Statistical optimization, characterization and effect of process variables on cotton stalk pellets using tractor drive pelleting machine.

Abstract

In present study, the development, production, characterization and economic analysis of pellets made from cotton stalk in a tractor PTO-based pelleting machine are investigated. The cotton stalk is widely available in the southern part of India and has a huge potential in bioenergy generation due to its salient physicochemical composition. Many regions of Southern India are suffering from an electricity shortage, and therefore to overcome on this issue, an energy-efficient, portable, tractor PTO-operated pelleting machine was developed that can be operated directly on the field to reduce the transportation cost of agro-residues. The Box-Behnken design using response surface methodology (RSM) was employed to evaluate the performance of the pelleting machine. Based on the ANOVA results, the pelleting efficiency, pelleting capacity, bulk density of pellet and fuel consumption were obtained to be 87.06%, 42.65kg/h, 614.09kg/m3 and 1.12 lit/h, respectively. In order to examine the physicochemical properties of cotton stalk pellets, the proximate, ultimate, physical, TG-DTG, FTIR and SEM analysis have been carried out. As a result, the ash content, calorific value, shattered index and durability of cotton stalk pellets were found to be around 2.73%, 18.92MJ/kg, 92.80% and 93.75%, respectively. A combustion characteristic of pellets using TGA analysis exhibited a maximum mass loss (43.5%) observed in between 180 and 350°C due to the degradation of cellulose and hemicellulose, whereas a SEM analysis of cotton pellets justified its homogeneous morphology along with rich concentration of minerals. The benefit-cost ratio and payback period of developed tractor PTO-operated pelleting machine for cotton stalk were found to be 1.11 and 33.1months, respectively. The internal return of rate was observed to be 74%.