Particularities of High Oxygen Content Biofuels Pyrolysis Process

Generating capacities supplied by solid biomass (renewable waste) gather at the moment less than 4.5% of the total renewable power installed worldwide. Given the two folded implications of such technology development and spreading (i.e. energy production and waste management), researches regarding efficient conversion processes and improved power facilities are of great interest currently. In this context, the paper addresses the particularities of high oxygen content biofuels pyrolysis, proposing innovative solutions to overcome the issues found in experimental investigations. Based on thorough experimental research conducted on agricultural wooden biomass and poultry manure, a number of problems arise. Among them, it is highlighted the heating in the absence of oxidants, an undesirable internal process caused by the high oxygen content, which contravenes the general principles regarding pyrolysis. Furthermore, the high oxygen content is associated with great moisture percentages. The present paper reveals the challenges determined by some negative aspects emerging during the pyrolysis of high oxygen content biofuels. Several solutions are proposed to improve the efficiency of the conversion process through adequate control. For instance, it is pointed out that the temperature level at which the pyrolysis process develops plays a crucial role in the general energy balance. On this matter, investigating poultry manure pyrolysis at low temperatures, a significant decrease of the final coke product is noticed. Poultry manure pyrolysis results as a suitable and simple solution to be employed for waste treatment purposes, as its combustible effects (combustible gases and semicoke / coke) are good candidates for energy production.

Download Full-text

Combustion system optimization for dimethyl ether using a genetic algorithm

International Journal of Engine Research ◽

10.1177/1468087419851577 ◽

2019 ◽

Vol 22 (1) ◽

pp. 22-38 ◽

Cited By ~ 1

Author(s):

Marius Zubel ◽

Tamara Ottenwälder ◽

Benedikt Heuser ◽

Stefan Pischinger

Keyword(s):

Oxygen Content ◽

Dimethyl Ether ◽

Ignition Delay ◽

System Optimization ◽

High Oxygen ◽

Experimental Investigations ◽

Compression Ignition Engine ◽

High Oxygen Content ◽

Volumetric Heating ◽

Cooling Effects

Dimethyl ether is a gaseous fuel which can easily be liquefied under moderate pressures. Its high reactivity makes it suitable for combustion in a compression ignition engine, and due to the high oxygen content, its combustion is virtually free of soot. The high oxygen content and low density of dimethyl ether lead to a lower volumetric heating value compared to Diesel fuel. Therefore, the hydraulic flow rates of the injectors have to be increased with larger nozzle holes. The influence of larger nozzle holes on the dimethyl ether spray formation and ignition are presented in this article. Experimental investigations were conducted at a constant-pressure vessel with optical access and with a single-cylinder research engine. Subsequently, a numerical optimization of the piston bowl and injector nozzle has been carried out. A very fast air/fuel mixture formation with dimethyl ether was observed, which leads to a lean combustion with small nozzle diameters. With increasing nozzle diameters, the combustion moves toward stoichiometric conditions and with very large diameters to rich combustion conditions. The ignition delay for small diameters is mostly dominated by the lean mixture, and for large diameters, the ignition delay is strongly influenced by cooling effects. For the optimization, the oxidation potential number was maximized, which proved suitable to simultaneously increase efficiency and reduce emissions. A conventional ω-shaped bowl and a step bowl have been optimized, and large bowl diameters were found to be beneficial for dimethyl ether combustion. Furthermore, nozzle diameters around 150 µm showed the most promising results. Compared to the dimethyl ether reference, the simulations with the optimized ω-shaped bowl showed a power increase of 2.7%. Experimentally, the optimized ω-shaped bowl in combination with the reference injector showed an efficiency increase by more than 1% at 2000 r/min full load compared to the dimethyl ether reference.

Download Full-text