I. Project Overview:
The glycerol method epichlorohydrin project requires a large amount of refined glycerin as a raw material, and in the production process of biodiesel and oleochemicals, a certain amount of by-product crude glycerin is produced, so a set of glycerin refining equipment is used to carry out crude glycerin. Refining, used in the synthesis of epichlorohydrin or entering the market, can not only reduce the production cost of epichlorohydrin by 500-1000 yuan, but also bring good economic and social benefits to enterprises. Pure glycerin is a colorless and sweet viscous liquid. It is a triol with the general chemical properties of triols. It can participate in many chemical reactions and produce various derivatives. Many important physicochemical properties have become important chemical raw materials. Glycerin is currently used in China for the production of coatings, food, medicine, toothpaste, cellophane, and insulating materials.
Industrial applications
1. Used to manufacture nitroglycerin, alkyd resin and epoxy resin.
2. In medicine, it is used to prepare various preparations, solvents, hygroscopic agents, antifreezes and sweeteners, and external ointments or suppositories. Nitroglycerin for glycerol preparation.
3. Used in the coating industry to prepare various alkyd resins, polyester resins, glycidyl ethers and epoxy resins.
4. In the textile and printing and dyeing industry, it is used to prepare lubricants, moisture absorbents, fabric anti-shrinkage treatment agents, diffusing agents and penetrants.
5. It is used as a moisture absorbent and solvent for sweeteners and tobacco agents in the food industry.
6, has a wide range of uses in the paper, cosmetics, leather, photography, printing, metal processing, electrical materials and rubber industries.
7. Used as an antifreeze for automotive and aircraft fuels and oil fields. There are different refining methods depending on the use of glycerin and the consumption in the production process. In general, the purification of glycerin can be divided into distillation and decolorization purification methods, rectification and decolorization purification methods (high energy consumption), ion exchange and exclusion purification methods.
The differences between the laws are as follows:
1. Distillation and decolorization refining method: less waste is generated, investment is saved, and manufacturing cost is low.
2, distillation and decolorization refining method: the production of waste residue, high investment, high manufacturing costs.
3. Ion exchange and exclusion refining method: high investment, slightly higher manufacturing cost and large amount of wastewater. Therefore, in industrial production, industrial glycerin is produced by distillation and decolorization purification. If glycerin is used as a special purpose, such as edible, medicinal, etc., no matter which refining method is used, there must be an ion exchange process in the process to ensure that glycerol can meet the quality standards.
Second, the introduction of refining process:
According to the actual demand, the company adopts vacuum distillation and decolorization refining method. During the distillation process, the high boiling component remains in the distillation pot and is separated from the crude glycerin. The low-boiling component becomes a mixed gas mainly composed of glycerin and water vapor after gasification, and by using the difference of the boiling point of glycerin and water, the third-stage partial condensation can obtain a higher purity of refined glycerin and a lower concentration of glycerin. Sweet water (light glycerin). The refined glycerin is often pale yellow or even yellow depending on the distillation process and operating conditions, and needs to be decolorized by activated carbon to obtain refined glycerin after filtration.
Main equipment of the process;
1-crude glycerol storage tank; 2-pump; 3-distillation preheater; 4-distillation kettle; 5-cyclone separator; 6-first group condenser; 7-second group condenser; 8-third group condenser; 9-receiving tank; 10-dumping pump; 11-distilled glycerol intermediate storage tank; 12-bending pump; 13-decolorizing kettle; 14-bending pump; 15-filtering machine; 16- refined glycerol storage tank; 17-vacuum system, 18-cycle water pump; 19-heat-conducting oil furnace.
Third, the process description
Approximately 80% of the crude glycerol is placed from the storage tank into the crude glycerin feed preheating storage tank and is drawn into the distillation pot by a pressure difference (vacuum). The distillation was carried out under the conditions of a residual pressure of -0.95 – (-0.88) MPa and a liquidus temperature of 180 to 210 °C. The amount of direct steam is adjusted according to the distillation temperature and should not be too large. The glycerin vapor distilled from the distillation pot is partially condensed in the first condenser after being trapped by a vapor-liquid separator. The outlet vapor phase temperature is about 180 ° C. The first condenser uses a saturated hot water of about 140 ° C as a refrigerant, and naturally circulates between the steam drum and the first condenser shell, and partially vaporizes, and the obtained secondary steam is available. In the charge and preheat the crude glycerin. The temperature of the circulating hot water can be achieved by controlling the pressure of the steam in the drum and thereby indirectly adjusting the temperature of the glycerin vapor phase at each condenser outlet. The liquid level of the steam drum is sent from the hot water tank by the supplementary water pump, and the liquid level and the pump are interlocked. The uncondensed glycerin vapor discharged from the first condenser enters the second condenser, and the gas phase outlet temperature is controlled at about 140 ° C to condense most of the glycerin. The second condenser uses circulating soft water as a refrigerant, and the cold water temperature can be determined according to the gas phase temperature of the second cold outlet glycerin, and is generally 80 to 100 °C. The temperature of the secondary cold circulating water is controlled by a heat exchanger. The uncondensed gas discharged from the second cooling, the water vapor containing a small amount of glycerin, is recovered in the third condenser to obtain a sweet water having a slightly lower concentration, and is returned to the evaporation section or the double distillation. The gas temperature at the three cold outlets is about 50 to 60 °C. The third condenser uses circulating cooling water as a cooling medium. The amount of circulating cooling water is controlled by a regulating valve. The distillation system is pumped with a water ring pump. Water for water ring pumps requires clean low temperatures (less than 15 degrees). The refined glycerin condensed from a cooler and a secondary cooler was separately collected in a glycerin receiver. Then, it is pumped to the decolorizing pot, decolorized by adding an appropriate amount of activated carbon, and then pumped into a filter press to obtain fine glycerin. The refined glycerol is tested in the analysis room content, and the content index is adjusted according to the test result. After meeting the quality requirements of the finished glycerin, it enters the fine glycerin tank, and is metered and packaged. Third, technical improvement: In view of the problems in the production process, combined with the actual situation to make some favorable improvements, the actual operation, the effect is obvious, not only is conducive to reducing the amount of workers, but also to improve the yield of glycerol, reduce manufacturing The cost has a significant effect.
1. Due to the small size of the glycerin receiving tank and frequent discharge operations, it is necessary to continuously break the vacuum of the receiving tank and also affect the distillation system. In response to this situation, various solutions were initially implemented: changing the automatic control system to discharge, increasing the receiving tank, and vacuum discharging. By comparing and understanding the vacuum discharge scheme that finally determines the input and reduces the amount of operation, after the transformation, in addition to the manual operation of the sweet water in the initial stage, the normal distillation can be automatically discharged without manual operation.
2, the pretreatment of crude glycerin, crude glycerol contains a large number of impurities: such as oleic acid, lipids, saponification, salt, etc., before the distillation kettle to pre-treat, artificially fish and floats such as oil, smelly and difficult to fish Clean, it will affect the distillation pot, the yield is reduced, and the energy consumption is increased. The glycerin preheating pool is also easy to form salt accumulation, resulting in poor heat exchange effect, feed blocking, and parking salt clearing operation. By understanding the pretreatment method, it is determined that the mechanical separation scheme is adopted, and even if the crude glycerin is pretreated by a special machine, not only the effect of removing impurities is good, but also the manual operation is greatly reduced.
3. Sweet water recovers glycerin. It is found in production that returning sweet water directly to the distillation tank will cause the distillation discharge to be significantly reduced or paused, which will seriously affect the yield. After consulting the relevant data, the sweet water was separately treated by flash dehydration method, and the dehydration effect was ideal, so that the glycerin in the sweet water was effectively recovered.
4. Treatment of waste residue: The crude glycerin is distilled for about two days. As the high boilers in the distillation pot increase, the temperature rises and it becomes more and more difficult to steam. It is necessary to carry out slagging treatment, and each time the slag discharged is about ten tons. Because it is difficult to incinerate because it contains salt, there is currently a company that purchases oil residue, but the oil residue is required to be as anhydrous as possible. Therefore, combined with some information, the oil residue is initially treated, the salt is separated, and the organic components are sold.
Summary: Through the understanding of the problems in the production process of crude glycerin refining, continuous improvement and optimization, saving labor costs, reducing consumption, recycling of waste, making the market competitiveness of refined glycerin project continuously improve, contributing to the development of the industry, and achieved Good economic and social benefits.
