Model based control of a liquid swelling constrained batch reactor subject to recipe uncertainties

This work presents the application of nonlinear model predictive control (NMPC) to a simulated industrial batch reactor subject to safety constraint due to reactor level swelling, which can occur with relatively fast dynamics. Uncertainties in the implementation of recipes in batch process operation are of significant industrial relevance. The paper describes a novel control-relevant formulation of the excessive liquid rise problem for a two-phase batch reactor subject to recipe uncertainties. The control simulations are carried out using a dedicated NMPC and optimization software toolbox Optcon which implements state of the art technologies. The open-loop optimal control problem is computed using the multipleshooting technique and the arising non-linear programming problem is solved using a sequential quadratic programming (SQP) algorithm tailored for large scale problems, based on the freeware optimization environment HQP. The fast response of the NMPC controller is guaranteed by the initial value embedding and real time iteration technologies. It is concluded that the OptCon implementation allows small sampling times and the controller is able to maintain safe and optimal operation conditions, with good control performance despite significant uncertainties in the implementation of the batch recipe

Comparison of external bulk video imaging with focused beam reflectance measurement and ultra-violet visible spectroscopy for metastable zone identification in food and pharmaceutical crystallization processes

The purpose of the paper is twofold: it describes the proof of concept of the newly introduced bulk video imaging (BVI) method and it presents the comparison with existing process analytical technologies (PAT) such as focused beam reflectance measurement (FBRM) and ultra violet/visible (UV/Vis) spectroscopy. While the latter two sample the system in small volumes closely to the probe, the BVI approach monitors the entire or large parts of the crystallizer volume. The BVI method is proposed as a complementary noninvasive PAT tool and it is shown that it is able to detect the boundaries of the metastable zone with comparable or better performance than the FBRM and UV/VIS probes

Emissions, Fate and Transport of Persistent Organic Pollutants to the Arctic in a Changing Global Climate

Climate change is expected to alter patterns of human economic activity and the associated emissions of chemicals, and also to affect the transport and fate of persistent organic pollutants (POPs). Here, we use a global-scale multimedia chemical fate model to analyze and quantify the impact of climate change on emissions and fate of POPs, and their transport to the Arctic. First, climate change effects under the SRES-A2 scenario are illustrated using case-studies for two well-characterized POPs, PCB153, and α-HCH. Then, we model the combined impact of altered emission patterns and climatic conditions on environmental concentrations of potential future-use substances with a broad range of chemical properties. Starting from base-case generic emission scenarios, we postulate changes in emission patterns that may occur in response to climate change: enhanced usage of industrial chemicals in an ice-free Arctic, and intensified application of agrochemicals due to higher crop production and poleward expansion of potential arable land. We find both increases and decreases in concentrations of POP-like chemicals in the Arctic in the climate change scenario compared to the base-case climate. During the phase of ongoing primary emissions, modeled increases in Arctic contamination are up to a factor of 2 in air and water, and are driven mostly by changes in emission patterns. After phase-out, increases are up to a factor of 2 in air and 4 in water, and are mostly attributable to changes in transport and fate of chemicals under the climate change scenario

Endoscopy based in-situ bulk video imaging of batch crystallization processes

External bulk video imaging (eBVI) of crystallization processes has proven to be a promising technique for metastable zone determination. In this contribution the endoscopy based in-situ bulk video imaging (iBVI) method is introduced. The video data is processed using the mean gray intensity method and by a digital image processing technique which aims to detect the first crystals during nucleation. The experiments have been carried out in a small scale calorimeter CRCv4, during which the compensation heater and infrared spectroscopy signals were monitored. It is concluded that monitoring the onset of the apparent nucleation, formation of particles with detectable size, using the mean gray intensity (MGI) trend delivers similar performance to the calorimetric and IR spectroscopy signal, whereas the crystal recognition method is the fastest, allowing to detect nucleation earlier. The endoscopy based nucleation monitoring technique is proposed as a complementary tool to existing process analytical technologies (PAT) since it provides an in-situ, lowcost, robust, probe-based method for metastable zone identification which can be easily integrated and automated with existing laboratory hardware and software

Comparative Assessment of the Global Fate of α- and β-Hexachlorocyclohexane before and after Phase-Out

Technical hexachlorocyclohexane (HCH) was one of the most widely used pesticides during the 20th century. Although production and use were phased-out during the 1990s, two of its major components, α- and β-HCH, are still ubiquitous in the environment. Here, we have collected and analyzed data on concentrations of α- and β-HCH in the atmosphere and oceans, including spatial and temporal trends and seasonalities. We apply a global fate and transport model to both isomers over the period 1950 to 2050 to rationalize current levels and trends at remote locations with estimated emissions and to forecast into the near future. Our model results indicate that secondary emissions from soils and oceans are currently controlling the observed rates of decline in the atmosphere. β-HCH is declining more slowly than α-HCH due to its higher persistence, and we hypothesize that it will eventually become the predominant isomer of HCH in the environment. The model reproduces over 70% of measured concentrations of α-HCH in air and ocean water within factors of 3 and 5, respectively, and over 70% of measured concentrations of β-HCH within factors of 8 and 20, respectively. The model results are only weakly sensitive to climate change-induced trends in Arctic sea-ice cover and temperature