Semi-dry concept
Converter primary dust method mainly comes from Japan's wet method and stem from Europe. In recent years, the semi-dry law that China began adopting and rapidly promoted was China's invention patent and high-tech in Shanghai. Briefly, the semi-dry method is a new dust removal process technology that combines a dry evaporative cooler with a wet scrubber (girth venturi or wet electrostatic precipitator) in combination with a dry process, a new OG wet process Process difference.
Semi-dry dust removal technology features and advantages
1, the choice of semi-dry reason
Comprehensive environmental design brochures, textbooks and foreign industrial flue gas dust removal experience, choose from the gas separation and recovery of particle size 10-100μm dry dust, dust and cyclone dust removal the most economical, 1-10μm dust should be wet dust, and only For the following 1μm soot is suitable for considering the choice of ESP, Venturi or bag filter dust. When the converter gas does not burn, 90% of the dust particles are larger than 10μm. The innate defect of various wet dedusting is to wash all the dust into the drainage water, resulting in a complex sewage treatment problem. , High moisture content, viscosity of the converter once the dust is not correct, this is its fouling, the root causes of unstable emissions. The semi-dry method uses the evaporative cooler similar to the dry process to recover more than 40% dry ash, retains the advantages of wet scrubbing and dust removal, overcomes the respective defects of dry and wet processes, and shows better performance than wet and dry processes Competitive Advantage.
2, the second generation of semi-dry dust removal technology
Semi-dry technology first applied from 2004 to now go through two generations of technological innovation and improvement: the first generation of semi-dry method to follow all wet water wet ash; and the second generation of semi-dry method prominent feature is the recovery of more than 40% Dry dust, its process and major equipment.
The first generation of semi-dry method in China has more than 100 converter used, the second generation of semi-dry method has 5 converter used, the dust concentration has long been stable down to ≤ 5mg / Nm3. After the semi-dry and dry treatment of gas dust concentration actual measurement results. It can be seen from the figure that the gas dust concentration after the semi-dry treatment is lower than that of the dry method.
3, the main advantage of the new converter using semi-dry method
1) Saving investment: Compared with the dry method and the new OG method, the semi-dry method reduces the investment by more than 50%, for example, the 120t converter can save an investment of over 10 million yuan. Semi-dry relative to the dry method, saving the dry electrostatic precipitator, gas cooler and automatic control equipment investment; relative to the wet method, saving water treatment investment.
2) reduce the area: semi-dry method, the equipment can be arranged in the workshop, covers an area of ​​?? less. Compared with the dry method to reduce the electrostatic precipitator, gas cooler and circulating water and other equipment area; compared with the wet method to reduce the water treatment equipment area, such as 120t converter, for example, using dry and wet ( Including water treatment part), equipment covers an area of ​​more than 7000m2, and the use of semi-dry method, covers an area of ​​less than 3000m2. In the case of plant area constraints, reducing equipment footprint (in itself, saving money) is more important than saving money.
4, using semi-dry method to transform the main benefits of the existing wet method
Modification of existing OG or new OG wet process by semi-dry method can not only completely solve the environmental problems of chimney discharge and smoke at the mouth of the furnace, but also achieve greater economic and energy-saving benefits. Mass production statistics show that:
1) increase gas recovery 10-20Nm3 / t, gas CO content increased by 10%, reducing converter energy consumption over 2kgce / t, reducing costs over 2 yuan / t;
2) Reduce the cost of recycled water by more than 2% / t by reducing the amount of circulating water by more than 50% so as to save more than 2 kWh / ton of steel per tonne, and reduce the cost of water treatment accordingly.
3) At the same control emission concentration, the power consumption of the primary dust removal fan can be reduced by 1-2kWh / t due to the reduced resistance loss.
In fact the semi-dry method to transform the wet, auxiliary spray dust removal is the greatest potential economic benefits can not open the secondary dust fan or reduce the secondary dust fan speed. Because the secondary dust blower high power consumption, but the use of very low efficiency, the effective control of a furnace smoke and the use of spray control feeding dust, with the secondary dust blower or reduce the secondary fan speed conditions.
5, using semi-dry method to transform the main content of the existing wet method and the time required
The semi-dry method to transform the existing wet method needs to dismantle the existing equipment such as overflow venturi, dual text, dehydrator and so on. The new design and manufacture of evaporative cooler (including dry and conveying ash system), spray dust collector, Tube, dehydrator and other new equipment, and the electrical control, instrumentation, water supply and drainage, etc. to be updated or adjusted accordingly. The new equipment design and production cycle of 1-3 months, shutdown furnace construction and installation of the cycle in 7-15 days. In fact, most users are revamping their annual maintenance opportunities with converter equipment.
6, using semi-dry method to transform the existing dry method
The existing dry gas cooler with wet saturated cooling, still need to recycle water system, such as 120t converter needs recycled water about 200t / h, on the one hand, recycled water system to increase equipment investment, covers an area, more importantly, the cooler The outlet temperature can only reach the saturation temperature of about 70 ℃, and sometimes it will be forced to release qualified gas because the gas temperature exceeds the requirement of the gas tank. Semi-dry method is the use of extreme evaporative cooling technology, that is, without circulating water can reach the required saturation temperature, and if you keep the circulating water, the gas temperature can be reduced to 50 ℃ or lower. Due to the reduction of steam volume, the volume of gas will be reduced by 30%, which helps to increase the gas recovery and gas calorific value.
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