The production process of the leaching plant is divided into five main sections, namely, material leaching, mixed oil desolvation, wet meal desolvation, solvent recovery and tail gas treatment.

Solvent Recovery

Solvent recovery mainly involves two solvent sources: DTDC evaporator and evaporation system. ①Solvent recovery from DTDC evaporator and stripper

DTDC evaporator has a large pipe at the top, called the gas phase pipe, is the steam and solvent mixture in the evaporator gas discharge channel. Because the mixed gas contains a certain amount of meal, so the lowest position in the gas phase pipe is generally set up a manhole to facilitate maintenance to clean up the meal deposited inside. Because the manhole can not be opened several times a year, and the gas mixture contains steam condensate will also be deposited here. Therefore, every time you open the manhole to clean up the meal when the odor is quite acidic, I believe that people who have cleaned up the memory is very deep.

The temperature of the gas mixture is generally around 80 ℃, and the heat is huge, if it can be utilized, will greatly save steam consumption. Therefore, it can be used for a steam mixture to warm up the oil. However, in order to avoid the mixed gas contained in the meal into a steam shell process in the adherence to the outer surface of the column tube to affect the heat transfer efficiency or reduce the shell space to increase the resistance of the mixed gas flow and affect the negative pressure of the DTDC steam off the machine, when serious, resulting in a steam shell process of the clogging, generally need to be mixed gas in the meal to capture down. Capture meal end of a variety of ways, I met more is the wet capture method, that is, the use of wastewater cooking tanks in the hot water through the nozzle uniformly sprayed to the mixed gas, meal end by the water captured to the wastewater tank, clean mixed gas into a steam shell process to the mixed oil heat exchange. With the wet capture method is the opposite of the dry capture method, that is, with the solvent liquid at room temperature to capture. Each method has its advantages and disadvantages, which are not described in detail here. After heat exchange, a portion of the gas mixture is not condensed to a liquid, but is passed into a condenser to be cooled to a liquid by circulating water. After heat exchange or cooling into a liquid mixture of liquid into the water separation tank after the solvent liquid recycling, but there will still be a small amount of solvent gas is not condensed down, this part of the gas will enter the tail gas system for recycling. Tail gas fan can make the tail gas treatment system and the equipment connected to it, such as condenser are in a slightly negative pressure state, can provide power to the gas flow. ②Solvent Recovery from Evaporation System

Leached mixed oil contains a large number of solvents, after a steam, two steam and steam extraction, leaching oil in the solvent content has been reduced to very low. Qualified leaching oil solvent content is generally less than 100 ppm. after vaporization by the evaporation system, the solvent enters the condensation system, and cooling water heat exchange into the condensate and flow into the water separation tank water, water solvent is recycled again.

Vacuum pump will condensing system and evaporation system in the gas pumping so that its internal negative pressure state, the solvent evaporation into a gas that is beginning to move back and into the condenser in the shell process (the outer wall and the space between the tubes is called the shell process), while the condenser tubes (referred to as the tube process) is passed into the cooling water, the solvent in the shell process of the gas and the condensate through the process of the condensate through the exchange of heat, the solvent gas loss of heat condenses into a liquid and into the water distribution tank after water recycling, the cooling water in the tube process will be from the heat obtained from the solvent gas brought to the cooling tower to cool down and then cycle heat exchange. Liquid and into the water distribution tank after recycling, the cooling water in the tube course will be from the solvent gas in the heat to the cooling tower to cool down and then recirculate heat exchange. Because a steam two steam no direct steam, and the temperature is not too high, so its heat recovery value is not high, but the solvent gas volume is relatively large, so a steam and two steam out of the solvent gas merged into a larger heat transfer area of the condenser can be directly condensed. Stripping tower out of the amount of solvent gas, although very small, but the stripping of a large number of direct steam, steam temperature is high, and contains more heat, has a very considerable recycling value, if it is directly cooled down condensation will result in a waste of heat, according to the needs of the first and need to be warmed up with the material for the heat exchange (need to have a large enough temperature difference to work), and then into the condenser for cooling and condensation. The condenser can then be used for cooling and condensation. In addition to the above two main sources of solvents to be recovered, the solvent free gas produced by the leachers and condenser non-condensable gas in a certain amount of solvents need to be recovered. These two parts of the solvent recovery and the next section of the tail gas treatment combined introduction, here for the time being.

What are the factors affecting solvent loss in a leaching plant?

Original Oil Mill Artist Oil Mill Artist September 09, 2024 19:45 Henan

Solvent is recycled in the oil leaching process, but due to a variety of reasons will cause solvent loss in recycling. The amount of solvent consumed per ton of material processed in the leaching production process is called solvent unit consumption. Solvent consumption is a very important indicator in the leaching production process, which directly affects the safety of the leaching plant, the working environment, product quality and production costs, etc. A large solvent consumption is also not conducive to environmental protection. Leaching workshop solvent loss mainly comes from the following aspects: ① wet meal evaporation residual solvent (not finished meal solvent content, why?); ② mixed oil evaporation vapor; ② mixed oil evaporation vapor; ③ solvent content, why? ② residual solvent in the leaching oil after the evaporation of mixed oil vaporization; ③ residual solvent in the water discharged from the wastewater tank after cooking; ④ residual solvent in the exhaust gas discharged after condenser condensation; ⑤ solvent leakage in the production and maintenance process. According to the characteristics of solvent loss, it can be divided into two categories, i.e. unavoidable solvent loss and avoidable solvent loss.

Under the current oil leaching technology, the complete recovery of solvent in leaching production is impossible, that is, there is always a small amount of solvent unavoidably lost in leaching production. Usually the minimum amount of solvent loss under good normal production conditions is called unavoidable solvent loss. The first four aspects of solvent loss mentioned above are the main causes of unavoidable solvent loss.

The amount of unavoidable solvent loss depends on the selected production process, the structural performance of the equipment, the type and nature of the leach material, the composition and nature of the solvent used, the level of worker operation, production scale and other factors. Leaching material structure and performance of different, in the same leaching production conditions of the solvent loss is different. If the leached material powder degree is large, high moisture, solvent permeability through the material layer is poor, after leaching meal in the residual oil rate and wet meal solubility are increased, wet meal evaporation effect will be reduced, resulting in high solvent residue in the finished meal. Factors affecting the leaching effect and the desolvation effect of DTDC evaporation machine can be referred to

The basic principle of oil leaching process and the factors affecting