The energy revolution has also brought to light the fact that carbon dioxide is only a bad thing when it is released into the air. If, however, CO2 is captured and stored, it could make a significant contribution to reducing CO2 and generating “green” products. Carbon dioxide is the key ingredient in the power-to-gas concept, for example. This technology involves storing renewable energy in the form of synthetic methane gas to provide a combined solution that both reduces CO2 and allows problematic green power surpluses to be stored. What’s more, CO2 forms part of the process for producing plastics which are free of petroleum.
Many methods are currently being tested to supply raw materials for rubber and plastics for a wide range of everyday products such as trainers and disposable tableware. In theory, we could recover valuable carbon dioxide directly from the air – but there is no way that would be profitable. However, a win-win option would be to separate the CO2 from the exhaust gas emitted by conventional power stations or industrial plants and to transfer it to a suitable CO2 recovery process so that the CO2 can be stored. The recovery process would involve removing most of the carbon dioxide from the flue or exhaust gas by means of a chemical or physical solvent. Around 85 to 90 percent of the CO2 could be separated in a profitable manner using this method. The separation process in the raw gas/ purified gas is monitored by analyzers and gas flow meters from SICK.
Transporting CO2 back underground
An affordable way of making a significant reduction to CO2 emissions may be provided by carbon capture & storage (CCS). Rather than releasing fossil carbon dioxide into the air, it is captured either during the process or before it reaches the chimney and preferably permanently sequestered in layers of the earth that contain salt water. The technology may prove to be particularly attractive for countries such as China or Poland who produce most of their power from fossilfuel power stations. With CCS, the oxyfuel principle only has a relatively small impact on its efficiency. The method has also been trialled successfully at a German testing facility where SICK analyzers were used. The oxy-fuel principle involves the combustion of carbon dioxide with pure oxygen and recirculated gas. This produces water and carbon dioxide. To ensure that the CO2 can be stored as efficiently as possible, it must be extremely pure. It passed this test with flying colors: Optimum qualities were achieved thanks to a purity level of up to 99.7 percent. Analyzers from SICK played a key role in this: once the dust had been removed, the MCS100E HW extractive multi-component analyzer system recorded the fluctuating sulfur and CO2 concentrations in the damp raw gas without any problems, despite the different combustion capacities and fuels used. Following desulfurization, the MKAS multi-component analyzer system with SIDOR then monitored the sulfur dioxide and CO2 in the purified gas as it was being supplied to the separation facility. The FLOWSIC500 gas flow meter ensured that the gas flows were measured precisely. If geological storage is to be used to sequester the CO2 quantitative and qualitative measuring tasks would also be necessary, in particular to identify any leaks.
Giving plants an extra helping of CO2
Do plants have a maximum limit with respect to the amount of carbon dioxide they can take in during photosynthesis? Algae, a popular raw material for pharmaceutical products and the production of biodiesel, like to be fed plenty of CO2. Carbon dioxide is a source of nutrients for algae and nitrogen oxides act as a fertilizer. Both are fed back into the natural cycle of materials. At an algae cultivation pilot plant operated by Subitec GmbH and EnBW, exhaust gases from a biomass power station were used and monitored with measuring technology from SICK. The rate of CO2 reduction was determined by measuring the difference at the plant’s inlet and outlet. The SIDOR extractive NDIR gas analyzer from SICK was used here. If the CO2 concentrations required for algae to grow are known, the plant can be controlled in an optimum manner. Monitoring the dilution of the exhaust gas with ambient air controls the concentration. The GMS800 gas analyzer with the DEFOR analysis module, which operates based on the UVRAS principle, also tested the extent to which the algae are able to use NO or NO2 as fertilizer. The associated analyzer system was set up outdoors and with a temperature control system. Similar to the process used in an industrial greenhouse. Here, tomatoes are also naturally strengthened with carbon dioxide and small quantities or nitrogen which acts as a fertilizer. SICK’s approved MAC800 modular analyzer system controls the process.
The supply of NOx is converted into natural air/nitrogen and water by injecting a reduction agent and using a downstream catalyst in an SCR denitrification plant. Measuring the NOx with the GMS800 DEFOR helps ensure that the reduction agent is precisely metered and reduced to a minimum. The emissions limits are also reliably monitored.