The cost of gas cleaning is likely to be more significant for oxyfuel than for other Carbon Capture technologies. This project will identify the impact of gas quality on the capital and operating costs of power plant CO2 compression, on transport systems, and on gas quality regulations for storage.
This study has confirmed the reactions, mechanisms and processes operating that deliver relatively clean flue-gas (carbon dioxide) for storage from the Callide Oxy-fuel Demonstration. The carbon dioxide processing unit design is shown to be effective, where the significant minor components are removed as condensate at the flue gas compression stage prior to transport and disposal. It shows that expensive de-SOx, de-NOx and dedicated mercury removal equipment is not necessary to clean the gas. On-site testing at the Callide oxy-fuel plant has achieved results consistent with those predicted by the laboratory studies. This research has done ‘outstanding work’ according to the Project Director of the Callide Oxyfuel Project (COP).
With the absence of back-end cleaning Australian flue gases derived from oxy-fuel combustion are expected to have higher levels of contaminants. This report provides an assessment of NOx and NOx/SOx mixture behaviour under pressure in controlled wet and dry conditions. It is part of a larger study on the interaction of NOx with SOx as well as Hg in a wet environment, such as during compression. The experiments conducted, have established the feasibility of CO2 gas quality control in oxy-combustion technology by removal of SOx and NOx gas impurities in condensates as liquid acids during compression.
The report describes a laboratory experimental program that examines gas scrubbing prior to CO2 compression to remove certain gas impurities. A laboratory-scale well stirred reactor (WSR) is developed to contact continuously flowing gas with a fixed liquid volume, used in a semi-batch mode, for examining the absorption of various SOx and NOx from oxy-fuel flue gas. The experimental operating conditions are based on pilot plant data and it is concluded that gas absorption rate is likely to be impacted by various factors, including; gas phase concentration, gas phase diffusion, gas solubility and liquid phase diffusion and reaction. The results indicate that operational conditions can be selected to minimize the consumption of the NaOH reagent yet still allow high rates of absorption during scrubbing. That is, a pH value window between 4 and 5.5 is implied for operation of practical scrubbers. Operation at pH value higher than 5.5 may lead to loss of caustic solution.
Research Organisation:
The University of Newcastle
Status:
Completed, 2014
Authors:
Anthony L Morrison, Peter F. Nelson, P. Sargent Bray
Reference:
6-0710-0061
