Thermal treatment of biomass

A biomass pyrolysis process is provided in which biomass feedstock is mixed with a heat carrier. The heat carrier at least partly comprises char. The ratio by weight of biomass to char is in the range 1:1 to 1:20. The process may be carried out by in a screw/auger pyrolysis reactor in which the solid feedstock components are conveyed along the reactor by a first screw. A second screw conveys at least a portion of the solid products of the biomass pyrolysis back to a heat transfer medium input port. Thus, the heat transfer medium includes char from the biomass pyrolysis.

Thermal Treatment

The invention provides methods and apparatus for thermal treatment, e.g. for pyrolysis of lignin. The lignin is provided to a reaction chamber as a paste, which can reduce or avoid process difficulties encountered when heating lignin.

High temperature gas cleaning for advanced syngas utilization:Paper # 95

Biofuels and chemicals from biomass mean the gasification of biogenic feedstocks and the synthesis via methanol, dimethylester (DME) or Fischer-Tropsch products. To prevent the sensitive synthesis catalysts from poisoning the syngas must be free of tar and particulates. The trace concentrations of S-, C1-, N-species, alkali and heavy metals must be of the order of a few ppb. Moreover maximum conversion efficiency will be achieved performing the gas cleaning above the synthesis conditions. The concept of an innovative dry HTHP syngas cleaning is presented. Based on the HT particle filtration and suitable sorption and catalysis processes for the relevant contaminants a total concept will be derived, which leads to a syngas quality required for synthesis catalysts in only 2 combined stages. The experimental setup for the HT gas cleaning behind the 60 kWtherm entrained flow gasifier REGA of the institute is described. Results from HT filter experiments in pilot scale are presented. The performance of 2 natural minerals for HC1 and H2S sorption is discussed with respect to the parameters temperature, surface and residence time. Results from lab scale investigations on low temperature tar catalysts' performance (commercial and proprietary development) are discussed finally.

Effect of thermal residual stresses on fatigue crack opening and propagation behavior in an Al/SiCp metal matrix composite

The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing. Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated. © 1995 The Minerals, Metals & Material Society.

Design, synthesis and thermal behaviour of a series of well-defined clickable and triggerable sulfonate polymers

In the printing industry, the exploitation of triggerable materials that can have their surface properties altered on application of a post-deposition external stimulus has been crucial for the production of robust layers and patterns. To this end, herein, a series of clickable poly(R-alkyl p-styrene sulfonate) homopolymers, with systematically varied thermally-labile protecting groups, has been synthesised via reversible addition-fragmentation chain transfer (RAFT) polymerisation. The polymer range has been designed to offer varied post-deposition thermal treatment to switch them from hydrophobic to hydrophilic. Suitable RAFT conditions have been identified to produce well-defined homopolymers (Đ, Mw/Mn < 1.11 in all cases) at high monomer conversions (>80% for all but one monomer) with controllable molar mass. Poly(p-styrene sulfonate) with an isobutyl protecting group has been shown to be the most readily thermolysed polymer that remains stable at room temperature, and was thus investigated further by incorporation into a diblock copolymer, P3HT-b-PiBSS, by click chemistry. The strategy for preparation of thermal modifiable block copolymers exploiting R-protected p-styrene sulfonates and azide-alkyne click chemistry presented herein allows the design of new, roll-to-roll processable materials for potential application in the printing industry, particularly organic electronics.

Studies of clay minerals and their decomposition products

Mõssbauer spectroscopy and X-ray diffraction of five coals revealed the presence of pyrite, illite, kaolinite and Quartz, together with other minor phases. Analysis of the coal ashes indicated the formation of hematite and an Fe (3+) paramagnetic phase, the latter resulting from .the dehydroxylation of the clay minerals during ashing at 700 to 750 C. By using a combination of several physicochemical methods, different successive stages of dehydroxylation, structural consolidation, and recrystallisation of illite, montmorillonite and hectorite upon thermal treatment to 1300 C were investigated. Dehydroxylation of the clay minerals occurred between 450 and 750 C, the X-ray crysdallinity of illite and montmorillonite remaining until 800 C. Hectorite gradually recrystallises to enstatite at temperatures above 700°C. At 900 C the crystalline structure of all three clay minerals had totally collapsed. Solid state reactions occurred above 900 C producing such phases as spinel, hematite, enstatite, cristobalite and mullite. Illite and montmorillonite started to melt between 1200 and 1300°C, producing a silicate glass that contained Fe(3+) and Fe(2+) ions. Ortho-pnstatite, clino-enstatite and proto-enstatite were identified in the thermal products of hectorite, their relative proportions varying with temperature. Protoenstatite was stabilised with respect to metastable clinoenstatite upon cooling from 12000 C by the presence of exchanged transition metal cations. Solid state Nuclear Magnetic Resonance spectroscopy of thermally treated transition metal exchanged hectorite indicated the levels at which paramagnetic cations could be loaded on to the clay before spectral resolution is significantly diminished.

Synthesis, thermal processing, and thin film morphology of poly(3-hexylthiophene)-poly(styrenesulfonate) block copolymers

A series of novel block copolymers, processable from single organic solvents and subsequently rendered amphiphilic by thermolysis, have been synthesized using Grignard metathesis (GRIM) and reversible addition-fragmentation chain transfer (RAFT) polymerizations and azide-alkyne click chemistry. This chemistry is simple and allows the fabrication of well-defined block copolymers with controllable block lengths. The block copolymers, designed for use as interfacial adhesive layers in organic photovoltaics to enhance contact between the photoactive and hole transport layers, comprise printable poly(3-hexylthiophene)-block-poly(neopentyl p-styrenesulfonate), P3HT-b-PNSS. Subsequently, they are converted to P3HT-b-poly(p-styrenesulfonate), P3HT-b-PSS, following deposition and thermal treatment at 150 °C. Grazing incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS) revealed that thin films of the amphiphilic block copolymers comprise lamellar nanodomains of P3HT crystallites that can be pushed further apart by increasing the PSS block lengths. The approach of using a thermally modifiable block allows deposition of this copolymer from a single organic solvent and subsequent conversion to an amphiphilic layer by nonchemical means, particularly attractive to large scale roll-to-roll industrial printing processes.

The geochemistry of radioactive waste disposal

The present study attempted to identify the significant parameters which affect radionuclide migration from a low level radioactive waste disposal site located in a clay deposit. From initial sorption studies on smectite minerals, increased Kd with decreasing initial cation concentration was observed, and three sorption mechanisms were identified. The observation of anion dependent sorption was related to the existence of a mechanism in which an anion-cation pair are bound to the clay surface through the anion. The influence of competing cations, typical of inorganic groundwater constituents, depended on: (1) Ni/Co:Mn+(Mn+ = competing cation) ratio, (2) nature of M^n+, (3) total solution ionic strength. The presence of organic material in groundwater is well documented, but its effect on cation sorption has not been established. An initial qualitative investigation involving addition of simple organic ligands to Ni(Co)-hectorite samples demonstrated the formation of metal complexes in the clay interlayers, although some modified behaviour was observed. Further quantitative examination involving likely groundwater organic constituents and more comprehensive physical investigation confirmed this behaviour and enabled separation of the organic compounds used into two classes, according to their effect on cation sorption; (i) acids, (ii) amine compounds. X-ray photoelectron spectroscopy, scanning electron microscopy and Mossbauer spectroscopy were used to investigate the nature of transition metal ions sorbed onto montmorillonite and hectorite. Evidence strongly favoured the sorption of the hexaaquo cation, although a series of sorption sites of slightly different chemical characteristics were responsible for broadened peak widths observed in XPS and Mossbauer investigations. The surface sensitivity of XPS enabled recognition of the two surface sorption sites proposed in earlier sorption studies. Although thermal treatment of Fe^3+/Fe^2+-hectorite samples left iron atoms bonded to the silicate sheet structure, Mossbauer evidence indicated the presence of both ferric and ferrous iron in all samples.

The plasma nutriding of tool and bearing steels

There is some evidence to suggest that nitriding of alloy steels, in particular high speed tool steels, under carefully controlled conditions might sharply increase rolling contact fatigue resistance. However, the subsurface shear stresses developed in aerospace bearing applications tend to occur at depths greater than the usual case depths currently produced by nitriding. Additionally, case development must be limited with certain materials due to case spalling and may not always be sufficient to achieve the current theoretical depths necessary to ensure that peak stresses occur within the case. It was the aim of' this work to establish suitable to overcome this problem by plasma nitriding. To assist this development a study has been made of prior hardening treatment, case development, residual stress and case cracking tendency. M2 in the underhardened, undertempered and fully hardened and tempered conditions all responded similarly to plasma nitriding - maximum surface hardening being achieved by plasma nitriding at 450°C. Case development varied linearly with increasing treatment temperature and also with the square root of the treatment time. Maximum surface hardness of M5O and Tl steels was achieved by plasma nitriding in 15% nitrogen/85% hydrogen and varied logarithmically with atmosphere nitrogen content. The case-cracking contact stress varied linearly with nitriding temperature for M2. Tl and M5O supported higher stresses after nitriding in low nitrogen plasma atmospheres. Unidirectional bending fatigue of M2 has been improved up to three times the strength of the fully hardened and tempered condition by plasma nitriding for 16hrs at 400°C. Fatigue strengths of Tl and M5O have been improved by up to 30% by plasma nitriding for 16hrs at 450°C in a 75% hydrogen/25% nitrogen atmosphere.

The relationship between fracture toughness and microstructure in titanium alloys

Linear Elastic Fracture Mechanics has been used to study the microstructural factors controlling the strength and toughness of two alpha-beta, titanium alloys. Fracture toughness was found to be independent of orientation for alloy Ti/6A1/4-V, but orientation dependent for IMI 700, bend and tension specimens giving similar toughness values. Increasing the solution temperature led to the usual inverse relationship between strength and toughness, with toughness becoming a minimum as the beta transus was approached. The production of a double heat treated microstructure led to a 100% increase in toughness in the high strength alloy and a 20% increase in alloy Ti/6A1/4V, with little decrease in strength. The double heat treated microstruoture was produced by cooling from the beta field into the alpha beta field, followed. by conventional solution treatment and ageing. Forging above the beta transus led to an increase in toughness over alpha beta forging in the high strength alloy, but had little effect on the toughness of Ti/6A1/4V. Light and electron microscopy showed that the increased toughness resulted from the alpha phase being changed from mainly continuous to a discontinuous platelet form in a transformed beta matrix. Void formation occurred at the alpha-beta interface and crack propagation was via the interface or across the platelet depending on which process required the least energy. Varying the solution treatment temperature produced a varying interplatelet spacing and platelet thickness. The finest interplatelet spacing was associated with the highest toughness, since a higher applied stress was required to give the necessary stress concentration to initiate void formation. The thickest alpha platelet size gave the highest toughness which could be interpreted in terms of Krafftt's "process zone size" and the critical crack tip displacement criterion by Hahn and Rosenfield from an analysis by Goodier and Field.

The breakdown of stainless steels in strong acids

A study was made of the corrosion behaviour in the ASTM standard Nitric acid and Oxalic acid tests, of two commercial AISI type 304L steels in the as received condition and after various heat treatments. Optical microscopy and SEM, TEM and STEM in conjunction with energy dispersive x-ray analysis, were used to correlate the corrosion behaviour of these steels with their microstructure. Some evidence of phosphorus segregation at grain boundaries was found. The corrosion behaviour at microstructural level was studied by examining on the TEM thin foils of steel that had been exposed to boiling nitric acid. Banding attack in the nitric acid and oxalic acid tests was studied using SEM and EPNA and found to be due to the micro-segregation of chromium and nickel. Using two experimental series of 304L, one a 17% Cr, 91 Ni, steel with phosphorus additions from 0.006% to 0.028%, the other a 20% Cr, 121 Ni steel with boron additions from 0.0011 to 0.00B51. The effect of these elements on corrosion in the nitric acid test was studied. The effect of different cooling rates and different solution treatment temperature on the behaviour of these steels was examined. TEM and STEM in conjunction with energy-dispersive x-ray analysis were again used to study the microstructure of the steels. Phosphorus was found to affect the corrosion behaviour but no effect was found with boron.

TiN-based coatings on fuel cladding tubes for advanced nuclear reactors

Titanium nitride (TiN) thin films are coated on HT-9 and MA957 fuel cladding tubes and bars to explore their mechanical strength, thermal stability, diffusion barrier properties, and thermal conductivity properties. The ultimate goal is to implement TiN as an effective diffusion barrier to prevent the inter-diffusion between the nuclear fuel and the cladding material, and thus lead to a longer lifetime of the cladding tubes. Mechanical tests including hardness and scratch tests for the samples before and after thermal cycle tests show that the films have a high hardness of 28GPa and excellent adhesion properties despite the thermal treatment. Thermal conductivity measurements demonstrate that the thin TiN films have very minimal impact on the overall thermal conductivity of the MA957 and HT-9 substrates, i.e., the thermal conductivity of the uncoated HT-9 and MA957 substrates was 26.25 and 28.44 W m-1 K-1, and that of the coated ones was 26.21 and 28.38W m-1 K-1, respectively. A preliminary Ce diffusion test on the couple of Ce/TiN/HT-9 suggests that TiN has excellent material compatibility and good diffusion barrier properties.

In situ synthesis and catalytic activity in CO oxidation of metal nanoparticles supported on porous nanocrystalline silicon

Reactive surface of mesoporous nanocrystalline silicon was used to synthesise noble metal nanoparticles via in situ reduction of the precursor salt solutions. The synthetic methodology for metal nanoparticle formation was systematically developed, and reaction conditions of metal salts reduction were optimised to prepare nanoparticles of controlled size distribution in the order 5–10 nm inside the mesoporous silicon template. CO oxidation was used as a test reaction for the synthesised Pt/porous silicon catalysts. Sharp reaction light-off was observed at about 120 °C on the optimised catalysts. The catalysts were shown to be stable in the extended steady-state runs and in the catalysts re-use experiments. Metal nanoparticles were shown to be stable to sintering at elevated temperatures up to 1000 °C. However, after thermal treatment on air, Pt nanoparticles were covered by a SiOx layer and were less active in CO oxidation.

Pharmaceutical process optimisation of bulk lyophilisates:implications of powder handling

Lyophilisation or freeze drying is the preferred dehydrating method for pharmaceuticals liable to thermal degradation. Most biologics are unstable in aqueous solution and may use freeze drying to prolong their shelf life. Lyophilisation is however expensive and has seen lots of work aimed at reducing cost. This thesis is motivated by the potential cost savings foreseen with the adoption of a cost efficient bulk drying approach for large and small molecules. Initial studies identified ideal formulations that adapted well to bulk drying and further powder handling requirements downstream in production. Low cost techniques were used to disrupt large dried cakes into powder while the effects of carrier agent concentration were investigated for powder flowability using standard pharmacopoeia methods. This revealed superiority of crystalline mannitol over amorphous sucrose matrices and established that the cohesive and very poor flow nature of freeze dried powders were potential barriers to success. Studies from powder characterisation showed increased powder densification was mainly responsible for significant improvements in flow behaviour and an initial bulking agent concentration of 10-15 %w/v was recommended. Further optimisation studies evaluated the effects of freezing rates and thermal treatment on powder flow behaviour. Slow cooling (0.2 °C/min) with a -25°C annealing hold (2hrs) provided adequate mechanical strength and densification at 0.5-1 M mannitol concentrations. Stable bulk powders require powder transfer into either final vials or intermediate storage closures. The targeted dosing of powder formulations using volumetric and gravimetric powder dispensing systems where evaluated using Immunoglobulin G (IgG), Lactate Dehydrogenase (LDH) and Beta Galactosidase models. Final protein content uniformity in dosed vials was assessed using activity and protein recovery assays to draw conclusions from deviations and pharmacopeia acceptance values. A correlation between very poor flowability (p<0.05), solute concentration, dosing time and accuracy was revealed. LDH and IgG lyophilised in 0.5 M and 1 M mannitol passed Pharmacopeia acceptance values criteria with 0.1-4 while formulations with micro collapse showed the best dose accuracy (0.32-0.4% deviation). Bulk mannitol content above 0.5 M provided no additional benefits to dosing accuracy or content uniformity of dosed units. This study identified considerations which included the type of protein, annealing, cake disruption process, physical form of the phases present, humidity control and recommended gravimetric transfer as optimal for dispensing powder. Dosing lyophilised powders from bulk was demonstrated as practical, time efficient, economical and met regulatory requirements in cases. Finally the use of a new non-destructive technique, X-ray microcomputer tomography (MCT), was explored for cake and particle characterisation. Studies demonstrated good correlation with traditional gas porosimetry (R2 = 0.93) and morphology studies using microscopy. Flow characterisation from sample sizes of less than 1 mL was demonstrated using three dimensional X-ray quantitative image analyses. A platinum-mannitol dispersion model used revealed a relationship between freezing rate, ice nucleation sites and variations in homogeneity within the top to bottom segments of a formulation.

Stabilization of self-assembled alumina mesophases

An efficient route to stabilize alumina mesophases derived from evaporation-induced self-assembly is reported after investigating various aspects in-depth: influence of the solvent (EtOH, s-BuOH, and t-BuOH) on the textural and structural properties of the mesophases based on aluminum tri-sec-butoxide (ATSB), synthesis reproducibility, role of nonvolatile acids, and the crystallization and thermal stability of the crystalline counterparts. Mesophase specific surface area and pore uniformity depend notably on the solvent; s-BuOH yields the highest surface area and pore uniformity. The optimal mesophase synthesis is reproducible with standard deviations in the textural parameters below 5%. The most pore-uniform mesophases from the three solvents were thermally activated at 1023 K to crystallize them into γ-alumina. The s-BuOH mesophase is remarkably thermally stable, retaining the mesoscopic wormhole order with 300 m2/g (0.45 cm3/g) and an increased acidic site density. These features are not obtained with EtOH or t-BuOH, where agglomerated γ-Al2O3 crystallites are formed with lower surface areas and broader pore size distributions. This was rationalized by the increase of the hydrolysis rate using EtOH and t-BuOH. t-BuOH dehydrates under the synthesis conditions or reacts with HCl, situations that increase the water concentration and rate of hydrolysis. It was found that EtOH exchanges rapidly, producing a highly reactive Al-ethoxide, thus enhancing the hydrolysis rate as well. Particle heterogeneity with random packing of fibrous and wormhole morphologies, attributed to the high hydrolysis rate, was observed for mesophases derived from both solvents. Such a low particle coordination favors coarsening with enlargement of the pore size distribution upon thermal treatment, explaining the lower thermal stability. Controlled hydrolysis and formation of low-polymerized Al species in s-BuOH are possibly responsible for the adequate assembly onto the surfactant. This was verified by the formation of a regular distribution of relatively size-uniform nanoparticles in the mesophase; high particle coordination prevents coarsening, favors densification, and maintains a relatively uniform pore size distribution upon thermal treatment. The acid removal in the evaporation is another key factor to promote network condensation in this route. © 2013 American Chemical Society.