Decolorization treatment system and treatment method during the startup and heating process of producing fuel ethanol

Abstract

The present invention provides a decolorization treatment system and method during the start-up heating process of fuel ethanol production. The system includes a molecular sieve tower group connected to a rectification tower. One end of the regeneration end of the molecular sieve tower group is connected to a reverse discharge tank, and the other end of the pipeline at the regeneration end of the molecular sieve tower group is connected to the feed end of a vacuum heat exchanger. The first outlet end of the vacuum heat exchanger is connected to a vacuum tank, one end of the vacuum tank is connected to a vacuum pump, and the outlet end of the exhaust pipeline of the vacuum pump is connected to a light wine tank. The inlet of the light wine tank is connected to the cooling water pipeline of the vacuum heat exchanger. The discharge end of the molecular sieve tower group is connected to a fuel ethanol heat exchanger and is refluxed through a switching valve. The beneficial effects of the present invention: Through the process improvement of further refluxing and reducing the alcohol content of the fuel ethanol with unqualified chromaticity in the initial stage of heating during fuel ethanol production, the influence of unqualified alcohol quality caused by the low temperature in the tower during the initial stage of start-up heating of the molecular sieve tower group is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel ethanol production, and particularly relates to a decolorization treatment system and a treatment method during the start-up and temperature-raising process of fuel ethanol production. Background Art

[0002] Fuel ethanol generally refers to anhydrous ethanol with a volume concentration of more than 99.5%. Fuel ethanol belongs to renewable energy, which can be directly used as a liquid fuel or mixed with gasoline, reducing the dependence on non-renewable energy (petroleum) and ensuring the energy security of the country. In order to ensure the quality of fuel ethanol, it is necessary to decolorize the fed ethanol so that its chromaticity reaches a certain standard to effectively guarantee the quality of fuel ethanol. Currently, in the production of fuel ethanol, the molecular sieve adsorption method is usually used for decolorization adsorption treatment.

[0003] The molecular sieve adsorption method is a technology that uses molecular sieves to adsorb and desorb water from the fed ethanol vapor. Molecular sieves are materials made into granular or spherical shapes through attapulgite, with micropores of controlled size. Usually, 3A synthetic zeolite is used. Since the pore diameter is 3A, the water molecule is 2.8A, and the ethanol molecule is 4.4A. The alcohol molecule is larger than the water molecule, and the water molecule can be adsorbed in the pores, while the ethanol molecule cannot be adsorbed and is repelled. When the water-containing alcohol vapor passes through the molecular sieve adsorption bed, the molecular sieve adsorbs the water, and the ethanol vapor passes through the adsorption bed to become dry ethanol products.

[0004] During the actual application process, the applicant found that during the start-up and temperature-raising process of the molecular sieve tower, due to the low temperature of the molecular sieve, during the heating process, when the high-temperature alcohol vapor flows through the molecular sieve bed layer, some molecular sieves may be pulverized after being washed and rubbed. The pulverized molecular sieves are likely to cause the chromaticity of the product fuel ethanol to exceed 30 numbers at the initial stage of start-up, while the chromaticity meeting the standard needs to be 10 numbers and below. Therefore, the fuel ethanol at the initial stage of temperature rise cannot reach the required product standard, resulting in unqualified product quality of the final fuel ethanol. Summary of the Invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a decolorization treatment system and a treatment method during the start-up and temperature-raising process of fuel ethanol production.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] Decolorization treatment system during the startup and heating process of producing fuel ethanol, including a molecular sieve tower group connected to a rectifying tower. One end of the regeneration end of the molecular sieve tower group is connected to a reverse discharge tank, and the other end of the pipeline at the regeneration end of the molecular sieve tower group is connected to the feed end of a vacuum heat exchanger. The first outlet end of the vacuum heat exchanger is connected to a vacuum tank, one end of the vacuum tank is connected to a vacuum pump, and the outlet end of the exhaust pipeline of the vacuum pump is connected to a weak wine tank; the inlet of the weak wine tank is connected to the cooling water pipeline of the vacuum heat exchanger, and the discharge end of the molecular sieve tower group is connected to a fuel ethanol heat exchanger and refluxed through a switching valve.

[0008] Preferably, one end of the weak wine tank is further connected to a vacuum heat exchanger, and the cooling water of the heat exchanger enters the weak wine tank through a switching valve. The other end of the weak wine tank is connected to the exhaust pipe of the vacuum pump to receive the weak wine absorbed by the vacuum pump.

[0009] Preferably, the vacuum heat exchanger includes a first vacuum heat exchanger and a second vacuum heat exchanger connected to the first vacuum heat exchanger, and one end of the second vacuum heat exchanger is connected to the vacuum tank.

[0010] Preferably, the molecular sieve tower group includes three molecular sieve towers connected in parallel.

[0011] Preferably, the reverse discharge tank is connected to a recovery tower through a reverse discharge pump group, and the reverse discharge pump group is two reverse discharge pumps connected in parallel.

[0012] Preferably, the fuel ethanol return outlet end of the fuel ethanol heat exchanger is also connected to the weak wine tank through a pipeline, and a valve is provided between the fuel ethanol return outlet end and the weak wine tank.

[0013] Preferably, the treatment method of the decolorization treatment system during the startup and heating process of producing fuel ethanol as described in any one of the above includes the following steps:

[0014] S1. The ordinary alcohol passing through the rectifying tower is heated by an evaporator and a superheater and then enters the molecular sieve tower group, and the regeneration gas enters the vacuum heat exchanger through the upper end of the molecular sieve tower group;

[0015] S2. The material after dehydration and adsorption separation by the molecular sieve tower group forms fuel ethanol after heat exchange through the fuel ethanol heat exchanger;

[0016] S3. The chromaticity of the fuel ethanol product formed in the initial stage of dehydration does not meet the standard. At this time, the non-compliant fuel ethanol is refluxed to the weak wine tank through a pipeline. The weak wine tank is supplemented with water and the cooling water of the vacuum heat exchanger through the exhaust pipe of the vacuum pump and mixed with the fuel ethanol entering the weak wine tank to dilute the alcohol content to 10%vol - 20%vol;

[0017] S4. The diluted fuel ethanol enters the recovery column through the light wine tank for subsequent rectification to further separate the molecular sieve powder in the fuel ethanol. The separated molecular sieve powder is discharged through the wastewater at the bottom of the recovery column.

[0018] S5. When the color of the fuel ethanol after the material discharged from the molecular sieve tower group enters the fuel ethanol heat exchanger meets the requirements, it indicates that the decolorization treatment is completed. Then, close the valve between the fuel ethanol heat exchanger and the light wine tank, and normal subsequent production can be carried out.

[0019] Preferably, for the treatment method of the decolorization treatment system during the start-up and heating process of fuel ethanol production, when diluting the alcohol content of the fuel ethanol in the light wine tank in S3, the cooling water in the vacuum heat exchanger and the primary water in the outlet exhaust pipe of the vacuum pump selectively enter the light wine tank for alcohol content dilution.

[0020] Preferably, for the treatment method of the decolorization treatment system during the start-up and heating process of fuel ethanol production, S1 includes the following steps: The ordinary alcohol passing through the rectification column is heated by the evaporator and the heater and then enters the molecular sieve tower group. The regeneration gas first enters the reverse release tank to extract part of the light wine during the regeneration process to reduce the load on the heat exchanger and the vacuum pump. After completion, close the valve between the reverse release tank and the molecular sieve tower group, and open the valve between the molecular sieve tower group and the vacuum heat exchanger to make the regeneration gas enter the vacuum heat exchanger.

[0021] The beneficial effects of the present invention: Through the process improvement of further refluxing and reducing the alcohol content of the fuel ethanol with unqualified color at the initial stage during the heating process of fuel ethanol production, it effectively improves the influence of the unqualified alcohol quality caused by the low temperature in the tower at the initial stage during the start-up and heating process of the molecular sieve tower group. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the system connection relationship of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention specifically discloses a decolorization treatment system during the start-up and heating process of fuel ethanol production, which includes a molecular sieve tower group connected to a rectification column. The molecular sieve tower group includes three molecular sieve towers 2 connected in parallel to each other.

[0024] One end of the regeneration end of the molecular sieve tower group is connected to the vacuum heat exchanger, and the other end is connected to the reverse discharge tank 3. The vacuum heat exchanger includes a first vacuum heat exchanger 6 and a second vacuum heat exchanger 7. The first outlet end of the second vacuum heat exchanger 7 is connected to the vacuum tank 9, and one end of the vacuum tank 9 is also connected to a vacuum pump. The second outlet end at the bottom of the first vacuum heat exchanger 6 is connected to the light wine tank 5; one inlet end of the light wine tank 5 is connected to the cooling water pipeline of the second vacuum heat exchanger 7, and the discharge end of the molecular sieve tower group is connected to the fuel ethanol heat exchanger 1.

[0025] The other end of the light wine tank 5 is connected to the exhaust pipe of the vacuum pump. The reverse discharge tank 3 is connected to the recovery tower through a reverse discharge pump group, and the reverse discharge pump group is two reverse discharge pumps 31 connected in parallel. The fuel ethanol discharge end of the fuel ethanol heat exchanger 1 is also connected to the light wine tank 5 through a pipeline, and a switching valve is provided between the fuel ethanol discharge end and the light wine tank 5.

[0026] The present invention also discloses a treatment method of the decolorization treatment system during the start-up and heating process of producing fuel ethanol using the above-mentioned method. For a better understanding of the treatment method of the present invention, the following further explains the specific precautions and principles of the molecular sieve tower.

[0027] First of all, the preparation method of fuel ethanol is that ethanol with an ethanol content of 92.4% (w / w%) and a water content of 7.6% (w / w) from the rectification tower enters the boundary area through flow control. The water-containing ethanol vapor is heated up through the evaporator and superheater. To ensure that the quality of the ethanol vapor entering the molecular sieve tower 2 in the molecular sieve tower group fully meets the feeding conditions, it can be achieved by strictly controlling the flow rate of the heating steam.

[0028] The molecular sieve adsorption tower group is composed of three molecular sieve towers 2 and a program control valve with a regulating function. Qualified ethanol vapor enters the molecular sieve tower 2 through the program control valve at the inlet of the molecular sieve tower 2 for dehydration. Usually, when in use, only one tower is performing adsorption in each time period. After dehydration, the product (water content ≤ 0.05%) is cooled to below 40°C through product condensation and cooler in sequence, and then sent out of the boundary area, and the product enters the metering tank.

[0029] Similar to the existing molecular sieve tower adsorption process, during the entire dehydration process, the adsorption time is mainly adjusted according to the feed flow rate, and the product quality can be monitored through outlet analysis. The flow rate and pressure of the feed to the molecular sieve bed during adsorption are controlled by a flow regulator and a pressure regulator of the molecular sieve dehydration unit. Under certain operating conditions, the water adsorption capacity of the adsorbent is determined by the performance of the adsorbent. Therefore, to adjust the product output, it is necessary to extend the adsorption time. However, extending the adsorption time is likely to cause breakthrough adsorption in the bed layer, resulting in the product not reaching the dehydration depth. The higher the feed flow rate, the shorter the contact time, and the less water is adsorbed. To improve the product purity, it is necessary to reduce the feed flow rate and increase the contact time.

[0030] When an adsorption tower finishes adsorption, the inlet program-controlled valve is closed, and the tower enters the regeneration process. The regeneration of the adsorption tower is completed through steps such as reverse release, pressure reduction, and evacuation. Each step of the regeneration cycle is based on a timed or pre-set event, and is completed by setting the valve opening degree to the position marked on the valve program, and is adjusted by the control system.

[0031] The pressure reduction step is a process of gradually relieving pressure and evacuating the molecular sieve bed layer. Gradually controlling the speed of pressure reduction can effectively prevent the abrasion caused by the strong scouring of the molecular sieve by the gas flow, effectively extend the service life, and at the same time is an effective process to reduce the instantaneous heat load and save the consumption of cooling water. All adjustment times, valve positions, and step times can be adjusted by the control system. Therefore, the flushing flow rate can be adjusted by setting the opening position and time of the valve.

[0032] The adsorption tower that has completed regeneration enters the adsorption preparation stage. The adsorption preparation is actually a process of boosting the bed layer pressure to the adsorption pressure. The control method of the booster valve in the boosting step is the same as that of the pressure reducing valve. To prevent the impact of rapid boosting on the molecular sieve bed layer, the boosting speed is adjusted through a boosting control valve to achieve the best protection effect on the adsorbent.

[0033] In the present invention, the pressure reduction step is the vacuum formed by the vacuum system within a certain period of time, which involves the vacuum system and the corresponding system heat exchanger. The pressure reduction step plays an important role in the entire desorption process. Since the regeneration effect of the molecular sieve bed layer will directly affect the product quality, the pressure reduction process is also one of the keys of this system.

[0034] During the entire pressure reduction process, the power provided by the system comes from the vacuum system. In the present invention, the reverse release tank, the vacuum heat exchanger group, and the vacuum pump provide the vacuum system required by the system.

[0035] The pumped ethanol-water mixture enters the weak wine tank after being cooled by the desorbed gas vacuum heat exchanger, and the non-condensable gas is evacuated through the vacuum pump. The weak wine in the weak wine tank is diluted and sent to the rectification column for regeneration treatment through a pump. The qualified gaseous alcohol obtained by rectification is mixed with the gas evaporated by the evaporator, then goes through superheating and adsorption for recycling.

[0036] The specific dehydration process is as follows:

[0037] S1. Ordinary alcohol (heated by the evaporator and superheater) passing through the rectification column enters the molecular sieve tower group. The regeneration gas first enters the reverse release tank 3 through the upper end of the molecular sieve tower group for the regeneration process, extracting part of the weak wine to reduce the load on the vacuum heat exchanger and the vacuum pump. After completion, the valve between the reverse release tank 3 and the molecular sieve tower group is closed, and the valve between the molecular sieve tower group and the vacuum heat exchanger is opened, so that the regeneration gas enters the vacuum heat exchanger.

[0038] S2. The material separated by dehydration and adsorption through the molecular sieve tower group forms fuel ethanol after heat exchange through the fuel ethanol heat exchanger 1.

[0039] S3. The colority of the fuel ethanol product formed in the initial stage of dehydration does not meet the standard. At this time, the non-compliant fuel ethanol flows back to the weak wine tank through the pipeline. The weak wine tank 5 replenishes the primary water and the cooling water of the vacuum heat exchanger through the vacuum pump, and is mixed with the fuel ethanol entering the weak wine tank 5 to dilute the alcohol content to 10%vol - 20%vol. Of course, when diluting the alcohol content, the cooling water of the vacuum heat exchanger and the primary water in the exhaust outlet pipeline of the vacuum pump can be selectively introduced into the weak wine tank for diluting the alcohol content.

[0040] S4. The diluted fuel ethanol enters the recovery tower through the weak wine tank 5 for subsequent rectification to further separate the molecular sieve powder in the fuel ethanol. The separated molecular sieve powder is discharged through the wastewater at the bottom of the recovery tower.

[0041] S5. When the colority of the fuel ethanol after the material in the molecular sieve tower group enters the fuel ethanol heat exchanger meets the requirements, it indicates that the decolorization treatment is completed. The valve between the fuel ethanol heat exchanger and the weak wine tank is closed, and subsequent normal production can be carried out.

[0042] The subsequent production of fuel ethanol in the present invention is the same as that in the existing fuel ethanol production system, and it is not the key point of protection of the present invention, so it will not be elaborated here.

[0043] There are still various specific implementation manners of the present invention. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims

1. A treatment method for a decolorization treatment system during the start-up and heating process of producing fuel ethanol, characterized in that: Among them, during the startup and heating process of producing fuel ethanol, the decolorization treatment system includes a molecular sieve tower group connected to a rectifying column. One end of the regeneration end of the molecular sieve tower group is connected to a reverse discharge tank, and the other end of the pipeline at the regeneration end of the molecular sieve tower group is connected to the feed end of a vacuum heat exchanger. The first outlet end of the vacuum heat exchanger is connected to a vacuum tank, one end of the vacuum tank is connected to a vacuum pump, and the outlet end of the exhaust pipeline of the vacuum pump is connected to a light wine tank; the inlet of the light wine tank is connected to the cooling water pipeline of the vacuum heat exchanger. The discharge end of the molecular sieve tower group is connected to a fuel ethanol heat exchanger and is refluxed through a switching valve. The treatment method includes the following steps: S1. The ordinary alcohol passing through the rectifying column is heated by an evaporator and a superheater and then enters the molecular sieve tower group. The regeneration gas enters the vacuum heat exchanger through the upper end of the molecular sieve tower group; S2. The material after dehydration and adsorption separation by the molecular sieve tower group forms fuel ethanol after heat exchange through the fuel ethanol heat exchanger; S3. The chromaticity of the fuel ethanol finished product formed in the initial stage of dehydration does not meet the standard. At this time, the non-compliant fuel ethanol is refluxed to the light wine tank through a pipeline. The light wine tank is supplemented with primary water and the cooling water of the vacuum heat exchanger through the exhaust pipe of the vacuum pump and is mixed with the fuel ethanol entering the light wine tank to dilute the alcohol content to 10%vol - 20%vol; S4. The diluted fuel ethanol enters the recovery tower through the light wine tank for subsequent rectification to further separate the molecular sieve powder in the fuel ethanol. The separated molecular sieve powder is discharged through the wastewater at the bottom of the recovery tower; S5. When the chromaticity of the fuel ethanol after the discharge from the molecular sieve tower group enters the fuel ethanol heat exchanger meets the requirements, it indicates that the decolorization treatment is completed. Close the valve between the fuel ethanol heat exchanger and the light wine tank and proceed with normal subsequent production.

2. The treatment method of the decolorization treatment system during the startup temperature rise process for producing fuel ethanol according to claim 1, characterized in that: One end of the light wine tank is also connected to a vacuum heat exchanger. The cooling water of the vacuum heat exchanger enters the light wine tank through a switching valve. The other end of the light wine tank is connected to the exhaust pipe of the vacuum pump to receive the light wine absorbed by the vacuum pump.

3. The processing method of a decolorization treatment system during the startup heating process for producing fuel ethanol as described in claim 2, characterized in that: The vacuum heat exchanger includes a first vacuum heat exchanger and a second vacuum heat exchanger connected to the first vacuum heat exchanger. One end of the second vacuum heat exchanger is connected to the vacuum tank.

4. The treatment method of the decolorization treatment system during the start-up and temperature rise process for producing fuel ethanol according to claim 3, characterized in that: The molecular sieve tower group includes three molecular sieve towers connected in parallel.

5. The treatment method of the decolorization treatment system during the start-up heating process of producing fuel ethanol according to claim 4, characterized in that: The reverse discharge tank is connected to the recovery tower through a reverse discharge pump group. The reverse discharge pump group is two reverse discharge pumps connected in parallel.

6. The treatment method of the decolorization treatment system during the start-up heating process of producing fuel ethanol as claimed in claim 5, wherein: The fuel ethanol reflux outlet end of the fuel ethanol heat exchanger is also connected to the light wine tank through a pipeline, and a valve is provided between the fuel ethanol reflux outlet end and the light wine tank.

7. The processing method of the decolorization treatment system during the start-up heating process of producing fuel ethanol according to claim 6, characterized in that: When diluting the alcohol content of the fuel ethanol in the light wine tank in S3, the cooling water in the vacuum heat exchanger and the primary water in the outlet exhaust pipe of the vacuum pump selectively enter the light wine tank for alcohol content dilution.

8. The treatment method of the decolorization treatment system during the start-up heating process of producing fuel ethanol as described in claim 7, wherein S1 includes the following steps: The ordinary alcohol passing through the rectifying column is heated by the evaporator and superheater and then enters the molecular sieve tower group. The regeneration gas first enters the reverse blow tank for the regeneration process to extract part of the light alcohol to reduce the load on the heat exchanger and vacuum pump. After completion, the valve between the reverse blow tank and the molecular sieve tower group is closed, and the valve between the molecular sieve tower group and the vacuum heat exchanger is opened, so that the regeneration gas enters the vacuum heat exchanger.

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