Stack emission monitoring using non-dispersive infrared spectroscopy with an optimized nonlinear absorption cross interference correction algorithm

Abstract

In this paper, we present an optimized analysis algorithm for non-dispersive infrared (NDIR) to in situ monitor stack emissions. The proposed algorithm simultaneously compensates for nonlinear absorption and cross interference among different gases. We present a mathematical derivation for the measurement error caused by variations in interference coefficients when nonlinear absorption occurs. The proposed algorithm is derived from a classical one and uses interference functions to quantify cross interference. The interference functions vary proportionally with the nonlinear absorption. Thus, interference coefficients among different gases can be modeled by the interference functions whether gases are characterized by linear or nonlinear absorption. In this study, the simultaneous analysis of two components (CO₂ and CO) serves as an example for the validation of the proposed algorithm. The interference functions in this case can be obtained by least-squares fitting with third-order polynomials. Experiments show that the results of cross interference correction are improved significantly by utilizing the fitted interference functions when nonlinear absorptions occur. The dynamic measurement ranges of CO₂ and CO are improved by about a factor of 1.8 and 3.5, respectively. A commercial analyzer with high accuracy was used to validate the CO and CO₂ measurements derived from the NDIR analyzer prototype in which the new algorithm was embedded. The comparison of the two analyzers show that the prototype works well both within the linear and nonlinear ranges

Complex Dynamics Induced by Nonlinear Pollution Absorption, Pollution Emission Rate and Effectiveness of Abatement Technology in an OLG Model

“…A similar trend has been observed with other pollutants [5]. If gas concentrations are too high, then there is a nonlinear absorption [10]. Endo et al [11] found that the removal of extractable organic material causes the sorption of soot-considered as an important sorbent for organic contaminants in soils, sediments, and aerosols-to be more nonlinear and with a decreasing trend.…”

“…In the environmental economic modeling literature (e.g., [1,3,4]), m is assumed to be a constant. However, the most recent research results show that the environmental absorption capacity is not a constant, but has some nonlinear characteristics (see [5,10,11]). It is reasonable to assume that when the pollution stock level is relatively low, the environment may have a relatively high absorption capacity, while it may not be valid when the pollution accumulations become too high.…”

“…Zemel [8] pointed out that the natural decay of the pollution stock is a stochastic process. It is argued that the environment possesses nonlinear absorption capacity rather than a constant or linear one [9,10]. Canadell [9] found a decline in the efficiency of CO 2 sinks in the last 50 years and largely increased the carbon intensity.…”

Industrial SO<sub>2</sub> emission monitoring through a portable multichannel gas analyzer with an optimized retrieval algorithm

“…Selecting a relatively weaker absorption waveband for a certain gas reduces the sensitivity to this gas for all applications (Lambrecht, 2005;Gary, 2002). Sun et al (2013) proposed a new cross-interference correction technique that works well even when nonlinear absorption occurs (Sun et al, 2013). Consequently, the measurement range of a multichannel analyzer can be extended by a factor of approximately 2-4.…”

“…In this case, SO 2 concentrations within a certain linear range can be well resolved. However, the conventional interference correction introduces large uncertainty because of nonlinear absorption when the intended or interfering gases concentration lies beyond a threshold (Sun et al, 2013). In cases where the conventional correction of cross-interferences is impossible, one has to resort to other methods.…”