The effect of drying kinetics models on the energy efficiency of a conveyor-belt convective drying system was investigated. Experiments were conducted on the material to be dried, and the system was ...modeled using two drying kinetics models. Mathematical models incorporating the drying kinetics model were used to create a module that designs the drying system under given operating conditions. A comparison of the design results of two drying kinetics models under various operating conditions demonstrated that the total drying time of the material can be incorrectly estimated by an average of 35 % when an inappropriate model is used. Furthermore, this inaccurate estimation of the drying time leads to the total energy usage of the system being up to 32 % higher than necessary. These results demonstrate that a good dryer design cannot be guaranteed merely by using experimental data of the material to be dried; the design process must include selection of the most suitable model among various models considering the drying characteristics. Consequently, an appropriate algorithm that incorporates the selection of suitable drying kinetics models can contribute to reduced energy consumption and carbon emissions in various energy-intensive drying processes, especially with the widespread use of conveyor-belt dryers.
•Investigation of the impact of drying kinetics model selection on dryer energy use.•Drying experiments with two materials using a bench-scale conveyor-belt dryer.•Development of a dryer design module incorporating mathematical process modeling.•Inappropriate model usage: average deviation in drying time of 35 %.•Inappropriate model usage: energy usage increase up to 32 %.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•Olive leaves were dried in a conveyor belt dryer aimed at supercritical extraction.•Influence of drying conditions on extraction was investigated.•Leaf temperature and output ...moisture were successfully predicted by a drying model.•Higher extraction yields and AA were found in samples dried at 50 °C for 300 min.•Total phenolic compounds content was enhanced in samples dried at 70 °C for 60 min.
The influence of drying conditions on the composition of supercritical extracts recovered from olive leaves was investigated. Leaves were dried on a conveyor belt and the effects of air temperature and residence time on the extraction kinetics, global yield, antioxidant activity, total polyphenols content and chemical profiles of the extracts were evaluated. Inlet air temperatures of 50, 60 and 70 °C with residence times of 180, 120 and 60 min, respectively were tested. A model based on mass and energy balances with effective heat and mass transfer coefficients fitted from experimental data was used to describe the drying process. The temperature and output moisture of the leaves were well predicted by the model. The extraction kinetics was not significantly affected by the drying conditions (air temperature and residence time), but the extraction yield was enhanced for samples dried at 50 °C/180 min whereas the higher values of antioxidant activity and phenolic contents were found at 60 °C/120 min. Sovová’s model was effective in describing the supercritical extraction of olive leaves and can be used to estimate the extraction kinetics and mass transfer coefficients.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Hops are an essential raw material in beer brewing, providing typical flavor and aroma characteristics to beer. Freshly harvested hop cones must be dried immediately. While conveyor-belt dryers are ...widely used, their operation is largely based on operator experience, which leads to energy-intensive operation whilst adversely affecting the quality. This work identifies the bottlenecks in hops drying by summarizing the results of previous studies, and experimentally analyzing an industrial dryer. Heterogeneous air-distribution, uneven drying and suboptimal control-strategies were identified as key issues which can be battled with accurate model-based process analysis and smart control systems, both of which need further research.
Full text
Available for:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Dry biomass provides considerable benefits for combustion, such as increased boiler efficiency, lower flue gas emissions and improved boiler operations, compared to fuels with high moisture. Drying ...is however an energy-intensive pre-treatment. Utilising low-grade, waste heat – of which large amounts are available from many process industries – could significantly reduce energy consumption. The integration of a drying process into a power station fuel system was investigated; the results are presented here. Waste heat from a process industry plant (100 MW output) was utilised as the heat source for drying. The biomass, pine chips at 60wt% moisture, was dried and could then be provided as the input fuel for a subsequent 40 MW power plant. The process consisted of a belt conveyor as the dryer and either flue gases or superheated steam (generated from the hot cooling water) as the heat source. Flue gas usage would result in lower capital costs (∼€2.5 m), but environmental issues, such as pollutant emissions must be considered. Superheated steam can combine short drying times, good heat recovery and environmental protection, but would entail greater capital costs (∼€3 m). A 3–4 year return on the initial investment was calculated for both technologies, but profitability was sensitive to fuel price.
▸ Dry biomass greatly enhances combustion compared to high-moisture fuels. ▸ Drying is thus often necessary but can be highly energy-intensive and costly. ▸ Using low-grade/waste heat from process industries can reduce energy consumption. ▸ This process used flue gas or superheated steam as the heat source and a belt dryer. ▸ A 3–4 year return on the initial investment was calculated for both technologies.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study examines the impact of biomass drying on the overall efficiency of a Biomass-to-Liquids (BTL) process co-producing Fischer-Tropsch (FT) syncrude and heat. The proposed BTL process is based ...on steam-blown dual fluidised-bed gasification of biomass, simplified gas clean-up and FT synthesis. Biomass drying was found to have a significant effect on both the FT product yield and the overall thermal efficiency of the BTL plant. In the considered concept, FT off-gases are used as supplementary feedstock in the oxidiser, alongside with char, to satisfy the heat demand in gasification. Drying of the biomass feedstock leads to reduced need of water evaporation during gasification. This in turn reduces the demand for off-gases in the oxidiser, and allows to produce more syncrude (and less off-gases) in the FT unit. The simulations indicated that more extensive drying could result in a significant increase in FT syncrude yield: the thermal efficiency of FT syncryde production increased from 47.7% to 54.6% as the moisture mass fraction of the biomass feed was reduced from 30% to 8%. The highest overall thermal efficiencies of 85–88% were obtained with a two-stage drying concept that combines a belt dryer and an indirectly-heated steam dryer.
•Biomass drying plays a key role in maximising the overall efficiency of the plant.•More extensive drying allows producing more Fischer-Tropsch syncrude.•The highest overall thermal efficiency was obtained using a two-stage dryer.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The cost of drying microalgae chlorella in a conveyor belt dryer using exhaust flue gas of an industrial plat is estimated.•The dryer is mathematically modeled to obtain the moisture distribution on ...the belt.•The economics is compared to spray dryer and conveyor belt dryer utilizing natural gas.•Using conveyor belt dryer coupled with waste heat recovery system improved the drying costs.
The objective of this research is to estimate the cost of drying microalgae chlorella in a conveyor belt dryer using waste heat from an industrial source. The recycling system consists of a run around thermal fluid between two tube heat exchangers. The dryer is mathematically modeled and the mass transport coefficient is obtained from empirical thin-layer kinetic data.
The dryer and heat recovery system are designed for the production of 1000kg/h dried microalgae at a moisture content of 10% (wet basis, w.b.). The input moisture content can range from 35 to 75% (wet basis). Depending upon the applied Hand factor, the total cost to dry microalgae from 55% to 10% ranges from $46.13 to $109.64 per ton of dried product. Using natural gas assumed at $6.27/GJ, the drying cost increases to $83.47 per ton (using hand factor equal to 1). The drying cost using a commercial spray dryer is $109.05 per ton of dried product (using hand factor equal to 1). The paper discusses the sensitivity of drying costs to initial moisture content as well. The results show that integrating waste heat recovery with conveyor belt dryer decreases the drying costs of chlorella drying in comparison to two other drying methods.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Fatigue life analysis and structure optimization of the conveyor belt bedplate of the belt dryer.•The influence of the polygonal effect of the chain drive on the motion trajectory of the conveyor ...bedplate is analyzed.•The stress experiment was carried out on the conveyor belt bedplate, and the reason for fracture was analyzed.•The proposed calculation method provides a reference for the fatigue life analysis of the critical components of the belt dryer.
The chain drive conveyor belt (CDCB) of the belt dryer is prone to generate impact load during operation, and the conveyor belt bedplate (CBB) will cause fatigue damage and fracture. This study presents an approach for calculating fatigue life, which combines the automatic dynamic analysis of mechanical systems (ADAMS), finite element analysis software (ANSYS), fatigue analysis software (FE-SAFE), and experimental stress analysis. The virtual prototype model for simulation of the CDCB is established, and its motion stability, contact impact force and motion trajectory are analyzed. The study shows that the chain drive polygon effect will cause periodic changes in velocity, and the motion trajectory has very good similarity. The stress experiment results show that the stress was considerable during the chain drive meshing process. The finite element analysis results show that the maximum stress of the old CBB is higher than the yield strength of the material, and the equivalent stress of the new CBB is lower than that of the old CBB. The area of the maximum stress of old CBB presents a fracture, which indicates the fatigue failure of the old CBB. The finite element calculation results were imported into FE-SAFE for fatigue life analysis, which compared the fatigue cycle number and safety factor of the old CBB and the new CBB. The results show that the new CBB can extend the service life of the belt dryer. The proposed analytical method for fatigue life is simple and effective and can serve as a reference for the fatigue life analysis of the key components of the belt dryer.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study investigated the effects of various drying conditions involving microwave power, air velocity, and sample mass on the drying behavior, starch gelatinization properties, and ...gamma‐aminobutyric acid (GABA) content of germinated red adzuki bean (GRAB) under continuous microwave drying. Increasing the microwave power and lowering the sample mass can promote GRAB drying and shorten the total drying duration; improving the air velocity limited the temperature elevation of GRAB to affect water removal to some extent. The drying rate had only the rising‐ and falling‐ rate stages throughout the drying process. Microwave drying lowered the gelatinization temperature and enthalpy to facilitate the starch gelatinization of GRAB. The microwave power and sample mass had significant effects on the GABA content of the final dried GRAB. This study may provide guidance for understanding and follow‐up improving the continuous microwave drying production of germinated bean products like GRAB.
Practical applications
GRAB is consumed as a nutritional food source due to its high starch and protein contents, low fat, and rich bioactive ingredients like GABA. Drying processing is a needed step for fresh GRAB to facilitate long‐term storage and quality retention. This study evaluated the drying behavior and quality attributes of GRAB in a continuous microwave belt dryer, and the research results have underlying application potential and may provide guidance for microwave drying production of germinated bean products like GRAB.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Belt dryer is commonly used in the production of the dried aquatic feed. Poor airflow distribution during the aquatic feed drying process leads to moisture content variation that could be lead to ...high energy consumption and poor feed quality. A newly designed belt dryer with improved drying efficiency was used to study airflow distribution. In order to analyze airflow distribution inside the dryer, a model for a new belt dryer was established. Airflow distribution under five different feed thicknesses (20 mm, 30 mm, 40 mm, 50 mm, 60 mm) were simulated using computational fluid dynamics (CFD) techniques and verified by experimental data. A finite volume method with porous media formulation was used to simulate airflow distribution inside the dryer. The experimental results showed that there was good consistency between the experimental and simulated values of airflow velocity. The airflow velocity on the feed layer range from 0.28 m/s to 0.98 m/s with a standard deviation of up to 0.17 m/s. Airflow distribution inside the dryer was affected by the feed thickness and air space size. When the feed thickness was 40 mm, the uniformity of the airflow velocity at the surfaces of the feed can reach the best results.
Full text
Available for:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Introduction. In the process of convective drying, there is a contradiction between drying speed and energy efficiency. One of the solutions to this contradiction is the use of targeted energy supply ...to the product. The method of targeted energy supply is the use of electromagnetic radiation in the drying process. Aim of the Article. The study was aimed at obtaining the coefficients of a logarithmic model for calculating the performance of a belt IR dryer for drying carrots. Materials and Methods. There were studied a modular belt IR dryer with the ability to control the speed of the belt and the power of the emitters. To describe the process, there were used standard models of the dependence of relative water content on drying time. Results. An analysis of the drying rate curves showed an extreme effect of the belt speed on the drying rate. At belt speeds above 10 mm/s, an increase in belt speed leads to an increase in the duration of the drying process. To describe the kinetics of the drying process at IR powers of 170, 300, and 450 W, there was used a logarithmic model, as it most adequately describes the experimental data. Discussion and Conclusion. For this type of dryers it is recommended to use the belt speed of about 10 mm/sec. The obtained coefficients of the logarithmic model are used to calculate the capacity of the drying unit.
PDF
