Outlet Moisture Content Research Articles

Computational Fluid Dynamics Modelling of a Laboratory Spray Dry Scrubber for SO2 Removal in Flue Gas Desulphurisation—Effect of Drying Models

Spray dry scrubbing is widely used for SO2 abatement, but high removal efficiencies are required for economical operation. Whereas SO2 removal dependence on the drying rate has been investigated, available modelling work has not addressed the impact of selected drying models on the removal efficiency; instead, a single drying model is often assumed. In the present work, computational fluid dynamics is used to numerically model the SO2 removal in a laboratory-scale spray dry scrubber. The Euler–Lagrangian framework is used to simulate the multiphase interaction and two drying models are used: the widely used classical D2-law model and the mechanistic model. In addressing shortcomings from previous works, this study also provides a comprehensive model development and robust model validation with quantifiable metrics for goodness-of-fit, including R2. Also presented are key parameters associated with SO2-removal efficiency, including the exit product moisture content and droplet dynamics. The mechanistic model gave a better representation of the SO2-removal efficiency. The latter was found to be dependent on the inlet temperature, the calcium-to-sulphur and liquid-to-gas (L/G) ratios, with a high L/G ratio having the most significant impact on the removal efficiency, although resulting in a higher product outlet moisture content.

Enhancing prior-knowledge-based control with deep attention neural network for outlet moisture content of cut-tobacco

Monitoring and controlling the drying process is crucial, particularly for rotary dryers, to ensure optimal quality and efficiency. However, due to the process’s nonlinear behavior, delays, and input disturbances, achieving this can be quite challenging. Previous research has not adequately explored online forecasting for rotary dryer control in real production settings. To bridge this gap, our study focuses on tobacco drying in an actual plant and presents a novel online prediction model for moisture content. We conducted comparative experiments to validate the model’s practical application in production settings and demonstrate its effectiveness in enhancing drying control. Our approach, called MCTFormer, has proven to be scalable to high-dimensional problems. The results of our study indicate a 45% improvement in product quality through accurate prediction of outlet moisture content, better control over moisture levels, and reduced energy consumption.

Seasonal performance research of heat-source tower systems using different work materials

Abstract The heat-source tower system has been evaluated in an enthalpy difference laboratory. This study analyzes the seasonal performance under various operating situations and fluid quality. In the summer and fall seasons, water is used as the circulating fluid in the tower. In the spring and winter seasons, glycol solution is used as the circulating fluid. Some parameters of the heat-source tower (e.g. the temperature of the solution inlet and outlet, the flow rate of the solution inlet and outlet, the temperature of the air inlet and outlet, the inlet air volume and the moisture content of the inlet air) are considered and measured to obtain its heat transfer characteristics. The simulation model of heat-source tower is constructed based on the mechanism of heat and mass transfer. This model is validated by the experimental results. The heat exchange and latent heat exchange of the system are analyzed under different parameters, as well as the variation law of inlet and outlet temperature and moisture content differences. The results show that the system has solution moisture absorption during winter operation. However, for every 9000 m3/h increase in air volume, the rate of solution dilution decreases between 9 and 43%. The rate of solution dilution is reduced by 11–31% for every 1°C in addition to the inlet solution temperature. Meanwhile, the heat dissipation in summer is about 2.8 times of the heat dissipation in winter.

An adaptive optimization method toward batch-wise variable set point of outlet moisture content for the tobacco drying process

The tobacco drying process in the cigarette production has an important effect on the final product quality. Therefore, the intelligent control methods have been widely investigated to ensure the stability of tobacco’s outlet moisture content. The existing work mostly uses a relatively fixed set point of the outlet moisture content for different tobacco batches, which can lead to unforeseen product quality after several processes following the drying process and inaccessible amount of dehydration for the rotary dryer. Some tobacco moisture prediction methods have been studied recently while the relationship with the intelligent control methods remain largely unexplored. To deal with these issues, a novel method is proposed in this paper to identify the optimal set point of the drying outlet moisture content for each tobacco batch. An encoder-decoder model is first developed to forecast the post-drying moisture trajectory. Then, an adaptive filter with specially designed mechanisms and a confidence interval of the dehydration level are constructed to obtain the design constraints. Based on all above, a constrained optimization problem is formulated and solved by the genetic algorithm. Extensive experiments on 895 tobacco batches from a large cigarette factory are carried out, which involves both algorithmic evaluation and field test. It turns out that the proposed method achieves the superior performance and leads to an improvement of the product quality in real production.

Integrating phase change material in building envelopes combined with the earth-to-air heat exchanger for indoor thermal environment regulation

To utilize the combined effects of earth-to-air heat exchanger (EAHE) and phase change material (PCM) in indoor thermal environment regulation during summer, this study proposes a combination mode, i.e., EAHE–PCM. In this method, EAHE continuously provides cool air to indoor spaces. PCM integrated into building envelopes stores excess cold provided by EAHE at night and transfers it indoors across time. We performed two full-scale comparative experiments (EAHE–PCM combined operation mode and PCM alone operation mode) on typical summer days in hot-summer and cold-winter regions. The results showed that the maximum reduction in the EAHE outlet air temperature and moisture content reached 21.6 °C and 4.55 g/kg, respectively, inducing an average cooling capacity of approximately 1186.5 W. The use of EAHE decreased the time-averaged PCM internal temperature by 6.0 °C in 24 h compared to the PCM alone operation mode, thereby activating the phase change process of PCM between 19:54 and 9:45. Therefore, PCM can store excess cold provided by the EAHE via latent heat and transfer it to indoor air through the melting process, resulting in a 157 min lag in the PCM internal temperature rise. When the ambient air temperature varied between 26.3 and 45.2 °C, the EAHE–PCM combined operation mode decreased the time-averaged indoor air temperature by 6.6 °C compared to the PCM operation alone, which helped maintain the indoor air temperature within the comfort temperature range of 22–28 °C for 73% in 24 h, with a peak temperature of 30.6 °C.

Effect of surface wettability on air parameters and performance of indirect evaporative cooler in the presence of primary air condensation

The surface wettability in the wet channels is an important factor affecting the performance of the indirect evaporative cooler (IEC). However, in previous studies on surface wettability, little attention has been paid to air condensation. Therefore, this paper presents a mathematical model of plate type IEC focusing on the surface wettability in the wet channels and air condensation. Besides, a test bench was built to verify the reliability of the model. The effect of surface wettability on air parameters and performance of IEC unit was intensively studied. The results show that with the increase of wettability factor from 0.3 to 1, and the outlet temperature of primary air decreases from 23.4 °C to 21.6 °C. It is worth noting that the condensation behavior of primary air at the entrance is restrained. The outlet temperature of secondary air decreases from 23.6 °C to 22.3 °C, and the outlet moisture content of secondary air increases from 13.9 g/kg to 16.86 g/kg. Moreover, when wettability factor increases from 0.2 to 1, the enlargement coefficient, wet-bulb efficiency, dehumidification rate, total heat transfer and water consumption increase by 5.9%, 61%, 68%, 81.8% and 251% respectively.

Prediction of solids outlet moisture content in a continuous wall heated fluidised bed dryer for uniform and binary solid mixtures

Most of the industries perform drying of solids to enhance the durability of the product. The solid nature and available resources will play an important role in the selection of the dryer and there are more than a hundred types of dryers currently used in different industries. In the dryer, the heat to wet solids is supplied in different ways such as conduction, convection or in combination. The application of fluidisation phenomena to drying will have several advantages and disadvantages. The advantages are the drying rate is higher than most of the dryers, due to the high transfer rate of heat and mass and also applicable for various ranges of particle sizes. In the present study, ambient air is used instead of hot air and also the heat to wet solids is provided from the wall. The significance of conventional parameters and effect of the mixture of solids have been studied.

Prediction of solids outlet moisture content in a continuous wall heated fluidised bed dryer for uniform and binary solid mixtures

Prediction of solids outlet moisture content in a continuous wall heated fluidised bed dryer for uniform and binary solid mixtures

Field experiments on the cooling capability of earth-to-air heat exchangers in hot and humid climate

In this study, full-scale experiments were performed to investigate the cooling capability of earth-to-air heat exchangers in a hot and humid climate. Four pipes with different configuration parameters were employed; the variations in the air temperature, relative humidity, cooling capacity, coefficient of performance and the soil thermal response and recovery rate were investigated. The results demonstrate that although the temperature and moisture content of the inlet air vary from 21.5 to 41.2 °C and from 11.2 to 20.52 g/kg, respectively, the temperature and moisture content of the outlet air are relatively stable for all four pipes. For an earth-to-air heat exchanger with a 0.075 m diameter and 3 m depth, the maximum reductions in the air temperature and moisture content are approximately 22.13 °C and 7.41 g/kg, respectively. It is observed that increasing the buried depth and decreasing the pipe diameter contribute to decreasing both the outlet air temperature and moisture content. The air temperature decays exponentially along the pipe length and the air temperature reduction increases linearly with the inlet air temperature. Moreover, the time-averaged sensible cooling capacity of earth-to-air heat exchangers accounts for 60.5%–82.82%, whereas the time-averaged latent cooling capacity accounts for 17.18%–39.5% of the total cooling capacity. The maximum total cooling capacity and coefficient of performance occur in the earth-to-air heat exchanger with a 0.16 m diameter and 3 m depth; these are 2987.94 W and 31.79, respectively. Further, the thermal recovery rates of the soil temperature are lower than the corresponding response rates.

Dead Band Zone Model Predictive Control of Cut Tobacco Drying Process

In this article, an L1-Norm model predictive controller with a dead band zone is proposed for the cut tobacco drum dryer system. The control objective is to make the drum dryer temperature, hot air temperature and cut tobacco outlet temperature meet the process constraints, and optimize the outlet moisture content of the cut tobacco. First, the cut tobacco drum dryer system is introduced, and the nonlinear open equation model is established. Then an L1-Norm moving horizon estimator (MHE) is designed to provide state and parameter estimation for the controller by using its ability to deal with nonlinearity and constraints. A model predictive control (L1-Norm zone MPC) for L1-Norm target tracking with a dead band zone is proposed for the cut tobacco drum dryer system. The simulation results show that the proposed L1-Norm zone MPC (L1-ZMPC) better-tracking performance and the controller's minimum action economic characteristics compared with the traditional setpoint tracking model predictive control.

Evaluation of soil moisture prediction for Gopalkheda sub-catchment, India

ABSTRACT In present study, station-based daily rainfall data and gridded rainfall (0.25° × 0.25°) from India Meteorological Department (IMD) with lumped soil parameters have been used to simulate the soil moisture content within top 90-cm vertical soil profile at an interval depth of 15 cm using 1D numerical unsaturated flow module of coupled MIKE SHE/MIKE 11 for the Gopalkheda sub-catchment, India. The unsaturated flow parameters have been calibrated for the years 1991–1998 and validated for the years 1999–2004. The model has simulated stream flow at sub-catchment outlet and soil moisture content in the sub-catchment using both station-based rainfall and gridded rainfall datasets. The simulated results are compared with observed stream flows and available soil moisture data using statistical performance indices, i.e. Nash-Sutcliffe Efficiency (NSE), Root mean square error (RMSE), coefficient of determination (R 2). The results of calibrated model indicated that performance of hydrological model is highly dependent on nature of rainfall inputs into the model. The overall analysis indicated that gridded rainfall data are promising for stream flow and soil moisture predictions within the sub-catchment. The application of distributed hydrological model would be significant to water resource planner and agronomist in monitoring the water availability and soil moisture within their response sub-catchment.

Energy and exergy efficiencies as design criteria for grain dryers

ABSTRACTWe devised a novel methodology for optimizing cereal grain dryers grounded on the transient spatial–temporal first and second laws of thermodynamics and associated balance equations. Model equations were solved using a special time-adaptive radial basis function. Comprehensive sensitivity tests show the quantitative effects of initial moisture content, air velocity, and drying air temperature on the temporal profiles of outlet air temperature and moisture content and temporally integrated energy and exergy efficiencies. Drying temperature is the most efficacious parameter in the drying range of 50–90°C. Finally, selected examples show optimized dryer operation points under unrestrained and restrained conditions. Second law efficiency is well suited for expressing drying performance, portraying time, noble energy expenditure, and intrinsic sustainability. Three decision tables, based on simulation results, can be used to define dryer design under normal technical choice. First law efficiency and the specific moisture extraction rate are concepts more adequate for designing in-bin low-temperature dryers. Second law efficiency is indicated when exergy recuperation is at stake: higher drying temperatures, shorter drying times, recirculation drying, and other processes.

Modeling and simulation of drying characteristics on flexible filamentous particles in rotary dryers

Experiments were conducted to demonstrate the effects of the drum wall temperature on the heat and mass transfer in rotary dryers. The drying characteristics of flexible filamentous particles in rotary dryers were further explored. In addition, the inlet and outlet temperatures and moisture contents of granular particles were measured. As a result, the good agreement between the simulations and experiments verified the rationale and feasibility of the numerical method. Therefore, the approach was adopted to evaluate the temperature and moisture content of wet granular particles in a rotary dryer in different conditions, for instance, drum wall temperature and rotational speed. The results revealed that the higher drum wall temperature led to hotter particles with lower outlet moisture content. Conversely, the higher rotational speed resulted in cooler particles with higher outlet moisture content due to the decrease of residence time in the rotary dryer.

Drying Characteristics of Fine-Particle Lignite in Paddle Dryers

Drying is an important way to improve the quality of lignite with high moisture. In this paper, a single-shaft paddle dryer experimental system was built to investigate the drying characteristics of fine-particle lignite with diameter 0-5mm. The experimental results show that with the increasing in shaft rotation speed the flow rate of lignite increases linearly approximately and the residence time decreases correspondingly. Increasing the inclination angle of dryer frame helps increase the flow rate. Both shaft rotation speed and heating source (heat transfer oil) temperature have significant effects on outlet moisture content of lignite. Shaft rotation speed affects the average heat transfer coefficient greatly and heating source temperature affects it weakly for specified conditions. It is found that for 5-12mm coarse-particle lignite, flow is not smooth and the average heat transfer coefficient is much less than that of fine-particle lignite. This research shows that it is feasible technically to dry fine-particle lignite by using paddle dryers, but not suitable to dry coarse-particle lignite.

Modeling and Simulation of a Co-current Rotary Dryer

Abstract Mathematical models including mass and energy conservation were developed in order to predict the outlet particles temperature and moisture. As the inlet air temperature increased, the outlet particles temperature increased as well and the outlet particles moisture decreased quickly. The outlet particles temperature and moisture changed a little as a function of the speed of rotation at the low inlet air temperature, while the outlet particles temperature and moisture increased very apparently with the speed of rotation increased at the high inlet air temperature. The error of the simulation results compared to the experimental data showed good accuracy for particles temperature and moisture content. The mathematical model performs well to predict the outlet particles temperature and moisture content.

Superheated steam drying of sawdust in continuous feed spouted beds – A design perspective

Spouted bed drying technology shows promising results for the drying of unscreened sawdust in superheated steam. In this paper, the experiences from designing, running and evaluating two spouted bed continuous feed dryers are presented. Stable running conditions and drying results have been achieved. This has been particularly important for sawdust that will be compressed into pellets or briquettes. The spouted bed superheated steam dryer also shows high potential for energy efficient integration into sawmills. Our recommendation is thus, to use the outlet steam temperature as the control parameter for the outlet moisture content. A drying rate above and one below the fibre saturation level, can be identified. Visual observations through the viewing glass in the drying zone in both the dryers clearly showed that not all of the material participated in the spout at all times; there were, however, no indications of dead zones. A heat transfer analysis indicated that only about 70% of the surface area of the material was in thermal contact with the steam. This paper sums up the experiences regarding drying properties, control and system properties obtained when sawdust is dried using superheated steam as the drying medium. Further work on standardised dryers in series or in parallel is necessary to increase the capacity in the spouted bed dryer.

Optimization of the spray drying of a Paenibacillus polymyxa-based biopesticide on pilot plant and production scales

Spore survival and moisture content are two important properties of biopesticides, and both are related to field biocontrol efficacy and storage shelf life. In this study, Paenibacillus polymyxa (HY96-2) was spray-dried on both pilot plant and production scales, and the effects of inlet and outlet temperatures on spore survival and moisture content were investigated. The results showed that inlet temperatures ranging from 170 to 230 °C (at an outlet temperature of 80 °C) had no obvious effect on the two properties during pilot scale processing, although an inlet temperature of 230 °C resulted in higher feed speed. When the outlet temperature on the pilot scale was reduced from 100 to 80 °C, no obvious variations in spore survival and moisture content were found, while a further reduction from 80 to 65 °C resulted in a decline in spore survival from 81.0 to 67.0% and an increase in moisture content from 2.3 to 31.7%. These results indicate that both outlet temperature and moisture content have an effect on spore survival. Optimum inlet and outlet temperatures for P. polymyxa processing were 230 °C and 85–90 °C on a production scale. Under these conditions, spore survival and moisture content were 83.5–86.6% and 2.73––4.12%, respectively.

Mathematical modeling and simulation of an industrial rotary dryer: A case study of ammonium nitrate plant

Drying of solids is of great significance in fertilizer industry as the quality of final product should meet the commercial required standards. A rotary dryer which has been investigated in the present study is used in ammonium nitrate (AN) plant located at Shiraz Petrochemical Complex (SPC). This plant is designed to produce 650 metric tons of final products in a day. In this work, mathematical modeling of the concurrent rotary dryer for AN including heat and mass transfer equations between solid and air was developed. New correlations were proposed for AN equilibrium moisture and drying rate which were used in the modeling. The model was checked against the industrial data which showed a good agreement. The model predicts air and product moisture and temperature depending on working conditions of the rotary dryer. Regardless of the slope and speed of the dryer, inlet AN moisture and air temperature have been shown to be the variables that have the greatest effect, on the outlet moisture content of the product.

Sewage Sludge Flow and Drying Characteristics in Paddle Dryers

Sewage sludge from wastewater treatment is being more and more produced in many countries. For sewage sludge disposal, drying operation is usually required and greatly energy-consuming. Paddle dryers, one kind of indirect dryers, are widely used in removing moisture of sewage sludge recently, but the design, to some extent, still depends on empirical and limited data. In this paper, we presented preliminary experimental results of sewage sludge drying based on a 3 m2 paddle dryer prototype. The effects of thermal oil inlet temperature on outlet moisture content and mass flowrate of initial sludge are recorded and analyzed. A simple monotonic relation between mass flowrate of initial sludge and thermal oil inlet temperature does not exist. Besides, we performed the drying experiment of adding low-value biomass (rice husk) into wet sewage sludge. The results show that the drying performance is improved significantly.

Experiments, Modeling and Control of a Dryer–Cooler of Expanded Raw Soybean Flakes in a Hexane Extraction Plant

AbstractDrying and cooling are preparatory operations typically applied in the soybean processing industry to reduce the moisture content and temperature of the flakes fed to the extractor. Although these parameters are important for a safe and optimal process of extraction, limited or even inexistent schemes for their control are available. To deal with this problem, the current investigation suggests the use of a PID controller to manipulate the speed of the conveyor belt in order to keep the temperature of the flakes in the discharge of the dryer–cooler close to 61 °C without exceeding the acceptable outlet moisture content range from 9.9 to 12.3 % dry basis (d.b.). Closed‐loop responses for the controlled variables when considering simultaneous arbitrary disturbances on operating conditions confirmed the reliability of the current control strategy. A dynamic model represented by a system of two partial differential equations obtained by energy and mass balances for the solute in the bed was used as a virtual conveyor‐belt dryer‐cooler. Its consistency was checked by a comparison between experimental and calculated results for moisture content and temperature at the exit of a size‐scale dryer–cooler of soybean flakes at typical industrial operating conditions. The ISE technique and the simplex method of optimization were used to tune the set of PID parameters in which process control was stable.