Monitoring Formaldehyde in a Chipboard Manufacturing Plant
- The Photoacoustic Field Gas-Monitor - INNOVA 1412
The manufacturing process to produce chipboard commonly uses Formaldehyde. Formaldehyde is a toxic, carcinogenic gas, which affects the mucus membranes such as the lungs, eyes and nose. At low concentrations, its effects cause a mild irritation, while at higher concentrations inhalation of the gas can result in death. Egger (UK), a subsidiary of an Austrian company which has manufacturing sites in several European cities, manufactures chipboard in Northern England. In order for Egger (UK) to produce chipboard at this site, the HMIP (The UK pollution inspectorate) required that the plant measured, on a continuous basis, the vent emissions of formaldehyde to the atmosphere.
A Need for Multi-point Sampling
Traditional methods to measure Formaldehyde are normally time consuming, labour intensive and require expensive chemicals and laboratory facilities – increasing the running costs. Egger (UK) decided that in addition to measuring vent emissions, they would also measure fugitive emissions and ambient levels within the factory boundary. This meant they required a multi-point sampling system that could simultaneously measure in 4 separate areas. They also wanted to be able to measure TOC levels during the process, which meant a multi-gas measurement capability must be included in the system. As legislation required vent emissions to be measured, the system must provide some form of hard copy of the measurement results as documentation to prove to the authorities that the process was running as planned. Egger (UK) also decided, as an extra safeguard for the workers, the system must provide real-time results that could be linked to an alarm system. This alarm system would be triggered if the concentrations exceeded the permitted values.
The Tested Technique
A Multi-gas Monitor - INNOVA 1302 was installed. This monitor, with it's photoacoustic (PAS) measurement technique and narrow band optical filters, is capable of measuring up to five gases simultaneously. The filters chosen for this application and the gases they measure are shown in Table 1 below.
Gases Filter- Detection Formaldehyde UA 0986 0.04 ppm<//font> |
Table 1: Gases to be measured and filters installed
The Solution
Although the UA0986 filter was chosen for Formaldehyde, both Methanol and Dimethylether, present onsite, absorb in this filter's absorption range. Additional filters were included to enable cross-compensation for Methanol and Dimethylether. In addition to the INNOVA 1302, a sampler was installed. These were housed in an analyzer house within the plant. The vent was approx. 100m from the proposed instrument position (away from any zoned areas). The other sampling points were 50, 25 and 100m from the monitor. The high dew point in the scrubber meant that heating of the sampling system was needed, to avoid condensation in cold weather in the sample tube. Heated sampling lines were run through the plant to the sampling points. A coalescing filter was also installed as an additional safeguard to protect the monitor's measurement cell. An external pump was connected to the sampling lines enabling all the lines to be constantly purged to a common manifold. This reduced any measurement time delay (measurement results available every two minutes). Only the line to be sampled is diverted to the monitor. The monitor's own internal pump provides the sample. Result data for all four gases is passed, via an RS–232 interface, to a printer to produce a hard copy. The samples can be identified by the "channel number data" provided by the sampling system. The system has no expendable parts and the monitor's inherent stability means it only requires recalibrating approximately twice a year. So, once the measurement procedure is started the monitor can measure without any user intervention. The need for an alarm system is covered by the monitor's built-in beeper and Alarm Relay socket. The beeper warns staff working close to the monitor that the measured concentration has exceeded the alarm level, while the relay socket enables remote alarms to be connected to warn staff working in other parts of the factory. This is a feature Egger (UK) have ear-marked for future development.
Conclusion
Even though the authorities demand a continuous monitoring system, which are often time consuming for those who have to operate them, by installing this system all the data and documentation necessary to satisfy the authorities are available without requiring more time from the workers. In addition to this, this monitoring system ensures the health and safety of the workers.