Mathematical modelling of slow pyrolysis of segregated solid wastes in a packed-bed pyrolyser

Waste segregation is being explored as one of the potential effective ways for waste management, where wastes are separated for either recycling or energy recovery. In this paper, three segregated wastes, contaminated waste wood, cardboard and waste textile are pyrolysed in a slow-heating packed-bed reactor for the purpose of solid, liquid and gas recovery. The effect of final temperature was investigated and product yields and compositions were measured. Mathematical modelling was employed to simulate the heat, mass transfer and kinetic processes inside the reactor. Both a parallel reaction model and a function group model were used to predict the product yields as well as their compositions. Char yield of 21–34%, tar 34–46% and gas 23–43% were obtained. It is found that packed-bed pyrolysis produces 30–100% more char compared to standard TGA tests and the local heating rate across the packed-bed reactor differs remarkably from the programmed wall-heating rate and varies greatly in both time and space. Mathematical modelling suggests that wood has higher tar cracking ability than cardboard and textile wastes during pyrolysis, and the effects of mineral contents in the fuel need to be explored. CO₂, CO, tar and water are the main released species during the major stage of the pyrolysis processes which occurs between 250 and 450 °C, whereas noticeable quantity of hydrogen and light hydrocarbons is observed only at higher temperature levels and at the final stage.     

Structural Features of C–S–H(I) and Its Carbonation in Air—A Raman Spectroscopic Study. Part II: Carbonated Phases

The effects of carbonation of mechanochemically prepared C–S–H samples under ambient conditions for upto 6 months have been investigated by Raman spectroscopy and X-ray diffraction. The type and extent of carbonation are strongly dependent on the initial CaO/SiO₂ (C/S) ratio of the samples. Amorphous calcium carbonate hydrate is formed within minutes upon exposure to air. It crystallizes, over time, to give primarily vaterite at C/S≥0.67 and aragonite at C/S≤0.50. Calcite was not observed as a primary carbonation product within the time frame investigated. Decalcification upon storage also initiates silicate polymerization. The dimeric silicate units seen in the calcium-rich phases polymerize rapidly to yield Q² silicate moieties. After 6 months, broad bands are seen in most spectra, ascribed to poorly ordered silica. C–S–H phases with C/S ratios of 0.75 and 0.67 are the most resistant to carbonation, and even after 6 months of storage, Q² silicate units still dominate their structures. The ability of Raman spectroscopy to probe the short-range order of poorly crystalline materials is ideal for investigations of C–S–H structure. Additionally, the technique's sensitivity toward the various calcium carbonate polymorphs illuminates the sequence of carbonation and decalcification processes during aging of C–S–H. Of particular importance is the identification of amorphous calcium carbonate as the first carbonation product. Additionally, the formation of aragonite as a carbonation product is related to the presence of SiO₂ gel in the aged samples.     

Mineralizing Effect of Li2B4O7 and Na2B4O7 on Magnesium Aluminate Spinel Formation

Lithium borate (Li₂B₄O₇) and sodium borate (Na₂B₄O₇) mineralize spinel formation from stoichiometric MgO and Al₂O₃ between 1000° and 1100°C. Mineralization with both compounds is shown to be mediated by B-containing liquids which form glass on cooling. However, the liquid compositions depend on the type of mineralizer and temperature, suggesting that templated grain growth or dissolution–precipitation mechanisms are operating, one dominating over the other under certain conditions. Na₂B₄O₇-mineralized compositions show predominantly templated grain growth at 1000°C, which changes to dissolution–precipitation at 1100°C, whereas Li₂B₄O₇-mineralized compositions show dissolution–precipitation from 1000°C. Li₂B₄O₇ is a stronger mineralizer as spinel formation is complete with 3 wt% Li₂B₄O₇ at 1000°C and with ≥1.5 wt% addition at 1100°C, whereas Na₂B₄O₇-mineralized compositions are found to retain some unreacted corundum even at 1100°C.     

Citrulline malate supplementation does not improve German Volume Training performance or reduce muscle soreness in moderately trained males and females

Background

Use of supplements to aid performance is common practice amongst recreationally active individuals, including those without a sufficient evidence base. This investigation sought to assess whether acute supplementation with 8 g of citrulline malate (CM) (1.11: 1 ratio) would improve anaerobic performance.

Methods

A randomised double blind placebo control trial was employed, using a counterbalanced design. We recruited recreationally active men and women to take part in an isokinetic chair protocol, based on German Volume Training (GVT) whereby participants attempted to perform 10 sets of 10 repetitions against a force representing 70% of their peak concentric force.

Results

The number of repetitions achieved over the course of the GVT was 94.0?±?7.9 and 90.9?±?13.9 for placebo and CM respectively. There was no significant difference between the placebo and CM treatment for number of repetitions (P?=?0.33), isometric (P?=?0.60), concentric (P?=?0.38), or eccentric (P?=?0.65) peak force following the GVT. Total muscle soreness was significantly higher in the CM compared to the placebo treatment following the GVT protocol over 72 h (P?=?0.01); although this was not accompanied by a greater workload/number of repetitions in the CM group.

Conclusions

We conclude that an acute dose of CM does not significantly affect anaerobic performance using an isokinetic chair in recreational active participants. Practical implications include precaution in recommending CM supplementation. Coaches and athletes should be aware of the disparity between the chemical analyses of the products reviewed in the present investigation versus the manufacturers’ claims.

     

Minimum sensitivity based robust beamforming with eigenspace decomposition

An enhanced eigenspace-based beamformer (ESB) derived using the minimum sensitivity criterion is proposed with significantly improved robustness against steering vector errors. The sensitivity function is defined as the squared norm of the appropriately scaled weight vector and since the sensitivity function of an array to perturbations becomes very large in the presence of steering vector errors, it can be used to find the best projection for the ESB, irrespective of the distribution of additive noises. As demonstrated by simulation results, the proposed method has a better performance than the classic ESBs and the previously proposed uncertainty set based approach.     

Housing performance evaluation: challenges for international knowledge exchange

ABSTRACT

Developing effective building performance evaluation and feedback processes is a vital part of global efforts to reduce building energy use and gain insight into the actual performance of buildings and technologies. Although attempts have been made to introduce internationally agreed models for these processes, it is clear that various countries are producing different approaches according to their cultural, institutional and policy differences. Knowledge exchange is potentially a key means of developing a shared understanding of values, meanings and practices in relation to building performance evaluation. This paper identifies cultural and institutional barriers in the European Union for international building performance communities of practice utilizing knowledge exchange, from an experiential ‘real-world’ perspective. The preparation of a 30-month research project to help develop building performance evaluation in Poland and an associated bilateral symposium is closely evaluated through an action research case study in terms of the stakeholders, the national contexts in which they operated and the key challenges they faced. Recommendations are then made in terms of the support needed to develop more responsive research programmes in relation to developing international knowledge exchange, and the capacity-building elements required for these international communities of practice.     

Particle refinement of ZrB2 by the combination of borothermal reduction and solid solution

Flexible synthesis of ultra‐fine ZrB₂ powders was achieved by borothermal reduction in a mixture of ZrO₂, boron, and TiO₂. Without TiO₂ additive, coarse ZrB₂ powders with particle size of 0.81 μm were obtained, presumably due to good wettability and solubility of ZrB₂ in the byproduct B₂O₃. It was found that the particle growth of ZrB₂ was effectively inhibited by the solid solution of TiB₂ (≥1 mol%). The refinement mechanism was that the solid solution of in situ formed TiB₂ presumably lowered the wettability and solubility of ZrB₂ in the B₂O₃ liquid and significantly inhibited the coarsening of ZrB₂. The average particle size of resulting powders decreased to 0.37 μm with the addition of 10 mol% TiO₂.