CN111253203A - A process for optimizing heat exchange in crude benzene distillation section - Google Patents

Abstract

The invention relates to the technical field of crude benzene distillation heat exchange, in particular to a heat exchange optimization process for a crude benzene distillation working section. The temperature of the mixture of oil gas and water vapor is reduced by circulating water at the temperature lower than 32 ℃ in a benzene-water heat exchanger, and the temperature of the hot lean oil is improved from the temperature reduction by heat exchange with rich oil at the temperature of about 70 ℃ to the temperature reduction by heat exchange with rich oil at the temperature of about 30 ℃; the heat transfer coefficient of the lean-rich heat exchanger is increased by changing the heat lean oil pump to the front of the lean-rich heat exchanger. The invention solves the problem of poor heat exchange effect of the mixture of oil gas and water vapor and rich oil at about 30 ℃ in the oil gas heat exchanger, and solves the problem that the quality and yield of crude benzene are influenced when the rich oil leaked from the oil gas heat exchanger enters the benzene-water mixture; the problem of poor heat exchange and temperature reduction effects of hot lean oil and rich oil at about 70 ℃ is solved; the problem of low heat transfer coefficient when the hot lean oil automatically flows into the lean rich oil heat exchanger is solved; the problem that the benzene content of lean oil is influenced when the lean oil enters the lean oil due to the leakage of the rich oil from the lean-rich oil heat exchanger is solved.

Description

A process for optimizing heat exchange in crude benzene distillation section

technical field

The invention relates to the technical field of crude benzene distillation heat exchange, in particular to a process for optimizing heat exchange in a crude benzene distillation section.

Background technique

At present, the crude benzene distillation process of the coking plant is as follows:

About 30°C rich oil from the benzene washing process first enters the oil and gas heat exchanger, exchanges heat with the oil and gas and water vapor mixture from the top of the debenzene tower, and then heats up to about 70°C, and then enters the lean and rich oil heat exchanger to be removed from the bottom of the benzene tower. The discharged hot lean oil is heated to 150-160 ℃, and then enters the tube furnace.

The 90-93 ℃ oil-gas and water-vapor mixture escaped from the top of the debenzene tower enters the oil-gas heat exchanger to exchange heat with the rich oil, and then enters the condensing cooler to be condensed and cooled by low-temperature water, and the condensate enters the oil-water separator.

The hot lean oil discharged from the bottom of the benzene removal tower flows to the lean and rich oil heat exchanger and exchanges heat with the rich oil, and then uses the hot lean oil pump to pass through the lean oil first-stage cooler and the lean oil second-stage cooler for cooling with circulating water and low-temperature water respectively. After the benzene washing process, it is recycled.

However, the problems with this heat exchange method are:

1. The oil-gas and water-vapor mixture in the oil-gas heat exchanger exchanges heat with the rich oil at about 30°C in the oil-gas heat exchanger, and the heat exchange effect is not good. If the oil-gas heat exchanger leaks, the rich oil will be mixed into the benzene-water mixture. Benzene needs to be returned to the system, which affects the quality and yield of crude benzene.

2. The hot lean oil exchanges heat with the rich oil at about 70°C. The temperature drop of the hot lean oil is small. It is difficult to reach below 30°C after the heat exchange between the circulating water and the low temperature water. It flows into the lean-rich oil heat exchanger, so the heat transfer coefficient is low, and if the lean-rich oil heat exchanger leaks, the rich oil will leak into the lean oil due to the high pressure of the rich oil, resulting in an increase in the benzene content of the lean oil. High, affecting the washing effect of benzene, thereby affecting the yield of crude benzene.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a process for optimizing heat exchange in the distillation section of crude benzene. Solve the problem that the oil-gas and water-vapor mixture and the rich oil of about 30℃ have poor heat exchange effect in the oil-gas heat exchanger, and solve the problem that the oil-gas heat exchanger leaks the rich oil into the benzene-water mixture and affects the quality and yield of crude benzene; Solved the problem of poor heat exchange and cooling effect between hot lean oil and rich oil at about 70°C; solved the problem of low heat transfer coefficient of hot lean oil self-flow into the lean and rich oil heat exchanger; solved the leakage of rich and lean oil heat exchanger. The problem that the oil enters the lean oil affects the benzene content of the lean oil.

The specific technical solutions are as follows:

A process for optimizing heat exchange in a crude benzene distillation section, characterized in that the mixture of oil and gas and water vapor at 90-93° C. escaped from the top of a debenzene tower is cooled by circulating water below 32° C. in a benzene-water heat exchanger before entering The condensing cooler is condensed and cooled with low-temperature water, and the condensate enters the oil-water separator; the hot lean oil discharged from the bottom of the benzene removal tower is pressurized by the hot lean oil pump, and then enters the lean and rich oil heat exchanger and is cooled by about 30°C rich oil from the benzene washing process. After that, the first-stage cooler of lean oil and the second-stage cooler of lean oil are cooled with circulating water and low-temperature water, respectively, and then used for washing in the benzene process; the rich oil heated by the hot lean oil enters the tube furnace; the hot lean oil pump is changed to the lean oil pump. Before the rich oil heat exchanger, the heat transfer coefficient of the lean rich oil heat exchanger is increased.

Compared with the prior art, the present invention has the following beneficial technical effects:

1. The mixture of oil and gas and water vapor is cooled by circulating water below 32°C in the benzene water heat exchanger. Because the specific heat capacity of water is larger than that of oil-rich, the heat exchange effect is better than that of oil-rich at about 30°C.

2. The leakage of oil and gas heat exchanger is due to the high pressure of circulating water, so the circulating water enters the benzene-water mixture, which will not affect the quality and yield of crude benzene, because water can be separated from benzene in the oil-water separator.

3. The heat exchange and cooling effect between hot lean oil and about 30℃ rich oil is better than that with about 70℃ rich oil.

4. The hot lean oil pump is changed before the lean rich oil heat exchanger, which increases the heat transfer coefficient of the lean rich oil heat exchanger.

5. If the lean and rich oil heat exchanger leaks, because the lean oil pressure is higher than the rich oil pressure, the lean oil enters the rich oil, which will not affect the benzene content of the lean oil.

Description of drawings

Fig. 1 is the heat exchange process flow chart of the prior art;

Fig. 2 is the heat exchange process flow diagram after the improvement and optimization of the crude benzene distillation section.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited by the accompanying drawings and specific embodiments.

Fig. 1 is the heat exchange process flow diagram of the prior art, as shown in the figure, the crude benzene distillation process flow of the coking plant is as follows at present:

About 30°C rich oil from the benzene washing process first enters the oil and gas heat exchanger, exchanges heat with the oil and gas and water vapor mixture from the top of the debenzene tower, and then heats up to about 70°C, and then enters the lean and rich oil heat exchanger to be removed from the bottom of the benzene tower. The discharged hot lean oil is heated to 150-160 ℃, and then enters the tube furnace.

The 90-93 ℃ oil-gas and water-vapor mixture escaped from the top of the debenzene tower enters the oil-gas heat exchanger to exchange heat with the rich oil, and then enters the condensing cooler to be condensed and cooled by low-temperature water, and the condensate enters the oil-water separator.

The hot lean oil discharged from the bottom of the benzene removal tower flows to the lean and rich oil heat exchanger and exchanges heat with the rich oil, and then uses the hot lean oil pump to pass through the lean oil first-stage cooler and the lean oil second-stage cooler for cooling with circulating water and low-temperature water respectively. After the benzene washing process, it is recycled.

Fig. 2 is the heat exchange process flow chart after the improvement and optimization of the crude benzene distillation section, as shown in the figure, the improved crude benzene distillation section heat exchange process of the present invention is optimized, and the 90-93 ℃ of oil and gas escaping from the top of the debenzene tower and The water-vapor mixture is cooled by the circulating water below 32℃ in the benzene-water heat exchanger, and then enters the condensing cooler to be condensed and cooled by low-temperature water, and the condensate enters the oil-water separator; After pressing, it enters the lean-rich oil heat exchanger and cools the rich oil at about 30°C from the benzene washing process, and then passes through the lean oil first-stage cooler and the lean-oil second-stage cooler with circulating water and low-temperature water, respectively, and then goes to the benzene washing process. Use; the rich oil heated by the hot lean oil enters the tube furnace; the hot lean oil pump is changed before the lean rich oil heat exchanger, which increases the heat transfer coefficient of the lean rich oil heat exchanger.

Claims (2)

1. a crude benzene distillation section heat-exchange optimization process, is characterized in that: after the 90-93 ℃ of oil and gas and the water-vapor mixture that the debenzene tower top escapes are cooled by the circulating water lower than 32 ℃ in the benzene water heat exchanger Then enter the condensing cooler with low-temperature water for condensation cooling, and the condensate enters the oil-water separator; the hot lean oil discharged from the bottom of the benzene removal tower is pressurized by the hot lean oil pump and then enters the lean and rich oil heat exchanger and the about 30 ℃ rich oil from the benzene washing process. After the oil is cooled, the first-stage cooler of lean oil and the second-stage cooler of lean oil are cooled with circulating water and low-temperature water, respectively, and then used in the benzene washing process; the rich oil heated by hot lean oil enters the tube furnace. 2. The process of optimizing heat exchange in crude benzene distillation section according to claim 1, characterized in that: the hot lean oil pump is changed before the lean and rich oil heat exchanger to increase the heat transfer coefficient of the lean and rich oil heat exchanger.

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