A method for cascade upgrading of lignite

Abstract

The invention relates to a gradient upgrading method for lignite. The gradient upgrading method for the lignite comprises the following steps that (1) the lignite is crushed; (2) equipment improvement is carried out, specifically, upgrading equipment is divided into a drying area and an upgrading area through a partition plate, the deformed material section is reshaped to be rectangular as before through the partition plate, and the flue gas heating efficiency is improved; (3) vapor condensation is carried out, specifically, vapor generated in the drying process is collected and condensed independently, the condensation amount is controlled, and 70% (by volume) of vapor in air is made to be standby; and (4) lignite upgrading is carried out, specifically, pyrolysis gas generated in the upgrading area enters a lifting flue of a cyclone barrel, fine powder of a fine coal bin is leaked from the upper end of the flue, the flowing speed of flue gas in the lifting flue is controlled to be 0.5-1.3 Nm<3> / s, and through downward flowing of the fine powder, heat in the flue gas is recycled and coal tar is adsorbed; the fine powder is dried, and the temperature of the fine powder is increased to 150-250 DEG C; upgraded lignite semicoke is obtained by upgrading the lignite in the upgrading area; and the pyrolysis gas is delivered back to a hot blast heater to support combustion. According to the method, the gradient utilization of the lignite is achieved, and the lignite resource utilization rate is high; and a cooling area is reduced, the drying area and the upgrading area are expanded, and the hour output of the equipment is improved.

Description

technical field [0001] The invention belongs to the field of coal chemical industry, and in particular relates to a method for cascade upgrading of lignite. Background technique [0002] Lignite belongs to soft coal. Compared with other coals, lignite has high oxygen content, large changes in ash content and ash melting point, low density, easy spontaneous combustion, and coal powder is easy to explode. my country's lignite is a low-quality fuel with high volatile content (about 50%), high moisture content (about 30%), high ash content (about 30%), low calorific value (about 14MJ / kg), and low ash melting point. [0003] In recent years, with the worldwide energy shortage and the dwindling of high-quality coal resources, the use of lignite in low-quality coal has gradually attracted attention. However, lignite is prone to spontaneous combustion due to its high moisture content, so upgrading its quality is a prerequisite for its large-scale use. Lignite upgrading means that l...

AI Technical Summary

Problems solved by technology

[0005] (1) Lignite is extremely easy to oxidize, and the low-level lignite will be completely weathered into peat after a week in the open air.

[0006] (2) The weathering of piles of lignite will also cause spontaneous combustion of coal piles, which wastes resources and pollutes the environment

[0007] (3) Lignite contains more water, has more pores, most of which are large pores, and has low mechanical strength, which causes excessive transport capacity and is easily broken during transportation.

[0013] ⑴Because lignite is easy to weather, there are more pulverized coal <3mm in the raw coal, accounting for about 30% of the total. If the pulverized coal is not used, the cost will increase, and the accumulation of pulverized coal will increase. Generally, quality upgrading enterprises use this part of pulverized coal to burn boilers and provide flue gas, but there are more pulverized coal in this part, and most of them cannot be effectively used

[0014] (2) In the original upgrading equipment, the flue gas is blown into the coal powder vertically from the bottom of the coal powder. In the second half of the upgrading equipment, the tiled coal powder section changes from a rectangle to a spherical crown, and the upgrading flue gas is short-circuited, affecting Improve quality and shorten equipment life

[0015] (3) The original upgrading equipment is macroscopically divided into drying zone, upgrading zone and cooling zone, but the distribution of temperature range is not strict. At the same time, most of the water vapor in the drying zone is brought into the upgrading zone, which reduces the efficiency of upgrading; cooling zone It has the effect of cooling down, but cannot increase the quality and output

[0016] ⑷The water recovered by quality improvement is recovered in the original technology and used in other ways, and the cost of water condensation is high

[0017] (5) Moisture participates in the upgrading process, lignite is heated unevenly and is prone to spontaneous combustion

[0018] ⑹Lignite dust after upgrading is relatively large, and the working environment is harsh

[0019] ⑺ The upgrading temperature is low, and the structure of lignite cannot be changed to a large extent, resulting in easy water absorption and spontaneous combustion after upgrading

[0020] ⑻ The volume density of upgraded lignite is small, and the transportation cost is high

Images