Flue gas treatment by power-to-gas integration for methane and ammonia synthesis – Energy and environmental analysis

Abstract

The present paper aims at assessing the carbon and energy footprint of an innovative process for carbon dioxide recycling, with flue gas as feedstock of nitrogen and carbon dioxide. Nitrogen is converted into ammonia through the Haber-Bosch process and carbon dioxide into methane via Sabatier reaction using hydrogen produced by renewable electricity excess. Carbon and energy footprint analysis of the process was assessed based on experimental data related to hydrogen production by electrolysis, methane synthesis via Sabatier reaction, energy consumption and energy output of the process units for flue gas separation, carbon dioxide methanation and ammonia synthesis. A Life Cycle Assessment method is applied, based on the experimental and computational data, both in case of renewable electricity excess and electricity from the grid. Results show that in case of renewable electricity excess, for a functional unit of 1 kg of treated flue gas, the specific carbon footprint is 0.7819 kg CO2eq and energy footprint is 50.73 MJ, which correspond to 4.012 kg and 260.3 MJ per 1 kg of produced hydrogen. In case of electricity from the grid, the specific carbon footprint is 1.550 kg CO2eq and energy footprint is 59.12 MJ per flue gas mass unit. If the carbon footprint is positive, the process indirectly leads to avoided emissions, ranging from 0.673 to 0.844 kg CO2eq kg −1 fluegas , thus proving the sustainability of the proposed pathway.

Natural Gas Engine Technologies: Challenges and Energy Sustainability Issue

“…There is a recent initiative of producing methane through power to a gas solution in view of storing excess renewable electricity [152], CO 2 capture, and flue gas treatment [153]. Methane can be produced through this solution in two steps.…”

Waste Heat and Water Recovery System Optimization for Flue Gas in Thermal Power Plants

“…Many studies are being conducted to find ways to utilize flue gas to reduce carbon footprints; these include employing it in the synthesis of methane and ammonia [1], as well as investigations focusing on waste heat recovery and utilization. Some studies focus on the reuse of exhaust gases for co-generation [2] and the use of this energy for pre-drying in coal power plants, which increases the thermal efficiency of the system by approximately 2% [3].…”

Elemental Composition and Flue Gas Emissions of Different Components from Five Semi-Arid Woody Species in Pyrolysed and Non-Pyrolysed Material

“…However, a decade after its implementation, the official reports of the United Nations (UN) and Non-Governmental Organizations (NGOs) exposed serious unforeseen consequences to the increase in the international production and consumption of biofuels [5], which raises further questions about the social, economic and environmental benefits or harms of large-scale production. As a by-product of fuel combustion [6], flue gas is composed of Greenhouse Gases (GHG) that consist of CO 2 , N 2 , oxygen (O 2 ) and water (H 2 O), sulphur dioxide (SO 2 ), nitrogen oxides (NO x ) and hydrogen chloride (HCl), entailing negative effects on the environment [7]). Therefore, burning biomass is a precursor of significant amounts of short-living global warming substances, such as black carbon, and also significantly contributes to ozone formation by photochemical reactions among its precursor VOCs and NO x [8].…”