Energy Efficiency Of Dryer Research Articles

Development and Testing of Small-Scale Flash Dryer for Maize Bran

Sun drying is the most common technique used to dry various food products due to its economic convenience. However, it is not effective owing to its unreliable nature leading to microbial deterioration and aflatoxin contamination of food. In Tanzania, about 1.3 million tonnes of maize bran are at risk of deterioration annually due to improper drying. The aim of this study was to design, fabricate and test an efficient small-scale flash dryer for maize bran. Using principles of material and energy balance, a small-scale flash dryer with a throughput of 500 kg of dry product per hour was designed resulting in a nominal diameter of 387 mm and a drying length of 20 m. Design calculations and drawings were done using MS Excel 2021 and SolidWorks 2018 respectively. Empirical procedures were used to fabricate and test the dryer. The material of construction used in the flash duct was food grade (stainless steel, SS 201). A fuel blend of Waste Engine Oil (WEO) and diesel (85%-15%) was used with a novel heavy oil burner. It was observed that at an inlet air temperature of 150 °C and air velocity of 12 m/s, moist maize bran was dried from 37% to 10% w.b. The fabricated flash dryer's energy efficiency, specific energy consumption, and specific energy utilization are 74%, 3.4 MJ/kg water evaporated, and 1.71 MJ/kg dry maize bran respectively. It was concluded that the fabricated small-scale flash dryer displayed improved energy performance compared to others presented in literature. Better instrumentation was recommended for feedback control on burner operation and process monitoring which further enhances the performance of the fabricated small-scale flash dryer.

Energetic and exergetic performances during drying of freshly harvested peanut with industrial mixed-flow dryer

Rapid drying of peanut is very important to maintain quality and reduce the risk of mildew, especially for peanut harvested in high moisture content in China. The modified mixed-flow dryer can dry freshly harvested peanut efficiently and evenly which is not available for traditional fixed-bed drying. However, the performances of energy and exergy of peanut drying using modified mixed-flow dryer are not clear, lacking of relevant data for equipment improvement and process formulation. Therefore the relevant investigation was carried out to evaluate the performance of fresh harvested peanut drying using industrial mixed-flow dryer with heat-pump full power heating and waste heat recovery The results show that the energy consumption is mainly consumed by heat-pump and centrifugal fan, accounting for 73.5% and 24.2% of all energy consumed respectively. The overall specific energy consumption and specific heat consumption are 1494.5 kJ/kg and 4706.1 kJ/kg respectively. The thermal efficiency and the energy efficiency are affected by the change of the temperature of airflow entering the drying chamber, both fluctuate over time, increase earlier then decrease later and rise again until the material temperature reach to a relatively steady temperature. And the energy efficiency of dryer (178.9%) is approximately triple of thermal efficiencies of drying chamber (56.1%) and dryer (59.4%) for the overall drying. The heat utilization ratio decreases gradually over drying time, with the overall value of 50.0% for drying chamber and 52.9% for dryer. The exergy efficiency of drying process earlier increases then decreases in the overall trend with the overall value of 51.3%. The exergy efficiencies of the drying chamber and whole dryer are both increased gradually with the overall value of 34.5% and 31.8% respectively. However, the variation tendencies of energy improvement potential rates are opposite to exergy efficiencies.

Toward natural convection solar drying of date palm fruits (Phoenix dactylifera L.): An experimental study

AbstractSun‐drying has proven to be the most sustainable technique for preserving food and agricultural products. However, conventional sun‐drying has limited drying capacity and can lead to significant losses in product quality. Greenhouse and indirect solar drying are advanced drying methods with improved product quality. In this article, the natural convection greenhouse dryer and natural convection indirect solar dryer were developed to study date palm fruits' drying characteristics (Phoenix dactylifera L.) in terms of moisture ratio and convective heat transfer coefficients. At the same time, the thermal performance of drying units was examined in terms of energy efficiency. The greenhouse dryer's higher convective heat transfer coefficient reduced drying time, and the indirect solar dryer's energy efficiency was obtained. The experimental data were fitted in various drying models, of which the Lewis model was found to be best fitted. The experimental errors were analyzed in terms of percent uncertainties. The drying costs of dried date palm fruits under greenhouse dryer and indirect solar dryer were found to be INR ₹ 22.37/kg (US$ 0.30/kg) and INR ₹ 30.14/kg (US$ 0.40/kg), respectively. Drying units could be a sustainable way of product drying, particularly in the rural areas where advanced drying mechanisms are still unavailable (1 USD = 74.8 INR as on 03 Feb, 2022).

Influence of load mass, drum speed and load composition on evenness of drying in a heat pump tumble dryer

This work investigates the evenness of fabric drying in a household heat pump tumble dryer. The evenness of drying was defined as the standard deviation of the fraction of water, evaporated from each fabric item. Drying experiments were performed according to the IEC 61121 standard, which was also followed to determine quantities and types of cotton fabric items (towels, pillowcases and sheets) within each load. Regression analysis was performed to develop models for evenness of drying as a function of load mass and drum speed. Similarities between the tumble dryer energy efficiency parameters and the evenness of drying were analyzed. A high level of agreement was determined between responses of energy efficiency, drying time and evenness of drying to changes in drum speed. Effects of load mass were however more complex and were reflected in a non-linear response of evenness of drying to changes in load mass – the best evenness of drying could be obtained at 2 kg load, followed by 6 kg and 4 kg load. Load composition was determined as an important factor affecting the evenness of drying. At larger loads, a sheet or a pillowcase in average contributed more to the un-evenness of drying than a towel. The presence of sheets and probably the ratio of sheets to other item types in the load were determined as the most probable factors that negatively affected the evenness of drying.

Influence of process parameters on the energy requirements and dried sliced tomato quality

AbstractThis study presents the effects of process parameters on the energy demand for drying and quality indices of dried tomato slices. The experiment was designed and analyzed with the Box‐Behnken method of Design Expert and conducted for drying 1800 g batch of a local variety of tomatoes with a solar‐electric dryer. The study examined the impact of varying process parameters: air temperature (50°C, 60°C, and 70°C), sample thicknesses (10, 15, and 20 mm), and air velocities (1.0, 1.5, and 2.0 ms−1) on the total and specific energy requirements, drying time, lycopene content, ascorbic acid, nonenzymatic browning index, brightness, and ratio of redness to yellowness of dried tomato samples, with emphasis on process optimization and drying time. The prediction of the optimal process condition is obtained using the desirability index technique. The results obtained show that the total and specific energy requirements for a batch of tomato varied from 7.82 to 125.48 kJ h and 6.70 to 179.83 kJ h g−1. The results of the analysis of variance (ANOVA) indicate that all the studied process parameters were significant with P > .05; with the maximum (40.21%) and minimum (19.82%) percent energy contribution by air temperature and air velocity, respectively. The energy of activation varies between 20.26 and 39.35 kJ mol−1. At the optimum process conditions of 57.28°C, 14.08 mm, and 1.3 ms−1, the specific energy requirements, lycopene content, ascorbic acid content, nonenzymatic browning index, brightness, redness to yellowness ratio, and drying duration are obtained as 103.313 ± 2.35 kW h kg−1, 58.7 ± 2.19 mg/100 mg dry matter, 2.9 ± 0.26 mg/g, 0.51 ± 0.033 absorbance unit, 60.074 ± 1.44, 0.77 ± 0.021, and 61.88 ± 8.93 minutes, respectively. The results of the study are of immense benefit to the food drying industry, as it provides food industries with improved drying parameters for enhancing dried tomato quality, as well as increasing dryer energy efficiency and cost‐effectiveness. Sugestions on prospects for further studies were given.

Improving the Performance and Energy Efficiency of Pneumatic Dryer for Okara

Abstract. A corrugated-pipe drying column and a multipass drying concept (one-pass and two-pass drying) were proposed in this study to improve the performance and energy efficiency of a conventional pneumatic dryer for okara. The performance (in terms of volumetric water evaporation rate and volumetric heat transfer coefficient) and the energy efficiency of the dryer were evaluated. With the use of the corrugated-pipe drying column, the moisture reduction of the okara, the volumetric water evaporation rate, and the volumetric heat transfer coefficient were enhanced. The specific energy consumption (SEC) of the drying process was also improved. The maximum values of the volumetric water evaporation rate and the volumetric heat transfer coefficient of 765 kgwater m-3 h-1 and 6966 W m-3 K-1, respectively, were found when drying was performed by the system using the corrugated-pipe drying column. The lowest value of the SEC of 3.03 MJ kgwater-1 was also observed. The lowest final moisture content of okara obtained after the two-pass drying was around 0.72 kgwater kgdrysolid-1. Keywords: Corrugated pipe, Multipass drying, Okara, Pneumatic dryer, Specific energy consumption, Volumetric heat transfer coefficient, Volumetric water evaporation rate.

Cleaner Coal: Improving Energy Efficiency at a Coal Preparation Plant in Western Canada

In an environment of constantly cyclical mineral market prices, operators of sites in the global mining industry are challenged to continuously improve processes to remain competitive with their peers. Although not necessarily a priority in the past, the issue of energy-efficiency project upgrades has moved to the forefront of mine operations. The dual benefits of serving as a means of offsetting rising energy costs and reducing emissions to reduce the environmental footprint are compelling. This article is a case study of one such energy-efficiency project recently implemented at a coal preparation plant in western Canada. The project began with a coal dryer energy efficiency feasibility study (EEFS) performed by a global energy services engineering company. Solicitation for the EEFS was supported by the local utility company serving the mine site, which funded the cost of the research. This article will review the analysis methods used and the recommendations included in the study and then describe site implementation of one of the key deliverables of the EEFS: a proposed plan to install a 6,000-hp medium-voltage adjustable frequency drive (AFD) to improve control of the main coal dryer exhaust fan. This article will also describe the unique AFD selected for installation for this load, including an overview of the power electronics topology and the resulting performance in delivering improved energy efficiency and process improvements. This upgrade ultimately ensured that energy and operational costs were reduced while the coal preparation plant delivered a superior end product to its customers.

APPLICATION OF SYNERGY OF ERGO-MECHANICAL SYSTEM TO IMPROVE FUEL ENERGY EFFICIENCY OF DRYER AND WORKING CAPACITY OF WOMEN EMPLOYEES IN INDUSTRIAL FACILITIES OF BANTEN AT BLAHBATUH GIANYAR BALI

Tumpeng and penek are important facilities on making of banten according to Hinduism in Bali. The use of tumpeng and penek on banten strongly associated with the believing on Tri Rnam and Panca Yadnya which based on the local wisdom of Tri Hita Karana, where its use continuously and in line with the implementation of religious ceremonies. The necessity of tumpeng and penek is constantly increases then it needs more effective and efficient in the creation, in order to fulfill the market demand. Tumpeng and penek making process is now done by home industry. Although by home industry, but the production process is still done on the floor with no ergonomic body posture and the drying process is done by a dryer without heat insulation that effects to the woman employees. These conditions affect the working capacity and energy efficiency of the fuel of dryer. Based on the above problems it is necessary to study the synergy of ergonomics and mechanical systems which in this case is expressed as synergy ergo-mechanical systems by ergonomically synergy between the employees and the mechanical system of the dryer in order to increasing labor productivity and efficiency. This is done by redesigning the work system and dryer system that aims to increasing working capacity by reducing workload, decreasing complaints of musculoskeletal, decreasing in fatigue, increasing of comfort, improving energy efficiency of fuel. Research experiments conducted within subject design by involving 15 respondents that randomly selected, all of whom studied in 2 (two) periods, Period I and Period II. Period I is the period prior to the application of synergy ergo-mechanical system, and the second period is the period after the application done of synergy ergo-mechanical system. Each carried in three days period, with washing out of 2 days and 5 days of adaptation. Data were analyzed with descriptive and test for normality using the Shapiro-Wilk. Different test has been done when the data were normally distributed with a t-paired, unless analyzed by the nonparametric Wilcoxon test with the significant-degree of about 5%. The results showed that of about 21.90% reduction occurred in workload, musculoskeletal complaints of about 15.10%, about 22.23% of fatigue, increasing employee comfort of about 59.18%, and fuel efficiency of dryer of about 13.29%. It concluded that synergy of ergo-mechanical system applications improves energy efficiency of dryer fuel and work capacity of industry women employees of banten facility at Blahbatuh Gianyar Bali.

Batch uniformity and energy efficiency improvements on a cabinet dryer suitable for smallholder farmers.

Drying can add value, facilitate transport and extend the storage life of agro-products; therefore, in developing countries with poorly established cool-chains, drying is particularly effective. Furthermore, drying within small-scale village-based enterprises contributes to rural development. However, most equipment suitable to such operations yields a product of non-uniform quality and shows low levels of energy efficiency. The aim of this research was to improve the batch uniformity and the energy efficiency of a cabinet dryer suitable for smallholder farmers. Experiments were carried out with the cooperation of a dryer manufacturer and a group of users. On each trial 144.5kg of peeled and deseeded litchis were placed at the dryer's 17 trays, that were stacked atop each other. Moisture content (wet basis) was reduced from 87 to 23% in about 15.5h. It was found that a low-cost modification to the dryer chamber's air inlet was able to improve heat distribution and increase the uniformity of the fruit's moisture content. In the original design, at the end of the drying process, moisture content of the fruits on the top tray was 38% while at the bottom tray was 12%. The modification to the dryer reduced this disparity and the final moisture content of the fruits placed at the top tray was 25% while at the bottom tray was 21%. In addition, the modification reduced the dryer's air mass flow from 0.3 to 0.1kgs(-1) without jeopardizing drying forces, consequently the dryer energy efficiency increased from 33 to 42%.

On Dryer Energy Performance and Controllability: Generalized Modeling and Experimental Validation

This work presents an approach to compute dryer energy efficiency using air flowrate step responses and establish a link between drying energy efficiency and process controllability. The approach is based on the temperature drop between the dryer inlet and outlet air under adiabatic conditions and so decouples water evaporation from heat loss and product heating effects on dryer temperature drop. As such, the computation is accurate even for dryers with significant heat losses where the traditional use of actual temperature drop measurements is grossly inaccurate. The approach is tested and verified on two experimental case studies involving significant heat losses: the first, a continuous fluidized-bed dryer (from literature); the second, a conventional and zeolite wheel-assisted batch dryer designed in the current study.

Improving dryer energy efficiency and controllability simultaneously by process modification

This work establishes a relationship between dryer energy performance and controllability using energy balances and process resiliency analysis. It is shown that using the process gain matrix, the dryer energy efficiency can be reliably calculated with conditions for simultaneous controllability improvement established. By incorporating a drying rate modifying system such as a desiccant dehumidifier as an add-on, these conditions are shown to be achievable due to the extra dehumidification which can be manipulated using the additional degrees of freedom introduced by the sorption system. Due to the adsorbent regulation properties which are enhanced by high-temperature regeneration, the resilience of energy performance to disturbances is significantly improved compared to conventional dryers. Also, a desiccant system performance indicator, the “adsorber–regenerator net energy efficiency ARNEE” is introduced and it is shown that energy efficiency improvement is possible only if the ARNEE is greater than the energy efficiency of the stand-alone dryer.

Improving Adsorption Dryer Energy Efficiency by Simultaneous Optimization and Heat Integration

Conventionally, energy-saving techniques in drying technology are sequential in nature. First, the dryer is optimized without heat recovery and then, based on the obtained process conditions, heat recovery possibilities are explored. This work presents a methodology for energy-efficient adsorption dryer design that considers sensible and latent heat recovery as an integral part of drying system design. A one-step pinch-based optimization problem is formulated to determine the operating conditions for optimal energy performance of such an integrated system subject to product quality. Because the inlet and target stream properties of the heat recovery network are determined by the adsorption drying conditions, they are unknown a priori and thus are determined simultaneously within the overall optimization using the pinch location method. Energy balances are written above and below the various pinch point possibilities and the optimal pinch point is that which minimizes the amount of external heating utility required while satisfying drying and thermodynamic constraints. Results for a single-stage zeolite adsorption drying process with simultaneous heat recovery optimization show a 15% improvement in efficiency compared to a sequentially optimized system. The improvement is traceable to alterations in enthalpy-related variables like temperatures and flow rates. The discrepancy in optimal operating conditions between the sequential and simultaneous cases underscores the need to change system operating conditions when retrofitting for heat recovery because previous optimal conditions become suboptimal when heat recovery is introduced. Also, compared to a conventional dryer (without an adsorption process) operating under similar conditions, energy consumption is reduced by about 55%.

Energy Efficiency and Drying Kinetics of Recycled Paper Pulp

In this work, the influences of the air temperature and velocity on the drying kinetics of recycled paper pulp were analyzed. The increase of both variables positively influences the process, concerning the final moisture content and the drying time. However, optical microscopy and visual observation showed worse quality of the paper for drying conditions of high air temperature and velocity, presenting less uniformity and overdried surfaces. The dryer energy efficiency was evaluated by performance parameters and the results were compared with the ones obtained for other types of industrial paper dryers, presenting good agreement.

A Study for the Thermal Treatment of Dehydrated Sewage Sludge with Gas-Agitated Double Screw Type Dryer

A specially designed dryer has been developed for the thermal treatment of dehydrated, highly viscous sewage sludge with moisture content more than 80 wt.% by an gas-agitated, double-screw type dryer system. The treatment capacity of sludge dryer was about 100 kg/h. It consists of burner, feeding hopper, hot gas supplying ducts with double screw conveyor, damper and outlets of drying gas and dried material. The sewage sludge was transported by the revolution of the cylinder conveyor together with the tumbling and mixing action of the screw and lifters. The heating of the sludge was made efficient by the combination action of conduction and convection modes together with the gas-agitation process. The conduction occurred across the surface of the combustor cylinder, the convection was made by the flue gas interaction over the sludge and the agitation action through holes of conveyor cylinder into the bottom of the sludge. The number and location of gas-agitation holes and thereby the fraction of drying gas into the agitation holes were evaluated by numerical calculation of turbulent reacting flow. To evaluate the performance of the dryer developed in this study, a series of parametric experiments were performed in terms of important variables. In general drying process occurred successfully even for the highly agglomerating municipal sewage sludge through the first lumped plastic phase to a fine granulate state when the heat and mass balance was matched by adjusting rpm of the conveyor, burner capacity, and the fraction of gas-agitation. Further the avoidance of initial sludge agglomeration was considered to be important by the combination action of screw and lifter. The weight of the sludge was reduced approximately by 60% and therefore the volume of sludge was decreased to approximately 75% of initial volume with the water content of 10–20%. Energy efficiency of dryer was evaluated in the range of 70–75% at the sludge feed rate, 100 kg/h. The results obtained show the development of a robust, drying action applicable to highly viscous and high moisture content sewage sludge by the novel design of conveyor system and gas-agitation process developed in this study.