Moisture measurement in carbon sequestration and utilisation

How to ensure carbon dioxide gas quality and process efficiency 

In recent years there has been growing interest in Carbon Capture and Storage (CCS) as a potential tool in the fight against climate change.  The process works as follows: 

1. Carbon dioxide (CO2) is extracted from power generation and industrial processes.

2. The gas is compressed before being injected back into disused underground oil and gas fields.

3. This can reduce the amount of CO2 entering the atmosphere.

CCS is already widely used as a means of extracting the last commercially viable oil and gas reserves from depleted fields.  As fossil fuels are rapidly being replaced by renewable energy sources, the focus is now on getting CCS projects up and running as soon as possible.   

According to the International Energy Authority there is between 8,000 and 55,000 Gt of underground CO₂ storage capacity; used alongside other carbon reduction technologies, this will be sufficient to meet our global net zero emission targets.

The two aspects of carbon sequestration

CCS is only part of the story.  Equally important - and perhaps of greater commercial value - is Carbon Capture and Utilisation (CCU).  This technique involves the extraction of CO₂ emissions at source from coal or gas-fired power plants, chemical, cement or steel plants, or biomass energy facilities.  Once CO₂ has been processed to produce gas of the appropriate quality, it can be used as a feedstock for a range of products, including:

However, in many Applications, the process of extracting, purifying and reusing CO2 consumes considerable amounts of energy, so the use of renewable energy is a key aspect of a viable CCU process.  In other areas, notably in the production of building materials, where CO2 is combined with calcium-rich minerals to create calcium carbonate for use as aggregate or in cement manufacture, much of the process is exothermic and requires relatively low levels of external energy.  

Another consideration is that many of the products made from the recovered CO2 will release the gas back into the atmosphere at the end of their useful life, as they decompose or burn.  Ideally, the gas is recaptured and processed again to create a closed loop cycle.  In practice, of course, this may not happen, so this factor must be taken into account when assessing the value of a CCU project.  In contrast, products such as concrete and carbonated plastics, or carbon additives for nanotubes and graphene, may not release CO2 if they convert it into another chemical during manufacture.   

Gas quality is critical to the success of CCU deployment

CCU shows considerable potential; however, success depends on how efficiently CO2 can be extracted and processed to produce gas of the right quality for use as a feedstock.   Ideally, CO2 should be captured and used in the same facility.  In many cases, however, this will be impractical, as the gas will need to be compressed and transported through a pipeline distribution network. 

Inevitably, CO2 captured from power generation or industrial processes contains impurities.  These need to be removed, reduced in concentration or otherwise treated before the gas can be used.  In addition, the distribution process may introduce contaminants through leaking pipes, for example.  Therefore, treatment of the gas will be necessary both at the initial extraction and compression stage and at the point of use.  

The nature and concentration of impurities varies from process to process and may include sulphur, nitrogen and oxygen, as well as chemicals that may carry over from systems used to separate CO2 from flue or industrial gases.  The need to remove moisture by cooling and dehydration of the CO2 will also be common.  

Moisture measurement and removal 

The presence of moisture in the form of vapour or liquid in CO2 can pose a number of quality, efficiency and safety problems.  The most obvious problem is corrosion of the surfaces of steel piping and distribution equipment, with the consequent risk of leakage and damage to compressors used to pressurise the gas.  Other problems include the risk of reaction between water vapour and CO2, or other impurities such as hydrogen sulphide, to form aggressive acids such as sulphuric carbonic acid; again, these will attack and degrade metal surfaces and rubber or plastic gaskets on piping and other equipment.  

Monitoring the presence of moisture requires specialised detection and analysis instruments.  These must be extremely reliable, accurate and capable of providing consistent readings over time.  These instruments must also meet appropriate quality and safety standards and be supported by a manufacturer with experience and expertise in measuring moisture in demanding industrial process applications.  

Two instruments that meet these criteria are our QMA601 and QMA401 quartz crystal moisture analyzers, offering fast response to process moisture changes, with built-in, automatic functions to ensure long-term accuracy and original factory calibration traceable to national standards. As you would expect from one of the world's leading manufacturers of sensors and instrumentation, these moisture analyzers are backed by a comprehensive range of technical support services.  

With 50 years of experience in developing innovative precision instrumentation, we are experts in moisture measurement applications for all carbon capture and storage applications. If you would like to discuss your requirements, please contact us. contact our team today.   

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