PRODUCT
What is rice husk and what are its major products?
The rice husk, also called rice hull, is the coating on a seed or grain of rice. It is formed from hard materials, including silica and lignin, to protect the seed during the growing season. Each kg of milled white rice results in roughly 0.28 kg of rice husk as a by-product of rice production during milling.
Common products from rice husk are: solid fuel (i.e., loose form, briquettes, and pellets), carbonized rice husk produced after burning, and the remaining rice husk ash after combustion.
Rice husk in its loose form is mostly used for energy production, such as combustion and gasification. Combustion is the process of burning carbon in the rice husk, which emits CO2 and generates heat energy for further use. One of the most efficient uses of this by-product is its direct combustion without the need for a heat exchanger with a proper furnace to generate heat for drying paddy. Gasification is the process of converting rice husk to synthesis gas (syngas) in a gasifie
r reactor with a controlled amount of air. Syngas can be used as fuel for drying and cooking or in a cogeneration system to produce electricity.
Rice husk briquettes and granule are produced using densification to increase the density of materials and their combustion performance. These densified rice husks are mainly used in industrial boilers as a substitute for fossil fuel.
Rice husk ash is the remaining by-product after combustion is done. The amount of carbon remaining in ash depends on the combustion performance (i.e., complete or incomplete combustion). Rice husk ash can be used as a soil amendment and as additive in cement and steel, among others. However, only small amounts compared to the total rice husk production are used for such purposes.
Carbonized rice husk is produced by thermal decomposition of the rice husk under a limited supply of oxygen (O2) and at relatively low temperatures (less than 700°C). Biochar produced from carbonization can be used as soil amendment, for processing fertilizer, and as activated carbon, etc.
The term biogenous silica also known as rice husk ash indicates the products’source. Biogenous silica is a natural, renewable raw material.
Rice husks are used in modern biomass ower plants as a quality-controlled source of energy. Hereby, the raw material is burned in a carbon-neutral manner. this means that during combustion, no more CO2 is released than the rice plant absorbed from the atmosphere during its growth - an aspect that is gaining in importance for raw materials in the future.
Characteristics of the rice husk
Produced during rice milling, the rice husk is already dried and accumulated at the factory. The specific weight of uncompressed rice husk is about 100 kg/m3.
The physical and chemical properties of rice husk ash are dependent on the components of the combustion process, such as combustion type, feeding type, temperature, residence time, and availability of oxygen (aerobic or anaerobic).
The characteristics of rice husk compared with other solid fuels can be summarized as follows:
- Its high silica content causes excessive wear to parts of processing machines, such as conveyors or grinders, and hampers digestibility in livestock. The content of volatile matter in the rice husk is higher than in wood and much higher than in coal; whereas, fixed carbon is much lower than in coal. Ash content in the rice husk is much higher than in wood and coal, which causes barriers in energy conversion.
- The high content of ash, alkali, and potassium causes agglomeration, fouling, and melting of the parts of combustors or boilers.
Utilization of the rice husk
Rice husk was long considered a waste from the rice milling process and was often dumped and/or burned. But because it can be easily collected and is cheap, some amount of rice husk has always been used as an energy source for small applications, such as for brick production, for steam engines and gasifiers used to power rice mills, and for generating heat for rice dryers. The high silica content of rice husk ash makes it a good additive for the steel and concrete industries. To a lesser degree, rice husk ash is used as soil conditioner, activated carbon, insulator, and others. More recently, creation of electrical power on a small to medium scale—up to 5 megawatts—has been piloted throughout Asia, with some promising approaches but also some demonstrated limits. Failure was mostly due to feedstock supply problems once the formerly free waste rice husk becomes a traded commodity and due to logistical problems and the high cost when transport distances become too large.
RICE HUSK ASH
Rice husk ash (RHA) is an abundantly available and renewable agriculture by-product from rice milling in the rice-producing countries. Approx 22 % of the weight of paddy is received as husk . This husk is used as fuel in the rice mills to generate steam for the parboiling process. The balance amount is converted into ash during the firing process which is known as rice husk ash ( RHA ). It has the highest proportion of silica content among all plant residues.
The carbon neutral green additives for infrastructure industry.
the present low carbon of rice husk ash or Rice Hull is high demand in many
industries in the world. The physical of carbonize rice husk ash will has a gray or white color with their important specification is high silica with very low carbon or almost none in carbon sometimes.
With an extraordinary for binding property of carbonized rice husk ash is a unique, therefore the suitable industries which will use it, are steel and cement industries.
Rice Husk is a waste material obtained from the milling process of paddy which produces the husk residues. It looks golden yellow, light yellow, reddish brown depending on the rice species.
Rice husk consists of organic matter and silica. Organic matter is composed of about 51% carbon, 42% oxygen, the rest is hydrogen and nitrogen. Silica is found abundantly on the outer surface of the rice husk, thus making the rice husk high hardness and can be used. can be abrasive material
