Effect of hot air assisted infrared drying on drying characteristics and quality of rice bran pellets

The objective of this study was to determine drying characteristics and quality of rice bran pellet subjected to hot air assisted infrared (HA-IR) drying at different levels of infrared (IR) intensity (750 – 3750 W/m2) and air temperature (40 – 80°C). The rice bran pellets were dried from 0.18 to 0.08 g water/g dry matter. The maximum drying rate (DR) and drying time were in the ranges of 0.0030 – 0.0165 g water/g dry matter·min and 8 – 54 min, respectively. Higher IR intensity and air temperature resulted in greater maximum DR and shorter drying time. The same trend was also observed for the effective moisture diffusivity (Deff) values which were between 0.3103×10-7 and 2.7603×10-7 m2/s. As compared to the commercial reference sample of dried rice bran pellets, the products of this study had higher oil content and lower FFA content. The oil content was affected by IR intensity only while the FFA content was affected both by IR intensity and air temperature. HA-IR drying could improve drying characteristics of the rice bran pellets and produce better quality of the dried products

Experimental investigation of air characteristics during dehumidification in the multilayer desiccant bed column system

The gold of this research is to investigate air characteristics during dehumidification process using the multilayer desiccant bed. Silica gel packing in the multilayer column was used as a desiccant material. Airflow direction in the column was designed in a zigzag path passing each desiccant layer. The changes in temperature and relative humidity of exit air were recorded after dehumidification at different airflow rates of 18, 36, and 72 m3/h. In the desiccant regeneration process, moisture in silica gel was removed by 85°C of hot air at varied airflow rates. The characteristics of exit air after regeneration were also monitored. The result revealed that air humidity ratio was significantly decreased using multilayer desiccant bed column. The highest rates of air dehumidification and desiccant regeneration were observed in the first 5 min operation. The highest air dehumidification rate was 12.82 g/min at the airflow rate of 72 m3/h and the highest regeneration rate of desiccant was 6.70 g/min at the airflow rate of 72 m3/h. In addition, the dual column of multilayer desiccant bed can be successfully applied to cyclic operation of dehumidification and regeneration when the cycle time were 5 min and airflow rate 36 and 72 m3/h

Drying characteristics and quality evaluation in convective drying of Cissus quadrangularis Linn.

This study aimed to investigate the effect of drying temperature (40, 60, 80, and 100°C) on drying characteristics of Cissus quadrangularis Linn. (CQ) undergoing convective drying. Physical properties and phytochemicals of the dried CQ were also evaluated. CQ with the thickness of 5 mm was dried from about 10 to 0.1 g water/g dry matter. The results showed that increasing drying temperature increased drying rate (DR) and effective moisture diffusivity (Deff) and consequently decreased drying time. The drying time, maximum DR, and Deff were in the ranges of 85-1920 min, 0.0059-0.0248 g water/g dry matter·min, and 0.7302-9.1281×10-9 m2/s, respectively. Lower drying temperature could preserve quality of the dried CQ. Decreasing drying temperature resulted in greener and lower bulk density and shrinkage. The greatest total phenolic content (TPC) and quercetin content were obtained by drying the CQ at 60°C

Drying kinetics and quality of Cissus quadrangularis Linn. dried by convective hot air

This research aimed to develop a suitable drying model of convective hot air drying of Cissus quadrangularis Linn. (CQ), determine the effective moisture diffusivity of the drying process and the activation energy of CQ, and investigate the effects of different drying temperatures (40, 60, 80, and 100°C) on energy consumption and quality of dried CQ. The generalized linear-plus-exponential-type model proposed in this study could be used to describe the moisture data of hot air drying of CQ satisfactorily with an R2 of 0.9957. The effective moisture diffusivity was in the range of 0.7302-9.1281 ×10-9 m2/s. a positive relationship was observed between this parameter and drying temperature. The activation energy of CQ was 39.78 kJ/mol. The lowest energy consumption of 3.40 kWh was required when the highest drying temperature of 100°C was applied. The quality was well preserved when CQ was dried at a lower drying temperature. Drying at 60°C produced dried CQ with the lowest total color difference (16.76), shrinkage percentage (88.47%), and bulk density (0.1817 g/cm3) as well as the highest total phenolic (1062 mg GAE/100 g dry matter) and quercetin contents (0.955 mg/100 g dry matter)

Vibratory bed assisted infrared drying of parboiled rice and its rice bran stability

The purposes of this research were divided into two parts: (1) to determine the drying characteristics and quality of parboiled paddy undergoing vibratory bed assisted infrared (VIR) drying, and (2) to study the stability of rice bran from the VIR-dried parboiled paddy. Infrared (IR) drying and hot air (HA) drying were applied for comparison purpose. For the experiment 1, VIR drying of parboiled paddy provided the best drying characteristics with the shortest drying time of 50 min and the maximum drying rate of 0.00146 g water/g dry matter·min. VIR drying also produced the greatest head rice yield of 61.3%. The experiment 2 presented that rice bran from VIR-dried parboiled paddy had the highest oil content of 0.256 ± 0.041 g/g dry matter and the most stable in term of minimum change in free fatty acid (FFA) content. The increase in FFA during storage for 14 days was 0.36%. However, the increases in FFA of rice bran from IR-and HA-dried parboiled rice and normal rice were 0.38, 1.36, and 4.10%, respectively

Effect of different desiccant bed designs in a desiccant column on their dehumidification performance

A design with multilayers of solid desiccant and air ducts in a desiccant container was developed to allow good air flow in a zigzag pattern. The desiccant material was silica gel stacked as multiple layers in a column with different numbers of layers and with or without air holes on the upper cover of the container that penetrated through all layers. Air dehumidification characteristics and psychrometric properties of air of various desiccant bed designs were investigated. Dehumidification rate, percentage adsorbed water, desiccant column effectiveness of each design were evaluated at an air flow rate of 1.2 m3/min, where the control was a single layer packed bed design. Both kinds of multilayer bed designs (with and without air ducts) exhibited a significantly better dehumidification rate, percentage adsorbed water, and desiccant column effectiveness than the control. The experimental dehumidification psychrometric process was consistent with the theoretical adiabatic dehumidification process. The percentage dehumidification rate as time passed for every multilayer bed design was better than that of the control. The 15-layer bed design with air holes exhibited the highest values of about 16 g water/min dehumidification rate, 52% adsorbed water, and 0.998 desiccant column effectiveness

Modeling of hot air drying of coconut residue

In this study, the effect of drying temperature (50-110°C) on hot air drying characteristics of coconut residue was investigated. The drying time and drying rate (DR) were in the ranges of 540-100 min and 0.0048-0.0182 g water/g dry matter·min at the drying temperature of 50-110°C, respectively. Six drying models (Lewis, Page, Henderson and Pabis, Logarithmic, Midilli et al, and linear-plus-exponential model) were used to determine the change in moisture ratio (MR) with drying time. The linear-plus-exponential model provided best fitting of the predicted MR to the experimental MR with the highest average R2 of 0.9985 and the lowest RMSE of 0.01463. The variation of drying temperature with the constants and coefficient of the model was polynomial type. The generalized linear-plus-exponential model as a function of drying temperature gave best result of prediction of MR with the R2 of 0.9709

Evaluation of cyclic efficiency of multilayer desiccant bed column

The main objective was to evaluate cyclic efficiency of a multilayer desiccant bed column. The experimental setup consisted of an air humidifier unit, a heating unit for regeneration, and the desiccant bed column with 15 layers. An airflow rate of 2.4 m3/min with the humidity ratio of 20 g water/kg dry air was used in this study. The results showed that the highest dehumidification rate of 21 g water/min was found at the beginning of the dehumidification process. During the regeneration process, the highest regeneration rate was 39 g water/min when regenerating the desiccant at a temperature of 90°C. For cyclic operation process, the cyclic efficiencies were 11% and 7% at the regeneration temperatures of 70°C and 90°C, respectively. The cyclic efficiency was dependent on the regeneration temperature

Experimental investigation of air characteristics during dehumidification in the multilayer desiccant bed column system

The gold of this research is to investigate air characteristics during dehumidification process using the multilayer desiccant bed. Silica gel packing in the multilayer column was used as a desiccant material. Airflow direction in the column was designed in a zigzag path passing each desiccant layer. The changes in temperature and relative humidity of exit air were recorded after dehumidification at different airflow rates of 18, 36, and 72 m3/h. In the desiccant regeneration process, moisture in silica gel was removed by 85°C of hot air at varied airflow rates. The characteristics of exit air after regeneration were also monitored. The result revealed that air humidity ratio was significantly decreased using multilayer desiccant bed column. The highest rates of air dehumidification and desiccant regeneration were observed in the first 5 min operation. The highest air dehumidification rate was 12.82 g/min at the airflow rate of 72 m3/h and the highest regeneration rate of desiccant was 6.70 g/min at the airflow rate of 72 m3/h. In addition, the dual column of multilayer desiccant bed can be successfully applied to cyclic operation of dehumidification and regeneration when the cycle time were 5 min and airflow rate 36 and 72 m3/h

Effect of torrefaction temperature on energy properties of spent coffee ground

The aim of this research was to investigate the effect of torrefaction temperature on 4 energy properties as high heating value (HHV), enhancement factor, solid yield, and energy yield of spent coffee ground (SCG). Four different torrefaction temperatures (200, 250, 300, and 350°C) were selected. Torrefaction process was conducted at the heating rate of 10°C/min. HHV and enhancement factor were the highest when SCG was torrefied at the highest temperature of 350°C. However, at this temperature, solid and energy yields were the lowest. Torrefaction temperature highly affected these four energy properties with R of higher than 0.9. Regression models representing the relationship between torrefaction temperature and HHV and energy yield were HHV = 0.0519T+15.917, R2 = 0.9483 and energy yield = -0.2743T+155.1, R2 = 0.9976. These models are helpful for prediction of the energy properties of SCG undergoing torrefaction process in the studied temperature range