The disposal of whey, the by-product of cheese or casein production, represents serious environmental problems. On the contrary, recovery of whey components or use of whey as fermentation medium may be advantageous not only for the environment but also for a sustainable economy. In this study we investigate the possibilities for whey fermentation with kefir grains. Firstly, optimal cultivation conditions were determined, afterwards construction of a mathematical model that describes the dynamic process of whey fermentation with kefir grains was developed. The attention was placed on maximum biomass increase, and not on the quality of the resulting kefir-like drink. Kinetic parameters were estimated and adjusted using a non-linear regression technique in order to fit with the experimental data. All experiments were performed in a laboratory batch bioreactor with whey from a commercial dairy plant. The gravimetric method was used to determine daily kefir grain increases under selected operating conditions (temperature, rotational frequency of the stirrer, and initial kefir grain mass concentration). Maximum specific growth rates of cells in whey and milk were compared. It was found that kefir grain increase was nearly the same in whey and in milk. From the obtained results, it is obvious that whey as dairy industry waste, could be effectively used in fermentation processes to obtain value added products. The estimated kinetic parameters could be used to bioreactor design.

The production of powder materials from melts is usually done by atomisation. In our research two different frits were successfully produced using water atomisation technique. An overall assessment of the powders showed that the sizes of particles and their morphologies are determined mainly by the chemical compositions of the frits and atomisation parameters. The sizes of the particles depend on the viscosities of the frits, which is governed by the melt superheating during the experimental trials, orifice diameter and interactions between droplets and particles during additional stages after primary atomisation, which were controlled by water pressure. The morphologies of the particles depend on the relationships between the times of solidification and sphereoidisation and on the interactions between the particles.

Enamel fit melting kinetics are investigated. A two-component reaction system consisting of borax pentahydrate (Na2B4O7 center dot 5H(2)O) and quartz (SiO2) was used as a case study. The response to the melt composition was followed, as well as its specific mechanical characteristics regarding rising temperatures. For predefined heating rate regimes melt samples were taken from the smelter at pre-defined times and the amount of B2O3 formed was analytically determined. The melting behaviour was followed using a heating microscope, whilst a dilatometer was used for defining the linear thermal expansion coefficient profile. Besides determination of the basic kinetic parameters, a mathematical equation was developed for predicting any linear thermal expansion changes as a function of the reaction temperature and time variations. The reaction proved to be elementary, with an overall fourth order. The average reaction rate constant was 8.9x10(-6) (L/mol)(3)min(-1) and this is valid within the investigated temperature interval. The melting process could not be performed at a constant temperature, thus the activation energy and pre-exponential factor were not estimated. The mathematical model for predicting thermal expansion showed very good agreement between the test and the model-based results.

The main objective of this study was to develop overall kinetic model of sodium benzoate synthesis, from ethyl benzoate and sodium hydroxide. For this purpose a series of experiments were performed in an automated RCl reactor system (Mettler Toledo). The ethyl benzoate and sodium benzoate molar concentration profiles were indirectly real-time monitored using FTIR based ReactIR (TM) iC10 analysis system, (Mettler Toledo). The heterogeneous reaction mixture was initially homogenized. The proposed second order kinetic model gives very good prediction of the experimental data. Obtained results are in agreement with previously published data.

This paper describes an experimental determination of the biodegradation rate for tannins present in industrial wastewater, after the extraction of chestnut chips. Experiments were performed in a laboratory aerobic reactor (Armfield) by using biomass from an existing industrial wastewater treatment plant. The outlet tannins concentration was determined under various processing conditions. Simultaneously, an optical microscope was used to monitor the mix of microbiological cultures in the biomass. On the basis of data obtained in experiments, non-linear regression was used to perform parametric analysis of various kinetic models, which took into account inhibition, as quoted in literature (Haldane, Edwards, Aiba, Luong). The statistical analysis, based on the P-criterion, F-criterion, adjusted coefficient of determination, Kolmogorov-Smimov test and root mean squared error, showed that the biodegradation of plant tannins in industrial wastewater under selected conditions for aerobic digestion, can be most successfully described statistically by the Aiba's kinetic model.

Site expansions or changes in production capacities are usually related with changes of utilities demands and/or utility system design. Despite several available and well established techniques for process synthesis and integration, very often, changes in process designs are made on the basis of intuition and experiences of engineers. In this paper possibilities of rational energy consumption and energy integration in an existing site for production of specialty chemicals were studied. On the basis of real process parameters and computer simulation results energy integration was re-examined. Total site analysis using modified Site Sink Source Profiles, which gives a profound insight into the site utility system configuration, heating-cooling demands and cogeneration design was performed. The existing site was found to be very well designed. With only few modifications additional 9% of hot utilities and 5% of cold utilities savings are possible.

Crystallization has become one of the most important unit operation in the chemical industries. The need to reduce the time from product discovery to market introduction is an inherent concern. In order to achieve the prescribed product quality characteristics, the process of engineering experimentation has to be optimized. Therefore, an experimental design method for crystallization processes is presented in this paper. Initially, the standardized Taguchi method was used to plan a minimum number of experiments. After identifying the working levels of the design factors and the main performance characteristics of the product under study, the method can be successfully applied to the crystallization processes. The simultaneous variations of the main crystallization parameters and their interactions were investigated using orthogonal array technique. A statistical analysis of 'signal-to-noise' ratio was followed by performing a variance analysis. After developing some special criteria, which depend on performance objectives, the optimal levels of the design factors were determined.Crystallization of KNO3 with desirable particle size as a performance characteristic was used to illustrate the design procedure. The effects of rotational frequency of the stirrer, linear cooling rate and added admixture on final particle size were studied. In order to keep the selected parameters constant during the experiment and to ensure reproduction of entire experiment the automated reaction calorimeter RC1 was used.

Cogeneration consists of combined production of electricity and heat using fuel which allows remarkable energy savings in comparison with a system producing electricity and heat separately. The possibilities for integrating a cogeneration system with chemical processes has been studied in this paper. Improvement in the systems where high temperature process streams exist can be achieved by direct integration of steam turbine with them. A hot reactor stream was used instead of fuel to produce electricity and steam for further process heat requirements. A thermodynamics oriented approach to identify a cogeneration plant that completely satisfies process heat and power demand is highlighted. Pinch analysis with extended grand composite curve enables rational choice of utilities. The acrylic acid process was used to illustrate the procedure proposed. Economic attractiveness based on payback time and net present worth indicated that the steam turbine based cogeneration system would yield a return period of less than 3 months, showing that the investment in cogeneration could be of interest for this plant.

The design of small specialty chemical plants is dealt with in the first part of this paper. The influence of different parameters on decision making between batch and continuous operation was taken into account. The results in the first part of the paper confirm the conclusions from the previous two papers that in the case of single-purpose equipment, the continuous plant is more profitable than the batch one for all capacities, but the batch process with multi-purpose equipment can be favoured over the continuous one when the equipment arrangement is appropriate (minimum number of process units and small size factor). In the second part of the paper, important economic factors (variable, fixed and equipment capital costs, product price) which have an influence on the net present worth of batch and continuous plants are discussed in detail. Variable costs have the greatest effect on the net present worth. Increased variable costs reduce the profitability of the batch or the continuous project. Merging of tasks makes the batch alternative more attractive at small production rates because economy of scale has a stronger effect on small size equipment. Merging can offset other disadvantages of batch processes, therefore it is cheaper to have one larger unit than many small units. The limiting capacity was determined where the batch process becomes more profitable than the continuous one. It depends on the process type and its annual costs. The manufacture of dibutylphtalate from butanol and phthalic anhydride is discussed as an additional case study.

Complex design procedures for a continuous and for a single product batch plant were compared. Production rate, process structure and energy integration which influence desision-making about continuous or batch operating mode, were considered. The final conclusion after applying economic analysis to all variants with single-purpose equipment is that a continuous plant with recycles after energy integration is more profitable than a batch one for all capacities, unless special reasons exist why reactors should be operated the batch way. An example calculation for a process which is planned to produce a specialty product with three reactions is used to compare the net present worth of continuous and discontinuous operation modes.

In this paper, the advantage of a batch plant which enabled multiple operations to be carried out in the same unit (multi-purpose equipment) was considered. The same example calculation for a process which was planned to produce a specialty chemical, as in Part I, was used to compare the net present worth of continuous and batch operation modes after including multi-purpose equipment. Batch process with multi-purpose equipment was more profitable than a batch process with single-purpose equipment and even more profitable than a continuous one for the capacities 1300 t/yr and lower in our case study. The results of energy integration are given, too.

The present paper is concerned with computer aided design of a specialty chemical product plant. Decisions about batch/continuous operation, time fraction of operation, plant capacity, amount and energy balances including energy integration are the first decisions to be met. Special criteria that could help to decide when a batch process may be favoured over a continuous one, are described. 12 months per year production is rescheduled to 3 months per year production. Design procedure with technological and economic results of different operating variants is described. Analysis of the results shows that the continuous process after energy integration is preferrable over a batch one for all capacities, unless special requirements exist for process related reasons.