03-08-2012, 02:05 PM
BIOGAS FUEL FOR INTERNAL COMBUSTION ENGINES
engine modification.pdf (Size: 213.89 KB / Downloads: 193)
SUMMARY
Author presents the problems of biogas use for powering internal
combustion engines. Modification of internal combustion engines for
stationary electrical generators and internal combustion engines for
tractors and light duty trucks is reviewed.
Properties and desired characteristics of biogas fuel are also
presented. The main aspect of stationary internal combustion engines for
electrical generators use is for isolated farms and rural areas, which is
now thoroughly examined through techno-economical analysis and
impacts on environment.
KEY WORDS:
biogas, engine, electrical energy
INTRODUCTION
Current energy situation throughout the world and the fact that main
resources of energy, such as crude oil, natural gas, coal and nuclear fuel
are not renewable give importance to other sources of energy, like hydro
energy, solar energy, energy of wind and biogas. Mentioned sources of
energy are all renewable, but biogas is particularly significant because of
possibility of use in internal combustion engines, which are the main
power source for transport vehicles and also commonly used for powering
of generators of electrical energy. This possibility of use is justified by
biogas' properties, which make it convenient for IC engines.
PROPERTIES OF BIOGAS AS FUEL FOR INTERNAL COMBUSTION ENGINES
Biogas is the product of fermentation of man and animals' biological
activity waste products when bacteria degrade biological material in the
absence of oxygen, in a process known as anaerobic digestion. Since
biogas is a mixture of methane (also known as marsh gas or natural gas)
and carbon dioxide it is a renewable fuel produced from waste treatment.
Biogas contains 50% to 70% of CH4, 2 % of H2 and up to 30 % of CO2.
After being cleaned of carbon dioxide, this gas becomes a fairly
homogeneous fuel containing up to 80 % of methane with the calorific
capacity of over 25 MJ/m3. The most important component of biogas, from
the calorific point of view, is methane, CH4. The other components are not
involved in combustion process, and rather absorb energy from
combustion of CH4 as they leave the process at higher temperature than
the one they had before the process. Requirements to remove gaseous
components depending on the biogas utilization are in Tab. 1 (Hingerl,
2001).
Tab. 1 Requirements to remove gaseous components depending on the biogas utilization
Application H2S CO2 H2O Siloxane
CHP engine < 500 ppm no no condensation yes
Vehicle fuel yes recommended yes no
Thermodynamic properties of CH4 at 273 K and 101325 Pa are: