Greater Safety Thanks to In Situ Oxygen Measurement
Formaldehyde is one of the most widely used industrial chemicals. It is a common precursor to numerous complex compounds and materials, is a key ingredient in many resins and building products, is used as a preservative in paints and cosmetics, and is also a highly effective disinfectant.
There are two main production routes: the direct oxidation of methanol to formaldehyde using metal oxide catalysts,; and oxidative dehydrogenation of methanol using a silver catalyst.
The latter process is used by one of the largest formaldehyde producers in the US. During production a mixture of methanol and water is mixed with air and recycled gas from the process. This mixture is vaporized by heat exchange against hot reactor effluent. The vaporized feed mixture is then fed to the silver catalytic reactor to form formaldehyde.
Oxygen levels are critical
The methanol / air mixture in the vaporizer is highly flammable and the oxygen level must be maintained below the lower explosive limit (LEL). For oxygen measurement the facility was using an extractive system for drawing a sample that was then conditioned before it could be measured. The inherent time delay in the system compromised safety, so to compensate the process was run at less than its optimal throughput. In addition, the many components in the extraction and conditioning equipment were increasing the risk of the toxic process gas escaping.
In situ measurement increases safety
METTLER TOLEDO was asked to provide a solution that would provide a fast response and allow production to be safely increased.
Our GPro 500 oxygen sensor is highly suited to this application. Its tunable diode laser (TDL) technology allows it to measure directly in the vaporizerʼs outlet, so measurements are almost instantaneous. Single-flange installation means there is no danger of process gas escaping. It is also immune to the corrosive process gas.
Whereas other available TDLs have a high purge gas demand, the GPro 500ʼs unique probe design means that purge gas consumption is very low. And as there are no moving parts, maintenance is reduced to occasional cleaning of the optics and annual inspection.
Our customer reports that since commissioning they have been gratified with the sensorʼs performance, which they describe as “flawless”. They particularly appreciate the lack of servicing required which means maintenance technicians have more time for critical tasks. Thanks to the GPro 500, formaldehyde production at the plant is now safer and throughput has been increased.
Find out more about the GPro 500 at: