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![Energy consumption for selected dryers [5].](profile/Jan-Havlik/publication/339833131/figure/tbl1/AS:1152323346792448@1651746703263/Energy-consumption-for-selected-dryers-5_Q320.jpg)
This paper focuses on indirect biomass drying. It compares the operating characteristics of a laboratory-scale drum dryer and a pilot-scale rotary dryer. Before the design of an industrial dryer for a specific material, it is important to experimentally prove the process and to determine the drying characteristics of the material. To verify the por...
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Context 1
... drum has an adjustable revolution speed. On the inner side (the drying material side), heated flights (see Figure 6) are used to maintain a longer contact time with the heating surface and to increase the surface area of the dryer while maintaining its volume. The inner lateral surface area of the dryer is 6.42 m 2 and the dryer volume is 0.59 m 3 . ...
Context 2
... drum has an adjustable revolution speed. On the inner side (the drying material side), heated flights (see Figure 6) are used to maintain a longer contact time with the heating surface and to increase the surface area of the dryer while maintaining its volume. The inner lateral surface area of the dryer is 6.42 m 2 and the dryer volume is 0.59 m 3 . ...
Context 3
... water is carried away out of the dryer by a header in the upper part of the dryer due to small overpressure in order of tens of Pa formed in the dryer as a result of developing steam during drying. The drum configuration is shown in Figure 6. The drum is heated by steam, which condenses inside the tube system. ...
Context 4
... value without heat loss was calculated from the measured value, during operation without a material charge, and the heat loss of the dryer was measured as 3 kg of condensate per hour. The drum configuration is shown in Figure 6. The drum is heated by steam, which condenses inside the tube system. ...
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Citations
... The cultivated biomass is then subjected to a drying pre-treatment to remove the excess moisture content. The energy inputs of this phase were estimated according to Havlik et al. (2020) [68], who estimated a flow of 2.9 kWht/kg of evaporated water. Assuming a water content of 23% (P.I.) in the WDC, the resulting heat needed to remove the excess of moisture amounts to 20.9 kWht/FU. ...
The growing attention regarding the environmental challenges in the energy sectors pushes the industrial system toward the investigation of more sustainable and renewable energy sources to replace fossil ones. Among the promising alternatives, biomass is considered a valid source to convert the system and to reduce the fossil fraction of the national energy mixes, but its multiple potential uses need an environmental evaluation to understand the actual benefit when it is used as an energy resource. For this purpose, life cycle assessment (LCA) is applied to a wood biomass gasification system aimed to produce electricity and heat generated after the combustion of the produced syngas and the management of the biochar. The aim is to provide a quantitative comparison of (i) a baseline scenario where wood biomass is sourced from waste and (ii) a second scenario where wood biomass is drawn from dedicated cultivation. A further evaluation was finally applied to investigate the environmental implications associated with the biochar composition, assuming it was used on land. The proposed strategies resulted in an environmental credit for both the examined scenarios, but the outcomes showed a net preference for the baseline scenario, resulting in better environmental performances for all the examined categories with respect to the second one. It underlines the potentialities of using waste-sourced biomass. However, according to the Climate Change category, if on-site dedicated biomass cultivation is assumed for the second scenario, the baseline is considered preferable only if the biomass transportation distance is <600 km, which is estimated as a theoretical distance for scenarios to break even. Finally, biochar composition proved a particular concern for toxicity-related categories. This study highlights the importance of applying objective and standardized methodologies such as LCA to evaluate energy production systems based on alternative sources and to support decision-making toward achieving sustainability goals.
... MC reduction can be done by using a drying system where the heat source used can be either stand-alone or by utilizing heat from the waste of industrial activity. The most common dryer types are rotary dryers [22][23][24][25], flash dryers [26], fluidized-bed dryers [26][27][28][29], and belt dryers [30,20]. Lee [13] in his experiment utilizing an electrical air heater found out that for reducing the MC of woodchip from 40 % to 10 % MC needed 23.0 min. ...
This paper is to study the drying method to reduce the moisture content (MC) of the woodchip. The methods used are to utilize the heat from solar and waste heat from the Biomass Power Plant (BioPP). By using a 250 °C heat waste from the BioPP, and stirring on the woodchip inside the drying equipment, the results obtained to reduce the MC from more than 40 % to MC around 20 % will take 2 h and 4 h faster than that which was not done on woodchips. Reducing MC from 40 % to 20 % will save 25.44 % on the woodchip consumption for combustion in the boiler of the BioPP. An analysis related to MC, CV, and woodchip consumption in generating electricity is also carried out. When MC is 26.70 %, the CV is 13.5 GJ T⁻¹, and the woodchip consumption becomes 4.62 T h⁻¹ and 1.31 T MWh⁻¹, the energy produced is 764.7 kWh T⁻¹. When the MC is higher, 47.68 %, causing the CV to become 9.8 GJ T⁻¹, it is found that the consumption of the woodchips becomes 6.41 T h⁻¹ and 1.81 T MWh⁻¹, the energy produced is 551.3 kWh T⁻¹.
... Tada et al. (2017) [21] used the Péclet number to determine the dominant heating mechanism ina granular bed and obtained that the rate of heat transport is characterized using the Nusselt number and a fluids-inspired relationship correlating this quantity with a Péclet number. Recently, Havlik and Dlouhý (2020) [22] comparatively studied the experimental drying characteristics of green wood chips and wet bark from open air storage with moisture contents ranging from 50 to 65 wt (%) in indirect dryers with drum and rotary configurations. In this study, a laboratory-scale indirect dryer was used to better understand the biomass drying process and to experimentally obtain the volumetric and square evaporation capacities [22,23] Their study shed light on the biomass drying process and experimentally obtained the volumetric and square evaporation capacities. ...
... Recently, Havlik and Dlouhý (2020) [22] comparatively studied the experimental drying characteristics of green wood chips and wet bark from open air storage with moisture contents ranging from 50 to 65 wt (%) in indirect dryers with drum and rotary configurations. In this study, a laboratory-scale indirect dryer was used to better understand the biomass drying process and to experimentally obtain the volumetric and square evaporation capacities [22,23] Their study shed light on the biomass drying process and experimentally obtained the volumetric and square evaporation capacities. These capacities were used as scaling parameters, finally using the square evaporation capacity to design and build a pilot-scale rotary dryer. ...
... Similarly, decreasing the steam pressure to 4 (bar) favors the final moisture reduction for lower feeding frequencies, reaching a moisture reduction of from 25 to 42 (%). These results are consistent with those reported in the literature, where higher evaporation rates are achieved using high feed rates of wet material and high vapor pressure, and where lower moisture contents in the dry biomass are achieved when the feed flow is reduced [22,31,32]. ...
An experimental study and dimensional analysis of the effective heat transfer coefficient in a continuous-indirect rotatube dryer using forest biomass as the granular material isare developed in the present work. The study employed a factorial design 33 to investigate the effects of feed flow frequency (20–35–50 (Hz)), drum rotational velocity (6–8–10 (rpm)), and saturated vapor pressure (4–5–6 (bar)) on the heat transfer coefficient. During steady state conditions, the moisture content profiles and inlet and outlet temperatures were measured within the experimental region, and parameters, such as the effective heat transfer coefficient, solid retention change, and moisture content ratio were studied. The results showed that heat transfer was optimized with high solid feeding rates, low pressure, and low rotation, with solid feeding being the predominant factor. The moisture content profiles revealed a change in the hydrodynamic behavior, with the center point of the experimental region being the least optimal. The dimensional analysis yielded a Nu number as a function of Pe, Fr, and the feeding dimensionless number. A new dimensionless energy efficiency number improved the coefficient correlation from 85.88 (%) to 94.46 (%), indicating the developed model potential to predict dimensionless variables and scale continuous-indirect rotatube dryers.
... Considering the resulting SCP as a nutritional yeast, the drying process was meant to reduce the moisture content of the microbial cells to 10 % and also inactive the cells without compromising nutritional quality. Thus, a drum dryer was chosen due to its suitability for thermosensitive nutrients, cost advantages, and technical efficiency (Havlík and Dlouhý, 2020). The dried SCP was cooled with cooling water to bring down the exit temperature to ambient temperature. ...
... Considering design guidelines regarding the thermal-hygrometric aspects of rotary drum dryers, the classic ones proposed by Perry et al. (2019) [13] are well known, based on equations of the thermal-hygrometric exchange, and simplified and integrated by empirical indications. Again, with regard to the design, computational methods based on finite element analysis have also recently been proposed [14][15][16]. These methods are very useful for analysing and verifying the thermal-hygrometric and fluid dynamic phenomena inside the rotary drum after the dimensions, flow rates, and temperatures have been set. ...
Rotary drum dryers operating in co-current mode are commonly used for drying food and feed in leaf form, reducing the damage caused by the high air temperatures typical of these dryers, as well as providing advantages including reduced drying times and increased energy efficiency. However, drying control to ensure a desirable product exit moisture content is strongly based on empirical practices, which are usually jealously guarded by producers and users, grounded in simplified mathematical modelling. To overcome these uncertainties, in this work, a more complete mathematical modelling approach, based on the solution of ordinary differential equations (ODEs), is developed. The ODEs describe the drying process in the drum dryer, where the air is continuously cooled and humidified as the product dries. The mathematical model developed was experimentally verified in a drum dryer by drying alfalfa, and the maximum relative error was found to be only 2.4%. Finally, a comparison between the complete model proposed here and a simplified model was conducted, using both for drying control to keep the product exit moisture content constant (i.e., at 0.111). The results indicated that the simplified model provided values of air inlet temperatures erroneously higher, up to +8.2%, with a consequent higher energy consumption, lower dried alfalfa quality, and a greater risk of fire, given that the product exit temperature was dangerously increased.
... Rotary dryers consume 15-30% less specific energy and have low maintenance costs [22]. Indirect biomass drying using a rotary dryer is better, with a smaller diameter, slimmer shape, and length [23]. ...
This research focuses on testing rotary dryers for the small-scale drying of cherry coffee, using hot air through the conversion of rice husk into thermal with a heat exchanger. Drying cherry coffee with a moisture content of 62% was dried using a rotary dryer and sun drying. Rotary dryer testing for mass variations of 10 kg, 15 kg, and 20 kg. During the drying process, rice husks are not added to the furnace. The results showed that the rotary drying temperature was higher than the sun drying. The final moisture content of sun drying was 13.14%; the average temperature was 29.44 °C for 16 days. The rotary dryer produces final moisture content of 10.71%, 10.45%, and 11.13%. The time required is 1440 min, 1680 min, and 1920 min, respectively. The fastest drying rate occurs at a mass of 10 kg. The highest drying efficiency occurs for a mass of 20 kg. The greater the mass affects the moisture content evaporation, so the drying efficiency is high. During the drying process, there is a decrease in efficiency because the energy absorbed by cherry coffee decreases as the moisture content decreases.
... A comparison of the penetration model with the discrete modelling was done in [27]. Recent articles on indirect drying of biomass can be found in [28][29][30]. ...
This paper focuses on biomass drying for the design and operation of an indirect dryer used in a biomass power plant. Indirect biomass drying is not as well described process as direct drying, especially when used for the preparation of biomass in energy processes, such as combustion or gasification. Therefore, it is necessary to choose a suitable model describing the drying process and evaluate its applicability for this purpose. The aim of this paper is to identify parameters that most significantly affect the indirect drying process of biomass for precise targeting of future experiments. For this purpose, the penetration model was chosen. The penetration model describes indirect drying through 21 parameters. To run a series of experiments focused on all parameters would be time consuming. Therefore, the easier way is to select the most important parameters through a sensitivity analysis, and then perform experiments focused only on the significant parameters The parameters evaluated as significant are the temperature of the heated wall, operating pressure in the drying chamber, surface coverage factor, emissivity of the heated wall, emissivity of the bed, diameter of the particle, and particle surface roughness. Due to the presumption of perfect mixing of the material being dried, stirrer speed is added into important parameters. Based on these findings, it will be possible to reduce the scope of experiments necessary to verify the applicability of the penetration model for the description of indirect biomass drying and the design of dryers for a practical use.
... On the basis of experimental results and past experience [33][34][35], the adoption of general fire prevention measures is recommended, i.e. the process should be conducted in such a way that the premises are dust-free. In order to limit dust accumulation inside the premises, a cleaning plan should be implemented at regular intervals, wet cleaning of the equipment or using EX-compliant vacuum cleaners for dust explosive areas should be carried out to avoid dust. ...
In this paper the explosive and fire properties of energy willow dust were experimentally determined before and after drying with superheated steam at temperatures of 120°C, 140°C, 160°C and 180°C. The conducted research has shown that the parameters of the operation of the installation of drying with superheated steam of the energy willow biomass have a decisive impact on the fire-explosive characteristics of the dust produced. The results indicate that the higher the drying temperature, the stronger the probability of ignition of the willow dust cloud, the faster the flame propagation and the higher the explosion intensity. Although the superheated steam drying installation for energy willow biomass is considered to be safe, the probability of occurrence of a fire or explosion events of the biomass dust-air mixture is likely.
... For indirect dryers, the main thermal resistance in the heat transfer process is between the wall and the surface of the bed of the drying material and the resistance across the bed of the drying material [14]. Assuming sufficient material mixing, there should also be similarity for different concepts and operating mode (batch or continuous) of indirect dryers [33]. ...
This article deals with the influence of the final drying degree of moist biomass used as fuel in a power or CHP plant on indirect dryer sizing. For a description of the drying process, experiments with wet bark containing approx. 50 wt% of water were carried out in a laboratory indirect dryer. A new parameter called drying effectivity was introduced, whose size varies according to the degree of biomass being dried. Its maximum value corresponds to the optimal biomass drying, when the relative size of the indirect dryer to evaporate the required mass of water from the biomass would be smallest. Based on the experimentally determined drying characteristics of wet bark, the optimal drying of 13 wt% of water content was evaluated. If the bark was dried to a lower water content, the required relative size and price of the dryer would increase. Similarly, drying a bark with water content above 31 wt% is not very advantageous because drying effectivity continues to increase rapidly at this stage, and the required relative size of the dryer therefore decreases.
... Such a need arose in order to determine the conditions of uniqueness and technological safety in the digital modeling of such chemical-technological objects and processes. Accordingly, to verify the methodology based on the model of the drying drum, an experimental stand was developed and constructed, as well as a methodology of experimental research [2][3][4][5]. ...
The article considers the experimental stand for studying the process of removing moisture from granular carbon black in a drying drum. The substantiation of the need for the development and construction of the experimental stand is made from the position of the need to verify the numerical calculation methodology. The description of the design of the experimental stand and the experimental research methodology are presented. The results of experimental researches and their analysis are presented. Based on the results of the research, a conclusion was made about the working capacity of the stand and the possibility of its use for verification of the methodology for theoretical researches of the process of drying granular carbon black.
