Semi coke production process

The semi coke is named for its blue flame when it is burned. When the semi coke is produced, coal tar and coke oven gas are by-produced. Coke production is mainly high-temperature dry distillation; semi coke production is mainly low-temperature dry distillation.

There are mainly three types of low-temperature dry distillation furnaces suitable for semi coke production: SJ low-temperature dry distillation square furnace,TDM segmented lump coal low-temperature dry distillation furnace, and ZDM  low-temperature dry distillation furnace.

 SJ low-temperature dry distillation furnace

SJ low-temperature dry distillation square furnace is based on the original three-stage furnace, inheriting the technical advantages and production practical experience of internal heating vertical cubic furnace and SJ reheating vertical carbonization furnace. Moreover, it has absorbed the advantages of domestic and foreign furnace types, and developed a new type of furnace based on the coal characteristics of high volatile content, low ash melting point and high oil content in the coal fields of Yulin, Shenmu, Fugu and other places. This furnace type has the characteristics of  material fall evenly,  uniform gas distribution, uniform heating, etc., which truly realizes the low-temperature dry distillation of coal. At the same time, the effective volume of the coke oven is increased.

TDM type segmented lump coal low-temperature dry distillation furnace

Overview: This equipment is used for low-temperature dry distillation of bituminous coal with a particle size of 25~100mm. The main products are semi coke, coal tar and coal gas. It has the following characteristics:

(1) Drying, dry distillation and cooling are carried out in stages. The coal gas is drawn from the dry distillation section, which prevents the flue gas used for drying  being mixed into the raw gas, which is beneficial to improve the recovery rate of coal tar and the quality of coal gas.

(2)  Flue gas is used for dry hot air distribution, which not only reduces fuel consumption but also ensures the quality of lump coal.

(3) The purified gas will not burn the carbon in the semi coke, and will not decompose the tar vapor.

(4) The coal gas used for air distribution exchanges heat with the carbonized semi coke before the air distribution, so that part of the heat is recovered and the temperature of the semi coke is also reduced.

(5) It avoids the disadvantages of steam to  decompose tar steam and high water content of semi coke .

(6) The feeding system adopts double gates was sealed.

(7) The discharging system adopts three gates was sealed , and thus control the production speed of the whole system.

(8) The raw gas outlet is at normal pressure, the inside of the sealed feed is negative pressure, and the inside of the sealed discharge is positive pressure. The pressure difference between the drying section and the retorting section, and between the retorting section and the cooling section is zero to avoid short circuit of air flow.

•In fact, the raw gas outlet is slightly positive pressure, and the specific pressure can be adjusted on site.

• The lower part of the drying section is slightly larger than the upper part of the dry distillation section, which not only ensures that the gas does not leak, but also helps the lump coal to supplement heat during the process of uniform temperature.

• The lower part of the dry distillation section is slightly larger than the upper part of the drying section, so that a certain amount of heat can be added during the heat preservation of the semi coke. The pressure  should be controlled between 30 and 50 Pa.

(9) Dedicated hot air system and burner.

ZDM type low temperature dry distillation furnace

(1). Overview: This equipment can be used for lignite low-temperature dry distillation projects to further carry out low-temperature dry distillation of lignite that has been dried at 250 degrees. The main products are semi-coke ,coal tar, and gas for self-use. It has the following characteristics:

•External heating: This will help increase the tar recovery rate of the system and reduce the raw gas purification capacity.

•It can achieve low-temperature dry distillation at 500~600℃.

•Dry coking.

Structural features and process characteristics:

• This device is separated from the drying, so that raw gas no longer enters the drying system.

•The principle of dry distillation temperature is that the gas produced by the system is just enough for the system to burn, and its benefits is that there is basically no surplus gas, and there are few harmful substances in the raw gas, which simplifies the subsequent gas treatment process of the project.
Production characteristics of blue charcoal

1. There are many flammable, explosive and toxic substances produced in the production process.

2. There is a lot of dust and smoke in open-air operations.

3. The production process conditions are harsh

The general process of production

Semi coke has high fixed carbon and can be used as heat, reducing agent and carburizing agent in the blast furnace to replace coke to save coke and reduce consumption. The low ash and low sulfur characteristics of semi coke have a good influence on improving blast furnace output, reducing coke ratio, and reducing desulfurization energy consumption. The high reactivity of semi coke not only plays a good role in protecting large coke, but also in reducing carbon consumption, gas permeability of the blast furnace, the reduction rate of iron ore, and the production capacity of the blast furnace.The entry of semi coke into the iron and steel smelting industry is great significance for saving coke and reducing consumption, improving quality and efficiency in iron and steel smelting, and alleviating the increasingly scarce coking coal resources. In recent years, the smog weather in many cities in China is closely related to coal burning. As an environmental friendly fuel, semi coke has better indicators than coal and anthracite. Its wide application can reduce the emission of harmful substances and improve air quality. The semi coke is the first choice to reduce air pollution and control haze weather.

The production of semi coke is mostly based on low-temperature dry distillation. The dry distillation temperature is generally around 600°C. It takes about 1.7 tons of lump coal to produce 1 ton of semi coke. Due to the late start, the current annual output of semi coke low-temperature dry distillation furnace equipment is mostly around 30,000 tons/year, and low-temperature dry distillation furnace equipment with a scale of more than 50,000 tons/year is still in the stage of exploration and testing. The technology of large-scale equipment  is still immature, and only one furnace with multiple doors and other combined technologies can be used to achieve centralized mass production.After the raw coal is crushed in the second stage, the lump is 20-80mm, and it is sent to the coal storage bunker above the retort furnace through the coal conveying belt. The coal feeder adds the coal lump according to the processing capacity of the retort furnace, so that the top of the furnace does not lose material. The raw coal gradually descends in the dry distillation furnace, passes through the drying section, the dry distillation section and the cooling section in turn, and finally is pushed down to the quenching tank by the coke pusher, and the semi coke is sent to the dryer for drying through the scraper.