Oil phase separation and dynamic oil discharge system of wastewater stripping tank of mto device

Abstract

This utility model discloses an oil phase separation and oil discharge system for a stripping tower reflux tank in an MTO (Metal-Oxide-Transfer) unit. The system includes a wastewater stripping tower, with its top connected to the reflux tank via a first exhaust pipe. A purified water drain pipe is located at the bottom of the wastewater stripping tower. A second exhaust pipe for discharging non-condensable gases is connected to the top of the reflux tank, and a reflux tank condensate drain line is connected to the bottom of the reflux tank. To achieve real-time online monitoring and adjustment of oil discharge, the oil phase separation and dynamic oil discharge system also includes a COD monitor, an oil collection pipe, and an oil discharge regulating valve. The COD monitor is connected to the purified water drain pipe and to a control system. The oil collection pipe is located inside the reflux tank, with its top end below the highest liquid level in the reflux tank. The reflux tank condensate drain line is connected to the oil collection pipe, and its outlet is connected to a waste oil recovery tank. The oil discharge regulating valve is connected to the control system. Therefore, when the COD value of the supplied purified water exceeds the specified value, oil can be discharged in real time.

Description

Technical Field

[0001] This application relates to the field of chemical equipment technology, and in particular to an oil phase separation and dynamic oil discharge system for a wastewater stripping tower reflux tank in an MTO unit. Background Technology

[0002] In a methanol-to-olefins (MTO) unit, methanol feedstock reacts exothermically in direct contact with a high-temperature regenerated catalyst from a regenerator within the reactor. The reaction gas contains a large amount of water vapor. After the catalyst entrained in the reaction gas is removed by a cyclone separator, the reaction gas is cooled by a heat exchanger and sent to a quench tower for further cooling and catalyst washing. It then passes through a water washing tower for further cooling and condensation of the water vapor in the reaction gas and for washing the oxides (methanol, dimethyl ether, etc.) in the reaction gas. The wash water drawn from the bottom of the water washing tower contains trace amounts of methanol, dimethyl ether, and olefin components, which need to be stripped for recovery. The stripping gas from the top of the wastewater stripping tower is cooled by heat exchange and then enters the reflux tank. The purified water after stripping is sent outside the unit. During the cooling process, some components of the stripping gas (such as light hydrocarbons) may condense to form an oil phase. Therefore, after cooling, the stripping gas enters the reflux pump and is separated into gas and liquid phases. The condensed oil phase floats on top of the liquid phase. Then, the non-condensable gas at the top of the reflux tank is returned to the reactor, while the separated liquid is returned to the stripping tower by the reflux pump. At this time, the oil phase in the reflux tank needs to be discharged in time. If the oil is not discharged in time or incompletely, the oil phase floating on top of the liquid will be returned to the stripping tower by the liquid pump, which may affect the treatment effect of the purified water.

[0003] Current existing technologies for draining oil phase from reflux tanks include a local level gauge installed at the top of the tank, with a drain line connected to the top of the level gauge via a tee. The end of the drain line is connected to a tonne container for draining oil, and a control valve is installed on the drain line to control the draining process. The flow diagram is shown below. Figure 1 As shown.

[0004] Currently, when the oil phase in the reflux tank is discharged through this oil discharge structure, the liquid level in the reflux tank needs to be above 100%, and the control valve on the oil discharge pipeline needs to be manually opened before the oil phase can be discharged to the ton container. At this time, the operator may not be able to accurately control the timing of oil discharge, resulting in incomplete discharge of the oil phase. Subsequently, when the oil phase flows back to the stripping tower with the liquid, it will affect the water quality of the subsequent purified water. Utility Model Content

[0005] This application provides an oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit, which solves the problem that incomplete oil discharge in existing methods can affect the quality of subsequent purified water.

[0006] This utility model embodiment provides an oil phase separation and dynamic oil discharge system for a wastewater stripping tower reflux tank in an MTO (Metal-Oxide-Transfer) unit, comprising: a wastewater stripping tower, the exhaust port at the top of the wastewater stripping tower being connected to the reflux tank via a first exhaust pipe, a condenser being installed on the first exhaust pipe, a purified water discharge pipe being installed at the drain port at the bottom of the wastewater stripping tower, a second exhaust pipe for discharging non-condensable gases being installed at the top of the reflux tank, a reflux tank pressure control valve connected to a control system being installed on the second exhaust pipe, and a reflux tank condensate discharge pipeline being connected to the bottom of the reflux tank, characterized in that it further comprises:

[0007] A COD monitor is connected to the purified water drain pipe, and the COD monitor is connected to the control system.

[0008] The oil collecting pipe is vertically installed inside the return tank. The top of the oil collecting pipe is lower than the top of the return tank. The inlet end of the return tank's condensate drain line is connected to the lower oil outlet of the oil collecting pipe. The outlet end of the return tank's condensate drain line is connected to a waste oil recovery tank.

[0009] The oil drain regulating valve is installed on the condensate drain line of the return tank and is connected to the control system.

[0010] Preferably, the top of the oil collecting pipe is located at 72%-75% of the highest liquid level in the return tank.

[0011] Preferably, a check valve is installed on the condensate drain line of the reflux tank.

[0012] Preferably, a first field gate valve, a drain sight glass, and a second field gate valve are sequentially arranged downstream of the check valve and between the drain regulating valve.

[0013] Preferably, the condensate drain line of the return tank is connected to the waste oil recovery tank via the inlet line of the waste oil recovery tank.

[0014] Preferably, a steam purging line is also connected to the condensate drain line of the return tank, and the steam purging line is located upstream of the check valve.

[0015] Preferably, the steam purging pressure of the steam purging pipeline is not less than 0.5 MPa.

[0016] Preferably, a third field gate valve is also provided upstream of the check valve, and the steam purging pipeline is located between the check valve and the third field gate valve.

[0017] The beneficial effects of this utility model are:

[0018] This utility model discloses an oil phase separation and dynamic oil discharge system for the reflux tank of a wastewater stripping tower in an MTO (Metal-Oxide-Transfer) unit. By monitoring the COD (Chemical Oxygen Depletion) indicator connected to the purified water discharge pipe, the system can determine the water quality of the purified water discharged from the wastewater stripping tower. If the COD value of the delivered purified water is lower than the system's set value, it indicates that oil discharge from the reflux tank is unnecessary. However, if the COD value of the delivered purified water exceeds the set value, it may indicate the presence of a high concentration of organic pollutants (including emulsified oil or dissolved organic matter) in the water. In this case, the reflux tank needs to be discharged promptly. The pressure inside the reflux tank is set via a pressure control valve, and then... When the liquid level in the reflux tank exceeds the top of the oil collecting pipe, the oil phase at the top of the liquid surface is pushed down into the oil collecting pipe under the static pressure of the oil phase. At the same time, the control system can control the oil discharge regulating valve on the reflux tank discharge pipeline to be in the open state. After that, the oil phase is discharged to the waste oil recovery tank after passing through the oil collecting pipe and the reflux tank discharge pipeline in sequence. In summary, the oil phase separation and dynamic oil discharge system of the wastewater stripping tower reflux tank of the MTO unit disclosed in this utility model can realize real-time dynamic online monitoring of the oil discharge process. When the COD value of the external purified water exceeds the index value, oil can be discharged in real time. The existing oil discharge structure has problems such as incomplete oil discharge, which leads to excessive oil content in the external purified water. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments of this utility model or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the oil discharge process for draining oil from a tonne drum connected to a local level gauge, as described in the background art.

[0021] Figure 2 This is a flowchart of an oil phase separation and dynamic oil discharge system for a wastewater stripping tower reflux tank in an MTO (Metal-Oxide-Transfer) unit according to this utility model.

[0022] Icons: 1. Wastewater stripping tower; 2. Return tank pressure control valve; 3. Return tank; 4. Oil collection pipe; 5. Return tank local level gauge; 6. Return tank condensate drain line; 7. Check valve; 8. Oil drain sight glass; 9. Oil drain regulating valve; 10-1. First field gate valve; 10-2. Second field gate valve; 11. Waste oil recovery tank inlet line; 12. Steam purging line; 13. COD monitor; 14. Condenser; 15. Purified water drain pipe; 16. Waste oil recovery tank; 17. Third field gate valve. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model.

[0024] This utility model provides an oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO (Metal-Oxide-Transfer) unit, such as... Figure 2 As shown, the system includes a wastewater stripping tower 1 and a reflux tank 2. The exhaust port at the top of the wastewater stripping tower 1 is connected to the reflux tank 3 via a first exhaust pipe. A condenser 14 is installed on the first exhaust pipe. The drain port at the bottom of the wastewater stripping tower 1 is connected to a purified water drain pipe 15. The exhaust port at the top of the reflux tank 3 is connected to a second exhaust pipe for discharging non-condensable gases. The outlet of the second exhaust pipe is connected to the reactor. A reflux tank pressure control valve 2, connected to the control system, is installed on the second exhaust pipe. A reflux tank condensate discharge line 6 is also connected to the bottom of the reflux tank 3. To achieve real-time online monitoring and adjustment of oil discharge, the oil phase separation and dynamic oil discharge system also includes... The system includes a COD monitor 13, an oil collection pipe 4, and an oil discharge regulating valve 9. The COD monitor 13 is connected to the purified water drain pipe 15 and is also connected to the control system. The oil collection pipe 4 is vertically installed inside the return tank 3, with the top of the oil collection pipe 4 lower than the highest liquid level in the return tank 3. The inlet end of the return tank condensate drain line 6 is connected to the lower oil outlet of the oil collection pipe 4. The outlet end of the return tank condensate drain line 6 is connected to the waste oil recovery tank 16. The return tank condensate drain line 6 and the waste oil recovery tank 16 are connected through the waste oil recovery tank inlet pipe 11. The oil discharge regulating valve 9 is installed on the return tank condensate drain line 6 and is connected to the control system.

[0025] When oil is discharged through the aforementioned oil phase separation and dynamic oil discharge system, the quality of the purified water discharged from the wastewater stripping tower 1 can be determined by monitoring the COD monitor 13 connected to the purified water discharge pipe 15. If the COD value of the delivered purified water is lower than the system-set value, it means that oil does not need to be discharged from the return tank 3. However, if the COD value of the delivered purified water exceeds the set value, it may indicate that there is still a high concentration of organic pollutants (including emulsified oil or dissolved organic matter) in the water. In this case, it means that the return tank 3 needs to be discharged in time. At this time, the pressure in the return tank is set by the return tank pressure control valve 2. Then, when the liquid level in the return tank 3 exceeds the set value, the pressure will be adjusted accordingly. When passing the top of the oil collecting pipe 4, the oil phase at the top of the liquid surface is pressed down into the oil collecting pipe 4 under the action of the oil phase static pressure. At the same time, the control system can control the oil discharge regulating valve 9 on the return tank discharge pipeline 6 to be in the open state. After that, the oil phase passes through the oil collecting pipe 4 and the return tank discharge pipeline 6 in sequence and is discharged to the waste oil recovery tank. In summary, the oil phase separation and dynamic oil discharge system of the wastewater stripping tower return tank of the MTO unit disclosed in this utility model can realize real-time dynamic online monitoring of the oil discharge process. When the COD value of the external purified water exceeds the index value, oil can be discharged in real time, thereby solving the problem of incomplete oil discharge in the existing oil discharge structure, which leads to excessive oil content in the external purified water.

[0026] The oil-water separation in reflux tank 3 primarily relies on the density difference between oil and water. Oil is generally less dense than water, so it floats on top. To ensure effective oil discharge, the upper oil layer needs to be collected and discharged through the oil collecting pipe, avoiding the intake of the lower water layer. When the upper oil phase is discharged, the static pressure generated by its own weight acts as a guide, propelling the oil phase from the oil collecting pipe 4 into the condensate drain line 6. The pressure within reflux tank 3 indirectly affects the oil phase discharge efficiency. For example, an increase in tank pressure may slightly increase the oil phase discharge rate; conversely, a decrease in pressure may slow down the discharge. The core driving force for oil phase discharge still relies on static pressure, and the pressure control valve mainly performs the pressure balancing function.

[0027] In this embodiment, the top of the oil collecting pipe 4 is positioned at 72%-75% of the highest liquid level in the reflux tank 3. This is to ensure that the oil phase can smoothly enter the oil collecting pipe 4 under the static pressure within the reflux tank 3. When the top of the oil collecting pipe 4 is below 72% of the highest liquid level, the liquid level of the liquid-oil phase mixture is low, and the oil phase thickness is insufficient. Insufficient oil phase thickness means that the oil phase is not enough to cover the inlet of the oil collecting pipe 4. This results in the inlet of the oil collecting pipe 4 being partially or completely exposed to air. When the inlet of the oil collecting pipe is exposed to air, air or other gases may enter the oil collecting pipe, which will cause unstable pressure within the oil collecting pipe and affect the flow of oil. External gas entering the oil collecting pipe 4 may also create gas resistance, further hindering oil discharge. When the top of the oil collecting pipe 4 is higher than 75% of the highest liquid level, the inlet of the oil collecting pipe is closer to the liquid surface, the oil phase liquid level depth decreases, resulting in a decrease in static pressure. Therefore, the static pressure cannot effectively overcome the pipe resistance and oil viscosity, thus affecting the efficiency of oil phase flowing into the oil collecting pipe 4. In this application, the top of the oil collecting pipe 4 is configured to be 72%-75% of the highest liquid level of the return tank 3. This can also prevent non-condensable gas from carrying a large amount of liquid to the reactor when it overflows along the second exhaust pipe. This can prevent the reactor temperature from dropping, and thus also prevent the product selectivity from deviating from the target.

[0028] Furthermore, in this embodiment, a check valve 7 is provided on the reflux tank drain line 6. When the fluid flows in a set direction, the check valve opens to allow the fluid to pass through; when the fluid pressure decreases or backflow occurs, the valve automatically closes to prevent the fluid from flowing in the opposite direction. Therefore, the check valve 7 is provided here to prevent the discharged floating oil from flowing back into the reflux tank and to ensure the unidirectional flow of the system.

[0029] Furthermore, to control the oil discharge process, a first field gate valve 10-1, an oil discharge sight glass 8, and a second field gate valve 10-2 are sequentially arranged downstream of the check valve 7 and between the oil discharge regulating valve 10 disclosed in this embodiment. The first field gate valve 10-1 is located near the check valve 7. The first field gate valve 10-1 is used to manually isolate the pipeline. By rotating the handwheel of the first field gate valve 10-1, the first field gate valve 10-1 can be fully opened or closed, thereby isolating the fluid flow in the pipeline. Here, the first field gate valve 10-1 is used to isolate the discharge during maintenance or repair. The drain pipe prevents fluid from entering downstream equipment; the drain sight glass 8 is used to observe the fluid flow status. Through the transparent sight glass window on the drain sight glass 8, the operator can intuitively observe the color, flow speed, and presence of impurities in the fluid in the drain pipe. Here, the drain sight glass is used to monitor the state of the discharged floating oil and condensate so as to adjust the system operating parameters in a timely manner; the second field gate valve 10-2 is used to further isolate the pipeline. The second field gate valve 10-2 is usually installed on the rear side of the drain sight glass 8 to provide double protection for the return tank drain condensate line 6 and prevent fluid from entering downstream equipment.

[0030] When the temperature is too low in winter, the oil phase in the return tank condensate drain line 6 will solidify and block it, thus affecting the normal discharge of the oil phase. Therefore, in order to avoid the oil phase solidification and blockage of the line, the return tank condensate drain line 6 disclosed in this embodiment is also connected to a steam purging line 12, which is located upstream of the check valve 7. The steam purging pressure of the steam purging line 12 is not less than 0.5 MPa. When hot steam is discharged into the return tank condensate drain line 6 through the steam purging line 12, it can effectively prevent the oil phase from solidifying and blocking the return tank condensate drain line 6 at low temperature. Furthermore, when the steam purging line 12 is used regularly to purge the return tank condensate drain line 6 and the recovery tank inlet line 11, the dirty oil in the line can be purged to the waste oil tank, ensuring that the line and the drain sight glass 8 are clean.

[0031] To prevent steam from entering the return tank through the condensate drain line 6 during steam purging, a third field gate valve 17 is installed upstream of the check valve 7, and the steam purging line 12 is located between the check valve 7 and the third field gate valve 17.

[0032] When using the oil phase separation and dynamic oil discharge system of the wastewater stripping tower reflux tank of the MTO unit disclosed in this utility model for oil discharge, it is confirmed that the first field gate valve 10-1 and the second field gate valve 10-2 on the reflux tank discharge pipeline 6 for oil discharge are in the normally open state. At the same time, the oil discharge sight glass 8 is ensured to be in good condition. In winter use, the reflux tank discharge pipeline 6 is heated by hot steam. When discharging oil, the system can predict in advance whether oil discharge is needed. If the online COD monitor shows that the data exceeds the index value, when the liquid level in the reflux tank 3 exceeds the top of the oil collection pipe 4, the reflux tank pressure is set by the reflux tank pressure regulating valve 2. The oil phase at the top of the liquid surface is pushed down by the pressure in the tank and can enter the oil collection pipe 4. At the same time, the control system controls the oil discharge regulating valve 9 on the reflux tank discharge pipeline 6 to be in the open state. Then, the oil phase is discharged to the waste oil recovery tank 16 after passing through the oil collection pipe 4 and the reflux tank discharge pipeline 6 in sequence. In summary, the MTO unit disclosed in this utility model... The oil phase separation and dynamic oil discharge system of the wastewater stripping tower reflux tank can realize real-time dynamic online monitoring of the oil discharge process. When the COD value of the external purified water exceeds the index value, oil can be discharged in real time, thus solving the problem of incomplete oil discharge leading to excessive oil content in the external purified water due to the existing oil discharge structure. In addition, the oil phase separation and dynamic oil discharge system also has the following beneficial effects: because the top of the oil collection pipe 4 is located at 72%-75% of the highest liquid level of the reflux tank 3, it can prevent non-condensable gas from carrying a large amount of liquid into the reactor when it overflows along the second pipe, thus avoiding the problem of product selectivity deviating from the index; and by setting up a steam pipe, it can simultaneously prevent the oil phase from solidifying and clogging the reflux tank condensate discharge pipe 6 at low temperature, and can also purge the sludge oil in the pipeline to the waste oil tank. The above-mentioned oil phase separation and dynamic oil discharge system can dynamically respond to changes in the oil phase and adapt to complex working conditions by adjusting the oil discharge rate in real time.

[0033] In the description of the embodiments of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the embodiments of this utility model and simplifying the description. They do not 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 utility model. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In addition, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this utility model can be understood according to the specific circumstances.

[0034] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0035] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. An oil phase separation and dynamic oil discharge system for a wastewater stripping tower reflux tank in an MTO unit, comprising a wastewater stripping tower (1), wherein the exhaust port at the top of the wastewater stripping tower (1) is connected to a reflux tank (3) via a first exhaust pipe, a condenser (14) is provided on the first exhaust pipe, a purified water discharge pipe (15) is provided at the drain port at the bottom of the wastewater stripping tower (1), a second exhaust pipe for discharging non-condensable gases is provided at the top of the reflux tank (3), a reflux tank pressure control valve (2) connected to a control system is provided on the second exhaust pipe, and a reflux tank condensate discharge line (6) is also connected to the bottom of the reflux tank (3), characterized in that, Also includes: A COD monitor (13) is connected to the purified water drain pipe (15), and the COD monitor (13) is connected to the control system; An oil collecting pipe (4) is vertically installed inside the return tank (3). The top of the oil collecting pipe (4) is lower than the top of the return tank (3). The inlet end of the return tank drain line (6) is connected to the lower oil outlet of the oil collecting pipe (4). The outlet end of the return tank drain line (6) is connected to a waste oil recovery tank (16). An oil drain regulating valve (9) is installed on the condensate drain line (6) of the return tank, and the oil drain regulating valve (9) is connected to the control system.

2. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 1, characterized in that, The top of the oil collecting pipe (4) is located at 72%-75% of the highest liquid level of the return tank (3).

3. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 1, characterized in that, A check valve (7) is installed on the reflux tank drain line (6).

4. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 3, characterized in that, Downstream of the check valve (7) and between the drain regulating valve (9), a first field gate valve (10-1), a drain sight glass (8), and a second field gate valve (10-2) are sequentially arranged.

5. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 3, characterized in that, The oil outlet of the return tank drain line (6) is connected to the waste oil recovery tank (16) via the waste oil recovery tank inlet line (11).

6. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 5, characterized in that, The reflux tank drain line (6) is also connected to a steam purging line (12), which is located upstream of the check valve (7).

7. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 6, characterized in that, The steam purging pressure of the steam purging pipeline (12) is not less than 0.5 MPa.

8. The oil phase separation and dynamic oil discharge system for the wastewater stripping tower reflux tank of an MTO unit according to claim 7, characterized in that, A third field gate valve (17) is also provided upstream of the check valve (7), and the steam purging pipeline (12) is located between the check valve (7) and the third field gate valve (17).

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