This paper presents a method for quantitative assessment of the mechanisms of nucleation and granules growth by layering in the process of bed wetting during periodic disc granulation. This study included two initial, consecutive stages of a process with defined time courses. The first phase was a time period, in which only formation of new nuclei took place, while in the second stage simultaneous nucleation and growth of granules as a result of sticking raw material grains to pre-existing nuclei occurred. Different kinds of binding liquid were used for bed wetting in each phase. In the first phase, an aqueous solution of dye was used, and pure distilled water in the second stage. The contribution of particular mechanisms to the formation of agglomerates at different time points within the second phase of the process was determined in this study. To do that the results of bed granulometric analysis, mass balance of size fractions and the analysis of contents of a marker (dye) delivered to the bed with the binding liquid during the first phase in agglomerates were used. To assess the concentration of the dye in different size fractions of the batch, spectrophotometric analysis was utilised. The study was performed using UV-VIS JASCO V-630 spectrophotometer equipped with an integrating sphere. The sieve analysis, spectrophotometric studies and mass balance were used to determine changes in the weight of the dye containing nuclei and of the nuclei containing no dye. The aforementioned analyses were also used to assess changes in the weight of formed granules and of raw material particles attached to nuclei during simultaneous nucleation and growth of granules.
Analysis of granulation kinetics was carried out using a laboratory disc granulator with a diameter D of 0.5 m. A liquid binder was delivered to the tumbling bed at a constant flow rate with a nozzle generating droplets with a size of approx. 4-5 mm. Fine-grained chalk was used as a model of raw material and water or disaccharide solution with concentrations of 20 - 40% as a wetting liquid. Different times of droplet delivery ranging from 2 to 6 min were utilized. Granulometric composition of the bed for selected lengths of process, bed moisture and the moisture of individual size-fractions were assessed. Mass of granulated material, which was transferred from nuclei fraction to other size fractions was determined on the basis of mass balance analysis and the assessment of liquid migration between fractions. The influence of disaccharide concentration in wetting liquid on the aforementioned phenomena was also examined.
This paper presents the results of experimental drum granulation of silica flour with the use of wetting liquids with different values of surface tension. Additionally, different liquid jet breakup and different residual moisture of the bed were applied in the tests. The process was conducted periodically in two stages: wetting and proper granulation, during which no liquid was supplied to the bed. The condition of the granulated material after the period of wetting (particle size distribution and moisture of separate fractions) and a change in the particle size distribution during the further conduct of the process (granulation kinetics) were determined.
The results of investigations of the granulation process of foundry dusts generated in the dry mechanical reclamation process of used sands, where furan resins were binders are presented in the paper. Investigations concerned producing of granules of the determined dimensions and strength parameters. Granules were formed from the dusts mixture consisting in 50 mass% of dusts obtained after the reclamation of the furane sands and in 50 mass % of dusts from sands with bentonite. Dusts from the bentonite sands with water were used as a binder allowing the granulation of after reclamation dusts from the furane sands. The following parameters of the ready final product were determined: moisture content (W), shatter test of granules (Wz) performed directly after the granulation process and after 1, 3, 5, 10 days and nights of seasoning, water-resistance of granules after 24 hours of being immersed in water, surface porosity ep and volumetric porosity ev. In addition the shatter test and water-resistance of granulate dried at a temperature of 105oC were determined. Investigations were performed at the bowl angle of inclination 45o, for three rotational speeds of the bowl being: 10, 15, 20 rpm. For the speed of 10 rpm the granulation tests of dusts mixture after the preliminary mixing in the roller mixer and with the addition of water-glass in the amount of 2% in relation to the amount of dust were carried out. The obtained results indicate that the granulator allows to obtain granules from dusts originated from the reclamations of moulding sands with the furane resin with an addition of dusts from the bentonite sands processing plants.
The application of fluidized fly ash in underground mining excavations is limited due to its significant content of free calcium and calcium sulfate. In order to increase the amount of utilized fly ash from fluidized beds, it should be converted to a product with properties that meet the requirements for mining applications. This research presents the results of an attempt to adapt fluidized fly ashes for use in underground mining techniques, by means of carbonation and granulation. Carbonation was performed with the use of technical carbon dioxide and resulted in the reduction of free calcium content to a value below 1%. Granulation on the other hand, resulted in obtaining a product with good physical and mechanical parameters. The performed mineralogical and chemical studies indicate that trace amounts of “binding” phases, such as basanite and/or gypsum are present in the carbonized ash. The addition of water, during the granulation of carbonized fluidized fly ash, resulted in changes in the mineral phases leading to the formation of ettringite and gypsum as well as the recrystallization of the amorphous substance. It was confirmed that the carbonization and granulation of flying fluidized ashes positively affects the possibility of using these ashes in underground mining excavations.
With the increase in wall thickness of the casting of iron-nickel-aluminium-bronze, by the reduction of the cooling rate the size of κII phase
precipitates increases. This process, in the case of complex aluminium bronzes with additions of Cr, Mo and W is increased. Crystallization
of big κII phase, during slow cooling of the casting, reduces the concentration of additives introduced to the bronze matrix and hardness.
Undertaken research to develop technology of thick-walled products (g> 6 mm) of complex aluminium bronzes. Particular attention
was paid to the metallurgy of granules. As a result, a large cooling speed of the alloy, and also high-speed solidification casting a light
weight of the granules allows: to avoid micro-and macrosegregation, decreasing the particle size, increase the dispersion of phases in
multiphase alloys. Depending on the size granules as possible is to provide finished products with a wall thickness greater than 6 mm by
infiltration of liquid alloy of granules (composites). Preliminary studies was conducted using drip method granulate of CuAl10Fe5Ni5
bronze melted in a INDUTHERM-VC 500 D Vacuum Pressure Casting Machine. This bronze is a starting alloy for the preparation of the
complex aluminium bronzes with additions of Cr, Mo, W and C or Si. Optimizations of granulation process was carried out. As the process
control parameters taken a casting temperature t (°C) and the path h (mm) of free-fall of the metal droplets in the surrounding atmosphere
before it is intensively cooled in a container of water. The granulate was subjected to a sieve analysis. For the objective function was
assume maximize of the product of Um*n, the percentage weight "Um" and the quantity of granules 'n' in the mesh fraction. The maximum
value of the ratio obtained for mesh fraction a sieve with a mesh aperture of 6.3 mm. In the intensively cooled granule of bronze was
identified microstructure composed of phases: β and fine bainite (α+β'+β'1) and a small quantity of small precipitates κII phase. Get high
microhardness bronze at the level of 323±27,9 HV0,1.
Significant quantities of coal sludge are created during the coal enrichment processes in the mechanical processing plants of hard coal mines (waste group 01). These are the smallest grain classes with a grain size below 1 mm, in which the classes below 0.035 mm constitute up to 60% of their composition and the heat of combustion is at the level of 10 MJ/kg. The high moisture of coal sludge is characteristic, which after dewatering on filter presses reaches the value of 16–28% (Wtot r) (archival paper PG SILESIA). The fine-grained nature and high moisture of the material cause great difficulties at the stage of transport, loading and unloading of the material. The paper presents the results of pelletizing (granulating) grinding of coal sludge by itself and the piling of coal sludge with additional material, which is to improve the sludge energy properties. The piling process itself is primarily intended to improve transport possibilities. Initial tests have been undertaken to show changes in parameters by preparing coal sludge mixtures (PG SILESIA) with lignite coal dusts (LEAG). The process of piling sludge and their mixtures on an AGH laboratory vibratory grinder construction was carried out. As a result of the tests, it can be concluded that all mixtures are susceptible to granulation. This process undoubtedly broadens the transport possibilities of the material. The grain composition of the obtained material after granulation is satisfactory. Up to 2 to 20 mm granules make up 90–95% of the product weight. The strength of the fresh pellets is satisfactory and comparable for all mixtures. Fresh lumps subjected to a test for discharges from a height of 700 mm can withstand from 7 to 14 discharges. The strength of the pellets after longer seasoning, from the height of 500 mm, shows different values for the analyzed samples. The values obtained for hard coal sludge and their blends with brown coal dust are at the level from 4 to 5 discharges. The strength obtained is sufficient to determine the possibility of their transport. At this stage of the work it can be stated that the addition of coal dust from lignite does not cause the deterioration of the material’s strength with respect to clean coal sludge. Therefore, there is no negative impact on the transportability of the granulated material. As a result of mixing with coal dusts, it is possible to increase their energy value (Klojzy-Karczmarczyk at al. 2018). The cost analysis of the analyzed project was not carried out.
Hard coal sludge is classified as group 01 waste or it is a by-product in the production of a hard coal with variable energy importance. Pulverized lignite is not waste but a final product of drying and the very fine pulverization of lignite with a high calorific value. The study comprised the basic material before granulation such as coal sludge (PG SILESIA) and pulverized lignite (LEAG) as well as their prepared blends after the granulation on a pipe vibration granulator designed at AGH. The pulverized lignite of the LEAG company shows a low sulfur contents. In the analyzed samples its average content (Stot d) is 0.61%. An average value of this parameter in the analyzed coal sludge samples is 0.55%. The addition of pulverized lignite does not have a significant impact on the total content of sulfur and of analyzed toxic elements (Hg, As, Cd, Cr, Co, Cu, Mn, Ni, Pb, Sb, Tl, and W) in the samples. The calorific value of coal sludge falls within the range of 11.0−12.4 MJ/kg (on a dry basis). For the coal sludge and pulverized lignite blends the calorific value clearly increases to values of 14.8−17.7 MJ/kg (on dry basis). The calorific value slightly decreases in the
The new legislative provisions, regulating the solid fuel trade in Poland, and the resolutions of
provincial assemblies assume, inter alia, a ban on the household use of lignite fuels and solid fuels
produced with its use; this also applies to coal sludge, coal flotation concentrates, and mixtures
produced with their use. These changes will force the producers of these materials to find new
ways and methods of their development, including their modification (mixing with other products
or waste) in order to increase their attractiveness for the commercial power industry. The presented
paper focuses on the analysis of coal sludge, classified as waste (codes 01 04 12 and 01 04 81)
or as a by-product in the production of coals of different types. A preliminary analysis aimed at
presenting changes in quality parameters and based on the mixtures of hard coal sludge (PG SILESIA)
with coal dusts from lignite (pulverized lignite) (LEAG) has been carried out. The analysis
of quality parameters of the discussed mixtures included the determination of the calorific value,
ash content, volatile matter content, moisture content, heavy metal content (Cd, Tl, Hg, Sb, As, Pb,
Cr, Co, Cu, Mn, Ni, and W), and sulfur content. The preliminary analysis has shown that mixing
coal sludge with coal dust from lignite and their granulation allows a product with the desired quality
and physical parameters to be obtained, which is attractive to the commercial power industry.
Compared to coal sludge, granulates made of coal sludge and coal dust from lignite with or without
ground dolomite have a higher sulfur content (in the range of 1–1.4%). However, this is still an
acceptable content for solid fuels in the commercial power industry. Compared to the basic coal
sludge sample, the observed increase in the content of individual toxic components in the mixture
samples is small and it therefore can be concluded that the addition of coal dust from lignite or carbonates
has no significant effect on the total content of the individual elements. The calorific value
is a key parameter determining the usefulness in the power industry. The size of this parameter for
coal sludge in an as received basis is in the range of 9.4–10.6 MJ/kg. In the case of the examined
mixtures of coal sludge with coal dust from lignite, the calorific value significantly increases to
the range of 14.0–14.5 MJ/kg (as received). The obtained values increase the usefulness in the
commercial power industry while, at the same time, the requirements for the combustion of solid
fuels are met to a greater extent. A slight decrease in the calorific value is observed in the case of
granulation with the addition of CaO or carbonates. Taking the analyzed parameters into account,
it can be concluded that the prepared mixtures can be used in the combustion in units with flue gas
desulfurization plants and a nominal thermal power not less than 1 MW. At this stage of work no
cost analysis was carried out.