Negative-pressure crude benzene distillation process and system adopting tubular furnace for heating

Abstract

The invention relates to a negative pressure crude benzene distillation process and system adopting a tubular furnace for heating. The system comprises a debenzolization tower, a tubular furnace and a crude benzene condensation, cooling and separation integrated device, the debenzolization tower is sequentially provided with a rectifying section, a stripping section, a storage tank section and a regeneration section from top to bottom; the crude benzene condensing, cooling and separating integrated device comprises a heat exchange tower and a separating tank; a low-temperature water heat exchanger is arranged at the lower part of the heat exchange tower; a crude benzene collecting section, an oil-gas-water separating section and a water collecting section are arranged in the separating tank; a first heating section and a second heating section are arranged in the tubular furnace. Compared with an existing negative-pressure crude benzene distillation process, the method has the remarkable advantages that the tail gas output is low, the tail gas is not discharged, the tube furnace operation temperature is low, the washing oil consumption is small, no additional separated water is generated, and the one-time investment is low.

Description

Technical Field

[0001] The invention relates to the technical field of coking product recovery, and in particular to a negative pressure crude benzene distillation process and system using tubular furnace heating. Background Art

[0002] There are two methods for crude benzene distillation in the coking industry: positive pressure crude benzene distillation (also known as normal pressure crude benzene distillation) and negative pressure crude benzene distillation. The positive pressure crude benzene distillation process uses superheated steam to distill at a pressure of 30-50kPa. The disadvantage of this process is that it consumes a lot of energy and also produces a large amount of difficult-to-handle crude benzene separation water. The negative pressure crude benzene distillation process uses vacuum distillation, which uses the principle of reducing the boiling point of the liquid by reducing the liquid surface pressure. A vacuum device is used to extract non-condensable gas at the top of the tower to reduce the liquid surface pressure in the tower to achieve a negative pressure state, thereby saving heat for distillation and improving the separation effect. Circulating hot lean oil is used to provide heat. Therefore, compared with the positive pressure crude benzene distillation method, it can greatly reduce the generation of wastewater and greatly reduce operating costs.

[0003] At present, there are mainly three processes for negative pressure crude benzene distillation:

[0004] The first is a negative pressure crude benzene distillation process that uses the lean oil at the bottom of the distillation tower to be heated in a tubular furnace as a heat source. The process heat is brought into the debenzene tower by the lean oil heated by coal gas in the tubular furnace. The rising airflow in the debenzene tower is mainly crude benzene gas and partially vaporized wash oil. The advantage of this process is that no additional crude benzene separation water is produced, and the coke oven gas produced by the coking plant can be used as a heat source. The disadvantage is that a large amount of tail gas will be generated after the coal gas is burned in the tubular furnace, and the emission indicators are difficult to meet environmental protection standards, and the additional construction of the tail gas treatment system will increase investment. In addition, the process uses coal gas for indirect heating, and the wall temperature of the heat exchange tube is high, resulting in a large amount of slagging and high consumption of the wash oil.

[0005] The second is a negative pressure crude benzene distillation process using superheated steam as a direct heat source. The process heat is brought into the debenzene tower through superheated steam. The rising airflow in the debenzene tower is crude benzene gas, partially vaporized gasoline and superheated steam. The advantages of this process are low operating temperature of the debenzene tower and low consumption of wash oil; the disadvantage is that crude benzene separation water is produced during the debenzene of rich oil, which increases the production load of subsequent wastewater treatment.

[0006] The third is the negative pressure crude benzene distillation process using the reboiler method, which uses steam to heat the circulating wash oil at the bottom of the tower to provide heat for the debenzene tower. The rising airflow in the debenzene tower is mainly crude benzene gas and partially vaporized wash oil. The advantage of this process is that there is no combustion tail gas and no additional crude benzene separation water; the disadvantage is that the heating steam consumption is large and the operating cost is high.

[0007] In summary, the current crude benzene distillation process mainly has three problems: it is difficult to meet environmental protection index requirements, the construction investment is large, and the operating cost is high. In addition, the previous crude benzene distillation process also has the following common characteristics:

[0008] 1) Due to process requirements, a civil construction frame needs to be set up outside the debenzene tower to install the gas-liquid separator and the oil-water separator, which requires a large initial investment and a long construction period;

[0009] 2) The debenzene tower internals use trays, or the stripping section uses fillers and the rectifying section uses trays. The advantage of using fillers is that the tower height and tower resistance can be reduced, but the disadvantage is that it is difficult to set up the naphthalene extraction line in the rectifying section. If all the debenzene tower internals use fillers, naphthalene can still be extracted from the side line, which will reduce the equipment's one-time investment and on-site installation time. Summary of the invention

[0010] The present invention provides a negative pressure crude benzene distillation process and system using tubular furnace heating. Compared with the existing negative pressure crude benzene distillation process, the system has the advantages of low tail gas generation and no exhaust of tail gas, low operating temperature of the tubular furnace, small consumption of wash oil, no additional separation water generation, and low one-time investment.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A negative pressure crude benzene distillation process using a tubular furnace for heating includes the following steps:

[0013] 1) The debenzene tower is provided with a rectifying section, a stripping section, a storage tank section and a regeneration section from top to bottom; the rectifying section and the stripping section are both provided with fillers; the regeneration section is provided with a heater; the rich oil sent from the benzene washing unit is heat exchanged with the hot lean oil discharged from the bottom of the debenzene tower through the lean-rich oil heat exchanger, and then enters the stripping section of the debenzene tower for distillation; a part of the hot lean oil at the bottom of the debenzene tower is pumped out by the lean oil pump, and is cooled in three stages in sequence through the lean-rich oil heat exchanger, the lean oil cooler and the lean oil deep freezer, and then sent to the benzene washing unit;

[0014] 2) Another part of the hot lean oil at the bottom of the debenzene tower is pumped out by the lean oil circulation pump and sent to the tubular furnace for heating in two parts; most of the lean oil is heated and sent to the storage tank section of the debenzene tower for flash evaporation as a heat source for distillation; a small part of the lean oil is heated and sent to the heater in the regeneration section at the bottom of the debenzene tower as a heat source for washing oil regeneration;

[0015] 3) The crude benzene vapor extracted from the top of the debenzene tower enters the crude benzene condensation, cooling and separation integrated device, and then enters the separation tank at the bottom after heat exchange with circulating water and low-temperature water in turn; the separation tank is provided with a crude benzene collection section, an oil-gas-water separation section and a water collection section; the crude benzene after heat exchange and condensation directly enters the oil-gas-water separation section, and the crude benzene, non-condensable gas and water are separated by standing, and the separated non-condensable gas is further heat exchanged with low-temperature water and deep cooled, and then pumped out by a vacuum pump and sent to the benzene washing unit; the separated crude benzene overflows into the crude benzene collection section, and a part is pumped out by a benzene pump and sent to the top of the debenzene tower as reflux; the other part is sent to the crude benzene storage tank of the oil depot unit as a crude benzene product; the separated water overflows to the water collection section, and is pumped out by a separation water pump and sent to the coal gas final cooling unit;

[0016] 4) draw the naphthalene oil fraction at the rectifying section side line of the debenzene tower, the naphthalene oil fraction drawn enters the residue tank, and is regularly delivered to the tar storage tank of the oil depot unit by the residue pump;

[0017] 5) A small amount of hot lean oil is drawn from the circulating heating oil and sent to the regeneration section at the bottom of the debenzene tower, where it is heated by the heater, and the evaporated oil-gas mixed steam is also sent to the bottom of the debenzene tower as a heat source;

[0018] 6) The tubular furnace uses the reaction heat of combustion of coal gas and air as the heat source; part of the exhaust gas after combustion is sent to the desulfurization and denitrification device for purification, and the other part is returned to the air duct upstream of the air blower, mixed with the newly entered air, and then sent to the tubular furnace as a combustion-supporting gas.

[0019] A negative pressure crude benzene distillation system using tubular furnace heating, comprising a debenzene tower, a tubular furnace and a crude benzene condensation, cooling and separation integrated device; the debenzene tower is provided with a rectification section, a stripping section, a storage tank section and a regeneration section in sequence from top to bottom; wherein the rectification section and the stripping section are both provided with fillers; a reflux crude benzene distributor is provided at the top of the rectification section, an oil-rich distributor is provided at the top of the stripping section, and a hot lean oil distributor is provided at the top of the storage tank section; a heater is provided in the regeneration section; the storage tank section and the regeneration section are connected by a circulating lean oil pipeline; the crude benzene condensation, cooling and separation integrated device comprises a heat exchange tower and a separation tank; a circulating water heat exchanger is provided at the upper part of the heat exchange tower, and a low-temperature water heat exchanger is provided at the lower part; a crude benzene collecting section, an oil-gas-water separation section and a water collecting section are provided in the separation tank; the bottom of the heat exchange tower is connected to the top of the oil-gas-water separation section; a low-temperature water-non-condensable gas heat exchanger is provided in the separation tank above the oil-gas-water separation section; a heating section 1 and a heating section 2 are provided in the tubular furnace;

[0020] The rich oil inlet of the rich oil distributor is connected to the rich oil outlet of the lean-rich oil heat exchanger, and the rich oil inlet of the lean-rich oil heat exchanger is connected to the rich oil outlet pipeline of the benzene washing unit; a lean oil outlet 1 is arranged on one side of the bottom of the storage tank section of the debenzene tower, which is connected to the lean oil inlet of the lean-rich oil heat exchanger through a lean oil pump; a lean oil outlet 2 is arranged on the other side of the bottom of the storage tank section, which is simultaneously connected to the first heating section and the second heating section of the tubular furnace through a lean oil circulation pump, and the hot lean oil outlet of the first heating section is connected to the hot lean oil inlet of the regeneration section and the hot lean oil distributor of the storage tank section through a hot lean oil pipeline; the hot lean oil outlet of the second heating section is connected to the heater inlet of the regeneration section, and the heater outlet is connected to the hot lean oil pipeline drawn from the first heating section.

[0021] A naphthalene oil production outlet is provided on one side of the upper part of the distillation section, and is connected to the residue tank through a naphthalene oil production pipeline;

[0022] The crude benzene vapor outlet at the top of the debenzene tower is connected to the crude benzene vapor inlet at the top of the crude benzene condensation, cooling and separation integrated device; the crude benzene collecting section of the crude benzene condensation, cooling and separation integrated device is provided with a crude benzene outlet connected to the crude benzene return pipeline and the crude benzene product delivery pipeline, and the crude benzene return pipeline is connected to the crude benzene inlet of the reflux crude benzene distributor; the non-condensable steam outlet at the top of the oil-gas-water separation section of the crude benzene condensation, cooling and separation integrated device is connected to the benzene washing unit through a vacuum pump, and the water collecting section is provided with a separation water outlet connected to the coal gas final cooling unit through a separation water pump.

[0023] The separation tank of the crude benzene condensation, cooling and separation integrated device is a horizontal tank, and partition plate one, partition plate two and partition plate three are arranged in the separation tank along the longitudinal interval, wherein the top surface of partition plate two is higher than the top surface of partition plate one, the top surface of partition plate one is higher than the top surface of partition plate three, and the bottom surface of partition plate two is spaced a distance from the bottom surface of the separation tank; the space between partition plate one and partition plate two is an oil-gas-water separation section, the internal space of the separation tank outside partition plate one is a crude benzene collection section, and the internal space of the separation tank outside partition plate three is a water collection section.

[0024] The residue tank is a horizontal tank, an inner partition is arranged in the residue tank, a naphthalene oil inlet and a naphthalene oil outlet are arranged on both sides of the inner partition at the top of the residue tank, the naphthalene oil inlet is connected to the naphthalene oil extraction pipeline, a naphthalene oil inlet pipe is arranged at the naphthalene oil inlet, and the naphthalene oil inlet pipe extends vertically downward to the bottom of the residue tank; the top surface of the inner partition is higher than the bottom opening height of the naphthalene oil inlet pipe; the naphthalene oil outlet of the residue tank is connected to the return naphthalene oil inlet at the top of the debenzene tower through a naphthalene oil return pipeline; a naphthalene oil delivery port is arranged at the lower part of the residue tank near the naphthalene oil outlet and connected to the inlet of a residue pump; a wash oil residue outlet is arranged at the bottom of the regeneration section of the debenzene tower and connected to the inlet of the residue pump, and the outlet of the residue pump is connected to the tar storage tank of the oil depot unit.

[0025] The lean oil outlet of the lean-rich oil heat exchanger is connected to the benzene washing unit through a lean oil pipeline, and a lean oil cooler and a lean oil deep cooler are arranged on the lean oil pipeline in sequence.

[0026] The top of the tubular furnace is provided with a flue gas outlet, and the bottom is provided with a burner. The burner is provided with a clean coal gas inlet and a combustion-supporting gas inlet. The combustion-supporting gas inlet is connected to the outlet of the air fan through a combustion-supporting gas pipeline. The flue gas inlet of the tubular furnace is connected to the flue gas inlet of the desulfurization and denitrification device through a flue gas pipeline one, and is connected to the inlet of the air fan through a flue gas pipeline two.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) Good environmental protection effect: Compared with the negative pressure crude benzene distillation process using the lean oil at the bottom of the distillation tower to heat in a tubular furnace as a heat source, the process of the present invention generates less tubular furnace waste gas, and all of it is sent to the desulfurization and denitrification device for treatment, without waste gas emission; compared with the negative pressure crude benzene distillation process using superheated steam as a direct heat source, the present invention does not generate additional crude benzene separation water, thereby reducing the amount of wastewater discharged.

[0029] 2) Low construction cost: The present invention integrates the crude benzene condensation cooler, gas-liquid separator, non-condensable steam cooler, oil-water separator and other equipment in the conventional crude benzene distillation system into one, that is, a crude benzene condensation, cooling and separation integrated device. In one device, the crude benzene steam condensation cooling, gas-liquid separation, oil-water separation, crude benzene reflux buffer, non-condensable steam condensation cooling and other functions can be realized. The device has a compact structure and a small size, and the equipment and land investment are significantly reduced;

[0030] In the previous design, the gas-liquid separator and the oil-water separator are two independent devices. In order to maintain the vacuum degree of the gas-liquid separator, the gas-liquid separator and the oil-water separator need to be designed at different elevations and maintain a certain elevation difference. When adopting this design, an installation frame must be set to place the two devices. The present invention integrates the two. The integrated crude benzene condensation, cooling and separation integrated device can be directly placed on the ground, eliminating the installation frame, and significantly reducing the primary investment in civil engineering.

[0031] The rectifying section and the stripping section of the debenzene tower of the present invention both use fillers instead of tower plates as mass transfer surfaces, which significantly reduces the height of the debenzene tower and saves the initial investment in equipment; the rectifying section is provided with a side line extraction device, and the naphthalene component in the circulating oil can be extracted without providing a liquid cut-off plate and a redistribution device.

[0032] 3) Low operating cost: The present invention does not use steam as the heat source for heating the debenzene tower, but uses the self-produced coal gas of the coking plant as the heat source, so the operating cost is low;

[0033] The tubular furnace of the present invention uses the reaction heat of combustion of coal gas and air as a heat source. Part of the exhaust gas after combustion is sent to a desulfurization and denitrification device for purification, and part is returned to the front of the air blower, which effectively reduces the amount of exhaust gas discharged and reduces the coal gas consumption; at the same time, the wall temperature of the furnace tube is reduced, the deterioration rate of the washing oil is slowed down, and the operating cost is low.

[0034] 4) The debenzenization effect of rich oil is good, and the naphthalene content of lean oil is low: In order to reduce the resistance of the debenzenization tower, the distillation section and the stripping section of the debenzenization tower of the present invention both use fillers as mass transfer surfaces instead of tower plates, which greatly reduces the resistance of the debenzenization tower and significantly increases the debenzenization efficiency of rich oil; the distillation section of the debenzenization tower uses fillers as the mass transfer surface, and a side line extraction device is provided, so that the naphthalene component in the circulating oil can be extracted without the need to set a liquid cut-off plate and a redistribution device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a schematic structural diagram of a negative pressure crude benzene distillation system using a tubular furnace for heating.

[0036] In the figure: 1. Debenzene tower 2. Rough pump condensation cooling separation integrated device 3. Tubular furnace 4. Residue tank 5. Benzene pump 6. Lean oil circulation pump 7. Lean oil pump 8. Residue pump 9. Separation water pump 10. Vacuum pump 11. Air fan 12. Lean oil deep cooler 13. Lean oil cooler 14. Lean and rich oil heat exchanger DETAILED DESCRIPTION

[0037] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0038] like Figure 1 As shown, the negative pressure crude benzene distillation process using a tubular furnace for heating according to the present invention comprises the following steps:

[0039] 1) The debenzene tower 1 is provided with a rectifying section, a stripping section, a storage tank section and a regeneration section from top to bottom; wherein the rectifying section and the stripping section are both provided with fillers; a heater is provided in the regeneration section; the rich oil sent from the benzene washing unit is heat exchanged with the hot lean oil discharged from the bottom of the debenzene tower 1 by the lean-rich oil heat exchanger 14, and then enters the stripping section of the debenzene tower 1 for distillation; a part of the hot lean oil at the bottom of the debenzene tower 1 is pumped out by the lean oil pump 7, and is cooled in three stages by the lean-rich oil heat exchanger 14, the lean oil cooler 13 and the lean oil deep freezer 12 in sequence, and then sent to the benzene washing unit;

[0040] 2) Another part of the hot lean oil at the bottom of the debenzene tower 1 is pumped out by the lean oil circulation pump 6 and sent to the tubular furnace 3 for heating in two parts; most of the lean oil is heated and sent to the storage tank section of the debenzene tower 1 for flash evaporation as a heat source for distillation; a small part of the lean oil is heated and sent to the heater in the regeneration section at the bottom of the debenzene tower 1 as a heat source for washing oil regeneration;

[0041] 3) The crude benzene vapor extracted from the top of the debenzene tower 1 enters the crude benzene condensation, cooling and separation integrated device 2, and enters the lower separation tank after heat exchange with circulating water and low-temperature water in sequence; the separation tank is provided with a crude benzene collection section, an oil-gas-water separation section and a water collection section; the crude benzene after heat exchange and condensation directly enters the oil-gas-water separation section, and the crude benzene, non-condensable gas and water are separated by standing, and the separated non-condensable gas is further heat exchanged with low-temperature water and deep cooled, and then pumped out by the vacuum pump 10 and sent to the benzene washing unit; the separated crude benzene overflows into the crude benzene collection section, and a part is pumped out by the benzene pump 5 and sent to the top of the debenzene tower 1 as reflux; the other part is sent to the crude benzene storage tank of the oil depot unit as a crude benzene product; the separated water overflows to the water collection section, and is pumped out by the separation water pump 9 and sent to the coal gas final cooling unit;

[0042] 4) draw naphthalene oil fraction at the rectifying section side line of debenzene tower 1, the naphthalene oil fraction drawn enters residue tank 4, is regularly delivered to the tar storage tank of oil depot unit by residue pump 8;

[0043] 5) A small amount of hot lean oil is drawn from the circulating heating oil and sent to the regeneration section at the bottom of the debenzene tower 1, where it is heated by a heater, and the evaporated oil-gas mixed steam is also sent to the bottom of the debenzene tower 1 as a heat source;

[0044] 6) The tubular furnace 3 uses the reaction heat of combustion of coal gas and air as a heat source; part of the exhaust gas after combustion is sent to the desulfurization and denitrification device for purification, and the other part is returned to the air duct upstream of the air blower 11, mixed with the newly entered air, and then sent to the tubular furnace 3 as a combustion-supporting gas.

[0045] The negative pressure crude benzene distillation system using tubular furnace heating described in the present invention comprises a debenzene tower 1, a tubular furnace 3 and a crude benzene condensation, cooling and separation integrated device 2; the debenzene tower 1 is provided with a distillation section, a stripping section, a storage tank section and a regeneration section in sequence from top to bottom; wherein the distillation section and the stripping section are both provided with fillers; a reflux crude benzene distributor is provided at the top of the distillation section, an oil-rich distributor is provided at the top of the stripping section, and a hot lean oil distributor is provided at the top of the storage tank section; a heater is provided in the regeneration section; the storage tank section and the regeneration section are connected by a circulating lean oil pipeline; the crude benzene condensation, cooling and separation integrated device 2 comprises a heat exchange tower and a separation tank; a circulating water heat exchanger is provided at the upper part of the heat exchange tower, and a low-temperature water heat exchanger is provided at the lower part; a crude benzene collecting section, an oil-gas-water separation section and a water collecting section are provided in the separation tank; the bottom of the heat exchange tower is connected to the top of the oil-gas-water separation section; a low-temperature water-non-condensable gas heat exchanger is provided in the separation tank above the oil-gas-water separation section; a heating section 1 and a heating section 2 are provided in the tubular furnace;

[0046] The rich oil inlet of the rich oil distributor is connected to the rich oil outlet of the lean-rich oil heat exchanger 14, and the rich oil inlet of the lean-rich oil heat exchanger 14 is connected to the rich oil outlet pipeline of the benzene washing unit; a lean oil outlet 1 is provided on one side of the bottom of the storage tank section of the debenzene tower 1, which is connected to the lean oil inlet of the lean-rich oil heat exchanger 14 through a lean oil pump 7; a lean oil outlet 2 is provided on the other side of the bottom of the storage tank section, which is simultaneously connected to the first heating section and the second heating section of the tubular furnace 3 through a lean oil circulation pump 6, and the hot lean oil outlet of the first heating section is connected to the hot lean oil inlet of the regeneration section and the hot lean oil distributor of the storage tank section through a hot lean oil pipeline; the hot lean oil outlet of the second heating section is connected to the heater inlet of the regeneration section, and the heater outlet is connected to the hot lean oil pipeline drawn from the first heating section.

[0047] A naphthalene oil extraction port is provided on one side of the upper portion of the rectifying section, and is connected to a residue tank 4 through a naphthalene oil extraction pipeline;

[0048] The crude benzene vapor outlet at the top of the debenzene tower 1 is connected to the crude benzene vapor inlet at the top of the crude benzene condensation, cooling and separation integrated device 2; the crude benzene collecting section of the crude benzene condensation, cooling and separation integrated device 2 is provided with a crude benzene outlet connected to the crude benzene return pipeline and the crude benzene product delivery pipeline, and the crude benzene return pipeline is connected to the crude benzene inlet of the reflux crude benzene distributor; the non-condensable steam outlet at the top of the oil-gas-water separation section of the crude benzene condensation, cooling and separation integrated device 2 is connected to the benzene washing unit through a vacuum pump 10, and the water collecting section is provided with a separation water outlet connected to the coal gas final cooling unit through a separation water pump 9.

[0049] The separation tank of the crude benzene condensation, cooling and separation integrated device 2 is a horizontal tank, and partition plate 1, partition plate 2 and partition plate 3 are arranged in the separation tank along the longitudinal interval, wherein the top surface of partition plate 2 is higher than the top surface of partition plate 1, the top surface of partition plate 1 is higher than the top surface of partition plate 3, and the bottom surface of partition plate 2 is spaced a distance from the bottom surface of the separation tank; the space between partition plate 1 and partition plate 2 is the oil-gas-water separation section, the internal space of the separation tank outside partition plate 1 is the crude benzene collection section, and the internal space of the separation tank outside partition plate 3 is the water collection section.

[0050] The residue tank 4 is a horizontal tank, an inner partition is arranged in the residue tank 4, a naphthalene oil inlet and a naphthalene oil outlet are arranged on both sides of the inner partition at the top of the residue tank 4, the naphthalene oil inlet is connected to the naphthalene oil production pipeline, a naphthalene oil inlet pipe is arranged at the naphthalene oil inlet, and the naphthalene oil inlet pipe extends vertically downward to the bottom of the residue tank 4; the top surface of the inner partition is higher than the bottom opening height of the naphthalene oil inlet pipe; the naphthalene oil outlet of the residue tank 4 is connected to the return naphthalene oil inlet at the top of the debenzene tower 1 through a naphthalene oil return pipeline; a naphthalene oil delivery port is arranged at the lower part of the residue tank 4 near the naphthalene oil outlet, which is connected to the inlet of a residue pump 8; a wash oil residue outlet is arranged at the bottom of the regeneration section of the debenzene tower 1, which is connected to the inlet of the residue pump 8, and the outlet of the residue pump 8 is connected to the tar storage tank of the oil depot unit.

[0051] The lean oil outlet of the lean-rich oil heat exchanger 14 is connected to the benzene washing unit through a lean oil pipeline, and a lean oil cooler 13 and a lean oil deep cooler 12 are sequentially arranged on the lean oil pipeline.

[0052] The top of the tubular furnace 3 is provided with a flue gas outlet, and the bottom is provided with a burner. The burner is provided with a clean coal gas inlet and a combustion-supporting gas inlet. The combustion-supporting gas inlet is connected to the outlet of the air fan 11 through a combustion-supporting gas pipeline; the flue gas inlet of the tubular furnace 3 is connected to the flue gas inlet of the desulfurization and denitrification device through a flue gas pipeline 1, and is connected to the inlet of the air fan 11 through a flue gas pipeline 2.

[0053] The negative pressure crude benzene distillation system using tubular furnace heating of the present invention utilizes a tubular furnace 3 to heat two circulating wash oils, one of which is used as a heat source for crude benzene distillation and the other as a heat source for wash oil regeneration. A vacuum pump (set) is used to maintain the vacuum degree of the crude benzene distillation system and the wash oil regeneration system.

[0054] Part of the flue gas generated by the tubular furnace 3 is sent to the desulfurization and denitrification device, and part is returned to the air blower 11, which can effectively reduce the amount of exhaust gas discharged, reduce gas consumption, reduce the furnace tube wall temperature, and slow down the deterioration rate of oil washing.

[0055] The crude benzene condensation, cooling and separation integrated device 2 is used to realize multiple functions such as crude benzene condensation and cooling, oil-water separation, gas-liquid separation, crude benzene reflux buffering, and non-condensing steam deep cooling in one device. The crude benzene condensation, cooling and separation integrated device 2 can be placed directly on the ground without the need for an additional installation frame.

[0056] In order to reduce the resistance of the debenzene tower 1, the distillation section and the stripping section in the debenzene tower 1 both use fillers as mass transfer surfaces. Compared with the method of using tower plates, the resistance of the debenzene tower is greatly reduced, the oil-rich debenzene efficiency is significantly increased, and the height of the debenzene tower is significantly reduced.

[0057] The debenzene tower 1 uses packing as a mass transfer surface in the distillation section and is provided with a side line extraction device. The naphthalene component in the circulating oil can be extracted without setting a liquid cut-off plate and a redistribution device, thereby reducing the naphthalene content in the lean oil and further reducing the naphthalene content in the coal gas after benzene washing.

[0058] In order to ensure the quality of the circulating wash oil, a small amount of hot lean oil is drawn out from the circulating hot lean oil and sent to the regeneration section of the debenzene tower 1. The hot lean oil is used as a heat source for heating through a heater, and the evaporated oil-gas mixed steam enters the bottom of the debenzene tower 1 as a distillation heat source.

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A negative pressure crude benzene distillation process using tubular furnace heating, characterized in that: The process includes the following: 1) The debenzene tower is provided with a rectifying section, a stripping section, a storage tank section and a regeneration section from top to bottom; the rectifying section and the stripping section are both provided with fillers; the regeneration section is provided with a heater; the rich oil sent from the benzene washing unit is heat exchanged with the hot lean oil discharged from the bottom of the debenzene tower through the lean-rich oil heat exchanger, and then enters the stripping section of the debenzene tower for distillation; a part of the hot lean oil at the bottom of the debenzene tower is pumped out by the lean oil pump, and is cooled in three stages in sequence through the lean-rich oil heat exchanger, the lean oil cooler and the lean oil deep freezer, and then sent to the benzene washing unit; 2) Another part of the hot lean oil at the bottom of the debenzene tower is pumped out by the lean oil circulation pump and sent to the tubular furnace for heating in two parts; most of the lean oil is heated and sent to the storage tank section of the debenzene tower for flash evaporation as a heat source for distillation; a small part of the lean oil is heated and sent to the heater in the regeneration section at the bottom of the debenzene tower as a heat source for washing oil regeneration; 3) The crude benzene vapor extracted from the top of the debenzene tower enters the crude benzene condensation, cooling and separation integrated device, and then enters the separation tank at the bottom after heat exchange with circulating water and low-temperature water in turn; the separation tank is provided with a crude benzene collection section, an oil-gas-water separation section and a water collection section; the crude benzene after heat exchange and condensation directly enters the oil-gas-water separation section, and the crude benzene, non-condensable gas and water are separated by standing, and the separated non-condensable gas is further heat exchanged with low-temperature water and deep cooled, and then pumped out by a vacuum pump and sent to the benzene washing unit; the separated crude benzene overflows into the crude benzene collection section, and a part is pumped out by a benzene pump and sent to the top of the debenzene tower as reflux; the other part is sent to the crude benzene storage tank of the oil depot unit as a crude benzene product; the separated water overflows to the water collection section, and is pumped out by a separation water pump and sent to the coal gas final cooling unit; 4) draw the naphthalene oil fraction at the rectifying section side line of the debenzene tower, the naphthalene oil fraction drawn enters the residue tank, and is regularly delivered to the tar storage tank of the oil depot unit by the residue pump; 5) A small amount of hot lean oil is drawn from the circulating heating oil and sent to the regeneration section at the bottom of the debenzene tower, where it is heated by the heater, and the evaporated oil-gas mixed steam is also sent to the bottom of the debenzene tower as a heat source; 6) The tubular furnace uses the reaction heat of combustion of coal gas and air as the heat source; part of the exhaust gas after combustion is sent to the desulfurization and denitrification device for purification, and the other part is returned to the air duct upstream of the air blower, mixed with the newly entered air, and then sent to the tubular furnace as a combustion-supporting gas.

2. A negative pressure crude benzene distillation system using tubular furnace heating for realizing the negative pressure crude benzene distillation process using tubular furnace heating as claimed in claim 1, characterized in that: It comprises a debenzene tower, a tubular furnace and a crude benzene condensation, cooling and separation integrated device; the debenzene tower is provided with a rectification section, a stripping section, a storage tank section and a regeneration section in sequence from top to bottom; wherein the rectification section and the stripping section are both provided with fillers; a reflux crude benzene distributor is provided at the top of the rectification section, an oil-rich distributor is provided at the top of the stripping section, and a hot lean oil distributor is provided at the top of the storage tank section; a heater is provided in the regeneration section; the storage tank section and the regeneration section are connected by a circulating lean oil pipeline; the crude benzene condensation, cooling and separation integrated device comprises a heat exchange tower and a separation tank; a circulating water heat exchanger is provided at the upper part of the heat exchange tower, and a low-temperature water heat exchanger is provided at the lower part; a crude benzene collecting section, an oil-gas-water separation section and a water collecting section are provided in the separation tank; the bottom of the heat exchange tower is connected to the top of the oil-gas-water separation section; a low-temperature water-non-condensable gas heat exchanger is provided in the separation tank above the oil-gas-water separation section; a heating section 1 and a heating section 2 are provided in the tubular furnace; The rich oil inlet of the rich oil distributor is connected to the rich oil outlet of the lean-rich oil heat exchanger, and the rich oil inlet of the lean-rich oil heat exchanger is connected to the rich oil outlet pipeline of the benzene washing unit; a lean oil outlet 1 is provided on one side of the bottom of the storage tank section of the debenzene tower, which is connected to the lean oil inlet of the lean-rich oil heat exchanger through a lean oil pump; a lean oil outlet 2 is provided on the other side of the bottom of the storage tank section, which is simultaneously connected to the first heating section and the second heating section of the tubular furnace through a lean oil circulation pump, and the hot lean oil outlet of the first heating section is connected to the hot lean oil inlet of the regeneration section and the hot lean oil distributor of the storage tank section through a hot lean oil pipeline; the hot lean oil outlet of the second heating section is connected to the heater inlet of the regeneration section, and the heater outlet is connected to the hot lean oil pipeline drawn from the first heating section; A naphthalene oil production outlet is provided on one side of the upper part of the distillation section, and is connected to the residue tank through a naphthalene oil production pipeline; The crude benzene vapor outlet at the top of the debenzene tower is connected to the crude benzene vapor inlet at the top of the crude benzene condensation, cooling and separation integrated device; the crude benzene collecting section of the crude benzene condensation, cooling and separation integrated device is provided with a crude benzene outlet connected to the crude benzene return pipeline and the crude benzene product delivery pipeline, and the crude benzene return pipeline is connected to the crude benzene inlet of the reflux crude benzene distributor; the non-condensable steam outlet at the top of the oil-gas-water separation section of the crude benzene condensation, cooling and separation integrated device is connected to the benzene washing unit through a vacuum pump, and the water collecting section is provided with a separation water outlet connected to the coal gas final cooling unit through a separation water pump.

3. The negative pressure crude benzene distillation system using tubular furnace heating according to claim 2, characterized in that: The separation tank of the crude benzene condensation, cooling and separation integrated device is a horizontal tank, and partition plate one, partition plate two and partition plate three are arranged in the separation tank along the longitudinal interval, wherein the top surface of partition plate two is higher than the top surface of partition plate one, the top surface of partition plate one is higher than the top surface of partition plate three, and the bottom surface of partition plate two is spaced a distance from the bottom surface of the separation tank; the space between partition plate one and partition plate two is an oil-gas-water separation section, the internal space of the separation tank outside partition plate one is a crude benzene collection section, and the internal space of the separation tank outside partition plate three is a water collection section.

4. The negative pressure crude benzene distillation system using tubular furnace heating according to claim 2, characterized in that: The residue tank is a horizontal tank, an inner partition is arranged in the residue tank, a naphthalene oil inlet and a naphthalene oil outlet are arranged on both sides of the inner partition at the top of the residue tank, the naphthalene oil inlet is connected to the naphthalene oil extraction pipeline, a naphthalene oil inlet pipe is arranged at the naphthalene oil inlet, and the naphthalene oil inlet pipe extends vertically downward to the bottom of the residue tank; the top surface of the inner partition is higher than the bottom opening height of the naphthalene oil inlet pipe; the naphthalene oil outlet of the residue tank is connected to the return naphthalene oil inlet at the top of the debenzene tower through a naphthalene oil return pipeline; a naphthalene oil delivery port is arranged at the lower part of the residue tank near the naphthalene oil outlet and connected to the inlet of a residue pump; a wash oil residue outlet is arranged at the bottom of the regeneration section of the debenzene tower and connected to the inlet of the residue pump, and the outlet of the residue pump is connected to the tar storage tank of the oil depot unit.

5. The negative pressure crude benzene distillation system using tubular furnace heating according to claim 2, characterized in that: The lean oil outlet of the lean-rich oil heat exchanger is connected to the benzene washing unit through a lean oil pipeline, and a lean oil cooler and a lean oil deep cooler are arranged on the lean oil pipeline in sequence.

6. The negative pressure crude benzene distillation system using tubular furnace heating according to claim 2, characterized in that: The top of the tubular furnace is provided with a flue gas outlet, and the bottom is provided with a burner. The burner is provided with a clean coal gas inlet and a combustion-supporting gas inlet. The combustion-supporting gas inlet is connected to the outlet of the air fan through a combustion-supporting gas pipeline. The flue gas inlet of the tubular furnace is connected to the flue gas inlet of the desulfurization and denitrification device through a flue gas pipeline one, and is connected to the inlet of the air fan through a flue gas pipeline two.

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