Christian Markussen, FLSmidth, Denmark, outlines the challenges posed by an acid-damaged gas analysis system at Cementos Lemona and how these were overcome by a new approach to difficult conditions.
Like any cement plant, Cementos Lemona wanted to be able to accurately monitor their process. But their gas analysis probe kept clogging, resulting in continuous maintenance and downtime.
It’s a common problem. The high-temperature, dust-laden kiln environment is hard on gas analysis probes. It’s not a question of if they’ll clog, but when. And while they’re being cleaned, the gas analysis system is effectively useless. No monitoring. No data. No possibility to keep a watchful eye on the process.
Pipe dream becomes reality
After living with these problems for years, Cementos Lemona took the decision to upgrade to a new gas analysis system from FLSmidth with patented KilnLoq probe.
We were recommended the KilnLoq probe by other plants in the CRH Group. It has the reputation of being the most robust probe on the market.
The KilnLoq probe has earned this reputation by reducing maintenance to the absolute minimum. As a one-pipe design with no bends or filters in the path to trap dust, the probe stays cleaner for longer – and when it does come time to clean it, it’s a matter of minutes, not hours.
Cementos Lemona's new gas analysis system incorporated:
- The KilnLoq one pipe probe system mounted in the automatic Extraction Device
- A probe water cooling system - necessary due to the high temperature in the kiln inlet
- An air tank, used for the probe-cleaning, which uses a similar technique to an air cannon design
- An analyser cabinet containing analyser equipment as well as the control of the complete system
The KilnLoq probe
A one pipe probe system mounted in the automatic Extraction Device
Containing analyser equipment as well as the control of the complete system
Probe water cooling system
Necessary due to the high temperature in the kiln inlet
Used for the probe-cleaning, which uses a similar technique to an air cannon design
The new system completely eradicated the probe problems Cementos Lemona had been experiencing – and enabled the gas analysis system to do its job. The precise and reliable measurements resulted in much better fuel regulation, which led to savings in fuel costs.
Unfortunately, that was not the end of the story. The clogged probe had been masking other issues in the system. With the probe blockages resolved, these other problems came to light. The service team experienced gas analysis failures, unreliable O2 measurements, low gas flow issues and more. The cause? Acid formation in the gas conditioning system.
Acid forms, gas analysers suffer
Acid formation is a common problem for plants dealing with high levels of sulphur in their fuels or raw materials – as is the case for Cementos Lemona. Alternative fuels such as tyres can send sulphur levels rocketing, putting gas analysers in danger.
Sulphur dioxide can react with oxygen to create sulphur trioxide. Add H2O to the mix and you’re left with highly corrosive sulfuric acid that will cause severe and extensive damage to your gas analyser chamber. Exactly the scenario that Cementos Lemona was dealing with.
The impact on Cementos Lemona was severe. Many hours were spent on calibrating and maintaining the system and the costs mounted. Meanwhile, without a working gas analysis system, they were running the kiln blind. How could they optimise their process and keep a handle on their emissions levels without a working analyser? They had to invest in a second analyser to enable continuous measurement through the downtime. Another expense – and not much of a solution. They needed an analyser that could cope with their process conditions.
Why do gas analysis systems suffer acid formation?
While the coolers used in conventional cold/dry gas analysis systems lower H2O concentrations in the gas-phase, they still allow for acid formation that can cause serious damage in the analyser measurement chamber. Cold/dry systems operate at temperatures around 5˚C – a danger zone for acid formation. The acid concentration depends on four things:
- The SO2 concentration
- The SO2 to SO3 conversion rate
- The concentration of water
- The concentration of NO2 in the process
As a gas, the acid compounds are not particularly corrosive. However, when the temperature of the gas drops below the acid gas dewpoint, an acid mist can form, which can either turn into a fine aerosol, or it can condense on a cold surface. Either way, the potential for damage to the gas analyser system is severe.
How to solve the acid problem?
It’s impossible to eliminate water from this type of gas analysis system, even with a low-temperature cooler. But it is possible to raise the temperature above the sulfuric acid dewpoint, so that the gas being measured is both hot and wet. This is what FLSmidth’s new KilnLoq HW Laser System does – and this is the solution we proposed to Cementos Lemona.
The KilnLoq HW Laser System uses Rosemount’s QCL/TDL technology with patented laser chirp technique to expand gas analysis to both the near and mid-infrared range, enabling enhanced process insight, improved overall gas analysis sensitivity and selectivity, eliminating cross interference and increasing response time. CO, NO, SO2, CO2 and O2 can all be measured precisely in less than a microsecond. It delivers increased accuracy and efficiency, while removing the acid corrosion problem – for good. Because the temperature of all parts of the system is kept above the acid dew point, we can wave goodbye to expensive maintenance and say adios to lengthy equipment downtime.
Cementos Lemona was excited by the potential savings this technology could offer. In June 2017, a test installation of the KilnLoq HW Laser System was supplied by FLSmidth Gas Analysis Technology in Denmark and commissioned in cooperation with a gas analysis specialist from our office in Madrid.
The end of ‘tedious’ downtime
The benefits were immediate and remarkable. No more acid damage. No more extensive downtime for repairs. Continuous and reliable measurements of O2, NO, CO and SO2 restored the plant operators’ trust in the measuring results. And of course, the data generated enables the process to continue effectively, efficiently and with minimal environmental impact.
With the reduction in man-hours spent maintaining and recalibrating the gas analysis system, Cementos Lemona expects to see a swift return on investment.
The implementation of the KilnLoq HW Laser System delivered immediate benefits. We avoided the long downtimes caused by acid-damaged gas analysers and achieved both a significant reduction of maintenance and the money spent on analyser repairs.
In fact, Cementos Lemona has worked out that it will save a total of 1435 man-hours over 5 years thanks to the new gas analysis system.
“Upgrading to the KilnLoq probe eliminated our tedious and time-consuming probe clogging problems,” says Iñigo San-José Ortiz. “And with the hot/wet laser-based analyser, we also gained more stable and reliable measurements and thus much more precise fuel regulation, which provided fuel cost savings.”
We experienced a successful implementation of the KilnLoq HW Laser System. We have had a good cooperation with FLSmidth and are now fully satisfied with our gas analysis solution.