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Combined heat and power from the intermediate pyrolysis of biomass materials offers flexible, on-demand renewable energy with some significant advantages over other renewable routes. To maximise the deployment of this technology an understanding of the dynamics and sensitivities of such a system is required. In the present work the system performance, economics and life-cycle environmental impact is analysed with the aid of the process simulation software Aspen Plus. Under the base conditions for the UK, such schemes are not currently economically competitive with energy and char products produced from conventional means. However, under certain scenarios as modelled using a sensitivity analysis this technology can compete and can therefore potentially contribute to the energy and resource sustainability of the economy, particularly in onsite applications with low-value waste feedstocks. The major areas for potential performance improvement are in reactor cost reductions, the reliable use of waste feedstocks and a high value end use for the char by-product from pyrolysis. Keywords: bioenergy system; intermediate pyrolysis; combined heat and power; technoeconomic evaluation; environmental life-cycle analysis1 Introduction BackgroundOver ten percent of total world primary energy supply in 2013 (13.5 billion tonnes of oil equivalent) was produced from biomass sources, making biomass by far the most important renewable energy source [1,2]. In a global context, the use of biomass to generate power and heat has been a key element in reducing fossil fuel consumption and combating climate change. In the UK, the government has projected bioenergy to contribute over 35% of the total renewable energy production (including non-domestic heat and transport) needed to meet the target of 15% primary energy generation from renewables by 2020 [3].Biomass as an energy source is abundant, predictable and non-intermittent, and, importantly, is © 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

An experimental study of entrained flow, air-blown cogasification of biomass and a coal−coke mixture has been performed in order to evaluate the effect of the relative fuel/air ratio (ranging between 2.5 and 7.5), the reaction temperature (ranging between 750 and 1150 °C), and the biomass content in the fuel blend on the producer gas composition and the process performance. Dealcoholized grape marc, a waste coming from the wine industry and with high potential in the south-central regions of Spain, has been chosen as biomass fuel. On the other hand, the coal−coke blend (composed of a low-rank autochthonous coal and a solid residue from refineries) is an abundant fossil fuel which is used in a commercial IGCC power plant. The results obtained show that an increase of the biomass content in the fuel blend upgrades the producer gas quality and improves the cold gas efficiency. Some hints of synergy between biomass and coal−coke have been found, especially at low fuel/air ratios and low reaction temperatures, which might be mainly related to the content and composition of the blend ash (especially due to the catalytic effect of Ca and K coming from the biomass ash, and the Fe, Ni, and Zn contents of the coal−coke ash). However, thermogravimetric analyses have not provided enough information about possible interaction between biomass and coal−coke.

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Because of the importance that the energy use of agricultural and forestry wastes has acquired over the last years, results for the laminar flame speed of producer gas coming from the gasification of lignocellulosic biomass are presented in this work. These results have great interest for the development of combustion models that provide significant information to be used as a tool for the optimization and design of specific internal combustion engines. The CHEMKIN software, together with the GRI-Mech chemical reaction mechanism, has been used to compute the laminar flame speed for different producer gas compositions, different values of pressure and temperature, and different producer gas/air equivalence ratios. The results have been compared with those obtained in an experimental combustion bomb, as well as with the laminar flame speed obtained for conventional fuels, showing that the flame speed of the producer gas is less than that of isooctane but greater than that of methane. A sensitivity analysis shows the influence that the dominant chemical reactions and species have on the laminar flame speed of producer gas at different producer gas/air equivalence ratios. Although good qualitative agreement has been found, some differences between experimental and modeled results at high pressure and temperature are due to the instabilities in the experimental flame.

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