Methanol to olefin quench tower catalyst washing device

Abstract

The utility model discloses a kind of methanol to olefin quench tower catalyst washing devices, including quench tower, the quench tower includes bottom water washing circulation, washing water is by washing water inlet into the washing water nozzle in tower, by tower bottom washing water outlet through bottom circulation pump return the quench tower, it is characterized in that, the device also includes lye storage tank and hydrocyclone, the lye outlet of the lye storage tank bottom is connected by lye pump the washing water inlet described;The bottom circulation pump outlet is connected to hydrocyclone by pipeline, catalyst is discharged from bottom after liquid-solid separation in hydrocyclone, washing water is returned the washing water inlet of the quench tower from top, or discharge to sewage treatment device.The device can effectively increase the washing effect of quench tower bottom catalyst, improve catalyst removal efficiency.

Description

Technical Field

[0001] This utility model relates to a methanol-to-olefins (MTO) plant, specifically to a catalyst washing device for the quench tower in a methanol-to-olefins plant. Background Technology

[0002] Methanol to olefins (MTO) uses methanol as a raw material. In a fast fluidized bed reactor, superheated methanol reacts with the active sites of the catalyst to produce product gas, mainly ethylene and propylene. The product gas then enters a quench tower to remove the superheat and is further separated and purified.

[0003] In the methanol-to-olefins (MTO) process, due to process constraints, the product gas entering the quench tower often contains some catalyst. The quench tower, as an essential piece of equipment for removing superheat from the product gas, washing catalyst dust, and neutralizing acidic substances, is typically designed with a three-stage circulating water wash: a bottom stage for removing superheat and washing the catalyst; a middle stage for alkaline washing with NaOH solution to neutralize acidic substances; and an upper stage for adjusting the pH to weakly alkaline through water washing. However, in actual operation, the bottom washing agent in the quench tower is water, resulting in poor catalyst washing at the bottom. This leads to catalyst being carried to the upper middle and even downstream systems. During the alkaline washing process in the middle, aldehydes and ketones in the product gas easily undergo condensation reactions under alkaline conditions to form polymers. These polymers can adhere to the catalyst, easily clogging the tray sieves and, in severe cases, even clogging the upper trays, affecting the normal operation of the quench tower and posing a threat to the safe and stable operation of the MTO unit. The current solution is to increase the amount of bottom circulating washing water and add a detergent dispersant to the middle circulation. In fact, the dispersant has been effective to some extent, but the washing effect at the bottom has not changed much. Too much catalyst is still carried to the middle and cannot be effectively discharged, which leads to frequent blockages in the trays and external drainage pipelines. Summary of the Invention

[0004] The purpose of this invention is to provide a catalyst washing device for the quench tower of an MTO unit, which solves problems such as poor catalyst washing effect and tray blockage in the MTO quench tower, improves the catalyst washing effect, and effectively prevents the catalyst from entering the downstream system.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A catalyst washing device for a methanol-to-olefins quench tower includes a quench tower with a bottom water washing circulation system. Washing water enters a washing water nozzle inside the tower through a washing water inlet and returns to the quench tower via a bottom circulation pump from the bottom washing water outlet. The device further includes an alkali storage tank and a hydrocyclone separator. The alkali outlet at the bottom of the alkali storage tank is connected to the washing water inlet via an alkali pump. The outlet of the bottom circulation pump is connected to the hydrocyclone separator via a pipeline. After liquid-solid separation in the hydrocyclone separator, the catalyst is discharged from the bottom, and the washing water returns from the top to the washing water inlet of the quench tower or is discharged to a wastewater treatment device.

[0007] Furthermore, the alkaline solution is stored in the alkaline solution storage tank, and the alkaline solution is preferably a NaOH solution with a mass percentage concentration of 30%.

[0008] Furthermore, the device includes a second inlet and a second nozzle inside the quench tower, and also includes a dispersant storage tank. The dispersant outlet at the bottom of the dispersant storage tank is connected to the second inlet via a dispersant injection pump, and the dispersant enters the second nozzle through the second inlet.

[0009] Furthermore, the dispersant is selected from silicate dispersants, phosphate dispersants, oxide dispersants, etc., preferably phosphate dispersants, such as sodium hexametaphosphate, sodium polyphosphate, potassium tripolyphosphate, etc.

[0010] Preferably, the second nozzle is located above the washing water nozzle.

[0011] Furthermore, the washing water inlet and the second inlet are connected by a connecting pipe, and the connecting pipe is equipped with an alkaline solution and dispersant switching valve.

[0012] Furthermore, the washing water nozzle and the second nozzle are made of stainless steel and include a set of spray heads. Preferably, the spray heads are evenly distributed on the cross-section of the quench tower.

[0013] Furthermore, the quench tower includes a product gas inlet at the bottom, a product gas outlet at the top, and an upper water washing circulation and a middle water washing circulation.

[0014] Beneficial Effects: This invention modifies the type of detergent by adding a 30% NaOH solution during the bottom water washing cycle of the MTO unit's quench tower to wash the lower layer of catalyst. This creates a highly viscous alkaline detergent solution that effectively washes away the catalyst from the product gas and removes acidic gases. To prevent catalyst clogging of the bottom trays and nozzles, a second nozzle, a dispersant storage tank, and a pump are added to the quench tower for dispersant injection (the injection of NaOH solution and dispersant into the washing water nozzles can be switched depending on nozzle clogging). Simultaneously, the device separates the washed catalyst into solid and liquid phases using an added hydrocyclone, separating the waste catalyst from the washing water. The separated washing water can be returned to the quench tower or discharged to control the bottom liquid level of the quench tower. This device effectively increases the washing effect on the catalyst at the bottom of the quench tower, improves catalyst removal efficiency, and prevents catalyst from entering the system and causing a series of problems. The separated catalyst is discharged from the bottom of the hydrocyclone and bagged for hazardous waste disposal. Attached Figure Description

[0015] Figure 1 is a schematic diagram of the catalyst washing device for the MTO quench tower of this utility model;

[0016] Among them, 1. Quenching tower, 2. Hydrocyclone separator, 3. Alkali storage tank, 4. Dispersant storage tank, 5. Bottom circulation pump, 6. Alkali pump, 7. Dispersant injection pump, 8. Alkali and dispersant switching valve. Detailed Implementation

[0017] The technical solution of this utility model will be further described in detail below through specific embodiments. However, it should be noted that the following embodiments are only used to describe the content of the invention and do not constitute a limitation on the protection scope of this utility model.

[0018] refer to Figure 1 This is a schematic diagram of the catalyst washing device for the quench tower of the MTO unit according to this utility model. The MTO unit quench tower 1 includes a product gas inlet at the bottom, a product gas outlet at the top, and upper, middle, and bottom water washing circulation sections. The bottom water washing circulation section includes a washing water input pipe. The washing water enters the washing water nozzle inside the tower through the washing water inlet and returns to the quench tower 1 through the bottom washing water outlet via the bottom circulation pump 5. The bottom water washing circulation section is mainly used to wash and remove solid catalyst entrained in the product gas. The middle and upper water washing circulation sections are used to neutralize excess acidic substances in the product gas.

[0019] The device also includes an alkali storage tank 3, an alkali pump 6, a dispersant storage tank 4, and a dispersant injection pump 7, and a hydrocyclone separator 2. A second inlet and a second nozzle are provided in the quench tower 1, with the second nozzle positioned above the wash water nozzle. The wash water inlet and the second inlet are connected by a pipe, and an alkali-dispersant switching valve 8 is installed on the connecting pipe. The alkali outlet at the bottom of the alkali storage tank 3 is connected to the wash water inlet via the alkali pump 6, allowing the alkali to enter the wash water nozzle. The dispersant outlet at the bottom of the dispersant storage tank 4 is connected to the second inlet via the dispersant injection pump 7, allowing the dispersant to enter the second nozzle. An additional pipe is added to the outlet of the bottom circulation pump 5, connecting to the hydrocyclone separator 2. After liquid-solid separation in the hydrocyclone separator 2, the catalyst is discharged from the bottom, and the wash water returns from the top to the wash water inlet of the quench tower 1, or is discharged to a wastewater treatment device. The connecting pipes of the equipment include the necessary valves and fittings.

[0020] The washing water nozzle and the second nozzle are made of stainless steel and are contained in a set of spray heads that are evenly distributed on the cross-section of the quench tower 1.

[0021] The catalyst washing device for the quench tower of the MTO unit of this utility model has the following characteristics:

[0022] (1) In the bottom water washing circulation of the original quench tower, this device includes two sets of nozzles. A second nozzle is added above the original washing water nozzle, and an alkali storage tank and a dispersant storage tank, as well as corresponding pumps, valves, etc. are added. The alkali mainly enters the washing water nozzle, and the dispersant mainly enters the second nozzle. As a washing agent, it is added to the washing water to wash and remove the catalyst entrained in the product gas.

[0023] (2) Add an alkaline cleaning process to the existing washing water circulation process. Inject a 30% NaOH solution into the washing water to increase the viscosity of the washing water and enhance the washing effect on the catalyst.

[0024] (3) Add a second nozzle and add a dispersant circulation washing process. The dispersant can peel off the deposits that have been deposited on the trays and other places, and can combine with the catalyst powder, making it less likely to deposit and form scale on the trays and other places. At the same time, the second nozzle is placed above the washing water nozzle. Since the alkaline solution can easily cause polymers to stick to the catalyst and cause blockage, it can prevent the catalyst from causing blockage of the trays and nozzles during the washing process.

[0025] (4) The washing water inlet and the second inlet are connected by a pipe and a switching valve is installed. If necessary, the washing water nozzle or the second nozzle can be used to switch between washing with alkaline solution or dispersant.

[0026] (5) Add a hydrocyclone separator to the device (or integrate the existing equipment in the MTO device) to separate the catalyst in part of the washing water, reduce the solid content in the washing water, and return the clean washing water from the top to the quench tower to replace the washing water or discharge it to the sewage treatment plant, and control the liquid level at the bottom of the quench tower.

Claims

1. A catalyst washing device for a methanol-to-olefins quench tower, comprising a quench tower, wherein the quench tower includes a bottom water washing circulation system, and washing water enters a washing water nozzle inside the tower through a washing water inlet, and returns to the quench tower through a bottom circulation pump from the bottom washing water outlet, characterized in that... The device also includes an alkali storage tank and a hydrocyclone separator. The alkali outlet at the bottom of the alkali storage tank is connected to the washing water inlet via an alkali pump. The outlet of the bottom circulation pump is connected to the hydrocyclone separator via a pipeline. After liquid-solid separation in the hydrocyclone separator, the catalyst is discharged from the bottom, and the washing water is returned from the top to the washing water inlet of the quench tower, or discharged to the wastewater treatment device.

2. The methanol to olefins quench column catalyst washing apparatus according to claim 1, characterized in that, The alkaline storage tank contains a 30% NaOH solution by mass percentage.

3. The methanol to olefins quench column catalyst washing apparatus according to claim 1, characterized in that, The device includes a second inlet and a second nozzle inside the quench tower, and also includes a dispersant storage tank. The dispersant outlet at the bottom of the dispersant storage tank is connected to the second inlet via a dispersant injection pump, and the dispersant enters the second nozzle through the second inlet.

4. The methanol to olefins quench column catalyst washing apparatus according to claim 3, characterized in that, The dispersant is a silicate dispersant, a phosphate dispersant, or an oxide dispersant.

5. The methanol to olefins quench column catalyst washing apparatus according to claim 3, characterized in that, The second nozzle is located above the washing water nozzle.

6. The methanol to olefins quench column catalyst washing apparatus according to claim 3, characterized in that, The washing water inlet and the second inlet are connected by a connecting pipe, and the connecting pipe is equipped with an alkaline solution and dispersant switching valve.

7. The catalyst washing device for a methanol-to-olefins quench tower according to claim 3, characterized in that, The washing water nozzle and the second nozzle are made of stainless steel and include a set of spray heads, which are evenly distributed on the cross-section of the quench tower.

8. The methanol to olefins quench column catalyst washing apparatus of claim 1, wherein, The quench tower includes a product gas inlet at the bottom, a product gas outlet at the top, and an upper water washing circulation and a middle water washing circulation.

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