Improving the Performance of Cogeneration System in Sugar Factory by the Integration of Superheated Steam Dryer and Parabolic Trough Solar Collector

Abstract

Superheated steam drying has previously been shown to improve the performance of the cogeneration system in sugar factory because it can reduce bagasse moisture content, which increases the efficiency of the steam generation unit, and recover water that would be lost with flue gases. The performance of this system depends on the degree of superheat in the extracted superheated steam, which is the difference between the superheated steam temperature and the saturated steam temperature at the same pressure. In this paper, an investigation is made into the use of parabolic trough solar collector to increase the temperature of superheated steam for drying bagasse. A case study under consideration is that of a system that processes 100 t/h of sugar cane. The pressure and temperature of steam generated from the steam generation unit are, respectively, 4.5 MPa and 440 °C. This system requires 42 t/h of water in the juice extraction unit. The outputs of the unit are 112 t/h of diluted sugar juice and 30 t/h of moist bagasse. The amount of saturated steam at 200 kPa required for the evaporation unit is 37.3 t/h. If 6 MW is generated by the steam turbine, a system with only superheated steam dryer consumes 2.325 kg/s of dry bagasse consumption and recovers 0.282 kg/s of water. If the solar direct beam irradiation is 500 W/m2, the integration of the parabolic trough solar collector with the aperture area of 1000 m2 results in the reduction of dry bagasse consumption by 0.027 kg/s or 283 ton/year compared with the system without parabolic trough solar collector. Furthermore, 0.089 kg/s of more water is recovered. The simple payback period for this system is 6.36 years.