Stability studies of a novel amine blend for the capture of CO2 generated from indirect co-combustion of natural gas and biomass

Abstract

The excessive release of CO2 from human activities has led to global warming and climate change, becoming a critical global issue for many years. Data released by the Environment Protection Agency of United States in 2022 clearly shows that, CO2 is the most emitted gas among other greenhouse gases. In response, numerous strategies have been developed to address this pressing problem. One particularly compelling approach is to use an optimal mix of fuels in combination with post-combustion capture technology to achieve net-zero or even negative CO2 emissions. Over the past years, solvent absorption in post-combustion capture technology has shown significant reliability and efficiency in reducing CO2 emissions. Despite this, investors face major challenges such as the cost of solvents, solvent loss, and the expenses involved in solvent regeneration. Monoethanolamine (MEA) is the most extensively studied alkanolamine absorbent and serves as the benchmark for evaluating other absorbents. MEA is recognized for its high absorption rate, low cost, and low viscosity. However, MEA is prone to a high degradation rate, which leads to significant solvent loss. In the field of CO2 capture, degradation refers to the diminished capacity of the solvent to effectively capture CO2 as expected during the capture process. This degradation is primarily caused by undesirable side reactions between the absorbent and impurities in the flue gas, such as oxygen, NOx, SOx, particulate matter, and heavy metals. Degradation is an endothermic reaction so the process is favoured at high temperature in the presence of these flue gas impurities. Solvent degradation is an important parameter to consider during solvent selection for commercial use in CO2 capture process. It does not only lead to solvent loss but degradation products like carboxylic acids and heat stable salt (HSS) promotes corrosion. Also, nitrosamines emitted due to some absorbent reaction with NOx poses threat to human health. There are chances of fouling and solvent foaming due to degradation. Least to mention is the increase in cost of operation due to increase in heat duty required for regeneration because of the presence of degradation products. This work demonstrates the stability of 4M AMP:1-(2 HE) PRLD. The novel amine blend was subjected to some conditions mimicking CO2 capture for flue gas generated from indirect cocombustion of natural gas and biomass. When it was compared with a known amine blend, thus, 5M MEA:DMAE under same conditions, 4M AMP:1-(2 HE) PRLD, proved to be inherently more stable. It had a 33% increase in its rate in degradation as against 80% increment when the oxygen partial pressure was doubled keeping all other conditions constant. This implies the novel amine blend is stable and can be used commercially for the capture of CO2 from pretreated flue gas. The results highlight its resilience and potential for long-term application in environments where oxygen levels may fluctuate without succumbing easily to the degradation processes that typically affect similar compounds. A kinetic model was generated for the rate of degradation and it is of the form: r( hr M ​ )=6.8222×10 9 e(− 8.314×T 50314.08 ​ )[O₂] 1.3