摘要:

Any nonuniformity in local moisture content of paper which develops during drying because of locally nonuniform drying rates provides a driving force for in-plane diffusion of moisture, which in turn acts to reduce this moisture nonuniformity. As no data have appeared for the in-plane diffusivity of moisture during desorption from paper over the range of conditions existing during papermachine drying, an investigation was undertaken to obtain this information.

ISSN:0737-3937    

DOI:10.1080/07373939708917234

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Through drying of paper of basis weight 25 to 50 g/m2was studied through 89 experiments with 22 to 90°C air at mass flow rates from 0.125 to 1.45 kg/m2s. The complete drying rate curves are represented with five quantitative parameters:moisture contents at the end of the increasing and constant rate periods, the constant drying rate, and exponents for the increasing and falling rate period relations. The constant drying rate period disappears at higher drying intensities leaving the increasing rate period accounting for as much as 37% of the drying. The constant drying rate may be controlled by thermodynamics or by transport phenomena. The critical moisture content depends on effects from the intrinsic local nonuniformity of through drying as well as on sheet average conditions. A universal set of relations was obtained for representation of the complete drying rate curve and was verified for prediction of drying rate and drying time. Through drying rates cannot be increased significantly by providing the drying air as an impingement flow.

ISSN:0737-3937    

DOI:10.1080/07373939708917235

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

For this combined drying process the fundamental characteristics were determined using a unique facility in which air convection drying of paper could be investigated over the full range from pure impingement to pure through drying. As well as light weight paper the program tested heavier sheets, of printing paper grammage, which are not currenfly dried industrially by either impingement air or through air drying.

ISSN:0737-3937    

DOI:10.1080/07373939708917236

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Printing and heavier grades paper are dried over steam heated cylinder dryers, a mature process which is characterized by low drying rates and lack of ability for control of moisture uniformity across the sheet. The present study examines factors relating to the applicability of through air drying for such grades of paper. This drying process yields much higher drying rates but now is restricted to high permeability, light weight products such as tissue and toweling as the cost of providing through flow across the sheet is the key economic factor in this technique. With over 400 through drying experiments the parameters characterizing the drying rate curves were determined for 10 quite different types of uncalendered paper produced on a variety of papermachines.

ISSN:0737-3937    

DOI:10.1080/07373939708917237

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Possible extension of industrial practice of through drying from its current use for drying light weight grades such as tissue papers requires knowledge of the effect of papermaking parameters. As these effects interact and the variables occur in only limited combinations for machine-produced paper, these effects cannot be extracted directly from measurements with papermachine sheets. Therefore the effects on through drying characteristics of important parameters in commercial papermaking such as beating. bleaching, wet pressing and formation were examined through experiments with handsheets.

ISSN:0737-3937    

DOI:10.1080/07373939708917238

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Results from three experimental studies are reviewed in order to examine the relationship between the heat and mass transfer coefficients in the combined infrared and convective drying process. These results demonstrared that the heat

ISSN:0737-3937    

DOI:10.1080/07373939708917239

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Drying of dielectric resin coatings is accompanied simultaneously by evaporation of multicomponent solvents and polycondensation from monomers. The characteristic of the drying is studied experimentally. As a test sample, a vanish consisting of trimellitic acid anhydride and 4.41-diphenylmethane diisocyanate dissolved in the mixture of N-methylpyrrolidone and xylene is coated on an aluminum pan. The sample is subjected in drying in two types of dryers: hot air heating and radiation heating. The constant drying rate period is not observed in any run. The maximum drying rate of the sample is lower than the evaporation rate from the solvent layer with no resin. There are remarkable fluctuations in the drying rate in the decreasing drying rate period. The fluctuations are caused by bubble formation. The progress of the reaction can be followed by IR spectroscopic analysis. From these results it is suggested that removal of the solvent and the product is inhibited by the formation of a polymer skin on the surface and it makes control of drying difficult.

ISSN:0737-3937    

DOI:10.1080/07373939708917240

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper presents an Overview of particulate medium drying and heat treating of cereal grains. While the conventional air drying of grains is well documented, studies on the drying of grains using heated granular medium do not appear to exist. The scientific study of the different aspects of drying with a heated granular medium began in the early 1970's. Progress on the utilization of particle-to-particle heat transfer was slow as evidenced by the fact that there is no commercial dryer using the method as of today.

ISSN:0737-3937    

DOI:10.1080/07373939708917241

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper presentS an overview of particulate medium dryers developed to evaluate the drying of grains using heated particulate media. Components of particulate medium heating and drying equipments as well as the devices employed to conduct the materials through the machine are described. How these components accomplish the basic processes involved in conduction/particulate medium heating is also explained.

ISSN:0737-3937    

DOI:10.1080/07373939708917242

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Rotary dryers are widely used for the continuous drying of minerals and chemicals on a large scale. Hot gases are passed parallel to the flowing solid to achieve the desired product moisture content. Because these dryers are energy intensive, it is mandatory to operate them as efficiently as possible to respond to economic pressures. Using a dynamic rotary dryer simulator for mineral concentrate, five control strategies are evaluated and compared. Two control strategies are based on PI controllers and the others use neural network models. Results clearly show that a feedforward action, in conjunction with a PI controller or incorporated within the structure of a neural network model, led to the best performances provided an accurate measurement of the feed moisture content is available.

ISSN:0737-3937    

DOI:10.1080/07373939708917243

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor