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For high performance of hydrocarbonintumescent coatings, interactions between the acid source ammoniumpolyphosphate (APP) and inorganic fillers can be critical. In the present work,low-borate concentration (i.e., 1 wt.% zinc borate) intumescent coatings with different concentrationratios of CaCO3 to APP were studied in an attempt to map thereaction mechanisms. The analysis of the coating performance was conductedusing thermal insulation assessment according to the UL1709 fire curve(disregarding substrate load, geometrical diversity, and other full-scaleimplications of the complete standard), rheological measurements,thermogravimetric analyses (TGA), Fourier transform infrared spectrometer(ATR-FTIR), and X-ray diffraction (XRD). Results show that a coating with a CaCO3/APPmass ratio of 0.3 gives the best performance (i.e., the longest critical time ofsteel substrates to reach both 400 and 550 oC in the thermalinsulation assessment). The dependency on the CaCO3/APP ratio of thedynamic viscosity minimum points to significant interactions between CaCO3and APP during the softening state (i.e., the intumescence process) of thecoating. Due to an enhanced anti-oxidation property, the degradation zone ofthe intumescent char and the residual weight of the coating after exposure wereboth improved when increasing the CaCO3/APP ratio. The compositionaldevelopment of the intumescent char showed that CaCO3 and APP reactto form a new polymeric phase, calcium catena-polyphosphate (CaP2O6).This polyphosphate may contribute to the formation of a compact phase in theintumescent char and benefit the thermal insulation performance of low-borateconcentration hydrocarbon intumescent coatings.

The mixing and segregation behaviour of binary solid mixtures has been extensively studied through various experiments, while accurate CFD simulations are difficult to achieve due to process complexity and a lack of reliable constitutive relations. In this study, CFD simulations of a dense fluidized bed with glass and polystyrene particles were performed in order to identify a universal set of simulation parameters and models for simulating binary mixtures with different mixed and segregation behaviour. Through a comparison to experimental data, it was found that the EMMS drag model coupled with the Ma‐Ahmadi solid pressure and radial distribution models predicted more a reasonable axial distribution of solid phases than the Syamlal O´Brien drag model coupled with the Lun et al. solid pressure and radial distribution models. The increase in the solid‐solid drag further improved the simulation results.

Silicones are typically cured at room temperature by means of metal catalyst such as tin or platinum. When networks are formed the catalyst become unrecoverable, which is of economic as well as environmental concern. Very few methods for producing metal catalyst-free room-temperature vulcanised (RTV) silicones exist and require conditions unavailable in industrial settings. Through the study of organic polysilazane (PSz) reactivity with simple alcohols by NMR, we discovered an unexpected fragmentation preference for breaking the Si-N bond rather than the Si-H; thereby, casting a new light on the fragmentation mechanism of polysilazanes. Utilising the polysilazane fragmentation as a silyl ether coupling agent for multifunctional carbinol silicones, we present a method of producing catalyst free RTV silicone networks at ambient conditions. These silicone networks were proven chemically similar to a standard condensation cured silicone and stoichiometric variations of PSz content demonstrated adjustable network properties.

Silicone elastomers are used in a wide range of applications, including artificial muscles, biomedical devices, and soft robotics, for which chemical, thermal, and mechanical stability are important requirements that these elastomers must fulfill. However, to ensure that silicone elastomers' properties and performance remain constant under long‐term deployment, it is necessary to examine and account for the Mullins effect, which has the potential to significantly alter certain elastomer properties of interest. In this article, the mechanical properties of soft and hard commercial silicone elastomers and two blends of commercial silicone elastomers are investigated—specifically their softening behavior due to the Mullins effect. Ultimate stresses, ultimate strains, and Young's moduli are obtained from uniaxial tensile tests. Results show that the point of softening greatly depends on both the elastomer type and its strain history. Furthermore, a significant permanent set is observed in the softest commercial formulations.

The direct sulfation of limestone was studied in a quartz bench scale fixed-bed reactor with the technique of data deconvolution. The obtained results show that the direct sulfation of limestone has a two-period kinetic behavior: a short initial sulfation period with high but fast decreasing reaction rate and a subsequent period with product crystal growth with low-conversion rate. The transition from the first period to the second period is sharp and indicates clearly the start point of the period with product crystal growth. The transition point was determined by the concentrations of gases such as SO2, O2, and CO2 and the temperature. The sulfation process in the initial stage of the period with product crystal growth can be described by the combination of the sulfation reaction at the gas–solid interface, diffusion of the product ions toward the product crystal grains, diffusion of carbonate ions toward the gas–solid interface to react, and the gradual shielding of calcite surface area by the product crystal grains. A simple and semi-empirical mathematical model derived on basis of this theory gives a satisfactory description of the experimental results up to a calcite conversion of about 0.5%. © 2010 American Institute of Chemical Engineers AIChE J, 2011

The initial kinetics of direct sulfation of Faxe Bryozo, a porous bryozoan limestone was studied in the temperature interval from 873 to 973 K in a pilot entrained flow reactor with very short reaction times (between 0.1 and 0.6 s). The initial conversion rate of the limestone—for conversions less than 0.3%—was observed to be significantly promoted by higher SO2 concentrations and lower CO2 concentrations, whereas O2 showed negligible influence. A mathematical model for the sulfation of limestone involving chemical reaction at calcite grain surfaces and solid-state diffusion of carbonate ions in calcite grains is established. The validity of the model is limited to the initial sulfation period, in which nucleation of the solid product calcium sulphate is not started. This theoretical reaction-diffusion model gives a good simulation of the initial kinetics of the direct sulfation of Faxe Bryozo. The intrinsic rate of the direct sulfation of the limestone is estimated to have an activation energy of about 25 kJ/mol and reaction orders of about 0.9 and −0.75 for SO2 and CO2, respectively. The diffusivity of carbonate ions in the surface layer of the calcite grain is estimated to be about three orders of magnitude higher than the diffusivity of carbonate ions in the inner lattice of calcite grain and have an activation energy of about 202 kJ/mol. © 2008 American Institute of Chemical Engineers AIChE J, 2008

The oxidation of methanol in a flow reactor has been studied experimentally under diluted, fuel-lean conditions at 650–1350 K, over a wide range of O2 concentrations (1%–16%), and with and without the presence of nitric oxide. The reaction is initiated above 900 K, with the oxidation rate decreasing slightly with the increasing O2 concentration. Addition of NO results in a mutually promoted oxidation of CH3OH and NO in the 750–1100 K range. The experimental results are interpreted in terms of a revised chemical kinetic model. Owing to the high sensitivity of the mutual sensitization of CH3OH and NO oxidation to the partitioning of CH3O and CH2OH, the CH3OH + OH branching fraction could be estimated as α = 0.10 ± 0.05 at 990 K. Combined with low-temperature measurements, this value implies a branching fraction that is largely independent of temperature. It is in good agreement with recent theoretical estimates, but considerably lower than values employed in previous modeling studies. Modeling predictions with the present chemical kinetic model is in quantitative agreement with experimental results below 1100 K, but at higher temperatures and high O2 concentration the model underpredicts the oxidation rate. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 423–441, 2008

The direct sulfation of limestone was studied in a laboratory fixed-bed reactor. It is found that the direct sulfation of limestone involves nucleation and crystal grain growth of the solid product (anhydrite). At 823 K and at low-conversions (less than about 0.5 %), the influences of SO2, O2 and CO2 on the direct sulfation of limestone corresponds to apparent reaction orders of about 0.2, 0.2 and −0.5, respectively. Water is observed to promote the sulfation reaction and increase the apparent reaction orders of SO2 and O2. The influence of O2 at high O2 concentrations (> about 15 %) becomes negligible. In the temperature interval from 723 K to 973 K, an apparent activation energy of about 104 kJ/mol is observed for the direct sulfation of limestone. At low temperatures and low conversions, the sulfation process is most likely under mixed control by chemical reaction and solid-state diffusion. The nucleation and crystal grain growth of the solid product, and this mixed control mechanism provide satisfactory explanations of the various phenomena related to the direct sulfation of limestone, such as porosity in the product layer, the variation of the apparent reaction orders of SO2, O2 and CO2 with reaction conditions and the influence of water. © 2007 American Institute of Chemical Engineers AIChE J, 53: 948–960, 2007

Mathematical modeling has been used to characterize and validate the working mechanisms of tin-free, chemically-active antifouling (AF) paints. The model-based analysis of performance data from lab-scale rotary experiments has shown significant differences between antifouling technologies as regards the biocide leaching and the surface polishing processes. Hence, the modeling framework developed in this work is built so as to describe any generic, chemically-active AF paint through model parameters, the values of which can be obtained or adjusted from relatively fast measurements. The detailed quantitative information on reacting AF paint systems obtained can be used for accelerated product optimization purposes, thus facilitating the transition to cleaner antifouling technologies using, for example, fast-degrading natural or synthetic bioactive components. © 2006 American Institute of Chemical Engineers AIChE J, 2006

The oxidation of benzene under flow-reactor conditions has been studied experimentally and in terms of a detailed chemical kinetic model. The experiments were performed under plug-flow conditions, at excess air ratios ranging from close to stoichiometric to very lean. The temperature range was 900–1450 K and the residence time of the order of 150 ms. The radical pool was perturbed by means of varying the concentration of water vapor and by adding NO. Furthermore, a few experiments were conducted on pyrolysis and oxidation of phenol. Benzene oxidation is initiated at ∼1000 K; the temperature for complete oxidation depends on stoichiometry, ranging from 1100 K (very lean conditions) to 1300 K (close to stoichiometric). The water vapor level and the presence of NO have only a minor impact on the temperature regime for oxidation. The proposed chemical kinetic model was validated by comparison with the present experimental data as well as flow reactor and mixed reactor data from literature. The model provides a reasonably good description of the overall oxidation behavior of benzene over the range of conditions investigated. However, before details of the oxidation behavior can be predicted satisfactorily, a number of kinetic issues need to be resolved. These include product channels and rates for the reactions of phenyl and cyclopentadienyl with molecular oxygen as well as reaction chemistry for the oxygenated cyclic compounds formed as intermediates in the oxidation process. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 498–522, 2000

In coal-fired combustion systems solid calcium species may be present as ash components or limestone added to the combustion chamber. In this study heterogeneous reactions involving HCN over seven different limestones were investigated in a laboratory fixed-bed quartz reactor at 873-1173 K. Calcined limestone is an effective catalyst for oxidation of HCN. Under conditions with complete conversion of HCN at O 2 concentrations above about 5000 ppmv the selectivity for formation of NO and N 2 O is 50-70% and below 5%, respectively. Nitric oxide can be reduced by HCN to N 2 in the absence of O 2 and to N 2 and N 2 O in the presence of O 2 . At low O 2 concentrations or low temperatures, HCN may react with CaO, forming calcium cyanamide, CaCN 2 . The selectivities for formation of NO and N 2 O from oxidation of CaCN 2 is 20-25% for both species. The catalytic activity of limestone for oxidation of HCN decreases with increasing degree of sulfation. Simultaneously the selectivity for formation of NO decreases while that for N 2 O increases. The catalytic activity of sulfated limestone increases with decreasing SO 2 concentration, indicating a competition between SO 2 and HCN for sites on the surface. The results indicate that heterogeneous oxidation of HCN is important in calciners and fluidized-bed combustors with limestone addition or when burning coals with an ash with a high catalytic activity.

An experimental and theoretical study on the effect of SO2 on moist CO oxidation with and without NO present has been carried out. The experiments were performed in an isothermal quartz flow reactor at atmospheric pressure in the temperature range 800–1300 K. Inlet concentrations of SO2 ranged from 0 to 1800 ppmv, while the NO ranged between 0, 100, or 1500 ppm. SO2 inhibits CO oxidation under the conditions investigated, shifting the fast oxidation regime 20–40 K towards higher temperatures at 1500 ppm SO2. The inhibition is most pronounced at high O atom levels. The experimental data supported by model analysis suggest that SO2 primarily reacts with O atoms forming SO3, which is subsequently consumed mainly by reaction with O and HO2. Addition of NO significantly diminishes the effect of SO2. Since NO is usually present in combustion flue gases, the impact of SO2 on CO burnout in most practical systems is projected to be small. The H/S/O thermochemistry and reaction subset has been revised based on recent experimental and theoretical results, and a chemical kinetic model has been established. The model provides a reasonable overall description of the effect of SO2 and NO on moist CO oxidation, while the SO3/SO2 ratio is well predicted over the range of conditions investigated. In order to enhance model performance further, rate constants for a number of SO2 and SO3 reactions need to be determined with higher accuracy. © 1996 John Wiley & Sons, Inc.

The NH3/NO2 system has been investigated experimentally in an isothermal flow reactor in the temperature range 850–1350 K. The experimental data were interpreted in terms of a detailed reaction mechanism. The flow reactor results, supported by a theoretical analysis of the NH2NO2 complex, suggest that the NH2 + NO2 reaction has two major product channels, both proceeding without activation barriers: Our findings indicate that the N2O + H2O channel is dominant at low temperatures while H2NO + NO dominates at high temperatures. The rate constant for reaction (R21) is estimated to be 3.5 · 1012 cm3/mol-s in the temperature range studied with an uncertainty of a factor of 3. © 1995 John Wiley & Sons, Inc.

We have investigated the impact of surface reactions such as NH3 decomposition and radical adsorption on quartz flow reactor data for Thermal DeNOx using a model that accounts for surface chemistry as well as molecular transport. Our calculations support experimental observations that surface effects are not important for experiments carried out in low surface to volume quartz reactors. The reaction mechanism for Thermal DeNOx has been revised in order to reflect recent experimental results. Among the important changes are a smaller chain branching ratio for the NH2 + NO reaction and a shorter NNH lifetime than previously used in modeling. The revised mechanism has been tested against a range of experimental flow reactor data for Thermal DeNOx with reasonable results. The formation of N2O in Thermal DeNOx has been modelled and calculations show good agreement with experimental data. The important reactions in formation and destruction of N2O have been identified. Our calculations indicate that N2O is formed primarily from the reaction between NH and NO, even though the NH2 + NO2 reaction possibly contributes at lower temperatures. At higher temperatures N2O concentrations are limited by thermal dissociation of N2O and by reaction with radicals, primarily OH. © 1994 John Wiley & Sons, Inc.

The feasibility of combining selective reduction of nitric oxide by ammonia, or nitric oxide oxidation by methanol, with partial flue gas condensation has been studied in the laboratory. It was demonstrated that both combinations may result in high removal efficiencies for nitric oxide and sulfur dioxide. High-temperature reactors (600-900[degrees]C) and low-temperature (20-40[degrees]C) tubular condensers were applied in series, and each one was tested individually. The flow of simulated flue gas ranged from 1 to 5 Nl/min. In the condenser simultaneous absorption of ammonia, sulfur dioxide, oxygen, and nitrogen dioxide took place. At certain conditions large quantities of aerosols were formed, particularly when NO[sub 2] was present. 12 refs., 5 figs.

N2O decomposition and formation during the oxidation of NH3 and HCN were studied in a quartz flow reactor in the presence of CO, NO and other gases. The emphasis is on the influence of CO and NO. In addition, the homogeneous nitrogen chemistry of fluidized bed combustion and the selective noncatalytic reduction of NO (SNR) are discussed. The rate of N2O decomposition in N2 agrees with a first-order rate expression. The presence of CO or H2 increases the decomposition rate regardless of the additional presence of O2 For the formation of N2O, HCN oxidation is more efficient than NH3 oxidation. The presence of NO increases the amount of N2O formed during the oxidation of HCN or NH3.CO moves the N2O formation toward lower temperatures. H2O increases the reaction rate where few components are present, whereas H2O has little influence in the presence of large amounts of a combustible component such as CO. There are indications that NO is a necessary intermediate for any significant formation of N2O during the oxidation of NH3 and HCN. NO reduction is obtained when NO is initially present during oxidation of both NH3 and HCN. These results are comparable to the respective SNR results with reductant ammonia and urea.

Nitrous oxide (N2O) emissions from various combustion systems was measured by use of two analytical methods, the performance of which was evaluated together with the sampling procedures. One analytical method is grab sampling followed by analysis by gaschromatography (GC). This procedure was found to give accurate results, provided SO2 and H2O were removed during sampling in order to avoid N2O formation in the sample. An evaluation of a continuous infrared N2O analyzer shows that it is a useful instrument if measures are taken to eliminate or adjust for interferences from CH4, SO2, H2O, and to a minor extent also from NH3. A considerable formation of N2O was found when a gas containing SO2 and NO was scrubbed in a weak acid solution. The sampling program from a variety of combustion systems revelas that N2O emissions usually are low (0–5 ppm) from the combustion of pulverized coal. The results from a gas turbine, a laboratory gas-fired fiber burner, and a domestic oil combustor are also in the very low range, whereas emissions from combustion of straw or wood were slightly higher. Even higher emissions were observed from circulating fluidized bed combustion (CFBC), from which the level of emissions increased with decreasing combustion temperature and increasing excess air levels. Sampling inside the CFBC reactor showed that N2O formation is particularly rapid at the transition from reducing to oxidizing conditions at the secondary air inlet. Pilot plant experiments with the selective non-catalytic reduction of NO by urea or ammonia resulted in a large increase in N2O emissions during the injection of urea, whereas almost no increase was found during the injection of ammonia.

For the purpose of developing a simple and quantitative description of the rate of reactions occurring in the Thermal DeNOx process, the kinetics of the homogeneous reaction between NO and NH3 with excess of O2 has been studied in an isothermal plug flow reactor. Temperature windows of NO reduction were observed with the optimum temperature decreasing with increasing residence time. The degree of reduction of NO increases with residence time at lower temperatures but is sensitive to residence time only at very short residence times at higher temperatures. The degree of conversion of NH3 increases with both temperature and residence time. A simple model has been proposed to describe the reaction rates: rNO = kax [NH3] - kr [NH3] [NO] r =-kax [NH3]- kr [NH3] [NO] The two rate constants in the model were estimated based on the experimental data obtained in the present plug flow reactor at about 4% (vol.) oxygen: kax = (2.21 ± 0.33) × 1014 exp [-(38160 ± 170)/T], I/s kr = (2.45 ± 0.49) × 1014 exp [-(29400 ± 250)/T], m3mol. s It is verified that the kinetic model can give a satisfactory prediction of the experimental results under different conditions. Afin de mettre au poǐnt un modele de description simple et quantitatif de la vitesse des rections survenant dans le processus thermique DeNOx, on a etudia la reaction homogene entre NO et NH3, avec exces de O2: dans un reacteur a ecoulement piston isotherme. Les gammes de temperatures pour la reduction du NO ont ete observees, et on a constate que la temperature optimale diminuait avec l'augmentation du temps de sejour. Le degre de reduction du NO augmente avec le temps de sejour aux temperatures inferieures mais cette sensibilite s'observe seulement a des temps de sejour tres courts et des temperatures elevees. Le degre de conversion du NH3 augmente a la fois avec la temperature et le temps de sejour. On propose un modele simple pour decrire les vitesses de reaction: rNO = kax [NH3] - kr [NH3] [NO] r =-kax [NH3]- kr [NH3] [NO] Les deux constantes de vitesse du modele ont ete estimees a partir des donnees experimentales obtenues avec le reacteur a ecoulement piston utilise ici a environ 4% (volume)d'oxygene: kax = (2.21 ± 0.33) × 1014 exp [-(38160 ± 170)/T], I/s kr = (2.45 ± 0.49) × 1014 exp [-(29400 ± 250)/T], m3mol. s On a pu demontrer que le modele cinetique peut predire de maniere satisfaisante les resultats experimentaux dans differentes conditions.

Biofouling on ship hulls is prevented by the use of antifouling (A/F) paints. Typically, sea water soluble rosin or rosin-derivatives are used as the primary means of adjusting the polishing rate of the current chemically active self-polishing paint systems to a suitable value. Previous studies have shown that mathematical coating models based on a fundamental knowledge of the underlying mechanisms of A/F paints is a promising tool for accelerated product testing at different operational conditions of a sailing ship or a paint rotor. Such models can also be used for generation of ideas aiming at product optimisation and innovation (e.g. incorporation of natural active agents). This study seeks to attain scientifically founded knowledge of the reaction mechanisms and the rate of reaction with sea water of a Zn-carboxylate of a synthetic rosin compound. The kinetic expression attained can be used as input to mathematical models describing the behaviour of rosin-containing tin-free A/F paints. The experimental procedures developed can be easily implemented by marine paint companies for the screening of novel controlled-release binder materials for A/F paints. As a first step, it is demonstrated that the degradation of this Zn-containing rosin-derivative by sea water plays a key role in the polishing mechanism of paints formulated with such a resin. Then, the relevant literature available on the sea water behaviour of rosin and rosin-based binders is reviewed. Subsequently, two experimental procedures for the reaction rate estimation of the selected rosin-derived resin are presented; one is based on a gravimetric approach while the other uses flame atomic absorption spectroscopy (FAAS) to determine the total Zn 2+ released by the resin. Both methods yield well-defined reaction conditions and sufficiently high accuracies. The latter is important because very low steady state reaction rates (about 0.70 ± 0.26 μg Zn 2+ cm −2 day −1 at 25 °C and pH 8.2) are measured. Steady state reaction rates of Cu 2+ - and Mg 2+ -derivatives are also determined and discussed. The experimental procedures developed are used to investigate the influence of NaCl concentration (12–52 g/l), pH (7.8–8.5) and sea water temperature (10–35 °C) on the rate of reaction of the Zn-carboxylate. Within that range of sea water conditions, the following kinetic expression is found to describe the steady state Zn 2+ release rate resulting from the reaction of the Zn-carboxylate with sea water: ( − r ZnR ) = k 1 C O H − a − k − 1 C R − b C Z n 2 + c μ g Z n 2 + ( c m 2 film ) day k 1 = A e ( − E a / R T ) μ g Z n 2 + ( c m 2 film ) day 1 mol a k − 1 = k 1 C O H − a L ZnR 2 b − 2 ( C Z n 2 + ) eq b + c − 3 μ g Z n 2 + ( c m 2 film ) day 1 mol b + c where the natural logarithm of the pre-exponential factor, ln ( A ), is 18.0 ± 2.5 (the unit of A being the same as k 1 ), the activation energy, E a , is 18.5 ± 6.0 kJ/mol and the reaction order with respect to the hydroxide ion concentration, a , is 0.86 ± 0.42. L ZnR is the estimated solubility product of the ZnR resin which has a value of 3.1 × 10 −12 (mol/l) −3 (about 6 mg Zn 2+ /l in equilibrium). The low value of the activation energy is believed to result from the complex reaction mechanisms hypothesised rather than pointing at a certain diffusion control in the reaction rate experiments. The reverse reaction is found not to affect the hydrolysis rate within the pores of antifouling paints significantly. It is concluded, from the reaction mechanism proposed, that the observed partial exchange of Zn 2+ for Cu 2+ in the resin structure during paint dispersion and immersion results in a lower reaction rate compared to the pure ZnR. Cu-carboxylate has a reaction rate of about 5.8 ± 1.0 μg CuR cm −2 day −1 at 25 °C and pH 8.2. The presence of Mg and Na compounds (probably Mg- and Na-resinate) in the solid paint film has also been detected, and will influence the reaction rate by modifying the ZnR exposed surface area.