*5.2. Coal-Based Super-Critical Combustion Power Plants*

To quantify the techno-economic and environmental impact of the decarbonization process for the coal-based, super-critical, combustion-based, power generation using post-combustion capture systems, the next power plant concepts were used as illustrative examples in this work:

Case 2.1—Conventional combustion-based power plant without decarbonization; Case 2.2—Decarbonized power plant based on reactive gas-liquid absorption (MDEA); Case 2.3—Decarbonized power plant based on reactive gas-solid system (CaL).

The non-capture concept (Case 2.1) is based on current industrial design having 500 MW net output [19]. For the assessed decarbonized concepts (both having the same plant decarbonization degree—90%), the additional heat and power consumptions required for CO2 capture are covered by the main power block. The most important techno-economic and environmental performance indicators of evaluated coal-based super-critical power plants are summarized in Table 3.



As presented in Table 3, the decarbonization penalty for super-critical power plants lays between seven to nine net energy efficiency percentage points (for the same decarbonization rate considered in both options—90%). The post-combustion calcium looping decarbonization system shows improved values in comparison to the chemical gas-liquid absorption scrubbing system. The difference in net power efficiency points for the two decarbonization systems is about 1.62. This value is justified by the high-temperature heat recovery potential of the calcium looping cycle. The specific consumption of primary energy for CO2 avoided (SPECCA) also shows better value for chemical looping in comparison to chemical scrubbing (gas-liquid absorption) by about 0.67 MJ/kg. All these technical and environmental benefits of the CaL-based decarbonization process translate into improved economic performance [35]. All economic indicators are in favor of the calcium looping option in comparison to the gas-liquid absorption as assessed decarbonization technologies—specific investment cost (reduced by about 25%), levelized cost of electricity (reduced by about 18%), and CO2 avoided cost (reduced by about 36%). Also, it worth mentioning that the combustion-based power generation is cheaper than the gasification-based power generation in a non-carbon capture scenario, but when carbon capture is implemented, the economic differences are reduced significantly or even are in favor of IGCC power plants (see Tables 2 and 3).

To illustrate an in-depth environmental impact evaluation for the assessed super-critical power plants with and without carbon capture, Table 4 presents the Life Cycle Analysis (LCA) results in a cradle-to-grave approach using CML 2001 method. The full technical details of this LCA analysis are presented in the paper indicated as reference [31].



It can be noticed that the carbon footprint (noted here as Global Warming Potential—GWP) is reduced with plant decarbonization (not corresponding to 90% plant decarbonization rate but to a lower rate due to up-stream and down-stream processes). All other environmental indicators are increasing with plant decarbonization; in some cases, the increasing rate is quite high (e.g., acidification potential, indicators related to toxicity, etc.). It worth mention that for the calcium looping system, all environmental indicators have better values than for the reactive gas-liquid absorption system. The main reason for this result represents the lower environmental impact of natural-based calcium sorbent in comparison to a chemical-based solvent.
