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Experience promotion: improvement of soybean pressing cost system

Experience promotion: improvement of soybean pressing cost system
Soybean crushing steam consumption is an important KPI index to measure the management level of an enterprise and the improvement degree of technology and equipment. With the rapid development of oil processing industry, more and more new and expanded press oil factories have been built. Due to the reasons such as capital, scale and factory construction time, different degrees of technology and equipment exist in the enterprises, resulting in the difference of steam per unit consumption. The steam cost accounts for about 45%~50% of the total cost of soybean crushing. The high steam consumption will increase the production cost of unit product and the factory cost, so as to reduce the competitive advantage of products in the market .
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The four production lines of COFCO Eastocean Oils &Grains Industries(Zhangjiagang) Co., Ltd. (hereinafter referred to as Donghai Grains and Oils) have all been put into operation for more than 17 years, and the earliest oil pressing plant has been in operation for 23 years. The steam consumption per unit is about 20% lower than that of the newly built plant. Moreover, with the domestic policy on environmental protection is becoming more and more attention, the east China sea grain and oil steam supplier (near the thermal power plant) has gradually been out using coal stove for many years to use natural gas boiler, gas boiler cost is higher, thermal power plant is gradually adjusted ex-factory price of steam (or 80%), grain and oil in the east China sea oil production cost impact is bigger, the pressure surge. The unit price of steam is an external uncontrollable factor (there is only one supplier around). To solve the problem of processing cost, it is necessary to start from the steam unit consumption. To this end, the Eastocean Oil Plant has conducted key research in many aspects such as equipment selection and structure, process waste heat recovery and utilization, on-site management and maintenance.
The main methods and highlights of innovation
1. To optimize equipment selection and structure
1. Improve the heating method and increase the utilization of heat energy
The conditioning tower is the equipment used in the pretreatment workshop of the oil crushing plant for the conditioning and softening of soybeans and rapeseeds. Its working principle is to use indirect steam to heat the soybeans and rapeseeds to achieve softening. The equipment uses a large amount of steam, accounting for about 25% of the soybean squeezed steam consumption. The heating tube of the conventional quenching and tempering tower is elliptical, and the steam enters the pipeline to heat the oil outside the tube wall, and the heat exchange area per unit volume is limited. The Eastocean Oil Pressing Plant introduced a new type of high-efficiency plate heating device, which is placed on the top of the quenching and tempering tower, and uses steam condensate to preheat the oil. The heating area per unit volume of the plate is twice that of the oval tube, which can effectively improve the utilization rate of heat energy and reduce steam consumption.
The same type of crude oil tubular heat exchanger in the leaching workshop can also be used to improve the heat exchange efficiency. It should be noted that the channel of the plate oil exchange circuit is relatively small, and the mixed oil contains impurities, which is easy to block the channel. It is necessary to further filter and purify the mixed oil.
2. Equipment specification modification for supporting capacity
Based on the original design, the production lines of Eastocean grain and oil pressing plants have been upgraded to varying degrees, but the evaporation system and soybean meal desolvation and drying system in the leaching workshop have not been upgraded, resulting in many problems, such as short residence time of materials in the equipment, insufficient heat exchange area of the evaporation system, incomplete utilization of waste heat of secondary steam and so on, Fully investigate the relationship between equipment specifications and production capacity. Eastocean oil refinery has improved the specifications of DTDC, first steam and other equipment to match the production capacity and greatly reduce the steam consumption.
At present, large-scale molding oil pressing plants basically use n-hexane solvent to extract oil from oil crops. The wet soybean meal and mixed oil after oil extraction need to remove the residual solvent before they can leave the factory safely. DTDC is a wet meal desolvation and drying equipment in oil press plant. Its working principle is that the wet soybean meal containing solvent is fed layer by layer from the top of the equipment, and the residual solvent in the wet soybean meal is volatilized with the heating effect of steam in the feeding process. After the workshop capacity is increased, the material flow per unit time increases and the residence time in DTDC is shortened, which is not conducive to solvent volatilization and needs to consume more steam. By adding a desolvation layer in the soybean meal desolvation section, Eastocean oil press plant can prolong the material residence time and effectively improve the utilization rate of steam heat energy (too long heating time and too high temperature of soybean meal are easy to lead to protein denaturation and low protein solubility of soybean meal. This transformation needs to be fully considered in combination with steam consumption and protein solubility). The solvent gas volatilized by DTDC is used as an important heat source of the evaporation system to fractionate the mixed oil (according to the boiling point of solvent and oil). The primary steam heat exchange area after extraction is small, so it cannot make full use of the heat source. Similarly, the equipment specification is improved
3. System replacement, low cost instead of high cost
The vacuum of the mixed oil evaporation and condensation system and the vacuum of stripping in the leaching workshop of conventional oil extraction plant are powered by steam, which can be replaced by mechanical vacuum pump (after a comprehensive evaluation of the cost comparison between power consumption and steam consumption).
4. Automatic improvement and precise control
In the pressing process, the amount of steam in some production sections needs to be adjusted according to different process conditions. In order to ensure the quality of products, the steam is often turned up when the manual adjustment is made, which leads to excess product quality and steam waste. The accuracy and timeliness of the adjustment are insufficient. It is an effective method to reduce steam consumption to introduce automatic control valve in the process, which is interlinked with process temperature, moisture content and other data to realize automatic control.
2. Process waste heat recovery and utilization
The hot oil, condensed water, waste water, exhaust gas, etc. leaving the workshop entrain heat for heat recovery. In recent years, the hot air discharged from the DC and the hot air discharged from the expansion cold-dry box have been recovered for heat energy, and the flash steam of the steam condensate tank has been used to reduce the steam consumption.
The exhaust gas from the expansion system and soybean meal drying system of the oil extraction plant has high humidity, high temperature and high latent heat. Meanwhile, the exhaust gas has special odor (bean smell, meal smell, alkane aromatic hydrocarbon smell). The concentration of the odor when directly discharged without treatment exceeds the allowable emission concentration of the national standard. In addition, when equipment failure occurs, there will be meal powder blown into the atmosphere, which does not meet the emission standards of particulate matter.
In the exhaust gas treatment plan, cooling is an important means to remove peculiar smells. In combination with peculiar smell treatment, dust treatment and waste heat utilization, the Eastocean oil pressing plant has implemented a “wet capture and waste heat utilization” technical transformation program. The first step of the scheme is to wet capture the exhaust gas from the outlet of cyclone. On the one hand, the water mist through the mist nozzle captures the solid particles in the exhaust gas, and on the other hand, transfers the exhaust heat to the trap during the capture process. In the water. Then the captured water is exchanged with the cold air at the air inlet of the equipment to achieve the improvement effect of "dust removal, odor removal, and waste heat utilization".
3. On-site management and maintenance
Poor site management and leakage of steam and condensate will inevitably affect steam consumption. Whether the safety valves, pressure regulating valves, and pressure relief valves working in the workshop are working properly, the relevant instruments need to be adjusted regularly. The heat exchange surface of the heat exchanger needs to be inspected and cleaned regularly. If there is fouling, it will affect the heat exchange effect. The steam trap is checked regularly to see if there is internal leakage and whether it is working properly. Surface insulation of traps, steam valves, and thermal equipment
Project benefits
After the implementation of the project, the unit consumption of soybean pressing steam of the fourth Eastocean oil pressing plant has decreased by about 20%, and the economic income has reached 7.75 million yuan / year
It can be popularized and applied
The continuous production line built or reconstructed in the press industry can learn from the equipment and process of the project to optimize the design. 
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