Potassium sulphate production from an aqueous sodium sulphate waste from lead acid battery recycling

In Canada and around the globe, government and regulatory agencies have implemented regulations to regulate the industries' amount and concentration of waste disposed into the environment. The regulations are enacted and executed to protect human, animal or plant health or the environment and other micro-organisms that form part of the ecosystem. Hence, there is a high industrial demand for value-added waste management methodologies, safer management, and disposition of industrial wastes. Also, the high demand for renewable energy sources necessitates the demand for energy storage technologies. Because of the comparative advantages that lead acid batteries have over other energy storage technologies, there is an increasing demand and use of lead acid batteries in various industrial operations. The lead acid battery waste stream is a significant source of Na2SO4, which is a potential reagent for production of K2SO4 for the fertilizer market. Various researchers have investigated the conversation Na2SO4 to K2SO4 and NaCl based on the assumption that Na2SO4 is pure. With this assumption, previous researchers did not investigate the capability of the impurities to either inhibit or amplify the conversion process. The Na2SO4 recovered from the recycling of lead acid battery is far from pure. The recovered Na2SO4 could not meet the market quality for commercialization because of the level of impurities - traces of heavy metals in it. The impurities in the solution are known to impede the crystallization process, with limited examples known to enhance the growth rate. HSC Chemistry and SysCAD simulation programs were used in this study to simulate the production of K2SO4 and NaCl from Na2SO4 and KCl, with the impurities accounted for in the feedstocks. The SysCAD program was used for validation of the HSC Chemistry with a strong similarity between the results from the two programs. It was found that it is possible to achieve over 90% yield and purity of K2SO4 from the Na2SO4 waste stream from lead acid battery recycling at a constant pressure of 1 bar, feed temperature of 25oC and reactor temperature of 40oC. However, when the impurities were factored into the feeds, the yield of the K2SO4 dropped from 97.8 to 84.5% and NaCl from 93.7 to 75.8%. In other words, an inversely proportional relation was observed between the yield of both the K2SO4 and NaCl and the level of impurities in the feed. The elemental equilibrium composition of the two reactors indicated a significant decrement of potassium (K) and chlorine (Cl) molecules when the level of impurities was varied from 1% to 10%. Between the impurities levels of 0 to 3%, yields of both k2SO4 and NaCl greater 90% were achieved. Thereafter, the yields dropped below 90%. This observation indicated the need for more raw material (KCl) to increase the presence of K and Cl molecules in the reactors – by implication, an increase in the cost of raw material. Based on the results, it is evident the impurities have detrimental effects on the production of K2SO4 and NaCl from Na2SO4 and KCl. Thermoeconomic analysis showed a directly proportional relationship between the impurity degrees and the exergy – both fuel exergy unit cost and product exergy unit cost for the system. This observation is an indication that the impurities in the feedstock will make the system demand more energy and do more work. Hence, it is essential to ensure that the feed is as pure as possible. The results of this simulation show that at the impurity ranges of 0% to about 4%, the system can achieve yield and purity of over 90% for both K2SO4 and NaCl. Economic assessment of the simulated process was done with a Net Present Value (NPV). estimated at $63.5 million, ROI of 27%, and a payback period of 3.37 years.

Name thesis:degree_name

Master of Applied Science (MASc)

Level thesis:degree_level

Master's

Discipline thesis:degree_discipline

Engineering - Industrial Systems

Grantor dc:publisher

Faculty of Graduate Studies and Research, University of Regina

Year dc:date.issued

2023

Author dc:creator

• Zorzor, Barialo Teiyedilo

Advisor dc:contributor.advisor

• Ibrahim, Hussameldin

Committee members dc:contributor.committeemember

• Henni, Amr
• Shirif, Ezeddin

Language dc:language.iso

en

DOI

https://doi.org/10.82465/3844

OAI identifier oai:identifier

oai:uregina.scholaris.ca:10294/16445