Abstract
In this study, CaO-containing wastes from pulp and paper industries such as fly ash (FA) and calcined lime mud (LM) were utilized to neutralize and purify acidic wastewaters from the pickling processes in steel mills. The investigations were conducted by laboratory scale trials using four different batches of wastewaters and additions of two types of CaO-containing waste materials. Primary lime (PL), which is usually used for the neutralization, was also tested in the same experimental set up in the sake of comparison. The results show that these secondary lime sources can effectively increase the pH of the acidic wastewaters as good as the commonly used primary lime. Therefore, these secondary lime sources could be potential candidates for application in neutralization processes of industrial acidic wastewater treatment. Moreover, concentrations of metals (such as Cr, Fe, Ni, Mo and Zn) can decrease dramatically after neutralization by using secondary lime. The LM has a purification effect from the given metals, similar to the PL. Application of fly ash and calcined lime mud as neutralizing agents can reduce the amount of waste from pulp and paper mills sent to landfill and decrease the need for nature lime materials in the steel industry.
Highlights
The production chain of stainless steel is made up of a series of steps, where the steel undergoes various treatments to reach the desired material properties and surface qualities
Underneath the oxide layers, some chromium depleted zones exist since the chromium diffused to the surface
This study focused on investigating the possibilities to use some different CaOcontaining wastes obtained from pulp and paper industries to replace primary lime in the neutralization process
Summary
The production chain of stainless steel is made up of a series of steps, where the steel undergoes various treatments to reach the desired material properties and surface qualities. Underneath the oxide layers, some chromium depleted zones exist since the chromium diffused to the surface. These zones have lower corrosion resistances and strengths [1]. In order to remove these chromium depleted zones, a pickling process can be applied. Pickling is a chemical cleaning process that is commonly used in various steelmaking processes in a steel mill for removal of impurities (such as contaminants, corrosion products or scale) from a steel surface. After treating the steel in a pickling bath, the steel is rinsed with water
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