การทำแห้งละอองน้ำยางธรรมชาติโดยลมร้อนจากห้องเผาไหม้แบบพัลส์

Abstract

The main objective of this research is to study the method for producing natural rubber powder from natural rubber latex by spray drying process under hot gas jet generated from a pulse combustor. The pulse combustor is valvelss Helmholtz type that having single tailpipe and single air inlet. In the experiments, study flow characteristics of hot air jet generated by Helmholtz pulse combustor. The distance from tailpipe outlet was varied at 1D, 2D, 3D, 4D, 5D, 6D, 7D and 8D where D was an inner diameter of tailpipe equal to 47 mm. The flow rate of LPG fuel was varied at 22, 25 and 29 V/min. In addition, the experimental study of spray nozzle configuration consisted of 3 air inlet positions. The flow rate of air inlet into the nozzle was varied at 70, 80 and 90 V/min and the flow rate of latex was varied at 20, 40 and 60 g/min. The rubber latex was sprayed from developed air spray nozzle into the drying chamber. Then the latex droplets was heated by hot air and dried in the chamber. After the drying process, the morphology and particle size of natural rubber powders were analyzed by scanning electron microscope (SEM) and electron micro analyzer, respectively. The thermal properties of natural rubber powder was analyzed by thermogravimetry. The properties of raw rubber and Mooney viscosity of natural rubber powder were analyzed. The vulcanized rubber was characterized by mechanical analysis. Including the calculation of total energy consumption in the drying process. The result showed that jet temperature and jet velocity of hot air from the pulse combustor decreased according to increasing of distance from tailpipe outlet. Especially, the jet temperature decreased rapidly. The distributing temperature of the hot air in the drying chamber generated from the pulse combustor. It is distributed throughout the chamber. Drying efficiency and rapid drying of latex. For the effect of spray nozzle configuration at the different air inlet position. It was found that the spray nozzle configuration at the air inlet position tilt angle of 40 degrees with the latex inlet pipe provided good spraying performance in all cases of air flow rate. At the air flow rate of 90 V/min and the flow rate of latex at 20 g/min, the dispersion of the latex was very small and without the blockage of the rubber in the spray nozzle. From the study of various conditions in the spray drying process, in the case studies using talcum powder as a coating for natural rubber particles. It was found that the optimum condition for drying rubber latex was condition for the supplied flow rate of LPG fuel was 29 V/min, the entrance speed of drying chamber was 12 m/s and the flow rate of latex at 20 g/min. After the drying process, the morphology and particle size of natural rubber powders were analyzed by scanning electron microscope (SEM) and electron micro analyzer, respectively. The range of particle size was found from a range of 50 μm to 300 μm. To examine the thermal properties of rubber powder, it was found that thermal stability was around 200 °C. From the Mooney viscosity test, it was found that the natural rubber powder had Mooney viscosity equal to 43.87. Natural rubber powder has tensile strength and hardness equal to 16 MPa and 55, respectively. For studying various conditions in the spray drying process. In the case studies using zinc stearate as a coating of natural rubber particles. It was found that the optimum conditions for spray drying process were the condition for the supplied flow rate of LPG fuel was fixed at 29 l/min, the velocity inlet of drying chamber was 12 m/s and the flow rate of latex at 20, 40 and 60 g/min. At the time of the experiment, the temperature was distributed in the drying chamber. From the study of morphological characteristics of natural rubber particles by electron scanning electron microscope. It was found that the spherical shapes were dispersed without clinging to each other and the particle size was in the range of 90 μm to 600 μm. The rubber powdered has the thermal stability about 200 °C, while, the natural rubber powder having Mooney viscosity equal to 47.65. From mechanical properties testing, it was found that natural rubber powder coated with zinc stearate has the tensile strength and 100% modulus that is close to the case of STR 5L rubber block, with a value of about 10 and 0.95 MPa, respectively.