#165 - Nova Analyzers from the Field – Episode 3

These pictures had us scratching our heads for a while. The analyzer installation is on a roof in South Africa at a plant that produces aluminum chlorohydrate. According to Wikipedia, aluminum chlorohydrate is used in deodorants and anti-perspirants and as a coagulant in water purification. This South African plant makes it in a reactor containing aluminum ingots, hot water, and aluminum chloride solution.

One by-product of the reaction is hydrogen and that is the gas they wanted to monitor on this site. Possibly because the concentration of H2 is an indicator of the pace of the reaction. High or low H2 content may trigger an adjustment in the addition rate of the aluminum chloride or the aluminum ingots.

The Nova analyzer is easy to identify. It’s the cabinet with the round port-hole, in the center of each picture. This is a Model 430N7MC Hydrogen analyzer with explosion-proof cabinet.

The other components attached to it were more difficult to identify. These were evidently the work of the original installer. From the site staff explanation, there is apparently a vortex-style cooler, a ‘silencer’, and a knock-out pot. We assume that the vortex cooler is intended to cool the gas and cause the moisture to condense and fall out in the knock-out pot. The ‘silencer’ is perhaps to regulate noise or velocity associated with the compressed air input (?). The intentions are good, but the implementation seemed questionable.

A vortex style cooler separates cold and hot fractions of air by spinning them very quickly. They require an input of compressed air in the side, and the hot and cold flows usually emerge from opposite ends of the tube. None of the components in the pictures seem to have that exact configuration. So we were uncertain about the correct operation of the installation.

We were also somewhat confused by the requirement for an explosion-proof analyzer. The components installed ahead of the analyzer do not seem to reflect this requirement.

Our concerns with the tubing layout and functionality of the parts were confirmed when it was revealed that the moisture system was not working properly and was allowing corrosion deposits to form in the system. The deposits were also apparently contributing to sporadic Low Flow alarms in the analyzer.

On the right side of the analyzer is a data collection cabinet or control device of some kind. The analyzer is equipped with a 4-20mA output corresponding to the range of gas analysis. This output is no doubt connected to the process control panel. Adjustments are automatically made in response to the hydrogen levels measured.

Last I heard, the plant was looking to resolve their installation problems and expand their chemical production capacity. It would make sense to tidy up the loose components and mount them on a common base plate with an upgraded tubing layout. Sourcing more reliable components may also be necessary.

Despite the questionable installation, we were glad to hear that the hydrogen analyzer was performing satisfactorily. If you have a requirement for H2 measurement in challenging applications, we can likely offer a solution for you too. Hydrogen page on Nova website.

Episode 1 - old portable flue gas with dual CO channel
Episode 2 - portable ppm H2 analyzer for university metallurgical lab

1-800-295-3771

sales at nova-gas dot com

websales at nova-gas dot com

http://www.nova-gas.com/
https://twitter.com/NOVAGAS
http://www.linkedin.com/company/nova-analytical-systems-inc-
http://www.tenovagroup.com/

Vortex tube graphic modified from:

http://en.wikipedia.org/wiki/Vortex_tube

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#164 - PPM O2 Analysis – Part 1

We have had quite a few inquiries lately about oxygen analysis in the parts-per-million (PPM) scale.

The ambient air we breathe has 20.95% oxygen (O2) in it. This proportion of O2 is suitable for sustaining many forms of life and biological processes on this planet. However, some processes require atmospheres of low O2 or even trace O2. When verifying the purity of a produced gas, instead of measuring the target gas, it is sometimes best to measure the impurities. If the impurity is known to be O2, measuring the O2 will make good sense. Instead of being stated as a percent (%) O2, some very low O2 atmospheres are stated in parts-per-million (PPM).

Measuring ppmO2 can be a challenge for several reasons:

• PPM measurements require a suitable degree of accuracy and
  precision to be meaningful.
• Not all O2 measurement technologies are sensitive enough to
  function at low ppmO2 levels.
• Ambient O2 is ubiquitous and is difficult to exclude.

In our experience, the electrochemical sensor is most commonly requested by our customers for ppmO2 measurement. In Nova’s product line, this methodology can be used for any range from 0-100 PPM to 0-19,999 PPM O2. The electrochemical sensor provides good sensitivity, accuracy, and speed of response to O2 levels in these ranges.

One disadvantage of electrochemical ppmO2 sensors is their sensitivity to high levels of O2. If a sensor is set up for a range of 0-1,000ppm and it is exposed to ambient air, it will be ‘blinded’ temporarily. The effect is similar to stepping out into bright sunlight after spending time in a low-light environment. An electrochemical sensor may have long recovery time after the exposure for a couple of reasons:

• Chemical recovery of the sensor and removal of high O2
  from the cell’s diffusion layer.
• Purging the excess O2 from the internal sample tubing
  and related components.

Therefore, it is important to avoid exposing the sensor to ambient air. This may not be too difficult with a continuous analyzer that is permanently connected to a low O2 environment. However, a portable analyzer may not have this advantage.

In these analyzers, we internally protect the O2 sensors by purging out the ambient air out before exposing the sensors to the sample. When finished analyzing, we trap the last ppmO2 sample in the sensor before decoupling the analyzer from the process. We do both of these operations by using PURGE / SAMPLE switch on the front panel.

Before the analyzer is exposed to the sample gas,
the switch on analyzer is moved to the PURGE position.
Running the analyzer in this mode allows some time
for the ambient air to purge out of the sample tubing.
After the purge time, the switch can be moved over to SAMPLE.

The Model 325 is designed for ppmO2 analysis. If a system like this is of interest to you, contact Nova for details.

1-800-295-3771

sales at nova-gas dot com

websales at nova-gas dot com

http://www.nova-gas.com/

https://twitter.com/NOVAGAS

http://www.linkedin.com/company/nova-analytical-systems-inc-

http://www.tenovagroup.com/

#163 - Explosion Atmosphere Analysis Application

The recent mining deaths in Colorado USA involved two miners who died of carbon monoxide poisoning after they entered an area of the mine where an explosive had previously been detonated. (link)

We usually think only of the dynamic physical effects caused by explosions. However, explosions can also create gas emissions that have some resemblance to combustion atmospheres.

A couple years ago, we were approached by Queen’s University located in Kingston, Ontario, Canada to assist with atmosphere analysis in mining research.

They were detonating an explosive charge in a chamber approximately 14m3 (500ft3). The produced atmosphere was pumped to a monitoring station about 10-20m away.

The atmosphere developed in the chamber was no doubt a product of the following constituents:

- the products of heat and combustion

- the prevailing atmosphere prior to the explosion; e.g. O2 content

- the chemistry of the explosive

The gas analysis required was:

0 – 25% O2

0 – 2,000ppm CO

0 – 20,000ppm CO2

0 – 800ppm NO2

0 – 800ppm NO

The CO / CO2 were done by infrared detectors. The other gases were done by electrochemical sensors.

It is understandable that an explosion event can be very dusty. In this case, the explosion atmosphere was contained inside a chamber and the intention was to analyze the gases soon after detonation. To enable this, a remote probe & heated filter was supplied. After the explosion, the probe / filter assembly would be mated to the chamber via a set of bolted flanges similar to the graphic below.

Another option would have been to permanently mount the probe onto the chamber and install a heavy manual valve in the pipe between them. After the explosion, the valve could be opened and analysis begun.

During or after analysis, a supply of instrument air or N2 could be connected to the filter assembly enable a blow-back function which sends a blast of high pressure air/N2 back through the probe and filter to push any accumulated dust back out into the chamber.

Connected to the filter system was the analyzer which had a built-in pump. The pump pulls a gas sample through the probe and filters and into the detectors for analysis. If the sample tubing between the chamber and the analyzer runs outdoors in cold weather, the tubing will require some form of freeze-protection. This will ensure that any condensation will not freeze up and block flow.

Besides the gases listed above, it was expected that up to 1000ppm NH3 would develop in the chamber. The analyzer was therefore designed with NH3-resistant components to prevent corrosion. Up to 5000ppm CH4 was also expected, but this was not a corrosion concern. We were able to propose a ppmCH4 detector. However, this did not end up being needed.

If a system like this is of interest to you, contact Nova for details.

1-800-295-3771

sales at nova-gas dot com

websales at nova-gas dot com

http://www.nova-gas.com/

https://twitter.com/NOVAGAS

http://www.linkedin.com/company/nova-analytical-systems-inc-

http://www.tenovagroup.com/

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#162 - Solar Field with Capability to Generate at Night

From the http://phys.org/ website:

http://phys.org/news/2013-10-arizona-solar-hours-sun.html

Interesting article about Abengoa's Solana solar plant in the desert near Gila Bend, Arizona. This facility covers 7.8 sq km / 3 sq miles, with the majority of the area taken up by rows of parabolic mirrors. The mirrors focus and concentrate sunlight onto a pipe that contains a heat transfer fluid. The heated fluid travels to boilers where the heat is exchanged with water, creating steam. The steam drives 140-megawatt turbines to produce electricity.

The heated fluid process is really is a thermal storage system that allows the plant to continue generating electricity at full output for approximately 6 hours even after the sun goes down. This addresses some of the intermittency issue, which is an often-cited disadvantage of solar power. The additional 6 hours of power generation allows the plant to meet the peak electricity demands of evening and early night-time.

Pictures © 2013 copyright Ed Gunther

http://guntherportfolio.com/2013/01/abengoa-solar-solana-generating-station-sortie/

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