Model discrimination for reactions with stop-effect

Several basic models presented in the literature for reactions with a stop-effect yield virtually the same results under steady state conditions. Such a situation takes place for dehydration of alcohols and the deamination of primary amines. It has been proved that a simple transient behaviour after a stop in the supply of the reactant will not make it possible to distinguish between the models. However, a considerable difference in the mean reaction mte under forced concentration oscillations between the models can be observed. The difference decreases with an increase in the cycling time

Process and equipment design optimising product properties and attributes

Classically, when products have been developed at the bench, process engineers will search for equipment to manufacture the product at large scale. More than often, this search is constraint to the existing equipment base, or a catalog search for standard equipment. It is then not surprising, that the product manufactured at large scale, either deviates significantly from the intended product, and/or the incurred costs to manufacture the product are much higher than anticipated because the equipment has not been designed for this product, or product range. This paper describes the combined design of an extruder equipment and the operating conditions to process ice cream with desired product attributes

Determination of the thermal conductivity coefficient of nanofluids using analytical dependencies

W pracy dokonano przeglądu literaturowego istniejących formuł analitycznych dla określenia przewodnictwa cieplnego nanopłynów. Stwierdzono, że pomimo znacznego wysiłku nie udało się uzyskać wzorów ogólnych o zadowalającej dokładności. Uzyskano natomiast szereg wzorów godnych zalecenia dla konkretnych przypadków szczególnych. Słowa kluczowe: współczynnik przewodzenia ciepła, metody obliczeniowe, nanopłynyThe paper presents literature survey on analytical prediction of effective thermal conductivity of nanofluids. It was found that regardless big efforts a general formula of sufficient accuracy was not obtained. However, a number of trusted in specific cases equations were obtained

Modelling and experimental validation of emulsification process in continuous rotor-stator units

Despite the wide range of industrial applications of structured emulsions, current approaches towards process design and scale-up are commonly based on trial-and-error experimentation. As this design approach is foreseen to deliver most likely suboptimal process solutions, we propose in this contribution a model-based approach as the way forward to designing manufacturing processes of structured emulsions. In this context, process modelling and simulation techniques are applied to predict production rates and equipment sizing. Moreover, sensitivity analysis of the process model provides insight about potential bottlenecks in the process

Product driven process synthesis methodology

In the last ten years much more processes are being reported to be desinged through a process synthesis approach. It has been recognised during those years that (i) processes for structured products are much more difficult to design through process synthesis; (ii) processs synthesis is disconnected from product development. In a response to these shortfalls a number of authors have described that these gaps need to be filled, however no methodology extension has been proposed. In this work, we will present extensions to the conceptual process synthesis methodology to include the (structured) product design. The whole design methodology spans from how the new product can enlight the consumer, financial and supply chain boundary conditions, through to an optimal flowsheet able to produce the desired product cost effectively

Factory operations modelling methodology applied to a case study

Most of Unilever’s food processes consist of a large number of ingredients with limited storage capacity, a small number of process plants, a large number of intermediate product storage facilities and a smaller number of packing lines. The practical production scheduling inside the vast majority of these factories focusses on scheduling the packing lines on the production floor. The schedule is ‘thrown over the wall’ to the process department, in which a schedule is being made to satisfy the packing demand. This schedule is also "thrown over the wall" to the incoming materials department, etc. This way of scheduling poses three problems: 1. There is no clear insight in where the bottlenecks in the whole process are, resulting in a reduced production capacity. 2. Any change in the packing schedule might lead to an infeasible schedule in the upstream departments. As a result, packing lines may not run due to lack of intermediate products, wrong intermediates being made in the process plant, etc. 3. Each department will strive to ensure that their department is not to blame for not packing products, hence less available capacity will be communicated to the plant. The challenge is to reduce the impact of these problems in order to increase the capacity of the factory and reduce the product cost/tonnes. Problem This paper describes a methodology is to reduce the impact of these problems by modelling the factory operations. This is done by building a multi-stage scheduling model which describes the infra-structure of the factory, which products are being produced and how the plant is operated. The key challenge is to translate the complexity of the plant (and the operations) into a simplified, but realistic, multi-stage scheduling model. This model of the whole factory, including the constraints, is used to schedule the whole plant, maximising the production capacity and minimising the impact of the above described problems. Main results This paper describes a methodology to translate the complexity of the plant into a simplified model that can be used to schedule all relevant plant operations. The methodology consists of six steps: 1. Based the process flow diagrams, interviews and standard operating procedures a factory structure model is built. 2. Including the bill of materials and product routing a material flow structure is built. 3. Combining the above structures and taking into account the change-over structure the factory model is built. 4. This factory model is used to specify which data is to be retrieved from the existing factory systems into the data model. 5. The simulation model is implemented by combining the factory model, data model and the operational inputs. 6. The model is firstly verified with the operators in the plant, followed by validation by running the plant by the model. Conclusions & recommendations The above methodology was applied to an ice-cream factory. The resulting model was validated and shown to describe the plant with sufficient accuracy. Operational use of the model proved a production capacity increase of 10 – 30

nanofluids with Al2O3 particles

W pracy przedstawiono formułę do obliczania efektywnego współczynnika przewodzenia ciepła nanopłynów zawierających cząstki A1203 możliwą do wykorzystania przy obliczeniach numerycznych. Zaproponowano również metodę postępowania dla przypadku, gdy wyniki estymacji prowadzą do rezultatu niezgodnego z fizyką procesu.A dependence for numerical calculations of effective thermal conductivity coefficient of nanofluids containing A1203 particles is presented in the paper. A procedure in case when the estimation leads to results inconsistent with physics of the process is also proposed

Coal sludge dewatering using periodical centrifugal filtration

W jednej z kopalń węgla kamiennego odwadnianie zawiesiny z wirówek sedymentacyjno-sitowych polega na podawaniu odsączu do odmulnika DORR'a, skąd szlam kierowany jest na prasy filtracyjne typu PF - ROW, a proces filtracji prowadzony jest przy ciśnieniu roboczym 6 bar. W wyniku odwadniania uzyskuje się osad o wilgotności 36÷37%. Dane technologiczne przewidują, że zagęszczony wylew z odmulnika DORR'a zawiera 250÷300 g/dm3 ciała stałego, a przelew zawracany do obiegu zawiera 2÷4 g/dm3 ciała stałego, będącego wg danych [1] w ok. 81,5% węglem, a więc ciało stałe stanowi cenny surowiec energetyczny. Problemem technicznym znanych technik odwadniania takich szlamów jest ich drobne uziarnienie, dlatego rozważono zmianę sposobu odwadniania na periodyczną filtrację wirową, a ideą badań było stwierdzenie, czy w czasie takiej filtracji uzyskuje się zbliżone wilgotności końcowe osadów. Potwierdzenie takiej tezy dla periodycznej filtracji wirowej mogłoby stanowić asumpt do zmiany technologii odwadniania w kierunku filtracji wirowej ciągłej, dla której wprawdzie koszty inwestycyjne takich wirówek są bardzo wysokie, ale zdecydowanie mniejsze są koszty robocizny. Oczywiście o ewentualnym wyborze sposobu odwadniania musiałby decydować rachunek ekonomiczny.Results of experiments dealing with laboratory-scale periodical centrifugal filtration of sludge originated from one of coal mines, currently dewatering in filtration press, is presented in the paper. This sludge is characterized by a quite high, i.e. greater than 20% mass concentration of solid phase being the coal in 81.3%. Because a final moisture content in the sediment is approximately equal to 37% at pressure of 6 bars, a question appears, if using the centrifugal filtration for simplex a/ g = 1000 (usually applied in industrial conditions) and the centrifugation time close to 10 min, a lower final moisture content of sedimentcan be achieved? It was stated that for such conditions, the final moisture content was equal to about 0.418, what was much higher than after presses. Researches on centrifugal filtration were conducted in a relatively broad range of a/g = 174.5-.;-1786.8 and 't =4-.;-30 min. It was proved that the influence of a/g on the final moisture content was stronger than 't. For the highest a/ g and 't used in the experiments, values of w = 36.6% (for the supply 2) and w = 37.2% (for the supply 1) were obtained. The data for sludge presented in this work indicate that the increase of solid phase mass concentration in the suspension influences the decrease the final moisture content of sediment, and this conclusion is a result of comparison of the data taken from works [26] and [27], obtained for a few and over 20% solid phase concentration in suspension. Quite high values of moisture content in sediments indicate the difficulties in mechanical phase separation. This was also proved by additional measurements, including particle size distribution and sedimentation tests. It was stated that particle size distribution was very fine (Jlm) and critical sedimentation time - long (ca. 120 hr.). This means that the initial suspension thickening using sedimentation is unnecessary. One of the conclusion derived from the researches leads to the statement that periodical or continuous centrifugal filtration is useless because of wet sediments obtained. It is also worth to mention that filtration tests were carried out for previously selected filtration cloth of the type PT - 912 and suspension tested could be treated as without addition of flocculant

Change of filtration properties of coal flotoconcentrate subjected to the centrifugal filtration after flocculant sonication

Vacuum filtration is widely used in dehydration of the coal flotoconcentrate. Inspite of the application of flocculants, it gives post-filtration suspension humidity of ca. 27-28%. Suspension humidity may be significantly decreased as a result of the centrifugal filtration. Investigated flotoconcentrate suspension contained ca. 31% of solids and its density was ca. 1087 [kg/m3]. Flocculant Magnafloc 336 was added to the suspension in a proportion 70 g/l Mg of dry product. During the simultaneously performed investigation on vacuum filtration ([4]) it was shown that applied dosage is too small. Therefore, an additional flocculant portion of 40 g/l Mg of dry product is advisable. It enables one to obtain a product of less humidity. It was also stated that, in comparison to a nonsonicated flocculant, a treatment of the additional dosage by an ultrasound field of 20 [kHz] for 6 [s] results in an additional effect of dehydration. Investigations of the centrifugal filtration were carried out for the following parameters of a laboratory centrifuge: tau = 5-30 min, a/g = 251.3-1969.9. Investigation series for given suspension (without additional flocculant, addition of 40 g/l Mg and sonicated addition of 40 g/l Mg) included 7 centrifugation times and 6 values of the multiplication coefficient. It means 42 measurement points. All examinations were carried out for the same filtration cloth PT-912. Empirical triparametric correlations w(pl) = f (a/g,tau) were developed. The value of R-2 of the correlation is not lower than 0.9443 for investigated suspensions. Moreover, particle size distribution as well as sedimentation tests of examined suspensions were performed. It was stated that although addition of the extra flocculant dosage causes the decrease of humidity of the filtration cake significantly as a result of centrigugal filtration, the sonication of the flocculant was beneficial for final dehydration, however the changes were less noticable. For the most important working parameters of the centrifuge, i.e. a/g = 1970 and tau = 1800 s, for sonicated flocculant Magnafloc addition w(pl) approximate to 16.5% was obtained. Physical explanation of the flocculant sonication effect is a formation of smaller but more stable aggregates and the considerably lower amount of micrograins in comparison to a technological suspension. This suggestion is confirmed not only by sedimentation tests and grain analyses, but also by other coal flotoconcentrate investigations published in [7, 10], considering an influence of the flocculate sonication on w(pl) during the pressure filtration