Energy study - Cotton Ginning
Ginning is an energy intensive process. This project evaluates the energy usage inside the cotton gins in Australia. electricity use is found to range between 44-66 kWh per bale, with national average being 52.3 kWh. The electricity consumption for different gins is nearly linearly correlated with bale numbers produced. The electricity network charge is a significant cost in cotton ginning operations. Maximum demand occupies 48-67% of total kW required to run all the energy-consuming equipment. All gins monitored had an overall power factor of higher than 0.85.
Drying temperature generally increases as module moisture increases. It is also found that the regulated drying temperature for the cotton dryer has a strong relationship with the incoming module moisture. Gas usage is strongly influenced by the amount of moisture removed from the incoming cotton as well as the regulated drying temperature. The drying process uses some 0.74 – 3.90 m3 of natural gas or 2.27 – 5.61 litres of liquefied petroleum gas (LPG) per bale. Overall thermal efficiency of the drying process is lower than 15%. The cost of gas in producing one bale ranges between $0.98–3.39/bale. Overall, the gas and electricity usage comprises approximately 39% and 61% respectively of the total energy usage (GJ/bale) in the cotton ginning process. On average, the total ―national benchmark energy cost (both electricity and gas) is $ 10.70/ bale. 60.38 kg of CO2 are emitted due to the energy use for processing each bale of cotton.
A method for the detailed monitoring of energy performance in cotton ginning is developed and described. Detailed monitoring and analysis were carried out at two gin sites. It is found that changes in trash content in the module, degree of moisture and lint quality produced do not have significant influence on electricity usage. However, the cotton variety is shown to affect the energy usage. The energy used within each ginning sub-process is quite different between the two gins monitored.
Overall, cotton handling is found to have the largest energy requirement and accounts for almost 50% of the total power usage in both gins. When combined, packaging and handling account for approximately 70% of the total power required. A significant proportion of motors inside the gins are found to operate at less than 40% loading. The low power factors of individual motors have been successfully corrected by the capacitor banks so that the overall power factor of the whole gin is satisfactory.