What is coal tar?
The black or dark brown viscous liquid is produced by coal distillation with a pungent odor, referred to as tar. Coal tar is generally used as a raw material for processing and refining to make a variety of chemical products but also can be directly used, such as industrial briquette, coke, and coal activated carbon binder ingredients, can also be used as fuel oil, blast furnace injection fuel and wood anticorrosive oil and charcoal black raw materials.
According to different pyrolysis temperature, it can be divided into low temperature (450°C~650°C) dry distillation tar, low temperature and medium temperature (600°C~800°C) furnace tar, medium temperature (900°C~1000°C) vertical coal tar, high temperature (1000°C) coking tar. The crude tar is the gas produced in coking, which is sprayed with circulating ammonia water and cooled with condensation in the primary cooler for recovery. It contains a lot of water, about 4% of water, sometimes up to 8-10%.
Formation and recovery
In air chamber heating furnace charging coal volatile precipitation when, through the coke cake and the space between the chamber wall and cracks, hot coke, carbocoal itself in coal and aggregate into the roof space, in 700 ~ 850 ℃ high temperature secondary pyrolysis reaction (paraffin cracking and aromatization reactions, naphthene dehydrogenation reaction, phenols, dehydration, condensation reaction, etc.) to take off the alkyl aromatic and heterocyclic compounds.
These gaseous coal retorting products around 700℃ are carried with coal dust, coke dust and pyrolysis carbon, and enter the collecting pipe through the rising pipe. They are quenched to 70 ~ 80℃ by circulating ammonia water.
In the collecting pipe, most coal dust, coke, pyrolytic carbon and some coal tar with high boiling point are condensed and washed down.
The remaining fog-or vapor-state coal tar is gradually condensed and separated in the coke oven gas primer and subsequent gas purification plant.
The coal tar separated by condensation is collected to the tar ammonia water separator, and the ammonia water and tar residue are preliminarily removed to separate the coal tar.
The yield of coal tar is 3 ~ 4.5% of dry coal mass in high temperature distillation.
Principle of coal tar decanter separation
The decanter centrifuge’s working principle is that the coal tar mixture (suspension) enters the bowl through the feed tube and the screw conveyor.
Under the centrifugal force generated by the high-speed rotation, the separation is generated due to the density difference of different components in the feeding material.
Solid particles (cinders) are accumulated on the bowl’s inner wall and are scraped continuously off and pushed out by the screw.
Tar and ammonia phase form concentric rings: light phase liquid (ammonia) in the innermost layer of the bowl, heavy phase liquid (tar) in the outer layer of the bowl, through the opening of the regulating plate overflow out of the bowl respectively.
The separation of advantage
Compared with other traditional separation methods, the ZK Coal Tar Decanter Centrifuge has the following advantages for coal tar treatment:
- 1. High production efficiency: it can achieve a high capacity of processing coal tar, and the treated coal tar can directly enter the storage tank, which improves production efficiency;
- 2. Minimum maintenance: The feed is automatically imported into the equipment by the coke oil pump, and the oil, water, and slag after treatment are continuously discharged and transported without manual operation. The entire slag removal and dehydration process is an automatic treatment process, which significantly reduces the labor intensity of workers;
- 3. Clean working environment: ZK Coal Tar Decanter Centrifuge occupies a small area, and the supporting equipment is simple, the whole work process is completely closed, will not cause pollution to the workshop, easy to manage;
- 4. High degree of automation in the production line: the whole process flow of ZK Coal Tar Decanter Centrifuge can realize automatic control of dehydration and slag discharge. The PLC system can control the entire dehydration workshop to form an automated production line conveniently.