Waste minimisation at an air-conditioning company.
Waste minimisation involves reducing waste (emissions, effluent, solid waste) in companies, at source. v 7, 8 Its benefits include cost savings, environmental improvement, increased throughput and risk and liability reduction. 7, 8, 13 Through implementation of a structured waste minimisation programme, companies can identify waste minimisation opportunities: broad focus areas that will benefit from a more detailed waste minimisation assessment. More specific waste minimisation solutions can then be identified. In this study, the waste minimisation opportunity was identified by the company, Ben Booysen, a priori. Ben Booysen is a local air-conditioning and refrigeration company in Pietermaritzburg, which services air-conditioner units. They identified the waste minimisation opportunity of optimising the process conditions for cleaning the airconditioner units. At the time at Ben Booysen, Alukleen, an acid cleaner (RT Chemicals®, RTCM 64) , was applied manually (by a paintbrush) at an effective dilution of 1:3 to clean the aluminium air-conditioner coils. Handy Andy and green soap were used to clean the plastic covers of the units. Concerns about the effluent, cost and safety of handling Alukleen led to their identification of this waste minimisation opportunity. The initial objectives of this project were thus the qualification and quantification of the species present in Alukleen; the quantification of the species present in the Ben Booysen effluent and the subsequent comparison of these values to limits for disposal to stormwater and Darvill. A further objective was the optimisation of the cleaning system with regard to Alukleen concentration and contact (soaking) time. Wet chemical analysis was employed as a qualitative tool for identification of the components present in Alukleen. This analysis indicated that fluoride, sulfate, sulfide, arsenite and chloride ions are present in Alukleen. Further quantitative analysis using the Ion chromatograph, the ICP-OES and a fluoride ion selective electrode indicated that only sulfate (152600 ppm) and fluoride (25400 ppm) are present in significant quantities. Studies were conducted on aluminium coil pieces in which both the contact (soaking) times and Alukleen concentrations were varied. These tests indicated that the effect of soaking time on the cleanliness achieved was negligible. Although a greater amount of dirt was removed when using more concentrated Alukleen solutions, etching of the metal occurred at higher concentrations, resulting in a loss of sheen and malleability of the metal. Etching of the aluminium air-conditioner coils by Alukleen, as indicated by both digital photography and electron microscopy, resulted in extending the objectives of this project to include the investigation of alternative aluminium cleaners. Hence, the cleaning action of three degreasers was investigated: Powerkleen (RT Chemicals®, RTCMI23), Technicians' Choice (Auto Brite (PTY) Ltd.) and Klengine (Auto Brite (PTY) Ltd.) . Powerkleen was found to be the most effective degreaser and did not compromise the metal's sheen or malleability. Further studies were then conducted to characterise the major components ofPowerkleen and to optimise its use with regard to concentration and contact (soaking) time. The suitability oftwo methods of application was also tested. The main component of Powerkleen, determined through the use of ICP-OES, was found to be potassium hydroxide, present at a concentration of 0.711 M. The optimum Powerkleen concentration range for cleaning the aluminium coils was found to be between a 1:20 and 1:40 dilution. Contact (soaking) time of Powerkleen with the aluminium coils was found to have a negligible effect on the mass of dirt removed by the degreaser. Application of the Powerkleen to the aluminium coils by an air gun at a pressure of 4 bars (for units serviced at Ben Booysen) and by a pump bottle (for units serviced in industry) were both found to achieve an acceptable degree of cleanliness of the aluminium. A feasibility analysis (technical , economical and environmental) indicated that a 1:40 dilution of Powerkleen is a feasible, cost-effective and environmentally compliant alternative to Alukleen. Implementation of the Powerkleen cleaning system would result in a R5030 annual saving with a payback period of 5.9 months and an internal rate of return of 214.9%. It would further eliminate the fluoride effluent problems associated with Alukleen and reduce the quantity of chemical raw materials required for the process from 2100 Llannum to 260 Llannum. In industry, an effective dilution of 1:39 would be used for the sake of eas y dilution. A 1:79 dilution of Powerkleen was also found to be a feasible replacement for Handy Andy and green soap in the cleaning of the plastic covers of the units.