Based On FLUENT Simulation Analysis of Vertical Heat-Carrier Heating Device

Heat-carrier heating device is an important part of biomass pyrolysis oil equipment. In particular, the application of vertical heat-carrier heating device can improve the rate of biomass pyrolysis. In this article, we will analyze the vertical carrier heating device based on FLUENT software and model the temperature field and velocity field of hot gas and carrier so as to draw a conclusion that the final temperature of carrier can reach approximately 840K which can meet the biomass pyrolysis process temperature. Meanwhile, the movement of carrier is very smooth without any stoppage thus laying a solid foundation for the improvement and optimization of the device. Keyword: Heat-Carrier Heating Device; Vertical; FLUENT With the rapid growth of world population and the development of technology, energy shortage becomes more and more serious so that the new energy came into being. As one of the most promising new energy, biofuel is characterized by high cost performance, low price and renewability, which can effectively solve the problems of agricultural and forest waste and environmental pollution to a certain extent. [1] Thus, research on biomass pyrolysis oil equipment has great economic and environmental significance. Since the carrier heating device is an important part of the biomass pyrolysis oil equipment, we mainly focus on the study of vertical carrier heating device in this article. Not only does the vertical carrier heating device need to reach the process temperature through heating, but also to complete the heat transfer process and separation process of hot gas and carrier. Since the design of the device is really difficult and there is no clear specification and industry Standard Reference, we try to provide a new way of design for the vertical carrier heating device through simulation model of heat transfer and the movement of carrier based on FLUENT. 1. The Structure and Working Principles of Vertical Carrier Heating Device 1.1 The Structure of Vertical Carrier Heating Device In order to make the carrier reach the needed temperature of the next process, the vertical carrier heating device passes heat to the carrier through the joint movement of hot gas and carrier. It mainly consists of burner, vertical bed, feeding device, carrier buffer, peephole, hot gas outlet, carrier outlet, cover and insulation layer. The overall structure is shown in Figure 1. International Journal of Control and Automation Vol.8, No.8 (2015) 2 Copyright c 2015 SERSC Figure 1. The Structure of Vertical Carrier Heating Device 1. Burner 2. Inner tube of vertical bed 3. Fluidized pipeline 4. Hex Bolts 5. Homemade flange 6. Hex nuts 7. Peephole 8. Feeding device 9. Feeding tube 10. Outer tube of vertical bed 11. Insulation layer 12. Bellows 13. Carrier outlet 14. Carrier buffer 15. Hot gas outlet 16. Cover 1.2 The Working Principles of Vertical Carrier Heating Device The vertical carrier heating device can make the carrier reach a certain temperature by heat transfer between the hot gas and the carrier. The main working principles are explained as followings. The hot gas which is generated by the burner comes into the heating device at a high speed through the inner tube of the vertical bed, drives the carrier which comes from the feeding device to move upwards along the vertical bed. When the lift of carrier given by the hot gas equals the gravity of carrier, the carrier will move at a constant speed along with the hot gas. As it moves to the inlet of the vertical bed pipeline, the sudden expansion of the diameter leads to a slow-down of the hot gas and the carrier and then the diameter enlarges again at the carrier buffer so that the hot gas and the carrier move upwards again at the same speed with it passing by the inlet of the vertical bed pipeline. Finally, it enters the carrier outlet in free fall through the baffle under the buffer while the hot gas also moves to the next process through the hot gas outlet. During this process, heat transfer is carried out. 2. The Model Establishment of Vertical Carrier Heating Device 2.1 The Parameters of the Main Structure and the Building of Three-Dimensional Model The main structural parameters of the vertical carrier heating device in this study are as follows: the diameter of the inner tube is 377mm; the diameter of the outer tube is 692mm; the overall height of the vertical bed is 23.26m; the height of the inner tube is 2.3m; the height of the carrier buffer is 2.6m; the thickness of the insulation layer is 100mm. According to the structure and the parameters in this article, the three-dimensional simulation model of the vertical carrier heating device is shown in Figure 2. International Journal of Control and Automation Vol.8, No.8 (2015) Copyright c 2015 SERSC 3 Figure 2. The Three-Dimensional Structure of the Vertical Carrier Heating Device 2.2 Mathematical Description The theory of this device mainly depends on the fluid characteristics such as heat convection and the heat-flow coupling calculation based on hydrodynamics and heat transfer. In order to meet the fluid characteristics and the heat transfer performance, continuity equation, momentum equation and energy equation are established [2]. Continuity equation: 0             z w y v x u t    