Abstract:
Nowadays energy shortfall is becoming a major problem worldwide. Some of the reasons behind this alarming situation are less efficient energy generation, unexplored renewable energy resources and over consumption of fossil fuels. Possible effective solutions to cater this condition could be replacement or modification of less efficient energy generation equipment and to move towards renewable energy resources.
There had been a great influence of researchers towards Organic Rankine Cycle (ORC) development in the past decade. But ORC implementation for waste heat recovery from boilers and steam turbine condensers have received comparatively less attention of researchers. This study has been performed to check the feasibility of energy efficiency enhancement of 2.66 MW Gadoon Textile Mills Limited (GTML) thermal powerplant, by effectively extracting the inferior heat from boiler waste gas through coupling of existing system with ORC. Waste energy utilization reduces the carbon footprint and global warming due to additional energy generation by efficiency enhancement.
Refrigerant R245fa has zero ozone depletion potential and suitable for low temperature applications hence, it has been used in present study. A steady state simulation model of ORC system has been developed through Powerplant Simulator and Designer (PPSD) software. All components including; water heater, water pump, refrigerant pump, evaporator, ORC turbine and refrigerant condenser simulation is performed.
In this study, a comparative analysis of thermal and electrical efficiency has been conducted for traditional Steam Rankine Cycle (SRC) based powerplants and SRC-ORC system. Through ORC waste heat recovery, boilers waste flue gas temperature is decreased from 170 to 98°C on average. Therefore, 3710 kW more heat has been extracted from waste gases and overall plant thermal efficiency is enhanced from 61.84% to 82.68%. Overall net electric efficiency of existing system is increased by 0.9% and additionally produced power can fulfill the internal electricity requirement of studied powerplant.
Economic analysis including plant cost estimation and payback period calculation of proposed system has also been performed. Chinese and European origin ORC plant cost is 0.238 and 0.337 million PKR/kW respectively. The evaluated payback period is found to be feasible as it is varied between 2.9 to 5.9 years based on the equipment origin (Chinese or European) and different plant operation scenarios. Hence, the proposed system has considerable technical and economic potential for energy efficiency enhancement through boiler’s waste heat recovery.
To validate the simulated model, no similar data from literature could be found for comparison with present study. However, re-modeling of published data has been performed on PPSD to compare present simulation results with previous study.
