CN115197779A

CN115197779A - Composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease

Info

Publication number: CN115197779A
Application number: CN202210720751.5A
Authority: CN
Inventors: 胡婷; 胡洋; 周竹君
Original assignee: Wuhan Zedian New Material Co ltd
Current assignee: Wuhan Zedian New Material Co ltd
Priority date: 2022-06-23
Filing date: 2022-06-23
Publication date: 2022-10-18

Abstract

The invention relates to the technical field of renewable resource recycling, grease processing and electric insulating materials, in particular to a composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease. The method comprises the following steps: preheating the kitchen waste grease to a first preset temperature, adding an adsorbent into the kitchen waste grease, and stirring; vacuumizing, turning on a UV light source to radiate the kitchen waste grease, simultaneously heating the preheated kitchen waste grease to a second preset temperature again, adding the adsorbent into the kitchen waste grease again, and stirring; and cooling the kitchen waste grease to a third preset temperature, turning off the UV light source, and filtering the kitchen waste grease in vacuum to obtain decolored kitchen waste grease. The method improves the decoloring effect of the adsorbent, oxidizes the pigment in the grease by combining heat energy and ultraviolet irradiation, destroys the structure of a chromophoric group to fade, has higher efficiency than the traditional physical decoloring method, is more effective to the dark grease, and has lower cost than the chemical decoloring method.

Description

Composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease

Technical Field

The invention relates to the technical field of renewable resource recycling, grease processing and electric insulating materials, in particular to a composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease.

Background

Insulating oil is an important insulating material in oil-filled electrical equipment as a liquid insulating medium, and mineral insulating oil is widely applied to oil-immersed and insulated high-voltage equipment due to good electrical insulating property, cooling performance and low cost. However, mineral insulating oil has a low ignition point, is difficult to meet the manufacturing requirements of electrical equipment with high fireproof performance, has poor biodegradability, pollutes surrounding soil and water sources once leakage occurs, and simultaneously, petroleum resources are in short supply. Under the influence of these factors, a new insulating oil which has great potential in oil source development, high ignition point and complete degradation needs to be found.

The existing research shows that the vegetable insulating oil has good electrical property, high ignition point and good biodegradation rate, meets the requirement of electrical equipment on fire resistance, and is a good environment-friendly liquid dielectric medium for replacing mineral insulating oil in the future. However, the refining of the vegetable insulating oil generally requires high-quality vegetable oil as a raw material, and if the vegetable insulating oil is produced in large quantities, shortage and price fluctuation of the edible oil are easily caused. The raw material cost is high, so that the cost of the refined insulating oil is high, and the application and popularization of the insulating oil are limited.

The kitchen waste oil refers to inedible oil with extremely poor quality, and also comprises waste oil after food is fried and fried for many times, and inedible oil generated after oil-containing waste water is separated by an oil-water separator or an oil separation tank, and belongs to the category of kitchen waste conceptually. The main component is triglyceride, which is usually a mixture of vegetable and animal oil, and has black brown appearance, pungent odor, and large amount of toxic and harmful substances. The kitchen waste grease contains triglyceride components similar to vegetable insulating oil, and if the kitchen waste grease can be properly treated for preparing the electric insulating oil, the selection space of insulating oil raw materials is increased, and the important significance on maintaining food safety is realized. Although the physical adsorption decoloration of the kitchen waste oil is simple and convenient, the decoloration effect of the deep-color kitchen waste oil is not ideal, the kitchen waste oil is subjected to a chemical oxidation method, the production cost is high, the pollution is large, the components of the kitchen waste oil are damaged, and the physical and chemical electrical characteristics of an insulating oil product are influenced.

In view of this, overcoming the drawbacks of the prior art is a problem to be solved urgently in the art.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention aims to provide a composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease, and aims to solve the technical problem that the conventional decoloring treatment in the prior art hardly meets the use requirement of the electric insulating oil.

In order to achieve the above object, according to one aspect of the present invention, the present invention provides a composite decoloring method for preparing electric insulating oil from deep color kitchen waste grease, the method comprising:

preheating the kitchen waste grease to a first preset temperature, adding an adsorbent into the kitchen waste grease, and stirring;

vacuumizing and turning on a UV light source to radiate the kitchen waste grease, simultaneously heating the preheated kitchen waste grease to a second preset temperature again, adding the adsorbent into the kitchen waste grease again and stirring;

and cooling the kitchen waste grease to a third preset temperature, turning off the UV light source, and performing vacuum oil filtration on the kitchen waste grease to obtain decolored kitchen waste grease.

Preferably, the first preset temperature is 85-95 ℃.

Preferably, the second preset temperature is 120 to 180 ℃.

Preferably, the third preset temperature is 60-80 ℃.

Preferably, the wavelength of the UV light source is 200-400 nm.

Preferably, the irradiation time of the UV light source is 60-120min.

Preferably, the addition amount of the adsorbent is 2-3% of the weight ratio of the kitchen waste grease each time.

Preferably, the adsorbent is one or more of activated clay, diatomite, activated carbon, bentonite, silica and alumina.

Preferably, when the oil is filtered in vacuum, the aperture of the filter screen is 0.5-10 μm.

Preferably, the number of times of vacuum oil filtering is at least two, and the mesh diameter of the filter screen is reduced from large to small.

The invention has the following beneficial effects:

the composite decoloring method adopted by the invention adopts two-step gradient adsorption decoloring, further improves the decoloring effect of the adsorbent compared with the traditional physical adsorption mode at the same temperature, and simultaneously utilizes the characteristics that the pigment can be oxidized at high temperature and has photosensitivity, and combines heat energy and ultraviolet irradiation to oxidize the pigment in the grease, so that the structure of the chromophoric group is destroyed into a colorless compound to be decolored. Compared with the traditional method for decoloring at the same temperature by only adopting an adsorbent, the composite decoloring method for preparing the electric insulating oil from the deep-color kitchen waste grease has better decoloring effect, higher decoloring efficiency and more effectiveness on the deep-color grease; meanwhile, compared with a chemical decoloring method, the method has the advantages of lower cost, better environmental protection and smaller influence on the electric performance of the insulating oil.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

Fig. 1 is a schematic flow chart of a composite decoloring method for preparing electric insulating oil from deep-color waste kitchen grease provided by an embodiment of the invention;

fig. 2 is a diagram illustrating a relationship between an ultraviolet band and a decoloring rate in a composite decoloring method for preparing electric insulating oil from deep-color waste kitchen grease according to an embodiment of the present invention;

fig. 3 is a graph showing the relationship between reaction time and decolorization rate in the composite decolorization method for preparing electric insulating oil from deep-color kitchen waste grease according to the embodiment of the present invention;

fig. 4 is a graph showing a relationship between a second preset temperature and a decoloring rate in the composite decoloring method for preparing electric insulating oil from deep-color waste kitchen grease according to the embodiment of the present invention;

fig. 5 is a graph showing a relationship between the amount of an adsorbent and a decoloring rate in a composite decoloring method for preparing electrical insulating oil from deep-color waste kitchen grease provided by an embodiment of the present invention;

fig. 6 is a photograph comparing the state of the grease prepared by the composite decoloring method for preparing the electric insulating oil from the deep-color kitchen waste grease according to the embodiment of the present invention with the initial state of the kitchen waste grease, the state of the kitchen waste grease after the conventional adsorption decoloring, and the state of the finished product oil of the vegetable insulating oil.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention. In addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the description of the present invention, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are for convenience only to describe the present invention without requiring the present invention to be necessarily constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In the present invention, unless expressly stated or limited otherwise, the recitation of a first feature "on" or "under" a second feature may include the recitation of the first and second features being in direct contact, and may also include the recitation that the first and second features are not in direct contact, but are in contact via another feature between them. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. "beneath," "under" and "beneath" a first feature includes the first feature being directly beneath and obliquely beneath the second feature, or simply indicating that the first feature is at a lesser elevation than the second feature.

At present, the conventional refining and decoloring process of the kitchen waste oil, in particular to the decoloring process of the electric insulating oil for preparing the electric insulating oil with the physicochemical electrical property meeting the requirements of the insulating oil, usually adopts a physical adsorption method for decoloring, and mainly adopts active (acidic) adsorbent and oil for mixing, adsorbing and decoloring for decoloring the oil, or adopts alkaline decolorant taking sodium bentonite as a raw material for mixing and decoloring, or adopts adsorption and decoloring in a decompression state. The above various adsorption decoloring methods have a certain decoloring effect, and the specific decoloring degree depends on the quality of the raw oil. The kitchen waste grease is complex in component, contains a large amount of colored fatty acid, pigment and oxidation products, impurities and moisture, and the kitchen waste grease collected by different channels is large in color depth and aging degree difference, most of the kitchen waste grease is dark in color and bad in performance. In actual treatment, the decolorization effect of the method is not ideal when the method is applied to preparing insulating oil from deep-color inferior kitchen waste grease, the insulating oil prepared from the kitchen waste grease is difficult to decolorize to be yellowish and transparent, and the general finished oil is dark and still reddish brown. While other grease decoloring processes such as a hydrogen peroxide and activated clay combined oxidation decoloring method, an acid oxidation hydrolysis method and other chemical decoloring methods have good decoloring effects, but cause the deterioration of the physicochemical and electrical properties of insulating oil, increase the cost of subsequent treatment, are not suitable for production and processing of electric insulating oil, and are mostly used for preparing products such as biodiesel and the like which have no requirements on the electrical insulating property of the products. The insulating oil with too dark color shows that a large amount of oil-soluble colored substances exist in the kitchen waste oil and fat to influence the physicochemical electrical performance and the oxidation stability of the kitchen waste oil and influence the visibility and the test judgment of the acid value of the transformer during application. Therefore, a method for decoloring electric insulating oil prepared from deep-color waste kitchen grease is urgently needed, and has very important practical significance for improving the market value and the application field of the electric insulating oil.

Example 1:

the technical problem to be solved in this embodiment is that it is difficult to meet the use requirements of the electrical insulating oil by the conventional decoloring treatment in the prior art. The kitchen waste grease is usually fried at high temperature or rancidity for a long time, not only has high acid value, but also is rich in a large amount of peptized impurities such as phospholipid, protein, pituitous substances, glycosyl diglyceride and the like, has high medium loss, and influences the technological effects of refining and deep processing; meanwhile, the kitchen waste oil is complex in component and contains a large amount of colored fatty acid, artificial or natural pigment, oxidation products and impurities with different colors and the like, the kitchen waste oil collected from different channels is large in color depth and aging degree difference, most of the kitchen waste oil is deep in color and poor in performance, the conventional physical decoloring method is not ideal in decoloring effect when being applied to deep-color inferior kitchen waste oil to prepare insulating oil, the insulating oil prepared from the kitchen waste oil is difficult to decolor to be yellowish and transparent, and the chemical decoloring method can cause large amount of damage to the kitchen waste oil component and influence the physicochemical electrical characteristics of a processed product.

The embodiment provides a composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease, which comprises the following steps as shown in fig. 1:

s101: preheating the kitchen waste grease to a first preset temperature, adding an adsorbent into the kitchen waste grease, and stirring.

In the first embodiment, the first preset temperature is set to 85 to 95 ℃, preferably 90 ℃. Firstly, the kitchen waste grease is pretreated at low temperature, and the adsorbent added for the first time can adsorb partial polar substances, so that the high-temperature photo-thermal decolorization is facilitated. The stirring speed is 40 r/min-80 r/min during preheating, is selected according to the size of the container and the viscosity degree, and can be uniformly stirred and dispersed without splashing.

S201: vacuumizing and opening a UV light source to radiate the kitchen waste grease, simultaneously heating the preheated kitchen waste grease again to a second preset temperature, and adding the adsorbent into the kitchen waste grease again and stirring.

In the first embodiment, the second preset temperature is set to 120-180 ℃, preferably 150 ℃. And (3) heating the preheated kitchen waste grease again to oxidize the pigment in the kitchen waste grease at a high temperature, and simultaneously destroying the pigment structure in the kitchen waste grease by using ultraviolet radiation light to ensure that the structure of a chromophoric group is destroyed into a colorless compound to fade. The first addition of the adsorbent is to pre-decolorize the grease, and part of pigments and polar substances are adsorbed, but the decolorizing effect is limited. When the adsorbent is added for the second time, the temperature of the grease is raised, and UV illumination radiation is applied, the fluidity of the grease becomes good, the molecular collision motion is enhanced, the decomposition of the pigment is facilitated, the physical and chemical activity of the reactant is improved, the adsorbent continuously adsorbs residual pigment on the one hand, and on the other hand, the adsorbent can adsorb the decomposition product of photo-thermal decoloration, so that the decoloration effect of the adsorbent is further improved compared with the traditional physical adsorption mode at the same temperature. The first addition of the adsorbent and the second addition of the adsorbent do not impair the reaction.

Also, since the second preset temperature is high, in order to prevent the grease from being oxidized by overheating, a vacuuming operation is performed. If the vacuum pumping is not carried out, the decoloring effect is not obvious, and the loss is large.

When the kitchen waste grease is heated, the stirring speed is 40 r/min-80 r/min, the stirring speed is selected according to the size of the container and the viscosity degree, and the kitchen waste grease can be uniformly stirred and dispersed without splashing.

S301: and cooling the kitchen waste grease to a third preset temperature, turning off the UV light source, and performing vacuum oil filtration on the kitchen waste grease to obtain decolored kitchen waste grease.

In the first embodiment, the third preset temperature is set to be 60 to 80 ℃, preferably 70 ℃. The higher the third preset temperature is, the faster the speed is during vacuum oil filtration. When filtering oil in vacuum, filtering oil in vacuum with the filtering precision of 5-10 microns for 2-3 times, and filtering oil in vacuum with the filtering precision of 0.5-2 microns for 1-2 times to finally obtain the decolored waste kitchen grease. When filtering oil in vacuum, the adsorbent is filtered out to improve the purity of the grease.

The composite decoloring method adopted in the embodiment adopts two-step gradient adsorption decoloring, compared with the traditional physical adsorption mode at the same temperature, the decoloring effect of the adsorbent is further improved, and meanwhile, the characteristics that the pigment can be oxidized at high temperature and is photosensitive are utilized, and the heat energy and ultraviolet irradiation are combined to oxidize the pigment in the grease, so that the structure of the chromophoric group is destroyed into a colorless compound to be decolored. Compared with the method for simply decoloring by adopting an adsorbent, the composite decoloring method for preparing the electric insulating oil from the deep-color kitchen waste grease provided by the embodiment has the advantages that the decoloring effect is better, the decoloring efficiency is higher, and the method is more effective for the deep-color grease; meanwhile, compared with a chemical decoloring method, the method has the advantages of lower cost, better environmental protection and smaller influence on the electric performance of the insulating oil.

In order to facilitate the high-temperature decolorization of the pigment in the trench, a preferred implementation scheme is also provided in combination with the embodiment of the invention, and specifically, the first preset temperature is 85-95 ℃. In this temperature range, the adsorbent can adsorb a part of pigments and impurities, which is beneficial to the efficiency of the subsequent decolorization, but some dark colors, especially red groups, are difficult to decolorize by the adsorbent.

In order to facilitate the high-temperature decolorization of the pigment in the waste kitchen oil, a preferred implementation scheme is also provided in combination with the embodiment of the invention, and specifically, the second preset temperature is 120-180 ℃. In this range, dark groups, especially red groups, decompose to colorless substances under the combined action of light and heat. If the second preset temperature is too high, energy waste is caused, and too much decoloring effect and efficiency cannot be improved; if the second preset temperature is too low, the decoloring effect and efficiency are not good.

In order to improve the purity of the decolored oil of the waste kitchen grease, a preferable implementation scheme is also provided in combination with the embodiment of the invention, and specifically, the third preset temperature is 60-80 ℃. In the temperature range, the kinematic viscosity of the decolored kitchen waste grease is high, if the third preset temperature is too low, the flowability of the decolored kitchen waste grease is poor, and the filtering effect and the efficiency are poor. If the third preset temperature is too high, energy is wasted, the heat-resisting requirements of equipment, pipelines, packing materials and the like are improved, and the service lives of the equipment and consumables are shortened.

In order to improve the decolorization rate of the waste kitchen grease, a preferable implementation scheme is provided in combination with the embodiment of the invention, and specifically, the wavelength of the UV light source is 200-400 nm.

The long chains are broken into shorter chains by the direct action of high-energy photons, thereby destroying the "backbone" of the molecule. The kitchen waste grease contains a large amount of colored fatty acid, artificial or natural pigment, oxidation products with different colors, impurities and the like. Most compounds in the kitchen waste grease can be within ultraviolet irradiation energy and have equivalent vibration frequency with covalent bonds, so that when the covalent bonds absorb ultraviolet irradiation with specific wavelength, the covalent bonds are broken to form a large number of charged free radicals with strong chemical activity, and the degradation of the compounds in the kitchen waste grease can be accelerated due to the existence of the free radicals. Therefore, ultraviolet irradiation oxidizes the pigment in the oil or fat, and the structure of the chromophoric group is broken into a colorless compound, thereby fading.

In order to improve the efficiency of the UV photothermal decolorization, a preferable implementation scheme is also provided in combination with the embodiment of the invention, and specifically, the irradiation time of the UV light source is 60-120min.

If the irradiation time of the UV light source is too short, the effect of destroying the chemical structure of the pigment cannot be achieved. If the irradiation time of the UV light source is too long, the fading amplitude is not changed significantly, and even the chromaticity of the grease is increased.

In order to improve the efficiency of adsorbing the pigment, a preferable implementation scheme is provided in combination with the embodiment of the present invention, and specifically, the addition amount of the adsorbent is 2 to 3% of the weight ratio of the kitchen waste oil.

If the addition amount of the adsorbent is too much, the adsorbent absorbs more oil after decolorization, which easily causes hydrolysis of oil, so that the acid value of the decolorized oil is increased, and the performance of the insulating oil in the aspect of electrochemistry is affected. If the addition amount of the adsorbent is too small, the decoloring rate of the grease is low, and the effect of decoloring the insulating oil cannot be achieved.

In order to improve the efficiency of adsorbing the pigments, polar substances and the decomposition products of photothermal bleaching, a preferred implementation scheme also exists in combination with the embodiment of the invention, and specifically, the adsorbent is one or more of activated clay, diatomite, activated carbon, bentonite, silica and alumina. Wherein, the activated clay has the best adsorption effect, and the adsorbent of one or more of diatomite, activated carbon, bentonite, silicon oxide and aluminum oxide has weaker effect than the activated clay.

In order to filter the adsorbent, a preferred implementation scheme also exists in combination with the embodiment of the invention, specifically, when the oil is filtered under vacuum, the pore diameter of the filter screen is 0.5 μm to 10 μm.

If the filtering precision of the vacuum oil filtering is too high, the filter screen is easy to block. And the oil flow rate is slow, affecting efficiency. If the filtering precision of the vacuum filtered oil is too low, the filtering effect of the adsorbent and part of impurities is poor, and the transparency and the electrical performance of the oil are influenced.

In order to improve the filtering effect of the adsorbent and the impurity filtering, in combination with the embodiment of the present invention, there is also a preferred implementation scheme, specifically, the number of times of vacuum oil filtering is at least two, and the mesh size of the filter screen is reduced from large to small.

In the first embodiment, during vacuum oil filtering, the filter screen with the larger aperture can be selected first for filtering, and then the filter screen with the smaller aperture can be selected for filtering continuously. In the first embodiment, 2 to 3 times of vacuum oil filtration with the filtration precision of 5 to 10 microns are selected, 1 to 2 times of vacuum oil filtration with the filtration precision of 5 to 2 microns are selected, and 1 to 2 times of vacuum oil filtration with the filtration precision of 0.5 to 2 microns are selected, so that the decolored kitchen waste grease is obtained. The more the filtration frequency is, the better the filtration effect of the adsorbent and part of impurities is, the less the filtration frequency is, and the weaker the filtration effect of the adsorbent and part of impurities is.

Example two:

on the basis of the first embodiment, the wavelength range of the radiation light source is controlled, 200-275nm, 275-320nm and 320-400nm are respectively selected to radiate the preheated kitchen waste grease, and the relationship result between the wave band of the radiation light source and the absorbance of the kitchen waste grease before and after decolorization is shown in fig. 2. In step S101, the kitchen waste oil is heated to 90 ℃, an adsorbent which is 2-3% of the oil weight is added, and the mixture is mixed and stirred for 30 minutes. In step S201, the radiation time is set to 90min, the second preset temperature is 150 ℃, the total of the additive amounts of the adsorbent in the previous and subsequent steps is 5% of the weight of the waste kitchen grease, and the adsorbent is activated clay.

The calculation method of the decolorization ratio comprises the following steps: the absorbance of the kitchen waste grease is measured by using an ultraviolet-visible spectrophotometry, plant insulating oil processed from soybean oil is used as a reference, the model is VS100, and the manufacturer is Wuhanze New electric Material Co. The decolorization ratio was calculated using the following formula (1):

in the formula: a. The ₀ Representing the absorbance of the kitchen waste grease; a represents the absorbance of the kitchen waste grease subjected to the composite decolorization method.

The preheated kitchen waste grease is added into a reaction container, under the irradiation of high temperature and UV lamp tubes, pigments in the kitchen waste grease are oxidized, decomposed and faded, but the oxidation loss of other components in the grease is increased due to excessive illumination, and meanwhile, the grease rancidity and peroxide value are increased due to the existence of excessive oxides in the grease, the adsorption efficiency of an adsorbent is influenced, so that the wave band of a radiation light source is controlled during the decoloration.

As can be seen from FIG. 2, when the wavelength band of the radiation source is in the UVC (200-275 nm) and UVB (275-320 nm), the decolorization rate can be maintained above 95%, and the decolorization rate of UVA (320-400 nm) in the wavelength band of the radiation source is greatly reduced compared with that of UVB. When the light speed is not changed, the shorter the wave band, the higher the light frequency, the higher the carried energy, and the stronger the decoloring capability to the pigment, so the damage effect of the radiation light source with the wave band of the light source exceeding the UVB to the pigment is lower than that of the light source below the UVB, and considering the economic benefit factor in the actual production, the shorter wave band UVC radiation light source needs more energy, therefore, the ultraviolet irradiation wave band is controlled to be the best UVB.

Example three:

on the basis of the first embodiment, the radiation time of the radiation light source is controlled, and 60min, 70min, 80min, 90min, 100min, 110min and 120min are respectively selected to radiate the preheated kitchen waste grease, and the result of the relationship between the radiation time and the absorbance of the kitchen waste grease before and after decolorization is shown in fig. 3. In step S101, the kitchen waste oil is heated to 90 ℃, an adsorbent which is 2-3% of the oil weight is added, and the mixture is mixed and stirred for 30 minutes. In step S201, UVB (275-320 nm) is selected as a radiation light source waveband, the second preset temperature is 150 ℃, an adsorbent is added, the sum of the addition amounts of the adsorbent in the previous and subsequent two times is 5% of the weight of the waste kitchen grease, and activated clay is selected as the adsorbent.

As can be seen from fig. 3, the decolorization rate gradually increases with the time increase within 60-90 min, the maximum decolorization rate is 95.43% within 90min, and the decolorization rate tends to be flat within the time range of 90-120 min. Within a certain time range, the decolorization degree is improved along with the increase of the radiation time, but the radiation time is excessively prolonged, so that the decolorization amplitude is not obviously changed, and even the chromaticity of the grease is possibly increased, and the radiation time is judged to be most suitable to be 90min.

Example four:

on the basis of the first embodiment, the second preset temperature is controlled, the preheated kitchen waste oil is reacted at the reaction temperatures of 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃ and 190 ℃, and the result of the relationship between the temperature during radiation and the absorbance of the kitchen waste oil before and after decolorization is shown in fig. 4. In step S101, the kitchen waste oil is heated to 90 ℃, an adsorbent which is 2-3% of the oil weight is added, and the mixture is mixed and stirred for 30 minutes. In step S201, UVB (275-320 nm) is selected as a radiation light source wave band, then an adsorbent is added, the sum of the addition amount of the adsorbent in the previous and later two times is 5% of the weight of the waste kitchen oil, the adsorbent is activated clay, and the radiation time is 90min.

The stability of the molecular structure of the pigment is reduced at high temperature, which is beneficial to the destruction of the pigment structure by the radiation light to achieve the fading effect, as can be seen from fig. 4, the fading rate is increased along with the increase of the temperature, but when the temperature exceeds 150 ℃, the fading rate is slowly increased. In addition, the grease can be thermally aged after being contacted with oxygen for a long time in a high-temperature environment, so that the peroxide value is increased to produce a new pigment, and the grease is discolored. Considering the problems of energy consumption and cost, the reaction temperature is most suitably selected to be 150 ℃ during light irradiation.

Example five:

on the basis of the first embodiment, the addition amount of the adsorbent is controlled, and the total addition amount of the adsorbent in the two previous and next times is respectively 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5% and 7%. The result of the relationship between the addition of the adsorbent and the absorbance of the kitchen waste grease before and after decolorization is shown in fig. 5. In step S101, the kitchen waste oil is heated to 90 ℃, and mixed and stirred for 30 minutes. In step S201, UVB (275-320 nm) is selected as a radiation light source wave band, then an adsorbent is added, activated clay is selected as the adsorbent, and the radiation time is selected for 90min.

As can be seen from fig. 5, when the amount of the adsorbent is 3% to 5%, the decolorization rate rapidly increases with the continuous addition of the activated clay, and when the weight of the activated clay is 5% of the weight of the oil, the decolorization rate reaches a peak value of 95.43%, and then the conversion rate tends to be stable, since the activated clay has oil absorption, the decolorized clay absorbs more oil, and the higher activity of the activated clay easily causes a small amount of hydrolysis of the oil when the activated clay is in long-term contact with the oil, so that the acid value of the oil after decolorization increases, it can be determined that the total amount of the activated clay is selected to be optimal to be 5%.

Example six:

in order to further improve the decolorization efficiency of the kitchen waste oil and find out factors influencing the decolorization of the kitchen waste oil, an orthogonal experiment is designed to obtain the influence degree of each factor in the composite decolorization method on the decolorization rate, as shown in table 1. The cross-experimental range analysis of the oil sample decolorization ratio is shown in table 2.

Table 1 orthogonal experimental results of the kitchen waste grease decoloring process

TABLE 2 pole difference analysis of the oil sample decolorization ratio in an orthogonal experiment

As can be seen from Table 2, the influence degrees of the composite decolorization are as follows in sequence from large to small: reaction temperature, adsorbent dosage, radiation time and radiation optical band during radiation. In conclusion, when the wave band UVB of the radiation light source of the kitchen waste oil is radiated, the reaction temperature is 150 ℃, the radiation time is 90min, and the subsequent adsorbent dosage is 5% of the oil weight, the decolorization degree can reach the best, and the result is identical with the conclusion obtained by a single-factor experiment.

As shown in fig. 6, (a) shows an initial state of the kitchen waste oil, (b) shows a state of the kitchen waste oil after conventional adsorption decoloration, (c) shows a state of the kitchen waste oil after decoloration by the method of the first embodiment, and (d) shows a state of a product oil of VS100 vegetable insulating oil. The initial state of the kitchen waste grease is black brown, contains precipitates and suspended matters, and has poor appearance. The kitchen waste grease subjected to traditional adsorption decoloration has no precipitate or suspended matter, but is still darker than the color of finished oil, and the kitchen waste grease subjected to composite decoloration has a remarkable decoloration effect and is close to VS100 plant insulating oil in color.

The traditional decoloring method of adsorption decoloring is to add activated clay at 80-90 ℃ 5% each time, stir for 60min, filter and repeat the decoloring process for 2 times. The decolorization rate is less than 50%, part of pigment groups are difficult to be adsorbed, and the oil sample obtained by multiple times of adsorption decolorization still has a reddish appearance.

The decolorizing method of the composite decolorizing method comprises adding activated clay 3% at 80-90 deg.C, stirring for 30min; heating the oil sample to 150 ℃, adding activated clay 2% again, radiating the oil sample by using a UV radiation waveband of 275-320nm, performing composite adsorption and decoloration for 90min, and performing vacuum filtration. The appearance of the finally obtained oil sample is similar to that of the finished oil, and the finally obtained oil sample is light yellow, clear and transparent.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease is characterized by comprising the following steps:

2. The composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease according to claim 1, wherein the first preset temperature is 85-95 ℃.

3. The composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease according to claim 1, wherein the second preset temperature is 120-180 ℃.

4. The composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease according to claim 1, wherein the third preset temperature is 60-80 ℃.

5. The composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease according to claim 1, wherein the wavelength of the UV light source is 200-400 nm.

6. The composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease according to claim 1, wherein the irradiation time of the UV light source is 60-120min.

7. The compound decoloring method for preparing the electric insulating oil from the dark-colored kitchen waste grease according to claim 1, wherein the addition amount of the adsorbent is 2-3% of the weight ratio of the kitchen waste grease each time.

8. The composite decoloring method for preparing electric insulating oil from deep-color kitchen waste grease according to claim 1, wherein the adsorbent is one or more of activated clay, diatomite, activated carbon, bentonite, silica and alumina.

9. The composite decoloring method for preparing electric insulating oil from dark kitchen waste grease according to claim 1, wherein the aperture of the filter screen is 0.5-10 μm during vacuum oil filtering.

10. The composite decoloring method for preparing electric insulating oil from dark kitchen waste grease according to claim 9, wherein the number of times of vacuum oil filtering is at least two, and the mesh diameter of the filter screen is reduced from large to small.