Fossil fuel has been the primary source in the last two decades to meet the thermal energy demand of small as well as large industries. The numbers of small-scale industries that use fossil fuels to meet the heat requirements are quite large. In such industries constant efforts are made to increase the efficiency of combustion devices to meet both efficiency and emissions standards. Over the years, many of the solid fuel based devices have been converted to petroleum-based fuels due to the availability and the compactness of the combustion system without serious concern on the economics of operation. With the present escalation of cost of petroleum fuels, the overall economics has been affected. Economics along with the environmental considerations has resulted in looking at alternate sources of energy. Industries have adopted the use of petroleum-based fuels for various applications, apart from generating electricity using internal combustion engines. Some of the applications are the low temperature requirements like, drying of various food and non-food items, hot air for specific process requirements, etc. high temperature requirements are in boilers for steam generation, thermic fluid heaters, furnaces in heat treatment industries, steel processing, ceramic sector, etc. This has led to the use of petroleum fuels for stationary applications, which other wise could address the transport sector. A significant part of fossil fuel is used for industrial applications to meet the thermal energy requirements. Further, the petroleum fuel usage has an impact on the Greenhouse gas emissions. Combustion of petroleum fuels degrades air quality with adverse impacts. It leads to emission of pollutant such as particulates, SO2, NOx, CO and GHG (largely CO2).
Biomass as an energy source
Even though many of the above mentioned applications could be addressed using biomass, the industrial sector has not taken note. With the adaptation of gasification technology, nearly all the advantages of using petroleum fuel as a thermal source of energy can be availed. Further, the use of biomass has an economic advantage along with environmental benefits.Biomass has been one of the main energy sources ever since the dawn of civilization although its importance is dwindling after the expansion in use of oil and coal in the late 19th century. The recent resurgence of interest in biomass energy in important countries of the world is not surprising considering the benefit it offers in the current context. It is renewable, widely available, carbon neutral and has the potential to provide significant productive employment. Power and liquid fuels could also be produced by the gasification route using energy plantations grown on non-agricultural lands. The present methods for utilization of these resources are highly inefficient. On the other hand, utilization of the residues through gasification route becomes economical and promising for thermal and power needs of rural areas and small-scale industries. This will also reduce the pressure on the worsening fuel wood situation. Biomass is the most convenient form of renewable energy because the built-in storage technologies based on stored energy are most suitable for energizing irrigation pump-set and industrial thermal applications.
Biomass gasification
Biomass gasification is basically conversion of solid biomass such as wood waste, agricultural residues etc., into a combustible gas mixture normally called “Producer gas” (or Low Btu gas). The solid biomass is burnt in the presence of limited air or oxygen to produce a low or medium calorific value gas. Partial combustion process occurs when air supply is less than adequate for combustion of biomass that contains carbon, hydrogen and oxygen and oxygen molecules and complete combustion would produce carbon monoxide as well as hydrogen also, which are both combustible gases. Solid biomass fuels are usually inconvenient, have low efficiency of utilization and can only be used for certain limited applications. Combustion is the normal conversion process for direct thermal use in cooking, heating space and water, or generation of steam with low efficiency. Conversion of the same biomass to a combustible gas mixture (producer gas) removes most of these problems associated with the use of solid biomass fuels. While conversion to gas results in loss of energy of up to 25 percent, use of gas can be highly efficient and hence overall efficiency could be very high. Also it can be employed at any scale and hence is ideally suited for decentralized application whether for shaft power, electricity or thermal energy applications.Number of thermal applications of gasifier systems has shown adequate and immediate promise. These applications involve diverse situation: where biomass might already be in use with traditional technologies; situations where biomass may not be currently in use but is available as a by-product; and situations where biomass may need to be procured for a switch over from fossil fuel. However even in situations where thermal energy is currently being provided by bio-resources, careful study of the application and effective development of application packages becomes necessary.
Use of boilers in textile industries
Textile industry can be classified according to the fiber being processed or the processing operations. In most of the knitted garment industries, thermal processing is one of the steps involved in the production chain. For thermal processing such as heating, boiling, hot air production, boiler operation etc. direct burning of wood is employed. Locally made boilers are used for the production of steam. Steam is used for thermal processing of clothes. They use various types of boilers ranging from steam production of 100 kg/h to 1000 kg/hr at moderate promises.
Retrofitting gasifier with boiler
Most common fuels used in the boilers are wood, diesel or electricity. Direct burning of wood involves less efficient processes and other fuels like oil, diesel involves higher cost of operation, which increase production cost. Burning of firewood by conventional method is very inconvenient and inefficient. Hence there exists scope to introduce gasification process having a fairly high efficiency. In thermal gasifiers, biomass like wood waste is burnt in controlled conditions and fuel gas is produced. This wood gas can be burnt in specially designed burners to get intense flame. Adopting gasifier of fairly high efficiency can reduce the cost of fuel. These gasifiers can be retrofitted with industrial boilers for thermal requirements.
