A process for the recovery of extract oil from a furfural refining unit

Abstract

The present application provides a kind of for furfural refining device extraction oil recovery system, comprising: de-aldehyde tower A, de-aldehyde tower B, reagent pump, de-aldehyde tower top cooler and de-aldehyde tower top liquid separator, compared with prior art, the present application has the beneficial effects as follows: the double-tower design of de-aldehyde tower A and de-aldehyde tower B reduces the number of trays of each tower, which can reduce the tower pressure, reduce the partial pressure of furfural at the bottom of stripping tower, facilitate the separation of furfural and extraction oil;Second, it can adapt to different furfural content of extraction oil, when the furfural content in extraction oil is low, only de-aldehyde tower A can be used, when the furfural content in extraction oil is high, de-aldehyde tower A and de-aldehyde tower B can be used simultaneously, to improve the flexibility of the whole system, inject alkaline reagent before extraction oil enters stripping tower, remove acidic substances in extraction oil, make furfural more easily and extraction oil separate.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, and specifically relates to an oil recovery system for furfural refining units. Background Technology

[0002] Furfural refining, a commonly used heavy oil processing technology, typically uses furfural as a solvent. Based on the physical property that furfural solvent has varying solubility for different components in the raw material, it exhibits high solubility for polycyclic aromatic hydrocarbons with short side chains, colloids, sulfur and nitrogen compounds, while being insoluble or sparingly soluble for oligocyclic aromatic hydrocarbons with long side chains, cycloalkanes, and alkanes. Refined oil and extractable oil are obtained through liquid-liquid extraction. When the raw materials processed by the furfural refining unit are furfural extractable oil, catalytic cracking slurry oil, coking wax oil, etc., these raw materials have a high aromatic content, especially furfural extractable oil and catalytic slurry oil, where the aromatic composition is generally above 50%. Furfural extraction further concentrates the aromatics into the product extractable oil, resulting in an aromatic composition typically exceeding 70%.

[0003] Problems with furfural refining of high aromatic hydrocarbon components: Due to the large electrostatic interaction between furfural and aromatic hydrocarbon molecules and their good miscibility, they are not easy to separate. After solvent recovery through the conventional furfural unit's extract oil system, furfural residues in the product extract oil are high, generally ranging from several hundred to tens of thousands of ppm, resulting in significant furfural loss. The extract oil has a distinct aldehyde odor, high viscosity, and requires high storage temperatures. During long-term storage, furfural gradually volatilizes, generating a strong odor in the tank area and causing environmental problems.

[0004] Because furfural and extracted oil are highly miscible, traditional methods using a single stripping tower are limited by tower height and pressure drop, making it impossible to ensure that the furfural content in the extracted oil does not exceed 100 ppm, especially when furfural content is high. Furthermore, the traditional single-stripping method results in large fluctuations in furfural content in the extracted oil, easily leading to substandard quality. Therefore, it is desirable to develop an extracted oil recovery system for a furfural refining unit to solve the aforementioned technical problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an oil recovery system for furfural refining equipment, thereby resolving the problems mentioned in the background section.

[0006] This invention is achieved through the following technical solution: a furfural refining unit oil extraction recovery system, comprising: a de-formaldehyde tower A, a de-formaldehyde tower B, a reagent pump, a de-formaldehyde tower top cooler, and a de-formaldehyde tower top separating tank. The de-formaldehyde tower A is connected in series with the de-formaldehyde tower B via a pipeline. The de-formaldehyde tower A is connected to the reagent pump via a pipeline. The de-formaldehyde tower B is connected to the de-formaldehyde tower top cooler via a pipeline. The de-formaldehyde tower top cooler is connected to the de-formaldehyde tower top separating tank via a pipeline. The upper end of the de-formaldehyde tower top separating tank is connected to a vacuum pumping device via a vacuum tube. The lower end of the de-formaldehyde tower top separating tank is connected to a water solvent tank via a liquid pipe.

[0007] In a preferred embodiment, the formaldehyde removal tower A is connected to the feed heater of formaldehyde removal tower A via a pipeline and a regulating valve, and the feed heater of formaldehyde removal tower A is connected to the raw material product heat exchanger via a pipeline.

[0008] The raw material product heat exchanger is connected to the product cooler via pipeline, the raw material product heat exchanger is connected to the raw material reagent mixer via pipeline, and the raw material reagent mixer is connected to the reagent pump via pipeline;

[0009] After the aldehyde-containing extractable oil is controlled by a valve, it enters the raw material reagent mixer. The reagent is pumped into the raw material reagent mixer, where the aldehyde-containing extractable oil and the reagent are mixed evenly. Organic acids (such as furfural) in the aldehyde-containing extractable oil and the reagent undergo a neutralization reaction in the raw material reagent mixer. In actual use, an alkaline reagent is injected into the aldehyde-containing extractable oil. The amount of alkaline reagent injected is usually 5 to 20 ppm of the aldehyde-containing extractable oil. The specific injection amount can be adjusted according to the acid value of the aldehyde-containing extractable oil and the stripping and dealdehyde removal effect. If the acid value is high and the dealdehyde removal effect is poor, the injection amount can be appropriately increased. The alkaline reagent can be an organic amine, an inorganic alkali (such as potassium hydroxide), or a compound reagent. Organic amine reagents can avoid scaling problems, but the mixing temperature should not be too high to avoid amine decomposition. Inorganic alkalis have a wide temperature range, but they are prone to scaling. The mixing temperature is effective in a wide range. The temperature of the aldehyde-containing extractable oil is generally between 90 and 180°C. Higher temperatures are beneficial to the mixing reaction.

[0010] In a preferred embodiment, the raw material mixer is an SV-type pipeline mixer, and the formaldehyde removal tower A is a plate-type formaldehyde removal tower. The formaldehyde removal tower A has 15 to 20 trays inside, and all the trays inside the formaldehyde removal tower A are installed at an inclination. The inclination angle of the trays is greater than or equal to 5 degrees. The liquid receiving tray of the tray does not have an inlet weir. The bottom of the formaldehyde removal tower A is connected to the bottom pump of the formaldehyde removal tower A through a pipeline.

[0011] After the reaction, the aldehyde-containing extract oil first enters the raw material product heat exchanger to exchange and recover the product heat. After heat exchange, it is heated to 210°C by the feed heater of the dealdehyde removal tower A and then enters the third tray at the top of the dealdehyde removal tower A. Stripping steam is injected into the bottom of the dealdehyde removal tower A. The aldehyde-containing extract oil and the stripping steam come into countercurrent contact in the top of the dealdehyde removal tower A and on the tray. Under high temperature and high vacuum conditions, the relative volatility of furfural increases. After adding alkaline reagents to remove acidic substances, furfural is more easily separated from the extract oil. The extract oil with furfural removed is obtained at the bottom of the dealdehyde removal tower A.

[0012] In practical applications, the plate-type formaldehyde removal tower has good anti-clogging and anti-coking capabilities, high operational flexibility, and the SV-type pipeline mixer can make the formaldehyde-containing extractable oil and reagents mix more evenly and react more completely. Generally, the stripping separation of furfural and extractable oil requires 20 to 40 trays depending on the furfural content. This invention adopts a dual-tower design, reducing the number of trays in each tower. First, it can reduce the tower pressure and the partial pressure of furfural at the bottom of the stripping tower, which is conducive to the separation of furfural and extractable oil. Second, it can adapt to different furfural contents in the extractable oil. When the furfural content in the extractable oil is low, such as below 1000 ppm, only formaldehyde removal tower A can be used. When the furfural content in the extractable oil is greater than 1000 ppm, formaldehyde removal tower A and formaldehyde removal tower B can be used simultaneously. Through dual-tower stripping, the furfural content in the extractable oil can be guaranteed to be no more than 100 ppm, and the operation is stable.

[0013] Considering that the extracted oil contains a small amount of coke powder, the injection of reagents containing inorganic alkali may increase the tendency to scale. Therefore, the trays are installed at an angle of 5° or greater, and no inlet weir is provided on the liquid receiving tray. This can prevent the deposition of coke powder and solid impurities.

[0014] In a preferred embodiment, the bottom pump of the formaldehyde removal tower A is connected to the feed heater of the formaldehyde removal tower B through a pipeline, and the feed heater of the formaldehyde removal tower B is connected to the formaldehyde removal tower B through a pipeline. The specifications of the formaldehyde removal tower B are the same as those of the formaldehyde removal tower A.

[0015] The material at the bottom of the formaldehyde removal tower A is drawn out by the bottom pump of the formaldehyde removal tower A, heated to 215°C by the feed heater of the formaldehyde removal tower B, and then enters the third tray at the top of the formaldehyde removal tower B. Stripping steam is injected into the bottom of the formaldehyde removal tower B. The formaldehyde-containing extracted oil and the stripping steam come into countercurrent contact in the formaldehyde removal tower B and on the tray. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural and extracted oil separate. After stripping, the remaining formaldehyde-containing extracted oil is removed, and the furfural-free extracted oil is obtained at the bottom of the formaldehyde removal tower B.

[0016] In a preferred embodiment, the lower end of the formaldehyde removal tower B is connected to the bottom pump of the formaldehyde removal tower B via a pipeline, and the bottom pump of the formaldehyde removal tower B is connected to the raw material product heat exchanger via a pipeline.

[0017] The oil extracted after furfural is removed from the formaldehyde removal tower B is pumped out by the bottom pump of the formaldehyde removal tower B, transported through pipelines to the raw material product heat exchanger for heat exchange, and then enters the product cooler for cooling before being sent out of the device.

[0018] In a preferred embodiment, the top of the formaldehyde removal tower A is connected to the formaldehyde removal tower top cooler via a pipeline, the top of the formaldehyde removal tower B is connected to the formaldehyde removal tower top cooler via a pipeline, and the formaldehyde removal tower top cooler is connected to the formaldehyde removal tower top separator via a pipeline.

[0019] After the top gases from formaldehyde removal towers A and B are combined, they enter the top cooler of the formaldehyde removal towers and are condensed and cooled to below 40°C. Then, they enter the top separator of the formaldehyde removal towers for gas-liquid separation. The top gas separated from the top separator of the formaldehyde removal towers is sent to the vacuum equipment for vacuuming. The vacuum equipment controls the top pressure of formaldehyde removal towers A and B at -85 kPa(G). The liquid separated from the top separator of the formaldehyde removal towers flows by gravity into the existing water solvent tank of the device and is finally transported to the water recovery system. In actual use, the top gases of formaldehyde removal towers A and B are connected in parallel, while the formaldehyde-containing oil extraction process is in series.

[0020] After adopting the above technical solution, the beneficial effects of the present invention are: by setting up formaldehyde removal tower A and formaldehyde removal tower B, the product extract oil of conventional furfural unit is processed to further remove residual furfural in the extract oil. It is particularly suitable for removing furfural from extract oil with high aromatic composition. After removing residual furfural from the extract oil, the furfural consumption of furfural unit can be reduced and environmental pollution can be reduced.

[0021] The dual-tower design of stripping tower A and stripping tower B reduces the number of trays in each tower. This has two advantages: first, it lowers the tower pressure and the partial pressure of furfural at the bottom of the stripping tower, which is beneficial for the separation of furfural and extracted oil; second, it can adapt to different furfural contents in the extracted oil. When the furfural content in the extracted oil is low, only stripping tower A can be used. When the furfural content in the extracted oil is high, stripping tower A and stripping tower B can be used simultaneously, improving the overall system's operational flexibility.

[0022] The formaldehyde removal unit of the entire recovery system can reduce the furfural content in the extracted oil. It can effectively handle materials with furfural content ranging from hundreds to tens of thousands of ppm in the extracted oil, and can meet the requirement that the furfural content in the extracted oil is no more than 100 ppm. The operating indicators are stable, and the entire recovery system has low investment and is easy to operate. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the working process of an oil recovery system for a furfural refining unit according to the present invention.

[0025] Figure 2 This is a schematic diagram of a tray structure for an oil recovery system in a furfural refining unit according to the present invention.

[0026] In the diagram, 100-formaldehyde removal tower B, 110-formaldehyde removal tower B feed heater, and 120-formaldehyde removal tower B bottom pump are shown.

[0027] 200 - Formaldehyde removal tower A, 210 - Formaldehyde removal tower A feed heater, 220 - Product cooler, 230 - Raw material and product heat exchanger, 240 - Raw material and reagent mixer, 250 - Formaldehyde removal tower A bottom pump;

[0028] 300-Pharmaceutical Pump;

[0029] 400-Formaldehyde Removal Tower Top Cooler;

[0030] 500-Formaldehyde removal tower top separator. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figures 1 to 2 This invention provides a technical solution: an oil recovery system for a furfural refining unit, comprising: a dealdehyde removal tower A200, a dealdehyde removal tower B100, a reagent pump 300, a dealdehyde removal tower top cooler 400, and a dealdehyde removal tower top separating tank 500. The dealdehyde removal tower A200 is connected in series with the dealdehyde removal tower B100 via a pipeline. The dealdehyde removal tower A200 is connected to the reagent pump 300 via a pipeline. The dealdehyde removal tower B100 is connected to the dealdehyde removal tower top cooler 400 via a pipeline. The dealdehyde removal tower top cooler 400 is connected to the dealdehyde removal tower top separating tank 500 via a pipeline. The upper end of the dealdehyde removal tower top separating tank 500 is connected to a vacuum pumping device via a vacuum tube, and the lower end of the dealdehyde removal tower top separating tank 500 is connected to a water solvent tank via a liquid pipe.

[0033] Please see Figure 1 The formaldehyde removal tower A200 is connected to the formaldehyde removal tower A feed heater 210 through pipes and regulating valves. The formaldehyde removal tower A feed heater 210 is connected to the raw material product heat exchanger 230 through pipes.

[0034] The raw material product heat exchanger 230 is connected to the product cooler 220 through a pipeline, the raw material product heat exchanger 230 is connected to the raw material reagent mixer 240 through a pipeline, and the raw material reagent mixer 240 is connected to the reagent pump 300 through a pipeline.

[0035] The aldehyde-containing extractable oil, after flow control via a valve, enters the raw material mixer 240. The reagent is then pumped into the raw material mixer 240 by the reagent pump 300. The aldehyde-containing extractable oil and reagent are mixed evenly in the raw material mixer 240. Organic acids (such as furfural acid) in the aldehyde-containing extractable oil and the reagent undergo a neutralization reaction in the raw material mixer 240. In actual use, an alkaline reagent is injected into the aldehyde-containing extractable oil. The amount of alkaline reagent injected is typically 5 to 20 ppm of the aldehyde-containing extractable oil volume. The injection volume can be adjusted according to the acid value of the aldehyde-containing extracted oil and the stripping and dealdehyde removal effect. If the acid value is high and the dealdehyde removal effect is poor, the injection volume can be appropriately increased. Alkaline agents can be organic amines, inorganic bases (such as potassium hydroxide), or compound agents. Organic amine agents can avoid scaling problems, but the mixing temperature should not be too high to avoid amine decomposition. Inorganic bases have a wide temperature range, but they are prone to scaling. The mixing temperature is effective in a wide range. The temperature of the aldehyde-containing extracted oil is generally between 90 and 180°C. Higher temperatures are beneficial to the mixing reaction.

[0036] As a first embodiment of the present invention, the aldehyde-containing extractable oil enters the raw material and reagent mixer 240 after flow control, and the alkaline reagent also enters the raw material and reagent mixer 240 after the required flow is controlled by the reagent pump 300. The aldehyde-containing extractable oil and the reagent are mixed evenly in the raw material and reagent mixer 240, and the organic acid (such as furfural acid) in the aldehyde-containing extractable oil and the reagent undergo a neutralization reaction in the raw material and reagent mixer 240.

[0037] Adding alkaline agents reduces the compatibility between furfural and extracted oil, making it easier for furfural to separate from the extracted oil in the downstream dealdehyde removal tower. At the same time, since the extracted oil has a high acid value, adding alkaline agents can neutralize the organic acids in the extracted oil, reduce the acid value of the aldehyde-containing extracted oil, and also reduce equipment corrosion.

[0038] Please see Figures 1 to 2 The raw material mixer 240 is an SV type pipeline mixer, and the formaldehyde removal tower A200 is a plate-type formaldehyde removal tower. The formaldehyde removal tower A200 has 15 to 20 trays inside. All the trays inside the formaldehyde removal tower A200 are installed at an inclination angle of 5 degrees or more. The liquid receiving tray of the tray does not have an inlet weir. The bottom of the formaldehyde removal tower A200 is connected to the bottom pump 250 of the formaldehyde removal tower A through a pipeline.

[0039] After the reaction, the aldehyde-containing extract oil first enters the raw material product heat exchanger 230 to recover the product heat. After heat exchange, it is heated to 210°C by the feed heater 210 of the dealdehyde removal tower A and then enters the third tray at the top of the dealdehyde removal tower A200. Stripping steam is injected into the bottom of the dealdehyde removal tower A200. The aldehyde-containing extract oil and the stripping steam come into countercurrent contact in the top of the dealdehyde removal tower A200 and on the tray. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural is more easily separated from the extract oil. The extract oil with furfural removed is obtained at the bottom of the dealdehyde removal tower A200.

[0040] In practical applications, plate-type formaldehyde removal towers exhibit good anti-clogging and anti-coking capabilities, high operational flexibility, and SV-type pipeline mixers ensure more uniform mixing and more complete reaction of the aldehyde-containing extractable oil and reagents. Generally, the stripping separation of furfural and extractable oil requires 20 to 40 trays depending on the furfural content. We adopt a dual-tower design, reducing the number of trays in each tower. This reduces the tower pressure and the partial pressure of furfural at the bottom of the stripping tower, facilitating the separation of furfural and extractable oil. Secondly, it can adapt to different furfural contents in the extractable oil. When the furfural content in the extractable oil is low, such as below 1000 ppm, only formaldehyde removal tower A200 can be used. When the furfural content in the extractable oil is greater than 1000 ppm, both formaldehyde removal towers A200 and B100 can be used simultaneously. Through dual-tower stripping, the final result can ensure that the furfural content in the extractable oil does not exceed 100 ppm, and the operation is stable.

[0041] Considering that the extracted oil contains a small amount of coke powder, the injection of reagents containing inorganic alkali may increase the tendency to scale. Therefore, the trays are installed at an angle of 5° or greater, and no inlet weir is provided on the liquid receiving tray. This can prevent the deposition of coke powder and solid impurities.

[0042] The bottom pump 250 of the formaldehyde removal tower A is connected to the feed heater 110 of the formaldehyde removal tower B through a pipeline. The feed heater 110 of the formaldehyde removal tower B is connected to the formaldehyde removal tower B100 through a pipeline. The specifications of the formaldehyde removal tower B100 are the same as those of the formaldehyde removal tower A200.

[0043] The material at the bottom of the formaldehyde removal tower A200 is drawn out by the bottom pump 250 of the formaldehyde removal tower A, heated to 215°C by the feed heater 110 of the formaldehyde removal tower B, and then enters the third tray at the top of the formaldehyde removal tower B100. Stripping steam is injected into the bottom of the formaldehyde removal tower B100. The formaldehyde-containing extracted oil and the stripping steam come into countercurrent contact in the formaldehyde removal tower B100 and on the tray. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural and extracted oil separate. After stripping, the remaining formaldehyde-containing extracted oil is removed, and the furfural-free extracted oil is obtained at the bottom of the formaldehyde removal tower B100.

[0044] The lower end of the formaldehyde removal tower B100 is connected to the bottom pump 120 of the formaldehyde removal tower B through a pipeline, and the bottom pump 120 of the formaldehyde removal tower B is connected to the raw material and reagent mixer 240 through a pipeline.

[0045] The oil extracted after furfural is removed from the formaldehyde removal tower B100 is pumped out by the bottom pump 120 of the formaldehyde removal tower B, and transported through pipeline to the raw material product heat exchanger 230 for heat exchange. After being cooled in the product cooler 220, it is sent out of the device.

[0046] The top of the formaldehyde removal tower A200 is connected to the formaldehyde removal tower top cooler 400 via a pipeline, the top of the formaldehyde removal tower B100 is connected to the formaldehyde removal tower top cooler 400 via a pipeline, and the formaldehyde removal tower top cooler 400 is connected to the formaldehyde removal tower top separator 500 via a pipeline.

[0047] The gases from the top of formaldehyde removal towers A200 and B100 are combined and then condensed and cooled to below 40°C in the top cooler 400. They then enter the top separator 500 for gas-liquid separation. The gas separated from the top of separator 500 is then evacuated by a vacuum pump, which controls the pressure at the top of both towers A200 and B100 at -85 kPa(G). The liquid separated from separator 500 flows by gravity into the existing water solvent tank and is ultimately transported to the water recovery system. In actual use, the top gases from formaldehyde removal towers A200 and B100 are connected in parallel, while the aldehyde-containing oil extraction process is conducted in series.

[0048] As a second embodiment of the present invention, based on the first embodiment described above, the aldehyde-containing extracted oil after the reaction is first exchanged with the raw material product heat exchanger 230 to recover the product heat, and then heated to 210°C by the feed heater 210 of the dealdehyde removal tower A before entering the third tray at the top of the dealdehyde removal tower A200. The heating temperature can be adjusted according to the dealdehyde removal effect, generally between 200 and 225°C. If the heating temperature is too low, the dealdehyde removal effect will be poor, and if the heating temperature is too high, furfural is prone to coking.

[0049] Stripping steam (or other stripping media such as nitrogen) is injected into the bottom of the formaldehyde removal tower A200. The formaldehyde-containing extract oil comes into countercurrent contact with the stripping steam on the trays in the top of the formaldehyde removal tower A200. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural is more easily separated from the extract oil. After stripping, more than 90% of the furfural in the formaldehyde-containing extract oil can be removed, and extract oil with most of the furfural removed is obtained at the bottom of the formaldehyde removal tower A200.

[0050] The material at the bottom of the formaldehyde removal tower A200 is extracted by the bottom pump 250 of the formaldehyde removal tower A, heated to 215°C by the feed heater 110 of the formaldehyde removal tower B, and then enters the third tray at the top of the formaldehyde removal tower B100. The heating temperature can be adjusted according to the formaldehyde removal effect, generally between 200 and 225°C. Stripping steam (or other stripping media such as nitrogen) is injected into the bottom of the formaldehyde removal tower B100. The formaldehyde-containing extracted oil and the stripping steam come into countercurrent contact on the tray in the formaldehyde removal tower B100. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural is more easily separated from the extracted oil. After stripping, the remaining formaldehyde-containing extracted oil is stripped, and the furfural-free extracted oil is obtained at the bottom of the formaldehyde removal tower B100. After two-stage stripping operation, the furfural content in the extracted oil can be stably controlled to no more than 100 ppm.

[0051] The remaining oil at the bottom of the formaldehyde removal tower B100 is the extracted oil after furfural removal. The extracted oil after furfural removal is extracted by the bottom pump 120 of the formaldehyde removal tower B. It first exchanges heat with the raw material product heat exchanger 230, and then is cooled by the product cooler 220 before being sent out of the device.

[0052] The cooled product oil at the top of formaldehyde removal towers A200 and B100 is refluxed to maintain the tower top temperature at approximately 130°C. The gases from the top of formaldehyde removal towers A200 and B100 are combined and condensed to below 40°C by the formaldehyde removal tower top cooler 400. The gases then enter the formaldehyde removal tower top separator 500 for gas-liquid separation. The gas separated from the top of the separator 500 is sent to a vacuum pump to create a vacuum. The vacuum pump controls the pressure at the top of formaldehyde removal towers A200 and B100 at -85 kPa(G). The liquid separated from the separator 500 flows by gravity into the existing water solvent tank in the unit and is finally transported to the water recovery system.

[0053] By setting up formaldehyde removal tower A200 and formaldehyde removal tower B100, the product extract oil of conventional furfural unit is processed to further remove residual furfural from the extract oil. It is particularly suitable for removing furfural from extract oil with high aromatic composition. After removing residual furfural from the extract oil, the furfural consumption of furfural unit can be reduced, and environmental pollution can be reduced.

[0054] The dual-tower design of the formaldehyde removal tower A200 and the formaldehyde removal tower B100 reduces the number of trays in each tower. This has two advantages: first, it lowers the tower pressure and the partial pressure of furfural at the bottom of the stripping tower, which is beneficial for the separation of furfural and extracted oil; second, it can adapt to different furfural contents in the extracted oil. When the furfural content in the extracted oil is low, only the formaldehyde removal tower A200 can be used. When the furfural content in the extracted oil is high, both the formaldehyde removal tower A200 and the formaldehyde removal tower B100 can be used simultaneously, improving the overall system's operational flexibility.

[0055] The formaldehyde removal unit of the entire recovery system can reduce the furfural content in the extracted oil. It can process materials with furfural content ranging from several hundred to tens of thousands of ppm in the extracted oil, and can meet the requirement that the furfural content in the extracted oil is no more than 100 ppm. The operating indicators are stable. The entire recovery system has low investment and is easy to operate (the above-mentioned 2 formaldehyde removal towers, 1 heat exchanger, 2 heaters, 1 cooler, 3 pumps, mixer and control system, etc., can all be conventional chemical equipment. It is worth noting that the 2 formaldehyde removal towers, namely formaldehyde removal tower A200 and formaldehyde removal tower B100, are formed by modifying the existing plate formaldehyde removal towers. The only changes are reducing the number of tower trays, changing the installation tilt angle of the tower trays and not setting the inlet weir at the tower tray inlet. The rest remains unchanged. Formaldehyde removal towers A200 and B100 are formed by modifying existing equipment. Their structure has been explained above, and their specific structure and working principle will not be repeated here).

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A furfural refining unit's extracted oil recovery system, comprising: The formaldehyde removal tower A (200), formaldehyde removal tower B (100), reagent pump (300), formaldehyde removal tower top cooler (400), and formaldehyde removal tower top separator (500) are characterized in that the formaldehyde removal tower A (200) is connected in series with the formaldehyde removal tower B (100) through a pipe, the formaldehyde removal tower A (200) is connected to the reagent pump (300) through a pipe, the formaldehyde removal tower B (100) is connected to the formaldehyde removal tower top cooler (400) through a pipe, the formaldehyde removal tower top cooler (400) is connected to the formaldehyde removal tower top separator (500) through a pipe, the upper end of the formaldehyde removal tower top separator (500) is connected to a vacuum pumping device through a vacuum tube, and the lower end of the formaldehyde removal tower top separator (500) is connected to a water solvent tank through a liquid pipe; The formaldehyde removal tower A (200) is connected to the formaldehyde removal tower A feed heater (210) via a pipe and a switch valve. The formaldehyde removal tower A feed heater (210) is connected to the raw material product heat exchanger (230) via a pipe. The raw material product heat exchanger (230) is connected to the product cooler (220) through a pipeline, the raw material product heat exchanger (230) is connected to the raw material agent mixer (240) through a pipeline, and the raw material agent mixer (240) is connected to the agent pump (300) through a pipeline. After the aldehyde-containing extract oil is controlled by a valve, it enters the raw material agent mixer (240). The agent is sent into the raw material agent mixer (240) by the agent pump (300). The aldehyde-containing extract oil and the agent are mixed evenly in the raw material agent mixer (240). The organic acid in the aldehyde-containing extract oil and the agent undergo a neutralization reaction in the raw material agent mixer (240). The raw material mixer (240) is an SV type pipeline mixer, and the formaldehyde removal tower A (200) is a plate formaldehyde removal tower. The formaldehyde removal tower A (200) is equipped with 15 to 20 layers of tower trays. The multiple layers of tower trays inside the formaldehyde removal tower A (200) are all installed at an inclination. The installation inclination angle of the multiple layers of tower trays is greater than or equal to 5 degrees. The liquid receiving tray of the tower tray is not equipped with an inlet weir. The bottom of the formaldehyde removal tower A (200) is connected to the bottom pump (250) of the formaldehyde removal tower A through a pipeline. After the reaction, the aldehyde-containing extract oil first enters the raw material product heat exchanger (230) to exchange and recover the product heat. After the heat exchange, it is heated to 210°C by the feed heater (210) of the dealdehyde removal tower A and then enters the third tray at the top of the dealdehyde removal tower A (200). Stripping steam is injected into the bottom of the dealdehyde removal tower A (200). The aldehyde-containing extract oil and the stripping steam are in countercurrent contact in the top of the dealdehyde removal tower A (200) and on the tray. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural and extract oil are separated. At the bottom of the dealdehyde removal tower A (200), extract oil with furfural removed is obtained.

2. The oil recovery system for a furfural refining unit as described in claim 1, characterized in that: The bottom pump (250) of the formaldehyde removal tower A is connected to the feed heater (110) of the formaldehyde removal tower B through a pipeline. The feed heater (110) of the formaldehyde removal tower B is connected to the formaldehyde removal tower B (100) through a pipeline. The specifications of the formaldehyde removal tower B (100) are the same as those of the formaldehyde removal tower A (200). The material at the bottom of the formaldehyde removal tower A (200) is drawn out by the bottom pump (250) of the formaldehyde removal tower A and heated to 215°C by the feed heater (110) of the formaldehyde removal tower B before entering the third tray at the top of the formaldehyde removal tower B (100). Stripping steam is injected into the bottom of the formaldehyde removal tower B (100). The formaldehyde-containing extracted oil and the stripping steam are in countercurrent contact in the formaldehyde removal tower B (100) and on the tray. Under high temperature and high vacuum conditions, the relative volatility of furfural increases, and furfural and extracted oil are separated. After stripping, the remaining formaldehyde-containing extracted oil is removed and the furfural-free extracted oil is obtained at the bottom of the formaldehyde removal tower B (100).

3. The oil recovery system for a furfural refining unit as described in claim 2, characterized in that: The lower end of the formaldehyde removal tower B (100) is connected to the bottom pump (120) of the formaldehyde removal tower B through a pipeline, and the bottom pump (120) of the formaldehyde removal tower B is connected to the raw material product heat exchanger (230) through a pipeline. The oil extracted after furfural is removed from the dealdehyde tower B (100) is pumped out by the bottom pump (120) of the dealdehyde tower B, and transported through pipeline to the raw material product heat exchanger (230) for heat exchange. After being cooled in the product cooler (220) from the raw material product heat exchanger (230), it is sent out of the device.

4. The oil recovery system for a furfural refining unit as described in claim 3, characterized in that: The top of the formaldehyde removal tower A (200) is connected to the formaldehyde removal tower top cooler (400) via a pipeline, the top of the formaldehyde removal tower B (100) is connected to the formaldehyde removal tower top cooler (400) via a pipeline, and the formaldehyde removal tower top cooler (400) is connected to the formaldehyde removal tower top separator (500) via a pipeline. The gases from the top of the formaldehyde removal tower A (200) and the formaldehyde removal tower B (100) are combined and then enter the formaldehyde removal tower top cooler (400) to be condensed and cooled to below 40°C. The gases then enter the formaldehyde removal tower top separator (500) for gas-liquid separation. The gas separated from the top of the formaldehyde removal tower top separator (500) is sent to the vacuum pump to be evacuated. The vacuum pump controls the pressure at the top of the formaldehyde removal tower A (200) and the formaldehyde removal tower B (100) at -85KPaG. The liquid separated from the formaldehyde removal tower top separator (500) flows by gravity into the existing water solvent tank of the device and is finally transported to the water recovery system.

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