Francesco Patuzzi

Agro-industrial waste to solid biofuel through hydrothermal carbonization

In this paper, the use of grape marc for energy purposes was investigated. Grape marc is a residual lignocellulosic by-product from the winery industry, which is present in every world region where vine-making is addressed. Among the others, hydrothermal carbonization was chosen as a promising alternative thermochemical process, suitable for the treatment of this high moisture substrate. Through a 50 mL experimental apparatus, hydrothermal carbonization tests were performed at several temperatures (namely: 180, 220 and 250 °C) and residence times (1, 3, 8 h). Analyses on both the solid and the gaseous phases obtained downstream of the process were performed. In particular, solid and gas yields versus the process operational conditions were studied and the obtained hydrochar was evaluated in terms of calorific value, elemental analysis, and thermal stability. Data testify that hydrochar form grape marc presents interesting values of HHV (in the range 19.8-24.1 MJ/kg) and physical-chemical characteristics which make hydrochar exploitable as a solid biofuel. In the meanwhile, the amount of gases produced is very small, if compared to other thermochemical processes. This represents an interesting result when considering environmental issues. Statistical analysis of data allows to affirm that, in the chosen range of operational conditions, the process is influenced more by temperature than residence time. These preliminary results support the option of upgrading grape marc toward its energetic valorisation through hydrothermal carbonization.

Hydrothermal carbonization of off-specification compost: A byproduct of the organic municipal solid waste treatment

The possibility to apply the hydrothermal carbonization (HTC) process to off-specification compost (EWC 19.05.03) at present landfilled was investigated in this work. The aim was to produce a carbonaceous solid fuel for energy valorization, with the perspective of using HTC as a complementary technology to common organic waste treatments. Thus, samples of EWC 19.05.03 produced by a composting plant were processed through HTC in a batch reactor. Analytical activities allowed to characterize the HTC products and their yields. The hydrochar was characterized in terms of heating value, thermal stability and C, H, O, N, S and ash content. The liquid phase was characterized in terms of total organic carbon and mineral content. The composition of the gas phase was measured. Results show that the produced hydrochar has a great potentiality for use as solid fuel.

Common reeds (Phragmites australis) as sustainable energy source: experimental and modelling analysis of torrefaction and pyrolysis processes.

The aim of this study is to apply advanced analytical techniques and kinetic modelling to common reeds (Phragmites australis) to characterize its pyrolysis and torrefaction as possible environmental friendly and sustainable pathways of fuel upgrading. Simultaneous thermogravimetric and differential scanning calorimetry analysis have been carried out on common reeds. The evolved gases during the decomposition process have been analysed by a coupled infrared gas analyser and gas chromatograph/mass spectrometer. Different reed origins (China and Italy) and plant parts (stem and leaves) have been compared. The results have been used to calibrate a torrefaction kinetic model. The model has also been tested simulating a reed torrefaction run occurring in a bench‐scale apparatus, supplementing the chemical analysis with a thermal simulation of the reactor carried out through a finite elements approach. The results show that the proposed modelling approach allows the prediction of the reaction products with a satisfying degree of accuracy. Besides its phytodepuration potential, P. australis has proven to be an interesting natural biomass resource for thermochemical conversion processes and energy production both for its suitability and availability.

Laboratory/Demonstration-Scale Developments

Gasification processes come with great challenges regardless of the scale. Pilot-scale facilities encounter various problems, such as low conversion efficiencies or tar removal, which usually need significant trial and error, time, and finances to solve. Using data generated in pilot-scale facilities to model and simulate further developments in demonstration and commercial-scale plants is a well-known path that researchers and technology developers employ to reduce the risks of scale-up. In this chapter, few examples of pilot-scale gasification units are discussed, some of which are currently successful demonstration or commercial-scale plants. The chapter also describes some less successful examples and projects which are still in early development stages.

The case of Frictional Torrefaction and the effect of reflux condensation on the operation of the Rotary Compression Unit

This work introduces the process of Frictional Torrefaction and comes as a continuation to the previous work done on Frictional Pyrolysis, which is a novel method of pyrolysis that does not utilize heat but only friction and pressure. Both processes (i.e. Frictional Torrefaction and Frictional Pyrolysis) take place in a Rotary Compression Unit without and with a reflux condenser respectively. Rotating augers are used for the development of friction and the simultaneous increase of pressure. The following types of analysis were performed: TGA, BET, CHNS and HHV. Both products have similar heating values, around 21 MJ/kg. The elemental compositions are comparable but lower hydrogen content (3.5%) was measured for Frictional Torrefaction. BET analysis showed differences on the surface areas and porous sizes of the materials. Frictional Torrefaction has higher fixed carbon (31.23% vs 28.31%), higher surface area (58.16 m2/g vs 36.88 m2/g) and higher absorbance (35 cm3/g vs 26 cm3/g).