What is the principle of waste tire refining?

New oil refining technology of tire thermal decomposition

The core technical principle of waste tire oil refining is the new technology of thermal decomposition of waste tire oil refining. Tires are mainly composed of rubber (including natural rubber, synthetic rubber), carbon black and a variety of organic and inorganic additives (including plasticizers, antioxidants, sulfur and zinc oxide, etc.), most organic compounds have thermal instability characteristics, if it is placed under hypoxia, high temperature conditions, under the joint action of decomposition and condensation, macromolecular organic compounds will crack. The chemical transformation of organic matter into gaseous, liquid and solid components with relatively small molecular mass is called thermal decomposition.
Technical principle of waste tire oil refining
The thermal decomposition of waste tire is a complex and continuous chemical reaction process, including the breaking of macromolecular bond, isomerization and condensation of small molecules, and finally the formation of smaller molecules. In the process of thermal decomposition, there are two kinds of changes in the intermediate products: one is the pyrolysis process from large molecules to small molecules until they become gas; The second is the process of polymerization from very small molecules to larger molecules. There is no clear stage of this reaction, and many reactions are carried out in a crossover. The thermal decomposition process of tires can be expressed by the following formula: organic solid waste → gas (H2, CH4, CO, CO2) + organic liquid (organic acids, aromatics, tar, kerosene, alcohols, aldehydes, etc.) + solid (carbon black, slag).
Waste tire oil refining process thermal decomposition of waste tire oil refining
The essence of thermal decomposition of waste tires is to heat organic macromolecules to crack them into small molecules. In this process, the reaction of different temperature ranges is different, the composition of the product is different, the composition of organic matter is different, and the starting temperature of the entire thermal decomposition process is also different, which leads to the thermal decomposition process is complicated and the temperature is strictly controlled. The thermal stability of organic matter depends on the formation of the bonds of the atoms of the constituent molecules and the size of the bond energy, the bond energy is large and difficult to break, and its thermal stability is high. The bond energy is small and easy to decompose, and its thermal stability is low. The yield of tire thermal decomposition products depends on the chemical structure and physical form of raw materials and the temperature and rate of pyrolysis.
Process flow of tire thermal decomposition oil refining equipment
The process flow of tire thermal decomposition oil refining equipment is divided into multiple stages according to the chemical reaction process mentioned in the tire cracking principle, and the specific process flow is described as follows:
1, the thermal decomposition temperature range of 0~120℃ : open the equipment exhaust valve, so that the air in the furnace is slowly discharged, to achieve the anaerobic conditions of the pyrolysis process. Since the pyrolysis process has just started, waste tires need to undergo heat absorption and heat transfer process, which requires slow heating at this stage, generally at the rate of 2K/min. When the temperature reaches about 120 ° C, it will be found that the temperature in the furnace is maintained for a period of time, and there will be no significant warming phenomenon, at this time, the waste tire begins to absorb heat, the thermal decomposition reaction process gradually begins, and the pyrolysis gas and oil begin to produce. This phase usually lasts about 2 hours.
2. When the temperature range of thermal decomposition is 150~380℃, the drain valve is closed and the products such as oil and gas generated by pyrolysis are collected. The high-temperature oil and gas enter the buffer tank to buffer the flow rate of oil and gas; Then through the condenser condensation, and finally collect the oil in the tank; The resulting combustible gas is connected to the combustion chamber to provide heat for the pyrolysis process. In order to prevent the thermal decomposition process of the tire from being too intense, this stage still needs to be slowly heated, which generally takes about 4 hours. In order to prevent the combustible gas from burning too fast, resulting in too high a heating rate, it is necessary to carry out flow control and store the excess combustible gas for the next stage of the pyrolysis process.
3, when the thermal decomposition temperature range is 380℃ constant temperature reaction process: the pyrolysis process at this stage is similar to the second stage, and the above process is still carried out. At this stage, the production of combustible gas gradually decreases, and when the calorific value provided by combustible gas is insufficient, it is necessary to supplement biomass fuel to maintain the heat of the pyrolysis process. This phase usually takes about 2 hours.
4, thermal decomposition to complete the cooling stage: in this process to stop heating, the project adopts the method of air cooling, through the fan to continuously take away the heat of the furnace wall, the cooling section lasts about 5 hours. At this time, the carbon black screw conveyor is started to collect the pyrolytic carbon black. After the collection of carbon black, open the drain valve above the furnace body, restore the normal pressure in the furnace, open the tank, and automatically unload the pyrolysis wire under the action of the spiral on the furnace wall. This stage generally takes about 2-4 hours, and then the new waste tires are loaded, and then the above pyrolysis process is carried out, and the production of one furnace after another is completed in batches.
Since the tire feed is the whole tire, there is no cutting and crushing section, the furnace body keeps rotating during the cracking process, so the steel wire is twisted together during the discharge, and a small amount of carbon black on the steel wire can be dropped by tapping, and the steel wire is directly packaged and transported after discharge. Then close the steel wire outlet, open the carbon black outlet, docking with the closed spiral slag machine, carbon black directly into the packaging bag after discharge, weighed by the scale after packaging factory. The carbon black steel wire discharge time of each equipment is 2 hours, and the total time of the entire tire thermal decomposition oil refining process is 20 hours.