Fuel Saving in Biomass Power Plant Using Solar Heat Supplied by Parabolic Trough Collectors and Waste Heat Recovered From Variable Boiler Blowdown

Abstract A hybrid drying system uses both a steam dryer and a flue gas dryer to reduce fuel moisture content, which results in increasing the energy efficiency of the biomass power plant. It has been demonstrated previously that flash steam from a blowdown heat recovery system may be used to operate a hybrid drying system. Steam is supplied to the steam dryer from direct steam-generating parabolic trough collectors. However, the intermittent nature of solar radiation means that the steam dryer will have to operate inefficiently with a variable steam supply. In this article, it is proposed that direct steam-generating parabolic trough collectors should be integrated with a blowdown heat recovery system. The problem of the fluctuating solar radiation is solved by varying the blowdown rate so that the steam dryer receives a steady steam supply. Blowdown rate is maximum when there is no solar energy, and blowdown rate is minimum when the maximum amount of steam is generated by parabolic trough collectors. The daily operation of the proposed system is divided into two modes depending on the availability of solar energy. It is demonstrated that the proposed system can reduce fuel consumption by 1.70% annually compared with the reference system that supplies steam to a steam dryer using only a blowdown heat recovery system.