Cold Briquette Technology of Converter LT Dust
Dust removal methods in the converter steelmaking process can be divided into the wet method and dry method. The traditional wet purification system is as follows: after the flue gas is treated by water spraying, the smoke dust is removed, and the sewage with smoke dust is treated by separation, concentration, and dehydration to obtain converter sludge, and the purified gas is recycled. The new dry purification system is that the flue gas is cooled and quenched and tempered, and then enters the cylindrical electrostatic precipitator for purification, and the captured dust is the primary dust of the dry converter (LT dust for short).
The advantages of LT dry dust collection include the following aspects:
1. The dust removal and purification efficiency is high, and the dust concentration can be reduced to below 10mg/m3.
2. The system adopts dry treatment, so there is no secondary pollution and sewage treatment.
3. The resistance loss of the system is small, the heating value of the gas is high, and the energy consumption is reduced.
4. The system is simplified, the occupied area is small, and it is convenient for management and maintenance.
At present, there are mainly the following methods for the utilization of converter LT dust at home and abroad:
The hot briquetting process uses the spontaneous combustion characteristics of dust to heat the dust, uses its plasticity at high temperature, presses it into blocks by a high-pressure briquetting machine, then cools it in a nitrogen sealed state and transports it to a converter to replace scrap steel or ore. This method does not need to add an additional binder, and the strength of the dust lump is also very high. At the same time, due to the work in a nitrogen atmosphere, the hydration reaction of CaO in the LT dust lump causes the problem that the strength of the finished ball is reduced or even pulverized. It is currently the most widely used method for LT dust treatment. However, the production of hot-pressed blocks needs to be carried out under the conditions of high temperature and air isolation, which requires high equipment and process control. Moreover, the one-time investment is large, the process conditions are harsh, the equipment failure rate is very high, and it is difficult to produce smoothly for a long time.
2. Wet lump
LT dust is first humidified into mud blocks, then pressed into blocks by a wet low-pressure briquetting machine after adding certain additives, and then consolidated to a certain strength by consolidation methods such as medium-temperature baking, high-temperature sintering, carbonation, cement curing or long-term natural stacking curing, and then returned to a converter for smelting. This method solves the problems of spontaneous combustion of dust and pulverization of lump products, but there are other problems, such as serious secondary pollution, large occupied space, high production cost and so on.
3. Return to sinter
LT dust is transported to the stock yard after being suppressed by water spraying, and then used as sintering raw material after natural stacking and cooling. Although this method does not need to add equipment, LT dust with too fine particle size and spontaneous combustion does not use sinter quality control and heat balance, and secondary pollution is very serious during transportation.
