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Improvement of bio-fuels combustion in boiler and in gas turbines


The objective is:

- to obtain practical data on the production of dedicated bio-energy crops (i.e. sweet sorghum) and on the cost of the crops delivered on the site of utilisation;

- to evaluate the technico-economic potential of atmospheric gasification technology for advanced power generation cycles;

- to evaluate alternatives for pyrolysis oil upgrading and define the conceptual design of a pilot plant;

- to verify the technical problems rising from the use of new fuels in power generation systems;

- to evaluate the pollution characteristics of several bio-fuels.
An advanced small size turbogenerator for decentralized production of electricty is being developed. Some components of the foreseen pilot plant in particular a heat exchanger able to regnerate the thermal cycle of the plant, are being worked upon. Market analysis for the engine is also being undertaken.

Some overall calculations have been done to obtain a rough dimensioning of a metallic, crossflow, recuperator to be used on the 400 kWe turbogenerator. The high temperature to be obtained for the compressed air (700 C), coupled with the gas temperature only 50 C higher, require very high recuperator efficiency. As a consequence, the heat exchanger dimensions are big when compared with the turbine ones. Obviously costs are high too. The results seem to address the necessity for a slight decrease of the required efficiency (eg using a temperature difference of at least 100 C between hot flue gases and the temperature achieved by the compressed air) to decrease the recuperator dimensions and costs. Moreover, especially if a lower efficiency is possible, it may be more convenient to choose a ceramic recuperator, due to the higher thermal limit in comparison with the metallic one, and possibly lower costs by means of a medium large series production.

Market analysis has shown that the turbogenerator under development has good prospects in the Italian market provided that technical solutions to the problems lead to good availability and operability with installation costs less than those for typical gas fired single cycle plants.
Activity no1: Feedstock production, harvesting, storage, pretreatment and drying.

a) Plantations in 3-4 different regions in Italy at a level of about 10 ha of several energy crops.
b) Harvesting operations of these biomass crops.
c) Sugar juice/bagasse separation of sweet sorghum.
d) Evaluation of alternatives about optimizing this operation and to improve the global system energy balance.
e) Evaluation of the logistics for the transportation and optimization of the dispersed and large size final storage system.

Activity no2: Biomass gasification tests.

Gasification of biomass for power generation allows the adoption of gas turbines or advanced combined cycles (STIG, ISTIG, HAT cycles) where the gas turbine is always the key element. The experimental activity will be implemented in one of the two recirculating atmospheric fluidised bed gasifier for RDF constructed by Ansaldo-Aerimpianti (Studsvik technology) in Greve in Chianti.

Activity no3: Pyrolysis oil upgrading.

a) Technical and economical analysis of the possible hydro-treatment processes for bio-crude oil.
b) Definition of the steps to take in order to prepare the future design of a middle size hydro-treatment pilot plant of about 100 kg/hr.
c) Depending on the results of point b), assessment and preliminary design of the pilot plant (about 1 kg/hr).

Activity no4: Bio-fuel utilization and environmental impact.

An experimental activity will be implemented on the utilization of a variety of bio-fuels. They will include: bio-crude oil, oil/ethanol emulsions and bio-ethanol (low grade) from sweet sorghum. The pollution characteristics of the several bio-fuels utilized will be evaluated.

The above tests will be carried out utilizing the availability of the various bio-fuels and test facilities.


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Ente Nazionale per l'Energia Elettrica SpA (ENEL)
Via Andrea Pisano 120
56100 Pisa

Participants (1)

Place De L'universite 1