Causes of fouling of dish centrifuge and its impact on production
Abstract: Discusses the causes of dish-type off-scale in continuous oil refining process. Based on the effect of Xia off-scale on product quality, output and refining rate, finally find out the method to solve the problem of off-scale on the G.
Keywords: dish-type off-machine; fouling; cleaning; production With the advancement of technology and the improvement of people's living standards, the market demand for salad oil and high-grade cooking oil has expanded, and the production scale of oil refining manufacturers has also become larger. The oil refining process has also advanced. At present, domestic oil refineries with a daily processing capacity of more than 50 tons of crude oil generally use a continuous oil refining process. The disc centrifuge is a key equipment in the continuous oil refining process. It is used to separate grease from oil feet or soap feet to maintain the centrifuge dish The smooth and smooth separation surface of the film and the drum is conducive to the separation of the above materials. Not only can reduce the neutral oil content in the oil foot or soap foot, improve the refining rate, but also ensure the stability of product quality.
l The cause of the scaling of the disc centrifuge The separation of grease and oil feet or soap feet by the disc centrifuge is a mixture of oil and soap or phospholipids that is completed by a set of discs in the centrifuge drum and the drum. The device enters the disc group, using a thin layer separation principle to separate the oil from soap or phospholipids within each disc interval. The oil flows upward along the surface of the disc and is discharged by a small centripetal pump of light phase; soap feet or oil feet Sliding down the surface of the disc and passing through the inner wall of the drum, it is discharged by the heavy phase centripetal pump. A small amount of mechanical impurities in the oil are automatically discharged from the sliding piston and the sealing surface of the drum cover at regular intervals ⋯. After the centrifuge has been in operation for a period of time, the surfaces of the discs and the drum will be fouled. If not cleaned in time, it will not only seriously affect the separation effect of the centrifuge, but also increase the neutral oil content in the oil foot or soap foot Increased consumption; and will also reduce the output of stand-alone equipment, resulting in incomplete separation of soap feet or oil feet in the oil, affecting the quality of the product. The causes of centrifuge disc scaling are as follows:
1.1 Crude oil quality Before entering the refining workshop, different manufacturers will use different filtration processes for processing. If the filtration effect is not good, the pre-pressed crude oil will contain more oil debris, mud, etc. Impurity crude oil during hydration or alkali refining, after a period of operation of the centrifuge, impurities will be on the centrifuge disc = scaling. Although the leached crude oil undergoes treatment processes such as filtration and salting out, the crude oil still contains meal foam, phospholipids and other organic impurities. When the crude oil enters the refining workshop for hydration or alkaline refining, these impurities will also be in the centrifuge disc On the scale.
1.2 Water quality General refineries do not pay attention to the water quality of process water and operation water of centrifuges during actual production. Untreated tap water underground well water or natural water of rivers and lakes are often used. The hardness of these waters is seriously exceeded. If the centrifuge meets the normal production process temperature, after a period of continuous operation, calcium and magnesium ions in the water will be A layer of scale is formed on the disc and water channel inside the centrifuge drum, which seriously affects the separation effect of the centrifuge.
1.3 The operation of off-center machine The centrifuge does not operate normally or is not well-operated. If off the tl, the slag discharge of the machine is not complete, and the solid impurities in the drum cannot be discharged in a timely and effective manner. After a period of continuous operation, the It will cause the discs of the centrifuge to become fouled. In severe cases, the drum may even be blocked. As a result, the centrifuge cannot work properly.
1.4 Working temperature away from the centrifuge The normally operating centrifuge is at a high temperature of 9o ℃ for a long time, because the crude oil contains a small amount of impurities and phospholipids. The water contains a small amount of inorganic salts. After a long period of continuous operation of the centrifuge, these substances will foul on the centrifuge disc and water parts, and more and more, causing the separation of the centrifuge difficult. L
2 Effect of centrifuge scaling on production
2.1 After affecting the product quality, the centrifuge is fouled, the heavy phase channel is blocked, the oil and phospholipid or soap are separated by a tL, the line gradually approaches the edge of the light phase, causing part of the oil foot or soap foot to be taken out of the oil, The oil separation effect is not good, which seriously affects the quality of the product. When producing hydrated secondary oil, it often shows that the 280 heating test fails and fails to meet the national standard secondary oil standard. If refining is carried out, it will not only increase the loss of grease, but also increase the consumption of auxiliary materials; production When deacidifying oil, it often shows that the content of soap feet in the oil is too high, and it is difficult to wash. After washing, the content of soap in the deacidified oil cannot meet the production process requirements. If it is not processed, it will affect the process effect and product of decolorization and deodorization. quality.
2.2 Reduce the refining rate of the product After the centrifuge is fouled, the heavy phase and the light phase cannot be completely separated, and a large amount of oil and fat enters the soap foot or oil foot, resulting in an increase in the neutral oil content in the oil foot or electric foot, and refining consumption Increased, the refining rate decreased.
2 3 Reduce the output of the equipment After the centrifuge is fouled, its active and effective separation area is reduced. Under normal production, the output of the centrifuge will be reduced. At the same time, the heavy phase channel is blocked due to fouling. In order to ensure product quality, the back pressure of the light phase out of the centrifuge must be increased to increase the slag discharge frequency, so that the output of the centrifuge will be reduced
2.4 When the deacidified oil is difficult to wash and scale, when the centrifuge produces deacidified oil, due to the poor separation of soap feet, the content of soap in the deacidified oil is high, and the content of soap in the deacidified oil cannot be met in one wash. It must be washed twice or three times to reach the standard, which will not only cause the loss of neutral oil, but also increase the consumption of auxiliary materials and increase production costs. ,
2.5 After affecting the scaling of the equipment sealing centrifuge, other components in the drum often also foul, including the drum sealing ring and its groove. If these areas are not cleaned, it will affect the various seals on the centrifuge. The sealing of the parts leads to the abnormal operation of the equipment, and even serious damage to the seals.
3 Solutions for centrifuge fouling Some factors of centrifuge fouling are inevitable, such as hydration or alkali refining process operating temperature, crude oil contains a small amount of impurities. However, we can work hard to improve the quality of the crude oil and water quality, extend the centrifuge fouling cycle, and reduce the number of centrifuge cleanings. The main parts of the centrifuge fouling are the inner and outer surfaces of the heavy phase channel and the disc. After the centrifuge is fouled, if it can be cleaned in time, this is to a great extent. t-. It will reduce the impact of scaling on production, and will not cause the scale to be hard, resulting in no final cleaning. In order to reduce the scale of the centrifuge, first of all, the quality of the crude oil and water quality must be guaranteed; secondly, the centrifuge should be cleaned regularly according to the scale of the centrifuge
3.1 Guarantee the quality of crude oil In order to reduce the scaling of the centrifuge, the cleaning of the crude oil must be fully completed to meet the working requirements of the centrifuge, and the impurity content in the oil should not exceed o. 3%.
For the pre-pressed crude oil, due to its high impurity content, it must be fine-filtered after passing through the slag picker and the initial clearing tank. For small oil plants, plate and frame filters can be used; for large and medium oil plants, Amar filters or decanter centrifuges are generally used. In the production of domestically produced rapeseed, due to the high impurity content of the raw materials and incomplete cleaning, it often leads to more mud in the crude oil and causes difficulty in filtration. In this case, you can add filter aids to the crude oil, such as sawdust or coarse rice bran to help filter, which can not only increase the filtration speed, but also make the filter cake easy to form, easy to dry and vibrate l 3l .
For leaching crude oil, hydrocyclone or box filter is often used for initial filtration. Then, salt precipitation, evaporation and stripping are carried out. After the initial filtration, the impurity content in the crude oil is still high, which makes salting out difficult. Too much impurities will take away part of the grease and solvent, resulting in increased losses. It is recommended to use a mixed oil filter to replace the hydrocyclone or box type The filter, in this way, can not only reduce the content of impurities in the crude oil, but also avoid the scaling of the evaporator and the stripping tower.
3 2 The off-machine process and operation water use demineralized water. The centrifuge works at a high temperature of about 90 for a long time. If the process and operation water are not treated with water, calcium and magnesium ions in the water will scale on the discs and water parts of the centrifuge. For large and medium-sized refineries, separate softened water treatment equipment should be provided in the refinery. If there is no separate water quality treatment equipment in the workshop, boiler softened water and steam condensate can be used, which can save energy and guarantee The requirements of process water for centrifuges do not allow scale to accumulate on the discs and water parts and affect production.
In general, the hardness of the centrifuge water should be less than 7 British hardness, and the chloride ion content in the water should not exceed 100. , g / 1, the pH value is between 6.5 and 7.5, which exceeds the above indicators, water quality must be treated. In addition to the centrifuge drum washing water, the softening water used in the refining workshop should be softened water used for lye, dilute phosphoric acid, hydration and washing water.
3.3 Correct selection of slag discharge and flushing time In normal operation of the centrifuge, it cannot be easily shut down to open for cleaning, because cleaning takes a long time. Therefore, in order to reduce the fouling of the centrifuge in production, it is necessary to carry out a targeted flush. When flushing, the feed should be stopped first, the feed valve should be closed, the flushing water valve should be opened, and the full slag discharge button should be pressed to carry out a complete slag discharge to ease the scaling of the centrifuge. When the centrifuge is operating, choose a slag discharge cycle And instant time is very necessary. The time can be set according to the quality of the crude oil and the neutral oil content in the oil foot or soap foot during production. The general slag discharge cycle time is set at 10 rain to 20 rain, and the instantaneous time is set at 0.3 s to 0.9 s. Flushing time is set at 30 S ～ 60 s
3.4 Regular manual cleaning of off-machine according to different gross
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