Biodiesel distillation vacuum tail gas treatment device

Abstract

The invention discloses a biodiesel distillation vacuum tail gas treatment device; the inlet of the tail gas vacuum unit is connected to the vacuum outlet of the distillation tower, the outlet is connected to the working liquid tank of the tail gas vacuum unit, the tank outlet is connected to a horizontal condenser, the horizontal condenser is provided with a tail gas outlet, a sewage outlet and a cooling water inlet and outlet, the tail gas outlet is connected to the inlet of a methanol receiving tank, the outlet of the receiving tank is connected to a methanol separator, a liquid methanol outlet is provided at the lower part of the receiving tank and connected to a methanol separation outlet pump; a tail gas outlet is provided at the top of the methanol separator, a heat mixing pipe steam inlet pipe is provided on it, an oxygen content control system is provided next to the tail gas outlet, the tail gas outlet is connected to the heat mixing pipe and the vacuum tail gas pipe in sequence, a pipeline separator, a pressure control system, a gravel flame arrester, a fire extinguishing steam pipe, a front temperature control system, a safety water seal, a stainless steel flame arrester and a rear temperature control system are sequentially installed on the vacuum tail gas pipe and then connected to a combustion furnace. The invention is safe to operate, environmentally friendly, efficient and has low production cost.

Description

Technical Field

[0001] The invention relates to the technical field of biodiesel production devices, and in particular to a vacuum tail gas treatment device when using waste oil and methanol as raw materials to carry out distillation of biodiesel production. Background Art

[0002] Domestic biodiesel production enterprises mainly use waste oil as raw material. Due to the common characteristics of waste oil with many impurities and the coexistence of free fatty acids and oil, it needs to be purified and impurities removed, and then the crude fatty acid methyl ester is produced through two-step chemical methods of esterification and transesterification. The crude methyl ester then enters the falling film flash evaporation to remove water and low-boiling substances such as methanol, and then the crude methyl ester is heated to 250℃ with heat transfer oil and enters the biodiesel distillation tower. Under a negative pressure of -0.05MPa, vacuum tail gas is extracted from the top of the distillation tower, and qualified products are obtained from different distillation towers according to different boiling points. The components of the vacuum tail gas extracted from the top of the distillation tower include: ① During the treatment and storage process of waste oil, due to a series of complex changes such as rancidity and oxidation, harmful volatile substances such as aldehydes, ketones, anthracenes, quinones, and small molecular acids will be produced; ② Acidic gases produced by the raw material waste animal and plant oils; ③ Waste oil contains sulfide and other tail gas with strong odor and strong corrosiveness; ④ Methanol tail gas; ⑤ Low boiling substances, etc. The direct discharge of the above vacuum tail gas will not only affect the production environment and safety, but also cause methanol waste. Summary of the invention

[0003] The purpose of the present invention is to provide a biodiesel distillation vacuum tail gas treatment device which is safe to operate, environmentally friendly, efficient and has low production cost, so as to achieve the goal of not causing environmental pollution when treating vacuum tail gas during the biodiesel distillation process, and to monitor in real time whether the production system and the vacuum unit have leaks, thereby ensuring the safe operation of the production and vacuum tail gas device and maximizing the recovery of methanol.

[0004] To achieve the above purpose, the biodiesel distillation vacuum tail gas treatment device of the present invention comprises a tail gas vacuum unit 4, a tail gas vacuum unit working liquid tank 5, a horizontal condenser 6, a methanol receiving tank 7, a methanol separation receiving tank outlet pump 8, an oxygen content control system 9, a methanol separator 10, a heat mixing pipe 11, a pipeline separator 12, a pressure control system 13, a gravel flame arrester 14, a fire extinguishing steam pipe 15, a front temperature control system 16, a safety water seal 17, a stainless steel flame arrester 18, a rear temperature control system 19, a combustion furnace 20, a vacuum tail gas pipe 21, and a coal furnace 22; the inlet of the tail gas vacuum unit 4 is connected to the distillation tower vacuum outlet b, and the outlet is connected to the tail gas vacuum unit working liquid tank 5, and the outlet of the tail gas vacuum unit working liquid tank 5 is connected to the horizontal condenser tail gas inlet j located at the upper left part of the horizontal condenser 6; the horizontal condenser 6 adopts a double-return horizontal condenser, and the lower left part is provided with a horizontal condenser tail gas outlet h, the lower right part is provided with a sewage outlet g, the left end is provided with a cooling water inlet i, and the right end is provided with a cooling water inlet i. There is a cooling water outlet k; the horizontal condenser tail gas outlet h is connected to the upper inlet of the methanol receiving tank 7, the upper outlet of the methanol receiving tank 7 is connected to the methanol separator tail gas inlet l located in the middle and upper part of the side of the methanol separator 10, and the lower part of the methanol receiving tank 7 is provided with a liquid methanol outlet and connected to the methanol separation receiving tank outlet pump 8; the top center of the methanol separator 10 is provided with a methanol separator tail gas outlet m, the methanol separator tail gas outlet pipe is provided with a heat mixing pipe steam inlet pipe n, and an oxygen content control system 9 is provided next to the top center of the methanol separator 10; the methanol separator tail gas outlet m is connected to the heat mixing pipe 11 and the vacuum tail gas pipe 21 in sequence, and the pipeline separator 12, the pressure control system 13, the gravel flame arrester 14, the fire extinguishing steam pipe 15, the front temperature control system 16, the safety water seal 17, the stainless steel flame arrester 18 and the rear temperature control system 19 are installed on the vacuum tail gas pipe 21 in sequence and then connected to the combustion furnace 20, and the end of the vacuum tail gas pipe 21 is bent downward and the diameter is reduced to facilitate concentrated combustion of the tail gas.

[0005] The use of a double-return horizontal condenser can greatly extend the vacuum tail gas separation time, facilitate the first condensation separation of methanol and low-boiling substances, greatly reduce the content of methanol and low-boiling substance condensate in the tail gas and make it recyclable; a methanol separator tail gas outlet is arranged on the top of the methanol separator, and a hot pipe steam inlet pipe is provided on the methanol separator tail gas outlet pipe to achieve the second separation of methanol and low-boiling substance condensate, so that the content of methanol and low-boiling substance condensate in the tail gas is further reduced; the pipeline separator installed at the bottom of the vacuum tail gas pipe is used to achieve the third separation of methanol and low-boiling substances in the tail gas in the pipeline condensate. At this time, the content of condensed methanol and low-boiling substance condensate in the tail gas is almost zero, and the tail gas furnace can avoid flashback accidents due to the absence of condensate.

[0006] The working principle of the oxygen content control system is that when the vacuum tail gas in the methanol separator tank is higher than the set upper limit, the oxygen controller sensor sends an alarm signal to the PLC to monitor the oxygen content of the production system and the vacuum unit in real time; oxygen content is an important safety indicator for distillation production, and the normal oxygen content is 0; if there is a leak in the normal production system and the vacuum unit, the oxygen content exceeds the standard by more than 0.5% and less than 1%, the leakage point should be dealt with in time, and if it is greater than 1%, the system should be shut down in time, otherwise it will be detrimental to safe production.

[0007] The first flame arrester adopts a stainless steel flame arrester, and the second adopts a gravel flame arrester. A front temperature control system is installed in front of the gravel flame arrester. The working principle of the front temperature control system and the rear temperature control system is that when the exhaust gas temperature of the vacuum exhaust pipe is higher than the set upper limit value, the temperature sensor sends an alarm signal to the program control system PLC. If the temperature rises abnormally, it means that there is a backfire phenomenon, and it is handled in time to open the fire extinguishing steam pipe for steam extinguishing; a pressure control system is installed after the gravel flame arrester. The working principle of the pressure control system is that when the exhaust gas pressure of the vacuum exhaust pipe is higher than the set upper limit value, the pressure transmitter sends an alarm signal to the program control system PLC. If the pressure rises, it means that the flame arrester is blocked, and the flame arrester is handled in time.

[0008] The upper control computers of the above-mentioned oxygen content control system, temperature control system and pressure control system are equipped with Tianhong Industrial Configuration Software V1.0. The function of this software system is to display, record and control the data of each process point. The software developer is Longyan Tianhong Computer Technology Co., Ltd., and it was launched in May 2018, which belongs to the prior art; the above-mentioned program control system PLC was developed by Longyan Tianhong Computer Technology Co., Ltd., the PLC brand is Siemens, the CPU and acquisition control module of the PLC system are Siemens S7-1200 series general products, and the PLC software programming is written by Longyan Tianhong Computer Technology Co., Ltd. according to requirements. All software and hardware with computer programs can be purchased on the market, which belongs to the prior art.

[0009] The biodiesel distillation vacuum tail gas treatment device of the present invention has the following technical characteristics and beneficial effects:

[0010] 1. The use of horizontal condensers, methanol separators and pipeline separators can well separate methanol and condensate from low-boiling substances, avoiding accidents caused by liquid flashback in the distillation vacuum tail gas treatment device;

[0011] 2. Adding an oxygen controller is very beneficial to monitoring distillation safety production, avoiding accidents caused by excessive oxygen content in the tail gas of the distillation vacuum tail gas treatment device;

[0012] 3. Adding a second flame arrester and multi-point temperature measurement can monitor the safe operation status and safety reliability of the distillation vacuum tail gas treatment device in real time.

[0013] 4. It has achieved the goal of not causing environmental pollution when treating vacuum exhaust gas during the biodiesel distillation process, but also being able to monitor in real time whether there are leaks in the production system and vacuum unit, ensuring the safe operation of production and vacuum exhaust gas equipment, and maximizing the recovery of methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram of a biodiesel distillation vacuum tail gas treatment device according to the present invention.

[0015] Figure 2 yes Figure 1 Schematic diagram of the enlarged structure of the middle distillation tower.

[0016] Figure 3 yes Figure 1 Schematic diagram of the enlarged structure of a medium horizontal condenser.

[0017] Figure 4 yes Figure 1 Schematic diagram of the enlarged structure of the methanol separator.

[0018] Figure 5 yes Figure 1 Schematic diagram of the enlarged structure of the middle pipeline flame arrester, temperature control system, and pressure control system.

[0019] Figure numerals: distillation tower 1, reboiler 2, distillation tower circulation pump 3, tail gas vacuum unit 4, tail gas vacuum unit working liquid tank 5, horizontal condenser 6, methanol receiving tank 7, methanol separation receiving tank outlet pump 8, oxygen content control system 9, methanol separator 10, heat mixing pipe 11, pipeline separator 12, pressure control system 13, gravel flame arrester 14, fire extinguishing steam pipe 15, front temperature control system 16, safety water seal 17, stainless steel flame arrester 18, rear temperature control system 19, combustion furnace 20, vacuum tail gas pipe 21, Coal furnace 22, crude methyl ester feed inlet a of distillation tower, vacuum outlet b of distillation tower, biodiesel outlet c of distillation tower, vapor phase inlet d of distillation tower reboiler, methyl ester feed outlet e of distillation tower, circulation outlet f of distillation tower reboiler, sewage outlet g of horizontal condenser, tail gas outlet h of horizontal condenser, cooling water inlet i, tail gas inlet j of horizontal condenser, cooling water outlet k, tail gas inlet l of methanol separator, tail gas outlet m of methanol separator, steam inlet pipe n of heat mixing pipe, T-temperature, O-oxygen content, P-pressure, I-display, A-alarm. DETAILED DESCRIPTION

[0020] The biodiesel distillation vacuum tail gas treatment device of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0021] Figure 1-Figure 5As shown, the biodiesel distillation vacuum tail gas treatment device of the present invention includes a tail gas vacuum unit 4, a tail gas vacuum unit working liquid tank 5, a horizontal condenser 6, a methanol receiving tank 7, a methanol separation receiving tank outlet pump 8, an oxygen content control system 9, a methanol separator 10, a heat mixing pipe 11, a pipeline separator 12, a pressure control system 13, a gravel flame arrester 14, a fire extinguishing steam pipe 15, a front temperature control system 16, a safety water seal 17, a stainless steel flame arrester 18, a rear temperature control system 19, a combustion furnace 20, a vacuum tail gas pipe 21, and a coal furnace 22; the inlet of the tail gas vacuum unit 4 is connected to the vacuum outlet b of the distillation tower, and the outlet is connected to the tail gas vacuum unit working liquid tank 5, and the outlet of the tail gas vacuum unit working liquid tank 5 is connected to the upper left part of the horizontal condenser 6. The horizontal condenser tail gas inlet j; the horizontal condenser 6 adopts a double-return horizontal condenser, which is provided with a horizontal condenser tail gas outlet h at the lower left, a sewage outlet g at the lower right, a cooling water inlet i at the left end, and a cooling water outlet k at the right end; the horizontal condenser tail gas outlet h is connected to the upper inlet of the methanol receiving tank 7, and the upper outlet is connected to the methanol separator tail gas inlet l located in the middle and upper part of the side of the methanol separator 10, and the lower part of the methanol receiving tank 7 is provided with a liquid methanol outlet and connected to the methanol separation receiving tank outlet pump 8; the top center of the methanol separator 10 is provided with a methanol separator tail gas outlet m, and the methanol separator tail gas outlet pipe is provided with a heat mixing pipe steam inlet pipe n, and an oxygen content control system 9 is provided 0.3 meters away from the top center of the methanol separator 10. The pipeline separator 12 is installed at the bottom of the ￠133 vacuum tail gas outlet pipe 21, and is installed 1 meter before the gravel flame arrester 14. The methanol and low-boiling substances in the tail gas are separated for the third time in the condensate in the pipeline. The condensed methanol and low-boiling substances in the tail gas are basically free, ensuring that there is no condensate in the tail gas furnace to avoid flashback accidents; the vacuum tail gas pipe 21 is installed with a stainless steel flame arrester 18 and a gravel flame arrester 14. The distance between the two flame arresters is 8 meters. The first one adopts a stainless steel flame arrester 18. The distance between the stainless steel flame arrester 18 and the center of the combustion furnace 20 is 2.5 meters. The rear temperature control system 19 is installed in front of the stainless steel flame arrester 18. The end of the vacuum tail gas pipe 21 is bent downward and the diameter is changed from ￠133 to ￠76 pipe, which is convenient for concentrated combustion of exhaust gas; the second one adopts a gravel flame arrester, and a front temperature control system 16 is installed in front of the gravel flame arrester. The working principle of the front temperature control system 16 and the rear temperature control system 19 is that when the exhaust temperature of the vacuum exhaust pipe 21 is higher than the set upper limit value, the temperature sensor sends an alarm signal to the program control system PLC to prompt. If the temperature rises abnormally, it means that there is a flashback phenomenon, and it is handled in time to open the fire extinguishing steam pipe 15 for steam extinguishing; a pressure control system 13 is installed after the gravel flame arrester 14. The working principle of the pressure control system 13 is that when the exhaust pressure of the vacuum exhaust pipe 21 is higher than the set upper limit value, the pressure transmitter sends an alarm signal to the program control system PLC to prompt. If the pressure rises, it means that the flame arrester is blocked, and the flame arrester is handled in time.

[0022] The specific operation steps of the biodiesel distillation vacuum tail gas treatment device of the present invention when used are as follows:

[0023] Crude biodiesel enters from the crude methyl ester feed port a of the distillation tower in the middle of the distillation tower 1, and after the crude methyl ester is heated to a certain temperature by the reboiler 2 of the distillation tower 1, qualified products are obtained from different distillation tower biodiesel outlets c at the upper part of the distillation tower 1 under high temperature vacuum according to different boiling points; vacuum tail gas enters the tail gas vacuum unit 4 from the distillation tower vacuum outlet b at the top of the distillation tower 1, and passes through the tail gas vacuum unit working liquid tank 5 at a relatively low position. The liquid level in the tail gas vacuum unit working liquid tank 5 is controlled at a height of 1 / 3 to 1 / 2, and is maintained by artificial discharge when exceeding the height. From bottom to top, it enters the horizontal condenser 6 at a relatively high position, and the vacuum exhaust gas and condensate flow by gravity to the methanol receiving tank 7. After the vacuum exhaust gas is separated, it flows out from the upper part of the methanol receiving tank 7 and enters the methanol separator 10. After gas-liquid separation, the vacuum exhaust gas flows out from the methanol separator exhaust gas outlet m at the top of the methanol separator 10 and enters the vacuum exhaust gas pipe 21. The condensate of the vacuum exhaust gas in the vacuum exhaust gas pipe 21 will naturally sink into the pipeline separator 12 and be discharged through manual control. After the condensate is discharged, the vacuum exhaust gas passes through the gravel flame arrester 14 and the stainless steel flame arrester 18 and then burns in the combustion furnace 20.

[0024] When the vacuum tail gas is separated in the methanol receiving tank 7 and then flows out from the upper part of the methanol receiving tank 7 into the methanol separator 10, the oxygen content control system 9 starts to work, and the oxygen content is controlled to be less than 0.5%. The normal oxygen content value is 0%. When the oxygen content is greater than 0.5%, the valve in front of the vacuum tail gas pipe 21 entering the combustion furnace 20 is closed. Since the valve on the water inlet seal tail gas pipe is usually open, the vacuum tail gas is naturally discharged from the safety water seal 17. At this time, the coal furnace 22 can be removed and the distillation workshop is notified to shut down.

[0025] When the condensate of vacuum exhaust gas in the vacuum exhaust pipe 21 naturally sinks into the pipeline separator 12 and is discharged through manual control, the pressure control system 13 installed on the upper part of the vacuum exhaust pipe 21 starts to work, and the working pressure is controlled to be less than 0.03MPa. When the working pressure is greater than 0.03MPa, the vacuum exhaust gas is naturally discharged from the safety water seal 17; if the pressure rises due to the flame arrester being used for too long, the flame arrester needs to be stopped and cleaned.

[0026] After the condensate in the vacuum tail gas pipe 21 is discharged, when the vacuum tail gas enters the gravel flame arrester 14 and the stainless steel flame arrester 18 in turn and finally enters the combustion furnace 20 for combustion, the front temperature control system 16 and the rear temperature control system 19 on the upper part of the vacuum tail gas pipe 21 start to work, and the working temperature is controlled at less than 60°C. When the working temperature of the rear temperature control system 19 is greater than 60°C, the vacuum tail gas may flash back. At this time, the coal furnace 22 is removed, the fire extinguishing steam pipe 15 is opened to extinguish the fire, and the distillation workshop is notified to shut down. The purpose of adding the second gravel flame arrester 14 is that when the first stainless steel flame arrester 18 flashes back, the gravel flame arrester 14 can play a second protection role.

Claims

1. A biodiesel distillation vacuum tail gas treatment device, characterized in that: It includes an exhaust gas vacuum unit (4), an exhaust gas vacuum unit working liquid tank (5), a horizontal condenser (6), a methanol receiving tank (7), a methanol separation receiving tank outlet pump (8), an oxygen content control system (9), a methanol separator (10), a heat mixing pipe (11), a pipeline separator (12), a pressure control system (13), a gravel flame arrester (14), a fire extinguishing steam pipe (15), a front temperature control system (16), a safety water seal (17), a stainless steel flame arrester (18), a rear temperature control system (19), a combustion furnace (20), a vacuum A tail gas pipe (21) and a coal furnace (22); the inlet of the tail gas vacuum unit (4) is connected to the vacuum outlet (b) of the distillation tower, and the outlet is connected to the tail gas vacuum unit working liquid tank (5); the outlet of the tail gas vacuum unit working liquid tank (5) is connected to the horizontal condenser tail gas inlet (j) arranged at the upper left part of the horizontal condenser (6); the horizontal condenser (6) adopts a double-return horizontal condenser, and the lower left part is provided with a horizontal condenser tail gas outlet (h), the lower right part is provided with a sewage outlet (g), the left end is provided with a cooling water inlet (i), and the right end is provided with a cooling water outlet (k); The tail gas outlet (h) of the horizontal condenser is connected to the upper inlet of the methanol receiving tank (7), and the upper outlet of the methanol receiving tank (7) is connected to the tail gas inlet (l) of the methanol separator located in the middle and upper part of the side of the methanol separator (10). The lower part of the methanol receiving tank (7) is provided with a liquid methanol outlet and connected to the methanol separation receiving tank outlet pump (8); the top center of the methanol separator (10) is provided with a methanol separator tail gas outlet (m), the methanol separator tail gas outlet pipe is provided with a heat mixing pipe steam inlet pipe (n), and a An oxygen content control system (9); the tail gas outlet (m) of the methanol separator is connected to a heat mixing pipe (11) and a vacuum tail gas pipe (21) in sequence, and a pipeline separator (12), a pressure control system (13), a gravel flame arrester (14), a fire extinguishing steam pipe (15), a front temperature control system (16), a safety water seal (17), a stainless steel flame arrester (18) and a rear temperature control system (19) are installed on the vacuum tail gas pipe (21) in sequence and then connected to a combustion furnace (20). The end of the vacuum tail gas pipe (21) is bent downward and reduced in diameter to facilitate concentrated combustion of the tail gas.

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