Digital Sensors Help Turn CO2 into Cement
The atmospheric concentration of carbon dioxide has risen from approximately 315 ppmv in 1960 to approximately 395 ppmv in 2013. With the rate of increase predicted to continue, technology companies are looking at methods to convert CO2 into more benign and useful forms. One such US company has developed a technique for converting CO2 in flue gas into a calcium carbonate cement for use in the production of concrete.
The company is proving the viability of the technology in a pilot facility located next to a large coal-fired power plant in California. CO2 that has been stripped in a scrubber from the power plantʼs flue gas is passed to a process vessel where a highly alkaline calcium-containing solution reacts with the CO2 to produce calcium carbonate. This is further processed and used as the integral constituent of cement. Manufacturing high purity calcium carbonate relies on tight control of pH in the scrubber.
Process conditions make pH measurement difficult
Periodic lab measurements of pH from grab samples would not be timely enough to allow adequate process control. However, use of in-line sensors means that they are constantly exposed to the process fluid. This quickly leads to a build-up of precipitate on a sensorʼs glass membrane and diaphragm, resulting in measurement drift that would ultimately impact product quality. In addition, staff resources at the plant are low, so regular sensor maintenance to uphold sensor performance is a great inconvenience.
Durable, low maintenance pH system
METTLER TOLEDO was asked to supply a low maintenance solution that would secure pH measurement reliability. We installed a system comprising our InPro 4260i pH sensor, InTrac 777e retractable housing, M700 transmitter, and EasyClean 400 automated cleaning / calibration system. This solution gives the facility engineers the measurement stability and reduced maintenance they require.
Intelligent Sensor Management
The system features METTLER TOLEDOʼs unique Intelligent Sensor Management (ISM®) technology platform, including digital sensor-transmitter communication. The digital signal is highly robust and immune to degradation caused by cable capacitance and interference from surrounding equipment. This further secures the reliability of the measurement received at the M700 transmitter.
ISMʼs predictive sensor diagnostics, displayed on the M700 and asset management system, means that facility engineers are constantly aware of sensor “health” and know well in advance when sensor replacement will be required.
Technicians at the facility are very pleased with the system. They are convinced that ISMʼs features give them a level of process reliability that they could not achieve with analog sensors. ISMʼs predictive diagnostics tools allow them to schedule sensor replacement for when it will be required, rather than conducting it too early or too late. The InPro 4260i, with its robust digital signal, gives them high confidence in the accuracy of pH measurements.
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