Title: Screening of ten different plants in the process of supercritical water gasification

Authors: Julian Dutzi, I. Katharina Stoll, Nikolaos Boukis, Jörg Sauer

Publication Year: 2024

Proposed by: Rainer Janssen

Project Areas: Supercritical water, biomass, hydrogen, homogeneous catalyst

Abstract

It is important to know the limitations of the supercritical water gasification (SCWG) in terms of behavior of different biomasses, especially when determining whether SCWG is a suitable conversion process for a certain biomass. Ten different biomasses (eight different plant species, of which two were grown in two different sites) were processed to evaluate this aspect. Moist and dry, woody, and grassy biomasses were gasified in the same experimental setup under similar conditions. Only small differences could be seen in the gasification experiments. The carbon gasification efficiency was 60.3 ± 5.1 %, the gas compositions were very similar. Solid deposits formed in all experiments in the same temperature zone of the reactor containing coke, salt building elements and heavy metals, sometimes leading to plugging. Nevertheless, an experimental duration of 6 h could be achieved for the dry biomasses. The experiment with the moist biomass Reed Canary Grass was ended early due to plugging of the feed tubing which is due to the different size reduction procedure for moist biomasses resulting in bigger biomass particles. This emphasizes the importance of sufficient size reduction prior to the experiment. Potassium addition as a homogeneous catalyst, in form of potassium hydroxide, has proven to be beneficial regarding gasification efficiency, but poses a threat regarding plugging due to salt deposits in the system.

Title: Energetic Assessment of SCWG Experiments with Reed Canary Grass and Ethanol Solution on Laboratory and Pilot Scale

Authors: Julian Dutzi, Nikolaos Boukis, Jörg Sauer

Publication Year: 2023

Proposed by: Nikolaos Boukis

Project Areas: Supercritical water, Biomass, Gasification

Abstract

The energetic assessment of biomass conversion processes is important for evaluating their application potential. Process energy efficiency is often evaluated based on simulation results for processes under idealized conditions. The present work uses data from a laboratory plant to perform an evaluation of the supercritical water gasification (SCWG). For this purpose, experiments were conducted with two types of feedstock, Reed Canary Grass and ethanol. Under the present lab-plant configuration, a cold gas efficiency of up to 79% could be reached, which is comparable to the gasification of biomass in fluidized-bed gasifiers or entrained-flow gasifiers. Based on the obtained data on the produced substances and their distribution, a scale up to pilot plant size was conducted. A model was derived from the available data to energetically assess different SCWG plant sizes based on real laboratory results. This model can be transferred to other feedstocks and other process designs to approximate the optimal size for the used biomass feedstock. The importance of heat recuperation in this process is described in detail based on pilot-scale data.

Title: Process Effluent Recycling in the Supercritical Water Gasification of Dry Biomass

Authors: Julian Dutzi, Nikolaos Boukis and Jörg Sauer

Publication Year: 2023

Proposed by: Nikolaos Boukis

Project Areas: Biomass Resources, Process design, Technologies

Abstract

The influence of process water recycling during the Supercritical Water Gasification (SCWG) of dry biomasses was investigated. Dry biomass has to be diluted with water to a dry matter content of approximately 10 wt.% to gasify it in the process of supercritical water gasification. The treatment of wastewater in the SCWG process is cost intensive due to organic contaminants; therefore, the recycling of the process effluent is attractive. Salt separation is needed to avoid accumulation of salts in the effluents, since salts enhance corrosion rates and might cause blocking of the flow when the effluent is recycled. The grass Reed Canary Grass and grapevines were gasified. The recycling of the process effluent did not influence the composition of the product gas. In both cases the carbon efficiency decreased by 4% when wastewater was used to dilute the biomass. An increase in organic carbon and potassium in the reactor effluent was observed after gasification of the biomass with recycled process effluent. The addition of potassium hydroxide to the feed as a homogenous catalyst needs to be closely monitored and adjusted according to the potassium content of the reactor effluent. Insufficient salt separation proved to be an issue regarding formation of solid deposits in the reaction system.

Title: Optimizing the Design of a Biomass-to-Biofuel Supply Chain Network Using a Decentralized Processing Approach

Authors: Fragkoulis Psathas, Paraskevas N. Georgiou, Athanasios Rentizelas

Publication Year: 2022

Proposed by: Athanasios Rentizelas

Project Areas: Biomass Resources, Biomass Availability

Abstract

When designing biomass-to-biofuel supply chains, the biomass uncertainty, seasonality and geographical dispersion that affect economic viability need to be considered. This work presents a novel methodology that can optimize the design of biofuel supply chains by adopting a decentralized network structure consisting of a mix of fixed and mobile processing facilities. The model considers a variable biomass yield profile and the mobile fast pyrolysis technology. The mixed-integer linear programming model developed identifies the optimal biofuel production and biomass harvesting schedule schemes under the objective of profit maximization. It was applied in the case study of marginal lands in Scotland, which are assumed to be planted with Miscanthus. The trade-offs observed between economies of scale against the transportation costs, the effect of the relocation costs and the contribution of storage capacity were investigated. The results showed that, in most cases, harvesting is most concentrated during the month of the highest biomass yield, provided that storage facilities are available. Storage capacity plays an important role to widen the operational time window of processing facilities since scenarios with restricted or costly storage resulted in facilities of higher capacity operating within a narrower time window, leading to higher investment costs. Relocation costs proved to have a minor share in the total transportation costs.

Title: Soil Compaction in Harvesting Operations of Phalaris Arundincea L.

Authors: Leonardo Bianchini, Riccardo Alemanno, Valerio Di Stefano, Massimo Cecchini and Andrea Colantoni

Publication Year: 2022

Proposed by: Andrea Colantoni (Tuscia University)

Project Areas: Biomass Resources, Biomass Availability, Phytoremediation

Abstract

Tillage and harvesting operations of perennial forage crops have problems with soil compaction. The effects of this phenomenon are soil deterioration with reduced crop performance and yield. This study aims to assess soil disturbance by measuring the level of compaction caused by the harvesting operations of Phalaris arundinacea L. P. arundinacea is a species that lends itself to biomass production and phytoremediation of contaminated soils; it adapts to difficult soil conditions, outperforming other species in terms of ease of planting, cost, maturity time, yield, and contamination levels. The crop was sown in three plots of the experimental teaching farm of the University of Tuscia, Viterbo, Italy. Following a detailed analysis of the chemical–physical characteristics of the soil, minimum tillage was chosen in order to concentrate on harvesting operations, which were carried out with a disc mower coupled to a tractor. This was followed by penetration resistance and soil moisture measurements to verify the incidence of the operations and the effect of the type of crop on compaction. On the study site, measurements were taken at points that the wheels of the tractor had gone over and at points that they had not. The soil analysis results indicate different chemical–physical characteristics between the two areas, the texture being frankly sandy to clayey. Penetration resistance measurements indicated differences for the first 20 cm between the part that was covered by the tractor’s tyres and the part that was left touched but also between the three plots. Moisture influenced penetration resistance. This study provides an evaluation of the first data obtained from a project that will last four years and which will explore the dynamics between soil, cultivation, and harvesting operations, giving a fundamental basis for further investigation of further harvesting operations and soil characteristics, which are crucial for planning and managing crops and reducing impacts on the soil in order to preserve it.