Modification of Fe–Mn mixed oxide COS removal sorbent by rare-earth oxides addition

In order to develop highly active sorbent for COS removal, Fe–Mn mixed oxides doped with CeO₂, La₂O₃ or Sm₂O₃ were studied. The effects of these promoters on the structural properties of Fe–Mn oxides were investigated by XRD, BET, TPR and TEM techniques. XRD results revealed that the degree of crystallinity of Fe–Mn oxide phase decreased due to the addition of rare-earth oxides. Doping with CeO₂, La₂O₃ or Sm₂O₃ led to an increase in BET surface area of the sample. TPR studies showed that the reactivity of the reduction of doped samples increased in the temperature range of 300–450 °C. In addition, the desulfurization test was performed at 325 °C with a gas hourly space velocity of 1000 h⁻¹. It was found that the addition of 3% La₂O₃ greatly improved the absorption sulfur capacity of the sorbent, while the sorbent doped 3% CeO₂ achieved a sufficiently high purifying degree before breakthrough.     

Two-stage biodegradation coupled with ultrafiltration for treatment of municipal landfill leachate

The municipal landfill leachate was treated in a hydrolysis–acidification reactor (HAR)/aerobic bio-contact oxidation reactor (ABOR) following a pretreatment with ultrafiltration (UF) membrane. Experiments were conducted continuously for 44 days at a constant flow rate of 20 l d⁻¹ and organic loading rates (OLRs) from 0.75 to 1.5 kgCOD m⁻³ per day. The results showed that COD of the leachate steadily decreased from 20,015 mg l⁻¹ to less than 3000 mg l⁻¹, and NH₄-N decreased from 368.6 mg l⁻¹ to 259.3 mg l⁻¹ in the UF process. The COD and NH₄-N removal efficiency of HAR was 56.7% and 27.7%, and that of ABOR was 94.6% and 86.7%, respectively. The total COD and NH₄-N removal efficiency reached 99.6% and 93.2%, respectively. UF and HAR played a critical role in raising the biodegradability of the landfill leachate, while ABOR had an important function on removing the dissolved NH₄-N in leachate.     

A comparative study of the effect of clay binders on iron oxide sorbent in the high-temperature removal of hydrogen sulfide

The purpose of this study is to investigate the effect of clay binder, an important additive, on the performance of iron oxide sorbent in high temperature coal gas desulfurization. The four clay binders chosen for the study were kaolinite, diatomite, bentonite and brick clay. The sulfidation–regeneration cycles were conducted in a fixed-bed reactor. XRD, DTA and FTIR, together with texture characterizing techniques, such as mercury porosimetry and nitrogen adsorption, were adopted to characterize the sorbents and raw materials. The results obtained show that sorbents prepared from various clay binders exhibit different breakthrough behaviors. In addition, a correlation between pore volume and sulfur capacity reveals that sorbents with a greater number of pores larger than 200 nm (diameter), exhibit higher sulfur capacity. The reason for this is that a greater number of large pores can improve diffusion and provide a larger space for relieving heat impact. However, too many large pores may result in weak strength and very low bulk density, thus a balance between large pores and the density must be achieved. This study also reveals that clay binder can contribute to the modification of a sorbent's texture as gas is released when the mineral structure changes during calcination. In addition, a clay mineral with an active interlayer has been shown to be beneficial in improving the dispersion of active components in the sorbent, because of the existence of an interaction between the mineral and red mud.     

Electrowinning studies for metallic zinc production from double leached Waelz oxide

Waelz oxide is a zinc and lead concentrate pyrometallurgically derived from electric arc furnace dust. There are clear incentives to leaching and purify this oxide to produce liquors that can be electrowinned to obtain recycled metallic zinc. This study is focused on this electrolytic zinc production from previously obtained sulphuric liquor. This liquor was obtained from double leached Waelz oxide (DLWO) throughout a hydrometallurgical process. The electrolytic liquor, after the corresponding leaching and purification stages, contains around 49 kg/m³. This liquor was fed to an electrowinning process where platinum or lead anodes and aluminium cathodes were used. After optimizing the different electrowinning critical parameters, and working at these optimal conditions, almost 88 secondary zinc kg were precipitated per each initial DLWO tonne in one-through process. The zinc purity was higher than 99.5%. After some mass balance calculations, it can be concluded that, optimizing the process configuration through internal recycling, around 210 Zn kg/DLWO t with purity near to 100% could be achieved.     

Absorption kinetics of NO from simulated flue gas using Fe(II)EDTA solutions

The absorption of NO encountering flue gases in aqueous solutions of Fe(II)EDTA was determined using a semi-batch stirred tank with a plane gas–liquid interface at 50 °C. The concentrations of NO, SO₂ and O₂ in the feeding stream were 300–800 ppm, 500–2200 ppm and 0–20%, respectively. The pH value of the Fe(II)EDTA solutions varied from 3 to 11. The concentrations of Fe(II)EDTA were maintained between 0.01 and 0.05 M. Experiments were performed to evaluate the effect of operating parameters on the NO absorption rate, the reaction kinetics of the reactants in gas and liquid phases, and the effect of competition between various reactants on the mass transfer rate in the NO removal system. Results indicate that the average reaction rate constant is 3.70 × 10⁷ M⁻¹ s⁻¹. Adding NaOH does not increase the absorption capability of Fe(II)EDTA. The presence of O₂ decreases the NO absorption rate with Fe(II)EDTA. The absorption rate of NO with Fe(II)EDTA decreases at low concentrations of SO₂, but increases at high concentrations.     

Improved VOC bioremediation using a fluidized bed peat bioreactor

A gas–solid fluidized bed bioreactor was successfully used to treat air contaminated with a volatile organic compound (VOC). A bioreactor containing both a fluidized and packed bed of moist peat granules removed ethanol, a representative VOC, from an air stream. The fluidized bed operation mode of the bioreactor outperformed the packed bed mode. The maximum elimination capacity (EC) of ethanol in the fluidized mode was 1520 g m⁻³ h⁻¹, with removal efficiencies ranging between 45 and 100%, at loadings up to 3400 g m⁻³ h⁻¹. Maximum EC was 530 g m⁻³ h⁻¹ in the packed bed mode. Removal efficiency in the fluidized bioreactor was best at the lowest velocity, where the bubbling bed fluidization regime predominated. As gas velocity increased, the size and amount of large bubbles (slugs) increased and removal efficiency decreased while elimination capacity increased.     

High nitrite accumulation and strengthening denitrification for old-age landfill leachate treatment using an autocontrol two-stage hybrid process

An autocontrol two-stage hybrid process was developed to treat landfill leachate. Biological nitrogen removal with nitrification and denitrification via nitrite pathway was split into two stages. The first stage was designed for the high nitrite accumulation and was composed of two hybrid bed reactors (Hybrid I and Hybrid II) and a coagulation–flocculation reactor having effective volumes of 120 L and 80 L, respectively. The second stage was designed for strengthening denitrification and included a single 80 L reactor. The carriers of the hybrid bed reactors were composed of fixed multiple flexible carriers and suspended particle carriers. Dissolved oxygen (DO), pH value, oxidation–reduction potential (ORP) and temperature were used as online fuzzy control parameters of the automatic control system. The concentration of nitrite in Hybrid I and Hybrid II could reach 411 mg L⁻¹ and 604 mg L⁻¹, respectively. Ammonia removal has reached maximal rates of 0.061 kgNH₄⁺-N (m³ h)⁻¹ and 0.041 kgNH₄⁺-N (m³ h)⁻¹, respectively. A maximum nitrite removal rate of 0.211 kgNO₂⁻-N (m³ h)⁻¹ was observed during the strengthening denitrification. The running time of one cycle was not fixed and was actually controlled by the system. The results indicated that the running period was more closely related to influent ammonia concentration than influent COD concentration. The aeration times could be shortened and the energy could be saved. The autocontrol two-stage hybrid process is therefore an economical and effective way for landfill leachate treatment.     

Effect of cycle time on biodegradation of azo dye in sequencing batch reactor

The effects of cycle time on the biodegradation of the azo dye remazol brilliant violet 5R (RBV-5R) were investigated in an anaerobic–aerobic sequencing batch reactor (SBR). System performance was determined by monitoring chemical oxygen demand (COD), color, anaerobic enzyme (azo reductase) and aerobic enzyme (catechol 2,3-dioxygenase), and aromatic amine concentration. SBR was operated in three different total cycle times (48 h, 24 h and 12 h), fed with a synthetic textile wastewater. In this study, the anaerobic period of SBR was found to allow the reductive decolorization of azo dye and the aerobic period was found to be effective on further COD removal after the anaerobic period. The percentage reductions in color by the anaerobic stage of the SBR were at 72%, 89% and 86% for the 24-h, 12-h and 6-h cycle times, respectively. Total COD removal efficiencies were over 75% for all operational conditions and about 70% of the COD removal was achieved in the first 3 h of anaerobic stages. During the decolorization of RBV-5R, two sulfonated aromatic amines (benzene-based and naphthalene-based) were formed and detected by HPLC. Aerobic phases of SBR with total cycle times of 48 h, 24 h and 12 h were able to remove benzene-based aromatic amines with removal efficiency of 64%, 92% and 89%, respectively. The results indicated that the best SBR performance in terms of color removal and aromatic amine degradation was achieved from total cycle time of 24 h.     

Numerical simulation of flue gas desulfurization characteristics in CFB with bypass ducts

A new process of flue gas desulfurization in circulating fluidized bed with flue gas bypass ducts is presented. k–? Model, Discrete Phase Model and Finite-Rate Chemistry Model are proposed to simulate the desulfurization process characteristics in circulating fluidized bed reactor. The proposed model is validated by the comparison of experimental data and simulation results. The results show that the desulfurization reactor with bypass ducts is superior to the reactor without bypass ducts. The reactor with bypass ducts has higher desulfurization efficiencies and lower flow resistances than the reactor without bypass ducts, and it is more suitable for flue gas flow variation. Desulfurization reaction rate is controlled by absorption reaction on sorbent particles surface. When water content and Ca/S ratio increase, desulfurization efficiency of the reactor with bypass ducts increases. When SO₂ concentration increases, desulfurization efficiency decreases.     

Explosion behavior of n-alkane/nitrous oxide mixtures

The explosion properties of alkane/nitrous oxide mixtures were investigated and were compared with those of the corresponding alkane/oxygen and alkane/air mixtures. The explosion properties were characterized by three parameters: the explosion limit, explosion pressure, and deflagration index. For the same alkane, the order of the lower explosion limits (LELs) of the mixtures was found to be alkane/oxygen ≈ alkane/air > alkane/nitrous oxide. In addition, the mixtures containing nitrous oxide tended to exhibit higher explosion pressures than the corresponding mixtures containing oxygen under fuel-lean conditions. The Burgess–Wheeler law was also observed to hold for the mixtures containing nitrous oxide.     

Fire risk management system for safe operation of large atmospheric storage tanks

This paper has been prepared by its authors to show the benefits coming from the application of the fire risk assessment methodology prepared by the “LastFire^© Project” group of experts. Now a days this methodology seems to be very effective to face the fire risk connected with large atmospheric storage tanks. It has been developed during the period 1997–2005 the HSE & operations experts from experts 16 worldwide operating oil companies. The authors, by “ad hoc” created software package, show the benefit coming from the applications of the LastFire^© methodology and how, from this, using the methodology and the supporting tad, realize a coherent fire strategy in the form of a Fire Risk Management System. Same workflow could also be extended to the issues connected with other problems related with large atmospheric tanks storing hydrocarbons, such as environmental impact by soil pollution, to create a common frame walk of assessment not can be shared with authorities as well. The proposed methodology, moving from the original project, sets as an effective “Fire Hazard Management Approach” in line with the most recent trends (even enforced by the regulations) shared at international levels, that propose the integration of risk assessment with prevention and protection measures selection based on achieved risk reduction, costs, time needed, etc.     

Removal of Zn and Ni by adsorption in a fixed bed of wheat straw

Zn⁺² and Ni⁺² in a solution were removed by biosorption in a fixed bed of wheat straw Triticum aestivum. The removal rate and the mass transfer coefficient for Zn⁺² and Ni⁺² were found to be proportional to the liquid superficial velocity to the power of 0.31 for the range of the particle Reynolds number from 18 to 445 (equivalent liquid rates of 0.00070–0.0175 m³ m⁻² s⁻¹). This agrees well with reported literature for mass transfer in a packed bed of solid particles under a laminar flow regime. Effect of the solution pH, temperature and the particle size (0.5, 1.0, 1.5 and 2.0 in.) on biosorption of Zn⁺² and Ni⁺² was also investigated. Biosorption of both Zn⁺² and Ni⁺² increased significantly with the solution pH from 4.0 to 7.0. On the other hand, Zn⁺² and Ni⁺² removal appeared to be insensitive to liquid temperature from 25 to 30 °C. Nevertheless, a 25% increase in the percentage removal of metal ions was observed with further increase of liquid temperature from 30 to 35 °C. However, the biosorbent particle size did not seem to have a systematic effect on the biosorption of Zn⁺² and Ni⁺². In addition, biosorption of Zn⁺² was not affected considerably by co-adsorption of the bimetal solution while biosorption of Ni⁺² decreased about 14%.     

Preliminary study of ballistic impact on an industrial tank: Projectile velocity decay

Since the events of September 11, 2001, the possibility of an intentional act targeting the chemical process industry has become realistic. It is, therefore, a great concern to be able to predict the immediate consequences of such an act. This study is intended to improve our knowledge about the sequence of events that occurs when a high-speed bullet (>1000 m s⁻¹) penetrates a vessel filled with toxic liquid. We find that, prior to liquid ejection, several well-defined phases occur, including the phenomenon known as the “hydraulic ram.” This paper focuses on projectile–target interactions and explains how the decay of projectile velocity is related to the initial conditions of the target.     

Biodiesel production from waste oil feedstocks by solid acid catalysis

Biodiesel is a non-toxic and biodegradable substitute for petroleum-based diesel. However, it is impractical to use refined edible oils to produce biodiesel due to its high cost and priority for food products, especially in China, while waste oils with high free fatty acids (FFAs) can be considered as the raw materials. In the present work, a solid acid catalyst comprising SO₄²⁻/TiO₂–SiO₂ was prepared, characterized and studied for its activity for the production of biodiesel from several low cost feedstocks with high FFAs. The solid acid catalyst can be recycled, easily removed and can simultaneously catalyze esterification and transesterification. The influence of reaction parameters was studied, and the optimized reaction parameters are reaction temperature 200 °C, molar ratio of methanol to oil 9:1 and catalyst concentration 3 wt.%. The catalyst showed good stability. A continuous process for biodiesel production from cheap raw feedstocks was proposed, and a 10,000-tonnes/year biodiesel production demonstration plant has been built.     

The influence of temperature on the deactivation of commercial Pd/Rh automotive catalysts

Automotive catalyst deactivation can be promoted by thermal and poisoning mechanisms. Catalyst efficiency is reduced by thermal degradation resulting in the agglomeration of precious metals and the reduction of the washcoat surface area. In this paper, the temperature influence on the commercial Pd/Rh-based automotive catalyst performance was studied. Textural and physicochemical characterisation techniques were employed, such as X-ray fluorescence (XRF), atomic absorption spectrometry (AAS), N₂ physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM–EDX). The catalysts were evaluated for CO and propane oxidation with a stoichiometric gas mixture similar to engine exhaust gas. The results indicated the transformation of alumina into high temperature phases and the formation of new mixed oxide phases. Evidence of sintered particles and several spots of palladium agglomerates was seen by SEM–EDX analysis. The activity results showed the effects of thermal deactivation on the conversion of the pollutants. In spite of exposure to extreme temperature conditions (72 h at 1200 °C), significant activity was still observed for carbon monoxide and propane oxidation reactions.     

Mass balance of anionic surfactants through up-flow anaerobic sludge blanket based sewage treatment plants

The outcome of a 21-month monitoring study on anionic surfactants (AS) at five (27–70 ML/d) up-flow anaerobic sludge blanket (UASB) based sewage treatment plants (STPs) is described. The average removals of AS were around 8–30%. Appreciable concentrations of AS were being discharged to the watercourse (average 4.30 mg/L; range 3.60–4.91 mg/L). On an average dried sludge contained 1452 mg AS/kg dry weight. Mass balance at three STPs indicated that, AS load of the order of 5–17% and ≈12% is removed by adsorption in UASB reactors and polishing ponds (PP) respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation (≈46%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100 units, than average of ≈74 and ≈7 units are discharged with treated effluent and dried sludge respectively, while 12 and 6 units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds respectively. At two STPs (34 and 56 ML/d), the filterable fluxes in UASBR increased so that the mass balance could not be computed.     

Laboratory study using paper mill lime mud for agronomic benefit

Annual ryegrass (Lolium perenne L.) is an important cool-season forage grass in the southeastern US. Since large portions of soils in this region are too acidic for optimum ryegrass production, there exists an opportunity to use lime mud waste from numerous regional pulp and paper mills as an agricultural liming material. In this study, four lime mud application rates, 2.25 (L₁), 4.51 (L₂), 9.01 (L₃), and 22.50 (L₄) ton ha⁻¹, dry weight basis, and a control (L₀) were evaluated for response to ryegrass growth during the first 6 weeks to estimate an optimum application range over the testing soil for future field test. Results indicated that applied lime mud slowed ryegrass germination and seedling emergence, with differences of whole plant length among treatments L₀–L₄ significant only during the first three weeks. Differences of whole plant dry weight among treatments L₀–L₄ reduced thereafter. The initial soil pH increase due to the lime mud application dropped in treatments L₁–L₄ by the end of the 6-week experiment. The optimum lime mud application range was estimated between L₂ and L₃, which provided higher ryegrass yields (kg ha⁻¹) of 84 and 80 over 77 of the control and complied with the Code of Federal Regulation, CFR 40 Part 503 for land application.     

Recovery from work‐related effort: A meta‐analysis

This meta‐analytic study examines the antecedents and outcomes of four recovery experiences: psychological detachment, relaxation, mastery, and control. Using 299 effect sizes from 54 independent samples (N = 26,592), we extend theory by integrating recovery experiences into the challenge–hindrance framework, creating a more comprehensive understanding of how both after‐work recovery and work characteristics collectively relate to well‐being. The results of meta‐analytic path estimates indicate that challenge demands have stronger negative relationships with psychological detachment, relaxation, and control recovery experiences than hindrance demands, and job resources have positive relationships with relaxation, mastery, and control recovery experiences. Psychological detachment after work has a stronger negative relationship with fatigue than relaxation or control experiences, whereas control experiences after work have a stronger positive relationship with vigor than detachment or relaxation experiences. Additionally, a temporally driven model with recovery experiences as a partial mediator explains up to 62% more variance in outcomes (ΔR² = .12) beyond work characteristics models, implying that both work characteristics and after‐work recovery play an important role in determining employee well‐being.     

Deterioration of the useful visual field with ageing during simulated driving in traffic and its possible consequences for road safety

A previous study has shown that the useful visual field deteriorates in a simulated road traffic situation as a function of the driver’s age and of the vehicle’s speed under monotonous conditions [Rogé, J., Pébayle, T., Lambilliotte, E., Spitzenstetter, F., Giselbrecht, D., Muzet, A., 2004. Influence of age, speed and duration of monotonous driving task in traffic on the driver’s useful visual field. Vision Research 44 (23), 2737–2744]. The aim of this new experiment is to study the effects of traffic density and age on the useful visual field of the driver during a simulated driving task with controlled traffic characteristics (speed, number of cars) for all participants. In total, 10 young drivers (m = 28.2 years) and 10 older drivers (m = 51.2 years) followed a car in road traffic at an average speed of 126 km h⁻¹ during two 2 h sessions corresponding to two conditions of traffic (light traffic, with five vehicles around the participant; and heavy traffic, with nine vehicles). While following this vehicle, the driver had to detect changes in the colour of a signal located in the central part of his or her visual field and a signal that appeared at different eccentricities on the rear lights of other vehicles in the traffic. Analysis of the data indicated that age interacted with the location of the peripheral signal and density of traffic interacted with the duration of driving. The implications of these results are discussed in terms of road safety and in terms of models of deterioration of the useful visual field (general interference and tunnel vision).     

Physical and transport properties of aqueous amino alcohol solutions for CO2 capture from flue gas streams

Densities, viscosities and refractive indices of 4-diethylamino-2-butanol + water mixtures were measured over the entire concentration range of 0–1 mole fraction and temperature range from 298.15 to 343.15 K. Excess molar volumes, viscosity deviations, and molar refraction changes were calculated from the measurement results and correlated as a function of the mole fractions. Various models were used for correlation with the measured data. Out of these, the Redlich–Kister equation was the most suitable model that correlated best with experimental data. The percent absolute deviations obtained with this model were 0.03% for density, 0.88% for viscosity and 0.009% for refractive index.