| dc.description.abstract | Commercially available disposable sanitary napkins are the most common method of menstrual hygiene management in most urban regions of India (van Eijk, 2016) (Mathiyalagen et al., 2017). It is estimated that in India a waste of 58,500 million sanitary napkins can be generated each year (Garg et al., 2012). A typical sanitary napkin consists of several layers made from cellulosic fibres, polypropylene fibres, superabsorbent polymer, etc. (Das & Pourdeyhimi, 2014). Due to non-biodegradability of certain materials, disposal of such napkins is a major environmental concern. Among other issues, soiled napkins contain human blood and endometrial tissue which attract stray dogs and other pests posing a threat to human and environmental safety. Such napkins can be completely destroyed through incineration leaving behind only incombustible ash. Institution-based commercially available incinerators have been gaining popularity in urban cities as it is a convenient and safe method of source destruction of soiled napkins. However, they can contribute to significant air pollution within the city limits and at present there are no emission standards in India for such incinerators.
The present study investigates into the performance of two commercially available sanitary napkin incinerators (Incinerator-1 and Incinerator-2). The emphasis is on quantification of combustion efficiency and emissions, basically CO and CO2 to assess the quality of combustion. The emission values are used to evaluate the systems’ baseline performance under controlled conditions and compare the same with Indian (CPCB) standards for MSW incinerators (upper limit of 100 mg/m3 for CO when corrected to 11 % oxygen in the stack gas and minimum combustion efficiency of 99 %). From preliminary studies on Incinerator-1, it was determined that the average values of CO and CO2, emitted from combustion of one napkin were 465 mg/m3 and 0.19 % respectively (15,505 mg/m3 and 6.33 % when corrected to 11 % oxygen). In the case of Incinerator-2, the average values of CO and CO2 emitted from combustion of one napkin were 148 mg/m3 and 0.23 % respectively (3,432 mg/m3 and 5.35
% when corrected to 11 % oxygen). The combustion efficiencies did not exceed 84 % for Incinerator-1 and 95 % in the case of Incinerator-2.
Further, parametric analysis was carried out to determine the role of parameters like batch size and combustion chamber temperature in the formation of product species. The evaluation clearly established the shortcomings in the combustion chambers to handle five-napkin batches and the need for quick heating to temperatures above 600 °C. In addition, the need for air supply directed in the primary combustion zone for reducing CO emissions was explored. Experimental studies were conducted by injecting atmospheric air at locations above and under the burning fuel bed to determine the effect of air flow rate on the product gas emissions. The results obtained are used to optimize the air flow rate and location within the chamber to achieve maximum air-fuel mixing to facilitate better quality combustion. The effect of air supply to the incinerator on the product gas emissions have been addressed. Through the improved design, the CPCB emission standards for MSW incinerators have been met in the case of incineration of a single napkin with resulting combustion efficiency over 99 %. The emissions of CO have been reduced to 48 mg/m3 (94 mg/m3 when corrected to 11 % oxygen). However, the systems still had certain shortcomings especially its inability to handle larger batch sizes.
Based on the findings an alternate method of incineration using LPG was investigated and preliminary tests conducted with LPG shower promising results. The CO emissions for 1-napkin batches was reduced by over 90 % when compared to cold-start electric resistance incineration and by over 45 % compared to pre-heated condition. Additionally, combustion efficiencies of over 99 % were obtained in the case of 5-napkin batch size. There is scope to further optimize this LPG incineration with extensive investigations into various operational and design parameters like air supply rate, residence time and combustion chamber design. | en_US |
