转筒干燥器容积计算方法的选择

通过对转筒干燥器设备容积两种不同计算方法的描述和比较,即蒸发强度计算法和容积传热系数计算法,说明这两种方法各自的优势和缺点。从而提出选择转筒干燥器设备容积计算方法的建议。     

气流旋转干燥器

1 旋风气流干燥器 旋风气流干燥器的干燥室结构以圆筒形居多,但也有锥形结构,锥形干燥室可使物料颗粒旋转速度由小到大,能达到强化干燥的目的. 旋风气流干燥器由内筒和外筒组成.外筒呈上大下小的锥形,物料从上部切线进入干燥器后,随热风向下部进行旋转运动,在干燥室内物料被干燥.到达底部后受气流夹带,粉体从内筒向上运动,经出料口排出.旋风气流干燥器的优点是使物料及热空气在干燥器内形成的转向降低了设备的高度,延长了物料在干燥器内的停留时间.     

磷肥转筒干燥器工艺计算的程序设计

<正> 转筒干燥器是磷肥、复合肥料工业最常用的主要设备。可以说,任何一种磷肥或复肥的生产,都离不开转筒干燥器。它经常用于原料和成品的干燥,以及成品的冷却。故合理的选择转筒干燥器,对于节省基建投资和经营费用(主要是电耗)都有很大的意义。通常,计算一台转筒干燥器约需30多个步骤,这对于一个熟练的工艺设计人员也少不了要花一天的时间;而使用本程序在 PC—1500电子计算机上演算,则只需3分钟。这不仅提高了工作效率,而且     

炭黑工艺研究与转筒干燥器工艺计算

本文介绍了较为成熟的碳黑生产工艺,并针对碳黑干燥工序常用的转筒干燥器的设计问题,阐述了工艺计算之前需要掌握的原始数据、工艺计算顺序和参数选择。     

煤的内热流化床干燥实验研究

在内热式流化床干燥器实验装置上完成了湿煤的干燥实验,验证了工艺可行性.通过调节干燥实验装置的干燥处理量,考察了流化床平均温度分别为83℃,89℃,102℃时的干燥强度、换热强度及耗热项等工艺特性.在较低的流化速度(0.37 m/s~0.41 m/s)和83℃~102℃的流化床平均温度范围内,实验装置可以稳定运行;以设计的最大干燥处理量114 kg/h运行时,流化床平均温度为83℃,干燥强度为76.5 kg/(m~2·h),蒸汽盘管的换热强度为4 172 W/m~2,干燥器平均传热系数为200W/(m~2·K),干燥煤中水分耗热比率为52%,加热流化风耗热比率和干燥器散热比率均为20%,加热物料耗热比率为8%.     

滚筒干燥器的应用

<正> 一、概述滚筒干燥器是用于溶液或糊状物料干燥的设备。对于中、小批量连续生产的化工产品。应用该设备是值得推荐的,其原因如下:1.滚筒干燥器是传导加热干燥器,热能用传导方式传递给物料,使物料中水分汽化,达到湿物料干燥的目的。废气用风机抽走,不用干燥介质,也无干燥介质带走的热量损失。同时,滚筒干燥器的散热面积较小,因此热损失也少。所以,滚筒干燥器汽化每公斤水分的热耗量为750～900大卡/公斤,而喷雾干燥为850～1200大卡/公斤;滚筒干燥器的热效率很     

内热式惰性粒子流化床中膏状物料干燥模型

通过对惰性粒子流化床中膏状物料干燥机理的分析,得到了干燥时间及单位面积床层水分汽化量的数学计算式,可对干燥器的性能进行预测。采用带浸没加热管的惰性粒子流化床对膏状钛白物料进行干燥中试研究,采用气流式喷嘴将膏状物料分散成200～400μm的小液滴喷洒在惰性粒子表面进行干燥,探索了适宜的干燥条件,测定和确定了最佳的干燥工艺参数、操作参数和设备参数。结果表明:该干燥工艺能强化床内传热传质,促进高黏性膏糊状物料很好地分散,床层温度分布均匀,干燥器的操作弹性大,热量消耗低,干燥强度高,传热系数可达300W·m-2·K-1以上。     

沸腾床干燥器的工艺特点及设计计算

介绍沸腾床干燥器的用途、工艺特点及沸腾床干燥器恒速干燥阶段底面积的计算，减速干燥阶段物料和气体的状态，物料在沸腾床中的停留时间等设计计算。卧式多室沸腾床干燥器结构特点易于操作，稳定性好，常用来干燥粒径为0．02-4mm的物料。     

直接加热转筒式干燥机设备选型计算

容积换热系数是决定回转圆筒干燥器载热体向物料传热的主要因素。在设计任务给定后,确定了设计所需的基本参数。进行了物料衡算和热量衡算,解决了需要消耗多少干燥介质和热量的问题。依据物料衡算和热量衡算的结果计算并确定了设备的规格参数。本文从容积换热系数入手,结合油页岩干燥的工程实例,对直接加热转筒式干燥机参数(筒体直径、长度)进行了理论设计计算。     

带浸没加热管的惰性粒子振动流化床干燥强度研究

采用带浸没加热管的惰性粒子振动流化床对（石灰）膏状物料干燥进行了实验研究。利用正交实验，考察了加料速率、振动条件、进气温度、进气速度、加热管功率等参数对干燥强度的影响，得出了计算干燥器干燥强度的关联式。结果表明，由于浸没加热管热量的引入，能显著增加干燥器的干燥能力，实验条件下干燥器干燥强度超过250kg·（m^3·h）^-1，干品湿含量可降至1．5％以下，质量能达到要求，相关数据可为膏状物料干燥器的设计和开发提供借鉴。     

粒状肥料专用回转式多筒烘干机

分析粒状钙镁磷肥采用传统单筒烘干机不能达到出口产品标准的原因,介绍将传统回转式单筒烘干机改造成回转式多筒烘干机的设备结构和使用效果。改造后的多筒烘干机可使颗粒肥产品粒度均匀,强度高,含水率低,成品率提高20~30百分点,特别适用于粒度1~5 mm产品的烘干。     

Modeling and Drying of Carton Packaging Waste in a Rotary Dryer

This research aims at modeling the rotary drying of carton packaging waste and analyzing the energy performance of the process. Drying data were obtained in a semi-pilot rotary dryer, 0.45 m diameter and 2.7 m rotating drum long, operating with an air velocity of 1 m/s and air inlet temperature of 90°C and 10 rpm. Under the operating conditions employed, the analysis of the data showed that the energy performance of the drying process increased from 5 to 75% as the inlet wet solid feed rate increased from 1.8 to 19 kg/h. In addition, at this latter wet-solid feed rate, the reduction of the air velocity in the dryer to 0.8 m/s also led to an increase in the performance of drying process from 80 to 94%. Furthermore, with a 95% confidence interval, the model used was adequate to predict the air and solid temperature as well as the air humidity and the solids moisture content.     

Influence of drum inlet air conditions on drying process in a domestic tumble dryer

This study examines how the inlet air temperature, relative humidity, and flow rate influence the textile drying process in an open cycle tumble dryer. An experimental setup was prepared by connecting a domestic tumble dryer to an external system for controlled heating, humidification, and transport of air. Experiments were conducted by drying cotton textiles (8?kg dry mass) at different air inlet conditions. On the basis of measured data, correlations for determination of the total drying time, the moisture evaporation rate during the constant drying rate, and the area-mass transfer coefficient were developed. The process in the drum was modeled by using an established moisture evaporation model, based on sorption isotherms. A commonly used and a recently reported sorption isotherm for cotton were used with the model. Agreement between calculated and measured drying curves was better in case of the commonly used sorption isotherm, but final moisture content was better predicted by the recently reported sorption isotherm.     

One-dimensional phosphate flash dryer model for design application

The present paper studies the design of a bench scale flash dryer for phosphate particles using a one-dimensional steady-state model. The model was based on the two-fluid theory considering momentum, heat, and mass transfer between the solid and gas phases for a dilute gas–solid suspension flow and for which solid interactions were neglected. The set of coupled nonlinear differential equations of the model was solved using a Runge–Kutta method. A sensitivity analysis for inlet air and solid velocity, air temperature and pressure, air and solid moisture content, and for tube diameter and length was performed to design phosphate bench scale flash dryer to reduce the solid moisture content from 18 to 2%. An analysis of the results enabled choosing the appropriate conditions for experiments of phosphate drying for a hot air stream inlet of 200°C, in a flash dryer of 1.7?m length and 0.2?m internal diameter.     

Effect of Humidity on NPK Fertilizer Drying

ABSTRACT

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

Effect of Humidity on NPK Fertilizer Drying

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

Mathematical Modeling the Drying of Poplar Wood Particles in a Closed-Loop Triple Pass Rotary Dryer

Closed-loop drying systems are an attractive alternative to conventional drying systems because they provide a wide range of potential advantages. Consequently, type of drying process is attracting increased interest. Rotary drying of wood particles can be assumed as an incorporated process involving fluid–solid interactions and simultaneous heat and mass transfer within and between the particles. Understanding these mechanisms during rotary drying processes may result in determination of the optimum drying parameters and improved dryer design. In this study, due to the complexity and nonlinearity of the momentum, heat, and mass transfer equations, a computerized mathematical model of a closed-loop triple-pass concurrent rotary dryer was developed to simulate the drying behavior of poplar wood particles within the dryer drums. Wood particle moisture content and temperature, drying air temperature, and drying air humidity ratio along the drums lengths can be simulated using this model. The model presented in this work has been shown to successfully predict the steady-state behavior of a concurrent rotary dryer and can be used to analyze the effects of various drying process parameters on the performance of the closed-loop triple-pass rotary dryer to determine the optimum drying parameters. The model was also used to simulate the performance of industrial closed-loop rotary dryers under various operating conditions.     

Dynamic modeling and control of soybean meal drying in a direct rotary dryer

This paper presents the analysis of the dynamic model and the application of Proportional, Integral and Derivative (PID) control in the soybean meal drying in a industrial direct rotary dryer by computational tests. Therefore, load disturbances as step, pseudorandom, and impulse were applied in the inlet speed and in the inlet moisture of soybean meal in the dryer. Later, the output responses for perturbations were investigated with control systems. The application of feedback PID control showed satisfactory results, returning expected output moisture. According to the Integral Square Error (ISE) the manipulated variables that showed better controllability were the inlet speed, when the perturbation was in the soybean meal inlet moisture; and the inlet temperature of drying air, when the perturbation was in the inlet speed of soybean meal. These results are coherent with literature and conclude that, the tuning feedback PID control keeps the output moisture of soybean meal inside the specifications with fast results.     

Effects of Drying Parameters on Heat Transfer during Drying of Fermented Ground Cassava in a Rotary Dryer

The effects of drying parameters on heat transfer during drying of fermented ground cassava in a rotary dryer were studied. The fermented ground cassava was dried in a bench-scale rotary dryer at different inlet air temperatures, inlet air velocities, relative humidities, feed rates, drum drive speeds, and feed drive speeds. It is shown that inlet air temperature, inlet air velocity, and feed rate have significant effects on the specific heat transfer coefficient and heat load in the material. Models that predict the specific heat transfer coefficient as a function of inlet air temperature and inlet air velocity and the heat load as a function of inlet air temperature, inlet air velocity, and feed rate are also presented. Predictions of the models are compared with experimental data and good agreement is obtained.     

Mechanism of Through Air Drying of Paper: Application in Hybrid Drying

During through air drying the internal sheet drying history develops as a succession of local moisture content profiles in the sheet thickness dimension. These profiles were determined by interrupting the through drying of 180 g/m² 6-ply sheets, then quickly delaminating and determining the moisture content of each 30 g/m² ply. On the through flow inlet side of the sheet, large moisture differences, about 0.4-0.6 kg/kg dry per 30 g/m² ply, develop and move into the interior of the sheet provided that local moisture content is in the range 0.45-1.75 kg/kg. On the through flow exit side, moisture gradients only become significant for moisture content below about 1.25 kg/kg. From the through flow exit side of the sheet much of the water is removed by diffusion to the flow entry side where most evaporation into the through flow occurs. The kinetics of through drying reflect the interaction between these two mechanisms, local evaporation into the through flow and thickness direction diffusion. The moisture diffusivity-moisture content relation controls this balance. In any combination with cylinder drying to give some kind of hybrid dryer, through drying should be at the dry end where air permeability is highest and cylinder drying rate is lowest.