Measuring H2S in CO2 Bottling Gas

OMA H₂S Analyzer 

Reprinted with permission from Applied Analytics

Prior to filling, beer bottles are purged with CO₂ to remove air and protect the taste against oxidation. In the fermentation process, yeast consumes sugar and expels a large amount of CO₂ which can be "reclaimed" and used for this bottle purging purpose. Unfortunately, fermentation often also produces toxic, odorous sulfides which can foam up into the piping and contaminate the reclaimed CO₂.

In order to continue using the great resource of CO₂ byproduct yet avoid contaminating the bottled beer with foul-smelling toxins, the reclaimed gas is run through sulfide removal skids. However, sulfide breakthrough can occur if the gas does not spend enough time in the scrubber. Employees are sometimes tasked with sniff-testing the reclaimed CO₂ , but this is an unhealthy practice and is too discrete to vigilantly prevent product contamination.

An automatic, continuous analysis solution is required in order to immediately divert contaminated CO₂ from use in bottling as well as provide feedback control for the sulfur removal processing time.

The OMA H₂S Analyzer is used to continuously measure concentrations of hydrogen sulfide (H₂S) and dimethyl sulfide (DMS) in the fermentation byproduct gas. This system uses a full-spectrum UV-Vis spectrophotometer to detect the absorbance of sulfides in the reclaimed CO₂ stream, an ideal method as CO₂ has zero absorbance in the UV spectrum. The OMA provides fast response alarms to high-concentration threshold which allows immediate diversion of contaminated CO₂.

For this application, the OMA is typically multiplexed to automatically cycle analysis between multiple sampling points. This maximizes system value by allowing one unit to monitor the raw fermentation gas entering the reclamation system, gas coming off the acid aldehyde scrubbers, and the bottling gas coming off of the sulfur removal beds -- all with sample stream switching at user-defined intervals.

Remote Sensing of Gases Directly in the Process

Electric Power Plant

Industrial operations, whether for direct process control or emissions compliance monitoring, have a need for accurate, reliable measurement of specific gas concentrations within a flowing medium. Tunable diode laser spectroscopy, packaged for industrial use, provides a number of substantially positive attributes.

• Rapid measurement.
• Can be focused on a specific component of interest.
• Multi-channel operation provides analysis of several components.
• In situ installation can provide direct measurements within a stack, pipe, or duct without sample handling or conditioning.
• Can measure NH3, HF, HCl, H2O, CO, CO2.
• Internal reference cell provides long term stability.
• Some models have continuous automatic calibration.

Siemens manufactures a line of tunable diode laser gas analyzers for industrial applications. In the company's own words, here is a basic description of how it works.

As a tunable diode laser-based technology this in-situ device enables high-performance measurements. The sensors (transmitter and receiver) are meant to be mounted directly on the process with no need of sampling systems. Laser light is sent from the transmitter, passing through the process gas, arriving at the detector on the receiver side. The measurements are carried out on-line with a very short response time permitting fast and effective cost-savings in process control. The laser characteristics allow single-line spectroscopy free of interferences. Since the band width of the laser light is extremely narrow, only the gas component of interest will interact with it. Other process influences, such as dust and temperature, are easily eliminated due to the excellent inherent compensation capabilities of this technique.

There is application assistance and more detailed information available from knowledgeable sales engineers in all localities. Combine your process mastery with their product application resources to meet the challenges posed by modern industrial process operation.

Sitrans Tunable Diode Laser Gas Analyzer from Ives Equipment