Thermodynamic and Economic Analyses of a Novel Cooling, Heating and Power Tri-Generation System with Carbon Capture

Abstract

The combined cooling, heating, and power (CCHP) system has attracted increasing attention due to its potential outstanding performance in thermodynamics, economics, and the environment. However, the conventional CCHP systems are carbon-intensive. To solve this issue, a low-carbon-emission CCHP system (LC-CCHP) is firstly proposed in this work by integrating a sorption-enhanced steam methane reforming (SE-SMR) process. In the LC-CCHP system, CO2 is continuously captured by the calcium loop so that low-carbon energy can be generated. Then, the LC-CCHP system thermodynamic model, mainly consisting of a dual fluidized bed reactor which includes the SE-SMR reactor and a CaCO3 calcination reactor, a hydrogen gas turbine, a CO2 reheater, and a lithium bromide absorption chiller, is built. To prove that the LC-CCHP model is reliable, the system major sub-unit model predictions are compared against data from the literature in terms of thermodynamics and economics. Finally, the effects of reforming temperature (Tref), the steam-to-carbon mole ratio (S/C), the calcium-to-carbon mole ratio (RCC), the equivalent ratio for gas turbine (RAE), and the hydrogen separation ratio (Sfg) on total energy efficiency (ηten), total exergy efficiency (ηtex), and carbon capture capability (Rcm) are detected. It is found that the minimum exergy efficiency of 64.5% exists at the calciner unit, while the maximum exergy efficiency of 78.7% appears at the gas turbine unit. The maximum energy efficiency and coefficient of performance of the absorption chiller are 0.52 and 1.33, respectively. When Tref=600 °C, S/C=4.0, RCC=7.62, RAE=1.20, and Sfg=0.27, the ηten, ηtex, and Rcm of the system can be ~61%, ~68%, and ~96%, and the average specific cost of the system is 0.024 USD/kWh, which is advanced compared with the parallel CCHP systems.