Drying Unit Research Articles

Exposure to dust, endotoxin and airborne microorganisms in wastewater sludge thermal drying units

The objective of this study was to assess workers' exposure to bioaerosols in sludge drying units. Simultaneous collection of inhalable dust and airborne biological agents was carried out using rotating cup samplers (CIP 10, Arelco). Sixteen stationary and 30 personal measurements were performed in three drying plants, during summer and winter. Microbial content of air was characterized by high amounts of Gram-negative bacteria, endotoxin, and thermophilic actinomycetes. High differences between exposure levels were observed with regard to workplaces and tasks. Dryers and conveyors in operation were closed, and the monitoring task in the dryer room was associated with low levels of personal exposure, close to background levels. Conversely, cleaning and maintenance of the dryer and conveyors required the equipment to be opened, giving significantly higher task-based personal exposure levels. The fall of dried sludge into indoor containers resulted in high emission and spreading of dust. Mean personal exposure levels to fungi were moderate or low for all tasks. Based on the results of this study, appropriate means of operational control and personal protection are being developed and implemented on sites.

Combined solar drying unit

The results of theoretical and experimental studies of the processes of drying different fruits and vegetables are presented with a view to intensification of the processes in a combined solar drying unit.

Construction of a solar drying unit suitable for conservation of food and enhancement of food security in West Africa

Drying is a widely used technique in sub-Saharan Africa which allows food conservation, weight reduction and added value for some products. However, the technique is quite complex, making the rational concept of drying devices challenging. A rational method for the design and the construction of a fruit and vegetable solar dryer is presented. A prototype was designed and constructed at the Universite Libre de Bruxelles (Belgium) to test the concept and was found to be capable of drying more than 40 kg of fresh tomatoes in 10 h. A second prototype was constructed in Bandiagara (Mali) by both local craftsmen and students from the Universite Libre de Bruxelles, using local materials. Speed of drying and prevention of food spoilage was far superior to that of traditional solar dryers. Based on these prototypes, a dryer industry is being constructed in Bandiagara in order to increase food self-sufficiency.

A SOLAR DRYER PERFORMANCE OF ONION SLICES UNDER FAYOUM CLIMATIC CONDITIONS

A solar drying unit was developed and constructed for drying onion slices under Fayoum conditions. The drying unit consists of a solar collector, which oriented and tilted with an optimum tilt angle and attached with drying chamber. The drying experiments were carried out to examine the effect of onion slice thicknesses (3, 6 and 10 mm) and airflow rate (2.4 and 1.6 m 3 .min -1 ) on the onion slices drying rate. The obtained results indicated that the daily average total solar radiation flux incident on the tilted solar collector surface (7.32kWh.m -2 .day -1 ) was greater than that incident on the horizontal surface (6.13kWh.m -2 .day -1 ) by 19.41%. The higher air temperatures were obtained at the lower airflow rate (1.6 m 3 .min. -1 ) whereas; the amount of heat gained to the air from the solar collector was relatively higher at the higher airflow rate as compared with the lower airflow rate. Consequently the higher efficiency of the solar collector was obtained at the higher airflow rate. The solar collector with the higher airflow rate increased the overall thermal efficiency by 12.56% as compared to the lower airflow rate. The moisture content of dried onion slices was strongly affected by the onion slices thickness and the airflow rate. The final moisture content of dried onion slices ranged from (6.8% to 7.7% dry-basis) depending on the drying temperature cycle. Effect of the individual variables (airflow rate, onion slice thickness, moisture removed, and their interactions) on the drying rate was statistically analyzed. A forward step-wise regression technique was applied to arrive at a reasonable good best set of independent variables. The coefficient of determination (R 2 ) was above 0.97 when

OPTIMIZING TEMPERATURE IN MUSHROOM DRYING

ABSTRACT Mushroom slices after blanching were dried using heated air at 45, 55, 65, 75, 85 and 95C to about 5% moisture content. Organoleptic evaluation of mushroom soup and rehydrated slices, browning index indicative of color and the rehydration quality were used to establish safe temperature for drying mushroom. A hot-air drying temperature of 65C was found to produce a product of desirable quality that was also acceptable to consumers. Mushroom dried at 65C had a rehydration ratio of 2.9. PRACTICAL APPLICATIONS Thin-layer drying apparatus using heated air for drying is a technical advancement that provides a low cost drying option for communities with restricted budgets. Optimizing temperature that is safe for human consumption and acceptable to consumer is achieved significantly through this drying process, which is the ultimate purpose of producing processed foods. The study is anticipated to help small farmers of developing and under-developing countries, particularly of hilly regions, with inadequate transport facilities and far away from road connectivity to save their perishables from complete deterioration. This may also encourage small entrepreneurs to establish their drying units in regions far away from fresh markets. Systems using locally available fuels from agricultural waste or from nearby forests may be developed for heating ambient air for drying small batches. Even solar energy can be tapped in difficult terrains to accomplish the drying process.

Solar facility for drying sour milk products

A solar drying facility is developed that differs from the existing facilities in the capability for transferring the heat to the product that is being dried both by thermal conduction and by radiation and convection. The drying rate of the products in the developed facility is 20–25% higher than in the solar drying unit of the radiation-convection type, and 50–60% higher relative to solar air drying.

Caracterização, beneficiamento e reciclagem de carepas geradas em processos siderúrgicos

A necessidade de aplicarmos as diretrizes ambientais no contexto produtivo de qualquer empresa é hoje uma realidade no cenário mundial. O beneficiamento e a comercialização de resíduos, em diversos seguimentos industriais, têm levado as organizações a uma nova ideologia sobre a questão do gerenciamento desses materiais, sendo que a geração de receita, através da reciclagem, tem contribuído para a expansão dessa prática. Carepa é um co-produto oriundo da oxidação da superfície do aço, quando submetido ao gradiente térmico ou à simples ação do tempo. No ramo siderúrgico, provém, basicamente, das operações de lingotamento contínuo e laminação. Carepas são óxidos de ferro, cuja disposição, em pátios de resíduos deve ser realizada, seguindo-se as normas ambientais pertinentes, visto que podem ser classificados como resíduos perigosos (Classe I, NBR 10004:2004). Entretanto há poucos estudos no sentido de se viabilizar sua reciclagem, agregando valor ao co-produto em questão. Nesse sentido, operações unitárias de secagem, peneiramento e briquetagem foram adotadas no processamento desse material. Caracterizações físicas e químicas permitiram investigar suas propriedades e potencialidades industriais, de forma a adequar os parâmetros ambientais, econômicos e produtivos às necessidades das empresas.

Quality maintenance and economy with high-temperature paddy-drying processes

Drying processes result in some loss of product quality. Three drying systems for paddy were investigated for their effects on head-rice yield and whiteness. Fluidised-bed drying, tempering and ambient air ventilation units were the main components, but they were arranged differently in each drying system. Heat- and mass-transfer equations were applied to predict the change in moisture content for each drying system. Both the experiments and simulations indicated that the two sub-drying systems (system No. 2) with tempering and ventilation as elements of each stage yielded higher drying capacity and thermal efficiency than the single drying system (system No. 1), in which paddy was treated with the drying, tempering and ventilation units only once. The proportion of full kernels and value of the whiteness obtained from both drying systems were not significantly different. System No. 3, where grains after the first tempering were dried immediately by the second fluidised-bed dryer with no ventilation unit, produced poor head-rice yield and colour and was unacceptable for producing white rice.

Synthesis of Rice Processing Plants. II. MINLP Optimization

A systematic design approach was applied to develop the optimal process flowsheet for a rice processing plant. The optimization problem was formulated as a Mixed-Integer NonLinear Programme, MINLP, consisting of vectors of binary and continuous variables. A superstructure flowsheet comprising all serial structures of drying, cooling, and tempering units in the process was postulated. The set of optimum decision variables including the number of drying, cooling, and tempering units, temperature and relative humidity of drying air, drying time, cooling time, and tempering time were determine as the solution of the corresponding MINLP. Six objective functions were investigated as possible performance criteria: production time, number of the operating units, energy consumption, total operating cost, head rice yield, and the profit. The choice of objective function was found to have a significant effect on the optimal solution. Comparison with typical design and operating conditions, the MINLP results showed that a 22% reduction in energy consumption was possible along with a 2.4% increase in head rice yield. These savings, if applied to the world-wide rice industry, translate into more than $3 billion dollars/year increase in profit.

Synthesis of Rice Processing Plants. III. Sensitivity Analysis

An optimal process flowsheet for a rice processing plant has been developed. The optimization problem was formulated as a Mixed-Integer Nonlinear Programme, MINLP, consisting of a vector of binary and continuous variables. The set of optimum decision variables including the number of drying, cooling, and tempering units, temperature and relative humidity of drying air, drying time, cooling time, and tempering time were determined as the solution of the MINLP problem. Six objective functions were investigated as performance criteria. A sensitivity analysis of each model parameter was conducted to determine its influence on the optimal flowsheet. The MINLP approach is an efficient tool for optimization and the simplified models were adequate for use at the synthesis stage. The solution is insensitive to uncertainty in the models. However, due to the nonconvex nature of MINLPs, the solution was found to depend on the initial starting values, especially for the maximum profit flowsheet.

Synthesis of Rice Processing Plants. I. Development of Simplified Models

This article, the first of three articles on the synthesis of rice processing plants, focuses on the development of simplified mathematical models necessary for use in optimizing rice processing plants. The second concentrates on the optimal synthesis of a rice plant and the third on the sensitivity of the optimization to uncertainty in model parameters. Existing models for rice processing unit operations are not suitable for flowsheet optimization and new models need to be developed to overcome numerical difficulties that occur in optimization applications, specifically in mixed integer nonlinear programming (MINLP) applications. Simplified models of the drying, cooling, and tempering units are developed. In addition head rice yield models, used as a quality indicator, energy consumption, and economic models were also developed. Naturally, the new models exhibit some mismatch with respect to the existing models from which they were developed. However, a sensitivity analysis, presented in Part III, has shown that the optimal flowsheet structure was not sensitive to a lack of fit between the simplified and complex models. The simplified models were found adequate to be appropriate for use at the synthesis stage.

Recycling of meat and bone meal animal feed by vacuum pyrolysis.

Due to the recent bovine spongiform encephalopathy (BSE) crisis in the European beef industry, the use of animal-derived products to feed cattle is now severely restricted. Large quantities of waste animal meat and bone meal (MBM), also known as animal flour, have to be safely disposed of or transformed. One disposal option is pyrolysis. Vacuum pyrolysis of an animal flour sample has been performed in a laboratory reactor. The results obtained revealed that vacuum pyrolysis can be an attractive alternative to incineration and cement kilns. The process generated a combustible gas (15.1 wt %), a high calorific value oil (35.1 wt %), a solid residue rich in minerals (39.1 wt %), and an aqueous phase rich in organics (10.7 wt %). The gas and the aqueous phase can be used to provide heat to the vacuum pyrolysis reactor and the MBM drying unit. The oil can be used alone or mixed with petroleum products as a fuel in boilers or gas turbines. Conversion of animal waste by pyrolysis into fuels can contribute to the reduction of greenhouse gases. It is suggested to use the solid residue for agricultural soil enrichment in minerals and as a soil moisturizer.

Review of research and development work on solar dryers for grape drying

This paper mainly deals with the development trends of solar dryers used for grapes drying. Several typical installations, including traditional methods, are presented. Technical and economical results indicate that solar drying of grapes is feasible. However, the farmer’s acceptance of solar drying was still very limited. This may be due to the small capacity of the dryers and too long pay back period or to socio-cultural factors. Further research and development work should be continued in order to over rule these factors. As research and development work has made significant progress, it seems that a review of all developed solar drying units is appropriate.

Presence and control of polycyclic aromatic hydrocarbons in petroleum coke drying and calcination plants

Storage, shipment, handling, as well as drying and calcination of petroleum cokes might create serious health risks. This material should be processed and handled with care not only because of the excessive dust emissions it causes, but also because it may emit hazardous and carcinogenic volatile compounds. In this study, polycyclic aromatic hydrocarbon (PAH) emissions from a petroleum coke drying and calcination unit in Turkey were investigated. Rotary kiln exhaust gases were found to contain 10 of the 16 EPA priority PAHs. These emissions were identified and evaluated by using the Turkish regulatory limits after certain pollution control measures were implemented. For control of PAHs and other incomplete combustion products in the stack gases incinerators equipped with liquefied petroleum gas (LPG) burners were installed into the drying and calcination gas outlet ducts.

98/01705 Drying units for flotation wastes recovered from a settler: Lobanov, A. V. et al. Ugol' Ukr., 1996, (12), 32–34. (in Russian)

98/01705 Drying units for flotation wastes recovered from a settler: Lobanov, A. V. et al. Ugol' Ukr., 1996, (12), 32–34. (in Russian)

97/03501 Drying units for flotation wastes recovered from a settler

97/03501 Drying units for flotation wastes recovered from a settler

On Blowing Rough Rice from On-floor Drying and Storage Unit

On Blowing Rough Rice from On-floor Drying and Storage Unit

SMALL TISSUE DRYERS WITH HIGH CAPACITY FOR RAPID FREEZE-DRYING.

In close connection to the development of a new histochemical technique the need for a small high capacity freeze dryer greatly increased. A convenient system was devised, which allows work with several independent drying chambers simultaneously. The cooling source is a standard refrigeration plant equipped with an expansion coil in a Dewar flask from which cold liquid is distributed to the separate drying units. The specimen carrier of each unit can take about twenty tissue pieces. Even though diffusion pump, cold finger trap, and other delicate components have been avoided, drying time is quite favourable; it may be as little as five hours for pieces of standard size. Moreover, the evacuation pump is well protected against vapor. The freeze dryer is built mainly of standard components or inexpensive modifications of these.

Drying—Unit Operations Review

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDrying—Unit Operations ReviewP. Y. McCormickCite this: Ind. Eng. Chem. 1960, 52, 5, 439–440Publication Date (Print):May 1, 1960Publication History Published online1 May 2002Published inissue 1 May 1960https://doi.org/10.1021/ie50605a039RIGHTS & PERMISSIONSArticle Views145Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (328 KB) Get e-Alerts

Factorial Design of Experiments in Ceramics, l

A factorial design of experiment is one in which a variable is evaluated at all levels of all other variables. This type of experiment was applied to the unit operations in body preparation and forming by extrusion. Drying and firing unit operations were not considered, and the variance due to these operations was minimized by duplication. The variables or factors were (1) particle‐size distribution at three levels, (2) water of plasticity at two levels, (3) entrapped air at two levels, and (4) two replications. Analysis of variance was used to determine the significant effects. It was found that 95%. 0f the total variance of the drying shrinkage was accounted for by the particle‐size distribution, water of plasticity, and two interactions; 95% of the total variance of the dry modulus of rupture was accounted for by particle‐size distribution, water of plasticity, entrapped air, and two interactions; 52% of the total variance of the firing shrinkage was accounted for by the particle‐size distribution; 87% of the total variance of the fired modulus of rupture was accounted for by the particle‐size distribution, water of plasticity, entrapped air, and three interactions. Since a tunnel kiln makes it possible to control the firing operation closely and with no changes in composition, close control of the particle‐size distribution, water of plasticity, and entrapped air should make it possible to produce more uniform ware. The slope constants for the factors were also determined which show the most efficient path leading to the development of optimum conditions necessary for maximizing a desired property.