A semi-rich oil heat exchange system for benzene washing process

Abstract

The present application relates to a kind of semi-rich oil heat exchange system of washing benzene process, including semi-rich oil heat exchanger, change-over switch, medium-temperature lean oil regulating system and low-temperature water regulating system, semi-rich oil heat exchanger is set between two-stage series washing benzene tower, by change-over switch control medium-temperature lean oil regulating system work or low-temperature water regulating system work, to make semi-rich oil heat exchanger heat semi-rich oil or cool semi-rich oil. When using a small amount of low-temperature water to cool semi-rich oil in hot summer, semi-rich oil is heated by medium-temperature lean oil of about 40 DEG C in cold winter, while reducing the low-temperature water consumption of lean oil cryogenic device, energy saving and cost reduction. The present application can control the washing oil at 25-28 DEG C, to improve the absorption effect of benzene on benzene, increase the yield of crude benzene, with good economy, simple process, reasonable structure, flexible operation, easy to maintain, at the same time, the device is convenient to transform on the basis of original system, and the change amount is small, easy to popularize and realize.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coke oven gas purification, in particular to a semi-rich oil heat exchange system for benzene washing process. BACKGROUND

[0002] In the coke oven gas purification process, the final cooling benzene washing process is mainly responsible for the absorption of benzene hydrocarbons in the gas, which belongs to a physical absorption process. Research shows that the following important factors affect the benzene washing effect and the benzene yield:

[0003] 1) the quality of the washing oil;

[0004] 2) the washing oil circulation amount;

[0005] 3) the absorption temperature (the temperature of the gas and the washing oil);

[0006] 4) the structure and the packing of the benzene washing tower.

[0007] The gas is first cooled to about 25 DEG C by the final cooling tower or the final cooling device, and the regulating valve is arranged on the low-temperature water pipeline of the final cooling device. The temperature and the low-temperature water flow are adjusted in series, and the temperature is relatively stable. The benzene in the final cooled gas is removed by the benzene washing tower, and the washing oil circulation amount and the structure and the packing of the benzene washing tower are determined by design and are strictly calculated, which can usually meet the production needs. Therefore, in the production process, the washing oil temperature is the biggest factor affecting the benzene washing effect and the benzene yield. The relevant data and production experience show that the absorption effect of the washing oil on the benzene hydrocarbons is the best when the average temperature of the washing oil is 25-28 DEG C.

[0008] In spring and autumn, when the temperature is suitable, the temperature of the gas and the washing oil remains basically unchanged after passing through the benzene washing tower, and the operation of each index is stable. In summer and winter, due to the solar radiation or the low ambient temperature, the benzene washing tower and the pipeline are equivalent to a huge heat exchange device, which causes the change of the benzene washing temperature and reduces the benzene washing efficiency. Especially for the benzene washing tower with stainless steel corrugated plate packing, the temperature change is larger due to the higher metal heat transfer coefficient. For the two-stage series benzene washing tower, the temperature of the washing oil changes greatly after passing through the 2# benzene washing tower, and the washing oil enters the 1# benzene washing tower, which will seriously affect the benzene washing effect. SUMMARY

[0009] In order to overcome the defects of the prior art, the technical problem solved by the present application is to provide a semi-rich oil heat exchange system for benzene washing process, which increases the semi-rich oil heat exchanger between the two-stage series benzene washing towers, and uses the medium-temperature lean oil with a temperature of about 40 DEG C from the low-temperature water or the lean oil cooler to cool or heat the semi-rich oil, so as to improve the benzene washing effect of the system and increase the benzene yield.

[0010] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0011] The application discloses a semi-rich oil heat exchange system for a benzene washing process, which comprises a pre-heat exchange pipeline of medium-temperature lean oil, a return pipeline, a switch, a temperature meter, a post-heat exchange pipeline of medium-temperature lean oil, a low-temperature water feeding pipeline, a low-temperature water return pipeline, a semi-rich oil heat exchanger, a medium-temperature lean oil adjusting system and a low-temperature water adjusting system, wherein the semi-rich oil heat exchanger is arranged between a first benzene washing tower and a second benzene washing tower which are connected in series; the medium-temperature lean oil adjusting system is composed of a lean oil valve, a lean oil adjusting valve and a lean oil flowmeter, wherein the lean oil valve, the lean oil adjusting valve and the lean oil flowmeter are sequentially connected and arranged on the pre-heat exchange pipeline of medium-temperature lean oil, one end of the pre-heat exchange pipeline of medium-temperature lean oil is connected with a tube side inlet of the semi-rich oil heat exchanger, and the other end is connected with a pipeline between a lean oil cooler and a lean oil cryogenic cooler; one end of the return pipeline is connected with the pre-heat exchange pipeline of medium-temperature lean oil before the lean oil adjusting valve, and the other end is connected with a pipeline before the lean oil cryogenic cooler; the low-temperature water adjusting system is composed of a low-temperature water valve, a low-temperature water adjusting valve and a low-temperature water flowmeter, wherein the low-temperature water valve, the low-temperature water adjusting valve and the low-temperature water flowmeter are sequentially connected and arranged on the low-temperature water feeding pipeline of the tube side inlet of the semi-rich oil heat exchanger; the low-temperature water return pipeline is connected with a tube side outlet of the semi-rich oil heat exchanger; one end of the post-heat exchange pipeline of medium-temperature lean oil is connected with the tube side outlet of the semi-rich oil heat exchanger, and the other end is connected with the pipeline before the lean oil cryogenic cooler; an inlet and an outlet of a shell side of the semi-rich oil heat exchanger are connected with a semi-rich oil pipeline between the first benzene washing tower and the second benzene washing tower; and the temperature meter is arranged on the semi-rich oil pipeline at an outlet end of the semi-rich oil heat exchanger.

[0012] The lean oil valve, the lean oil adjusting valve, the lean oil flowmeter, the low-temperature water valve, the low-temperature water adjusting valve, the low-temperature water flowmeter and the temperature meter are in interlocked control with the switch.

[0013] The switch controls the medium-temperature lean oil adjusting system or the low-temperature water adjusting system to work, so that the semi-rich oil heat exchanger heats or cools the semi-rich oil.

[0014] A medium-temperature lean oil communication pipeline valve is arranged between the lean oil cryogenic cooler and the lean oil cooler.

[0015] The semi-rich oil heat exchanger has a suitable temperature of about 25 DEG C for cooling the semi-rich oil in summer and a suitable temperature of about 28 DEG C for heating the semi-rich oil in winter.

[0016] The semi-rich oil heat exchanger preferably selects a spiral plate heat exchanger, and the spiral plate heat exchanger has low cost and high heat transfer efficiency.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] 1) The semi-rich oil heat exchanger is arranged between the two-stage series connection benzene washing towers, and the medium-temperature lean oil with a temperature of about 40 DEG C from the outlet of the low-temperature water or the lean oil cooler is used to cool or heat the semi-rich oil.

[0019] 2) The present application can control the washing oil at 25-28 DEG C, so as to improve the absorption effect of the washing oil on benzene substances, increase the crude benzene yield, and have good economy;

[0020] 3) The same heat exchanger is used for the semi-rich oil heated by the medium-temperature lean oil and the semi-rich oil cooled by the low-temperature water, and the dual functions are realized by switching through valves and instruments;

[0021] 4) The process is simple, the structure is reasonable, the operation is flexible, and the maintenance is convenient;

[0022] 5) The device is convenient to transform on the basis of the original system, has small change amount, is easy to realize, and is suitable for promotion. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the structural principle schematic diagram of the present application.

[0024] In the figure: 1 - the pipeline before medium-temperature lean oil heat exchange 2 - the lean oil communication valve 3 - the lean oil valve 4 - the lean oil regulating valve 5 - the lean oil flowmeter 6 - the return pipe 7 - the conversion switch 8 - the temperature table 9 - the pipeline after medium-temperature lean oil heat exchange 10 - the low-temperature water up-pipe 11 - the low-temperature water valve 12 - the low-temperature water regulating valve 13 - the low-temperature water flowmeter 14 - the low-temperature water return pipe 15 - the semi-rich oil heat exchanger 16 - the lean oil cryogenic cooler 17 - the lean oil cooler 18 - 1# benzene washing tower 19 - 2# benzene washing tower 20 - the semi-rich oil pipe pipeline DETAILED DESCRIPTION

[0025] The specific embodiment of the present application is further described below in combination with the drawings:

[0026] See Figure 1As shown, the present application relates to a semi-rich oil heat exchange system for benzene washing process, which comprises a pre-poor oil heat exchange pipeline 1, a return pipeline 6, a switch 7, a temperature meter 8, a post-poor oil heat exchange pipeline 9, a low-temperature water feeding pipeline 10, a low-temperature water return pipeline 14, a semi-rich oil heat exchanger 15, a poor oil regulating system and a low-temperature water regulating system, the semi-rich oil heat exchanger 15 is arranged between a first benzene washing tower 18 and a second benzene washing tower 19 in series, the poor oil regulating system is composed of a poor oil valve 3, a poor oil regulating valve 4 and a poor oil flowmeter 5, wherein the poor oil valve 3, the poor oil regulating valve 4 and the poor oil flowmeter 5 are sequentially connected and arranged on the pre-poor oil heat exchange pipeline 1, one end of the pre-poor oil heat exchange pipeline 1 is connected with a tube pass inlet of the semi-rich oil heat exchanger 15, and the other end is connected with a pipeline between a poor oil cooler 16 and a poor oil cryogenic cooler 17, one end of the return pipeline 6 is connected with the pre-poor oil heat exchange pipeline 1 before the poor oil regulating valve 4, and the other end is connected with a pipeline before the poor oil cryogenic cooler 17, so as to send the excess poor oil back to the pipeline before the poor oil cryogenic cooler 17 for further cooling, the low-temperature water regulating system is composed of a low-temperature water valve 11, a low-temperature water regulating valve 12 and a low-temperature water flowmeter 13, wherein the low-temperature water valve 11, the low-temperature water regulating valve 12 and the low-temperature water flowmeter 13 are sequentially connected and arranged on the low-temperature water feeding pipeline 10 of the tube pass inlet of the semi-rich oil heat exchanger 15, the low-temperature water return pipeline 14 is connected with a tube pass outlet of the semi-rich oil heat exchanger 15, one end of the post-poor oil heat exchange pipeline 9 is connected with the tube pass outlet of the semi-rich oil heat exchanger 15, and the other end is connected with the pipeline before the poor oil cryogenic cooler 17, the inlet and the outlet of the shell pass of the semi-rich oil heat exchanger 15 are connected with a semi-rich oil pipeline 20 between the first benzene washing tower 18 and the second benzene washing tower 19, and the temperature meter 8 is arranged on the semi-rich oil pipeline 20 at the outlet end of the semi-rich oil heat exchanger 15.

[0027] The poor oil valve 3, the poor oil regulating valve 4, the poor oil flowmeter 5, the low-temperature water valve 11, the low-temperature water regulating valve 12, the low-temperature water flowmeter 13 and the temperature meter 8 are interlocked controlled with the switch 7.

[0028] The switch 7 controls the poor oil regulating system or the low-temperature water regulating system (switched between the two in winter and summer) to work, so as to heat the semi-rich oil in winter or cool the semi-rich oil in summer.

[0029] The poor oil cryogenic cooler 17 is provided with a poor oil traffic pipeline valve 2 between the poor oil cooler 16.

[0030] The suitable temperature of the semi-rich oil heat exchanger 15 for cooling the semi-rich oil in summer is about 25℃, and the suitable temperature of the semi-rich oil heat exchanger 15 for heating the semi-rich oil in winter is about 28℃.

[0031] The semi-rich oil heat exchanger 15 is preferably a spiral plate heat exchanger, which has low cost and high heat transfer efficiency.

[0032] Example The circulating amount of the wash oil in a certain plant: 110 m 2 / h, and the packing in the benzene washing tower is stainless steel corrugated plate.

[0033] In winter, the extreme outdoor temperature is -28.8℃, at this time, the temperature of the poor oil entering the 2# benzene washing tower 19 is about 27℃, after passing through the 2# benzene washing tower 19, the temperature of the poor oil is reduced to about 21℃, which affects the benzene washing effect of the 1# benzene washing tower 18. At the same time, it brings a series of problems, such as the condensation of water in the coal gas after the temperature is reduced, the increase of the water content in the rich oil, which affects the stable operation of the crude benzene distillation, and at the same time, it brings the vibration of the rich oil pipeline, which brings certain safety hazards. If the temperature of the poor oil entering the 2# benzene washing tower 19 is increased, the benzene washing effect of the 1# benzene washing tower 18 is correspondingly improved, but the benzene washing effect of the 2# benzene washing tower 19 is reduced; therefore, the overall benzene removal effect after the series connection is poor.

[0034] In summer, the extreme outdoor temperature is -37.2℃, at this time, the temperature of the poor oil entering the 2# benzene washing tower 19 is about 27℃, after passing through the 2# benzene washing tower 19, the temperature of the poor oil is increased to about 33℃, which affects the benzene washing effect of the 1# benzene washing tower 18. If the temperature of the poor oil entering the 2# benzene washing tower 19 is reduced, the benzene washing effect of the 1# benzene washing tower 18 is correspondingly improved, but the benzene washing effect of the 2# benzene washing tower 19 is reduced.

[0035] Similarly, the reduction of the temperature also causes the increase of the water content in the rich oil, which further affects the stable operation of the crude benzene distillation, therefore, the overall benzene removal effect after the series connection is also poor.

[0036] In view of the above situation, a suitable spiral plate heat exchanger is selected, and the calculation process is as follows:

[0037] A. In winter: since the semi-rich oil is heated and then passes through the 1# benzene washing tower, it will continue to be cooled, therefore, the upper limit is suitable, and it is appropriate to heat to about 28℃.

[0038] Poor oil at medium temperature 40℃→33℃

[0039] Semi-rich oil 28℃←21℃

[0040] Calculated temperature difference: △Tm=12℃

[0041] The specific heat of the semi-rich oil is about 1.8kJ / kgK, the specific heat of the poor oil at medium temperature and the specific heat of the semi-rich oil are approximately equal, and the poor oil at medium temperature is calculated to be used for heating, that is, the amount q=110 m 2 / h

[0042] Oil-oil heat exchange, heat transfer coefficient K is 250kcal / m2.℃.h

[0043] Total heat transfer amount: Q=Cp(T2-T1)q=363825kcal / h

[0044] According to Q=KA△Tm, the area of the heat exchanger is calculated: A=122m2

[0045] B. Summer: Since the semi-rich oil heat exchange, still need to go through the 1# washing benzene tower, will continue to warm, so it is appropriate to take the lower limit, heat exchange to ~ 25 ℃ is more appropriate.

[0046] Low temperature water 16 ℃→20 ℃

[0047] Semi-rich oil 25 ℃←33 ℃

[0048] The temperature difference is calculated: △Tm=10.88 ℃

[0049] Semi-rich oil specific heat ~ 1.8 kJ / kgK, low temperature water specific heat ~ 1 kJ / kgK, the amount of low temperature water 104 m 2 / h

[0050] Total heat transfer: Q=Cp(T2-T1)q=415800 kcal / h

[0051] Water-oil heat exchanger, heat transfer coefficient of 350 kcal / m2.℃.h

[0052] The heat exchanger area is calculated: 119 m 2

[0053] For the above example, under extreme conditions, due to the difference in heat transfer area is not big, the fluid flow and flow rate are basically the same, and considering a certain rich capacity, a F=130 m 2 Spiral plate heat exchanger can be selected as a common semi-rich oil cooler 15.

[0054] When working:

[0055] Summer, hot, heat intensity, washing benzene effect decline, open semi-rich oil heat exchanger 15 inlet low temperature water valve (11) and low temperature water return pipe (14) on the valve, semi-rich oil heat exchanger (15) through the low temperature water inlet pipe (10) access to low temperature water cooling, will change the switch (7) into the low temperature water regulating system, according to the semi-rich oil outlet temperature, that is, temperature table (8), semi-rich oil heat exchanger 15 inlet low temperature water regulating valve (12) and semi-rich oil heat exchanger inlet low temperature water flow meter (13) cascade regulation. When stopped, all the valves should be closed and thoroughly vented and purged.

[0056] When the effect of washing benzene is decreased due to cold winter environment and low ambient temperature, open the valve on the inlet lean oil of semi-rich oil heat exchanger 15 (3), the lean oil pipeline (9) after the heat exchange of medium temperature lean oil and the valve on the return pipeline (6), close the valve on the lean oil pipeline (2), semi-rich oil heat exchanger 15 is connected to the medium temperature lean oil heating at about 40℃ through the pipeline (1) before the heat exchange of medium temperature lean oil, connect the switch (7) to the medium temperature lean oil regulating system, according to the semi-rich oil outlet temperature, i.e. the temperature table (8), the cascade regulation is carried out between the semi-rich oil heat exchanger 15 inlet lean oil regulating valve (4) and the semi-rich oil heat exchanger 15 inlet lean oil flowmeter (5). The excess medium temperature lean oil can be returned to the lean oil pipeline after the lean oil cooler 16 through the return pipeline (6) and continue to be cooled in the lean oil cryogenic cooler 17. The regulating valve is arranged on the low temperature water pipeline of the lean oil cryogenic cooler 17, the cascade regulation is carried out between the lean oil temperature into the 2# benzene washing tower and the low temperature water flow, therefore, the lean oil temperature into the 2# benzene washing tower is relatively stable. When the device is stopped, all the valves above should be closed and completely emptied and purged except the valve (2) on the lean oil pipeline.

[0057] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A semi-rich oil heat exchange system for a benzene washing process, comprising a pre-heat exchange pipeline for medium-temperature lean oil, a return pipe, a changeover switch, a thermometer, a post-heat exchange pipeline for medium-temperature lean oil, a low-temperature water supply pipeline, a low-temperature water return pipeline, a semi-rich oil heat exchanger, a medium-temperature lean oil regulating system, and a low-temperature water regulating system, characterized in that, The semi-rich oil heat exchanger is arranged between the 1# benzene washing tower and the 2# benzene washing tower in series; the medium-temperature lean oil regulating system is composed of a lean oil valve, a lean oil regulating valve and a lean oil flowmeter, wherein the lean oil valve, the lean oil regulating valve and the lean oil flowmeter are sequentially connected and arranged on a medium-temperature lean oil pre-heat pipeline, one end of the medium-temperature lean oil pre-heat pipeline is connected with a tube side inlet of the semi-rich oil heat exchanger, the other end is connected with a pipeline between the lean oil cooler and the lean oil cryogenic cooler, one end of a return pipeline is connected with the medium-temperature lean oil pre-heat pipeline before the lean oil regulating valve, the other end is connected with a pipeline before the lean oil cryogenic cooler; the low-temperature water regulating system is composed of a low-temperature water valve, a low-temperature water regulating valve and a low-temperature water flowmeter, wherein the low-temperature water valve, the low-temperature water regulating valve and the low-temperature water flowmeter are sequentially connected and arranged on a low-temperature water up-pipeline of the tube side inlet of the semi-rich oil heat exchanger; a low-temperature water return pipeline is connected with a tube side outlet of the semi-rich oil heat exchanger; one end of a medium-temperature lean oil post-heat pipeline is connected with the tube side outlet of the semi-rich oil heat exchanger, the other end is connected with a pipeline before the lean oil cryogenic cooler; an inlet and an outlet of a shell side of the semi-rich oil heat exchanger are connected with a semi-rich oil pipeline between the 1# benzene washing tower and the 2# benzene washing tower; a temperature table is arranged on a semi-rich oil pipeline at an outlet end of the semi-rich oil heat exchanger. The suitable temperature of the semi-rich oil heat exchanger for cooling the semi-rich oil in summer is 25℃, and the suitable temperature of the semi-rich oil heat exchanger for heating the semi-rich oil in winter is 28℃; the semi-rich oil heat exchanger is a spiral plate heat exchanger.

2. A semi-rich oil heat exchange system for a benzene washing process according to claim 1, characterized in that, The lean oil valve, the lean oil regulating valve, the lean oil flowmeter, the low-temperature water valve, the low-temperature water regulating valve, the low-temperature water flowmeter and the temperature table are interlocked controlled by the change-over switch.

3. A semi-rich oil heat exchange system for a benzene washing process according to claim 1, characterized in that, The change-over switch controls the medium-temperature lean oil regulating system or the low-temperature water regulating system to work, so that the semi-rich oil heat exchanger heats or cools the semi-rich oil.

4. A semi-rich oil heat exchange system for a benzene washing process according to claim 1, characterized in that, A medium-temperature lean oil communication pipeline valve is arranged between the lean oil cryogenic cooler and the lean oil cooler.

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