Methanol preheating device and preheating method for MTO (methanol to olefin) device

Abstract

The invention discloses a methanol preheating device and method for an MTO device. The preheating device comprises a first condensation water tank, a first heat exchanger and a second condensation water tank which are sequentially communicated, and further comprises a third heat exchanger and a fourth heat exchanger which are arranged in parallel. A preheating pipeline of the methanol feeding device is provided with a pipeline III and a pipeline IV which are connected in parallel, methanol discharging ends of the pipeline III and the pipeline IV are converged and then communicated with a methanol feeding end of a heat exchanger II, and a preheating pipeline at a methanol discharging end of the heat exchanger II is communicated with a feeding end of a vaporizer; the preheating method comprises the steps that raw material methanol firstly exchanges heat with high-temperature purified water in the heat exchanger III and / or the heat exchanger IV through the preheating pipeline, then enters the heat exchanger II and exchanges heat with high-temperature condensed water in the heat exchanger II, and finally, the raw material methanol enters the vaporizer and is treated by the vaporizer to obtain gas-phase methanol. According to the scheme, the methanol preheating effect can be improved, the system waste heat utilization rate is increased, and the vaporizer load and energy consumption are reduced.

Description

Technical Field

[0001] The invention relates to the field of methanol preheating, and in particular to a methanol preheating device and a preheating method for an MTO device. Background Art

[0002] The MTO device uses liquid methanol as raw material, which is vaporized through a heat exchange device and a methanol-stripping gas heat exchanger. The vaporized methanol enters the reactor. In the prior art, in order to consider economic benefits, the methanol feed load in the industry is generally controlled at more than 120%, and considering the energy consumption and raw material cost savings of upstream and downstream devices, MTO-grade methanol is used as feed. The water content in MTO-grade methanol is about 5% higher than that of refined methanol, which causes the methanol-steam vaporizer heat exchanger to have limited feed load under high load, high water content and low temperature weather; in addition, in the prior art, the waste heat utilization rate of the MTO device is insufficient. If the waste heat in the system can be recovered by effective means and the methanol preheating temperature can be increased, the load limitation of using MTO-grade methanol can be alleviated, the cost of methanol use can be reduced, the energy consumption of the device can be saved, and the marginal benefit of the device production can be improved. Summary of the invention

[0003] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a methanol preheating device and preheating method for an MTO unit, which can improve the methanol preheating effect, increase the system waste heat utilization rate and reduce the vaporizer load and energy consumption.

[0004] To solve the above problems, the present invention provides the following technical solutions: A methanol preheating device for an MTO device, the preheating device comprising at least one condensate tank 1 in a sewage stripping system, the water outlet end of the condensate tank 1 being connected to the water inlet end of the condensate tank 2 through a parallel pipeline 1 and a pipeline 2, the pipeline 2 being connected to a heat exchanger 1, the water outlet end of the condensate tank 2 being connected to the water inlet end of the heat exchanger 2 through a pump, the water outlet end of the heat exchanger 2 being connected to a condensate outlet device; the preheating device further comprising a heat exchanger 3 and a heat exchanger 4 being arranged in parallel, the water inlet ends of the heat exchanger 3 and the heat exchanger 4 being connected to a purified water inlet The device comprises a purified water outlet device, the outlet ends of heat exchanger three and heat exchanger four are connected with a purified water outlet device; the methanol feeding device comprises a preheating pipeline of raw methanol, the preheating pipeline is provided with a parallel pipeline three and a pipeline four, the pipeline three is connected with the methanol feed end of heat exchanger three, the pipeline four is connected with the methanol feed end of heat exchanger four, the methanol discharge ends of pipeline three and pipeline four are connected with the methanol feed end of heat exchanger two after merging, and the preheating pipeline of the methanol discharge end of heat exchanger two is connected with the feed end of the vaporizer; pipeline one, pipeline two, pipeline three and pipeline four are all provided with valves.

[0005] It should be noted that the wastewater stripping unit is an important unit for treating wastewater in the MTO (methanol to olefins) unit and produces low-pressure steam condensate. In this application, the low-pressure steam condensate is cooled by heat exchanger 1 and then sent to condensate tank 2. The purpose of setting heat exchanger 1 is to prevent the low-pressure steam condensate from impacting condensate tank 2 due to high temperature.

[0006] Heat exchanger three and heat exchanger four are designed in parallel and can be used in parallel or separately. Together with heat exchanger two that uses waste heat recovery for heat exchange, they can increase the preheating temperature of raw methanol and reduce the amount of purified water used.

[0007] The technical solution of the present invention also includes that a wall valve is provided on the pipeline at the water inlet end of the condensate tank 2, and the wall valve can stabilize the temperature of the condensate entering the condensate tank 2 through the pipeline. Preferably, the technical solution of the present invention also includes that the wall-attached valve is a ball valve, a butterfly valve, a gate valve, or a pendulum valve.

[0008] The technical solution of the present invention also includes that the heat exchanger 1 is connected to a cooling circulation device, and the function of the heat exchanger 1 is to cool the high-temperature low-pressure steam condensate to avoid water hammer in the condensate tank 2.

[0009] Furthermore, the technical solution of the present invention also includes that the heat exchanger is a shell and tube condenser or a plate condenser.

[0010] The technical solution of the present invention also includes that the heat exchanger 2, the heat exchanger 3, and the heat exchanger 4 are all shell and tube heat exchangers, plate heat exchangers, and sleeve and tube heat exchangers.

[0011] The second object of the present invention is to provide a methanol preheating method using the above-mentioned device, wherein the low-pressure steam condensate of the sewage stripping system enters pipeline one and / or pipeline two after being stored in condensate tank one, and then enters condensate tank two. The low-pressure steam condensate passing through pipeline two is cooled by heat exchanger one and then enters condensate tank two. The high-temperature condensate in condensate tank two is pumped to heat exchanger two by a pump; the raw methanol first exchanges heat with the high-temperature purified water in heat exchanger three and / or heat exchanger four through the preheating pipeline, and then enters heat exchanger two to exchange heat with the high-temperature condensate in heat exchanger two. Finally, the raw methanol enters the vaporizer and is treated by the vaporizer to obtain gaseous methanol.

[0012] The beneficial effects of the present invention are: Compared with the prior art, the purpose of the present invention is to provide a methanol preheating device and preheating method for an MTO device that improves the methanol preheating effect, improves the system waste heat utilization rate, and reduces the vaporizer load and energy consumption. In order to achieve the above technical effects, the preheating device of the present invention includes a heat exchanger 2 connected to a condensate tank 1 of a sewage stripping system, and uses a heat exchanger 2 and a heat exchanger 3 connected in parallel to each other, which effectively improves the waste heat effect before methanol gasification. In addition, a heat exchanger 1 is arranged in front of the condensate tank 2, thereby avoiding the water hammer phenomenon. The present invention realizes the recycling of the condensate heat in the system and the heat of the purified water system in the liquid phase methanol feeding process, which can effectively reduce the load of the vaporizer, reduce steam energy consumption, and achieve the beneficial effects of using MTO-grade high-water-content methanol and reducing raw material costs and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 It is a schematic diagram of a methanol preheating device for an MTO unit in a specific implementation manner.

[0015] Among them, 1 is condensate tank 1, 2 is pipeline 1, 3 is pipeline 2, 4 is condensate tank 2, 5 is wall valve, 6 is heat exchanger 1, 7 is pump, 8 is heat exchanger 2, 9 is heat exchanger 3, 10 is heat exchanger 4, 11 is preheating pipeline, 12 is pipeline 3, 13 is pipeline 4, 14 is vaporizer, and 15 is valve. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0017] In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only intended to simplify the description of the present invention, rather than to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0018] As can be seen from the attached drawings, a methanol preheating device for an MTO device comprises two condensate tanks 1 in a sewage stripping system, the water outlet of condensate tank 1 being connected to the water inlet of condensate tank 4 via a parallel pipeline 1 and a pipeline 2 3, and a wall valve 5 is provided on the pipeline at the water inlet of condensate tank 2 4.

[0019] The pipeline 23 is connected to a heat exchanger 6, which is a shell and tube condenser. The heat exchanger 6 is connected to a cooling circulation device. The water outlet of the condensate tank 24 is connected to the water inlet of the heat exchanger 28 through a pump 7, and the water outlet of the heat exchanger 28 is connected to a condensate outlet device.

[0020] The preheating device also includes a heat exchanger 3 9 and a heat exchanger 4 10 arranged in parallel, the water inlet ends of the heat exchanger 3 9 and the heat exchanger 4 10 are connected to a purified water inlet device, and the water outlet ends of the heat exchanger 3 9 and the heat exchanger 4 10 are connected to a purified water outlet device.

[0021] The methanol feeding device includes a preheating pipeline 11 for raw methanol, and the preheating pipeline 11 is provided with a parallel pipeline 3 12 and a pipeline 4 13, the pipeline 3 12 is connected to the methanol feeding end of the heat exchanger 3 9, the pipeline 4 13 is connected to the methanol feeding end of the heat exchanger 4 10, the methanol discharge ends of the pipeline 3 12 and the pipeline 4 13 are connected to the methanol feeding end of the heat exchanger 2 8, and the preheating pipeline 11 at the methanol discharge end of the heat exchanger 2 8 is connected to the feeding end of the vaporizer 14. Pipeline 1 2, pipeline 2 3, pipeline 3 12, and pipeline 4 13 are all provided with valves 15.

[0022] A methanol preheating method using the above-mentioned device, low-pressure steam condensate of the sewage stripping system is stored in condensate tank one 1 and then enters pipeline one 2 and pipeline two 3, and then enters condensate tank two 4, the low-pressure steam condensate passing through pipeline two 3 is cooled by heat exchanger one 6 and then enters condensate tank two 4, and the high-temperature condensate in condensate tank two 4 is pumped to heat exchanger two 8 by pump machine 7; raw methanol first exchanges heat with high-temperature purified water in heat exchanger three 9 and heat exchanger four 10 through preheating pipeline 11, and then enters heat exchanger two 8, exchanges heat with high-temperature condensate in heat exchanger two 8, and finally, the raw methanol enters vaporizer 14, and is processed by vaporizer 14 to obtain gaseous methanol.

[0023] The device and method can effectively improve the preheating effect of raw methanol, realize the recovery and utilization of condensate heat and purified water system heat in the MTO device system in the liquid methanol feeding process, effectively reduce the load of the vaporizer, reduce steam energy consumption, and realize the use of MTO-grade high-water-content methanol, thereby reducing the beneficial effects of raw material cost and energy consumption.

[0024] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art who is familiar with the present invention may easily think of changes or substitutions within the technical scope disclosed by the present invention, and all of these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A methanol preheating device for an MTO device, characterized in that: The preheating device includes at least one condensate tank 1 in the sewage stripping system, the outlet end of the condensate tank 1 is connected to the water inlet end of the condensate tank 2 through a parallel pipeline 1 and a pipeline 2, the pipeline 2 is connected to a heat exchanger 1, the outlet end of the condensate tank 2 is connected to the water inlet end of the heat exchanger 2 through a pump, and the outlet end of the heat exchanger 2 is connected to a condensate outlet device; the preheating device also includes a heat exchanger 3 and a heat exchanger 4 arranged in parallel, the water inlets of the heat exchanger 3 and the heat exchanger 4 are connected to the purified water inlet device, the heat exchanger 3 and The water outlet end of heat exchanger four is connected to a purified water outlet device; the methanol feeding device includes a preheating pipeline for raw methanol, and the preheating pipeline is provided with parallel pipelines three and four, pipeline three is connected to the methanol feed end of heat exchanger three, pipeline four is connected to the methanol feed end of heat exchanger four, and the methanol discharge ends of pipeline three and pipeline four are connected to the methanol feed end of heat exchanger two after merging, and the preheating pipeline of the methanol discharge end of heat exchanger two is connected to the feed end of the vaporizer; pipeline one, pipeline two, pipeline three, and pipeline four are all provided with valves.

2. The methanol preheating device for an MTO device according to claim 1, characterized in that: A wall valve is provided on the pipeline at the water inlet end of the second condensate tank.

3. The methanol preheating device for an MTO device according to claim 2, characterized in that: The wall-attached valve is a ball valve, a butterfly valve, a gate valve, or a pendulum valve.

4. The methanol preheating device for an MTO device according to claim 1, characterized in that: The heat exchanger is connected to a cooling circulation device.

5. The methanol preheating device for an MTO device according to claim 1, characterized in that: The heat exchanger 1 is a shell and tube condenser or a plate condenser.

6. The methanol preheating device for an MTO device according to claim 1, characterized in that: The heat exchanger 2, the heat exchanger 3 and the heat exchanger 4 are all shell and tube heat exchangers, plate heat exchangers and sleeve and tube heat exchangers.

7. The methanol preheating method of the device according to claim 1, characterized in that: The low-pressure steam condensate of the sewage stripping system is stored in the condensate tank one and then enters the pipeline one and / or pipeline two, and then enters the condensate tank two. The low-pressure steam condensate passing through the pipeline two is cooled by the heat exchanger one and then enters the condensate tank two. The high-temperature condensate in the condensate tank two is pumped to the heat exchanger two by a pump; the raw methanol first exchanges heat with the high-temperature purified water in the heat exchanger three and / or heat exchanger four through the preheating pipeline, and then enters the heat exchanger two to exchange heat with the high-temperature condensate in the heat exchanger two. Finally, the raw methanol enters the vaporizer and is treated in the vaporizer to obtain gaseous methanol.

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