Process of parboiling rice by microwave-assisted hot air fluidized bed technique

[EN] In this work the new process of producing parboiled rice (PB) by combinatintion of microwave and hot air fluidized bed (MWFB) was proposed and investigated. Results showed that the drying time was shorter with smaller bed depth, higher drying temperature and higher microwave power. The initial grain temperature, drying temperature, bed depth and microwave power strongly affected the gelatinization of rice starch. The PB produced by MWFB caused a very small broken kernel (1-2%). The whiteness was decreased with increase in drying time, initial grain temperature, drying temperature and microwave power. The specific energy consumption was increased with increasing such operating parameters.The authors express their sincere appreciation to The Office Of The Higher Education Commission (OHEC) and Yala Rajabhat Universisty (YRU), Thailand. Also, the authors thanks to The Thailand Research Fund (TRF) and The Thailand Research Fund (Grant no. DPG5980004), for their financial support.Prachayawarakorn, S.; Saniso, E.; Swasdisewi, T.; Soponronnarit, S. (2018). Process of parboiling rice by microwave-assisted hot air fluidized bed technique. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 1615-1612. https://doi.org/10.4995/IDS2018.2018.7541OCS1615161

Design of an extrusion screw and solid fuel produced from coconut shell

The objectives were to design an extrusion screw to produce biomass solid fuel in a cold extrusion process, and investigate the effects of molasses used as a selected adhesive on the physical properties of extruded products. The material employed consisted of crushed coconut shell char and coconut fiber char mixed at a ratio of 40:60. The ratios of molasses in the mixture were 10:100, 15:100 and 20:100 (by weight) and the extrusion die angles were 1.0, 1.1, 1.2, and 1.3 degrees gradation per experiment. The experimental results showed that the newly designed screw could function properly in the output range 0.75-0.90 kg/min, which is close to the design value. Regarding the molasses's effect on solid fuel properties, increasing the share of molasses was positive for both output and strength of the resulting briquettes, whereas the results of increasing die angle showed decreases in both output and strength. The compressive strength varied between 2.49-2.87 MPa in all circumstances, which was considerably higher than acceptable industrial level. Furthermore, the extruded solid fuel showed excellent resistance to impact force. Regarding energy consumption, the amount of electrical energy used in the extrusion process was insignificant, ranging between 0.040-0.079 kWh/kg

Performance analysis of a double-pass thermoelectric solar air collector

The thermoelectric (TE) solar air collector, sometimes known as the hybrid solar collector, generates both thermal and electrical energies simultaneously. A double-pass TE solar air collector has been developed and tested. The TE solar collector was composed of transparent glass, air gap, an absorber plate, thermoelectric modules and rectangular fin heat sink. The incident solar radiation heats up the absorber plate so that a temperature difference is created between the thermoelectric modules that generates a direct Current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. The ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel where it receives additional heating from the absorber plate. Improvements to the thermal and overall efficiencies of the system can be achieved by the use of the double-pass collector system and TE technology. Results show that the thermal efficiency increases as the air flow rate increases. Meanwhile, the electrical power output and the conversion efficiency depend on the temperature difference between the hot and cold side of the TE modules. At a temperature difference of 22.8 degrees C, the unit achieved a power output of 2.13 W and the conversion efficiency of 6.17%. Therefore, the proposed TE solar collector concept is anticipated to contribute to wider applications of the TE hybrid systems due to the increased overall efficiency. (C) 2008 Elsevier B.V. All rights reserved

Closed-ended oscillating heat-pipe (CEOHP) air-preheater for energy thrift in a dryer

The CEOHP air-preheater consisted of two main parts, i.e. the rectangular house casing and the CEOHP. The house casing was designed to be suitable for the CEOHP. The inside house casing divided the CEOHP into three parts, i.e. the evaporator, the adiabatic section and condenser section. The CEOHP air-preheater design employed copper tubes: thirty-two sets of capillary tubes with an inner diameter of 0.002 m, an evaporator and a condenser length of 0.19 m, and each of which has eight meandering turns. The evaporator section was heated by hot-gas, while the condenser section was cooled by fresh air. In the experiment, the hot-gas temperature was 60, 70 or 80 °C with the hot-gas velocity of 3.3 m/s. The fresh-air temperature was 30 °C. Water and R123 was used as the working fluid with a filling ratio of 50%. It was found that, as the hot-gas temperature increases from 60 to 80 °C, the thermal effectiveness slightly increases. If the working fluid changes from water to R123, the thermal effectiveness slightly increases. The designed CEOHP air-preheater achieves energy thrift.Closed-ended oscillating heat-pipe air-preheater Energy thrift dryer

A novel vortex-fluidized bed combustor with two combustion chambers for rice-husk fuel

A novel vortexing-fluidized bed combustor (VFBC) using rice-husk as fuel was developed and presented. The combined characteristics of vortex combustion and fluidized bed combustion are the main features of the VFBC, which was designed to achieve high thermal capacity (MWth m-3), high thermal efficiency and low diameter to height ratio. The VFBC comprises a vertical cylinder chamber and a conical base, which provides a bed for incompletely combusted fuel. The overall dimensions are 1.10 m in height and 0.40 m in diameter. To evaluate combustor performance, the specific feed rate of fuel and mass flow rates of the primary, secondary, and tertiary air were varied independently of one another. The combustion appeared into two zones characterized by different combustion behaviors, i.e. 1) vortext combustion above the vortex ring and 2) fluidized bed combustion below the vortex ring. The fluidized bed zone has uniform temperature distributions across the cross-section of the combustor. The swirling of air above the vortex ringand the vortex ring itself played important roles in preventing the escape of combustion particulates. Bottomash appeared as fine black and grey particles of ash, which ranged in size from 200 to 600 µm. Fluidizationcould be initiated without the assistance of any inert material mixed into the bed. The experimental resultsindicated that thermal efficiency did not depend on the secondary or tertiary airflows, but was significantlyinfluenced by the excess air resulting from the combined total of the three airflows. The introduction of thetertiary airflow helped maintaining the temperature inside the combustor within acceptable levels. According to experimental conditions, i.e. a specific feed rate of 240 kg h-1m-3 and excess air (157%), it was found that the VFBC could achieve an exit gas temperature of 1060ºC, thermal efficiency of 95%, and thermal capacity of 0.91 MWth m-3. The amounts of CO2, CO, and O2 gases emitted were directly related to thermal efficiency, and the amounts of CO and NOx were 50 and 380 ppm, respectively

A comparative study of low-pressure superheated steam and vacuum drying of a heat-sensitive material

10.1081/LDRT-200032818Drying Technology2281845-1867DRTE

Drying kinetics and inversion temperature in a low-pressure superheated steam-drying system

Industrial and Engineering Chemistry Research4461934-1941IECR