Wet Pellets Research Articles

Sewage sludge enhances cold-pressed pelletization and carbothermic reduction of steel plant sintering dust

The sludge-based forming thermal reduction can be used to improve the resource utilization ability of sintering dust. This paper discussed the feasibility and mechanism of sewage sludge as a binder and reducing agent to facilitate iron recycling from sintering dust by mixing wet sludge to form and adding dry sludge to reduce. The results showed that a 1.4% ratio of sewage sludge significantly enhanced the strength of metallurgical pellets, and the compressive strength of wet and dry pellets reached 309.5 and 1233.5 N/P. Meanwhile, with the addition of dry sludge (S/Fe = 2.0), the metallization ratio can be up to 88.4%. Sewage sludge has a more efficient reduction potential than other carbon sources as reducing agents. Combined with XRD, XPS, TG-MS, TG-FTIR, and other characterization methods, the reduction phenomenon of iron was confirmed, and the migration and transformation of metals in sintering dust and the segmented volatilization rule of Pb, Zn, K, Na, and other elements were revealed. It is proven that sludge as the disposal route of metallurgical dust cold-pressed forming and reduction is a green and sustainable view and promising research direction.

Sustainable fodder production and optimization of cow feeding rations in the ar-id climate of southern Ukraine

In the south of Ukraine, which traditionally belongs to the zone of risky land use due to frequent droughts and the last 10–15 years of steadily progressing global warming, the production of rye silage as a basic feed ingredient is gaining the status of an excellent insurance fund, which is essential in the region's feed production, as it will help to remedy the situation with the shortage of juicy fodder. Optimisation of dairy cow feeding rations during lactation in southern Ukraine involves the use of traditional dietary ingredients (corn silage, alfalfa haylage) and innovative ones (rye silage, wet beer pellets), which is mainly due to climate change in recent years. The research used commonly available methods: zootechnical (setting up experiments, developing feed rations, assessing dairy cattle productivity, milk quality, reproduction rates); biological (morphological and biochemical composition of blood); statistical (biometric processing of data) and economic analysis of the research. Thus, in terms of actual milk yield, amount of milk fat and milk protein for 305 days of lactation, cows of all experimental groups outperformed analogues of the control group (milk yield for 305 days of lactation was 7898.0 l; amount of milk fat and protein – 278.7 and 245.1 kg, respectively) by 1.2–3.3 %, by the amount of milk fat – by 5.1–16.9 % and by the amount of milk protein – by 3.4–10.9 % for 305 days of lactation. It was found that the diets of dairy cows of the experimental groups, which included rye silage in different amounts and wet beer pellets, had a positive effect on reducing the duration of the service period, and hence the duration of the intercalation period by 5.5–27.0 days in animals of the I–IV experimental groups compared to cows of the control group. There was a tendency to increase the content of carotene in the blood serum of animals of the II experimental group by 39.5 %, as well as a significant difference of 72.7 % (P < 0.05) and 81,3% (P < 0.01), respectively, in cows of the III and IV experimental groups compared to the same indicator of the control group, which was 209.6 μg/100 ml.

Reproduction and commercial cultivation of chinese perch <i>Siniperca chuatsi</i> in conditions of a warm-water farm

A breeding stock of chinese perch was gotten in a warm-water farm located in the southern Far East of Russia, where the experiment is conducted on growing this species up to three years. Combined method of growing in tanks, warm-water fry ponds and cages was used for growing the fingerlings, but two- and three-year old perches were kept in cages only and fed with live and non-living low-value forage fish. There were attempts to train two-year-old perch to feed on wet artificial pellets. By the end of the experiment, three-year-old chinese perches of two size groups had the body weight of 700−880 g with the maximum of 1600 g. Feed costs for the growth of two- and three-year-old fish in the growing seasons were 2.7−3.9 and 5.3−5.6 kg per 1 kg gain, respectively; their survival was 98−100 %. In 2023, the two-year-old perches weighing 0.5−1.1 kg were used for the first time in spawning and their offspring were raised to an average weight of 60 g.

Investigation of Jamming Phenomenon in a Direct Reduction Furnace Pellet Feed System Using the Discrete Element Method

A continuous iron ore pellet feed system for a direct reduction ironmaking furnace is reportedly jamming in a hopper above the furnace, where a counterflowing gas seals off the furnace flue gas. The conditions that result in jamming are not well understood. The system is computationally modeled utilizing the coupled discrete element method (DEM) and computational fluid dynamics (CFD) technique. The technique is computationally expensive; therefore, the pellet sizing is modified while preserving the key metrics important in jamming. The model is used to study the impact of pellet moisture, heating, and ice formation between pellets in relation to the jamming event. The results indicate that the influence of moisture alone on the bulk shear rate is unlikely to jam the system and that insufficient heat is supplied by the counterflowing gas to raise the temperature of the pellets, which suggests freezing conditions can exist within the hopper. Particle bonding is implemented to replicate wet and icy pellets freezing and breaking up. The results indicate that the system jams in winter conditions when the hopper is charged with a minimum of 15% icy pellets, or 10% icy with 5% wet pellets. These results agree with industry reports of jamming during winter operations.

Characteristic and kinetic study of the hot air-drying process of artificial limonite pellets

BackgroundLimonite pellets, primarily composed of Fe2O3·nH2O, are a crucial raw material for modern iron-making techniques. In order to produce high-quality pellets, a pre-drying and roasting process is necessary. This is because wet pellets can absorb heat during the water evaporation process, which can lead to uneven temperature distribution in the blast furnace. MethodsIn this study, we investigated the hot air-drying processes of limonite pellets. Specifically, we examined the impacts of temperature and air speed on pellet quality, weight loss, moisture content, and drying rate to identify optimal drying process parameters for artificial limonite pellets. Additionally, we analyzed the drying kinetics of synthetic limonite pellets using experimental data. Significant FindingsThe results show that the drying rates of the pellets increase with temperature and wind speed and that Correction Page(III) is suitable for the kinetic drying model of synthetic limonite pellets. This research provides important theoretical and practical insights into drying limonite pellets in real-world production processes.

Assessment anti-granuloma activity of Alpha-lipoic acid in chicks’ models

Background: Alpha-lipoic acid is an anti-inflammatory and antioxidant agent that has free radical scavenging characteristics as well as better effects on the recycling of other cellular antioxidants.Aim: The present study was made to assess the anti-granuloma of Alpha-lipoic acid by the cotton pellet granuloma method.Method: The chicks weighing around 100-150 g were selected, the Alpha-lipoic acid was administered at the following dose of 20, 40 & 80 mg/kg body weight respectively after insertion of cotton pellets into the groin region of chicks.Results: By using the up-and-down technique, it was found that the Median Lethal Dose (LD50) of the Alpha-lipoic acid was 451.8mg/kg, IP. Alpha-lipoic acid at 20, 40, and 80 mg/kg per body weight daily for consecutive seven days revealed that the ALA shows dose-dependent inhibition of weight of both wet and dry cotton pellets. The inhibition percentage for wet cotton pellets was 5, 11, and 14 respectively whereas the inhibition percentage for dry cotton pellets was 9, 15, and 25 respectively. Conclusion: We conclude that Alpha-lipoic acid has notable anti-granuloma activity as compared to control in animal models of chronic inflammation. Additional studies must be done to find the molecular role of Alpha-lipoic acid as anti-granuloma remedies

Evaluation of the Processing of Multi-Crop Plants into Pelletized Biofuel and Its Use for Energy Conversion

Multi-crop plants (fibrous hemp, maize, and faba bean) can potentially be an alternative to wood biomass pellets, but there is no detailed knowledge to support the suitability of this biomass for solid biofuel production. The aim of this study is to analyze and justify the suitability of multi-crop plant biomass for the production of biofuel pellets and to assess the environmental impact of burning them. This paper presents studies of physical-mechanical, thermal, and chemical characteristics of biofuel pellets from multi-crop plants and emissions during their combustion under laboratory conditions. The main parameters of the produced pellets were determined according to international standards, which are detailed in the methodology part. The length of the produced pellets ranged from 17.6 to 26.6 mm, and the diameter was about 6 mm. The density of wet pellets varied from 1077.67 to 1249.78 kg m−3. The amount of ash in the pellets varied from 5.75% to 8.02%. Determined lower calorific value of all pellets was close to 17.1 MJ kg−1. The lowest CO and CxHy emissions were determined when burning MIX2-1 pellets (biomass of the binary crop); their values were 572 and 29 ppm, respectively. The lowest content of CO2 was determined when burning S-Mz pellets (mono crop biomass), and it was 3.5%. The lowest NOx emissions were also determined when burning the pellets of this sample, with a value of 124 ppm. Research results show that multi-crop plants are a suitable raw material for the production of solid biofuel, the burning of which does not cause negative consequences for the environment.

The introduction of wet dyeing sludge pellets in the production of clay brick: A novel approach to promote the disposal efficiency

The introduction of dyeing sludge in the fired brick production is an economic and practical disposal approach. Wet dyeing sludge with high moisture usually produces block mass during mixing process of raw materials, not only reduces the production efficiency but negatively impacted products engineering properties. This study proposed a highly efficient method, wet sludge firstly being pelleted and then introduced in the production of fired bricks, to reduce the negative impacts on mixing process and the products quality. It was proved that the introduction of dyeing sludge pellets remarkably improved physical and mechanical properties of fired bricks. Especially, water absorption declined by 12% and compressive strength increased by 35% comparing with dyeing sludge without pelleting. The engineering properties of fired bricks containing 25 wt% sludge pellets are similar with that containing 15 wt% sludge without pelleting. The decrease in water absorption and porosity is mainly attributed to the reduction in number and volume of pores with diameter below 100 nm. It was considered that pellets with greater density and higher strength might play a role as aggregate to improve compressive strength. However, the introduction of sludge pellets with particle size over 8 mm is adverse to improving properties of products, because a large amount of macropore with diameter over 100 μm is produced, and destroys the homogeneous and compact structure of products. The optimal sludge pellet size is in the range of 2–6 mm based on products performance. The leaching toxicity of heavy metals from products is far lower than regulatory limitation. This study provides an advanced method to promote the disposal efficiency of solid waste and improve the engineering quality of products.

The Potential Migrated Mechanism of Water-Soluble Components in Pellets Prepared by Wet Extrusion/Spheronization: Effect of Drying Rate.

At present, there are numerous researches on the migration of components in tablets and granules, however, the investigation in the pharmaceutical literatures concerning the effect of drying rate on the migration of water-soluble components of pellets is limited. Temperature and Relative Humidity (RH) are crucial parameters during the drying process, which is an essential step in the preparation of pellets via wet extrusion/spheronization. To quantify these variables, the water loss percentage of pellets per minute is defined as the drying rate. The study aimed to investigate the influence of drying rate on the migration of water-soluble components in wet pellets and the potential migrated mechanism. The pellets containing tartrazine as a water-soluble model drug and microcrystalline cellulose as a matrix former were prepared by extrusion/spheronization and dried at four different drying temperatures and relative humidity. Afterwards, the extent of migrated tartrazine was assessed regarding appearance, in-vitro dissolution test, Differential Scanning Calorimetry, X-Ray Powder Diffraction, Attenuated total reflectance Fourier transform infrared spectroscopy and Confocal Raman Mapping. Results demonstrated that red spots of tartrazine appeared on the surface of pellets and more than 40% tartrazine were burst released within 5 minutes when pellets were dried at 60°C/RH 10%. When pellets were dried at 40°C/RH 80%, none of these aforementioned phenomena were observed. In conclusion, the faster the drying rate was, the more tartrazine migrated to the exterior of pellets. Adjusting drying temperature and relative humidity appropriately could inhibit the migration of water-soluble components within wet extrusion/spheronization pellets.

Wet route pellets production using primary sludge from kraft pulp mill

Abstract The substantial expansion of the Brazilian pulp and paper industry in the last years resulted in a significant increase in the solid waste generation. This paper investigates the production of pellets using primary sludge from the effluent treatment plant of a kraft pulp mill, as a fuel for producing energy, using a novel wet route process. The pellet samples were produced in a laboratory pelletizing press, which has a horizontal circular matrix. The samples were characterized by moisture content, high heating value, ash content, dimensions (diameter and length), mechanical durability and fines content. The net heating value and energetic density were also measured. The pellets manufactured with primary sludge were compared to the European standard for non-woody pellets. Pelletization caused a reduction of the moisture content by 37.8 %, and increased the net heating value by 41 % and bulk density by approximately 39 %, which resulted in a 263 % increase in the material´s energetic density. Pellet production using a wet route process was appropriate for the primary sludge, and produced pellets with a high mechanical durability (99.3 %) and low fines content (0.062 %), indicating the potential of thermal valorization for incineration in the biomass boiler to produce high-quality steam.

Comparative Study on Induration of Wet Iron Ore Pellets in Different Straight Grate Furnaces in Iran Using Mathematical Models

The current study presents mathematical modelling of the pellet induration process in several straight-grate pelletizing plants in Iran. The change in the essential parameters includes gas and pellet temperature, moisture, and oxidation rate for pellets in three drying, sintering, and cooling stages in the pelletizing plants of Gohar Zamin, Gol Gohar Sangan, Mobarakeh steel and Khuzestan steel. This article is validated by a semi-industrial study conducted by Mobarakeh Steel Company. By using this model, the oxidation of magnetite is followed by sintering of the oxidized magnetite. The results show that the magnetite oxidation for the lower layers of the pellet about 11% is less than the upper layers. This model can enhance induration productivity, optimise fuel costs, reduce power consumption, control gas temperature and pressure, and as an operator training simulator. This simulation also helps the control room monitor the conversion percentage of magnetite to hematite in pellets and extract the best for the oxidation rate.

Pellets from Biogas Digestates: A Substantial Source of N2O Emissions

The field application of pellets from biogas residues resulted in high N2O emissions which could not yet be parametrized through soil drivers. Therefore, the aim of this study was to determine potential N2O production from pellets themselves. N2O and CO2 release from the pure pellet body (in form of intact, crushed or finely ground pellets produced from biogas digestates) were measured during the first seven days after pellet wetting under constant laboratory conditions. Three pellet water contents were examined: 47, 62 and 72% water of the total fresh pellet weight. Additional replicates of similarly wetted intact pellets were used to determine NH4+, NO3− and DOC contents on days 0, 1 and 4 of incubation. Two further treatments of wet intact pellets (62% moisture) were sterilized prior or after moistening to investigate the emissions’ origin. N2O release was found to increase with decreasing pellet size fraction. A maximum of N2O fluxes within all three fractions was determined at 62% moisture, whereas lowest fluxes were measured at 72% moisture. The cumulative N2O emissions over seven days ranged between 1 µg N2O–N g−1 pellet (intact pellets at 72% moisture) and 166 µg N2O–N g−1 pellet (finely ground pellets at 62% moisture). In general, our findings indicate that denitrification was the main factor for N2O emissions, driven by indigenous microbial communities already present in the pellets. The results show that the N2O emissions released by the pellets themselves can explain a major portion of the N2O fluxes measured in situ.Graphic

Electronic Transport in the Biopigment Sepia Melanin.

Eumelanin is the most common form of the pigment melanin in the human body, with diverse functions including photoprotection, antioxidant behavior, metal chelation, and free radical scavenging. Melanin also plays a role in melanoma skin cancer and Parkinson's disease. Sepia melanin is a natural eumelanin extracted from the ink sac of cuttlefish. Eumelanin is an ideal candidate to eco-design technologies based on abundant, biosourced, and biodegradable organic electronic materials to alleviate the environmental footprint of the electronics sector. Herein, the focus is on the reversible electrical resistive switching in dry and wet Sepia eumelanin pellets, pointing to the possibility of predominant electronic transport satisfying conditio sine qua non to develop melanin-based electronic devices. These findings shed light on the possibility to describe the transport physics of dry eumelanin using the amorphous semiconductor model. Results are of tremendous importance for the development of sustainable organic electronics.

Influence of the type and output of domestic hot-water boilers and wood moisture on the production of fine and ultrafine particulate matter

Abstract The Ministry of the Environment of the Czech Republic within the Operational Programme Environment of the European Union (EU) has supported a ‘grant to replace old boilers’ from 2015 to 2020. The aim was to replace outdated, non-ecological, solid-fuel boilers with modern low-emission boilers (for the combustion of biomass, coal, or a combination), heat pumps, gas boilers, or solar systems. All heat sources must comply with the Ecodesign Directive of the EU. According to the Air Protection Act in the Czech Republic, commencing in 2022, outdated boilers of the 1st and 2nd emission classes will no longer be operable in households. The grant also aimed to reduce particulate matter (PM), organic gaseous compounds, and CO and NOx emissions. Our goal was to compare the PM emissions of four boilers: an outdated overfire boiler (B1), an outdated boiler with down-draft combustion (B2), a new gasification boiler (B3), and a new automatic boiler (B4). A Dekati low-pressure cascade impactor was used to determine the mass concentration of individual dust fractions; a scanning mobility particle sizer SMPS 3936 was utilized to determine the particle size distributions of the dust particles. Dry and wet spruce wood and wood pellets were combusted. Regarding the mass concentration of the PM and specific emissions (SE) of individual size fractions, they were much higher in boilers of older types (B1 and B2), while the reduction in SE of PM was very significant in boilers of newer types (B3 and B4). However, the SE of ultrafine particles (PM0.1) from the newer boilers remained in a range similar to that of B1 at a reduced output (Pmin) and B2.

Study of bentonite clays influence on quality indicators of pellets

Quality of iron ore pellets depends on many factors, including the type and properties of binding materials, in particular, bentonite clays. Laboratory studies of bentonite clays, differing by mineralogical composition and exchange ion complex. To assess the metallurgical characteristics of the pellets obtained with various kinds of binders, the moisture of the pellets, the compressive strength of the wet and dry pellets, the number of the wet pellets discards without destroying, and the “shock” temperature were determined. The carried out tests have shown that the impact strength and compression resistance of wet pellets at a slightly increased specific consumption of bentonite of cherkasy alkaline-earth bentonite does not concede to the correspondent properties of pellets with application of alkaline saryugyshsky bentonite as the binder. It was shown that clays of the IV layer, which are a natural mixture of alkaline-earth bentonite of the II layer and palygorskite III layer of the Cherkassky deposit, are favorable, to ensure good quality of the raw pellets. Tests of composite mixtures of clays IV with II and II with III layers showed that the quality of raw pellets with cherkassky bentonite is slightly worse comparing with sarygyuhsky one, however, the absolute values of their indicators satisfy the industry requirements. Tests of pelletizing of charges with different wetness, with the addition of 0.5% alkaline bentonite and a mixture of clays of the IV and II layers of the cherkassky deposit were carried out. It was shown, that with wetness increasing, pellets with both types of binder additives show the increase of the dynamic strength, porosity and temperature of the “shock” with a minimum difference in the absolute values of indicators with different binders. For confirmation of the possibility of using alkaline-earth bentonite of the Cherkassky deposit (II–III–IV layers) in the production of pellets, it is necessary to accomplish comparative industrial tests at a pelletizing plant (for example, at SevGOK), which uses a concentrate and industrial water of increased hardness.

Study of the influence of different types of bentonite clays on the quality indicators of pellets

Objective: to analyze and determine the influence of bentonite clays of different deposits and exchange ionic complexes on the metallurgical properties of iron ore pellets. Methods: performing rheological studies of bentonite clay samples and their chemical analysis, electron microscopic studies of samples. To assess the metallurgical characteristics of the pellets obtained, the moisture of the pellets, the compressive strength of the wet and dry pellets, the number of dumpings without destroying the wet pellets, and the temperature of the «shock» have been determined. Results: laboratory tests were conducted to determine the suitability of bentonite clays of different mineralogical composition and exchange ion complex for the production of pellets. Tests have shown that the impact resistance and compression resistance of raw pellets at a slightly increased specific consumption of bentonite Cherkasy alkaline-earth bentonite does not concede to the same properties of pellets with the use as a binder alkaline Saryugyhsky bentonite. It is demonstrated that to ensure good quality of raw pellets, an auspicious variety of clays of the Cherkasy deposit are clays of the IV layer, which are a natural mixture of alkaline-earth bentonite of the II layer and palygorskite (III layer). Tests of composite mixtures of clays IV with II and II with III layers showed that the quality of raw pellets with Cherkassky bentonite is slightly worse than with Sarygyuhsky, however, the absolute values of their indicators satisfy the industry requirements. Comparative tests of pelletizing of charges with different humidity and with the addition of 0.5% alkaline bentonite and a mixture of clays of the IV and II layers of the Cherkassky deposit have been carried out. It is shown that with increasing humidity in granules with both types of binders, the dynamic strength, porosity and temperature of the “impact” of granules increase with a minimum difference in the absolute values of indicators with different binders. To objectively confirm the possibility of using alkaline-earth bentonite of the Cherkassky deposit (II-III-IV layers) in the production of pellets, it is necessary to conduct comparative industrial tests at a pelletizing plant (for example, SevGOK), using a concentrate with the in-creased hardness of industrial water. Scientific novelty: the influence of alkaline bentonite replacement in charge for pellet production with alkaline earth, paligorskite clays and mixtures of their forms has been studied. The comparative influence of moisture content of raw pellets on their porosity and strength characteristics with alkaline and alkaline earth bentonites in the charge was studied. Practical significance: using the properties of raw, dry and calcined pellets as an example, the possibility of using less scarce and expensive local bentonite clays instead of expensive exported alkaline clays without impairing the production technology and characteristics of the pellets is shown.

Synthesis, characterisation and preliminary corrosion behaviour assessment of simulant Fukushima nuclear accident fuel debris

ABSTRACTNuclear fuel debris generated at the Fukushima Daiichi nuclear power plant during the loss of coolant accident in 2011, still resides within the reactor units, constantly cooled by water. Until it is retrieved, the fuel debris will corrode, releasing radioactive elements into the coolant water and the ground surrounding the reactors. To predict the corrosion behaviour of these materials, and to establish parameters for experiments with U-containing and real fuel debris, the corrosion of two surrogate fuel debris materials, with a composition of Ce(1-x)ZrxO2 (x = 0.2 and 0.4), was investigated. Materials were synthesised by a wet chemistry route and pellets were sintered at 1700°C in air atmosphere. Due to the slow corrosion kinetics, aggressive conditions were applied, and corrosion experiments were performed in 9 mol.L-1 HNO3 under static conditions. The incorporation of Zr into the structure of Ce reduced the normalised dissolution rate; from (3.75 ± 0.15) × 10-6 g.m-2.d-1 to (4.96 ± 0.28) × 10-6 g.m-2.d-1 for RL(Ce) of Ce0.8Zr0.2O2 and Ce0.6Zr0.4O2, respectively.

Mechanistic understanding regarding the functionality of microcrystalline cellulose and powdered cellulose as pelletization aids in wet-extrusion/spheronization

Powdered cellulose (PC) and microcrystalline cellulose (MCC) show considerable different behavior during wet-extrusion and spheronization. While MCC is an appropriate pelletization aid, PC is not suitable. The differences were explained by either the “molecular-sponge” or the “crystallite-gel” hypothesis. To elucidate the differences in functionality, the effect of several polar solvents on liquid–solid interaction with PC and MCC was investigated. In addition, PC was homogenized via high pressure homogenization to reduce particle size without affecting the degree of polymerization. Mixer torque rheometry (MTR), laser diffraction and texture analysis were used to characterize the behavior of PC and MCC in wet pastes, suspensions and pellets. PC and MCC interacted differently with solvents like dimethyl sulfoxide, dimethylformamide and several glycols during MTR experiments. While PC mainly swells in appropriate solvents, MCC showed a particle size reduction, partly into colloidal dimensions. Solvents that induced liberation of colloidal fibers, also enabled a wet-extrusion/spheronization process. The quantity of colloidal cellulose only had minor effect on the resulting pellet quality. Also, the properties of the used solvent had only minor impact on the pellet size, shape and mechanical stability. PC contained small amounts of colloidal fibers after high pressure homogenization. With this pre-treated PC, wet-extrusion/spheronization process was also possible although the pellet quality is inferior to MCC pellets. Colloidal cellulose fibers have a major impact on the behavior of wet mass and on the feasibility for pellet production via wet-extrusion/spheronization. These insights provide new evidence for the “crystallite-gel” model.

A contact model for the deformation behaviour of pharmaceutical pellets under cyclic loading

Spherical pharmaceutical pellets are commonly produced by an extrusion-spheronization process. In the spheronizer, the wet cylindrical extrudates are rounded into spheres due to multiple collisions. In order to model this rounding, a suitable contact model, which can predict the dominantly plastic deformation behaviour, is necessary. In this study, a novel cyclic model for wet and dry pellets was developed. Various single particle compression and impact tests with pellets produced from microcrystalline cellulose (MCC) and lactose were conducted to calibrate and validate this model. It was found that the model is able to predict the energy dissipation as well as the deformation during pellet impact in the velocity range which is relevant for the spheronization process. Since the pellets are loaded multiple times during this process, the model was designed in order to account for the increasing flattening and hardening in the contact area as a function of the number of loading cycles. Therefore, the presented model allows the description of the pellet deformation by repeated stressing.

Comparison of Miniaturized Raman Spectrometers for Discrimination of Carotenoids of Halophilic Microorganisms.

We present a comparison of the performance of four miniature portable Raman spectrometers for the discrimination of carotenoids in samples of carotene-producing microorganisms. Two spectrometers using a green laser allowing to obtain Resonance Raman (or pre-Resonance Raman) signals, one instrument with a 785 nm laser, and a recently developed Portable Sequentially Shifted Excitation Raman spectrometer (PSSERS) were used for identifying major pigments of different halophilic (genera Halobacterium, Halorubrum, Haloarcula, Salinibacter, Ectothiorhodospira, Dunaliella) and non-halophilic microorganisms (Micrococcus luteus, Corynebacterium glutamicum). Using all the tested instruments including the PSSERS, strong carotenoids signals corresponding to the stretching vibrations in the polyene chain and in-plane rocking modes of the attached CH3 groups were found at the correct positions. Raman spectra of carotenoids can be obtained from different types of microbiological samples (wet pellets, lyophilized culture biomass and pigment extracts in organic solvents), and can be collected fast and without time-consuming procedures.