Steel slags processing

Increase of production of cement can be achieved by of extraction of natural resources and construction of new plants for processing these natural resources. However, this is a costly and environmentally detrimental method.

At the same time, waste of ferrous metallurgy contain an enormous amount of oxidised steel slags with a high basicity.

After meltdown of such slags in the smelting unit MAGMA and partial reduction by carbon of oxides contained in them by process route shown below, we get molten slag (molten clinker) similar by its chemical composition to cement clinker manufactured by conventional methods at existing cement plants (Table 1).

Flow diagram of melted cement clinker production

 

Table 1. Chemical composition of oxidised steel slag, cement clinker and Portland cement type СЕМ 1

Material Content, %
CaO     Al2O3   SiO2   MgO      Fe2O3   MnO     Fe, корольки SO3   
Oxidised steel slag 40-45 1,5-3 15-19 1,5-2,5 18-25 4-7 4-6 --
Slag smelted and partially reduced
in MAGMA
61,7-63 1,8-3,7 18-24 1,8-3,1 4,5-5,2 2,5-4 0 --
Conventional cement clinker 60-67 3-8 17-25 2,5-5 4-5 -- 0 --
Typical Portland cement type СЕМ 1 62-64 5,5 21,5 1,5 3-4 -- 0 1,9

Production capacity of MAGMA for clinker is 200,000-250,000 tpy and depends on chemical composition of the slag being processed and energy carrier used.

Up to 800 kg of melted cement clinker and up 250 kg of iron alloy can be produced out of 1 ton of re-smelted steel slag.

This allows to significantly reduce the costs of production of the melted clinker.

Production of melted cement clinker out of ferrous metallurgy waste allows to decrease the environmental impact due to refusal from the use of natural resources, reduce energy intensity of production and CO2 emissions per ton of products, i.e. achieve a significant environmental improvement (Table 2).

Table 2. Comparative figures of cement clinker production methods

 
Production method Raw materials Saleable
products
Energy
carriers used
Specific units per 1 ton of product
Limestone
consumption
Natural gas
consumption
Coal
consumption
Off-gases
volume
CO2
emissions
kg m3 kg kg kg
Conventional method natural resources
(clay, limestone)
cement
clinker
natural gas,
electric power
1 150-1 850 82-96 - 1 500-1 700 720-840 
MAGMA method

ferrous
metallurgy waste
(oxidised steel slags, scales, gas treatment dust)

cement
clinker,
iron alloy
natural gas,
electric power,
coal
50-570 60-70 70-110  520-930 290-615