Chanchal Loha

Evaluation of Air Drying Characteristics of Sliced Ginger (Zingiber officinale) in a Forced Convective Cabinet Dryer and Thermal Conductivity Measurement

A forced convective cabinet dryer is used to study the hot air drying characteristics of sliced ginger placed in a single layer. Ginger is dried from initial moisture content of 87-88% (w.b.) to the final moisture content of 6-7% (w.b.). Experiments are carried out with four different drying air temperatures of 45, 50, 55 and 60°C by keeping the air velocity fixed at 1.3 m/s. The moisture removal rate is found to increase with increase in temperature and drying process occurred at falling rate period for all the temperatures studied. A non-linear regression analysis is conducted to investigate the accuracy of prediction of ten selected thin layer drying models. From the statistical analysis, a best fit curve is obtained which gives better agreement to the experimental drying data. Further, the thermal conductivity of ginger is determined experimentally and a mathematical expression of thermal conductivity as a function of moisture content has been established, which can predict the experimental data within 1.5% accuracy.

Energy generation from fluidized bed gasification of rice husk

Though gasification of biomass in fluidized bed system is an efficient way of biomass utilization, limited experimental data on the fluidized bed biomass gasification are available in open literature. Therefore, an experimental study of biomass gasification is conducted using a laboratory scale bubbling fluidized bed gasifier. Rice husk is used as the biomass material and air-steam mixture is used as the gasifying agent. As the non-granular nature of rice husk makes it difficult to fluidize, silica sand is used as the inert bed material to help in fluidization. Parametric studies are performed to determine the effects of reactor temperature, equivalence ratio, and steam-to-biomass ratio on the product gas composition and the heating value. The results show that both hydrogen percentage and the heating value of the product gas increase with increase in gasification temperature and steam-to-biomass ratio, but they decrease with increase in equivalence ratio. The maximum heating value (4.26 MJ/Nm3) and hydro...

Gasifiers: Types, Operational Principles, and Commercial Forms

Carbonaceous solid materials are converted into gaseous fuel through the gasification process. A limited supply of steam, air, oxygen, or a combination of these serves as gasifying agent. Depending upon the gasifying agent used, the fuel gas will contain mainly hydrogen, carbon monoxide, carbon dioxide, methane, higher hydrocarbons, and nitrogen (if air is used). In gasification, different technologies are used depending upon the requirement. Technologies used for gasification can broadly be classified into four groups; fixed bed or moving bed gasification, fluidized bed gasification, entrained bed gasification, and plasma gasification. In the present chapter, a detail discussion on the design, working principle, merits and demerits of different types of gasifiers are presented. Some of the important commercial gasifiers installed worldwide are also discussed.

Hydrodynamics of Circulating Fluidized Bed Systems

Fluidized bed reactors are used in different industries to carry out multiphase chemical reactions. In these reactors, the fluid is passed through the reactor bed having granular solid materials. The velocity of the fluid is kept high enough to suspend these materials resulting to behave them like fluids. Such reactors are classified as bubbling bed, fast circulating bed or dual bed systems combining two beds depending upon the fluid velocities and constructions of the reactors. For combustion and gasification processes, circulating or dual fluidized bed systems are often preferred because they are more efficient having high throughput. However, the hydrodynamics of such fluidized beds, using normally low-grade feedstocks, is very complex and plays a critical role for successful operation of the plant. Lots of experimental and theoretical investigations are done in this area; however, the available information on the hydrodynamics is limited. In this chapter, the hydrodynamics of circulating fluidized bed systems has been discussed.