Prediction of calorific value of syngas produced from oil-palm fronds gasification

The calorific value (CV) of syngas produced from gasification of solid biomass varies depending on the type of biomass as well as the gasifier type. Moreover, the interdependent operating conditions like reactor temperature, moisture content of biomass, and air fuel ratio play a major role in the composition as well as calorific value of syngas. The gasification of oil-palm fronds (OPF) is not studied in the past, and there is no previous work on the expected composition or CV of syngas. Therefore, it is found necessary to predict the CV of syngas for different operating conditions, in order to be able to exploit the energy reserve of this abundantly available biomass waste. This paper presents the prediction of CV of syngas produced from downdraft gasification of OPF by making use of ASPEN PLUS simulation model. The results of the simulation showed how the CV varies with operating conditions: moisture content, air fuel ratio and oxidation zone temperature. The result of the model showed that the CV predicted vary in the range of 4.05 to 4.35 MJ/m³ for increase in the oxidation zone temperature from 500 to 1200°C. In addition, the CV showed a decrease with moisture content. Moreover, a closely similar pattern of change in CV is obtained, through comparison with results reported in literature for gasification of other types of biomass feedstock.

I. Introduction

Biomass gasification is a thermal conversion of solid biomass to gaseous fuel, in which the energy stored in the biomass is converted to calorific value of the produced gas. The fuel gas obtained from gasification is called Syngas, which has major components: Carbon Monoxide CO, Hydrogen H₂, Carbon Dioxide CO₂, and small fractions of Methane CH₄. The fraction of each component gas in syngas is known to vary with the type of biomass [1], [2], initial moisture content of feedstock [1], [3], particle size [4], [5], operating temperature[1], [6], [7], and air fuel ratio (AFR) [3], [7], [8]. The fact that the composition of syngas and its resulting calorific value, vary with type of biomass, type of gasifier, and operating conditions, calls for a means of predicting the calorific value of syngas produced.