Gradient utilization device for heat energy of dehydrogenation tail gas

Abstract

The utility model belongs to the field of chemical engineering, and particularly provides a dehydrogenation tail gas heat energy gradient utilization device which comprises a gas-liquid separator, a feeding port of the gas-liquid separator is connected with a dehydrogenation tail gas pipeline, a gas phase outlet is formed in the upper portion of the gas-liquid separator, and the gas-liquid separator is connected to a tube pass of a steam pocket through a pipeline. A desalted water supplementing pipe is arranged at the lower part of the shell side; the device further comprises a liquid-phase collecting tank, a liquid-phase outlet of the gas-liquid separator and an outlet of the steam drum tube pass are connected to the liquid-phase collecting tank through pipelines, a gas-phase outlet is formed in the top of the liquid-phase collecting tank, and a gas phase enters the gas-phase introduction hydrogen compressor after being subjected to heat exchange through the condenser. The dehydrogenation tail gas is subjected to gas-liquid separation of a liquid phase to reduce the tail gas treatment load, the tail gas is subjected to heat exchange in a steam pocket to generate byproduct steam, then heat exchange is further performed to generate byproduct hot water, and finally heat exchange is performed to reduce the gas phase temperature so as to reduce the compressor load. The device can realize stepped recycling of heat and achieve the purposes of energy conservation and consumption reduction.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical industry and relates to a dehydrogenation tail gas heat energy cascade utilization device, which is particularly suitable for utilizing the tail gas heat energy in the production of cyclohexanone using benzene as a raw material. Background Art

[0002] Cyclohexanone is a colorless and transparent liquid. It is the simplest type of cyclic ketone compounds and is widely used in the chemical, pharmaceutical and food industries. Cyclohexanone has excellent properties such as low toxicity, low volatility and high boiling point, so it is widely used as a solvent, intermediate and fragrance. At present, about 83% of the world's cyclohexanone is produced using benzene as raw material. There are two types of technical routes for producing cyclohexanone using benzene as raw material: hydrogenation-hydration technical route (commonly known as cyclohexene method) and hydrogenation-oxidation technical route (commonly known as cyclohexane oxidation method). The cyclohexene method is that benzene is partially hydrogenated to produce cyclohexene, cyclohexene is hydrated to produce cyclohexanol, and cyclohexanol can be dehydrogenated to produce cyclohexanone. The cyclohexane oxidation method is that benzene is completely hydrogenated to produce cyclohexane, cyclohexane is oxidized, and peroxide decomposition is obtained to obtain cyclohexanone and cyclohexanol, and cyclohexanol is further dehydrogenated to produce cyclohexanone. In both cyclohexanone production processes, part or even all of the cyclohexanone products come from the cyclohexanol dehydrogenation process. Cyclohexanol is dehydrogenated to cyclohexanone under the action of catalyst, which requires the absorption of heat. Main reaction formula:

[0003] C6H 11 OH C6H 10 O +H2-62kJ / mol

[0004] Cyclohexanol is heated to 170℃ by steam and then sent to the dehydrogenation reactor. Under the operating conditions of normal pressure and 220℃~270℃, the cyclohexanol dehydrogenation reaction is carried out under the action of copper catalyst. Part (about 50%) of the cyclohexanol is converted into cyclohexanone and hydrogen after the dehydrogenation reaction. After the reaction, the organic materials containing cyclohexanol, cyclohexanone, water and hydrogen at about 140℃ after the primary heat recovery are sent to the cooling system. This part of the material has a high temperature and requires a large amount of circulating water to remove the heat. Summary of the invention

[0005] The utility model provides a dehydrogenation tail gas heat energy cascade utilization device, which can fully utilize the heat energy of the dehydrogenation tail gas.

[0006] The technical solution of the utility model is a dehydrogenation tail gas heat energy cascade utilization device, including a gas-liquid separator, a feed port of which is connected to the dehydrogenation tail gas pipeline, a gas phase outlet is provided on the upper part, and is connected to the tube side of the drum through a pipeline, a steam pipeline is provided on the upper part of the drum shell side to connect to the steam network, and a desalted water replenishment pipe is provided on the lower part of the shell side; the device also includes a liquid phase collecting tank, the liquid phase outlet of the gas-liquid separator and the outlet of the drum tube side are both connected to the liquid phase collecting tank through a pipeline, a gas phase outlet is provided on the top of the liquid phase collecting tank, and the gas phase enters the gas phase after heat exchange in the condenser and is introduced into the hydrogen compressor.

[0007] Furthermore, a heat exchanger is provided on the pipeline between the tube-side outlet of the steam drum and the liquid phase collecting tank.

[0008] Furthermore, a safety relief valve is provided on the steam pipeline.

[0009] Furthermore, a liquid level gauge is provided in the shell side of the drum, and a liquid level regulating valve is installed on the desalted water replenishing pipe.

[0010] Furthermore, the condensate of the condenser flows back to the liquid phase collection tank through a pipeline.

[0011] Furthermore, a condensate delivery pump and pipeline are provided at the bottom of the liquid phase collection tank.

[0012] The utility model has the following beneficial effects:

[0013] Since the temperature of the dehydrogenation tail gas obtained in the production of cyclohexanone is relatively high, reaching about 140°C, this device first separates the gas and liquid, collects the liquid phase, and the gas phase enters the drum for heat exchange, and uses its heat to generate steam. The obtained steam can enter the low-pressure steam pipeline for users to use. At the same time, a safety relief valve is set on the low-pressure steam pipeline to protect the safety of the drum; liquid level gauges, control valves and liquid level transmitters can also be set on the drum shell and desalted water pipeline to achieve automatic control of the liquid level. After the gas phase is heat exchanged in the drum, it can be further heat exchanged in the heat exchanger to produce 60-90°C hot water as a by-product, and then enter the liquid phase collection tank. The gas phase is further condensed by low-temperature water in the condenser to reduce the temperature of the hydrogen, and then enters the hydrogen compressor for treatment and reuse.

[0014] The device provided by the utility model greatly reduces the consumption of circulating cooling water in the cyclohexanol dehydrogenation part by stepwise recycling and utilizing the heat of the materials at the outlet of the cyclohexanol dehydrogenation reactor, and finally achieves the purpose of energy saving and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the device of the utility model. DETAILED DESCRIPTION

[0016] The embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0017] The dehydrogenation tail gas in the cyclohexanone production process mainly contains cyclohexanone, cyclohexanol, hydrogen, light components, water, heavy components, etc., with a temperature of about 140°C. If circulating water is used directly for cooling, the water consumption will be large and the heat energy cannot be fully utilized.

[0018] The following embodiment provides a dehydrogenation tail gas heat energy cascade utilization device, such as Figure 1 As shown, the device includes a gas-liquid separator 1, whose feed port is connected to the dehydrogenation tail gas pipeline 1-1, and a gas phase outlet is provided on the upper part, which is connected to the tube side of the drum 2 through a pipeline, and a steam pipeline 2-1 is provided on the upper part of the shell side of the drum 2 to connect to the steam network, and a desalted water replenishing pipe 2-2 is provided on the lower part of the shell side; the device also includes a liquid phase collecting tank 4, the liquid phase outlet of the gas-liquid separator 1 and the outlet of the tube side of the drum 2 are connected to the liquid phase collecting tank 4 through a pipeline, and a gas phase outlet is provided on the top of the liquid phase collecting tank 4, and the gas phase at the gas phase outlet is introduced into the hydrogen compressor 6 after heat exchange through the condenser 5.

[0019] The mixed gas-liquid raw materials (i.e., dehydrogenation tail gas) enter the middle of the gas-liquid separator 1 (cyclone separator is optional) for separation, the bottom heavy phase is connected to the liquid phase collection tank 4 through the line pipeline, the gas phase of the separator is connected to the tube side of the drum (optionally low-pressure steam drum) 2 through the line pipeline, and the low-pressure steam produced by the shell side of the drum 2 is connected to the low-pressure steam network through the steam pipeline 2-1. After the heat exchange of the tube side, it is also connected to the liquid phase collection tank 4 to further collect the liquid phase, and the gas phase is condensed by low-temperature water and enters the compressor for processing and recovery.

[0020] In a preferred embodiment, a heat exchanger 3 is further provided on the pipeline between the tube outlet of the drum 2 and the liquid phase collecting tank 4. Normal temperature water can be used for heat exchange here, and the temperature of the heat exchange medium can be raised to 60-90°C to further recover the heat in the dehydrogenation tail gas.

[0021] In another preferred embodiment, a safety relief valve is provided on the steam pipe 2-1 to protect the safety of the steam drum. The steam drum here can be a low-pressure steam drum.

[0022] In another preferred embodiment, a liquid level gauge is further provided in the shell side of the drum 2, and a liquid level regulating valve is installed on the desalted water replenishment pipe 2-2. The liquid level gauge may be a remote liquid level gauge, and the remote liquid level gauge and the liquid level regulating valve form a control loop through a liquid level transmitter to automatically adjust the liquid level in the drum to ensure system safety.

[0023] In another preferred embodiment, the condensate of the condenser 5 flows back to the liquid phase collection tank 4 through a pipeline. The gas phase overflowing from the liquid phase collection tank 4 is condensed by low-temperature water in the condenser, and the obtained liquid phase flows back to the liquid phase collection tank 4 through a line pipeline, while reducing the temperature of the hydrogen, which can reduce the operating load of the hydrogen compressor in the later stage.

[0024] In another preferred embodiment, a condensate delivery pump and a pipeline are provided at the bottom of the liquid phase collection tank 4, so that the condensed liquid phase can be timely extracted and further separated and processed.

[0025] The utility model reduces the load of subsequent tail gas treatment by first separating the liquid phase of the material at the outlet of the cyclohexanol dehydrogenation reactor; in the later heat exchange and heat recovery process, firstly recovers the heat by-product part of low-pressure steam through the low-pressure steam drum, and then uses water for heat exchange to produce by-product 60-90°C hot water, further recovers the heat of the dehydrogenation tail gas, and reduces the temperature in the condenser before entering the compressor, thereby reducing the operating load of the hydrogen compressor.

[0026] Through the cascade recovery and utilization of the heat of the above materials, the consumption of circulating cooling water in the cyclohexanol dehydrogenation part is greatly reduced, ultimately achieving the goal of energy saving and consumption reduction.

[0027] The above embodiments are only for illustrating the technical ideas and features of the utility model, and the contents are only preferred embodiments of the utility model, but the protection scope of the utility model is not limited thereto. Within the technical scope disclosed by the utility model, equivalent changes or improvements based on the technical solution and utility model concept of the utility model should be included in the protection scope of the utility model.

Claims

1. A dehydrogenation tail gas heat energy cascade utilization device, characterized in that: The device comprises a gas-liquid separator (1), the feed port of which is connected to a dehydrogenation tail gas pipeline (1-1), the upper part of which is provided with a gas phase outlet, which is connected to the tube side of a drum (2) through a pipeline, the upper part of the shell side of the drum (2) is provided with a steam pipeline (2-1) connected to a steam network, and the lower part of the shell side is provided with a desalted water replenishment pipe (2-2); the device also comprises a liquid phase collection tank (4), the liquid phase outlet of the gas-liquid separator (1) and the outlet of the tube side of the drum (2) are both connected to the liquid phase collection tank (4) through a pipeline, the top of the liquid phase collection tank (4) is provided with a gas phase outlet, and the gas phase enters the gas phase after heat exchange in a condenser (5) and is introduced into a hydrogen compressor (6).

2. The device according to claim 1, characterized in that: A heat exchanger (3) is also provided on the pipeline between the tube-side outlet of the steam drum (2) and the liquid phase collecting tank (4).

3. The device according to claim 1, characterized in that: The steam pipeline (2-1) is provided with a safety relief valve.

4. The device according to claim 1, characterized in that: A liquid level gauge is also provided in the shell side of the steam drum (2), and a liquid level regulating valve is installed on the desalted water replenishing pipe (2-2).

5. The device according to claim 1, characterized in that: The condensate from the condenser (5) flows back to the liquid phase collection tank (4) through a pipeline.

6. The device according to any one of claims 1 to 5, characterized in that: A condensate delivery pump and a pipeline are provided at the bottom of the liquid phase collection tank (4).

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