Solvent consumption is an important symbol to reflect the level of production technology of vegetable oil solvent extraction plants. The high solvent consumption in solvent extraction oil plant is not only detrimental to the efficiency of the enterprise and increases the processing cost of the enterprise, but also contradicts the national policy of promoting energy-saving and emission reduction, and more importantly, it threatens the safety of people’s lives and properties and the safety of the enterprise, which should be highly valued by the solvent extraction oil plant.
The unavoidable solvent consumption includes the amount of solvent carried away from crude oil, finished meal, wastewater, and exhaust gas; the avoidable solvent consumption refers to the amount of solvent loss caused by running, bubbling, dripping, and leakage. Due to the different processing technology and processing raw materials, the unavoidable solvent consumption is generally 0.3-1.5 kg/t material.
According to Chemsta more than 40 years of engineering experience in the industry, this article introduces the following aspects.
I Unavoidable dissolution depletion
1.1 Reduce the solvent content in the crude oil, the residual solubility of the crude oil is less than 100 ppm
– Increase the concentration of mixed oil
Generally based on the oil content of raw materials, the concentration of mixed oil is increased by 5-10% on this basis; master the solvent ratio, the oil making line without the expansion process, the solvent ratio is generally 0.8-1:1; while the solvent ratio of the oil making line with the expansion process is 0.5-0.8:1 is better; different processes slightly change.
– Control the evaporator oil temperature
The temperature of oil output from #1 evaporator under normal pressure is 75-80℃; the temperature of oil output from #2 evaporator is 95-115℃; the temperature of oil output from the steam tower is about 125℃.
Under negative pressure, the oil output temperature of #1 evaporator is 60-70℃; the oil output temperature of #2 evaporator is 100-110℃; the oil output temperature of the steam lifting tower is 110-115℃.
– Control the quality and amount of direct steam
The direct steam contains more water and the dosage is large, which will cause the liquid to flood in the steam tower and the solvent content in the gross oil exceeds the standard; a steam-water separator can be added or the direct steam can be heated into superheated direct steam to improve the steam quality and reduce the liquid flood in the steam tower.
– The evaporation amount must be uniform, not big or small, otherwise it will cause 1#, 2# evaporator liquid flooding, and steam tower desolvation is not clean, resulting in unstable residual solubility of gross oil, or even exceeding the standard.
– Precipitate or filter the mixed oil, remove the organic and inorganic impurities and reduce the evaporation system scaling and liquid flooding.
1.2 Reduce the solvent content in the meal, the finished meal residual soluble content is less than 700 ppm
– Cleaning out all the impurities picked up, due to poor permeability of impurities, which is not easy to evaporate the solvent out, will remain in the soybean meal; not only will cause the meal residual soluble to exceed the standard, but also affect the meal residual oil.
– Control the embryo piece thickness 0.3-0.4mm is more appropriate, too thin solvent penetration effect is poor, a wet meal containing solvent; too thick meal in the solvent is not suitable for evaporation out; resolutely put an end to the phenomenon of running raw, running raw soybean meal in the solvent content is seriously over the standard.
– Into the solvent extraction material moisture control due to the use of different solvent extractors is also slightly different: flat transition solvent extractor into the solvent extraction water 8-9%, drag chain solvent extractor into the solvent extraction water 9-9.5%, ring extractor into the solvent extraction water 10-12%
– Adjust the amount of spraying and spraying situation, try to extend the solvent extraction time, reduce the amount of wet meal containing solvent, wet meal containing less than 30% soluble is appropriate, the use of puffing process better results.
– Control the quality and amount of direct steam to reduce soybean meal caking, caking soybean meal steam should not be blown through, and the capacitor inside should not be steamed out, resulting in serious solvent overload in the meal.
– Increase the steaming off time. Adjust the steaming layer level, extend the wet meal steaming time, and reduce the solvent content in the meal as much as possible.
– Often check whether the fresh solvent with water, if the fresh solvent with water, a large amount of solvent with the wet meal brought to the steam off the machine, will cause the steam off machine load increases, but also cause soybean meal clumping, resulting in meal in the solvent seriously exceed the standard.
1.3 Reduce the solvent content in the wastewater and control it below 15 ppm
The temperature of water in the cooking tank is controlled at 92-95°C. Too high a temperature results in high steam usage and poor condenser condensation; too low results in high solvent content in the wastewater. Different process parameters vary slightly.
1.4 Solvent recovery in free gas
– The solvent in free gas can be absorbed by concentrated mixed oil first, then condensed and paraffin recovered.
– Add a paraffin injection pump and change primary paraffin absorption to secondary paraffin absorption to increase the absorption effect. If necessary, the exhaust fan can be stopped to reduce the exhaust gas emission, so that the emission is less than 2 m3/ton material and the solvent content in the exhaust gas is less than 15g/m3.
– Paraffin temperature of the absorption tower is less than 40℃; the Paraffin temperature of the analysis tower is controlled at 115-120℃ as appropriate. Properly open the direct steam of the analysis tower (0.02-0.1Mpa) to enhance the analysis effect of the analysis tower; often discharge the wastewater in paraffin to enhance the paraffin absorption effect; some due to the absence of a paraffin precipitation tank, in order to reduce the loss of paraffin caused by drainage, generally do not open the direct steam, so that the analysis effect is not good; in order to achieve better absorption effect, the solvent in rich oil In order to achieve better absorption effect, the solvent content in rich oil is generally less than 5%, and the solvent content in poor oil is less than 0.5%.
– Check the scaling of the packing in the absorption tower frequently, and determine whether to clean it according to the actual situation. It is better to add a filtering device in the paraffin absorption system to ensure the cleanliness of paraffin, and clean the impurities in the filter regularly; it is better to add a free gas purification device if there is a condition, to reduce the meal in the free gas so that the free gas can come out smoothly in the absorption tower, maintain the negative pressure of the system, and reduce the system running and dripping.
– The tail gas fan system can be installed with automatic control devices, according to the system pressure automatically adjust to reduce unnecessary waste.
– Condenser equipment and layout should be reasonable. The area of a single condenser can not be too large, too large circulating water flow rate is low, the effect is poor; condenser water intake methods in series, parallel, mixed, depending on the actual situation, in general, the series water intake method is better; circulating water pump equipped with scientific, otherwise it will either cause energy waste or insufficient water flow, condensation effect is poor.
1.5 Raw material quality
There are most low molecular sugars in immature oil, not yet fully synthesized polymer fats, low molecular sugars have a strong adsorption capacity for solvents, which is not conducive to solvent removal; moldy oil causes the decomposition of macromolecular substances into low molecular substances, which also have a strong adsorption capacity for solvents, which is not conducive to solvent removal.
ⅠⅠ Avoidable solvent consumption
2.1 Caused by leakage of equipment
– There are problems with the quality of the equipment itself.
Try to purchase equipment from regular manufacturers when purchasing to reduce equipment failure.
– Caused by human factors.
There is solvent leakage at flange, instrument, sight glass, driveshaft, etc. caused by human subjective factors in the process of overhaul, and improve the quality of staff overhaul by training them.
2.2 Caused the process is not perfect.
Through process adjustment and adding equipment to achieve reasonable use of energy inside the workshop, reduce the load of condenser and increase the condensation effect.
2.3 The good and bad quality of the solvent also has a direct impact on dissolution consumption.
The wider the process, the higher the dissolution consumption, also in the boiling point of high and low, low boiling point components, although easy to evaporate from the wet meal, but not easy to condensation recovery, high boiling point components, although not easy to evaporate but easy to condensation recovery. Therefore, the use of narrow flow and a reasonable boiling point of the solvent is conducive to the reduction of soluble consumption.
Ⅲ Strengthen staff skill training and production site management.
3.1 Strictly implement the workshop operation procedures, do not allow operators to simplify the process at will, and strengthen the coordination and cooperation between the processes to ensure continuous normal production in the workshop.
3.2 Watch, listen, think and do diligently, the operation should be formal and proficient, and small faults should be repaired and eliminated in time to ensure the continuous normal operation of equipment and avoid downtime due to equipment failure; strengthen equipment inspection to eliminate solvent leakage; especially some invisible parts to minimize solvent loss; ensure the system micro-negative pressure to be able to reduce leakage points and avoid unnecessary solvent loss.
3.3 Establish energy saving and consumption reduction incentive system, quantify the responsibility to the person; establish fault investigation system, reduce the failure rate, improve the equipment operation rate, not only realize the data management but also fully mobilize the staff’s work enthusiasm and subjective initiative
In the vegetable oil processing plant, the solvent extraction plant is a very important workshop, soluble consumption is the main technical indicator of the solvent extraction plant, soluble consumption of high and low consumption, not only affects the cost of processing enterprises, and more mainly affect the quality of oil meal and production safety and operator health, so in the oil solvent extraction process, must do everything possible to reduce solvent consumption. To a daily processing 80t of solvent extraction plant, for example, soluble consumption of 8kg / t, according to the annual processing of 24 000t of oil, annual consumption of solvent 192t; if the soluble consumption is reduced to 6kg / t, the annual consumption of solvent only 144t. According to the solvent ton price of $ 1000 yuan, the cost savings of $ 45000, which is a considerable expenditure for the enterprise. Therefore, it is very important to reduce solvent consumption both in terms of economic benefits and safety.
Ⅳ Several measures can be taken to reduce solvent consumption
4.1 Evaporation of miscella
The separation of solvent and oil in mixed oil is carried out through the first long tube and second long tube evaporator, disc type stripper. In order to ensure the quality of extracting oil, in addition to strictly abiding by the operation procedures, the following points must be noted:
– Must ensure that the flow of mixed oil evenly, otherwise it will make the evaporation equipment load unevenly, the temperature is not easy to control, and easy to produce turn over the tank, increasing the consumption of solvent.
– To ensure the stability of steam pressure, the steam pressure can not be lower than 0.5MPa, below which it can not be produced.
– The evaporation equipment should be cleaned regularly, not less than once a quarter, to ensure that the evaporation tube wall and shell are not scaled, so that the equipment operator can reach the best effect.
4.2 Solvent – water separator
Solvent – water separator is the key equipment for solvent and water separation. No matter what shape of water separator is used, the residence time of the solvent and water mixture in the container should be guaranteed to be about 30s, and the solvent discharge port and water discharge port should be strictly calculated according to the size of the container. The fresh solvent tank should be drained regularly to prevent the fresh solvent from water to make the material absorb water and swell causing the blockage of a part to bring unnecessary demolition and make the solvent leak out. The free gas discharge pipe of the water distribution combination cabinet should be smooth to prevent the pressure inside the water distributor from being too large so that the solvent level will drop and flow out from the drainage pipe. There should be a water seal pool outside the workshop so that once the solvent is leaked, it can be recovered.
4.3 Recovery of tail gas
The free gas in the solvent extraction plant is also one of the factors affecting solvent consumption. Every 1t of material added to the solvent extraction machine will bring in 2~2.5kg of air, then the free gas will take away more than 1kg of the solvent when discharged from the workshop, if discharged directly, it will pollute the environment, increase the safety hazard and increase the solvent consumption. Therefore, a condensation recovery device should be set up outdoors to recover the exhaust gas.
4.4 Wet meal drying and steaming off
The wet meal after solvent extraction contains 35% to 45% solvent, due to the large soluble content, the load of the desolvation steaming and drying system is large, increasing steam consumption. The solvent extraction section of Chemsta has the following features.
– Adding a drip-drying system, raising the original scraper seat by 40-50cm, with the same length and width, and adding a layer of steel plate filter in the middle, where the wet meal coming out of the extractors is first drained briefly, which can reduce part of the solvent evaporation.
– Changing the original vertical conveying wet meal scraper to 30° conveying to prevent the cylinder from blocking, resulting in a large amount of solvent leakage.
– After the wet meal enters the steam stripper, the height of the material layer must be strictly controlled, the temperature is not less than 80℃, and the steam hole of the bottom plate of the steam stripper is evenly sprayed with steam, which cannot leave a dead corner. After the reform, reduce the load of the dryer desolvation, to ensure that the finished meal detonation test qualified.
4.5 Reduce the leakage of solvent
The bearings of each transmission part of the solvent extraction workshop are subject to wear and tear, as well as the valves, pipe fittings, sight glasses, and other parts, because of poor sealing, easy to cause solvent leakage, while forming a safety hazard, especially in a summer production, management personnel and operators to do diligent look, touch, smell, find the problem in time to deal with, as long as to strengthen management, improve the skills of operators, reduce the soluble consumption is entirely possible.
Chemsta has been engaged in the turnkey and equipment manufacturing of vegetable oil and fat solvent extraction for more than 40 years, and we will share more useful technical information for you subsequently.