Assessment of Near-Infrared (NIR) spectroscopy for segregation measurement of low content level ingredients

Abstract

Segregation in particulate systems may be caused by particle size, density and shape distributions leading to negative effects on product quality as well as the production costs. Quantifying powder segregation using a reliable and robust method is challenging, particularly for low content level ingredients. In this paper, we evaluate the application of NIR spectral analysis for detecting the extent of segregation of components in a multi-component mixture. As a model system, a typical laundry detergent formulation, comprising spray-dried powder, known as Blown Powder (BP), Tetraacetylethylenediamine (TAED) and enzyme placebo granules, is used. The effect of using different pre-processing methods on the measured component fractions is analysed. These are scatter correction using Standard Normal Variate (SNV) as well as derivative correction using first, second, Norris-Williams and Savitzky-Golay derivatives. The results from the NIR technique are compared to those obtained by image analysis. Concepts of Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) are used to evaluate the accuracy of different preprocessing methods. The second derivative of Norris-Williams method shows the best pre-processing method for the quantification of low content level enzyme placebo granules in the ternary mixture of detergent powder. Using the proposed NIR technique and the optimum pre-processing method, the segregation index of a low content level ingredient, such as enzyme placebo granules, is estimated to be 0.71 for a ternary heap of washing powders.

Tailoring particle shape for enhancing the homogeneity of powder mixtures: Experimental study and DEM modelling

“…Due to the presence of the red pigment on the surfaces of EPG, the fine white BP particles went pink in colour during the granulation process, enabling their differentiation from the rest of materials and therefore the SI determination using image processing. The conclusions drawn in this study have been further verified using NIR spectroscopy as well as DEM simulation as described in the section 3.3 [8]. The homogeneity of EPG was analysed for some of the extracted powder samples (Grid number: 2, 3, 4, 5, 6, 8, 9, 10 and 11) by means of NIR spectroscopy, showing that the SI decreased from 0.50 to 0.15 after shape modification.…”

“…Extraction of samples from the formed heap was further performed by inserting the horizontal and vertical blades into the generated pile for subsection division. The extracted sub-samples were then scanned using Near-Infrared spectroscopy for the segregation analysis (following the optimised approach presented in our previous work [8]). In fact, adopting the latter technique for the segregation analysis could be a better representation of the component homogeneity within the entire powder mixture.…”

“…11 show that when the spherical EPG are used for the process of heap formation of the ternary mixture, the granules tend to segregate more into the centre of the pile, which is due to the higher density of EPG as compared to other ingredients (push-away mechanism). Full investigation of the segregation mechanisms of the studied ternary mixture are described in our previous researches [8,9,33]. Several snapshots of the impact of the modified EP granules to the surface of BP particles at different time frames were obtained using a high-speed camera, as demonstrated in Fig.…”

“…A typical laundry detergent powder product is a complex formulation containing the surfactants, bleaching agents, and auxiliaries such as enzymes. Asachi et al [8,9] demonstrated that the minor ingredient of enzyme granules tends to segregate towards the centre of the granular pile due to its higher density as compared to other ingredients, as a result of the push-away effect. Laundry detergent powder products are consumed in daily life and their optimum quality is demanded by consumers.…”

Experimental evaluation of the effect of particle properties on the segregation of ternary powder mixtures

“…2-b)is determined, the pixels of the defined area are measured and converted to the fraction data. The step by step image processing for the measurement of the component fractions are explained elsewhere[29].The segregation index (SI) of component is then estimated according to Eq. (1).…”