The market for laser absorption spectroscopy (LAS) techniques continues to mature. Such techniques, notably tunable diode laser absorption spectroscopy (TDLAS) and cavity ring down spectroscopy (CRDS), have found commercial success for monitoring trace amounts of gases in industrial applications and for environmental monitoring. The maturing of the market is evident in the recent acquisitions of two laser absorption spectroscopy companies by major process analysis instrument providers. Earlier this year, ABB announced the purchase of Los Gatos Research, a provider of Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) systems (see IBO 5/15/13). In 2011, Endress+Hauser acquired TDLAS supplier SpectraSensors (see IBO 6/30/12). This follows the acquisition of TDLAS and coulometry company Delta F by Servomex, a Spectris firm, in 2010 (see IBO 2/28/11) and Yokogawa’s purchase of TDLAS provider Analytical Specialties in 2008 (see IBO 7/15/08). IBO spoke with Endress+Hauser and Servomex about the opportunities in the laser absorption spectroscopy market and its displacement of other techniques.

LAS quantifies the amount of a species in a gaseous mixture in real time by using a laser to transmit a beam of light through the mixture and measuring the absorption of the light. Advantages compared to other trace gas analysis techniques, such as NIR spectroscopy, include greater sensitivity and speed, improved selectivity, and simple and lower cost operation. While TDLAS utilizes a multipath cell to increase the length of the optical path for increased sensitivity, CRDS employs a resonant optical cavity. OA-ICOS also employs an optical cavity, but the measurement is intensity based rather than time based, and it utilizes a different optical configuration. TDLAS operates in the mid-IR with detection limits in the ppb. CRDS and OA-ICOS operate in the UV to IR wavelength range with ppt sensitivity. Configurations of LAS systems include online, open air and portable systems.

SpectraSensors specializes in TDLAS instrumentation for natural gas, refining and petrochemical applications. The company offers extractive systems and portable systems for the analysis of moisture, carbon dioxide, hydrogen sulfide, acetylene, oxygen and ammonia, among other constituents. Founded in 2001, SpectraSensors employed around 90 people and had revenues of $30 million at the time of its acquisition. The company’s purchase by Endress+Hauser, a supplier of process solutions for liquid analysis, marked Endress+Hauser’s entry into the gas analysis market. “It has always been Endress+Hauser’s strategy to enter markets with cutting-edge technologies—as TDLAS definitely is. Additionally, we see a lot of potential for further applications of TDL technology,” said Michael Ziesemer, COO of Endress+Hauser.

Mr. Ziesemer highlighted the advantages and growing use of TDLAS in industrial applications. “TDLAS offers outstanding advantages compared to conventional technologies where a sensor is in direct contact with the sample,” he explained. “Electrochemical and capacitive probes, and quartz crystal analyzers are examples of conventional technologies being displaced by TDLAS in natural gas pipelines, for example.” A specific example of SpectraSensors’ technology use is for monitoring corrosion in natural gas pipelines due to moisture, carbon dioxide, hydrogen sulfide and oxygen. Mr. Ziesemer also commented on LAS’s overall impact on gas analysis process applications. “TDLAS is bound to replace other technologies in gas analysis. It will have a growing share in applications, especially in the oil and gas, chemical and petrochemical industries, besides other spectroscopic technologies,” he said. “In other words, TDLAS will not cover all, but a lot of applications.”

Asked about the challenges that remain for greater commercial adoption of TDLAS, he told IBO that investment is needed. “More applications have to be developed. Marketing is needed and sales channels have to be established to bring TDLAS to customers all over the world.” Endress+Hauser intends to expand the market. “Under the umbrella of the Endress+Hauser Group, SpectraSensors is set to open new business fields and to expand the product range. Endress+Hauser will safeguard sales and service of SpectraSensors’ gas analyzers in more and more countries.”

Servomex offers TDLAS instruments acquired through the purchase of Delta F, as well as TDLAS products of its own, including the SERVOTOUGH laser analyzers for in situ and extractive cross-stack measurements and gas monitoring. Delta F’s TDLAS products consist of extractive moisture analysis systems for semiconductor and process gas monitoring. “The ability of TDLAS technology to monitor a sample stream in situ means we are to offer a solution for many measurements which would previously have not been possible, while for some applications we are able to offer it as an alternative to an existing measurement technology,” explained Roger Highton, Product Business manager at Servomex.

In-situ TDLAS is well suited to the monitoring of combustion processes, according to Mr. Highton. “In combustion, the key to combustion efficiency is minimizing excessive air in the combustion chamber: a process which requires fast speed of response when monitoring the flue oxygen concentration at close to the optimum level and for the detection of carbon monoxide in the flue gas,” said Mr. Highton.” As TDLAS enables an in situ measurement location that is resistant to high temperatures and eliminates any sample system delays, this fast speed of response—less than two seconds—is ideal for the efficient and safe control of the combustion process.”

In monitoring nitrogen oxide emissions from power plants, TDLAS is advantageous for the measurement of nitrogen oxide reduction using selective catalytic reduction or selective non-catalytic reduction processes. “By monitoring for surplus of unreacted ammonia, commonly referred to as ammonia slip—a process difficult for traditional extractive techniques—a cross-duct TDLAS measurement can be made for ammonia concentration below the requisite 2 ppm,” explained Mr. Highton. “As the cross-duct installation gives an average rather than a point reading from an extractive sample, ammonia concentration levels can be measured with much greater certainty in the measurement.”

Servomex told IBO that sales of its TDLAS products are being driven by emerging markets. Key end-user markets for the company’s TDLAS systems are hydrocarbon processing and industry. The company also offers TDLAS products for power generation and automobile manufacturing. “Our development of TDLAS has been driven through our increasing understanding of the technology’s potential and by specific customer requirements,” said Mr. Highton. However, he noted the technology’s growth has mainly been the result of technology displacement. “In terms of the applications themselves, TDLAS has tended to fit a requirement within an existing application, offering either a brand new analysis solution or in presenting alternative or improvement to an existing technology,” he said. “In the majority of cases, therefore, TDLAS has enabled improvements to processes, rather than help innovate entirely new applications.”