Plant for the production of activated carbon and electric power from the gases originated in gasification processes

Abstract

The development of the countries involves a high energy demand; however, the energetic resources used by the moment are not renewable. Events like the energetic crisis of 1973, the continuous geopolitic clashes in energetic resource-rich areas, and the global environmental deterioration as a consequence of the industrial activity taking place in last century, make obvious the need of searching new sources of energy [1]. One of these sources is the obtainment of energy from biomass exploitation. The use of this raw material involves advantages in the emission of low quantities of contaminants to the atmosphere and its renewable character. Until now, the main drawback of this source is its lack of viability when trying to obtain electric power from biomass, due to the use of systems composed of a boiler and a steam turbine (which offer low operative flexibility), which are not rentable in such a competitive market as it is, currently, the energetic one. Nowadays, the use of internal combustion engines, combined with biomass gasifiers, allows rapid connection–disconnection of the plant (aproximately of five minutes), which confers a big flexibility to the system and, as a consequence, a better exploitation of the plant in maximum energetic consumption hours. It also has the advantage of establishing a co-generation system since the gases are generated at a high temperature, 800 °C [2]. With this view, the aim of this work has focused in the re-design of a gasification plant for the production of activated carbons, from biomassic residues, for the energetic exploitation of the combustible gases produced during the pyrolytic process (H 2, CO, CH 4, C 2H 2, C 2H 4, C 2H 6), since these gases are currently burnt in a torch in the plant. The idea of designing the activated carbon production plant arose from the need of managing the biomass residues (olive wastes) generated by the firm Euroliva-Azeites e Oleos Alimentares SA, located in Alto Alentejo, in the city of de Vale do Peso, Concelho de Crato. This firm collects the residues produced in the olive oil mill of Concelho do Crato and then, in the plant, makes the last obtainment of less-quality olive oil, which gives rise to a high production of olive waste. The production of this residue is 250 tons/day, which involves an annual production of 87,500 tons of residues that have to be removed [3]. The activated carbon production plant, already built, has a processing capacity of 250 kg h − 1 of residual biomass, with a yield close to 16% in carbon production. According to the plant capacity and the generated gases potential, a thermal power of 1.05 MW and, considering a process global output of 25%, an electric power of 250 kW would be obtained.