Emission reduction technology for VOCs in the sintering process of the steel industry. The measures taken by the domestic and international steel industry to reduce the emission of VOCs in the sintering process can be divided into three categories: source reduction, process control and end treatment.

Source cuts. In terms of source reduction, since most of the petroleum hydrocarbons volatilize in the sintering mixture at 100 ° C to 800 ° C and are discharged from the sintering process by the exhaust gas, reducing the use of oily dust and rolling chips can reduce VOCs emissions. The main techniques include: separately selecting low oil content dust and rolling mill to limit oil input; reducing the oil content of the rolling mill; purifying the rolling mill, heating the rolling mill to 800 ° C, volatilizing petroleum hydrocarbons; using solvent to roll from Extract oil from the chips.

Process control. In terms of process control, a part of the hot exhaust gas (ie, the flue gas of the sintering head) of the sintering trolley can be re-introduced into the sintering layer by the sintering flue gas circulation process, and the VOCs contained in the hot exhaust gas pass through the sintering zone above 1300 ° C. Time is broken down. At present, the typical sintering flue gas circulation processes that have been industrialized by domestic and foreign steel companies mainly include the regional exhaust gas circulation technology developed by Nippon Steel, the emission optimized sintering (EOS) developed by Aimeiden, the Netherlands, and the low emission and developed by the German HKM. Energy optimized sinterprocess (LEEP) and environmental process optimized sintering (EPOSINT) developed by VAI.

China's research and application of sintering flue gas circulation technology has just started. Ningbo Iron and Steel Company adopted sintering flue gas circulation technology in 2013.

End management. In terms of end treatment, the main technologies are the activated carbon method in Japan, the Linz steel mill and the maximised emission reduction of sintering.

The activated carbon method is that after the simple dedusting of the sintering flue gas by the cyclone dust collector, the dust concentration is reduced from 1000 mg/m3 to 250 mg/m3, and is discharged by the main fan. The flue gas is sent to the moving bed absorption tower through the booster blower, and the ammonia gas required for denitration is added at the inlet of the absorption tower. The SO2 and NO in the flue gas react in the absorption tower, and the sulfuric acid and the ammonium salt are removed by adsorption by activated carbon. The activated carbon adsorbed with sulfuric acid and ammonium salt is sent to the desorption tower, and the high concentration SO2 can be desorbed by heating to about 400 °C. The desorbed high-concentration SO2 can be used to produce high-purity sulfur (99.95% or more) or concentrated sulfuric acid (98% or more). The activated activated carbon is cooled to remove impurities and sent back to the absorption tower for recycling. Activated carbon method mainly relies on the pores of activated carbon to adsorb VOCs. The setting of the main sintering flue gas purification devices of foreign steel enterprises is shown in Table 3. It can be seen that many enterprises adopt the activated carbon method, and domestic steel companies such as Taigang also use the activated carbon method.

The MEROS method is to uniformly and high-speed and counter-flow the additive into the sintering flue gas, and then humidify and cool the sintering flue gas by using a high-efficiency dual-flow (water/compressed air) nozzle in the regulating reactor. After leaving the conditioning reactor, the dusty flue gas is passed through a pulse bag filter to remove dust particles from the flue gas. In order to improve gas purification efficiency and reduce additive costs, most of the separated dust in the filter bag filter is circulated to the gas stream after conditioning the reactor. Some of the dust leaves the system and is transported to the intermediate storage silo. The MEROS process combines desulfurization, de-HCl and de-HF, and allows almost all of the condensable parts of VOCs to be removed. At present, Ma Steel in China adopts the MEROS process.