Abstract
A thermodynamic model of a combined heat and power (CHP) plant, fed by syngas produced by dry olive pomace gasification is here presented. An experimental study is carried out to inform the proposed model. The plant is designed to produce electric power (200 kWel) and hot-water by using a cogenerative micro gas turbine (micro GT). Before being released, exhausts are used to dry the biomass from 50% to 17% wb. The ChemCad software is used to model the gasification process, and input data to inform the model are taken from experimental tests. The micro GT and cogeneration sections are modeled assuming data from existing commercial plants. The paper analyzes the whole conversion process from wet biomass to heat and power production, reporting energy balances and costs analysis. The investment profitability is assessed in light of the Italian regulations, which include feed-in-tariffs for biomass based electricity generation.
Highlights
Mediterranean countries are responsible for a large part of the world olive oil production.The environmentally friend disposal of the olive pomace requires the implementation of waste-to-energy strategies through pomace gasification
Suggests the following improvements to the downdraft biomass gasification model: (i) modeling three cascade reactors, simulating respectively the pyrolysis, oxidation and reduction zones; (ii) separation of a fraction (5% by mass) of the inlet carbon content, in order to take into account the unavoidable losses occurring in the gasifier due to char formation; (iii) bypass of a fraction of the methane formed during the pyrolysis directly to the reduction outlet, in order to reflect the unavoidable losses and the impossibility to achieve a complete equilibrium composition during the gasification
The whole plant is composed of five sections, as reported in the boxes of Figure 1 where the components are indicated in circles and the streams in squares
Summary
Mediterranean countries are responsible for a large part of the world olive oil production. A proper solution is to process the crude olive pomace (COP) aiming at obtaining dry olive pomace (DOP) as a fuel. The extraction of pomace oil from COP allows obtaining the DOP as a by-product (about 10% wb), generally used for energy conversion in CHP or thermal plants. Thermo-economic approaches can be usefully employed to compare operation strategies and profitability of small scale CHP plants fed by syngas [9]. In [11] a ChemCad model of a biomass gasification plant coupled to a micro GT is validated through experimental data. In this paper we adopted ChemCad to model the COP to syngas gasification process. A review of gasification technologies and modelling approaches is proposed, and successively a description of the CHP plant under investigation is presented. The energy balance of the system as resulting from the simulation, informed by specific experimental tests, and the economic profitability of the investment in the Italian legislative scenario are presented, and results are discussed in the last section
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