March 27, 2013

Putting the Do in Dew point: Using a C9+ Gas Chromatograph to Avoid Heavy Hydrocarbons in the Network

Hi everyone. This is Shane Hale, natural gas product marketing manager. I recently wrote an article for Pipeline & Gas Journal about using gas chromatographs to determine hydrocarbon dew point. The determination of hydrocarbon dew point (HCDP), the temperature at a defined pressure at which hydrocarbon liquids begin to form, has become critical for the natural gas industry. A big reason is that producers are focusing on extracting heavier gases in traditional and shale plays in an effort to produce more profitable natural gas liquids (NGLs) rather than the natural gas that is selling at historical lows. This has increased the risk of hydrocarbon liquids entering or forming in gas transmission networks if this rich gas is not processed fully.

The traditional method of determining the hydrocarbon dew point online is to use a chilled-mirror device that reduces the temperature of a mirror in a measurement chamber filled with the natural gas until enough hydrocarbon mist condenses on the mirror to be detected. Other dedicated HCDP analyzers using different measurement techniques are also available; however, they all provide a HCDP only at a single pressure and are dedicated analyzers that provide a single measurement.

Figure1An alternative to a dedicated HCDP analyzer is using an equation of state (EOS) to calculate the hydrocarbon dew point at any pressure from the composition obtained from a gas chromatograph (GC). By entering the composition of the natural gas into a recognized equation of state, the theoretical HCDP can be calculated for any pressure as well as the cricondentherm (the highest dew point temperature at any pressure). The validity of the calculated value depends on the accuracy of the composition used especially for the higher carbon number hydrocarbons (C6 to C9).

Fig 4 GC_700XA_transparentGas chromatographs are already used in custody transfer measurement to determine the energy content, compressibility, density, and other physical properties. Therefore, using a gas chromatograph to determine the HCDP using an EOS provides additional valuable information from already required equipment.

To learn how the C9+ gas chromatograph can be used to calculate hydrocarbon dew point at any pressure allowing pipeline operators to take corrective action before heavy hydrocarbons enter the network, click HERE. And let us know if you’re using, or have considered using a gas chromatograph at your plant!

March 6, 2013

Safe Drinking Water? It’s in the Ozone.

Hi everyone. I’m Rich Baril, product marketing manager at Emerson Process Management. All of us at Rosemount Analytical get very excited about water. Maintaining and improving water quality for municipal, industrial and commercial applications is one of our biggest jobs. Today, I want to talk about a technology being used more and more to maintain drinking water quality – whether at the treatment plant or bottling plant – and that’s ozone.

As you know, many different pathogens (bacteria, viruses and parasitic protozoa), some of which are potentially lethal, can be found in both surface water and some groundwater sources. Disinfection is integral to ensuring water quality and safety. Large-scale use of chlorine for water disinfection began in the U.S. in 1908, and chlorine is now used in both primary and secondary disinfection steps at many water treatment plants. However it has been reported that trihalomethanes and haloacetic acids are produced as byproducts of the chlorination process, and that these byproducts could be hazardous. Ozone also can produce byproducts, bromates, and much study about safe levels is being conducted.

In response to these reports, many water utilities have begun examining alternatives to chlorine for primary water disinfection, two of which are monochloramine and ozone. We will discuss ozone in this blog.

The first drinking water plant began operations in Nice, France in 1906. Since Nice has been using ozone since that time, it generally is referred to as the birthplace of ozonation for drinking water treatment. Today, some U.S. water plants are moving to ozone for disinfection to address more stringent drinking water regulations. Ozone is a powerful oxidant. Its effectiveness is measured by the amount of residual ozone remaining. The presence of a small residual implies that all organic compounds have already been neutralized.

Adding ozone to bottled water is a way to ensure that the water in the bottle is free of microorganisms, without leaving trace disinfectants.  When diffused into water, ozone oxidizes organic material, including waterborne microorganisms. It’s more effective than chemical disinfectants like chlorine and is both odorless and tasteless.  Because of ozone’s short half-life, any bottled ozonated water will have little or no remaining ozone in the solution.  It will have received an effective disinfection prior to bottling which will leave no residual disinfectant.

Ozone gas is produced by electrical discharge in air. The gas is injected into a contact chamber via diffusers to distribute the gas evenly and speed the disinfection process along. The ozone concentration in the contact chamber, where reaction is still occurring, can therefore be much higher than in the final effluent. Some ozone generator manufacturers recommend monitoring ozone concentration in the contact chamber to meet disinfection requirements. Aside from the capital cost of the ozone generator itself, the main cost of an ozone system is the electricity used.

Have you used or considered using ozone for water treatment? What was your experience? We’ll be happy to talk with you about the effective use of ozone in your water treatment or bottling plant – just let us know!