Gasifiers: Types, Operational Principles, and Commercial Forms Chanchal Loha, Malay K. Karmakar, Santanu De and Pradip K. Chatterjee Abstract 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 tech- nologies are used depending upon the requirement. Technologies used for gasifi- cation 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. Keywords Gasifier ⋅ Fixed bed ⋅ Fluidized bed ⋅ Entrained flow Commercial gasifiers C. Loha ( ✉ ) ⋅ M. K. Karmakar ⋅ P. K. Chatterjee CSIR-Central Mechanical Engineering Research Institute, Durgapur 713209, West Bengal, India e-mail: chanchalcmeri@gmail.com M. K. Karmakar e-mail: malaycmeri@gmail.com P. K. Chatterjee e-mail: pradipcmeri@gmail.com S. De Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India e-mail: santanu80@gmail.com © Springer Nature Singapore Pte Ltd. 2018 S. De et al. (eds.), Coal and Biomass Gasification, Energy, Environment, and Sustainability, https://doi.org/10.1007/978-981-10-7335-9_3 63