Composition of slag
Bottom ash (ie slag) is the main part of ash and slag, which is dark brown and accounts for about 80%-90% of the total mass of ash and slag. The moisture content of the slag is 10.5%~19.0%, the reduction rate on hot ignition is 1.4%~3.5%, and the low reduction rate on hot ignition reflects its good incineration effect. Bottom ash is a heterogeneous mixture of slag, glass, ceramic fragments, iron and other metals, and other non-combustible substances, as well as incompletely burned organics. Large particle slag (>20mm) is mainly composed of ceramics/bricks and iron, and the mass percentage of the two substances decreases with the decrease of particle size; small particle slag (<20mm) is mainly composed of molten slag and glass. It increases with decreasing particle size, mainly due to the different physical properties of these substances and the impact force they experience when moving in the grate.
About 200~250kg of slag is produced due to the incineration of 1t of domestic waste. Taking the Chongqing Tongxing Waste Incineration Power Plant with a daily processing capacity of 1200t as an example, about 80,000~110,000 tons of slag is produced in one year.
Slag sorting process
The total content of iron in the slag is 5% to 8%. At present, the domestic slag sorting is mainly to sort the iron in the slag.
The burnt slag in the grate falls into the slag remover, and through the cooling of water, the hydraulic slag remover drains the cooled slag and sends it to the belt conveyor. The high-grade iron separator uses magnets to sort out the metal iron. In order to further improve the sorting effect, the factory is generally equipped with a vibration device and a crushing device during the slag conveying process to increase the sorting power.
properties of slag
The particle size distribution of slag is mainly concentrated in the range of 2~50mm (accounting for 61.1%~77.2%), which basically meets the gradation requirements of road building materials (aggregate, graded crushed stone or graded gravel, etc.). The dissolved salt content of slag is low, only 0.8%~1.0%, so the possibility of groundwater pollution due to dissolved salt during slag treatment and disposal is small. The slag has a strong pH buffering capacity, and the initial pH value (leaching with distilled water, with a liquid-solid ratio of 5:1) is above 11.5, which can effectively inhibit the leaching of heavy metals [2]. Therefore, slag is a good building material, and as long as it is properly managed, it can be used for environmental protection and resource utilization.
Advantages of slag-made non-burning bricks
Slag-free bricks can use waste incineration slag as the main raw material, with a content of more than 80% (including aggregates), turning waste into treasure and turning harm into profit. The non-burning brick project has a competitive advantage in the market. The state strictly restricts the production of clay bricks. The non-burning bricks do not use clay as raw material and coal as fuel, so as to protect arable land and protect the environment. Brick making is all mechanized production, the production process is simple, easy to master, and can be applied everywhere. The production of non-burning bricks is formed by the two-way action of equipment down-pressing and high-frequency directional vibration after the materials enter the standard mold box. At present, among all the technologies that use industrial waste residue to produce building materials, the non-burning brick project has the least investment and the fastest effect.
brick making process
After sorting, the slag passes through the conveying system, batching system, mixing system, distribution system, forming system, demoulding system, blanking system, automatic stacking system, hydraulic system, electrical control system, etc. The slag, cement, stone and stone powder are pressed into shape in the ratio of 4:15:15:15 to achieve the purpose of resource utilization.