Characteristics of Flame Stability and Gaseous Emission of Bio-Crude Oil from Coffee Ground in a Pilot-Scale Spray Burner

Abstract

Coffee ground has been recently considered as a new biomass resource in relation to the increasing coffee consumption worldwide. The bio-crude oil can be produced by fast pyrolysis of coffee ground, and it has advantages of larger heating values in comparison with those from other biomass. But the bio-crude oil from coffee ground has a significantly high viscosity which can hinder the application to conventional burners. In this study, a pilot-scale burner system with a 35 kW capacity with an air-blast atomizing nozzle was developed for the combustion of bio-crude oil from coffee ground with a high viscosity. A downward fuel injection system was adopted to enhance the ignition of fuel spray and the flame stabilization, and a movable block swirl generator was installed for the combustion air. The bio-crude oil was blended with ethanol at the volumetric ratio of 9:1 to enhance the combustion characteristics. The effect of various atomizing air pressures, swirl intensities, and overall equivalence ratios on the flame stability and gaseous emission were investigated to find out the optimum operating conditions for a bio-crude oil burner.

Coherent Structures Analysis of Methanol and Hydrogen Flames Using the Scale-Adaptive Simulation Model

“…Figures 6 and 7 show the coherent structures of the methanol and hydrogen flames at different values of the Q criteria. For methanol, a fully developed PVC is seen, unlike the results reported by Guevara et al [1,21], in which only a ringed vortex was seen at the central axis of the flame. This difference may be due to the velocity profiles used at the entrance to the combustion chamber for the SAS model.…”

“…In contrast, the hydrogen flame develops a ringed structure, as reported by Guevara [1,21], as well as the PVC centered on the axial axis. These ringed vortices around the flame arise as a consequence of the velocity gradient of the air when it enters the chamber; due to the non-slip condition at the walls of the swirler, a velocity gradient is created.…”

“…It can also be observed that there is a high recirculation zone in the area close to the fuel injector, which favors a good stoichiometric mixture where the combustion temperature reaches a maximum. The remaining areas of the chamber achieved temperatures of 800-1000 C. However, it can be seen that the SAS model produces similar maximum temperature peaks for both flames, while the LES model gives different results [1]. This means that the use of the SAS model may have a direct impact on the calculated temperatures, and further study is required to understand which measurement affects the results.…”

“…One of the main difficulties with any device that uses turbulent combustion is flame stability, which depends on various factors, such as the fuel and the oxidant used, as well as the velocity field associated with their injection, the geometric of the combustion chamber, and the construction material, among others [1]. Flame instability is an acoustic phenomenon where pressure waves grow abnormally due to their coupling with heat release fluctuations [2].…”

Renewable Energy and Energy Storage Systems

“…The bio-oil produced from fast pyrolysis has a high viscosity, making its use more difficult. For this reason, Choi et al [93] developed a pilot-scale burner with a capacity of 35 kW and equipped it with an air-blast atomizing nozzle. In order to improve the fuel spray ignition and maintain a more stable flame, a downward fuel injection system was developed.…”