Low-rank coal drying method and system

Abstract

The invention discloses a method for drying low-rank coal, which comprises the following steps: (1) the low-rank coal is crushed, and the arrange of a grain diameter of the crushed low-rank coal is between 3 and 50mm; (2) the crushed low-rank coal is sent into a dryer and contacts hot flue gas which comes from a hot flue gas generation device; (3) the low-rank coal which comes out of the dryer is collected, and the hot flue gas discharged by the dryer as well as coal powder and water vapor which are carried by the hot flue gas are aerated into a coal powder treatment and acquisition system at the same time; (4) at least partial coal powder collected by the coal powder treatment and acquisition system is sent to the hot flue gas generation device to serve as a combustion material; (5) the hot flue gas which comes out of the coal powder treatment and acquisition system is divided into two parts, wherein the first part of flue gas circularly returns to the hot flue gas generation device, and the second part of the flue gas is discharged after heating combustion air through an air pre-heater; and (6) the heated combustion air is conveyed to the hot flue gas generation device to take part in the combustion. The invention also provides a low-rank coal drying system with self-supplied fuel, which has the advantages of high energy utilization rate and low production cost.

Description

technical field [0001] The invention relates to a coal drying method and system, in particular to a low-rank coal drying method and system. Background technique [0002] my country's energy resources are dominated by coal, and coal consumption accounts for about 60% of my country's primary energy consumption. For a long time, bituminous coal and anthracite have been the main sources of mining and utilization of coal resources in my country. With the continuous increase of my country's energy consumption and the excessive exploitation of bituminous coal and anthracite, the development and utilization of low-rank coal is becoming more and more important. [0003] The so-called low-rank coal refers to coal with a lower degree of coalification, such as lignite, long-flame coal, non-caking coal, weakly caking coal and gas coal. Low-rank coal accounts for a considerable proportion of my country's proven coal reserves, but due to the high moisture content (usually 20wt% to 60wt%)...

AI Technical Summary

Problems solved by technology

[0007] (1) During the working process of the coal-fired hot flue gas generator in the drying system, the fuel is in a state of adiabatic combustion. If coal with a lower ash melting point is used, the temperature of the hot flue gas generated by combustion is usually higher than that of the ash The slagging temperature is prone to slagging phenomenon, therefore, coal-fired hot flue gas generators usually use high-quality bituminous coal that is not easy to slagging, which will inevitably increase production costs

[0008] (2) The hot flue gas generating device of the current drying system mostly adopts the method of directly mixing cold air for temperature adjustment to meet the appropriate temperature required for drying materials, which makes the thermal efficiency of the system low and the fuel consumption large

[0009] (3) The temperature is adjusted by directly mixing cold air, resulting in a high oxygen content in the provided hot flue gas, which has serious safety hazards when drying some low-rank coals with poor thermal stability and easy spontaneous combustion

[0010] (4) Coal-fired hot flue gas generators have certain requirements for fuel, and additional fuel preparation devices may need to be added, which increases production costs

[0011] (5) The tail smoke loss of the drying system is very large, especially the heat loss, and the waste heat of the smoke exhaust cannot be fully utilized

However, this method only uses a part of the exhaust gas, and the fuel may need to be prepared separately

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