Semi coke is also known as low temperature coke. Gray-black, volatile matter (about 7%-12%) is higher than that of coke (about 3%), the texture is crisp and porous, the reaction performance is good, it is easy to burn, and it is smokeless. The solid product of coal dry distillation at low temperature (500～600℃). It is used to make producer gas and water gas, and can also be used as fuel . The ash content depends on the raw material coal quality, and the volatile content is about 5% to 20% (mass). Compared with coke, it has high volatile content, high porosity and low mechanical strength. It has strong reactivity with carbon monoxide, steam or oxygen. It is a good smokeless fuel with high calorific value. It is mainly used as industrial or civil fuel. It is also used in the production of synthesis gas and calcium carbide. A small amount is used as a reducing agent in the smelting of copper or phosphate ores. In addition, it is also used as a coking coal blending agent. Generally, semi-coke is also a by-product or intermediate product in the process of converting coal into liquid and gaseous fuels. Therefore, the production of semi-coke and coal gas through low-temperature dry distillation of rich, high-volatile coal is an important part of the coal conversion process.
Semi-coke is black to dark gray in appearance, matt, soft and brittle, with open pores, its strength is worse than that of high-temperature coke, and its apparent density and true density are also lower than that of high-temperature coke. The volatile content of semi-coke varies with the final temperature of dry distillation, generally 10-20%. Semi-coke is easy to catch fire and has high reactivity. Semi-coke reactivity is generally measured by the critical air blast method. The smaller the measured value, the greater the reactivity. The critical air blast volume value of semi-coke averages 0.017L/min, while high-temperature coke can reach 0.057L/min. The high volatile content of the semi-coke increases the reactivity and reduces the ignition temperature. Semi-coke has a larger specific surface area, and some of its adsorption performance can be close to activated carbon or carbon molecular sieve. The properties of semi-coke depend on the properties of raw coal, dry distillation equipment and dry distillation process, mainly the dry distillation temperature and time.
There are many types of semi-coke production equipment. Dry distillation equipment can be divided into two categories: external heating and internal heating. External heating type dry distillation equipment is to pack coal in a ceramic or metal kiln and heat it from the outside. Due to the poor thermal conductivity of coal, in order to improve heat transfer, methods such as stirring, rotation and multi-layer heating are also used, and the mechanism is relatively complicated. Internal heating type dry distillation equipment uses gas heat carrier or solid heat carrier to directly contact with coal for heating. The coal is rapidly heated by the heat carrier in a moving bed, fluidized bed or carrier bed and dry distilled into semi-coke.
The main uses of semi-coke are: (1) Used as fuel for civil or industrial use. The semi-coke is moderate in size, easy to ignite, and smokeless when burned. It is widely used as a civilian fuel in Europe. Semi-coke with powder and volatile content <20% is suitable for boiler fuel. Semi-focus Semi-focus (2) Used as a coal blending additive for high-temperature coking. Semi-coke has low strength and high reactivity, and cannot be directly used in blast furnaces and iron furnaces, but it can be used as a thinner for coking coal blending and used to produce metallurgical coke. (3) Preparation of shaped block or shaped coke. When high volatile non-caking coal is used to produce briquette or briquette, it must first be refined into semi-coke. (4) Others. Used as a reducing agent in the production of phosphorus and copper; semi-coke with a volatile content of 8-20% can be used as electrode raw material after pulverization and calcining; bulk semi-coke can be used as gasification raw material; low-ash semi-coke can be used after activation treatment Activated carbon; powdered semi-coke is used as fuel for blast furnace injection; lignite semi-coke that has been treated with alkali can be used instead of charcoal in the production of CS2.