RICE HUSK GASIFIER STOVE

Abstract

The stove basically is a top-lit updraft type(T-LUD) which follows the principle of gasification converting the raw rice husk into combustible gases resulting the luminous blue flame. With the thermal efficiency of nearly 20%, this gasifier stove can be fabricated using the locally available materials. Since the smoke and tar emission was found to be very minimal, it can be better alternative than the other traditional stove.

Introduction

It is estimated that about 40% of the global population relies on combustion of solid biomass for household energy need. The incomplete combustion process gives out smoke containing carbon monoxide and other harmful gases. Exposure to CO and other harmful gases emitted from incomplete combustion of solid biomass leads to numerous health effect and environment pollution.

Biomass currently covers approximately 10% of the global energy supply. Rice husk is an agricultural bio-waste having high potential for power generation. The gas stoves using rice husk were started from An Giang, province of Vietnam but the feasibility in terms of technology, social economy and environmental benefits were not concerned at that time. Later, Belonio started work relating to rice husks and the gas stove in 2003 at a time when there were high fuel prices. He then modified previously used stove into gasifier stoves. In Asian countries, rice husk is partly used as an energy source for cooking, heating and other purposes. It is estimated that worldwide 38 to 57 million tons of rice husk is available for energy generation.

Energy consumption and utilization pattern in Nepal differs from industrialized country. In Nepal, biomass accounts for approximately 87.1% of the total energy use. According to the census 2011, about two-third of the total households (64%) uses firewood as usual source of fuel for cooking followed by LPG (21.03%), cow dung (10.38%). Nepal have the potential of producing 0.86 million tons of rice husk. So, keeping in view of problems related to availability and price of LPG; throughout the world, energy consciousness has been developed and researchers are widely participated for the utilization of available resources and find the sustainable device with sustainable material (rice husk in context of Nepal). The different types of the gas stoves used in Nepal are: mud stove, metallic stove, wood stove and they have the efficiency less than 20%. But Rice husk gasifier stove is expected to have the efficiency of near about 25%.

Burning of solid biomass in traditional way produces large amount of smoke, this is termed as indoor pollution. Nepal has many households that are suffering from indoor pollutions. The few methods for increasing efficiency using rice husk and reducing indoor pollution may be:

1. The use of improved stoves such as gasifier stove over traditional stoves.

2. The quality of fuel being used can be upgraded by turning them into briquets and drying the solid biomass before burning the fill.

Significance and Scope:

The rice husks gas stove technology was found to have the following advantages, not only to the user but to the public as well:

➢ It is good replacement for LPG stove, in terms of fuel saving and quality of flame (i.e. luminous blue flame) produced during cooking. By direct energy conversion, about 23 tanks of 11-kg LPG fuel can be replaced by a ton of rice husks.

➢ It will significantly reduce the cost of household spending on conventional fuel sources such as electricity, kerosene, wood and wood charcoal.

➢ It will minimize the problem on household disposal which contributes a lot on environmental pollution.

➢ It will help reduce the carbon dioxide emission in air brought about by the excessive burning of wood and other biomass fuel in the traditional cook stoves, which consequently in the “greenhouse effect” into the atmosphere.

➢ It will help to prevent the deforestation to produce wood fuel, minimizing problems related to the environments.

➢ It doesn’t produce smoke and has stable fire without a tar like residue which is not harmful for human health.

Limitations:

1. Difficult to refill rice husk during the operation of gasifier, once the rice husk is finished in the reactor.

2. Difficult to get the required air from secondary holes as per the air supplied from fan.

3. Only applicable for those areas where the rice husk is easily available.

Scenario of Biomass in Nepal

Today major population depends upon non-renewable sources.70% of energy are obtained through firewood. Less than 1% people uses renewable sources. Most of the primary energy (about 70%) represents solid fuels used in the residential sector etc. And about 95% of the biomass is used for cooking and heating purposes. However, its use is inefficient and poses a threat to the country’s forests.

The kinds of Biomass available in Nepal are: -

➢ Wood products: -non-timber, tree removals, sawmill and other wood manufacturing residue dedicated forest

➢ Solid waste: -municipal solid waste, hospital wastes

➢ Landfill gas and Biogas: -methane, fermented gas

➢ Agricultural products: - rice husk, fibers, raw materials

The Types of Biomass Fuels Available in Nepal are: -

➢ Woody fuels: -deadfalls, woody crops, woody wastes

➢ Forestry: -forest debris

➢ Mill Residues: -rice husk, saw-dust

➢ Agricultural Residues: -rice husk, straw

➢ Dedicated Biomass Crops: -willow, maize, millet

➢ Chemical Recovery Fuels: -polymer waste, textiles

➢ Dry Animal Manure: -dry dung

➢ Wet Animal Manure: -dairy manure slurry