Comparative Evaluation of Integrated Waste Heat Utilization Systems for Coal-Fired Power Plants Based on In-Depth Boiler-Turbine Integration and Organic Rankine Cycle

Abstract

To maximize the system-level heat integration, three retrofit concepts of waste heat recovery via organic Rankine cycle (ORC), in-depth boiler-turbine integration, and coupling of both are proposed, analyzed and comprehensively compared in terms of thermodynamic and economic performances. For thermodynamic analysis, exergy analysis is employed with grand composite curves illustrated to identify how the systems are fundamentally and quantitatively improved, and to highlight key processes for system improvement. For economic analysis, annual revenue and investment payback period are calculated based on the estimation of capital investment of each component to identify the economic feasibility and competitiveness of each retrofit concept proposed. The results show that the in-depth boiler-turbine integration achieves a better temperature match of heat flows involved for different fluids and multi-stage air preheating, thus a significant improvement of power output (23.99 MW), which is much larger than that of the system with only ORC (6.49 MW). This is mainly due to the limitation of the ultra-low temperature (from 135 to 75 • C) heat available from the flue gas for ORC. The thermodynamic improvement is mostly contributed by the reduction of exergy destruction within the boiler subsystem, which is eventually converted to mechanical power; while the exergy destruction within the turbine system is almost not changed for the three concepts. The selection of ORC working fluids is performed to maximize the power output. Due to the low-grade heat source, the cycle with R11 offers the largest additional net power generation but is not significantly better than the other preselected working fluids. Economically, the in-depth boiler-turbine integration is the most economic completive solution with a payback period of only 0.78 year. The ORC concept is less attractive for a sole application due to a long payback time (2.26 years). However, by coupling both concepts, a net power output of 26.51 MW and a payback time of almost one year are achieved, which may promote the large-scale production and deployment of ORC with a cost reduction and competitiveness enhancement.

Waste Heat Recovery from Fossil-Fired Power Plants by Organic Rankine Cycles

“…The heat in the exhaust flue gas can be used to preheat feedwater by a low-pressure economizer [5][6][7] and pre-dry brown coal [8][9][10][11]. The waste heat of exhaust flue gas can also be used to drive an organic Rankine cycle to produce electric power [5,[12][13][14].…”

New Concept of Power Generation Using TEGs: Thermal Modeling, Parametric Analysis, and Case Study

“…A TEG is a solid component that provides direct energy due to the variation of the surrounding thermal behavior, and electrical power can then be generated based on the “Seebeck effect” and temperature gradient [ 6 , 7 , 8 ]. Thermoelectric technology had become popular in heat recovery applications and it was implemented with various sources such as internal combustion engines [ 9 , 10 , 11 , 12 ], stoves [ 13 , 14 , 15 ], vehicles [ 16 , 17 , 18 , 19 ], biomass gasifiers [ 20 ], chimneys [ 21 , 22 ], diesel engines [ 23 , 24 , 25 , 26 ], and fuel cells [ 27 ].…”

Heat Transfer Performance in a Superheater of an Industrial CFBC Using Fuzzy Logic-Based Methods

“…Abdelmotalib et al remarked that due to very complicated processes, which occur in the fluidized bed combustors, it is difficult to cover all aspects of heat transfer [ 9 ]. Therefore some additional, auxiliary data, e.g., to adjust parameters or to solve complex differential equations are necessary, and even other assumptions should be made to get a trackable solution [ 33 , 34 , 35 , 36 , 37 , 38 ]. As an example, Zhou et al pointed out that simulations conducted on the platform of FLUENT 12 software with three processors parallel for 70 s with the number of meshes nearly 8500 costs nearly 60 days [ 15 , 39 ].…”