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The pyrolysis of corn stalk was performed with thermogravimetry (TG), and its liquefaction was investigated in a semicontinuous apparatus with a nonisothermal fluid extraction technique, both with and without sodium carbonate (Na2CO3) as a catalyst. The results indicated that the main pyrolysis region of corn stalk is similar to500-650 K and the maximum rate occurs at similar to600 K on the differential thermogravimetry (DTG) curve. The presence of a catalyst has an obvious effect on the pyrolysis, especially in the temperature range of 550-650 K. When more than 1.0 wt \% of catalyst was added, the DTG curve is altered greatly, from two peaks to one, for the catalyst, which has a greater effect on hemicellulose than on cellulose and lignin. Kinetic analysis shows that the activation energy in the main pyrolysis range (10-70 wt \%) varies with different amounts of catalyst addition. The liquefaction conversion of corn stalk with 3 mL/min of water as a solvent at a pressure of 25 MPa, with or without the addition of 1.0 wt \% of Na2CO3, is up to 95.7 and 95.4 wt \%, respectively. The catalyst mainly improved the yield of bio-oil, from 33.4\% without a catalyst, increasing to 47.2\% with 1.0 wt \% of Na2CO3. The catalyst has a positive effect on the liquefaction at relatively higher temperatures and can increase the yield of liquid product, as well as improve the quality of liquid product. More bio-oil and less gas can be obtained with a catalyst than that without a catalyst. A two-stage main reaction may occur for both the pyrolysis and liquefaction of corn stalk under the experimental conditions.

Drying is the last operation for processing most biomaterials. Due to the heat and moisture sensitivity of biomaterials, selections of drying methods and operating parameters are very important to keep the viability of these materials. In the present study, experiments were carried out in fluidized bed drying of photosynthetic microorganism liquid and mixed culture animal food. Results show that most activities can be kept in dried products. Appropriate operation parameters were determined.

A photoelectrochemical process in the degradation of an azodye (Acid Orange II) on a Pt/TiO2 film electrode was investigated. By using the glass device and the voltage stabilized source of direct current, decolorization ratios higher than 78\% were observed during a period of 5h. Comparing this value with the sum of the decolorization ratios obtained by a sole application of electrochemical (lower than 3\%) and photochemical (about 23\%) procedures, a significant synergic effect between both processes was observed. The effects of adscititious voltage and pH value on the decolorization ratios were obvious while the effect of the amount of aeration was minor.

The oily sludge generated from the pretreatment step of the used lubricating oil re-refinery is characterized as a complex and tight water/oil emulsion with water content varying from 38 to 77 wt.\%. Removal of water is necessary for the emulsion to be fed into the processing line. Freeze/thaw method proves to be effective, with near 90\% of water removed. An optimal freezing temperature was found to be around the point where water droplets were all frozen, about -40 degreesC in this case. Sufficient freezing time is required for the removal of water to reach its maximum value. The best thawing conditions found are either in ambient air or in water bath at a temperature below 20 degreesC. The water separated from the emulsion contains some organic chemicals with chemical oxygen demand (COD) being 10 000-15 000 mg/l. The demulsification is achieved due to the expelling of surfactant molecules from the ice lattices during freezing and the forming of surfactant micells during thawing. (C) 2002 Elsevier Science B.V. All rights reserved.

The structure, physical characteristics and photocatalytic selective oxidation properties of nanometer-size TiO2 particles produced by a sol-gel method were studied by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and photocatalytic selective oxidation measurements. Analysis of the XRD results shows that sol-gel-produced TiO2 nanoparticles have the anatase structure at annealing temperatures less than or equal to973 K, that the rutile structure begins to emerge at annealing temperatures greater than or equal to973 K and the particles have the pure rutile structure at 1023 K. DRS indicates that the obtained TiO2 nanoparticles exhibit a blue shift with decreasing crystallite size. Analysis of the XPS results shows that the TiO2 nanoparticles have a lot of oxygen vacancies. The EPR spectrum of TiO2 at 77 K is composed of a strong isotropic EPR Surface-Ti3+ signal(l) at g = 1.926 and a weak broad Bulk-Ti3+ signal (11) at g = 1.987. Quantitative EPR indicates that both signals show a size and temperature dependence. Photocatalytic oxidation of cyclohexane into cyclohexanol with high selectivity and activity has been obtained by activation of molecular oxygen over sol-gel-produced TiO2 nanoparticles under mild conditions in dry solvent, which reveals that the quantum size effect and surface state effect of nanoparticles are key points for governing the selective photocatalytic reaction. The photocatalytic oxidation mechanism under dry solvent is different from that in aqueous solutions. (C) 2003 Society of Chemical Industry.

The dielectric material assisted microwave freeze-drying was investigated theoretically in this study. A coupled heat and mass transfer model was developed considering distributions of the temperature, ice saturation and vapor mass concentration inside the material being dried, as well as the vapor sublimation-desublimation in the frozen region. The effects of temperature and saturation on the effective conductivities were analyzed based on heat and mass flux equations. The model was solved numerically by the variable time-step finite-deference technique with two movable boundaries in an initially unsaturated porous sphere frozen from an aqueous solution of mannitol. The sintered silicon carbide (SiC) was selected as the dielectric material. The results show that dielectric material can significantly enhance microwave freeze-drying process. For case of the dielectric field strength, E=400OV/m under typical operating conditions, the drying time is 2081s, 30.1\% shorter and 47.2\% longer, respectively, than those for E = 2000V/m and E = 6000 V/m. The heat and mass transfer mechanisms during the drying process were discussed.

The salinity effect on electro-osmosis dewatering was investigated by measuring the solid content of sludge after dewatering. Three levels of salinity were studied, 5,000, 10,000, and 12,500 ppm. Coagulant chemicals such as alum, ferrous sulfate, and organic polyelectrolytes were used for some tests. Increasing the salinity from 5,000 to 10,000 ppm and 10,000 to 12,500 ppm was found to increase the sludge solid content about 88 and 28\%, respectively. A 2 V/cm increase in voltage intensity can also increase the solid content about 46\%. The effect of chemicals is evident at low salinity. At 5,000 and 10,000 ppm, addition of chemicals in average can enhance the sludge solid content about 44 and 16\%, respectively. Because of the electrolysis of salt solution and the release of chlorine gas, the pH of the sludge increased. Consequently the zeta potential of the sludge increased, which in turn results in an increase in dewatering rate. Therefore an S-shape solid content-time curve was observed for most of the operating conditions, contrary to the conventional shape of a linear increase followed with a decrease of rate before reaching zero rate.

Reductive dechlorination rate constants for five chlorobenzenes in the presence of Pd/Fe as catalyst were determined experimentally. Linear free energy relationships (LFER) for the dechlorination rate constants of five chlorobenzenes and three chlorophenols were developed by partial least squares (PLS) regression based on quantum chemical parameters computed by PM3 Hamiltonian. The optimal LFER model obtained is log k = -1.63 + 1.46 x 10(-3) DeltaH(f) - 7.69 x 10(-1) E-LUMO where k stands for the dechlorination rate constants, DeltaHf is the standard heat of formation, and ELUMO is the energy of the lowest unoccupied molecular orbital. The Q(cum)(2) value of the model is 0.879, indicating good robustness and predictive power of the model. (C) 2003 Elsevier Science Ltd. All rights reserved.

Absorption spectrum of recently discovered single-walled 4 Angstrom carbon nanotubes is measured. The semiempirical PM3 localized-density-matrix method is employed to evaluate the absorption spectra of three possible 4 Angstrom single-walled carbon nanotubes, (3,3), (4,2), and (5,0). Both experimental and calculated results reveal that these nanotubes have finite optical gaps and strong anisotropic optical responses. When the electric field is perpendicular to the nanotubes, they are transparent to visible lights; and this is confirmed and explained by the calculations. Compared to the measured absorption spectrum, calculated absorption spectra are used to determine the chirality of the nanotubes synthesized in the channels of porous zeolites. (C) 2002 American Institute of Physics.

Daliuta subbituminous coal (DL), loaded with Fe-2(MoS4)(3) bimetallic catalyst, was liquefied in a 50 ml micro-autoclave with tetralin as solvent at 440degreesC, initial hydrogen of 6.0 MPa, soaking time of 30 min in attempt to produce one to four ring aromatic chemicals. The catalytic effects of in situ impregnated Fe-2(MoS4)(3) in water solution with and without surfactant were investigated in terms of coal conversion, oil + gas yield and the yields of aromatic, aliphatic and polar compound fractions in the oil. The conversion, oil + gas, aromatics and polar compound yields of DL coal, loaded with 1 wt\% daf FeMo of Fe-2(MoS4)(3) bimetallic catalyst, were 78.2, 70.5, 20.8 and 16.7 wt\% daf, respectively, which were higher than those with 1.0 wt\% Fe (based on daf coal) of Fe2S3 (62.6, 54.2, 13.4, 13.2 wt\% daf, respectively) or 1.0 wt\% Mo of ammonium tetrathiomolybdate (70.8, 63.2, 16,7, 14.1 wt\% daf, respectively) alone under the same conditions. When the catalyst was impregnated on coal in surfactant solution, the coal conversion and product yields were further increased. (C) 2002 Elsevier Science Ltd. All rights reserved.

The oil sludge generated from the pretreatment of the used lubricating oil re-refinery is characterized as a complex and tight water/oil emulsion. The water content varies from 38 to 77 wt\%. When the water content is low, the emulsion is of water in oil type. When the water content is high, small oil droplets exist in the dispersed water phase. The oil in the sludge is not different from the oil in the raw feed based on physical and thermal analyses. Centrifuging or gravitational settlement at elevated temperature does not show significant effects on water separation. The usage of inorganic chemicals and the typical demulsification agents from oil fields does not give satisfactory results either. The ultrasonic wave shows some dehydration on some samples. The freeze and thaw method proves to be the best method with over 90\% of water removed from the on sludge at the energy cost of about 0.01 US\$ liter.

A mathematical model of coupled heat and mass transfer was applied to batch fluidized-bed drying with microwave heating of a heat sensitive material-carrot. Four kinds of microwave heating with intermittent variation were examined. The numerical results show that different microwave heating patterns can affect the fluidized bed drying significantly. Changing the microwave input pattern from uniform to intermittent mode can prevent material from overheating under the same power density. Supplying more microwave energy at the beginning of drying can increase the utilization of microwave energy while keeping temperature low within the particle. For a particle diameter of 4mm, fluidization velocity of 2 m/s, inlet airflow temperature of 70degreesC and the bed area factor of 80, the drying time are 750 and 1000s, respectively, for the two good operating conditions with on/off periods of 125/375s and 375/375s. The cumulative microwave energy absorbed by particles at the end of drying is 1415 and 2300kJ/kg (dry basis), respectively.

Carbon adsorbents (CAs) were made by heat treatment of a mixture of coal char and KOH under the protection of an inert argon flow and the influence of operating conditions on the properties of adsorbents was investigated. Changes in the characteristics of graphitic crystallites during manufacture by X-ray diffraction (XRD) analysis indicated that disappearance of the peak corresponding to 002 faces correlated to high specific surface area. Based on the experimental results, a new model of graphitic crystallites containing hydrogen atoms is proposed to calculate idealized surface area of CAs. With this model. the idealized surface areas of CA can be precisely calculated with the aid of X-ray diffraction. In this way, some experimental problems can be overcome, such as the difficulty to measure specific surface area with N-2 adsorption when pore diameters are too small and overestimation when surface areas are too large. (C) 21002 Elsevier Science Ltd. All rights reserved.

Electro-osmotic dewatering (EOD) of 9.1 wt \% bentonite slurry was investigated using a stationary and rotating anode. The rotational speed varied from 0 to 300 rpm. Excessive slurry is necessary to load beyond the anode initially to maintain good contact between the anode and the dewatered slurry. The water removed from the slurry increased significantly with the rotational speed initially and reached a plateau at 240 rpm. This increase is found to be due to the "falling off" of the dry cake from the rotating anode. The average solid content of the cake in the chamber after EOD can be 24.6 wt \% with the anode rotating at 240 rpm and 3 times excessive initial loading of slurry. This solid content is 70.8\% higher than that obtained using a stationary stainless steel anode. When a pin was inserted beneath the rotating anode, an optimal cake thickness of 5 mm was found in terms of water removal. The energy consumption for the process is <20\% of the latent heat of water evaporation.

The effects of microwave heating patterns were investigated for the case of batch fluidized bed drying by solving numerically a coupled heat and mass transfer model. Three patterns, uniform, sinusoidal and rectangular waves, were examined with the average electric field strength kept constant at 1000 V/m. Properties of apple were used to represent porous materials. The results show that the magnitude and distribution of the moisture, temperature and pressure within a particle can be significantly affected. More importantly, the drying time and microwave energy consumption change with the pattern of how microwave heating is applied. Particularly, intermittent heating with a rectangular wave pattern has the most microwave energy consumption but the shortest drying time. For a particle size of 5 mm, airflow rate of 2 m/s and temperature of 60 degreesC, the bed area factor f(A) of 100, the drying time is, respectively, 1600, 2000, 2400 s for rectangular, sinusoidal, and constant microwave heating. The values of microwave energy consumed for the three cases are, respectively, 2145, 1980, and 1560 kJ/kg water evaporated. (C) 2001 Published by Elsevier Science Ltd.

Daliuta subbituminous coal, from Shenfu, Shanxi province of China, was liquefied in a 50 mt micro-autoclave apparatus at 440 degreesC, initial hydrogen pressure of 6.0 MPa, soaking time of 30 min, using a mixture of tetralin and cyclohexane as solvent. The experiments were carried out to investigate the effects of in-situ impregnated Fe2S3 on the liquefaction conversion, oil and gas yields of the coal, and the aromatic, aliphatic, and polar compounds fraction content in the oil. The effect of surfactant treatment during catalyst impregnation was also studied using hexadecyl-trimethylammonium bromide. Gradient elution chromatography (GEC), GC, and GC-MS were used to characterize and quantify the coal liquids. XRD and TEM were used to characterize the catalyst. The results indicate that without catalyst the conversion and oil yield are 43.2 and 37.4 wt \%, respectively. At the same reaction condition but with the addition of 1.0 wt \% Fe (based on daf coal), the conversion and oil yield reach 62.6 and 54.2 wt \%, respectively. When the surfactant was used during the 1 wt \% Fe catalyst impregnation, the conversion and oil yield became 68.8 and 59.5 wt \%, respectively. The catalyst is dispersed in nanometer size particles in amorphous phase that transforms to pyrrholite phase during the liquefaction. The addition of 9.2 x 10(-4) hi surfactant changes the zeta -potential of the coal particles from -15 mV to +29 mV, decreases the size of catalyst particle on the coal surface from 30-40 to 15-20 nm. The oil products are complex aromatics with 2 to 3 rings.

Wet air oxidation (WAO) was applied to treat the desizing wastewater from natural and manmade fiber processing in a 2-L autoclave reactor. The range of operating temperatures examined was between 150 and 290 degrees C. The partial pressure of oxygen ranged from 0.375 to 2.25 MPa at a reference temperature of 25 degrees C. Variations in chemical oxygen demand (COD) and total organic carbon were monitored during each experiment and used to evaluate the performance of the reaction process. Experimental results showed that WAO is an efficient method for the treatment of desizing wastewater. A higher COD removal was achieved under gentler reaction conditions with the aid of a catalyst. A two-parameter mathematical model involving a fast reaction and a slow reaction was used to describe the WAO reaction kinetics and to calculate the reaction activation energies.

A mathematical model of heat and mass transfer is developed for fluidized-bed drying with microwave heating. The numerical results show that the temperature is uniformly distributed within a particle and that the pressure distribution in the particle has st significant effect on microwave fluidized-bed drying. The electric field strength E is an important parameter affecting the magnitude and distribution of the moisture, temperature, and pressure within a particle. At E = 10 000 V/m, a pressure difference of 1.3 MPa and a temperature of over 300 degrees C are obtained. Microwave fluidized-bed drying is capable of a much higher drying rate than conventional fluidized-bed drying, while it also maintains a low particle temperature. At a constant E, the drying time increases initially with the working load but gradually reaches a constant because of the limited moisture-carrying capacity of gas. The microwave power absorbed by the particles decreases during the drying process, and some of the microwave energy can be lost to the fluidized gas for certain operating conditions. Although the advantage of a high heat- and mass-transfer coefficient associated with the fluidized bed does not contribute to water evaporation at a high load, fluidization is still important for achieving better product quality: and a slightly higher drying rate when compared with microwave fixed-bed drying.

A coupled heat and mass transfer model is developed for batch fluidized-bed drying of moist porous particles considering the temperature, moisture saturation and pressure distributions in the particle. The model equations are solved numerically based on physical properties of apple. The heat and mass transfer mechanisms in the fluidized-bed drying process are analyzed. The results show that capillary flow and vapor diffusion play different roles in moisture transfer in the particle during different drying periods. The internal heat transfer can greatly affect the drying process while the effect of gas pressure distribution is insignificant. Due to the coupled effects between gas and particles, the state of gas in the fluidized-bed changes substantially along the bed height and affects the heat and mass transfer in the particle significantly. A new parameter called bed area factor is derived and analyzed. It is important in determining the drying efficiency in the design and operation of fluidized-bed dryers. The effects of particle parameter and inlet gas conditions on heat and mass transfer in the fluidized-bed drying process an discussed through the analyses of drying characteristics. (C) 2000 Elsevier Science Ltd. All rights reserved.

Xinglong coal, a sub-bituminous coal, was swollen with pyridine or tetrahydrofuran followed by liquefaction in a 70-ml autoclave apparatus. The experiments were carried out to investigate the effects of temperature, solvent, atmosphere and catalyst on the liquefaction of solvent-swollen coal and untreated coal. The results indicate that the conversion of coal could be effectively improved in the temperature range of 320-420 degreesC by swelling pretreatment. Molecular hydrogen shows no contribution to coal conversion during the liquefaction of pyridine-swollen coal in the absence of a catalyst and in the presence of hydrogen donor solvent such as tetralin. With the addition of a catalyst, the liquefaction conversion of pyridine-swollen coal is higher in H-2 than that in N-2. The swelling pretreatment of coal can improve the liquefaction yields, weaken the dependence of the process on the presence of molecular hydrogen and the hydrogen donation ability of the solvent, and increase the conversion of coal liquefaction. (C) 2000 Elsevier Science B.V. All rights reserved.

The fixed-bed drying of moist porous particles is described mathematically with a comprehensive heat and mass transfer model. The temperature, moisture content and pressure distributions in a particle were considered in the model along with the conjugate effects between the gas and particles in the fixed-bed. After dividing the deep bed into a series of thin layers, the fixed-bed drying model is solved layer by layer with finite difference method. The thin-layer model includes both the external and internal resistances of heat and mass transfer for particles in the bed. The numerical results show that non-uniformity exists not only for the temperature and relative humidity of gas in the fixed-bed, but also for the temperature, moisture content and pressure in the material. The drying behavior of each layer is significantly affected by the non-uniformity of drying conditions along the bed height. The distributions of temperature and moisture content in the particle play a very important role in heat and mass transfer in the fixed-bed drying. However, the effect of pressure distribution on the drying process is negligible. The calculation shows that a drying front exists in the fixed bed and moves forward linearly with drying time. The drying efficiency is higher in deep-bed drying than in thin layer drying up to a certain bed height. (C) 1999 Elsevier Science Ltd. All rights reserved.

Water extraction experiments were carried out in a semi-continuous operation apparatus with the substrate being Huadian oil shale from Jilin Province of China. Both non-isothermal and isothermal extraction techniques were employed. The effects of temperature and pressure were investigated in terms of degree of conversion, extract as well as gas yield and formation rate, and the compositions of extract and gas. For non-isothermal extraction, temperature varied from ambient value to 500 degrees C and pressure stayed either at 15 or 30 MPa. Isothermal extraction experiments were carried out at four levels of temperature from subcritical to supercritical conditions and two supercritical pressures of 25 and 30 MPa. The results indicated that the extract was obtained mainly in the temperature range between 300 degrees C and 500 degrees C and gas formation was only observed at temperatures higher than 350 degrees C. A maximum formation rate exists for extract and gas at about 390 degrees C. The major extract component is asphaltene and the major gas formed is CO2 for non-isothermal extraction. The large increase in the formation rate of H-2 and CH4 at high temperature results in a secondary increase of gas formation rate starting at 460 degrees C. The isothermal extractions show that a conversion plateau exists when temperature is over 400 degrees C where a maximum extract yield was also found. The experimental findings were explained well in terms of the variation of hydrocarbon solubility in water and the degree of pyrolysis of oil shale. Water extraction shows a higher conversion, slightly lower extract yield, more oil content than toluene extraction. The isothermal results re-establish that nonisothermal extraction technique is a useful tool in searching the optimal extraction conditions. (C) 1999 Elsevier Science Ltd, All rights reserved.

A diffusion model of heat and mass transfer in moist porous media is obtained for low intensity convection drying found typically in food products and vegetable dehydration. The effective diffusivity was analyzed based on the coupled effects of moisture content and temperature on mass transfer in capillary flow, evaporation-condensation, and transition regions. The temperature effect was found to be significant in the transition and evaporation-condensation regions. The model was solved numerically using the finite difference method. Physical properties of banana were determined. The results show that the most intensive heat and mass transfer occur in the transition region where both capillary flow and vapor diffusion play a significant role. The length of the transition region is determined clearly by analyzing the liquid flux distribution in the material, its value depends very much on the permeability of the material. The model proves that the assumption of evaporation front is valid for drying of very permeable materials. For the case of food and vegetable dehydration with the permeability below 10(-19) m(2), more comprehensive analysis is necessary. (C) 1999 Elsevier Science Ltd. All rights reserved.

A mathematical model was established successfully to analyze the gas separation concentration polarization which becomes an important problem due to the rapid development of membranes, especially the increase of permeation rate. The influences of membrane performance and operation parameters on concentration polarization were studied in terms of permeation fluxes of the more and the less permeable gases and separation factor. Sample calculations were presented for the two typical gas separation applications, hydrogen recovery and air separation, with shell side feed in hollow fiber module. The permeation rate was found to be a dominating factor in affecting concentration polarization, while the influences of separation factor to be significant initially and to level off gradually. Increasing feed gas velocity leads to a decrease in the concentration polarization. Operation pressures' effect is limited and the composition of feed gas shows no effect. The range in which concentration polarization is significant has been identified by studying the combined effects of the permeation rate, separation factor and feed gas velocity. Concentration polarization is important for process analysis and design when the permeation rate of the more permeable gas is larger than 1x10(-4) cm(3) (STP) cm(-2) s(-1) cmHg(-1) (100 GPU). (C) 1999 Elsevier Science B.V. All rights reserved.

The ultrafiltration (UF) and nanofiltration (NF) membranes have been prepared successfully from poly (phthalazine ether sulfone ketone) (PPESK), a proprietary chemical of excellent thermal, chemical and mechanical stability. The effects of PPESK concentration, the type and concentration of additives in the casting solution on membrane permeation flux and rejection were evaluated by using orthogonal array of the design of experiments in separation of polyethyleneglycol (PEG). It is shown that PPESK concentration and the additive in the casting solution is the dominant factor on the rejection and permeation flux, respectively. The membrane performance is consistent and agrees with the theoretical analysis. The membranes were applied in the dye separation with the effects of evaporation time, heat treatment and the type of dye studied. The separation of a variety of dyes of 600-900 Da can be accomplished by the PPESK membranes properly prepared. Over 98\% dye rejections were obtained for seven typical dyes. The permeation flux increases greatly by raising operation temperature and pressure without significant change of rejection. (C) 1999 Elsevier Science B.V. All rights reserved.

Wastewater from a preserved bean curd manufacture was treated using the membrane separation method. The wastewater had chemical oxygen demand (COD) of about 10 000 mg/l. Chemical coagulation was rejected due to its poor efficiency in COD removal. Biological oxidation was not considered because of its requirement of large space which is not available in the factory. Microfiltration and ultrafiltration were tested but found inadequate for COD removal to meet the government foul sewer discharge permit, 3000 mg/l. Nanofiltration was found to be a feasible technology for treating this kind of wastewater. The permeate flux and COD were investigated in relation to the transmembrane pressure drop, temperature, and;feed solution COD concentration. The permeate flux was found to increase significantly with transmembrane pressure drop and to decrease with feed concentration. The permeate COD for all the conditions tested meets the discharge permit. The permeate COD decreases with the increase of transmembrane pressure drop and increases with the operation temperature, which is consistent with the theory. The permeate can be reused in the bean processing and the concentrate may be returned to the production line. This method has been adopted by a bean curd manufacturing factory in Hong Kong. (C) 1999 Elsevier Science B.V. All rights reserved.

For through drying there are three distinct drying rate periods, increasing rate, constant rate and falling rate. The increasing rate period is so important that nearly half of the drying is completed in this period only. A drying rate - moisture content relationship for this period was obtained based on theoretical analysis. It was verified with experimental data. A quantitative representation of the complete drying rate curve was established using this relationship and a modified power law equation for the falling rate period drying rate - moisture content relation. It needs five parameters to quantify the through drying from wet to dry: moisture content at the end of the increasing rate period; exponent for the drying rate - moisture relationship during the increasing rate period; constant drying rate; critical moisture content and the power-law exponent for the falling rate period.