23 Inline and Online Process Analytical Technology with an Outlook …
575
The penetration depth of the light can be modeled with the radiative transfer
equation. A detailed overview of the axial and radial scattering of photons is given
in [52, 53]. Some more practical applications are described in [1, 55–60].
23.5.3 Robustness of the Inline Measurement Setup
for Solids: Diffuse Illumination
Robustness of the optical setup is a key issue for successful implementation of PAT
into industrial processes. The strongest “enemy” for reliable measurements of solids
and surfaces is specular reflection which accounts for many perturbations. A high
effort is needed especially with objects which are complex in shape like, e.g., capsules
in the pharmaceutical industry, or natural variable surfaces which are found in apples,
tomatoes (see Fig. 23.11) and other fruits. In hyperspectral, imaging often shades are
measured and need to be excluded, e.g., by chemometric data pre-treatment which
on the other side may reduce the robustness of the model [1, 40].
Ideally, the sample is illuminated by a perfect Lambertian source and the detector
is also integrated into an integrating sphere. A good approximation to a Lambertian
illumination can be realized in PAT as shown in Fig. 23.11. Two practical examples of
an illumination setup are shown which are cheap, robust, and efficient. As material,
industrially produced Teflon can be used as long as the material is easy to clean
and is stable within its industrial environment. The samples with these arrangements
are almost ideally and homogeneously illuminated and no shadow on the surface or
on the background material is present. Furthermore, diffuse illuminated samples are
very tolerant towards flutter in industrial assembly lines [13, 60, 61].
23.6 PAT in the Petrochemical Industry as an Example
for Inline Process Control
23.6.1 Petrochemical Industry
23.6.1.1 Product Portfolio
The petrochemical industry is a branch of industry that produces organic intermediates such as refined products, natural gas, plastics, rubber, fiber raw materials, and
many other basic chemicals using unit operations to separate and functionalize the
products [62].
Natural gas processing, for example, is a complex industrial process for purifying
raw natural gas, in which impurities such as various non-methane hydrocarbons and
liquids are separated to produce dry natural gas in so-called pipeline quality. The
inline analysis of natural gas consists primarily of methane, but also includes various
575
The penetration depth of the light can be modeled with the radiative transfer
equation. A detailed overview of the axial and radial scattering of photons is given
in [52, 53]. Some more practical applications are described in [1, 55–60].
23.5.3 Robustness of the Inline Measurement Setup
for Solids: Diffuse Illumination
Robustness of the optical setup is a key issue for successful implementation of PAT
into industrial processes. The strongest “enemy” for reliable measurements of solids
and surfaces is specular reflection which accounts for many perturbations. A high
effort is needed especially with objects which are complex in shape like, e.g., capsules
in the pharmaceutical industry, or natural variable surfaces which are found in apples,
tomatoes (see Fig. 23.11) and other fruits. In hyperspectral, imaging often shades are
measured and need to be excluded, e.g., by chemometric data pre-treatment which
on the other side may reduce the robustness of the model [1, 40].
Ideally, the sample is illuminated by a perfect Lambertian source and the detector
is also integrated into an integrating sphere. A good approximation to a Lambertian
illumination can be realized in PAT as shown in Fig. 23.11. Two practical examples of
an illumination setup are shown which are cheap, robust, and efficient. As material,
industrially produced Teflon can be used as long as the material is easy to clean
and is stable within its industrial environment. The samples with these arrangements
are almost ideally and homogeneously illuminated and no shadow on the surface or
on the background material is present. Furthermore, diffuse illuminated samples are
very tolerant towards flutter in industrial assembly lines [13, 60, 61].
23.6 PAT in the Petrochemical Industry as an Example
for Inline Process Control
23.6.1 Petrochemical Industry
23.6.1.1 Product Portfolio
The petrochemical industry is a branch of industry that produces organic intermediates such as refined products, natural gas, plastics, rubber, fiber raw materials, and
many other basic chemicals using unit operations to separate and functionalize the
products [62].
Natural gas processing, for example, is a complex industrial process for purifying
raw natural gas, in which impurities such as various non-methane hydrocarbons and
liquids are separated to produce dry natural gas in so-called pipeline quality. The
inline analysis of natural gas consists primarily of methane, but also includes various