Low-temperature Drying System Research Articles

Performance Optimization and Numerical Simulation Study of Sludge Low-Temperature Drying System

Performance Optimization and Numerical Simulation Study of Sludge Low-Temperature Drying System

Experimental investigation of circulating fluidized bed combustion of dry powders of coal slime

Effective combustion of coal slime in circulating fluidized bed (CFB) boilers is essential for the sustainable development of clean coal technology. To overcome issues related to burning wet coal slime in CFBs, we propose to dry coal slime in a low-temperature drying system and burn the dried fine powders in a CFB with a highly efficient separator. This study reports a series of experiments conducted in a 4MWth pilot-scale CFB combustion test facility to assess the feasibility. The results demonstrate that the dried slime particles, which have a particle size distribution similar to that of circulating ash particles, can be burned stably, efficiently, and cleanly. The combustion of fuels with size distributions similar to that of circulating ash particles increases solids circulation rates, betters solids concentration distribution, enhances heat transfer combustion and improves operation and SO2 and NOx controls. Therefore, the study presents a potential opportunity to advance CFB combustion technology.

Assessment of a Low Temperature Closed-Cycle Grain Drying System

This study analyzed the drying efficiency of a prototype low temperature closed-cycle grain drying system. The main principle of this drying system was the heat pump system working as a dehumidifier. The main component of this drying equipment included a compressor, a condenser, twin evaporators, and a fan. Two drying studies (denoted as trial 1 and trial 2) were conducted to assess the overall drying performance of this low temperature drying system. To calculate the drying efficiency, the total energy consumption was divided by the amount of water removal for each trial; the drying efficiency was reported in the form of Btu/lb of water removal. We also tested corn seed germination to determine if this drying process had an effect on seed germination performance. The drying efficiency results for trial 1 and 2 were 1036 Btu/lb water removal and 869 Btu/lb water removal, respectively; compared to other on-farm drying methods this drying system had fairly high drying efficiency. The germination test results showed that this drying system had no adverse effect on germination performance.

Investigation of energy-efficient solid desiccant system for wheat drying

The study investigates the applicability of solid desiccant system for drying of freshly harvested wheat grains in order to reduce the moisture content to an optimum level. Fast and low-temperature drying systems are required by today’s drying industries in order to provide economical and safe drying. Therefore, comparison of desiccant drying has been made with the conventional method in terms of drying kinetics, allowable time for safe storage, the total time for drying cycle, and overall energy consumption. It has been found that the air conditions of proposed desiccant drying system provides a high drying rate and longer allowable storage time for safe drying. As the desiccants possess water adsorbing ability by means of vapor pressure deficit, therefore, the desiccant system successfully provides low-temperature drying which ensures the quality of wheat grains. Overall energy consumption is estimated for both conventional hot air drying and desiccant drying system. It has been found that the desiccant system requires less energy as drying is accomplished at minimum level of air flow and within allowable storage time. In addition, the overall performance index of the desiccant system is higher at all temperatures. The study is useful for developing a low-cost and sustainable drying technology for various agricultural products. Keywords: desiccant, solid desiccant system, drying, grain, wheat, performance evaluation DOI: 10.25165/j.ijabe.20191201.3854 Citation: Hanif S, Sultan M, Miyazaki T, Koyama S. Investigation of energy-efficient solid desiccant system for wheat drying. Int J Agric & Biol Eng, 2019; 12(1): 221–228.

Experimental Research of Drying Red Chili by Two Methods: Solar Drying and Low - Temperature System Drying

The objective of this research was to experiment of solar drying and Low-Temperature system drying (45-50%RH, 27-30°C) for drying red chili. Solar drying during daytime (greenhouse dryer) and during at night using climate control system to coordinate with air conditioner in drying. The Low-Temperature system consists the humidity control unit (ultrasonic), air-conditioner, temperature and relative humidity sensor, heating coil and microcontroller unit. For Low-Temperature drying process, climate control system controls the compressor in the air conditioner by turn on-off to control the temperature and relative humidity in the chamber. The dehumidification process by controlling the temperature of the surface evaporator coil is decreased to the dew point temperature, making water vapor in the air condensed to be water drops. The result of solar drying and Low-Temperature system takes 52h to reduce the moisture content of about 74% to 13.5% (w.b). For temperature and relative humidity of the solar drying at 50 °C and 36%RH by average, in during daylight and at night with Low-temperature drying system by the climate control system coordinate with air conditioning system in moisture reduction at 27-30°C and relative humidity at 45-50%RH for drying chili in the night. These processes were found to have average temperatures and relative humidity for drying at 27.55°C, 47.37% RH., moisture condensation rate and specific energy consumption at 2.16 kgwater/h and 0.75 MJ/kg.

Evaluation of Low-Temperature Drying System by Thermal Exergy

Evaluation of Low-Temperature Drying System by Thermal Exergy

Dehydration of food crops using a solar dryer with convective heat flow

A solar drying system designed on the principles of convective heat flow was constructed from local materials (wood, metals and glass sheets) and used to dry food crops (cassava, pepper, okro, groundnuts, etc.). The solar collector could transfer 118 W m −2 thermal power to the drying air. The thermal exchanges within the dryer were determined from a psychometric chart. Ambient air at 32°C and 80% relative humidity (RH) could be heated to 45°C at 40%. The crops were dried to a final moisture content of <14% and were preserved for a period of one year without deterioration. The low-temperature drying system ensured the viability of the seeds for planting. The drying process can be represented by an empirical equation of the form M( t)= M Oexp (− kt) or d M/d t=− kM, where M O is the initial moisture content, M( t) is the moisture content at time t, and k is the drying constant. Under identical conditions, a high value of k was correlated with a shorter drying period. The drying process takes place in two phases: constant rate and falling rate periods, and the drying equation was solved to predict the total drying time. The mechanisms for the dehydration are the removal of unbound “free” water in the cell cavities and of “bound” water (water films) trapped within cells or chemically bound with solids as water of crystallization.

Analysis and design of a differential sunshine recorder

A solar drying system designed on the principles of convective heat flow was constructed from local materials (wood, metals and glass sheets) and used to dry food crops (cassava, pepper, okro, groundnuts, etc.). The solar collector could transfer 118 W m−2 thermal power to the drying air. The thermal exchanges within the dryer were determined from a psychometric chart. Ambient air at 32°C and 80% relative humidity (RH) could be heated to 45°C at 40%. The crops were dried to a final moisture content of <14% and were preserved for a period of one year without deterioration. The low-temperature drying system ensured the viability of the seeds for planting. The drying process can be represented by an empirical equation of the form M(t)=MOexp (−kt) or dM/dt=−kM, where MO is the initial moisture content, M(t) is the moisture content at time t, and k is the drying constant. Under identical conditions, a high value of k was correlated with a shorter drying period. The drying process takes place in two phases: constant rate and falling rate periods, and the drying equation was solved to predict the total drying time. The mechanisms for the dehydration are the removal of unbound “free” water in the cell cavities and of “bound” water (water films) trapped within cells or chemically bound with solids as water of crystallization.

Potential for Aflatoxin Development in Low Temperature Drying Systems

ABSTRACT AN equilibrium grain drying model has been used to simulate temperatures and equilibrium relative humidities in the grain mass during low temperature drying to predict the potential for aflatoxin development. The information obtained has been used to indicate regions within the U.S. where a significant potential for aflatoxin development exists.

Evaluation of the Feasibility of Solar Energy Grain Drying

ABSTRACT A model for simulating moisture content changes and grain quality deterioration in low-temperature drying systems is presented. The model is used to simulate solar-supplemented and ambient-air drying performance for St. Cloud, MN, Des Moines, lA and Indianapolis, IN. Results include minimum airflow rates, energy requirements and evaluation of economic feasibility for solar drying compared to ambient-air drying.

Quality Changes During high low temperature drying

ADSTRACT INCREASING emphasis on grain quality and energy conservation has created a need to develop drying systems that will deliver a better quality product with lower energy consumption for drying. There is also the problem of increasing the capacity of a drying system as the system expands to size. A combination high-temperature, low-temperature drying system as described by Cloud et al. (1976) and Morey et al. (1976) may provide some solutions to these three concerns. The purpose of this study was to determine on a field scale the effects of combination high-temperature, low-temperature drying on quality of grain as compared to conventional high-temperature drying. Quality factors considered included the grading factors of broken corn and foreign material, and test weight, breakage sus-ceptibility as measured by the Stein breakage test, germination, and mold development. Combination drying treatments included use of a high-temperature cross-flow batch dryer to deliver grain hot to a bin equipped for low-temperature dry-ing. The moisture content of the corn delivered from the dryer must be at a level that can be safely handled in a low-temperature system (18 to 22 percent) after being cooled. The results of this work are intended to assist in pro-ducing guidelines for management of combination drying systems which will most effectively improve grain quality.