Finding the key transition states and intermediates controlling net reaction rates and selectivity

In this paper Campbell's degree of rate control is extended to introduce the concepts of degree of kinetic rate control, degree of kinetic selectivity control, degree of thermodynamic rate control and degree of thermodynamic selectivity control. It is demonstrated by applying hypothetical but realistic kinetic models of varying complexity that the new methods offers a rigorous framework to analyze the importance of kinetic and thermodynamic parameters i.e. establishing the critical parameters of the kinetic model. The methods are general and can be applied to complex reaction networks with multiple overall reactions not only in heterogeneous catalysis but for all sorts of chemical kinetic models

Evaluation of an Open-source Chemical Process Simulator Using a Plant-wide Oil and Gas Separation Plant Flowsheet Model as Basis

In this paper, a detailed evaluation of the open source process simulator DWSIM is presented. Using a previously published simulation model of an oil and gas separation plant, the results obtained with DWSIM are compared to a commercial process simulator widely used in the industry. The modelled flow scheme comprises a vast number of unit operations including separators (flash vessels), valves, splitters, mixers, compressors, heat exchangers, pumps and recycles (tear streams). The results obtained with DWSIM both for characterization of the inlet fluid as well as for a single operating state for the entire process, compare very well with the data obtained using a commercial tool. A rigorous comparison is made and generally, compared results are within 1% in deviation with a few exceptions. Further, an elaborate comparison is made for over 90 simulations with different settings where 10 independent variables are randomly varied over a wide range. Again, good agreement is found between the two tools. The results are very encouraging and provide fidelity in the use of the investigated open source process simulation tools in a professional environment

Anaerobic digestion as a tool to eliminate animal parasites and weed seeds

Anaerobic digestion of residual materials from animals and crops offers an opportunity to simultaneously produce bioenergy and plant fertilizers at single farms and in farm communities where input substrate materials and resulting digested residues are shared among member farms. A surplus benefit from this praxis may be the suppressing of propagules from harmful biological pest like animal parasites, pathogens, and weed seeds. In the BIOCONCENS project (http://www.icrofs.dk/Sider/Forskning/foejoIII_bioconcens.html) batch experiments were performed, where survival of six species of weeds and the pigs large roundworm Ascaris suum (non-embryonated eggs) was assessed under conditions similar to biogas plants managed at meso- (37°C) and thermophilic (50°C) conditions. Cattle manure was used as digestion substrate and experimental units were sampled destructively during time. Regarding survival of A. suum, the effect of thermophilic conditions was highly significant as no eggs survived more than 3 h of incubation at 50°C. Incubation at 37°C did not affect egg survival during the first 48 h and it took up to 10 days before total elimination was reached. Similarly, at 50°C complete mortality of weed seeds, irrespective of species, was reached after less than two days. At mesophilic conditions, seeds of Avena fatua, Sinapsis arvensis, Solidago Canadensis had completely lost germination ability, while Brassica napus, Fallopia convolvulus and Amzinckia micranta still maintained low levels (~1%) of germination ability after one week. Chenopodium album was the only weed species which survived one week at substantial levels (7%) although after 11 d germination ability was totally lost. In general, anaerobic digestion in biogas plants seems an efficient way (thermophilic more efficient than mesophilic) to treat organic farm wastes in a way that suppresses animal parasites and weeds so that the digestates can be applied without risking the spread of these pests

Removal Efficiencies in Full-scale Biotrickling Filters used to clean Pig House Exhaust Air

In this study, we tested the performance and perspectives of four full-scale biotrickling filters based on Leca® (Light Expanded Clay Aggregates), a mechanically stable, non-degradable filter media, known to absorb odorous compounds such as H2S and methanethiol. The four filters varied in: filter thickness, carrying media, and the presence of dust filters. Biological Leca® filters were found to be capable of reducing NH3, H2S and odour by up to 96%, 80% and 78%, respectively. Clogging was observed to occur after approximately 100 days, but the installation of a dust filter successfully eliminated this problem