Study of the operation of straw-fired boiler dedicated to steam generation for micro-cogeneration system

Abstract

The combined heat and power generation (CHP), based on the use of renewable energy sources, is an essential aspect of currently developing energy systems. Among the other renewable sources, biomass is characterized by high caloric value, wide availability, and low prices. This paper is focused on the study of the operation of a straw-fired boiler, as a part of developing a micro scale CHP system based on the modified Rankine Cycle operation. Based on the previously conducted studies, a dedicated construction of a 100-kWth straw-fired batch boiler was designed and implemented. Thermal oil heated in the boiler was transferred respectively to the evaporator, superheater, and oil/water emergency heat exchanger. The control of the system operation was realized using a dedicated automation system based on the programmable logic controller (PLC). Presented results include the impact of various fuel inputs and the boiler's control scenario on the oil heating process. The power received by the evaporator and superheater (the first phase of combustion process) reached a level of 48 kW temporarily. The ratio of heat taken from evaporator and superheater to the theoretical amount of chemical energy accumulated in the fuel ranged from 16.8% to 21.4%. Moreover, also observed were differences in carbon monoxide emission from the boiler. Based on the results, some outlines for controlling the operation of the boiler were obtained.