Monitoring & metering


from Vaisala to measure carbon capture efficiency and therefore CCUS viability. The researchers have developed a pilot plant


to remove CO2 from the emissions of the incinerator at the Amager Bakke Waste-to-


Energy Plant, which is one of the largest combined heat and power (CHP) plants in northern Europe, with the capacity to treat 560,000 tonnes of waste annually. Developed by the Copenhagen-based waste management company ARC (Amager Ressourcecenter), which is jointly owned by five Copenhagen- area municipalities, the CHP plant features a number of innovations including a rooftop artificial ski slope, which is part of an outdoor activity centre known as CopenHill. The pilot plant was developed to capture


CO2 from the emissions of processes such as wastewater treatment, biogas production,


anaerobic digestion and waste incineration. However, the researchers are also investigating


the ways in which CO2 can be both captured and utilised. Prior to its installation at Amager Bakke, the pilot carbon capture plant was operated at a wastewater treatment plant. “The technology itself is not new,” explains Jens Jørsboe, a researcher from the DTU, “However, the focus of our work has been to lower the cost of carbon capture, so that it can become economically feasible.” Exhaust gas from the Amager Bakke incinerator is passed through an electrostatic precipitator (ESP) to remove particulates, NOx compounds are removed by selective catalytic reduction (SCR) and a scrubber removes


oxides of sulfur. High levels of CO2 remain in the flue gas and the main purpose of the pilot carbon capture plant is to investigate the feasibility of its capture. To achieve this, the gas


Credit: Hufton&Crow / ARC


is passed upwards through a column packed with beads and a monoethanolamine (MEA)


solvent which scrubs the CO2 from the gas. The solvent is then passed to a desorber which


removes the CO2, which is now almost pure, and regenerates the MEA for re-use. As a


research project the produced CO2 is currently still vented to air, but on a commercial basis there are many different


industrial applications in which CO2 can be utilised. For example, CO2 can be reacted with hydrogen in the Sabatier process to produce


methane (a gas fuel) and water, at elevated temperature and pressure, in the presence of a


nickel catalyst. This can be a green method for manufacturing fuel if the hydrogen is generated by electrolysis using renewable energy – from solar, biogas or wind power for example.


CO2 is also used in a wide variety of other industries including food and beverages, refrigeration, medical, horticulture, firefighting, welding etc., so a variety of potential markets


are available if CO2 can be produced on a commercial quality and scale.


MONITORING CARBON CAPTURE EFFICIENCY


The optimisation of the carbon capture


process can only be achieved if CO2 concentrations can be continuously monitored both before and after the carbon capture process. It was fortunate therefore that the


world’s first inline CO2, humidity and methane monitor was developed by Vaisala in Finland prior to the pilot plant construction. Exhaust gases from incinerators can be


corrosive and potentially explosive, so in the past it has not been possible to conduct in-line monitoring. Until recently, the only solution was to extract samples for analysis outside of the process, but this method is not suitable for process control and optimisation, and has a number of inherent flaws, such as the need to remove humidity from the sample line and a requirement for frequent re-calibration. The development of Vaisala’s multi-gas


probe, the MGP261, resolved all of these monitoring challenges, especially when it was followed by a sister product the MGP262, which was adapted for measuring high


concentrations of CO2 and was therefore ideal for the continuous inline monitoring of almost


pure CO2 after the pilot plant’s desorber. The pilot plant employs three Vaisala probes


in total, with the MGP261 monitoring incoming incinerator exhaust gas, and the MGP262


Instrumentation Monthly April 2022


Continued on page 16... 15


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