Resumo:
Minas Gerais is the biggest charcoal producer in Brazil. This production happens in carbonization
kilns that emit waste gases to the atmosphere, wasting useful energy and causing an environmental
impact. In this work, an evaluation of the electricity generation potential from the effluent gases of
the charcoal production in Minas Gerais was carried out using different electricity conversion
technologies. A survey of charcoal producers in the State and their production was conducted in order
to calculate the energy potential available in 2020 with a projection until 2030. For the electricity
generation studies, three technologies were considered, namely: The Steam Rankine Cycle (SRC),
the Organic Rankine Cycle (ORC) and the Externally Fired Gas Turbine (EFGT). For each
technology, the efficiencies were calculated and applied for each of the previously surveyed
producers. Efficiencies ranged from 5% to 24% depending on the type of technology power, ranging
from 100kW to 2000kW. Maps of the power generation potentials in Minas Gerais were created,
showing a concentration in the North and Northeast regions of the state. The highest power generation
potential for the state was 1348 GWh/year using the ORC cycle with regeneration, superheating and
n-decane as the working fluid. An economic analysis was also made, taking into account auctions for
the energy sale in the energy market, together with a sensitivity analysis for each variable considered:
Power, energy sale price, minimum attractiveness rate of return, taxes, plant operation time, and
capital expenditure. The results demonstrate that the current technical and economic scenarios are not
favorable for the implementation of electricity generation plants based on waste heat recovery from
gases in charcoal production plants in the State of Minas Gerais, making feasibility in plants smaller
than 10 MW practically impossible over a 10-year horizon. All technologies had energy sales prices
above 100 US$/MWh, which is higher than the average of the last 3 years. However, the technological
development in the charcoal production kilns and electricity conversion technologies, combined with
an economic incentive based on environmental benefits, may provide an improvement in this scenario
in the future.
