Gasifier-based power generation: technology and economics

The paper describes a 100 kW power generation system installed at Port Blair, Andaman and Nicobar Islands, under a project sponsored by the Department of Non-Conventional Energy Sources, Government of India. The system consists of a wood gasifier utilising the waste wood from a saw mill and a diesel engine genset. The performance of the total system and its elements are presented along with economics of operation. To bring out the economics of using such renewable energy devices for power generation, some realistic situations are considered for which the effective cost of power and the pay-back period for the investment are evaluated. The economics is compared with that of a similar system of 3.7 kW capacity

Gaseous emissions using producer gas as fuel in reciprocating engines

In the recent times issues like the Green House Gas (GHG) emission reduction and carbon-trading through Clean Development Mechanism (CDM) have gained large prominence as a part of climate change. Biomass gasification is one such technology which is environmentally benign and holds large promise for the future. These technologies are currently being utilized for power generation applications at a number of industrial sites in India and abroad. This paper summarizes the work conducted using biomass derived producer gas in reciprocating internal combustion engines. The producer gas for the experimental work is derived from the well-established open top, re-burn, down draft gasification system, which is proven to generate consistent quality, ultraclean producer gas. This paper discusses the actual emission measurements in terms of NOx and CO on (a) dual-fuel engine (compression ignition engine)-using high speed diesel and producer gas fuel, (b) gas engine (spark ignited engine)-using 100% ultra clean producer gas. In the case of dual-fuel operation it is found that the NOx levels are lower compared to operations with pure diesel fuel on account of lower peak flame temperature, whereas the CO levels were higher due to combustion inefficiencies. In the case of gas alone operation it is found to be environmentally benign in terms of emissions; NOx and CO levels are found to be much lower than most of the existing emissions norms of various countries including the United States and European Union

Five-kilowatt wood gasifier technology: evolution and field experience

Various elements of an efficient and reliable 5k W wood gasifier system developed over the last ten years are described. The good performance obtained from the system is related to the careful design of its components and sub-systems. Results from extensive testing of gasifier prototypes at two national centres are discussed along with the experience gained in the field from their use at more than one hundred and fifty locations spread over five states in the country. Issues related to acceptance of the technology are also included. Improvements in design to extend the life, to reduce the cost, and to reduce the number of components are also discussed. A few variants of the design to meet the specific requirements of water pumping, power generation and to exploit specific site characteristics are presented

Characterization and Applications of Non-Magnetic Rotating Gliding Arc Reactors - A Brief Review

Gliding arc discharge (GAD) reactors are known for high energy efficiency and good chemical selectivity compared to non-thermal plasmas such as glow discharge, corona and dielectric barrier discharge. Reported literature identified that planar diverging GAD have non-uniform gas treatment (e.g. only 20% of gas processed by plasma depending on electrode configuration). Further requirement of minimum limit gas velocity to drag the arc results in lower gas residence time. This paper attempts to investigate the GAD performance and preliminary studies to overcome some of the identified drawbacks, by using only fluid mechanics without magnetic field (rotating gliding arc (RGA)) inside the plasma reactor developed in various research laboratories. This article discusses the applications of GAD and also focuses on bringing out the performance and comparing with the results from the existing non-magnetic rotating gliding arc reactors. The paper also summarizes results from literature in such reactor designs

Portable single-pan wood stoves of high efficiency for domestic use

We describe and evaluate here certain new designs for single-pan wood stoves of high efficiency. The novelty in the design consists chiefly in the use of improved geometries for the combustion chamber and the vessel support. Extensive tests on water boiling and cooking demonstrate efficiencies exceeding 40%; these high values are attributable to stove operation at near stoichiometric conditions. The configuration termed Swosthee is among the most efficient stoves available to date, and is able to burn wet wood under partial loading with little accompanying smoke. Two versions of the same basic design provide inexpensive stoves that retain to a large extent the advantages of the original design like the generation of pollutants at low levels in the flue gases and the ability to handle wet wood. For the proposed designs the dependence of their cooking efficiency on vessel size has been obtained. These are reflected in terms of specific fuel consumption (whose variation is a function of vessel size). The present designs, when compared to other currently available improved stove designs like Priyagni, Tara, the Tamil Nadu Stove and the ASTRA three-pan stove, are better with respect to at least one of the following criteria-efficiency, cost, CO emission and portability. The stoves are presently being disseminated in small numbers

Biomass gasification technology - a route to meet energy needs

The paper addresses a distributed power generation system that has evolved at the Indian Institute of Science, Bangalore. The technological and field-related experience pertaining to open top re-burn down draft biomass gasification system coupled with the internal combustion engine or thermal device are brought out. The gasifier reactor design uses dual air entry - air nozzles and open top to help in establishing a thick high temperature zone to remove the contaminants in the product gas; a gas clean-up system to further refine the gas to ultra-pure quality. These elements are integrated with other sub-systems, namely feedstock preparation, ash handling, water treatment, process automation and other accessories to form an Independent Power Producer. Based on this technology there are over 30 units operating in India and abroad, with an accumulated capacity of over 20 MW. Over 80,000 h of operation of these systems have resulted in a saving of about 350 tons of fossil fuel, implying a saving of about 1120 tons of CO2 - a promising candidate for Clean Development Mechanisms (CDMs), other than reduction in toxic gases like NOx and SOx

Results of an Indo-Swiss programme for qualification and testing of a 300-kW IISc-Dasag gasifier

The paper describes the performance and operational experience in India on a high efficiency, low tar, woody biomass gasifier developed at Indian Institute of Science, Bangalore. This development is also of interest to Switzerland, which has a substantial potential of biomass energy. The test scheme included measurements on tar and particulates and the effluents along with necessary measurements for the mass and energy balance. The results indicate a low tar level to meet the engine specifications and the effluents issuing out of the system could be treated using simpler techniques, as the levels are low

Green electricity from biomass fuelled producer gas engine

In the recent times issues like the Green House Gas (GHG) emission reduction and carbon-trading through Clean Development Mechanism (CDM) have gained large prominence as a part of climate change. Biomass gasification is one such technology which is environmentally benign and holds large promise for the future. These technologies are currently being utilized for power generation applications at a number of industrial sites in India and abroad. In India there are nearly 4 MWe equivalent power plants which are based on IISc's open top reburn down draft biomass gasification technology. In the field of power generation, there has been substantial effort in the development of producer gas engine; systematic experimental and modeling studies followed by long duration field monitoring. As a part of this effort, a gas carburetor has been designed for producer gas fuel and forms a part of the power package. The essential requirements of gas conditioning equipment are packaged to meet the engine quality gas as a power plant. Currently there are more than 3.0 MWe equivalent gas engines operating in the field; of this one is deployed in an Energy Service Company (ESCO), which sells green electricity to a textile industry. The company is located at Metupalyam in South India, near the city of Coimbatore. The power plant is configured with a 150 kg/hr gasifier coupled with a turbo charged after cooled Cummins make (GTA855G) gas engine. The plant is also provided with an effluent treatment plant and an engine-waste-heat based biomass drier. The plant commissioned in September 2003 has successfully completed over 7500 hours of operation, generating about 0.7 million units, thus saving a net CO2 of about 0.7 million Tons against a fossil fuel technology. The plant operates on a continuously to meet the end use requirement over 275 hours non stop operations hours of operation. The power plant utilizes a weed namely Julifora Prosopis which is abundantly available in the southern part of India and converts into green energy; additionally generates value added product namely partially activated carbon-Iodine no. of 400-450. The paper reports specific biomass consumption and engine emission monitored over long duration. The specific biomass consumption is measured to be within 1.1 ± 0.1 kg/kWh with an overall efficiency of 22-24%. It is also found to be environmentally benign in terms of emissions; NOx and CO levels are found to be much lower than most of the existing emissions norms of various countries including the United States and European Union. The paper also highlights results from other installations using this technology. Keywords: open top gasifier, producer gas engine, CDM technology

Scientific and technological aspects of fixed bed biomass gasification

In recent years new emphasis has been placed on problems of the environmental aspects of waste disposal, especially investigating alternatives to landfill, sea dumping and incineration. There is also a strong emphasis on clean, economic and efficient processes for electric power generation. These two topics may at first appear unrelated. Nevertheless, the technological advances are now such that a solution to both can be combined in a novel approach to power generation based on waste-derived fuels, including refuse-derived fuel (RDF) and sludge power (SP) by utilising a slagging gasifier and advance fuel technology (AFT). The most appropriate gasification technique for such waste utilisation is the British Gas/Lurgi (BGL) high pressure, fixed bed slagging gasifier where operation on a range of feedstocks has been well-documented. This gasifier is particularly amenable to briquette fuel feeding and, operating in an integrated gasification combined cycle mode (IGCC), is particularly advantageous. Here, the author details how this technology has been applied to Britain's first AFT-IGCC Power Station which is now under development at Fife Energy Ltd., in Scotland, the former British Gas Westfield Development Centre