|Working safely with CO2|
|By Erik Meuleman, Team Leader and Project Manager CCS, CSIRO|
|Since 2008, CSIRO has been capturing CO2 from flue gas produced at AGL Loy Yang’s 2,200 MW power station in the Latrobe Valley, Victoria. Successive research projects with CSIRO’s post-combustion capture of CO2 (PCC) pilot plant at Loy Yang have been funded by Victorian State governments through its ETIS program and Brown Coal Innovation Australia (BCIA). The research has shown that the pilot plant can readily capture 90% of CO2 from the processed flue gas. CSIRO has evaluated its own capture systems, and also through research collaborations has evaluated the systems from world-leading entities such as RITE / Chiyoda (Japan), TNO (EU), Texas University (US) and currently IHI (Japan).|
Liquid absorbent capture technology involves selective removal of CO2 from the flue gas. The flue gas is passed through a gas-liquid contactor column, where CO2 is chemically bonded to a liquid absorbent containing ammonia, amine or an amino acid. The liquid is then pumped to the regenerating column where heat is used to release CO2 from the liquid and produced at the top of the column, whilst from the bottom the liquid is recycled to the absorption column.
The PCC pilot plant is a small process plant using chemicals unfamiliar to the power generation environment. It requires the CSIRO and AGL Loy Yang to closely work together to develop (new) safety protocols appropriate to PCC. AGL Loy Yang’s safety vision is all about ‘No Harm’ – every person at AGL Loy Yang working together to create a ‘No Harm’ workplace. A range of ‘No Harm’ policies, work practices and standards are in place to achieve a safe work environment at the site; CSIRO operates under its own strict safety protocols and AGL’s ‘No Harm’ policies. For example, every new absorption liquid is risk assessed for its cradle to grave potential impact before being authorised for use on site. This includes detailed risk assessment from entrance, to storage, and actual use, through to eventual end of life waste streams.
Apart from the chemicals used in pilot plant, the project must deal with a range of other hazards. The obvious compound requiring attention is CO2. The symptoms of CO2 intoxication include light headiness, which is quickly followed by an inability to leave the hazardous situation. In a power plant, CO2 is generally encountered in the form of flue gas, which has a distinctive smell and allows someone some time to leave the hazardous situation. Purified, concentrated CO2 however is odourless.
CO2 enters our plant in a dilute form as part of the flue gas; both CO2 and flue gas are classified as asphyxiants. CO2 is subsequently concentrated in our pilot plant to greater than 96% purity in the product stream. The production rate of CO2 is typically 20 kg/h, and at this research plant scale is discharged through the power station flue gas duct.
An advanced gas analysis system, capable of simultaneously analysing 20 gases from one sample, has been installed at the pilot. The CO2 concentration typically ranges from 10% in the feed to 1% in the outlet, higher than 96% in the product stream and about 400 ppm in ambient air. The system consists of long lines of tubing that lead the gas from the respective samplers to the gas analyser and is then vented to atmosphere.
Since the gas analyser is indoors extra precautions are required. To prevent a hazardous situation from occurring multiple layers of defence are implemented. For example, all inlet lines to the gas analyser are under negative pressure, which implies that in case of an accidental leak air would be drawn into the line and prevent unintended release of gases. Only the exit of the gas analyser has a minor positive pressure induced by a pump in the analyser. Minor gas flows through the line are piped to an external exhaust, which has a visual check for correct operation. During monthly maintenance checks all indoor gas lines are checked routinely to ensure they remain in sound operable condition.
|Additionally, an O2 alarm is in continuous operation, which alerts personnel once the O2 concentration drops below 19.5%, whereas commonly air contains 20.9%. Simply breathing into the sensor sets it off. The room is also equipped with a CO2 sensor and alarm. Despite the engineering solutions and electronic controls in place, we add another layer of defence by making it a compulsory site safety rule for all personnel to ensure that the doors to the room must be open for a minimum of 5 minutes prior to entry. This allows natural air circulation as a final layer of defence for poor air quality in the analysis room.|
|Figure 1: Gasmet FTIR.|
|We are convinced that the range of present safety measures adopted at the Loy Yang facilities have assisted other potential project partners to have their new capture system safely evaluated in this or other PCC pilot plants that CSIRO operates in the three Eastern states of Australia. AGL’s No Harm policies and support has assisted CSIRO to safely conduct on-line CO2 capture in operational power station environments.|
|Figure 2: CSIRO’s PCC pilot plant at AGL Loy Yang.|
|For further information please email email@example.com or visit csiro.au website.|