Energy-saving acetaldehyde production process device

Abstract

The utility model discloses an energy -saving acetaldehyde production process device, and main equipment includes ethanol evaporator, oxidizer, absorption tower, acetaldehyde rectifying column and ethanol recovery tower, the bottom of ethanol evaporator is equipped with ethanol import and air import, the air import is through the pipeline and dips into ethanol evaporator liquid level below, ethanol evaporator top is equipped with ethanol steam export, and is connected with oxidizer through the pipeline. The utility model discloses through optimization process realizes heat recovery, and the unit consumption of acetaldehyde product is reduced to 1.0t steam / t product, and the consumption of circulating water also reduces greatly.

Description

Technical Field

[0001] This utility model belongs to the field of energy-saving chemical technology, and in particular relates to a highly efficient and energy-saving acetaldehyde production process device and method. Background Technology

[0002] Acetaldehyde is an aldehyde, a colorless, easily flowing liquid with a pungent odor. It has a melting point of -121°C, a boiling point of 20.8°C, and a relative density of less than 1. It is soluble in water and some organic substances such as ethanol. Industrially, acetaldehyde is mostly produced by the direct oxidation of ethylene, which is costly and involves a complex process. Existing technologies also use ethanol as a raw material, where ethanol and air undergo oxidation and dehydrogenation reactions in the presence of a silver catalyst to produce acetaldehyde. However, in this process, the unreacted ethanol is not fully recovered, resulting in a low product yield. More importantly, the large amount of heat generated by the ethanol oxidation reaction is not fully recovered and utilized. Furthermore, steam is consumed during ethanol evaporation, acetaldehyde distillation, and ethanol recovery; current acetaldehyde processes consume 1.2-1.5 tons of steam per ton of product, with poor heat recovery efficiency. Summary of the Invention

[0003] Purpose of the invention: In view of the above-mentioned existing problems and deficiencies, the purpose of this utility model is to provide an energy-saving acetaldehyde production process device. By optimizing the process to achieve heat recovery, the unit consumption of acetaldehyde product is reduced to less than 1.0t steam / t product, while the consumption of circulating water is also greatly reduced.

[0004] Technical Solution: To solve the above-mentioned technical problems, this utility model adopts the following technical solution: an energy-saving acetaldehyde production process device, characterized in that it includes an ethanol evaporator, an oxidizer, an absorption tower, an acetaldehyde distillation tower, and an ethanol recovery tower. The bottom of the ethanol evaporator is provided with an ethanol inlet and an air inlet, and the air inlet extends into the liquid surface of the ethanol evaporator through a pipe; the top of the ethanol evaporator is provided with an ethanol vapor outlet, which is connected to the oxidizer through a pipe. The oxidizer has an oxidation product outlet at the bottom, which is connected to the middle section of the absorption tower via a pipe; a first tail gas condenser and a second tail gas condenser are also provided on the pipe connecting the oxidation product outlet to the absorption tower. The top of the absorption tower is provided with a spray water inlet and a tail gas outlet, and the bottom is provided with an acetaldehyde solution outlet. The acetaldehyde solution outlet is connected to the first tail gas condenser through a pipeline for heat exchange and then connected to the middle section of the acetaldehyde distillation tower. The acetaldehyde distillation column is provided with an acetaldehyde product outlet pipe at the top and a bottom liquid outlet at the bottom. The acetaldehyde product outlet pipe is also provided with an acetaldehyde distillation condenser and a bypass pipe connected to the top of the acetaldehyde distillation column. The bottom liquid outlet is connected to the middle section of the ethanol recovery column through a pipeline. The ethanol recovery tower is provided with a wastewater outlet and an ethanol recovery outlet pipe at its bottom and top, respectively. The ethanol recovery outlet pipe is equipped with an ethanol recovery tower condenser. The ethanol recovery outlet pipe is connected to the ethanol evaporator and the top of the ethanol recovery tower through pipelines. The bottom of the ethanol evaporator is also connected to the condenser of the ethanol recovery tower via a pipe to achieve heat exchange with the ethanol recovery liquid.

[0005] Preferably, a condensate heat exchanger is also provided on the pipeline connecting the acetaldehyde solution outlet of the absorption tower to the acetaldehyde distillation tower, and the condensate heat exchanger is located after the first tail gas condenser.

[0006] Preferably, the ethanol recovery and extraction pipe and the ethanol inlet are equipped with an ethanol mixer before entering the ethanol evaporator.

[0007] Preferably, a feed superheater is also provided on the pipe connecting the ethanol evaporator and the oxidizer.

[0008] Preferably, the absorption tower is provided with three spray condensation absorption sections.

[0009] Beneficial Effects: Compared with existing technologies, this invention achieves the recovery and utilization of the exothermic reaction of ethanol oxidation through a multi-stage heat exchanger. Simultaneously, it utilizes the overhead vapor phase of the ethanol tower as a heat source for ethanol evaporation, saving low-pressure steam and reducing the consumption of circulating water in the ethanol recovery tower condenser. Furthermore, the collected low-pressure steam condensate from this device exchanges heat with the feed to the acetaldehyde distillation tower, further increasing the feed temperature and reducing steam consumption in the acetaldehyde distillation tower reboiler. Taking a 30,000-ton acetaldehyde unit as an example, compared to existing processes, this invention reduces steam consumption by 46.9% to 3.5 t / h and circulating water consumption by 36.6% to 590 t / h. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the energy-saving acetaldehyde production process device described in this utility model.

[0011] The components include: 1. Ethanol evaporator; 2. Oxidizer; 3. Absorber; 4. Acetaldehyde distillation tower; 5. Ethanol recovery tower; 6. Ethanol circulation pump; 7. First tail gas condenser; 8. Second tail gas condenser; 9. Condensate heat exchanger; 10. Acetaldehyde distillation condenser; and 11. Ethanol recovery tower condenser. Detailed Implementation

[0012] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0013] like Figure 1 As shown, the energy-saving acetaldehyde production process device of this utility model includes an ethanol evaporator, an oxidizer, an absorption tower, an acetaldehyde distillation tower, and an ethanol recovery tower, wherein: The bottom of the ethanol evaporator is provided with an ethanol inlet and an air inlet, and the air inlet extends into the liquid surface of the ethanol evaporator through a pipe; the top of the ethanol evaporator is provided with an ethanol vapor outlet, which is connected to the oxidizer through a pipe. The oxidizer has an oxidation product outlet at the bottom, which is connected to the middle section of the absorption tower via a pipe; a first tail gas condenser and a second tail gas condenser are also provided on the pipe connecting the oxidation product outlet to the absorption tower. The top of the absorption tower is provided with a spray water inlet and a tail gas outlet, and the bottom is provided with an acetaldehyde solution outlet. The acetaldehyde solution outlet is connected to the first tail gas condenser through a pipeline for heat exchange and then connected to the middle section feed port of the acetaldehyde distillation tower. The acetaldehyde distillation column is provided with an acetaldehyde product outlet pipe at the top and a bottom liquid outlet at the bottom. The acetaldehyde product outlet pipe is also provided with an acetaldehyde distillation condenser and a bypass pipe connected to the top of the acetaldehyde distillation column. The bottom liquid outlet is connected to the middle feed port of the ethanol recovery column through a pipeline. The ethanol recovery tower is provided with a wastewater outlet and an ethanol recovery outlet pipe at its bottom and top, respectively. The ethanol recovery outlet pipe is connected to the ethanol evaporator through a pipeline, and is also connected to the top of the ethanol recovery tower through a reflux pipe. The ethanol recovery outlet pipe is also provided with an ethanol recovery tower condenser. The bottom of the ethanol evaporator is also connected to the condenser of the ethanol recovery tower via a pipe, enabling heat exchange with the ethanol recovery liquid. Based on the above device, the acetaldehyde process flow of this utility model is as follows.

[0014] 1) Ethanol evaporation and oxidation reaction Raw ethanol and recycled ethanol are mixed in an ethanol mixer and then enter an ethanol evaporator. Low-pressure steam is used to provide heat for acetaldehyde evaporation. The evaporation temperature is 65–70°C, and the pressure inside the evaporator is 20–30 kPa. Low-pressure steam is used to heat the ethanol... After passing through the air filter, the air is pressurized by an air blower and enters the air buffer tank. The outlet pressure of the air blower is 49 kPag. The air from the buffer tank outlet enters the lower part of the ethanol evaporator, where it is bubbled inside the evaporation vessel to accelerate the evaporation of ethanol. The gas exiting the ethanol evaporator is preheated to 120-130°C by the feed superheater, and then passes through the feed filter before entering the oxidizer.

[0015] 2) Oxidation reaction When the feed gas from the ethanol evaporator is running normally, it enters the oxidizer. The reaction process releases a large amount of heat, and the temperature in the reaction zone is about 530-550℃. The heat of the reaction gas is recovered by using hot water at 80-95℃ to generate low-pressure steam at 0.25MPaG.

[0016] 3) Absorption system After the reaction, the gas is cooled to 30-40℃ via heat exchange before entering the absorption tower. The absorption tower uses a three-stage absorption and condensation method to condense and absorb all the acetaldehyde and ethanol in the reaction gas. The 12wt% acetaldehyde solution overflowing from the bottom of the absorption tower enters the dilute aldehyde buffer tank.

[0017] 4) Acetaldehyde distillation column The material in the dilute aldehyde buffer tank, after preheating, enters the acetaldehyde distillation column. The acetaldehyde distillation column operates under 0.15 MPaG pressure distillation. The vapor phase at the top of the column is condensed by circulating water and then enters the acetaldehyde distillation column reflux tank. After being pressurized by the reflux pump, part of the vapor returns to the top of the acetaldehyde distillation column, and the rest is collected as product. The bottom material contains almost no acetaldehyde and is sent to the ethanol recovery column.

[0018] 5) Ethanol recovery tower The ethanol solution collected from the bottom of the acetaldehyde distillation column is fed into the ethanol recovery column to recover ethanol. The ethanol recovery column operates under atmospheric pressure distillation. The vapor phase at the top of the column is condensed after heat exchange with circulating water. The condensed ethanol solution enters the ethanol distillation column reflux tank. The material in the ethanol recovery column reflux tank is pressurized by a reflux pump, with part returning to the top of the ethanol recovery column and the rest sent to the ethanol evaporator. The acidic wastewater from the bottom of the column is cooled to 40°C after heat exchange with dilute acetaldehyde and then sent to the wastewater treatment unit.

[0019] This invention increases the operating pressure of the ethanol recovery tower to 0.02-0.3 MPa, and the tower top temperature to 85-110℃. An additional ethanol circulation pump is added to pressurize the ethanol solution at the bottom of the ethanol evaporator and send it to the ethanol evaporator where it reacts with ethanol at 70-75℃. Utilizing the vapor phase at the top of the ethanol tower as a heat source for ethanol evaporation saves low-pressure steam and also reduces the consumption of circulating water in the ethanol recovery tower condenser. Taking a 30,000-ton acetaldehyde plant as an example, compared to existing processes, this invention reduces steam consumption by 46.9% to 3.5 t / h and circulating water consumption by 36.6% to 590 t / h.

[0020] This invention combines the collection of low-pressure steam condensate from the device with heat exchange with the feed to the acetaldehyde distillation column, further increasing the feed temperature and reducing steam consumption in the reboiler. The exhaust gas discharged from the top of the absorption tower mainly consists of nitrogen, hydrogen, CO, and CO2, which is sent to the exhaust gas incinerator, producing low-pressure steam as a byproduct. This steam is then used in the acetaldehyde unit.

[0021] The above description is merely a preferred embodiment of the present utility model, and should not be construed as limiting the scope of the present utility model. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present utility model, and these improvements and modifications are also considered to be within the scope of protection of the present utility model.

Claims

1. An energy-saving acetaldehyde production process device, characterized in that: This includes an ethanol evaporator, oxidizer, absorption tower, acetaldehyde distillation tower, and ethanol recovery tower. The bottom of the ethanol evaporator is provided with an ethanol inlet and an air inlet, and the air inlet extends into the liquid surface of the ethanol evaporator through a pipe; the top of the ethanol evaporator is provided with an ethanol vapor outlet, which is connected to the oxidizer through a pipe. The oxidizer has an oxidation product outlet at the bottom, which is connected to the middle section of the absorption tower via a pipe; a first tail gas condenser and a second tail gas condenser are also provided on the pipe connecting the oxidation product outlet to the absorption tower. The top of the absorption tower is provided with a spray water inlet and a tail gas outlet, and the bottom is provided with an acetaldehyde solution outlet. The acetaldehyde solution outlet is connected to the first tail gas condenser through a pipeline for heat exchange and then connected to the middle section of the acetaldehyde distillation tower. The acetaldehyde distillation column is provided with an acetaldehyde product outlet pipe at the top and a bottom liquid outlet at the bottom. The acetaldehyde product outlet pipe is also provided with an acetaldehyde distillation condenser and a bypass pipe connected to the top of the acetaldehyde distillation column. The bottom liquid outlet is connected to the middle section of the ethanol recovery column through a pipeline. The ethanol recovery tower is provided with a wastewater outlet and an ethanol recovery outlet pipe at its bottom and top, respectively. The ethanol recovery outlet pipe is equipped with an ethanol recovery tower condenser. The ethanol recovery outlet pipe is connected to the ethanol evaporator and the top of the ethanol recovery tower through pipelines. The bottom of the ethanol evaporator is also connected to the condenser of the ethanol recovery tower via a pipe to achieve heat exchange with the ethanol recovery liquid.

2. The energy-saving acetaldehyde production process apparatus according to claim 1, characterized in that: A condensate heat exchanger is also installed on the pipeline connecting the acetaldehyde solution outlet of the absorption tower to the acetaldehyde distillation tower. The condensate heat exchanger is located after the first tail gas condenser.

3. The energy-saving acetaldehyde production process apparatus according to claim 1, characterized in that: The ethanol recovery and extraction pipe and the ethanol inlet are equipped with an ethanol mixer before entering the ethanol evaporator.

4. The energy-saving acetaldehyde production process apparatus according to claim 1, characterized in that: The pipeline connecting the ethanol evaporator and the oxidizer is also equipped with a feed superheater.

5. The energy-saving acetaldehyde production process apparatus according to claim 1, characterized in that: The absorption tower is equipped with three spray condensation absorption sections.

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