Lignite pre-drying process and lignite pre-drying device

Abstract

The invention discloses a lignite pre-drying process and a lignite pre-drying device which solve the problems of poor 'dewatering' and dedusting effects and no large-scale industrial application caused by direct-contact heat transfer of the prior art. The technical scheme includes that the process includes that lignite with the granularity smaller than 13mm is fed into a drying tube of a tube drier via a lignite inlet of the tube drier, and meanwhile, a heat source serving as a drying medium is fed to the outside of the drying tube of the tube drier, so that lignite in the drying tube and the heat source outside the drying tube are subjected to indirect heat exchange, and dried lignite is discharged via a lignite outlet; and exhaust with dust and generated by feeding of the lignite in the drying tube is mixed with steam generated after lignite drying to form tail gas, the tail gas enters a bag filter via a tail gas outlet to be filtered and separated, lignite dust collected after separation is discharged via a dust outlet of the bag filter, and the tail gas is discharge by an induced draft fan via a tail gas outlet of the bag filter. The lignite pre-drying process is simple, good in dewatering effect, safe, reliable and suitable for large-scale industrial application, and tail gas emission reaches the standards.

Description

technical field [0001] The invention relates to a lignite pretreatment process and device, in particular to a lignite predrying process and device. Background technique [0002] Due to the high moisture content of lignite (generally more than 30 Wt %, some as high as 60 Wt %), it is difficult to dry; the volatile content is high, easy to spontaneous combustion; the content of fixed carbon is low, in order to meet the requirements of the follow-up system, it is necessary to The coal is pre-dried to reduce its moisture, that is, the moisture content needs to be reduced to 10 wt% to 15 wt%. For the coal industry, reducing the moisture content of lignite can increase the calorific value of coal, reduce transportation costs, reduce surcharges (such as antifreeze), and enhance market competitiveness; while in the power industry, reducing the moisture content of lignite can increase the calorific value , can reduce the investment in follow-up system equipment (such as milling, boi...

AI Technical Summary

Problems solved by technology

However, after over-drying, re-moisture absorption may occur, and if it is dried at high temperature for a long time, its volatile components will be lost, thereby reducing the effective components, and in severe cases, spontaneous combustion and dust explosion will occur

Affect its large-scale industrial utilization

Therefore, the "precipitation" problem of lignite has always been the bottleneck that plagues the full utilization of lignite

[0003] Aiming at the "precipitation" problem of lignite, domestic rotary drum dryers have been used to dry lignite, and the flue gas is directly passed into the rotary drum dryer to exchange heat with the raw coal in the dryer to achieve the purpose of drying. This method belongs to direct contact. The low-temperature drying method, due to various limitations in the process, has a low output, and the drying heat medium is in direct contact with the raw coal, and the drying temperature is not suitable for control. For low-flammability coal such as lignite, there is a greater safety hazard. Currently So far, for the "precipitation" problem of lignite, there is no good process method that can meet all the above requirements

And for the exhaust dust removal of the drying system, some use electrostatic precipitators. Because of its low resistance, no induced draft fan is installed, and only the chimney effect is used to operate. The drying system capacity of this process cannot be controlled and adjusted, and the drying moisture is difficult to control. Cause problems in the downstream process system; at the same time, the dust content of the exhaust gas after dust removal cannot meet the environmental protection requirements; and because of the explosive nature of lignite, if only explosion venting measures are used, flash explosions are prone to occur in the process system

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