Document Type

Dissertation

Publication Date

2008

Department

Engineering

Keywords

biomass energy, gasification, carbon conversion, gasifier system, fluid bed, ground seed corn

Abstract

Gasification is one means of transforming biomass so that it can be more easily utilized as a renewable source of thermal energy, transportation fuel, and chemicals. Under typical gasification conditions it is not uncommon that a portion of the carbon entering with the biomass leaves the reactor unconverted as char. Understanding and improving carbon conversion during biomass gasification in an atmospheric bubbling fluidized bed reactor is the focus of this study.

To better understand the intricacies of biomass gasification a carbon conversion analytic methodology was developed. The methodology is based on a mass balance of the fixed carbon entering and leaving the gasifier. It allows fixed carbon leaving the reactor by elutriation to be distinguished from that which has been chemically converted. Carbon conversion analysis was applied to several steady state gasification experiments in a laboratory scale bubbling fluidized bed reactor utilizing ground seed corn as the feedstock. The impact on the gasification of ground seed corn was investigated for variations in the equivalence ratio, the gasification temperature, the superficial gas velocity, the biomass particle size, and the concentration of H2O entering the reactor. Insights gleaned from these experiments suggest that carbon conversion during gasification of ground seed corn in a bubbling fluidized bed is limited by elutriation of char comminuted by either fragmentation or chemically assisted attrition. Consequently, increased carbon conversion was realized with reductions in the superficial gas velocity through the reactor.

Comments

  • A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY, Iowa State University
  • Dr. Robert C. Brown, Major Professor
  • © 2008 Kevin Jay Timmer

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