TECHNOLOGY

The Petroleum Environmental Research Forum (PERF), a consortium of six major oil companies, has accepted a new HF detection technology for use in its member refineries.

The instrument, called SpectraScan, is manufactured by Spectrum Diagnostix of Andover, Mass. It uses tunable diode-laser spectroscopy to detect HF emissions.

The detection technology was proven successful during a 5-month commercial trial in an Exxon Corp. refinery.

Technology development

During the past 3 years, PERF companies have been working with Spectrum Diagnostix to develop a so-called open path monitor for detecting fugitive species of toxic gases released from refineries.

PERF's goal for the development project was to use tunable diode-laser spectroscopy to measure HF and H2S at the process unit fence line (hence the term "open path"). Fig. 1 shows how the laser is used to monitor refinery fugitive emissions.

PERF cofunded the development project with Spectrum Diagnostix, which used its tunable laser technology as the basis for the new instrument. PERF comprises Amoco Corp., BP, Chevron Corp., Exxon Corp., Mobil Corp., and Phillips Petroleum Co.

Technology

Traditional point monitors measure HF concentrations in a single location. These systems trigger an alarm only if the contaminant is detected in the immediate area of the monitor. By contrast, the new laser technology detects HF around the perimeter of the alkylation unit.

"The...perimeter monitor is not intended to pinpoint the location of an emission," said Patrick McDonnell, president and chief executive officer of Spectrum Diagnostix, "but to notify the refinery of an emission, the relative concentration of that emission at the fence line, and to do so with response times and sensitivity permitting initiation of mitigation scenarios if necessitated."

The device incorporates recent advances in diode lasers and optical fibers.

"SpectraScan is capable of simultaneously monitoring sub-ppm gas concentrations along four independent paths up to 200 m in length," said Jim Melnyk, SpectraScan product manager for Spectrum Diagnostix. "The transmitting laser source is located in a control console and optically connected to each of the measurement paths, which can be positioned up to 1 km from the source."

The system is designed to operate free of interference in extremely harsh environments and climates. It operates continuously and performs diagnostics and self-calibration automatically, says Melnyk.

Trials

Two perimeter monitors have been operating in separate HF alkylation units for a total operating time of 1 year, said McDonnell. During a 5-month trial at an Exxon refinery, the system experienced neither instrument failures nor false positive readings.

Mobil is installing the system at a second HF alkylation unit, says Melnyk.

The monitor also can be used to detect H2S emissions from sulfur-recovery units. Beginning in February, the company will begin testing a second version of the instrument to measure H2S at a Canadian refinery.

Spectrum Diagnostix is adapting the instrument for use in a variety of emissions monitoring and process control applications in the chemical processing and power industries. Its development partner is Bovar Western Research, Calgary, Alta.