Outlet Moisture 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.

Structural Integrity Assessment and Fatigue Evaluation of Feed Water Nozzle of 700MWe PHWR Steam Generator

Steam Generator (SG) is a prime component in Indian Pressurized Heavy Water Reactors (PHWRs). The Steam Generator consists of an inverted vertical U-tube bundle in shell for primary flow (Heavy water). The shell side is designed for recirculation. Steam Generator is a Safety Class-1 component and designed & fabricated as per the requirements of ASME Section III, Subsection-NB.Secondary side of the steam generator consists of a shell, Feed Water Nozzle (FWN), Steam Outlet Nozzle, moisture separator, drier, tubes and shroud. The principal material of construction for secondary side pressure boundary is of low alloy carbon steel. Secondary side of steam generator is subjected various loadings (Dead weight, pressure, pipe reactions & thermal) during normal plant condition as well as transient conditions including severe transient like crash cool down where in the thermal gradients are much higher. To take care of these thermal transient loadings a special thermal sleeve type of design has been incorporated in the FWN.As mentioned above, FWN is subjected to thermal transients throughout its life and susceptible to high thermal gradient which makes it important to evaluate for structural integrity and fatigue failure. This paper covers the approach & results for structural integrity assessment (stress evaluation) and fatigue evaluation (cumulative fatigue damage factor) of Feed Water Nozzle of 700MWe PHWR SG for various Service levels A, B, D & Design. These service conditions comprise of thermal & pressure transients during operating and accidental conditions. Detailed integrity check performed for all conditions by stress categorization at critical locations and qualify primary & secondary stresses against ASME Section III allowable.

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.

Multi-objective predictive control based on the cutting tobacco outlet moisture priority

In this paper, we propose a new priority multi-objective optimization strategy of system output variables in cutting tobacco process. The proposed strategy focuses on the cutting tobacco moisture-controlled output variables optimization in feasible regions with two levels according to the priority. This study aims to provide a novel technical support for the chemical industry contained drying process. In order to alleviate the lack of degree of freedom of the system, strict set-point control is given, meanwhile, other output variables adopt zone control. Firstly, the system control output variables are optimized in ascending order of priority. Secondly, the specific lower-level target constraints are first relaxed. Finally, the relaxation of other high-priority target constraints is stopped when the optimization is feasible. Thus, the system control output variables move along the optimal target trajectory. From the perspective of practical application of engineering, under the condition of disturbance existing in the cutting tobacco drying process, the simulation shows that the proposed approach has good robustness when there is disturbance, and the previous method cannot meet the control requirement. The proposed strategy meanwhile has better tracking effect through single and multiple output variables simulation, which compared with traditional predictive control in real cutting tobacco drying process.

The Tobacco Leaf Redrying Process Parameter Optimization Based on IPSO Hybrid Adaptive Penalty Function

In the tobacco redrying process, process parameter settings are greatly influenced by ambient temperature and humidity, and the moisture content of the tobacco leaf. In the face of complex and variable tobacco leaf characteristics, it is difficult to accurately adapt the process parameters to fluctuations in the incoming material characteristics by manual experience alone. Therefore, an improved optimization method combining an improved particle swarm optimization algorithm (IPSO) and an adaptive penalty function is proposed, which can adaptively recommend the best combination of process parameters according to the dynamic incoming characteristics of the tobacco leaf, to reduce the deviation in the outlet moisture and temperature of the roaster under different processing standards of the tobacco leaf. Firstly, the Radial Basis Function (RBF) Neural Network is used to fit the relationship between process parameters and roaster exit moisture content and temperature. Then, taking the standard tobacco leaf redrying export quality as the optimization goal, the optimization algorithm is used to search for the optimal solution. From the high-dimensional nature of the process operating conditions, the difficulty of this study lies in searching for the optimal solution under complex nonlinear constraints of multiple processes. To improve the convergence speed and accuracy of the searching algorithm, the position update method of the particle swarm optimization algorithm is improved, and the adaptive penalty function is combined to search for the optimal global solution to the optimization problem. Redrying experiments are conducted using the method proposed in this paper. Compared with the manual regulation of outlet moisture and temperature, the fluctuation range values are reduced by 7.5% and 11.8%, respectively, which has good application prospects and promotion value.

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.

Study of Aramid Yarns Sizing.

The process and efficiency of sizing aramid yarns before the weaving process was studied. The sizing was carried out under different conditions, with and without the pre-wetting of the threads before the actual sizing process. Two groups of yarns were tested. The first group consisted of five yarn samples that were blended with 95% meta-aramid and 5% para-aramid in counts of 20 × 2, 17 × 2, 14 × 2 and 12.5 × 2 tex. The second group of yarns consisted of three yarn samples that were blended with 93% meta-aramid, 5% para-aramid and 2% carbon in counts of 20, 20 × 2 and 17 × 2 tex. The inlet moisture of the yarn before sizing was 40% (with pre-wetting) and 4% (without pre-wetting), and the outlet moisture after drying was 4%. In order to carry out such tests to reproduce them, the sizing was carried out on a laboratory-sizing machine with the possibility of adapting to industrial conditions. According to the obtained results related to the properties of yarn before and after sizing, it can be concluded that sizing of aramid yarns is justified. When sizing the yarn without pre-wetting, the mechanical properties improved, especially breaking force, strength and abrasion resistance. Irregularity and hairiness were also reduced, especially when sizing with pre-wetting. Yarn hairiness or the frequency of protruding fibres also decreased with sizing in almost all samples and sizing conditions. The second group of yarns with a carbon fibre content mostly showed better mechanical properties before sizing, which continued after sizing. In general, the aramid yarn sized with pre-wetting showed certain deformations caused by stretching in the wet state and thus reduced the size pick-up, which caused less breaking forces and strength. Sizing with pre-wetting resulted in a slightly better smoothness of the thread and its higher evenness. It can be concluded that the aramid yarn should be sized with a lower size percentage (up to 4.5%), i.e., without pre-wetting in order to minimise the deformation of the yarn during sizing and thus improve the mechanical properties in the weaving process.

The added water control system based on neural network model and double parameter corrected for loosening and conditioning cylinder

In order to improve the stability of outlet moisture in the of loosening and conditioning cylinder, we concentrate on loosening and conditioning cylinder, and design the prediction model of the added water volume based on neural network technology and the double parameter corrected control system of material balance and moisture deviation for loosening and conditioning cylinder by using historical production data. Taking the set value of inlet and outlet moisture of the loosening and conditioning cylinder as the input factor and the added water volume as the output factor, the prediction model of the added water volume was to predict the total volume of the added water. When there was a big deviation between the actual value and the set value of outlet moisture, the double parameter corrected control system of material balance and moisture deviation was used to correct the deviation, so as to improve the outlet moisture stability and the control accuracy of the added water volume. Using Cigarette brand “diamond (hard-case Yingbin)” produced by Zhangjiakou cigarette factory to built model and analysis, the results showed that after the improvement, the standard deviation of output moisture of loosening and conditioning cylinder reduced by 0.27%, and the control stability and the control level of production process were improved.

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.

SHETRAN and HEC HMS Model Evaluation for Runoff and Soil Moisture Simulation in the Jičinka River Catchment (Czech Republic)

Due to the improvement of computation power, in recent decades considerable progress has been made in the development of complex hydrological models. On the other hand, simple conceptual models have also been advanced. Previous studies on rainfall–runoff models have shown that model performance depends very much on the model structure. The purpose of this study is to determine whether the use of a complex hydrological model leads to more accurate results or not and to analyze whether some model structures are more efficient than others. Different configurations of the two models of different complexity, the Système Hydrologique Européen TRANsport (SHETRAN) and Hydrologic Modeling System (HEC-HMS), were compared and evaluated in simulating flash flood runoff for the small (75.9 km2) Jičinka River catchment in the Czech Republic. The two models were compared with respect to runoff simulations at the catchment outlet and soil moisture simulations within the catchment. The results indicate that the more complex SHETRAN model outperforms the simpler HEC HMS model in case of runoff, but not for soil moisture. It can be concluded that the models with higher complexity do not necessarily provide better model performance, and that the reliability of hydrological model simulations can vary depending on the hydrological variable under consideration.

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.

A comprehensive analysis of critical variables used to design a spray dryer of whey protein concentrates

Five models of a spray dryer design for a whey protein process were analyzed in this study. These models include first principle approaches and empirical correlations. From a large set of given design specifications (inlet and outlet moisture contents, inlet air conditions and residence time), the physical size of the spray drying system was determined from their correlations. Then, the designs were compared to both industry heuristics for size ratios and dryer performance (when possible) to assess the validity of these models. Specific consideration was given to the correlation between the systems that met design heuristics and those that produced a usable product.

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.

State-space thermodynamic modeling of vanilla ethanolic extract spray drying with heat pump and [formula omitted

State-space thermodynamic modeling of vanilla ethanolic extracts spray drying with heat pump and N2 was developed. Thermodynamic modeling considers activity coefficients for Raoult law deviations of ethanol vapor pressure, water vapor pressure, ethanol evaporation latent heat and water evaporation latent heat in a N2-ethanol-water-vanilla solids system. State space considers 12 ordinary differential equations (ODEs) for ethanol and water concentrations in solid, N2 and condensed liquid; temperatures and condensed liquid rate. The model was validated with 32 treatments of vanilla ethanolic extract experimentally spray dried with heat pump and N2. The mathematical model reproduced the experimental gas outlet temperature with 4% of averaged error. An additional two parameters fit reached 11.4% of averaged error with respect to product outlet moisture and gas outlet temperature simultaneously. Proposed model demonstrated that heat pump spray drying can reach a 58% of thermal efficiency and a conventional spray drying can reach only 30%.

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.