Abating Volatile Organic Compounds in Low Pressure (ATMOSPHERIC) Hydrogen Process Flows Using a Regenerative Thermal Oxidizer

Thermal oxidizers are a well-known technology for the destruction of volatile organic compounds (VOC). Regenerative thermal oxidizers (RTO), an EPA referenced technology for VOC abatement, was found to be a very attractive option to abate VOC’s in our laboratory environment.

Our laboratory conditions produced challenges in managing the operation of the RTO. The VOC’s that needed to be abated were in a process flow that included up to 95% of hydrogen by volume. The laboratory test work, being variable in nature, resulted in process flows between 50 scfh and 1300 scfh, which the RTO needed to accommodate midstream during operation. These low process flows led to the design and building of a unique, small size, RTO to abate the VOC’s.

The complexity of the process flow into the RTO was further compounded by the need to maintain vacuum conditions in the inlet line. Vacuum conditions increase the propensity for air leaking into the piping system, with the potential of air mixing with the hydrogen in the process line, creating combustion prone mixtures. Therefore, flame arrestors, monitoring equipment and alarms were put in place to ensure safety during operation. Vacuum conditions in the system impacts the fan/blower selection and the burner system for the RTO.

In addition to the operational conditions, we discuss the instruments and controls for the continuous monitoring of VOC’s and Hydrogen. The availability of an instrument, to measure in real time, the LEL levels was not an off-the-shelf purchase and required much experimentation to identify a viable, long-term solution. To understand the stoichiometry of hydrogen-air in the region where the air is mixed with the process flow, we present the results of the computational modeling work that we did and the safety precautions we took with the piping in this mixing region.