Deep dephosphorization method for illegal cooking oil and dephosphorization reagent thereof

Abstract

The invention discloses an illegal cooking oil deep dephosphorization method and a dephosphorization reagent thereof, and belongs to the field of waste oil pretreatment. The method comprises the following steps: firstly, carrying out preliminary acidification and dephosphorization on illegal cooking oil, then adsorbing residual colloid and pigment in grease by using a fixed activated clay bed or a fixed silica gel bed, finally adding a dephosphorization reagent, carrying out phosphorus element form transformation on the grease at 180-260 DEG C, cooling the grease, and washing with desalted water to obtain deeply dephosphorized grease. According to the method, deep dephosphorization can be carried out on the illegal cooking oil, the phosphorus content is reduced to 3 ppm or below, the technological process is simple, and the industrial operation cost is low.

Description

Technical Field

[0001] The invention belongs to the field of waste grease pretreatment, and particularly relates to a method for deep dephosphorization of waste cooking oil and a dephosphorization reagent thereof. Background Art

[0002] In the field of waste oil pretreatment, the existing conventional solutions include filtration and sedimentation, acidification treatment, alkaline washing treatment, water washing, centrifuge separation, activated clay adsorption, etc. The above conventional solutions have the following defects: (1) Bio-jet fuel hydrogenation units usually require that the phosphorus content of the feedstock oil is no more than 3ppm, so as to ensure the service life of the hydrogenation catalyst. The existing conventional pretreatment solutions can only treat oils with low phosphorus content and easy to dephosphorize, such as high-quality old cooking oil, frying oil, sewage oil, palmitic acid oil, etc., and conventional pretreatment methods can reduce the phosphorus content to below 3ppm. However, for relatively low-quality waste cooking oil, it is difficult to reduce the phosphorus content to below 3ppm with conventional pretreatment methods. (2) Using the existing pretreatment process, even if the material dosage of each process is increased, such as increasing the amount of acid, alkali, activated clay, water, or changing the reaction time and temperature, it is still impossible to treat relatively low-quality waste cooking oil. Deep dephosphorization of waste cooking oil is an industry problem. (3) The existing pretreatment process is relatively complex, the amount of activated clay is large, and the cost is relatively high. Summary of the Invention

[0003] The object of the present invention is to provide a method for deep dephosphorization of waste cooking oil and a dephosphorization reagent thereof, which can deeply dephosphorize waste cooking oil and reduce the phosphorus content to below 3 ppm, and has a simple process flow and low industrial operation cost.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for deep dephosphorization of waste cooking oil comprises the following steps: S1: Add citric acid or oxalic acid to waste cooking oil, stir thoroughly at 60-80°C for 5-20 minutes, and then use a centrifuge to separate the colloid to obtain oil; S2: At 100-120°C, the oil is passed through a fixed activated clay bed or a fixed silica gel bed to absorb the residual colloid and pigment in the oil; S3: Transfer the oil into the phosphorus conversion reactor, add the dephosphorization reagent, and react at 180-260°C for 5-20 minutes. The reactor can be an empty bed or filled with spherical molecular sieves with adsorption function. The molecular sieve is a molecular sieve with a large specific surface area, which is conducive to the conversion of phosphorus and the adsorption of colloids. The dephosphorization reagent is an acidic aqueous solution with a concentration of 10-30% formed by an acid and an oxide in a molar ratio of 1.2-2:1, wherein the acid is one or more of formic acid, acetic acid, propionic acid, butyric acid, and citric acid, and the oxide is one or two of iron oxide, copper oxide, zinc oxide, and calcium oxide; S4: After the oil is treated with the dephosphorization reagent, it is cooled to 70~95℃ and then washed with desalted water. The oil is dehydrated under negative pressure or normal pressure to obtain deeply dephosphorized waste cooking oil.

[0005] Furthermore, in step S1, the amount of citric acid or oxalic acid used is 0.1-0.3% of the weight of the waste cooking oil, and the citric acid or oxalic acid is prepared with water to form an acid solution with a concentration of 10-30% and then added to the waste cooking oil.

[0006] Furthermore, in step S1, the centrifuge speed is 2000-4000 r / min.

[0007] Furthermore, in step S2, the activated clay or silica gel is in the form of 20-60 mesh granules.

[0008] Furthermore, in step S4, the temperature of the desalted water is 60-95°C.

[0009] The present invention adopts the above technical solution, firstly performing preliminary acid degumming (dephosphorization) on waste cooking oil, then using a fixed activated clay bed or a fixed silica gel bed to adsorb residual colloid and pigment in the oil, and finally adding the dephosphorization reagent of the present invention to transform the phosphorus form of the oil at 180-260° C. in a reactor, cooling the oil and washing it with desalted water to obtain deeply dephosphorized oil.

[0010] The present invention has the following beneficial effects (1) Conventional pretreatment processes can only reduce the phosphorus content in waste cooking oil from 20-40 ppm to 10-18 ppm. However, the dephosphorization reagent and method of the present invention can reduce the phosphorus content of waste cooking oil to below 3 ppm.

[0011] (2) When using the existing conventional pretreatment process to treat waste cooking oil, even if the acid content is increased to 1%, the amount of activated clay added is increased to 5%, or the reaction temperature and reaction time are changed, the phosphorus content of the waste cooking oil can only be reduced to a minimum of 12 ppm.

[0012] (3) The process of the present invention simplifies the conventional pretreatment process, does not require alkali treatment, uses fixed-bed activated clay or silica gel adsorption method instead of conventional powdered clay adsorption, reduces the amount of activated clay from 2% to 0.2%, and reduces the pretreatment cost by about 20%.

[0013] (4) The present invention has a particularly good deep dephosphorization effect on waste cooking oil with a high phosphorus content. The pretreated waste cooking oil can be used as feedstock for bio-jet fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the process flow of the core section of the method for deep dephosphorization of waste cooking oil of the present invention. DETAILED DESCRIPTION

[0015] The waste oil of the present invention is conventional waste oil, which is usually taken out from the drains of restaurants or kitchen factories. It has many insoluble impurities, high acidity, and high phosphorus content. It is generally traded under the name of "waste oil" on the market. Waste oils with similar sources and properties can be treated using the method of the present invention.

[0016] The order of the various steps in the pretreatment process involved in the present invention is not fixed. It is entirely possible to achieve the same effect by changing the order of the core processes, such as placing the core process before pickling, or before activated clay adsorption, or before or after other processes. Example 1

[0017] A typical waste cooking oil sample purchased on the market was selected, and the phosphorus content of the waste cooking oil was determined to be 24.2 ppm using the molybdenum blue colorimetric method specified in the national standard GB / T 5537 "Determination of phospholipid content in grain and oil".

[0018] S1: Preheat the waste cooking oil to 80°C, add citric acid or oxalic acid (add water to make a 20% acid solution) at a concentration of 0.3% by weight of the waste cooking oil, fully stir and react for 20 minutes, use a 3500r / min centrifuge to separate the colloid, then add sodium hydroxide solution at a concentration of 0.1% by weight of the oil for alkali washing and centrifugal separation, then add desalted water at a concentration of 10% by weight of the oil for water washing, centrifuge to separate the aqueous phase, fully remove the water at a temperature of 110°C, add powdered activated clay at a concentration of 2% by weight of the oil for adsorption degumming, and centrifuge to obtain the oil.

[0019] After the treatment in step S1, the phosphorus content dropped to 16.8 ppm, and the dephosphorization rate was 30.6%.

[0020] S2: Add a dephosphorization reagent made of citric acid and zinc oxide in a molar ratio of 1.2:1 to the oil treated in step S1, add 0.2% of the weight of the oil and react at a constant temperature of 250°C for 10 minutes. After the oil sample is cooled, wash it with 75°C desalted water with a concentration of 10% of the weight of the oil. Centrifuge to separate the aqueous phase, and dry the water to obtain the cleaned gutter oil. The phosphorus content of the gutter oil is measured to be 3.0 ppm. Example 2

[0021] A typical waste cooking oil sample purchased on the market was selected, and the phosphorus content of the waste cooking oil was determined to be 24.2 ppm using the molybdenum blue colorimetric method specified in the national standard GB / T 5537 "Determination of phospholipid content in grain and oil".

[0022] S1: Same as Example 1, after treatment in step S1, the phosphorus content is reduced to 16.8 ppm.

[0023] S2: Add a dephosphorization reagent made of acetic acid and zinc oxide in a molar ratio of 1.2:1 to the oil treated in step S1, add 0.2% of the weight of the oil and keep the temperature at 250°C for 10 minutes. After the oil sample cools down, wash it with 65°C desalted water with a volume of 10% of the weight of the oil. Centrifuge and separate the aqueous phase. After drying, the cleaned gutter oil is obtained. The phosphorus content of the gutter oil is measured to be 2.8 ppm. Example 3

[0024] Typical waste cooking oil purchased on the market was used, and the phosphorus content was measured to be 37.7 ppm.

[0025] S1: Same as Example 1, after treatment in step S1, the phosphorus content is reduced to 16.6 ppm, and the dephosphorization rate is 56%.

[0026] S2: Add 0.2% of the weight of the oil and fat to the oil and fat treated in step S1 with a dephosphorization reagent (acetic acid and zinc oxide solution in a molar ratio of 1.2:1) and react at a constant temperature of 180°C for 10 minutes. After the oil sample cools down, add 10% of the weight of the oil and fat with 80°C desalted water for washing. After drying the water, deeply dephosphorized waste cooking oil is obtained, and the phosphorus content is measured to be 2.9ppm. Example 4

[0027] The waste oil in Example 1 was prepared as is. The mixture was first reacted at 80°C for 5 min with a citric acid aqueous solution containing 0.3% of the waste oil weight. The mixture was then washed with desalted water containing 10% of the oil weight. The mixture was centrifuged at 3500 r / min for water separation. After drying the water at 110°C, the mixture was subjected to dephosphorization by adsorption on a fixed granular activated clay bed. A dephosphorization reagent prepared by adding acetic acid and zinc oxide (mol ratio of 1.5:1) containing 0.2% of the oil weight was added to the grease. The mixture was kept at a constant temperature for 10 min at 220°C. After the oil sample was cooled, the mixture was washed with desalted water to obtain a highly dephosphorized waste oil. The phosphorus content of the oil was 3.0 ppm.

[0028] Comparative Example 1 A typical waste cooking oil sample purchased on the market was selected, and the phosphorus content of the waste cooking oil was determined to be 24.2 ppm using the molybdenum blue colorimetric method specified in the national standard GB / T 5537 "Determination of phospholipid content in grain and oil".

[0029] S1: Same as Example 1, after treatment in step S1, the phosphorus content is reduced to 16.6 ppm.

[0030] S2: Comparison: No dephosphorization reagent was added, 0.3% citric acid, 0.3% EDTA, 0.3% oxalic acid, 0.2% EDTA disodium salt and other reagents were added. After the oil sample was kept at a constant temperature of 250°C for 10 minutes, it was washed with 10% desalted water by weight of the oil after cooling. Clean waste oil was obtained, and its phosphorus content was reduced to 13.5ppm, 9.9ppm, 9.8ppm, 13.7ppm, and 8.9ppm respectively. Compared with Examples 1 to 4, no dephosphorization reagent was added or other reagents were added, which could not achieve the purpose of deep dephosphorization of waste oil.

Claims

1. A method for deep dephosphorization of waste cooking oil, characterized in that: The following steps are involved: S1: Add citric acid or oxalic acid to waste cooking oil, stir thoroughly at 60-80°C for 5-20 minutes, and then use a centrifuge to separate the colloid to obtain oil; S2: At 100-120°C, the oil is passed through a fixed activated clay bed or a fixed silica gel bed to absorb the residual colloid and pigment in the oil; S3: Add a dephosphorization reagent to the oil and react at 180-260°C for 5-20 minutes; the dephosphorization reagent is an acidic aqueous solution with a concentration of 10-30% formed by an acid and an oxide in a molar ratio of 1.2-2:1; S4: After the oil is treated with dephosphorization reagents, it is cooled to 70~95℃, washed with desalted water, and then dehydrated to obtain deeply dephosphorized waste cooking oil.

2. A method for deep dephosphorization of waste cooking oil according to claim 1, characterized in that: In step S3, the acid in the dephosphorization reagent is one or more of formic acid, acetic acid, propionic acid, butyric acid, and citric acid, and the oxide in the dephosphorization reagent is one or two of iron oxide, copper oxide, zinc oxide, and calcium oxide.

3. A method for deep dephosphorization of waste cooking oil according to claim 1, characterized in that: In step S1, the amount of citric acid or oxalic acid used is 0.1-0.3% of the weight of the waste cooking oil. Citric acid or oxalic acid is prepared with water to form an acid solution with a concentration of 10-30% and then added to the waste cooking oil.

4. A method for deep dephosphorization of waste cooking oil according to claim 1, characterized in that: In step S1, the centrifuge speed is 2000-4000 r / min.

5. A method for deep dephosphorization of waste cooking oil according to claim 1, characterized in that: In step S2, the activated clay or silica gel is in the form of 20-60 mesh granules.

6. A method for deep dephosphorization of waste cooking oil according to claim 1, characterized in that: In step S4, the temperature of the desalted water is 60-95°C.

7. A dephosphorization reagent, characterized in that: The dephosphorization reagent is an acidic aqueous solution with a concentration of 10-30% formed by an acid and an oxide in a molar ratio of 1.2-2:1, wherein the acid is one or more of formic acid, acetic acid, propionic acid, butyric acid, and citric acid, and the oxide is one or two of iron oxide, copper oxide, zinc oxide, and calcium oxide.

Images