The composition characteristics of lubricant solvent dewaxing are the same as the overview of the process flow
{1} Composition characteristics of solvent dewaxing equipment
The solvent dewaxing device consists of five units, namely the crystallization unit; Dewaxing filtration, first stage oil removal filtration, and second stage oil removal filtration units; Recovery and drying dehydration units for filtrate, wax liquid, and solvent under wax oil; Ammonia refrigeration unit; Vacuum sealed unit.
The device uses a binary solvent of methyl ethyl ketone and toluene for dewaxing and oil removal.
The 400000 t/a solvent dewaxing unit uses 8 million t/a distillation unit to reduce the third line distillate oil as raw material, and produces 54 # or 56 # paraffin products after processing. Crude oil is a mixture of Shenbei crude oil and Daqing crude oil in a certain proportion.
In order to improve the yield of deoiling wax, the device first determined an adjustment direction, which is to use the remaining refrigeration capacity after the device does not control the dew point of the deoiling oil, transfer the cooling capacity to reduce the filtration temperature of the feed in the first and second stages of deoiling, and reduce the loss of low melting point paraffin components in the raw materials;
Solvent dewaxing simultaneously utilizes the influence of solvent composition on the crystallization state of wax, controls the optimal ratio, and achieves optimal wax crystallization state. Therefore, adjusting the solvent composition is beneficial for both improving wax yield and meeting product wax oil content standards.
In the process of device adjustment, in order to reduce the filtration temperature of the first and second stages of oil removal, and considering the fact that the solvent used in the dewaxing section of the device has a large refrigeration capacity while the solvent used in the first and second stages of oil removal has a small refrigeration capacity, in order to fully utilize the excess refrigeration capacity of the dewaxing section, the device was adaptively modified by adding a pipeline to replace all the cold washing solvents in the oil removal section with low-temperature solvents in the dewaxing section, transferring the refrigeration capacity of the dewaxing section to a part of the oil removal section, and achieving a reduction in filtration temperature in the oil removal section.
{2} Overview of process flow for ketone benzene dewaxing unit
Ketone benzene dewaxing is the main equipment of ketone benzene dewaxing equipment, and the current development trend abroad is towards large-scale and increasingly rational structure. The inner tube diameter of ketone benzene dewaxing in the United States has developed from 152mm to 304mm. The use of large diameter ketone benzene dewaxing with a scraper has the following advantages: ① low pressure drop, slow cooling speed, and energy saving; ② Reliable operation with low failure rate; ③ The use of multi-point dilution and rapid cooling methods can effectively utilize energy. In recent years, most of the cooling tubes in domestic devices have been replaced with large tubes with a diameter of 203mm imported and manufactured domestically, and a small number of ammonia cooling tubes have also been replaced with large tubes, resulting in significant economic benefits.
One of the important methods for refining petroleum products is to dilute and freeze lubricating oil raw materials through solvents, causing wax crystals to precipitate, thereby reducing the freezing point of lubricating oil. In industry, lubricating oil obtained from crude oil distillation of waxy crude oil is fractionated, and after solvent refining, solvent dewaxing of lubricating oil, and hydrofining with kaolin refining, lubricating oil base oil rings and paraffin can be produced; If vacuum residue from crude oil distillation is used as the raw material, lubricating oil base oil and ground wax can be produced through solvent deasphalting, solvent refining, ketone benzene dewaxing, and hydrogenation refining processes.
Ketobenzene dewaxing is an extremely important step. The ketone benzene dewaxing device is divided into four systems: ① The basic task of the crystallization system is to form good wax crystallization. By utilizing the different solubility of oil and wax in the ketone benzene solvent in the dewaxing raw material, cooling is carried out to gradually form crystals and precipitate the wax, thereby creating conditions for oil wax separation; ② The basic task of the refrigeration system is to ensure product quality, provide necessary cooling capacity, use ammonia as the refrigerant, and use the vaporization and heat absorption characteristics of liquid ammonia at low temperatures to cool the dewaxing raw materials and solvents. After the liquid ammonia absorbs heat, it vaporizes and is compressed into high-pressure gas ammonia by a refrigeration machine. After being cooled and condensed by dry and wet air cooling, it liquefies and is then throttled and enters the evaporator for recycling The basic task of a vacuum filtration system is to complete the separation of oil and wax, and provide inert gas sealing to the container and vacuum filter. According to the wax content of the raw material, one or two stages of filtration are used to recover solvents from the filtrate and wax, both using multi effect evaporation and stripping to reduce energy consumption. In addition, inert gas protection systems can reduce solvent loss and prevent explosion, ensuring safe production.
