Production and processing technology of low-temperature crystallized oleic acid

Abstract

The invention relates to the technical field of oleic acid production and processing, in particular to a low-temperature crystallized oleic acid production and processing technology which comprises the following steps: pumping fractionated fatty acid into a crystal melting tank from a raw material tank, heating, feeding into a crystallization kettle, and keeping the temperature stable; cooling by stages, and controlling the cooling rate in the cooling process of each stage to obtain crystal slurry; and performing water pressure squeezing on the obtained crystal slurry in a nitrogen atmosphere to obtain oleic acid. According to the method, the separation effect of high-melting-point fatty acid in the cooling crystallization stage in the oleic acid production process is accurately evaluated, and the cooling rate in the low-temperature crystallization stage in the crystallization filter-press method oleic acid production process is adjusted; crystal slurry obtained in the low-temperature crystallization stage contains excessive saturated fatty acid.

Description

Technical Field

[0001] The present application relates to the technical field of oleic acid production and processing, and specifically to a production and processing technology of low-temperature crystallized oleic acid. Background Art

[0002] Oleic acid is a monounsaturated omega-9 fatty acid that exists naturally in animal and vegetable oils in the form of glycerides. High-purity oleic acid is an important fine chemical product, widely used in paints and inks, coatings, mineral flotation agents, film antistatic agents, lubricants, textile auxiliaries, explosive emulsifiers, etc. Due to the increasingly fierce market competition and the increasing attention paid to environmental protection issues, the current production processes of oleic acid are mainly freeze pressing, crystallization filter pressing and distillation.

[0003] The crystallization filter press method is used to produce oleic acid, which has low production costs and high oleic acid quality. Since it does not involve chemical reactions, it is an environmentally friendly process and can achieve large-scale industrial production. However, in the process of producing oleic acid by the crystallization filter press method, liquid fatty acids are easily mixed in the crystal slurry, reducing the yield of the product. However, the existing technology is difficult to accurately evaluate the separation effect of high-melting-point fatty acids in the cooling and crystallization stage during the crystallization filter press method to produce oleic acid, which may increase the degree of inclusion of liquid fatty acids in the filter cake, and thus cannot provide scientific data support for the control and adjustment of the oleic acid crystallization filter press process. Summary of the invention

[0004] In view of the above, it is necessary to provide a production and processing technology of low-temperature crystallized oleic acid to solve the above problems.

[0005] One embodiment of the present application provides a production and processing process of low-temperature crystallized oleic acid, the process comprising: S1: pumping fractionated fatty acids from the raw material tank into the crystal melting tank; S2: heating the fractionated fatty acid in the crystal melting tank and sending it into the crystallization kettle to maintain a stable temperature; S3: Cooling in stages, controlling the cooling rate in each stage to obtain a crystal slurry; wherein the specific steps of controlling the cooling rate are: S301: using the hyperspectral image of the fatty acid solution at each moment as the low-temperature crystallization image at each moment, and using principal component analysis to obtain several characteristic bands of the low-temperature crystallization image; S302: obtaining a crystal reflectivity factor of each pixel according to the difference in reflectivity between each pixel of the low-temperature crystallization image at each moment and the pixels in the local range on the same characteristic band; taking a preset number of pixels as crystal pixels based on the crystal reflectivity factor, and using a regional growing algorithm to obtain all crystallization regions; S303: according to the difference between the reflectivity characteristic factors of the crystallization pixels in each crystallization area and the other pixels in each characteristic band of the low-temperature crystallization image at each moment, combined with the difference in pixel distribution and reflectivity distribution between each crystallization area and the other crystallization areas, the crystallization sufficiency of the low-temperature crystallization image at each moment is obtained; S304: taking a preset time length as a crystallization interval; determining a crystallization separation factor according to the distribution of all low-temperature crystallization images and the distribution of the crystallization sufficiency in each crystallization interval, and controlling the cooling rate; S4: hydraulically pressing the obtained crystal slurry under a nitrogen atmosphere to obtain oleic acid.

[0006] The fractionated fatty acid in S1 is a fatty acid obtained by fractionation of PFAD or a purchased fatty acid, and satisfies the freezing point ≤ 38°C and the iodine value ≥ 60g I2 / 100g; and the composition of the fractionated fatty acid is: C14 is 0.10%~0.5%, C16 is 20%~25%, C18 is 6%~8%, C18:1 is 50%~55%, and C18:2 is 10%~15%.

[0007] The temperature of the raw material tank in S1 is maintained at 45-50°C, and the temperature of the crystal melting tank is maintained at 65-70°C.

[0008] Among them, after heating in S2, the material temperature range is 65~70°C, the crystallization kettle is operated and stirred at a frequency of 25Hz; the temperature is maintained stable for more than 30 minutes.

[0009] The step of cooling down in stages includes: The first stage of cooling: from 65℃ to 50℃; the initial cooling rate is 7.5℃ every half hour; The second stage of cooling: from 50℃ to 35℃; the initial cooling rate is 3℃ every half hour; The third stage of cooling: from 35℃ to 25℃; the initial cooling rate is 2~3℃ every half hour; The fourth stage of cooling: from 25℃ to 15℃; the initial cooling rate is 4~5℃ every half hour; The fifth stage of cooling: from 15℃ to 10℃; the initial cooling rate is 1~2℃ every half hour.

[0010] Wherein, obtaining the crystal reflectivity factor of each pixel includes: For the low-temperature crystallization image at each moment, a pixel window is preset with each pixel as the center; on each characteristic band of each pixel, the mean reflectivity of all pixels in the pixel window of each pixel is obtained, which is recorded as the first mean; the difference between the reflectivity of each pixel and the first mean is obtained, which is recorded as the first difference; the mean reflectivity of all pixels in the preset neighborhood of each pixel is recorded as the second mean, and the difference between the second mean and the first mean is obtained, which is recorded as the second difference; the first difference is merged with the second difference to obtain the crystal reflectivity characteristic factor of each pixel.

[0011] The method of using a preset number of pixels as crystal pixels based on the crystal reflectivity factor and using a region growing algorithm to obtain all crystallized regions is specifically as follows: The crystal pixels of each characteristic band of the low-temperature crystallization image at each moment are respectively used as initial seed points; The growth condition is that the absolute value of the reflectivity difference between the search pixel and the pixel to be grown is less than or equal to a preset threshold.

[0012] The degree of crystallization sufficiency of the low-temperature crystallization image at each moment is obtained as follows: The fusion result of the difference between the crystal reflectivity characteristic factors of the crystallization pixel and the other pixels in each crystallization area of ​​the low-temperature crystallization image at each moment is recorded as the third difference; the product of the third difference and the disorder degree of the reflectivity of all pixels in each crystallization area is used as the explosive nucleation index of the corresponding crystallization area; For each crystallization region in each characteristic band of the low-temperature crystallization image at each moment, the fusion result of the difference in the number of pixels between each crystallization region and all other crystallization regions is recorded as the fourth difference; the fusion result of the difference in the mean reflectivity between each crystallization region and all other crystallization regions is recorded as the fifth difference; based on the fourth difference and the fifth difference, the crystal size consistency of each crystallization region is obtained; Calculating the ratio of the explosive nucleation index to the crystal size consistency, and taking the normalized value of the cumulative sum of the ratios of all crystallized regions in each characteristic band of the low-temperature crystallization image at each moment as the crystallization sufficiency factor of each characteristic band of the low-temperature crystallization image at each moment; The crystallization sufficiency factors of the low-temperature crystallization images at each moment in all characteristic bands are taken as input, and the multi-factor analysis method is used to obtain the crystallization sufficiency of the low-temperature crystallization images at each moment, wherein the weights of the crystallization sufficiency factors corresponding to the low-temperature crystallization images in each characteristic band are determined by the entropy weight method.

[0013] The crystallization separation factor is confirmed and the cooling rate is controlled, specifically: The crystallization separation factor of the xth crystallization interval is recorded as , its formula form is: ; In the formula, is the interquartile range of the corresponding crystallization degree of all low-temperature crystallization images in the xth crystallization interval; is the total number of low-temperature crystallization images obtained in the xth crystallization interval; is the difference in the degree of crystallization between the low-temperature crystallization images at the nth moment and the n+1th moment in the xth crystallization interval; norm() is the normalization function, and e is a natural constant; When the crystallization separation factor of a crystallization interval is less than a preset separation threshold, the cooling rate of the corresponding crystallization interval is not adjusted; otherwise, the cooling rate of the corresponding crystallization interval is increased by a preset amplitude.

[0014] Among them, the nitrogen pressure in S4 is 4~6bar.

[0015] This application has at least the following beneficial effects: When the cooling rate is regulated, the present application first obtains a hyperspectral image of the fatty acid solution at each moment, and uses principal component analysis to obtain a number of corresponding characteristic bands, which is helpful for subsequent analysis based on the reflectivity on the characteristic bands to obtain crystal pixels and crystallization regions; the crystallization sufficiency factor is obtained based on the crystal nucleation characteristics and crystal size characteristics in the crystallization region, and the crystallization nucleation speed characteristics and crystallization uniformity characteristics of the high-melting-point saturated fatty acid in the crystallization region are comprehensively considered, which more accurately reflects the crystallization precipitation status of the high-melting-point saturated fatty acid in the crystallization region; the crystallization sufficiency degree is obtained through the crystallization sufficiency factor, which fully considers The complete separation characteristics of saturated fatty acid crystals in fatty acid solutions in all characteristic bands were studied, and the crystallization separation factor was obtained according to the temporal variation characteristics of the crystallization sufficiency. On this basis, the cooling rate of the low-temperature crystallization stage in the crystallization filter press method of oleic acid production was adjusted. The complete crystallization separation of fatty acid solutions and saturated fatty acids such as hexadecanoic acid and stearic acid was more accurately evaluated, providing scientific data support for the control and adjustment of the oleic acid crystallization filter press process, avoiding the disadvantage that in the process of producing oleic acid by the crystallization filter press process, the crystal slurry obtained in the low-temperature crystallization stage is mixed with more saturated fatty acids, thereby affecting the oleic acid yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a production and processing process of low-temperature crystallized oleic acid provided in this application; Figure 2 A schematic diagram of the specific steps for controlling the cooling rate provided in this application; Figure 3 The present application provides a process flow chart for producing oleic acid using a crystallization filter press method. DETAILED DESCRIPTION

[0017] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0019] It should also be noted that the terms "first" and "second" in this application and its drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. The method disclosed in the embodiments of the present application or the method shown in the flow chart includes one or more steps for implementing the method. Without departing from the scope of protection of this application, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0020] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0021] The present application proposes a production and processing technology of low temperature crystallized oleic acid, which is applied to the technical field of oleic acid production and processing. Figure 1 , the process comprises: Before the production and processing of low-temperature crystalline oleic acid, check whether all water pumps, water levels, programmable valves\regulating valves, flow meters, temperature transmitters, liquid level transmitters, and pressure transmitters can operate normally; check whether the circulating water and refrigerator can operate normally and are within the process temperature range; confirm that the diaphragm filter press equipment is normal; check whether the material pipelines, water pipelines, gas pipelines, steam pipelines, etc. are unobstructed.

[0022] Example 1 S1: Pump the fractionated fatty acid from the raw material tank into the crystal melting tank, set the feed tank temperature to maintain at 45°C, and the crystal melting tank temperature to maintain at 65°C. In this embodiment, the fractionated fatty acid is a fatty acid obtained by fractionating palm fatty acid distillate (PFAD), and its indicators must meet the following requirements: freezing point ≤38°C, iodine value ≥60g I2 / 100g; in the fatty acid composition: C14 is 0.10%~0.5%, C16 is 20%~25%, C18 is 6%~8%, C18:1 is 50%~55%, and C18:2 is 10%~15%.

[0023] S2: Heat the fractionated fatty acids in the crystal melting tank and send them into the crystallization kettle to maintain a stable temperature.

[0024] Specifically, start the crystallization kettle for stirring, set the frequency to 25 Hz, open the feed control valve, start the feed pump, pass the above-mentioned fractionated fatty acids through the flow meter, and send them into the crystallization kettle after heating, ensuring that the temperature of the material entering the crystallization kettle after heating is between 65 and 70°C. When the total feed amount reaches the set value, stop feeding; maintain the temperature stable for 30 minutes, and the melting crystal process is completed. It should be noted that the temperature should be maintained for at least 30 minutes.

[0025] S3: Cooling the temperature in stages, controlling the cooling rate during each stage to obtain a crystal slurry.

[0026] After the feeding is completed, the cooling and crystallization process begins. The whole process is carried out according to the programmed cooling process and is divided into the following stages: The first stage of cooling: from 65℃ to 50℃.

[0027] Open the control valve, start the temperature control water pump to introduce temperature control water into the jacket. The temperature of the temperature control water is 40℃. Expel the air in the cooling pipe. After the temperature control water is full, open the inlet and outlet manual valves, start the circulating water pump, control the circulating cooling water temperature to 12℃, and maintain the initial cooling speed of 7.5℃ every half hour.

[0028] The second stage of cooling: from 50℃ to 35℃; Turn on the normal temperature water pump to add normal temperature water to the circulating water pump inlet for cooling. The temperature of the normal temperature water is 25°C. The temperature of the circulating cooling water is controlled at 12°C. The initial cooling speed is 3°C every half hour for a total of 150 minutes. Maintain this temperature for 60 minutes.

[0029] The third stage of cooling: from 35℃ to 25℃; Turn on the low-temperature water pump to add normal temperature water to the circulating water pump inlet for cooling. The normal temperature water is 25°C. The circulating cooling water temperature is controlled at 12°C. The initial cooling rate is 2°C every half hour.

[0030] The fourth stage of cooling: from 25℃ to 15℃; The circulating cooling water temperature is controlled to be 12°C, and the initial cooling rate is 4°C per half hour.

[0031] The fifth stage of cooling: from 15℃ to 10℃; The circulating cooling water temperature was controlled to be 7°C, and the initial cooling rate was 1°C per half hour. The temperature was maintained at 10°C for 30 minutes to obtain a crystal slurry.

[0032] During each stage of cooling, the material condition must be observed from the viewing mirror of the crystallization kettle. After the cooling is completed, the next step can be carried out. The final crystal slurry is a white material with a certain fluidity.

[0033] The specific steps of controlling the cooling rate are as follows: S301: taking the hyperspectral image of the fatty acid solution at each moment as the low-temperature crystallization image at each moment, and using principal component analysis to obtain a plurality of characteristic bands of the low-temperature crystallization image.

[0034] A hyperspectral imager is used to obtain a hyperspectral image in the cooling and crystallization stage of the oleic acid production process. The specific acquisition method is: the external probe of the hyperspectral imager is used to obtain a hyperspectral image of the fatty acid solution at an angle perpendicular to the fatty acid solution, wherein an auxiliary light source is used to perform supplementary light irradiation at an angle perpendicular to the fatty acid solution. The hyperspectral image acquisition time interval is set to 5 minutes in this embodiment. In order to prevent the acquired hyperspectral image of the fatty acid solution from being affected by external noise interference and subsequent analysis, the BM3D algorithm is used to denoise the acquired hyperspectral image; the implementer can adjust the image acquisition time interval and the image denoising algorithm according to the actual situation, and this application does not limit this. The acquired hyperspectral image of the fatty acid solution is called a low-temperature crystallization image for convenience of subsequent description.

[0035] The low-temperature crystallization images acquired at all times are taken as input respectively, and the sparse principal component analysis and feature selection (SPCAFS) algorithm is used to obtain the characteristic bands in each low-temperature crystallization image. The total number of characteristic bands adopts the default setting of the SPCAFS algorithm. Since the BM3D algorithm and the SPCAFS algorithm are both well-known technologies, the specific acquisition process will not be described in detail.

[0036] At this point, the reflectivity of any pixel in each characteristic band of the low-temperature crystallization image at each moment can be obtained by the above method.

[0037] S302: Obtaining a crystal reflectivity factor of each pixel according to the difference in reflectivity between each pixel of the low-temperature crystallization image at each moment and the pixels in the local range in the same characteristic band; taking a preset number of pixels as crystal pixels based on the crystal reflectivity factor, and using a regional growing algorithm to obtain all crystallization regions.

[0038] In the low-temperature crystallization images at each moment, as the low-temperature treatment proceeds, high-melting-point saturated fatty acids such as hexadecanoic acid and stearic acid in the fatty acid solution will gradually precipitate, and because the solid crystal has a more regular surface, it will lead to an increase in the directional reflection of light, thus showing a higher reflectivity in the low-temperature crystallization image compared to the fatty acid solution. When the high-melting-point hexadecanoic acid and stearic acid are precipitated, the crystal precipitation is completed, and the reflectivity of the crystal area reaches the highest. In addition, in the low-temperature crystallization process of fatty acids, according to the nucleation theory, high-melting-point hexadecanoic acid and stearic acid as solute molecules are more likely to precipitate in a concentrated manner.

[0039] Based on this, according to the difference in reflectivity between each pixel of the low-temperature crystallization image at each moment and the pixels in the local range on each characteristic band thereof, the crystal reflectivity factor of each pixel is obtained: for the low-temperature crystallization image at each moment, a pixel window is preset with each pixel as the center; on each corresponding characteristic band, the mean reflectivity of all pixels in the pixel window of each pixel is obtained, recorded as the first mean; the difference between the reflectivity of each pixel and the first mean is obtained, recorded as the first difference; the mean reflectivity of all pixels in the preset neighborhood of each pixel is recorded as the second mean, and the difference between the second mean and the first mean is obtained, recorded as the second difference; the first difference is merged with the second difference to obtain the crystal reflectivity characteristic factor of each pixel of the low-temperature crystallization image at each moment on each characteristic band thereof.

[0040] In this embodiment, the size of the pixel window is The preset neighborhood is eight neighborhoods, and the implementer can adjust it according to the actual situation. In the process of obtaining the crystal reflectivity characteristic factor, the difference calculation method is used to measure the difference characteristics between the variables. The first difference and the second difference are merged, specifically: the first difference is recorded as A, and the second difference is recorded as B. The formula form of the crystal reflectivity characteristic factor is: exp(A)+exp(B); wherein exp() is an exponential function with a natural constant as the base.

[0041] When high-melting-point saturated fatty acids are precipitated, the reflectivity of the pixel is significantly different from the reflectivity of the surrounding neighborhood, and the difference from the mean reflectivity of other pixels in the window is even greater, which will cause the crystal reflectivity characteristic factor of the pixel to become more prominent, that is, the larger the crystal reflectivity characteristic factor of the pixel, that is, the larger the difference between the pixel and the average reflectivity of all pixels in its corresponding pixel window, and the larger the difference between the mean reflectivity of the eight neighborhood pixels corresponding to the pixel and the mean reflectivity of all other pixels in the pixel window.

[0042] The crystal reflectivity characteristic factors of all pixels in the low-temperature crystallization image at each moment in each characteristic band are sorted in descending order, and a preset number of pixels are screened as crystal pixels in the low-temperature crystallization image at each moment. It should be noted that in this embodiment, the preset number is 20% of the number of all pixels in the low-temperature crystallization image at each moment. The implementer can set the number of screened crystal pixels according to actual conditions. The more crystal pixels are screened, the more accurate the analysis of the precipitation results of high-melting point saturated fatty acids in the fatty acid solution during the low-temperature process will be. At the same time, it will cause the risk of misjudging the fatty acid solution pixels as crystal pixels and increase the amount of calculation.

[0043] During the crystallization process of fatty acid solution, once high-melting-point saturated fatty acids in the region precipitate to form crystal nuclei, due to the growth core provided by the crystal nuclei, the high-melting-point saturated fatty acids around the crystal nuclei in the fatty acid solution are more inclined to grow at the crystal nucleus position to form larger crystals. The higher the uniformity of the crystals formed by aggregation, the better the crystallization effect of the high-melting-point saturated fatty acids in the fatty acid solution.

[0044] The crystal pixels of the low-temperature crystallization image at each moment in each characteristic band are respectively used as initial seed points, and the regional growing algorithm is used to obtain the crystallization region of each crystal pixel, wherein the search direction of the crystallization region takes the positive right direction of each pixel as the initial search direction, and when the absolute value of the reflectivity difference between the search pixel and the pixel to be grown is less than or equal to a preset threshold, the pixel to be grown is divided into the crystallization region of the crystal pixel, and the growth continues with the pixel to be grown as a new seed point; conversely, when the reflectivity difference between the search pixel and the pixel to be grown is greater than the preset threshold, the growth continues in the search direction rotated 45° clockwise from the original search direction of the search pixel until all searches within the eight neighborhoods of all pixels are completed. In this embodiment, the threshold is taken as the average reflectivity of all crystal pixels in the crystallization image. Since the region growing algorithm is a well-known technology, the specific acquisition process will not be described in detail.

[0045] The region growing algorithm used in this application can obtain a crystalline region of unlimited shape using the crystalline pixel as the initial seed point, and obtain all pixel regions with a small difference in reflectivity from the crystalline pixel, which is convenient for subsequent analysis of the explosive nucleation characteristics and crystal morphology characteristics of high-melting-point saturated fatty acids.

[0046] S303: The crystallization sufficiency of the low-temperature crystallization image at each moment is obtained based on the difference between the reflectance characteristic factors of the crystallization pixels in each crystallization area and the other pixels in each characteristic band of the low-temperature crystallization image at each moment, combined with the difference in pixel distribution and reflectance distribution between each crystallization area and the other crystallization areas.

[0047] Since the fast-precipitated high-melting-point saturated fatty acids grow too fast during crystallization, the crystal structure is irregular, showing larger crystals and uneven crystal distribution. Based on this, firstly, according to the difference between the crystal reflectivity characteristic factors of the crystal pixels and the remaining pixels in each crystal region in each characteristic band of the low-temperature crystallization image at each moment, combined with the distribution characteristics of the reflectivity in the corresponding crystal region, the explosive nucleation index of each crystal region in the low-temperature crystallization image at each moment is obtained: the fusion result of the difference between the crystal reflectivity characteristic factors of the crystal pixels and the remaining pixels in each crystal region of the low-temperature crystallization image at each moment is recorded as the third difference; the product of the third difference and the chaos degree of the reflectivity of all pixels in each crystal region is taken as the explosive nucleation index of the corresponding crystal region.

[0048] In this embodiment, in the process of obtaining the explosive nucleation index, the fusion result of the differences between the variables is specifically the cumulative sum of the absolute values ​​of the differences between the variables; and the information entropy is used to measure the degree of confusion of multiple variables.

[0049] When high-melting-point saturated fatty acids precipitate too quickly during low-temperature crystallization, the faster the high-melting-point saturated fatty acid crystal nucleus formation speed, the more uneven the precipitated high-melting-point saturated fatty acid crystals, the greater the difference in crystal reflectivity characteristic factors between all pixels within the crystallization region, the more chaotic the reflectivity of the pixels within the crystallization region, and the greater the explosive nucleation index of the crystallization region, that is, the greater the absolute value of the cumulative difference between the crystal reflectivity characteristic factors corresponding to the crystallization pixels in the crystallization region and all other pixels, and the greater the information entropy of the reflectivity of all pixels in the crystallization region.

[0050] Only by evaluating the degree of low-temperature crystallization of fatty acid solutions based on the explosive nucleation index of the crystallization area, it is impossible to accurately evaluate the uniformity of high-melting-point saturated fatty acid precipitation crystals. The higher the uniformity of high-melting-point saturated fatty acid precipitation crystals, the stronger the consistency of the morphology and size of the precipitated crystals. Based on this, according to the difference in pixel distribution and reflectivity distribution between each crystallization area and the remaining crystallization areas in the low-temperature crystallization image at each moment, the crystal size consistency of each crystallization area is obtained: for each crystallization area in each characteristic band of each low-temperature crystallization image, the fusion result of the difference in the number of pixels between each crystallization area and all other crystallization areas is recorded as the fourth difference; the fusion result of the difference in the mean reflectivity between each crystallization area and all other crystallization areas is recorded as the fifth difference; based on the fourth difference and the fifth difference, the crystal size consistency of each crystallization area is obtained, wherein the crystal size consistency is negatively correlated with the fourth difference and the fifth difference.

[0051] It should be noted that a positive correlation is a relationship in which as one variable increases, another variable also increases; a negative correlation is a relationship in which as one variable increases, another variable decreases.

[0052] In this embodiment, in the process of obtaining crystal size consistency, the fusion result of the difference is specifically the cumulative sum of the absolute values ​​of the differences; the crystal size consistency is specifically the inverse of the product of the fourth difference and the fifth difference. In order to avoid the situation where the denominator is zero, it is necessary to add a preset value to the denominator, and the preset value is 0.1.

[0053] When the degree of precipitation of high-melting-point saturated fatty acids in the fatty acid solution is more uniform during the low-temperature crystallization process, the crystal size between the crystallization regions and the crystal precipitation conditions in the crystallization regions are more consistent, and the crystal size consistency in the crystallization regions is stronger, that is, the difference in the number of pixels contained in the crystallization region and all other crystallization regions is smaller, and the difference in the mean reflectance of all pixels corresponding to the crystallization region and all other crystallization regions is smaller.

[0054] Generally, when the precipitation effect of high melting point saturated fatty acids in the low temperature crystallization process of fatty acids is more sufficient, the explosive nucleation condition of the fatty acid solution crystallization area is milder, and the crystal size consistency of the fatty acid crystallization area is stronger. Based on this, according to the explosive nucleation index of the crystallization area of ​​each characteristic band of the low temperature crystallization image at each moment and the crystal size consistency, the crystallization sufficient factor of each characteristic band of the low temperature crystallization image at each moment is obtained: for the crystallization area of ​​each characteristic band of the low temperature crystallization image at each moment, the ratio of the explosive nucleation index to the crystal size consistency is calculated, and the normalized value of the cumulative sum of the ratios of all crystallization areas of each low temperature crystallization image on each characteristic band is used as the crystallization sufficient factor of each characteristic band of the low temperature crystallization image at each moment. In this embodiment, the normalization method uses the sigmoid function, and the implementer can select a suitable normalization method according to the actual situation.

[0055] When the precipitation effect of high-melting-point saturated fatty acids is more complete during the low-temperature crystallization process of fatty acids, it means that the separation effect between saturated fatty acids and unsaturated fatty acids in the fatty acid solution is better, and the crystallization sufficiency factor is larger, that is, the explosive nucleation condition of all crystallization areas in the low-temperature crystallization image under the characteristic band is milder, and the crystal size consistency of all crystallization areas under the corresponding characteristic band of the low-temperature crystallization image is stronger.

[0056] The crystallization sufficiency factor of the low-temperature crystallization image at each moment in all characteristic bands is taken as input, and the CIM (Comprehensive Index Method) comprehensive index method is used to obtain the crystallization sufficiency at any moment, wherein the weight of the crystallization sufficiency factor of the low-temperature crystallization image at each characteristic band is determined by the entropy weight method. Since both the CIM comprehensive index method and the entropy weight method are well-known technologies, the specific acquisition process will not be described in detail.

[0057] S304: taking a preset time length as a crystallization interval; confirming a crystallization separation factor according to the distribution of all low-temperature crystallization images and the distribution of the crystallization sufficiency in each crystallization interval, and controlling the cooling rate.

[0058] Evaluating the precipitation effect of high-melting-point saturated fatty acids in fatty acid solutions only by the degree of crystallization of low-temperature crystallization images at each moment ignores the temporal variation characteristics of the crystallization of high-melting-point saturated fatty acids. There is a disadvantage that the temporal instability of the low-temperature crystallization process of fatty acid solutions leads to inaccurate evaluation of the separation effect of saturated fatty acids.

[0059] Normally, as saturated fatty acids in a fatty acid solution are precipitated through low-temperature crystallization, the concentration of high-melting-point saturated fatty acids in the fatty acid solution decreases, causing the degree of crystallization to gradually tend to a stable state. Conversely, when the degree of crystallization in the fatty acid solution becomes more and more obvious over time, it means that the saturated fatty acids have not been fully separated from the fatty acid solution, and the cooling rate of the fatty acids should be adjusted in a timely manner to promote the crystallization of saturated fatty acids.

[0060] Based on the above analysis, the preset time length is taken as a crystallization interval. In this embodiment, the preset time length is 30 minutes, and the implementer can adjust it according to the actual situation. Now, any crystallization interval in the low-temperature crystallization process of fatty acid solution is taken as an example for analysis. According to the distribution of all low-temperature crystallization images in each crystallization interval and the distribution of the corresponding crystallization sufficiency, the crystallization separation factor of each crystallization interval is obtained: the crystallization separation factor of the x-th crystallization interval is recorded as , its formula form is: ; In the formula, is the interquartile range of the corresponding crystallization degree of all low-temperature crystallization images in the x-th crystallization interval, which measures the discrete distribution of the crystallization degree; is the total number of low-temperature crystallization images obtained in the xth crystallization interval; is the difference in the degree of crystallization between the low-temperature crystallization images at the nth moment and the n+1th moment in the xth crystallization interval; norm() is a normalization function, so that The value range of is between [0,1]. In this embodiment, it is a sigmoid function, and e is a natural constant.

[0061] The better the effect of separating saturated fatty acids from the fatty acid solution by crystallization during the low-temperature crystallization process in the crystallization interval, the more significant the gradual stabilization of the high-melting point saturated fatty acid crystallization state in the fatty acid solution over time, the more stable the high-melting point saturated fatty acid crystallization state in the time interval, the smaller the crystallization separation factor in the crystallization interval, that is, the smaller the interquartile range of the crystallization degree corresponding to all low-temperature crystallization images in the crystallization interval, the smaller the difference between the crystallization degrees corresponding to the low-temperature crystallization images at adjacent moments in the crystallization interval, and the smaller the corresponding exponential function value. At this time, there is no need to adjust the cooling rate of the fatty acid solution in the low-temperature crystallization stage to avoid the situation where the high-melting point saturated fatty acid crystals precipitate too quickly and cause uneven crystallization.

[0062] When the crystallization separation factor of the crystallization interval obtained in real time is less than the preset separation threshold, it is determined that the separation effect of saturated fatty acid crystals and fatty acid solution within the current crystallization interval time range is relatively sufficient, and there is no need to adjust the cooling rate of the low-temperature crystallization stage of the fatty acid solution to avoid the high-melting point saturated fatty acid crystallization precipitation too fast to cause uneven crystallization; and when the crystallization separation factor of the crystallization interval obtained in real time is greater than or equal to the preset separation threshold, it is determined that the separation effect of saturated fatty acid crystals and fatty acid solution within the current crystallization interval time range is insufficient, and the cooling rate of the current fatty acid solution in the low-temperature crystallization stage needs to be adjusted in time. For high-melting point saturated fatty acids, the temperature is gradually reduced so that the high-melting point saturated fatty acid crystallization uniform precipitation effect is better, and the possibility of unsaturated fatty acids being crystallized is smaller, and the specific adjustment method is: the cooling rate in the corresponding cooling crystallization stage of the current crystallization interval is adjusted 2 ° C every half an hour, and the total cooling rate adjustment time is 30min. In this embodiment, the crystallization separation threshold value is 0.7.

[0063] Among them, the schematic diagram of the specific steps for controlling the cooling rate is as follows Figure 2 As shown, the above method can be used to adjust the low-temperature crystallization cooling rate in the process of producing oleic acid by the crystallization filter press method to obtain a crystal slurry.

[0064] S4: hydraulically pressing the obtained crystal slurry under a nitrogen atmosphere to obtain oleic acid.

[0065] Specifically, after the cooling and crystallization process is completed, the obtained crystal slurry is installed with filter cloth and the filter plate is pressed, the liquid collecting tank is installed, and the water in the frozen oleic acid receiving tank is drained. After the preparation work is completed, the programmable valve of the crystallization kettle outlet is manually opened, and the programmable valve of compressed nitrogen on the top of the kettle is opened at the same time. The nitrogen pressure is 4 bar. After the crystal slurry enters the screw pump, the pump is turned on to feed the filter press. Pay attention to the feed pressure of the filter press and adjust the feed frequency of the screw pump at any time. When the feed pressure of a filter press reaches 1.0MPA, the feed valve is closed, the filter press starts the pressing process, and the pressing water pump is started to start hydraulic pressing according to the control requirements of the filter press to separate the liquid oleic acid and fatty acid filter cake, and the qualified oleic acid is filled.

[0066] Among them, the process flow chart of producing oleic acid by crystallization filter press method is as follows Figure 3 shown.

[0067] Example 2 S1: Pump the fractionated fatty acid from the raw material tank into the crystal melting tank, set the feed tank temperature to maintain at 50°C, and the crystal melting tank temperature to maintain at 65°C. The fractionated fatty acid in this application is the fatty acid obtained by fractionation of PFAD, and the relevant indicators must meet the following requirements: freezing point ≤38°C, iodine value ≥60g I2 / 100g; fatty acid composition: C14 is 0.10%~0.5%, C16 is 20%~25%, C18 is 6%~8%, C18:1 is 50%~55%, and C18:2 is 10%~15%.

[0068] S2: Heat the fractionated fatty acids in the crystal melting tank and send them into the crystallization kettle to maintain a stable temperature.

[0069] Specifically, start the crystallization kettle to stir, set the frequency to 25 Hz, open the feed control valve, start the feed pump, pass the above-mentioned fractionated fatty acid through the flow meter, and send it into the crystallization kettle after heating, ensuring that the temperature of the material entering the crystallization kettle after heating is between 65 and 70°C. When the total feed amount reaches the set value, stop feeding; maintain the temperature stable for more than 60 minutes, and the melting crystal process is completed.

[0070] S3: Cooling in stages, controlling the cooling rate in each stage in the same manner as in Example 1, to obtain a crystal slurry. The initial cooling rate in the third stage is 2°C per half hour, the initial cooling rate in the fourth stage is 5°C per half hour, and the initial cooling rate in the fifth stage is 1°C per half hour.

[0071] S4: The slurry was hydraulically pressed in the same manner as in Example 1, wherein the nitrogen pressure was 6 bar.

[0072] Example 3 S1: Pump the fractionated fatty acids from the raw material tank into the crystal melting tank. Set the feed tank temperature to 45°C and the crystal melting tank temperature to 70°C. The fractionated fatty acids in this application are purchased fatty acids, and the relevant indicators must meet the following requirements: freezing point ≤ 38°C, iodine value ≥ 60g I2 / 100g; fatty acid composition: C14 is 0.10%~0.5%, C16 is 20%~25%, C18 is 6%~8%, C18:1 is 50%~55%, and C18:2 is 10%~15%.

[0073] S2: Heat the fractionated fatty acids in the crystal melting tank and send them into the crystallization kettle to maintain a stable temperature.

[0074] Specifically, start the crystallization kettle to stir, set the frequency to 25 Hz, open the feed control valve, start the feed pump, pass the above-mentioned fractionated fatty acid through the flow meter, and send it into the crystallization kettle after heating, ensuring that the temperature of the material entering the crystallization kettle after heating is between 65 and 70°C. When the total feed amount reaches the set value, stop feeding; maintain the temperature stable for 90 minutes, and the melting crystal process is completed.

[0075] S3: Cooling in stages, controlling the cooling rate in each stage in the same manner as in Example 1, to obtain a crystal slurry. The initial cooling rate in the third stage is 3°C per half hour, the initial cooling rate in the fourth stage is 5°C per half hour, and the initial cooling rate in the fifth stage is 2°C per half hour.

[0076] S4: The slurry was hydraulically pressed in the same manner as in Example 1, wherein the nitrogen pressure was 5 bar.

[0077] During the filtration and pressing process, observe the condition of the liquid material and take samples to test the freezing point, acid value and iodine value of the liquid.

[0078] The main indicators of oleic acid obtained by the production and processing technology in the embodiment of the present application meet the requirements of freezing point <10°C, moisture ≤0.3, iodine value ≥85g I2 / 100g, and C18:1 content ≥70.

[0079] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two continuous boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two continuous operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0080] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A production and processing technology of low temperature crystallized oleic acid, characterized in that: The process includes: S1: pumping fractionated fatty acids from the raw material tank into the crystal melting tank; S2: heating the fractionated fatty acid in the crystal melting tank and sending it into the crystallization kettle to maintain a stable temperature; S3: Cooling in stages, controlling the cooling rate in each stage to obtain a crystal slurry; wherein the specific steps of controlling the cooling rate are: S301: using the hyperspectral image of the fatty acid solution at each moment as the low-temperature crystallization image at each moment, and using principal component analysis to obtain several characteristic bands of the low-temperature crystallization image; S302: obtaining a crystal reflectivity factor of each pixel according to the difference in reflectivity between each pixel of the low-temperature crystallization image at each moment and the pixels in the local range on the same characteristic band; taking a preset number of pixels as crystal pixels based on the crystal reflectivity factor, and using a regional growing algorithm to obtain all crystallization regions; S303: according to the difference between the reflectivity characteristic factors of the crystallization pixels in each crystallization area and the other pixels in each characteristic band of the low-temperature crystallization image at each moment, combined with the difference in pixel distribution and reflectivity distribution between each crystallization area and the other crystallization areas, the crystallization sufficiency of the low-temperature crystallization image at each moment is obtained; S304: taking a preset time length as a crystallization interval; determining a crystallization separation factor according to the distribution of all low-temperature crystallization images and the distribution of the crystallization sufficiency in each crystallization interval, and controlling the cooling rate; S4: hydraulically pressing the obtained crystal slurry under a nitrogen atmosphere to obtain oleic acid.

2. The production and processing technology of low-temperature crystallized oleic acid according to claim 1, characterized in that: The fractionated fatty acid in S1 is a fatty acid obtained by fractionation of PFAD or a purchased fatty acid, and satisfies the freezing point ≤ 38°C and the iodine value ≥ 60g I2 / 100g; and the composition of the fractionated fatty acid is: C14 is 0.10%~0.5%, C16 is 20%~25%, C18 is 6%~8%, C18:1 is 50%~55%, and C18:2 is 10%~15%.

3. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: In S1, the temperature of the raw material tank is maintained at 45-50°C, and the temperature of the crystal melting tank is maintained at 65-70°C.

4. The production and processing technology of low-temperature crystallized oleic acid according to claim 1, characterized in that: After heating in S2, the material temperature ranges from 65 to 70°C, and the crystallization kettle operates and stirs at a frequency of 25 Hz; the temperature is maintained stable for more than 30 minutes.

5. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: The staged cooling includes: The first stage of cooling: from 65℃ to 50℃; the initial cooling rate is 7.5℃ every half hour; The second stage of cooling: from 50℃ to 35℃; the initial cooling rate is 3℃ every half hour; The third stage of cooling: from 35℃ to 25℃; the initial cooling rate is 2~3℃ every half hour; The fourth stage of cooling: from 25℃ to 15℃; the initial cooling rate is 4~5℃ every half hour; The fifth stage of cooling: from 15℃ to 10℃; the initial cooling rate is 1~2℃ every half hour.

6. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: The step of obtaining the crystal reflectivity factor of each pixel includes: For the low-temperature crystallization image at each moment, a pixel window is preset with each pixel as the center; on each characteristic band of each pixel, the mean reflectivity of all pixels in the pixel window of each pixel is obtained, which is recorded as the first mean; the difference between the reflectivity of each pixel and the first mean is obtained, which is recorded as the first difference; the mean reflectivity of all pixels in the preset neighborhood of each pixel is recorded as the second mean, and the difference between the second mean and the first mean is obtained, which is recorded as the second difference; the first difference is merged with the second difference to obtain the crystal reflectivity characteristic factor of each pixel.

7. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: The method uses a preset number of pixels as crystal pixels based on the crystal reflectivity factor and adopts a region growing algorithm to obtain all crystal regions, specifically: The crystal pixels of each characteristic band of the low-temperature crystallization image at each moment are respectively used as initial seed points; The growth condition is that the absolute value of the reflectivity difference between the search pixel and the pixel to be grown is less than or equal to a preset threshold.

8. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: The crystallization sufficiency of the low-temperature crystallization image at each moment is specifically obtained as follows: The fusion result of the difference between the crystal reflectivity characteristic factors of the crystallization pixel and the other pixels in each crystallization area of ​​the low-temperature crystallization image at each moment is recorded as the third difference; the product of the third difference and the disorder degree of the reflectivity of all pixels in each crystallization area is used as the explosive nucleation index of the corresponding crystallization area; For each crystallization region in each characteristic band of the low-temperature crystallization image at each moment, the fusion result of the difference in the number of pixels between each crystallization region and all other crystallization regions is recorded as the fourth difference; the fusion result of the difference in the mean reflectivity between each crystallization region and all other crystallization regions is recorded as the fifth difference; Based on the fourth difference and the fifth difference, the crystal size consistency of each crystallization region is obtained; Calculating the ratio of the explosive nucleation index to the crystal size consistency, and taking the normalized value of the cumulative sum of the ratios of all crystallized regions in each characteristic band of the low-temperature crystallization image at each moment as the crystallization sufficiency factor of each characteristic band of the low-temperature crystallization image at each moment; The crystallization sufficiency factors of the low-temperature crystallization images at each moment in all characteristic bands are taken as input, and the multi-factor analysis method is used to obtain the crystallization sufficiency of the low-temperature crystallization images at each moment, wherein the weights of the crystallization sufficiency factors corresponding to the low-temperature crystallization images in each characteristic band are determined by the entropy weight method.

9. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: The crystallization separation factor is confirmed and the cooling rate is controlled, specifically: The crystallization separation factor of the xth crystallization interval is recorded as , its formula form is: ; In the formula, is the interquartile range of the corresponding crystallization degree of all low-temperature crystallization images in the xth crystallization interval; is the total number of low-temperature crystallization images obtained in the xth crystallization interval; is the difference in the degree of crystallization between the low-temperature crystallization images at the nth moment and the n+1th moment in the xth crystallization interval; norm() is the normalization function, and e is a natural constant; When the crystallization separation factor of a crystallization interval is less than a preset separation threshold, the cooling rate of the corresponding crystallization interval is not adjusted; otherwise, the cooling rate of the corresponding crystallization interval is increased by a preset amplitude.

10. The production and processing technology of low temperature crystallized oleic acid according to claim 1, characterized in that: The nitrogen pressure in S4 is 4~6bar.

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