Pyrolysis

There are many pyrolysis technologies in the market and they differ deeply accordingly to their operational conditions.

The most important differences between pyrolysis technologies regard the reactor type (fluidized bed, fixed bed, rotating drum), the residence time (flash pyrolysis 1s, fast pyrolysis 2s, slow pyrolysis 40min-1h) and the temperature (low 400°C, medium 600-800°C, high >800°C).

The differences in operation conditions result in the generation of different products. For example, the carbonization, is a type of pyrolysis that generates mainly charcoal. Under other conditions it can generates mainly a liquid fuel called biooil and under other conditions gas is the main product, called syngas.

Below are listed some of the Slow Pyrolysis Plants in operation in the world:

The Slow Rotary drum pyrolysis received a very positive evaluation from the Department of Trade and Industry (DTI) of the United Kingdom and was evaluated as the best Waste to Energy technology by the Italian National Research Council (CNR), very distinguished institute from the MIUR Italian Minister. 

Some of the features listed by CNR are described below (Department of Energy and Transport - National Research Council (Italy) - Il ciclo integrato dei rifiuti in Campania: Prospettive e possibilità reali di applicazione):

  • The pyrolysis systems, operating in the absence of air, allow superior thermodynamic efficiencies and better emission results through the removal of harmful elements before the combustion;
  • This technology is the only example of process (among the technologies evaluated) that is capable of treating the unsorted waste with no previous treatment. This feature allows the reduction of the waste management chain in one process and reduce the dependency on landfills to a minimum;
  • Another positive feature of this technology is the fact that the syngas produced is sensibly richer than the one obtained using gasification, as it does not use any form of oxidation. These features make the process even more flexible and appropriated for the energy recovery;
  • The modern pyrolysis systems developed for the treatment of MSW are capable of guaranteeing very interesting global results, superior to other technologies of transformation. This is the case of many of the cited plants, developed by renowned companies worldwide, not only because this technology convinced these companies, but because effectively this is the most robust one, considering the flexibility to handle different waste compositions and when considering the costs of disposal, the one that can allow the biggest reduction in MSW disposal costs;
  • It is important to highlight the big number of plants of this kind in countries like Japan, a country very regardful of the acceptance of Waste to Energy by the public, especially when considering the high population density and its geographic constraints. This features imposed choices that could limit the pollutant emissions from the MSW disposal and transport, reducing the number of steps for the waste management system;
  • The pyrolysis plants can have small dimensions, being installed in small buildings inside industrial areas;
  • The low environmental impact allows the local public acceptance;
  • Allowing relatively small units, each community can be responsible for the MSW produced by its own, leading to a reduction in the MSW production and a more effective sorting;
  • For big cities, it is possible to use more than one module side by side in existing industrial areas;
  • The very simple and modular construction with local assemblage and reduced civil works (normally the most expensive and time-consuming part of an incinerator) allow short delivery and installation times;
  • Economic feasibility and fast return on investment;
  • Can be used also for treating some kinds of industrial waste;
  • Grate global efficiency in converting waste to heat, and consequently to electricity;
  • The system reduces the dependency on landfills;
  • The flexibility of the technology allows also the treatment of clinical waste, auto fluff, sewage sludge and biomass in general.