Method for treating acid water in waste oil biodiesel production

Abstract

The application provides a treatment method of waste oil and fat biodiesel acid water, and the method can separate waste sulfuric acid, methanol and organic impurities in the biodiesel acid water and recycle the waste sulfuric acid after concentration, avoids pollution caused by direct discharge of the biodiesel acid water to the environment, realizes recycling of the sulfuric acid, and greatly reduces the chemical oxygen demand (COD) of the biodiesel acid water, effectively reduces the difficulty of waste water treatment, and saves the production cost of enterprises.

Description

Technical Field

[0001] This invention relates to the field of biodiesel preparation technology, and more particularly to a method for treating acidic water in the production of biodiesel from waste oil. Background Technology

[0002] Biodiesel is a typical "green energy" source, characterized by good environmental performance, good engine starting performance, good fuel performance, and a wide range of renewable raw material sources. Vigorously developing biodiesel is of significant strategic importance for sustainable economic development, promoting energy substitution, reducing environmental pressure, and controlling urban air pollution. Biodiesel is primarily a fatty acid ester produced through the alcoholysis of renewable resources (cellulose, waste cooking oil, straw, vegetable oil, etc.). Its main components are lower alcohol esters of higher fatty acids, namely ester compounds formed by long-chain saturated or unsaturated fatty acids such as palmitic acid, stearic acid, oleic acid, and linoleic acid with alcohols such as methanol or ethanol.

[0003] Given my country's national conditions and the characteristics of its oil resources, biodiesel production enterprises generally use waste oils (gutter oil, acidified oil, etc.) to produce biodiesel. When producing biodiesel from waste oils, sulfuric acid is generally used as a catalyst. The biodiesel acid water produced in the process contains a large amount of waste sulfuric acid and organic impurities. If this biodiesel acid water is discharged directly, it will not only cause serious environmental pollution, but also increase the difficulty of wastewater treatment due to the high chemical oxygen demand (COD) in the biodiesel acid water, thereby increasing the production costs of enterprises. Summary of the Invention

[0004] This invention discloses a method for treating acidic wastewater from waste oil-to-biodiesel production. This method solves the problem that in the traditional waste oil-to-biodiesel production process, sulfuric acid is used as a catalyst, and the resulting acidic wastewater contains a large amount of waste sulfuric acid and organic impurities. Direct discharge of this acidic wastewater not only causes serious environmental pollution, but also increases the difficulty of wastewater treatment due to its high chemical oxygen demand (COD), thereby increasing the production costs for enterprises.

[0005] To solve the above-mentioned technical problems, the present invention specifically adopts the following technical solution:

[0006] A method for treating acidic water in the production of biodiesel from waste oil includes the following steps:

[0007] Step 1, methanol removal: Pump the biodiesel acid water into a reactor equipped with a condenser, heat the reactor to remove methanol under vacuum, adjust the condenser to full reflux before distillation, then adjust the reflux ratio of the condenser to collect methanol, sample and analyze the acid water during distillation, and end distillation when the methanol content in the acid water is found to be below 5‰.

[0008] Step 2, coarse filtration: The acid water after methanol removal in Step 1 is filtered through a mesh filter to remove coarse impurities. The mesh size of the filter is 80-100 mesh.

[0009] Step 3, Dehydration: The acid water after coarse filtration in Step 2 is pumped into the reaction vessel for vacuum dehydration, so that the water content in the dehydrated acid water is below 5‰ and the sulfuric acid concentration in the acid water is 55%-60%. The dehydrated water enters the sewage treatment plant.

[0010] Step 4, fine filtration: The acid water after dehydration in step 3 is filtered out by a bag filter to remove fine impurities. The mesh size of the filter screen is 120-150 mesh.

[0011] Step 5, Concentration: The acid water filtered in Step 4 is pumped into the reaction vessel for concentration, so that the sulfuric acid concentration in the acid water reaches more than 85%.

[0012] Step 6, Filtration: Pump the concentrated acid water from Step 5 into a plate and frame filter to remove fine impurities from the acid water. The filter screen has a mesh size of 200-250. After filtration, concentrated sulfuric acid with a concentration of over 85% can be obtained and reused in the biodiesel production workshop.

[0013] Furthermore, the acidic filter residue produced after filtering the acidic water in steps two, four, and six is ​​washed with methanol removed in step one until it becomes neutral. The resulting neutral filter residue is burned as biomass fuel, while the acidic methanol is reused in the biodiesel production workshop.

[0014] Furthermore, during the methanol removal process of the biodiesel acid water in step one, the temperature is set to 75-90℃ and the vacuum degree is set to 3×10⁻⁶. 4 -7×10 4 Pa, the condenser reflux time is set to 5-10 min, the reflux ratio of the condenser is set to 5:2 when collecting the fore fraction, and the holding time is set to 0.5-1 hour.

[0015] Furthermore, the filter screen of the mesh filter in step two is made of polypropylene, the bag filter in step four is made of polypropylene, and the plate and frame filter in step six is ​​made of polypropylene.

[0016] Furthermore, before the water removed in step three enters the wastewater treatment plant, the chemical oxygen demand (COD) in the removed water is measured to be 200-250 mg / L.

[0017] Furthermore, during the dehydration of the coarsely filtered acidic water in step three, the temperature is set to 100-120℃ and the vacuum degree is set to 4×10⁻⁶. 3 -6×10 3 Pa, the duration is set to 1-2 hours.

[0018] Furthermore, when concentrating the filtered acidic water in step five, the temperature is set to 140-150℃ and the vacuum degree is set to 2×10⁻⁶. 3 -3×10 3 Pa, the duration is set to 1-2 hours.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention separates all waste sulfuric acid, methanol, and organic impurities from biodiesel acid water, concentrates the waste sulfuric acid, and then recycles it, thus avoiding the pollution caused by direct discharge of biodiesel acid water and realizing the recycling of sulfuric acid. At the same time, only the dehydration stage generates wastewater in the entire process, which can greatly reduce the chemical oxygen demand (COD) of biodiesel acid water, effectively reduce the difficulty of wastewater treatment, and thus save production costs for enterprises.

[0021] 2. In this invention, inexpensive and convenient reaction vessels are used for methanol and water removal and sulfuric acid concentration. The process is simple and convenient, and the selected equipment is more suitable for industrial enterprises, which also saves the production costs of enterprises.

[0022] 3. In this invention, the acidic filter residue produced after filtering acidic water is washed with methanol after removal until it becomes neutral, and the resulting neutral filter residue is used as biomass fuel for combustion. This method makes the entire process more environmentally friendly. At the same time, the acidic methanol obtained from washing can also be recycled in the biodiesel production workshop, which effectively improves the utilization rate of resources. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0025] Example 1

[0026] This embodiment provides a method for treating acidic water in the production of biodiesel from waste oil, the method comprising the following steps:

[0027] In this embodiment, the chemical oxygen demand (COD) of the untreated biodiesel acid water was measured to be 20,000 mg / L.

[0028] (1) Methanol removal: Biodiesel acid water is pumped into a reactor equipped with a condenser, and the reactor is heated to perform vacuum methanol removal. The vacuum degree is set to 3×10⁻⁶. 4Pa, temperature set to 75℃, before distillation, the condenser was adjusted to perform total reflux, the total reflux time was set to 5min, then the reflux ratio of the condenser was adjusted to 5:2 and methanol was collected for later use. During the distillation process, the acid water was sampled and analyzed. When the methanol content in the acid water was measured to be 5‰, the methanol distillation was stopped, and the water content in the distilled methanol was measured to be 10%.

[0029] (2) Coarse filtration: The acid water after methanol removal is filtered through a mesh filter to remove coarse impurities. The mesh filter is made of polypropylene and has a mesh size of 80. After filtration, the acidic filter residue is collected.

[0030] (3) Dehydration: The coarsely filtered acid water is pumped into the reactor for vacuum dehydration. The temperature is set to 100℃ and the vacuum degree is set to 4×10⁻⁶. 3 Pa, the maintenance time was set to 1 hour, the water content of the acid water after removal was measured to be 5‰, and the sulfuric acid concentration in the acid water was measured to be 55% by acid-base titration. The chemical oxygen demand (COD) of the removed water was measured to be 200 mg / L and then entered the sewage treatment plant for treatment.

[0031] (4) Fine filtration: The dehydrated acid water is filtered through a bag filter to remove fine impurities. The bag filter is made of polypropylene and the filter screen has a mesh size of 120. After filtration, the acidic filter residue is collected.

[0032] (5) Concentration: The finely filtered acid water is pumped into a reaction vessel for concentration. The temperature is set to 140℃ and the vacuum degree is set to 2×10⁻⁶. 3 Pa, with the holding time set to 1 hour, the concentration of sulfuric acid in the acidic water was determined to be 85% by acid-base titration.

[0033] (6) Pressure filtration: The concentrated acid water from step five is pumped into a plate and frame filter to remove fine impurities from the acid water. The plate and frame filter is made of polypropylene and the filter screen has a mesh size of 200. The filtered concentrated sulfuric acid is then reused in the biodiesel production workshop, and acidic filter residue is collected at the same time.

[0034] (7) The acidic filter residue produced after three filtrations of acidic water is washed with methanol to neutrality. The resulting neutral filter residue is burned as biomass fuel, and the acidic methanol is reused in the biodiesel production workshop.

[0035] Example 2

[0036] This embodiment provides a method for treating acidic water in the production of biodiesel from waste oil, the method comprising the following steps:

[0037] In this embodiment, the chemical oxygen demand (COD) of the biodiesel acid water before treatment was measured to be 25000 mg / L.

[0038] (1) Methanol removal: Biodiesel acid water is pumped into a reactor equipped with a condenser, and the reactor is heated to perform vacuum methanol removal. The vacuum level is set to 7×10⁻⁶. 4 Pa, temperature set to 90℃, before distillation, the condenser was adjusted to perform total reflux, the total reflux time was set to 10min, then the reflux ratio of the condenser was adjusted to 5:2 and methanol was collected for later use. During the distillation process, the acid water was sampled and analyzed. When the methanol content in the acid water was measured to be 3‰, the methanol distillation was stopped, and the water content in the distilled methanol was measured to be 5%.

[0039] (2) Coarse filtration: The acid water after methanol removal is filtered through a mesh filter to remove coarse impurities. The mesh filter is made of polypropylene and has a mesh size of 100. After filtration, the acidic filter residue is collected.

[0040] (3) Dehydration: The coarsely filtered acid water is pumped into the reactor for vacuum dehydration. The temperature is set to 120℃ and the vacuum degree is set to 6×10⁻⁶. 3 Pa, the maintenance time was set to 2 hours, the water content of the acid water after removal was measured to be 3‰, and the sulfuric acid concentration in the acid water was measured to be 60% by acid-base titration. The chemical oxygen demand (COD) of the removed water was measured to be 250 mg / L and then entered the sewage treatment plant for treatment.

[0041] (4) Fine filtration: The dehydrated acid water is filtered through a bag filter to remove fine impurities. The bag filter is made of polypropylene and the mesh size is 150. After filtration, the acidic filter residue is collected.

[0042] (5) Concentration: The finely filtered acid water is pumped into a reaction vessel for concentration. The temperature is set to 150℃ and the vacuum degree is set to 3×10. 3 Pa, the holding time was set to 2 hours, and the concentration of sulfuric acid in the acid water was determined to be 90% by acid-base titration.

[0043] (6) Pressure filtration: The concentrated acid water from step five is pumped into a plate and frame filter to remove fine impurities from the acid water. The plate and frame filter is made of polypropylene and the filter screen has a mesh size of 250. The filtered concentrated sulfuric acid is then reused in the biodiesel production workshop, and acidic filter residue is collected at the same time.

[0044] (7) The acidic filter residue produced after three filtrations of acidic water is washed with methanol to neutrality. The resulting neutral filter residue is burned as biomass fuel, and the acidic methanol is reused in the biodiesel production workshop.

[0045] Example 3

[0046] This embodiment provides a method for treating acidic water in the production of biodiesel from waste oil, the method comprising the following steps:

[0047] In this embodiment, the chemical oxygen demand (COD) of the biodiesel acid water before treatment was measured to be 22500 mg / L.

[0048] (1) Methanol Removal: Biodiesel acid water is pumped into a reactor equipped with a condenser. The reactor is heated to perform vacuum methanol removal, with the vacuum level set to 5×10⁻⁶. 4 Pa, temperature set to 80℃, before distillation, the condenser was adjusted to perform total reflux, the total reflux time was set to 8min, then the reflux ratio of the condenser was adjusted to 5:2 and methanol was collected for later use. During the distillation process, the acid water was sampled and analyzed. When the methanol content in the acid water was measured to be 4‰, the methanol distillation was stopped, and the water content in the distilled methanol was measured to be 8%.

[0049] (2) Coarse filtration: The acid water after methanol removal is filtered through a mesh filter to remove coarse impurities. The mesh filter is made of polypropylene and has a mesh size of 90. After filtration, the acidic filter residue is collected.

[0050] (3) Dehydration: The coarsely filtered acid water is pumped into the reactor for vacuum dehydration. The temperature is set to 110℃ and the vacuum degree is set to 5×10⁻⁶. 3 Pa, the maintenance time was set to 1.5 hours, the water content of the acid water after removal was measured to be 4‰, and the sulfuric acid concentration in the acid water was measured to be 57% by acid-base titration. The chemical oxygen demand (COD) of the removed water was measured to be 225 mg / L and then entered the sewage treatment plant for treatment.

[0051] (4) Fine filtration: The dehydrated acid water is filtered through a bag filter to remove fine impurities. The bag filter is made of polypropylene and the mesh size is 140 mesh. After filtration, the acidic filter residue is collected.

[0052] (5) Concentration: The finely filtered acid water is pumped into a reaction vessel for concentration. The temperature is set to 145℃ and the vacuum degree is set to 3×10. 3 Pa, the holding time was set to 1.5 hours, and the concentration of sulfuric acid in the acid water was determined to be 88% by acid-base titration.

[0053] (6) Pressure filtration: The concentrated acid water from step five is pumped into a plate and frame filter to remove fine impurities from the acid water. The plate and frame filter is made of polypropylene and the mesh size of the filter screen is 220 mesh. The filtered concentrated sulfuric acid is reused in the biodiesel production workshop, and acidic filter residue is collected at the same time.

[0054] (7) The acidic filter residue produced after three filtrations of acidic water is washed with methanol to neutrality. The resulting neutral filter residue is burned as biomass fuel, and the acidic methanol is reused in the biodiesel production workshop.

[0055] In summary, this invention can completely separate waste sulfuric acid, methanol, and organic impurities from biodiesel acid water, concentrate the waste sulfuric acid, and recycle it, avoiding the pollution caused by direct discharge of biodiesel acid water and realizing the recycling and reuse of sulfuric acid. The entire process only generates wastewater during the dehydration stage, which can greatly reduce the chemical oxygen demand (COD) of biodiesel acid water, effectively reducing the difficulty of wastewater treatment and thus saving production costs for enterprises. Furthermore, this invention uses a method of washing the acidic filter residue produced after acid water filtration with methanol to neutrality, and then using the resulting neutral filter residue as biomass fuel for combustion, making the entire process more environmentally friendly. Simultaneously, the acidic methanol obtained from washing can also be recycled in the biodiesel production workshop, effectively improving resource utilization.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for treating acidic water in the production of biodiesel from waste oil, characterized in that: The method includes the following steps; Step 1, methanol removal: Pump the biodiesel acid water into a reactor equipped with a condenser, heat the reactor to remove methanol under vacuum, adjust the condenser to full reflux before distillation, then adjust the reflux ratio of the condenser to collect methanol, sample and analyze the acid water during distillation, and end distillation when the methanol content in the acid water is found to be below 5‰. Step 2, coarse filtration: The acid water after methanol removal in Step 1 is filtered through a mesh filter to remove coarse impurities. The mesh size of the filter is 80-100 mesh. Step 3, Dehydration: The acid water after coarse filtration in Step 2 is pumped into the reaction vessel for vacuum dehydration, so that the water content in the dehydrated acid water is below 5‰ and the sulfuric acid concentration in the acid water is 55%-60%. The dehydrated water enters the sewage treatment plant. Step 4, fine filtration: The acid water after dehydration in step 3 is filtered out by a bag filter to remove fine impurities. The mesh size of the filter screen is 120-150 mesh. Step 5, Concentration: Pump the filtered acid water from Step 4 into the reaction vessel for concentration, so that the sulfuric acid concentration in the acid water reaches more than 85%. Step 6, pressure filtration: Pump the concentrated acid water from step 5 into a plate and frame filter to remove fine impurities from the acid water. The mesh size of the filter screen is 200-250 mesh. After filtration, concentrated sulfuric acid with a concentration of over 85% can be obtained and reused in the biodiesel production workshop. The acidic filter residue produced after filtering the acidic water in steps two, four and six is ​​washed with the methanol removed in step one until it becomes neutral. The resulting neutral filter residue is burned as biomass fuel, and the acidic methanol is reused in the biodiesel production workshop. In step one, when removing methanol from the biodiesel acid water, the temperature is set to 75-90℃ and the vacuum degree is set to 3×10⁻⁶. 4 -7×10 4 Pa, the condenser reflux time is set to 5-10 min, the reflux ratio of the condenser is set to 5:2 when collecting the fore fraction, and the holding time is set to 0.5-1 hour.

2. The method for treating acidic water in waste oil-to-biodiesel production according to claim 1, characterized in that: The filter screen of the mesh filter mentioned in step two is made of polypropylene, the bag filter in step four is made of polypropylene, and the plate and frame filter in step six is ​​made of polypropylene.

3. The method for treating acidic water in waste oil-to-biodiesel production according to claim 1, characterized in that: Before the water removed in step three enters the sewage treatment plant, the chemical oxygen demand (COD) in the removed water is measured to be 200-250 mg / L.

4. The method for treating acidic water in waste oil-to-biodiesel production according to claim 1, characterized in that: In step three, when dehydrating the coarsely filtered acidic water, the temperature is set to 100-120℃ and the vacuum degree is set to 4×10⁻⁶. 3 -6×10 3 Pa, the duration is set to 1-2 hours.

5. The method for treating acidic water in waste oil-to-biodiesel production according to claim 1, characterized in that: When concentrating the filtered acidic water in step five, the temperature is set to 140-150℃ and the vacuum degree is set to 2×10⁻⁶. 3 -3×10 3 Pa, the duration is set to 1-2 hours.

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