Recycling kiln bypass dust into valuable materials

A new process has been developed for processing chlorine-bypass-dust into new materials that can be sold or used in the cement kiln. Bypass dust is the dust that is rejected from a kiln system in order to lower the chlorine or alkali content of the produced clinker. Many cement plants have routinely landfilled this dust over many years. The strategic concept of "zero waste" is the basis for this system, but other smaller reasons also exist for its development: · The landfill disposal costs are high in some areas. · Bypass dust, which is typically wasted, has a unit cost of 20-30% of the cost per ton of producing clinker - depending on the cement making process type - and this cost can be recuperated. · For environmental reasons it may be beneficial to reduce the landfill area within the overall plant site area. · An increase in alternative fuels may cause an increase in bypass dust that needs to be extracted, thereby, causing higher disposal specific production costs. · The sales price of salt runs at approximately 350 USD/t which is potentially a new income stream for the plant. The dust reduction system is made up of the following sections: 1. Washing of bypass dust with water; 2. Filtration to obtain a salt solution (brine); 3. Chemical treatment (purification and conditioning of the brine); 4. Evaporation of this clean-neutralized brine to obtain the alkali-salts. The products of the system are: 1. Raw meal, low in alkalis and chlorine, that can be directly used as kiln feed. 2. High purity salts that can be used for food, de-icing roads, or making fertilizer. 3. Heavy metals sludge that can be treated separately to obtain valuable metals. A pilot plant has been installed with positive results and now the first industrial-sized plant is under construction.