SIMULATION OF RECIRCULATION TYPE DRYER USING PNEUMATIC CONVEYORS

Recirculating rice dryers are suitable for a large amount of loading capacity. It generally comprises two parts, the tempering section, a drying section, and the grains are dried intermittently until the final moisture content of the grains can be achieved. Wet grains are initially dried for about 11 minutes within the drying section of the dryer. The grains then are conveyed to the tempering section, stored for about 40 to 50 minutes. At every passes, about less than 2% (wb). The moisture content can be removed from the grains. The number of passes required to accomplish a drying process in a recirculation dryer depends on the initial moisture content and the amount of rough rice to be dried. The drying and tempering duration can be adjusted through a mechanical valve. The purpose of this study was to examine the performance of recirculating dryers equipped with pneumatic conveyors instead of bucket elevators to reduce electricity cost and heated using a proper blend between kerosene and jatropha oil. Several experimental runs were conducted under a constant drying temperature of 60℃ and were controlled by adjusting the fuel consumption rate. The experimental results showed that the drying efficiency was in the range of 22.2% to 31.1%, the specific energy consumption was between 3,475-4,785 MJ/kg H2O evaporated, fuel consumption at 0.95 to 1.15 liters/hr, and the drying rate was 0.9% per day. Using 465 kg of rough rice, the entire drying operation required 10 hours of drying time with 74.3% of head yield. The mathematical model used in this study also had indicated close agreement with experimental data.

PENGARUH PEMBERIAN MINUMAN KARBOHIDRAT ELEKTROLIT TERHADAP PRODUKTIVITAS KERJA PADA PEKERJA PEMBUATAN BATU BATA

Work productivity is influenced by many things, one of which depends on the availability of nutrients in the worker's body. In industrial workers, the lack of nutrient consumption that is often experienced is lack of fluids. Workers who worked in hot ambient temperatures for 10 days lost an average of 4.8 - 6 grams of sodium. However, lost body fluids cannot be replaced by simply drinking water during work. This research is a quantitative study with a quasy experimental study design with one group pretest-posttest design which aims to determine the effect of giving electrolyte carbohydrates on work productivity of brick-making workers. The population in this study were all brick-making workers in the drying section, a sample of 42 people who were taken using the total sampling technique. Data were analyzed using Paired Sample t-test with α = 0.05. The results showed that there was an effect of giving electrolyte carbohydrate drinks on the work productivity of brick making workers (p value = 0.000). Giving electrolyte carbohydrate drinks can increase energy intake and bind Na + to remain in the cells. Electrolyte carbohydrate drinks replace water and electrolytes lost through sweat during activity and replace carbohydrates used from liver and muscle reserves during activity. Therefore, the owner of the masonry factory is expected to be able to provide water and electrolyte carbohydrate drinks for workers so that workers' fluid needs are met, workers do not experience fatigue and eventually work productivity increases.

Experimental and Theoretical Study of Heat Losses in Drying Cylinders

The research purpose is to develop methods for determination of heat losses in drying cylinders. Experimental study of temperature of drying cylinders performed in the drying section of a paper machine during its steady-state operation. Medium, maximum and permissible statistical characteristics of drying cylinder temperatures were defined. The drying cylinders with increased condensation concentration were determined by the minimally permissible temperature levels and the repair of the condensation drainage system to reduce heat losses (steam consumption) was justified. The cause of uneven dryness of the paper web across the width has been determined. The condensate ring on the inner wall at the edges of the drying cylinders gets thickened due to moisture coming from the end caps from the action of centrifugal forces. The condensation is removed from the drying cylinders with a siphon on the drive side. Therefore, on the front side of the drying cylinders condensate film has a greater thickness, and the paper web dries worse. The single-sided condensate disposal and the physical effect of centrifugal condensate runoff from the end caps to the side inner surface of the drying cylinders cause a lower dryness from the front side of the paper web. The use of thermal insulation of end caps will contribute to uniform dryness across the width of the paper web. The results of experimental studies were processed by methods of mathematical statistics in order to describe the thermal losses during contact drying of the paper web on drying cylinders with and without thermal insulation of the end caps to the ambient air. The calculation of heat losses is carried out according to the refined method of researching thermal processes in contact drying of paper web. It is found, that the use of thermal insulation of the end caps of the drying cylinders provides a reduction in steam consumption for contact drying of the paper web without affecting the technological process. The research results can be used to reduce heat losses in the drying section of paper machines on cylinders that do not have thermal insulation of the end caps. For instance, for a paper machine consisting of 56 cylinders with a diameter of 1500 mm and a capacity of 7000 kg/h of absolutely dry paper, insulating their end caps saves up to 223 kg/h of steam for drying the paper web. Methods of detection of drying cylinders with increased content of condensation on permissible levels of temperature is developed and approved. A refined method for determining thermal losses during contact drying of the paper web on drying cylinders has been developed.

Conventional and Advanced Exergy and Exergoeconomic Analysis of a Spray Drying System: A Case Study of an Instant Coffee Factory in Ecuador

Instant coffee is produced worldwide by spray drying coffee extract on an industrial scale. This production process is energy intensive, 70% of the operational costs are due to energy requirements. This study aims to identify the potential for energy and cost improvements by performing a conventional and advanced exergy and exergoeconomic analysis to an industrial-scale spray drying process for the production of instant coffee, using actual operational data. The study analyzed the steam generation unit, the air and coffee extract preheater, the drying section, and the final post treatment process. The performance parameters such as exergetic efficiency, exergoeconomic factor, and avoidable investment cost rate for each individual component were determined. The overall energy and exergy efficiencies of the spray drying system are 67.6% and 30.6%, respectively. The highest rate of exergy destruction is located in the boiler, which amounts to 543 kW. However, the advanced exergoeconomic analysis shows that the highest exergy destruction cost rates are located in the spray dryer and the air heat exchanger (106.9 $/h and 60.5 $/h, respectively), of which 47.7% and 3.8%, respectively, are avoidable. Accordingly, any process improvement should focus on the exergoeconomic optimization of the spray dryer.

Closed cycle of air-steam mixture the drying section of paper machine

The energy efficiency of the drying section of paper machine is determined by the technology of heat flows arrangements in it. Paper drying is the most energy-consuming stage of paper production. The thermal mode of the drying section is provided by the steam condensate system which is a part of it. Analysis of exergy increments shows that almost all elements of the drying thermal process are characterized by low exergy efficiency. The main ways for increasing the degree of thermodynamic perfection of the processes occurring in the drying section of the paper machine are identified based on the exergy analysis. It is assumed that the deep internal heat recovery of the steam-air mixture for heating the source air will increase the exergy efficiency of the heat recovery plant and reduce heat removal to the environment. The effectiveness of development and implementation of a closed cycle use of steam-air mixture in the drying section was examined. Building a closed cycle provides that the air mainly has a process duty, that is, it is a transport agent for the transfer of moisture and heat along a closed circuit. The calculations show that the exergy efficiency of the processes in the recovery unit of the drying section of the paper machine of the existing production is 28.6% against 66.29% for the proposed method.

A Novel Method for Dankness Control in Paper Industries

In the evolving industrial revolution, automation plays an important role. Automating the machineries we use can reduce the human efforts on operating it. The basic process involved in paper manufacturing includes wood preparation, pulping, chemical recovery, bleaching and paper making to convert wood to final product. In paper industries, moisture content is the most important parameter in the drying section. Controlling the moisture content of the paper is important for maintaining the paper quality and for the economical usage of energy. The paper drying involves heat transfer, evaporation and moisture removal processes where steam pressure, cylinder surface temperature, hood balance and condensate removal plays important roles in determining drying capacity and final product quality. To attain the required quality and flexibility 5-7% moisture is necessary. Hence the heat in the dryer removes the moisture content of the paper leaving it dry. The dryers will be operated continuously to perform this process which leads to high power consumption. In order to reduce the power consumed the dryers will be operated only for some instance corresponding to the moisture level of the paper in the drying unit. Hence the overall efficiency of the plant will be increased, which leads to reduced power consumption and increased productivity.