Carbon Resources Conversion最新文献

Energy efficiency and economic viability are the often-quoted issues in aquaponic farming. This work aims to (i) identify process technologies and technical measures which would enhance the profitability of aquaponics business while conserving energy and other resources, and (ii) to validate the determined optimal measures on the testing aquaponics farm. The process network synthesis technique was used to search for an optimal process pathway while the image processing technique was applied to automatically monitor the growth rate of produce since it is the main revenue stream in aquaponics. With the aid of P-graph method, the optimal feasible structure has 9 times higher annual net income than that of the existing process. This optimal solution includes the integration of electrical heat pump, biogas system, and utilizes black solider fly (BSF) facility to produce fish feed. Additional light energy savings were achieved by practical installation of reflective foils which improved 16.88% of Photosynthetic photon flux density (PPFD) on growth beds. These measures can help the aquaponics farms to become more competitive and to decrease their ecological footprint.

2,5-Bis(hydroxymethyl)furan (BHMF) is a high-value, bio-based, rigid diol that resembles aromatic monomers for the production of different polyesters. In this work, a carbon nanotubes (CNTs)-supported nickel catalyst (Ni/CNTs) was prepared and used for the selective hydrogenation of 5-hydroxymethylfurfural (HMF) to BHMF at low hydrogen pressure. The prepared catalyst was analyzed by nitrogen adsorption–desorption isotherms, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). According to kinetic studies, the rate constant for BHMF formation is significantly larger than that for the formation of the byproduct, 5-methyl furfural (MF). At optimal reaction conditions, conversion and selectivity rates of HMF and BHMF were 99.8 % and 95.0 %, respectively. The mechanistic study indicated the coexistence of Ni⁰ and Ni²⁺ species on the catalyst surface affects the catalytic performance. A possible mechanism was proposed to describe the synergetic effects of Ni⁰ and Ni²⁺. Furthermore, the catalyst can be easily separated from the reaction mixture for recycling.

In order to substitute fossil resources in activated carbon (AC) production, recent efforts have focused on the utilization of renewable raw materials. Regions with important wood industries offer two potentially underestimated resource types: forestry residue biomass (FRB) and waste wood (WW). Although these materials are widely available (approx. 130 mio. m³a^-1 FRB, approx. 50 mio. ta^-1 WW in the EU), they are mostly valorised through energy production, as they are high in ashes and may be contaminated with organics and heavy metals. In this study, both FRB and WW were treated via one-step pyrolysis for AC production. ZnCl₂ was applied as activating agent at pyrolysis temperatures varying from 400 to 600 °C and residence times between 1 and 3 h. Overall, 76 samples were prepared and characterized thoroughly via elemental analysis, N₂/CO₂ ad/-desorption, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and infrared spectroscopy (FTIR). The produced carbons showed specific surface areas of up to 1430 m²g⁻¹ and a pore size distribution with a micropore share of up to 80 %. The presence of oxygen-containing functional groups was confirmed via FTIR. Potential feedstock contamination can be mitigated, as minerals and heavy metals could be leached out (up to –99.15 %) by an additional wash step and organic contamination undergoes thermal cracking during pyrolysis. The presented study could be a next step in upcycling considerable waste streams from the wood sector through localised and non-fossil-based AC production.

Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.

The catalyst combination resulted in a reduction of 50% in the overall tar yield with respect to the reference values. Furthermore, the integration of an oxidative Hot Gas Filtration unit downstream the gasification reactor led to a further reduction in overall tar yield and relatively clean gas was obtained (approx. 1 g/Nm³, benzene-free). The tar dew point of the resulting producer gas was estimated to 80 °C, only 40 °C above the threshold value recommended for its valorisation in standard internal combustion engines. Moreover, catalyst elutriation and char hold-up took place to a large extent inside the reactor. The analysis of catalyst samples at different Time-On-Stream (TOS) revealed: (i) a considerable loss of iron oxides during the first hour of test because of the interparticle mechanical attrition (mostly surface abrasion) and partial reduction of hematite to magnetite and wustite but, stable composition at higher TOS, (ii) the loss of the iron oxide coverage of Fe/olivine particles and the formation of agglomerates with increasing TOS and, (iii) the amount of carbon deposited in the surface of the Fe/olivine particles increased with TOS, but in any case, these carbon deposits can be completely oxidized above 650 °C.

Currently, CO₂ conversion and utilization have become a key to mitigate the global warming. In this study, a novel separate-type autothermal dry reforming of methane (S-ATDRM) system is proposed and simulated, in which the methane dry reforming combined with methane partial oxidation is performed in a circulating fluidized bed with exergy recuperation to eliminate the negative effect of the products of CH₄ partial oxidation on the DRM reaction and further improve the CO₂ conversion efficiency. The results demonstrate that this S-ATDRM system can achieve an exergy efficiency of 84.7 %, and about 1055.7 kW of exergy can be recuperated from the process for crude syngas cooling and reapplied for pre-heating of feedstocks of CO₂, O₂ and CH₄. It is found that the largest exergy destruction in this system occurs in the partial oxidation reactor, which occupies ca. 45.6 % of the whole exergy loss. Comparing with the conventional ATDRM system, although the exergy of S-ATDRM system is decreased by approximately 0.3 %, the CO₂ conversion is substantially increased by about 11.3 %.