount of butter is easily generated. This butter is primarily composed of aromatic compounds, aldehydes and ketones, carboxylates, benzene, emulsified oil primarily composed of dimethylol, floating oil, and hydrocarbon polymers.

[0003] To prevent butter from clogging the caustic wash tower and affecting production efficiency, the current method for removing butter from the tower is to use caustic solution to clean the tower trays based on the pressure differential within the tower. This dissolves the butter adhering to the tower components in the caustic solution, which is then discharged with the caustic solution. Generally, fresh oily waste caustic solution discharged from the tower is approximately 50°C, pale yellow, and translucent. It exhibits excellent fluidity, with a viscosity between 4.4 and 8.6 mPa·s. Once discharged, the temperature of the oily waste caustic solution drops to 25°C, causing the butter's solubility to decrease. Upon contact with oxygen in the air, the butter precipitates and aggregates into red lumps, either suspended in the waste caustic solution or adhering to the container walls. At this point, the viscosity of the waste caustic solution ranges from 45.4 to 89.6 mPa·s, while the precipitated butter has a viscosity of 1136 to 2670 mPa·s. Therefore, in each link of the treatment of oily waste alkali liquid, butter will precipitate, which will then clog pipes, valves, pumps and other treatment equipment, bringing many problems to the comprehensive treatment of oily waste alkali liquid.

[0004] Furthermore, the presence of volatile organic compounds (VOCs) in oily waste lye increases the difficulty of VOC management. Furthermore, oily waste lye also has high oil content, high salt content, high chemical oxygen demand (COD), and high ammonia nitrogen content, making subsequent wastewater treatment extremely complex. Utility Model Content

[0005] In order to solve the above technical problems, the purpose of the utility model is to provide a system for treating oily waste alkali liquor of an MTO device, which adopts a closed oxygen-free heating transportation and spray blending combustion method to achieve thorough and efficient cleaning of the oily waste alkali liquor of the MTO device.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] A system for treating oily waste alkali liquor of an MTO device comprises an alkali washing tower, a waste alkali liquor blending burner and a boiler, wherein the alkali washing tower is connected to a waste alkali liquor buffer tank, the waste alkali liquor buffer tank is connected to a pressure pump, the pressure pump is connected to the boiler via the waste alkali liquor blending burner, a heater is provided inside the waste alkali liquor buffer tank, steam is transported in the waste alkali liquor blending burner, and the oily waste alkali liquor discharged from the alkali washing tower enters the alkali liquor blending burner, is mixed with the steam, and is then ejected into the boiler.

[0008] Furthermore, the alkali washing tower is connected to the waste alkali liquid buffer tank through a first closed pipe, and a filter is connected in series to the first closed pipe.

[0009] Furthermore, a nitrogen valve is provided on the top of the waste alkali liquid buffer tank.

[0010] Furthermore, one end of the waste alkali liquor blending burner is connected to a steam pipe, and the steam is transported into the waste alkali liquor blending burner through the steam pipe and mixed with the oil-containing waste alkali liquor before being sprayed into the boiler.

[0011] Furthermore, the waste alkali liquid buffer tank is connected to the booster pump through a second closed pipe, a first electrically controlled valve is connected in series to the second closed pipe, and the booster pump is connected to the waste alkali liquid blender through a third closed pipe, a second electrically controlled valve is connected in series to the third closed pipe.

[0012] Furthermore, a third electrically controlled valve is connected in series to one end of the steam pipeline close to the waste alkali liquor blending burner.

[0013] Furthermore, the steam pipe is connected to the second sealed pipe through a fourth sealed pipe, and a fourth electrically controlled valve is connected in series to the fourth sealed pipe.

[0014] Furthermore, nitrogen is input into one end of the nitrogen valve.

[0015] Furthermore, the heater is a coil heater.

[0016] Due to the adoption of the above technical solution, the utility model has the following advantages and effects:

[0017] (1) The utility model provides a system for treating oily waste alkali liquor of an MTO device, which utilizes the existing fly ash boiler of a coal chemical plant without the need to build a new co-firing boiler. The oily waste alkali liquor is transported to a waste alkali liquor buffer tank through a closed pipeline for heating and then pressurized by a pressure pump to a waste alkali liquor co-firing device for mixing with steam and then injected into the boiler for co-firing. The oily waste alkali liquor does not come into contact with air during transportation, thereby preventing the precipitation and aggregation of butter from causing blockage of pipelines, valves, pumps and other equipment, thereby reducing the maintenance and cleaning costs of the equipment.

[0018] (2) The utility model provides a system for treating oily waste alkali liquor of an MTO device. Since the oily waste alkali liquor has good fluidity in a high temperature environment and has a low calorific value, it can fully utilize the thermal energy of the boiler by co-firing with the boiler, thereby reducing the additional fuel consumption required for separate co-firing. Moreover, by reasonably adjusting the flow rate and pressure of the steam at the inlet of the waste alkali liquor co-firing device, it can be ensured that the waste alkali liquor can fully participate in the co-firing, thereby improving the co-firing effect of the oily waste alkali liquor, further optimizing the composition of the flue gas, and facilitating the subsequent exhaust gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the utility model.

[0020] The accompanying drawings are numbered as follows: 1-alkali washing tower, 2-waste alkali liquid buffer tank, 3-nitrogen valve, 4-pressure pump, 5-waste alkali liquid blending device, 6-boiler, 7-filter, 8-first electric control valve, 9-second electric control valve, 10-third electric control valve, 11-fourth electric control valve, 12-nitrogen, 13-steam. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings to describe the embodiments of the present invention in detail so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0022] like Figure 1 The utility model discloses a system for treating oily waste alkali liquor of an MTO device, comprising an alkali washing tower 1 and a boiler 6. The alkali washing tower 1 is connected to a waste alkali liquor buffer tank 2. The output end of the waste alkali liquor buffer tank 2 is connected to a pressure pump 4. The pressure pump 4 is connected to the boiler 6 via a waste alkali liquor blending burner 5. A heater is provided inside the waste alkali liquor buffer tank 2. Steam 13 is transported into the waste alkali liquor blending burner 5. The oily waste alkali liquor discharged from the alkali washing tower passes through the pressure pump 4 into the alkali liquor blending burner 5, is mixed with the steam 13, and is then injected into the boiler for blending burner.

[0023] Specifically, the existing waste alkali liquid discharge interface of the alkali washing tower 1 is led out, and the waste alkali liquid discharge interface after being led out, the waste alkali liquid buffer tank 2, the pressure pump 4 and the waste alkali liquid blender 5 are all connected through a closed pipeline, and the output end of the waste alkali liquid blender 5 is connected to the furnace of the boiler 6.

[0024] A coil heater, preferably an electric heating wire, is installed at the bottom of the waste alkali liquid buffer tank 2. The coil heater maintains the waste alkali liquid in the waste alkali liquid buffer tank 2 at a temperature of approximately 50°C, facilitating its transfer to the pressure pump 4 for pressurization. When the temperature in the furnace reaches above 1000°C, the oily waste alkali liquid is completely evaporated and co-combusted, ultimately converting it into CO2, H2O, and nitrogen oxides, which enter the exhaust gas treatment system along with the flue gas. Small amounts of salt solids generated by the co-combustion enter the tailings system and, preferably, a pulverized coal furnace, along with the fly ash.

[0025] The oily waste alkali liquid discharged from the alkali washing tower 1 is first heated in the waste alkali liquid buffer tank 2 and then transported by the pressure pump 4 to the waste alkali liquid co-incinerator 5 at the boundary of the boiler 6. The waste alkali liquid co-incinerator 5 is assisted by steam 13 to perform an atomization operation, atomizing the oily waste alkali liquid and then transporting it to the boiler 6 for co-incineration treatment. The waste alkali liquid co-incinerator 5 is preferably a spray gun.

[0026] Furthermore, the sealed pipe includes a first sealed pipe, a second sealed pipe, a third sealed pipe, and a fourth sealed pipe. The alkali washing tower 1 is connected to the waste alkali liquid buffer tank 2 through the first sealed pipe. The first sealed pipe is connected in series with a Y-type filter 7. The installation of the Y-type filter 7 can prevent the agglomerated butter and other large particles from entering the waste alkali liquid buffer tank 2.

[0027] Furthermore, a nitrogen valve 3 is provided at the top of the waste alkali liquid buffer tank 2, with nitrogen 12 input at one end. Because the oily waste alkali liquid in the waste alkali liquid buffer tank 2 is easily volatile, the inert gas nitrogen 12 is used to seal the tank. The nitrogen valve 3 only allows nitrogen 12 to enter, but does not exhaust. When the pressure in the waste alkali liquid buffer tank 2 decreases, the nitrogen valve 3 opens to replenish nitrogen 12 into the waste alkali liquid buffer tank 2, preventing negative pressure in the waste alkali liquid buffer tank 2. When the pressure in the waste alkali liquid buffer tank 2 increases, the nitrogen valve 3 discharges some nitrogen 12 to prevent excessive pressure. The nitrogen valve 3 is preferably a nitrogen slightly positive pressure sealing valve.

[0028] Furthermore, a steam pipe 13 is connected to one end of the waste alkali liquor blending burner 5. Steam 13 is transported into the waste alkali liquor blending burner 5 through the steam pipe to be mixed with the oil-containing waste alkali liquor. By adjusting the flow rate and pressure of the steam 13 in the steam pipe to match the flow rate of the oil-containing waste alkali liquor, the spray distance and atomization effect set by the waste alkali liquor blending burner 5 are achieved, ensuring that the oil-containing waste alkali liquor can be fully blended and burned in the furnace.

[0029] Furthermore, the waste alkali liquid buffer tank 2 is connected to the booster pump 4 via a second sealed pipe, to which a first electrically controlled valve 8 is connected in series, and the flow rate of the oily waste alkali liquid entering the waste alkali liquid buffer tank 2 is controlled by the first electrically controlled valve 8. The booster pump 4 is connected to the waste alkali liquid blender 5 via a third sealed pipe, to which a second electrically controlled valve 9 is connected in series, and the flow rate of the oily waste alkali liquid entering the waste alkali liquid blender 5 is controlled by the second electrically controlled valve 9.

[0030] Furthermore, a third electrically controlled valve 10 is connected in series to one end of the steam pipe close to the waste alkali liquor blending burner 5. The flow rate and pressure of the steam 13 entering the waste alkali liquor blending burner 5 are controlled by the third electrically controlled valve 10.

[0031] Furthermore, in order to facilitate cleaning of the sealed pipe, the steam pipe is connected to the second sealed pipe through a fourth sealed pipe, and the fourth sealed pipe is serially connected with a fourth electric control valve 11. The fourth electric control valve 11 controls steam 13 to enter the sealed pipe for pipe cleaning.

[0032] The utility model provides a system for treating oily waste alkali liquor of an MTO device. When the oily waste alkali liquor is mixed and burned in a boiler 6, the first electric control valve 8 and the pressure pump 4 are closed first, and then the third electric control valve 10 is closed. Then, the fourth electric control valve 11 is opened and steam is started for purging and cleaning. After the steam purging lasts for 30 seconds, the fourth electric control valve 11 is closed, and the waste alkali liquor mixing burner 5 is withdrawn from the boiler 6.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for treating oily waste alkali liquor of an MTO unit, characterized by: The invention comprises an alkali washing tower (1), a waste alkali liquor blending burner (5) and a boiler (6); the alkali washing tower (1) is connected to a waste alkali liquor buffer tank (2); the waste alkali liquor buffer tank (2) is connected to a pressure pump (4); the pressure pump (4) is connected to the boiler (6) via the waste alkali liquor blending burner (5); a heater is provided inside the waste alkali liquor buffer tank (2); steam (13) is transported into the waste alkali liquor blending burner (5); the oily waste alkali liquor discharged from the alkali washing tower (1) enters the alkali liquor blending burner (5), is mixed with the steam (13), and then is sprayed into the boiler (6).

2. The system for treating oily waste alkali liquor of an MTO device according to claim 1, characterized in that: The alkali washing tower (1) is connected to the waste alkali solution buffer tank (2) via a first sealed pipe, and a filter (7) is connected in series to the first sealed pipe.

3. The system for treating oily waste alkali liquor of an MTO device according to claim 2, characterized in that: A nitrogen valve (3) is provided on the top of the waste alkali solution buffer tank (2).

4. The system for treating oily waste alkali liquor of an MTO device according to claim 2 or 3, characterized in that: One end of the waste alkali liquor blending burner (5) is connected to a steam pipe, and the steam (13) is transported into the waste alkali liquor blending burner (5) through the steam pipe to be mixed with the oil-containing waste alkali liquor.

5. The system for treating oily waste alkali liquor of an MTO device according to claim 4, characterized in that: The waste alkali liquid buffer tank (2) is connected to the pressure pump (4) via a second sealed pipe, a first electric control valve (8) is connected in series to the second sealed pipe, and the pressure pump (4) is connected to the waste alkali liquid blending device (5) via a third sealed pipe, a second electric control valve (9) is connected in series to the third sealed pipe.

6. The system for treating oily waste alkali liquor of an MTO device according to claim 5, characterized in that: A third electric control valve (10) is connected in series to one end of the steam pipeline close to the waste alkali liquor blending burner (5).

7. The system for treating oily waste alkali liquor of an MTO device according to claim 6, characterized in that: The steam pipeline is connected to the second sealed pipeline through a fourth sealed pipeline, and a fourth electric control valve (11) is connected in series to the fourth sealed pipeline.

8. The system for treating oily waste alkali liquor of an MTO device according to claim 3, characterized in that: Nitrogen is input into one end of the nitrogen valve (3).

9. The system for treating oily waste alkali liquor of an MTO device according to claim 1, characterized in that: The heater is a coil heater.

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