2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 110 -
Abstract:
--This paper presents an evaluation of Hydrogen
production of mixed glycerol and rice husk air/steam
gasification. The system consists of a downdraft gasifier and
a gas cleaning system. The size of mixed rice husk-glycerol
briquettes was 3, 5 and 7 cm with moisture content of 4.4%.
The rice husk-glycerol briquettes consist of C (41.8%) H
(5.8%) O (33.9%) N (0.36%) and S (0.004%). LHV of mixed
rice husk-glycerol briquettes was 15,036.43 kJ/kg. Results
showed that biomass gasifier power generation system
consumes fuel at around 50 kg/hr or 5 kg/kWh. Gasifier can
generate product gas at around 74.2 m
3
/h. The mixed rice
husk-glycerol briquettes with length of 3, 5 and 7 cm can
produce H
2
using air as an agent lower compared to the use
of steam as an agent. The HHV of air/steam gasification was
in the range of 4.2-4.9 MJ/m
3
, the hydrogen yield was in the
range of 3-17%, and the gasifier conversion efficiency was
71-84%. The HHV of air gasification was in the range of
4.1-4.9 MJ/m
3
, the hydrogen yield was in the range of 1-14%
and the gasifier conversion efficiency was 42-49%.
Index Terms--
Hydrogen production; Gasification; Rice
husk-glycerol briquette; Gasifier efficiency
I.
I
NTRODUCTION
Biomass gasification is seen as an interesting and as a
very promising technology to substitute the conventional
energy source [1]. Today, due to the increase of fuel
prices and the environmental issues, biomass becomes an
important source of renewable energy for securing a
sustainable energy and for tackling climate change. The
advantages of the biomass are low cost by-product in
agriculture and forestry, and low ash and sulfur contents
[2]. The biomass can be converted to gaseous state
through a process called gasification. The gas known as
producer gas is more versatile than the original solid
biomass itself [3]. The average composition gas are
mainly combustible gas on a dry basis where CO = 13-
25%, CH
4
= 0.25-2.5%, H
2
= 15.1%, while the non-
combustible gas or inert gas consist of CO
2
= 8-19%, N
2
= 45-60% and hydrocarbon (which also include tar) [4].
The energy produced from the producer gas is usually in
the range of 3.5-5.5 MJ/m
3
[5-6]. Generally, the type of
gasifier can be categorized based on the direction of the
This research was financially supported by the Thailand Research Fund
(TRF), contract no. MRG-WII505S044. The authors also acknowledge
Thaksin University for facility support of the project.
gas flow such as updraft, downdraft, cross-draft and
fluidized bed. Each gasifier has different reactions and tar
composition. According to [7], the gasification through
the downdraft gasifier is the cheapest method compare to
other types and it can produce the producer gas with less
tar content. Many researchers used the downdraft gasifier
in their experimentations. [5] have investigated the
experiment on a downdraft gasifier using wood chips and
charcoal. [3] developed an Imbert downdraft gasifier and
used 4.06 and 4.48 kg/hr of furniture woods waste for the
gasification. [8] also has tested the open core gasifier for
the thermal application and [2] have carried out the
studies on the wood gasification where it has produced a
producer gas. Normally, the gasification process uses air
as a gasifying agent. Excess char formed by the pyrolysis
process within the gasifier is burnt with a limited supply
of air (usually at an equivalence ratio of 0.25). The
product is a low-energy gas containing primarily
hydrogen and carbon monoxide diluted with the nitrogen
from the air. The heating value of the produced gas is in
the range of 3.5-7.8 MJ/m
3
, which makes it suitable for
boiler and engine applications but not for machine that
require its transportation through pipelines [9]. Due to its
simplicity, air gasification technology is being studied by
many researchers for various types of biomass. Because
air is the gasifying agent, the reactor temperature is
dependent on the air flow rate and biomass feed rate.
Very low inlet air to the system results in very low bed
temperature, which produces lower gas, and higher tar
yields. Unlike air gasification, steam gasification requires
an external heat source if steam is used as a sole gasifying
agent. Using a mixture of steam and air as a gasifying
agent is not uncommon technology and has, in fact, been
studied by several researchers. Oxygen in the air will help
in providing the required energy due to the exothermic
nature of burning biomass. The elevated temperature will
help in the devolatilization process of biomass to produce
various gas and the heating value of the produced gas is
in the 11-18 MJ/m
3
[10].
The heating value of such a
stoichiometric mixture can be calculated from the
following formula [11]:
4
2
4
2
52.9
38.2
38.21
900 ,35
800 ,10
680 ,12
CH
H
CO
CH
H
CO
g
V
V
V
V
V
V
H
(1)
Hydrogen Production by means of Mixed
Glycerol and Rice-Husk Air/Steam Gasification
P. Jittabut
*
, J. Waewsak
*
, G. Prateepchaiku
**
and Y. Tirawanichakul
***
*
Renewable Energy System Research and Demonstration Center (RERD)
Department of Physics, Faculty of Science, Thaksin University, (
Thailand
)
**
Department of Mechanical Engineering Faculty of Engineering, Prince of Songkla University,
(Thailand)
***
Department of Physics, Faculty of Science, Prince of Songkla University, (
Thailand
)
