Solid Impurities Research Articles

Justification of design-mode parameters separating device

In Kazakhstan, the basis of the country's food security is livestock products. Increasing the production of livestock products is impossible without creating a strong feed base, high-quality preparation of feed, rational use and reduction of feed losses. Preparation of coarse stem feed for feeding requires grinding with feed grinding and mixing machines to obtain balanced feed mixtures. The grinding process is complicated by the fact that, along with coarse stem feed, foreign solid impurities enter, which damage the cutting organs of machines and cause a long shutdown of the entire feed preparation line, disruption of the feeding schedule, and reduction in animal weight gain and milk yield. These problems are of particular relevance in the development of small farms with a low level of mechanization. The authors have developed a device for separating foreign solid impurities from coarse stem feeds, the novelty of which is confirmed by a patent for an invention of the Republic of Kazakhstan. The article theoretically substantiates the influence of the design and operating parameters of the separating device for cleaning stem feed from foreign solid impurities. To separate foreign solid impurities from bound materials, such as stem feed, the most effective are separators with working bodies in the form of an air flow. In separators of this type, differences in the totality of physical and mechanical properties are used to separate foreign impurities from stem feeds. This approach makes it possible to achieve better separation by mechanical devices and expect their development towards the use of as many combinations of the distinctive properties of the separated components as possible.

SEARCH FOR METHODS TO INCREASE THE SEDIMENTATION RATE OF THE UPPER FLOATING LAYER OF OIL SLUDGE PITS

Traditionally, oil sludge with a liquid-viscous consistency is separated into petroleum product, water and solid mechanical impurities. A large number of technological devices, including separators, centrifuges, hydrocyclones of various designs, have been developed to carry out the operation of interfacial separation of liquid-viscous oil sludge.On the territory of every oil refinery that has been in operation for decades, there are oil sludge ponds — natural settling ponds in which large quantities of oil waste accumulate.The problem of processing barn oil sludge in the oil production and refining industry has not yet been completely solved. This is due to the high stability of barn emulsions, the peculiarities of their composition and properties, which are constantly changing under the influence of temperature and various processes occurring in them.The article presents the results of research aimed at identifying the possibility of destruction of a persistent oil-water emulsion taken from the upper floating layer of an oil sludge pit and its preparation without changing the technological scheme and technological parameters.The results of laboratory studies on the destruction of oily liquid during static sedimentation are considered. Simulation of the oily liquid preparation process was carried out in compliance with the temperature and time conditions of operation, with the use of demulsifiers, by analogy with the process of oily liquid preparation, as at the unit. The results of the simulation showed that at the dosage of the demulsifiers used at the unit, even with an increase in the dosage and an increase in the settling time to 5 days, the oil-water emulsion did not collapse at 60 0C. Further studies were carried out by testing eight brands of demulsifiers at different dosages and elevated temperatures. Based on the results of the research and the conclusions made, a scheme for the preparation of oil-containing liquid at static sludge with the existing set of equipment at the unit is proposed.Further studies were carried out to increase the depth and sedimentation rate of the persistent oil-water emulsion.

Rapid treatment of LLZTO solid electrolyte surface impurities by lactic acid solution

Abstract LLZO solid-state electrolytes of the garnet type exhibit exceptional electrochemical stability towards lithium metal and possess a remarkable level of ionic conductivity, and thus are considered to be one of the most promising solid-state electrolytes for solid-state lithium-ion batteries. However, LLZO is unstable in humid air and reacts with H2O and CO2 in the air to form Li2CO3, which reduces the wettability with lithium metal and decreases the overall ionic conductivity of LLZO. In this paper, a novel, fast, and simple method, lactic acid treatment, is proposed. The results show that Li2CO3 on the LLZO surface can be completely removed by acid treatment for 30 seconds, resulting in a pure LLZTO surface and improved wettability with lithium metal. Meanwhile, the assembled lithium symmetric battery can be cycled stably for 240 hours at 0.2 mA/cm2.

Development of a new reagent for the prevention of asphaltene-resin-paraffin deposits

Asphaltene-Resin-Paraffin deposits (ARPD) form a certain proportion of the crude oil mass, separating as temperature and pressure decrease and adsorbing to the surfaces of the reservoir wellbore zone, downhole equipment and tubulars. These deposits precipitate in the wellbore zone, oilfield equipment and pipes,resulting in reduced system productivity, reduced pumping efficiency of the pumping equipment and other negative consequences. Asphalt-resin and paraffin deposits (ARPD) are a complex mixture of solid paraffin hydrocarbons, asphalt-resin substances (ARS), water and mechanical impurities. The strength and composition of ARPD depend on the composition and properties of oil, geological, physical and technological conditions of field development. Chemical methods for removing deposits are currently the most widely used, as they are highly effective and technologically advanced. To this end, new reagents have been developed and their physico-chemical properties have been studied. Subsequently, the selected reagents were tested on oil samples from Oil and Gas Production Department (OGPD) with a paraffin content of more than 6 %. It was also shown that paraffin inhibitors have individual effects; a reagent that is effective on oil from one field may not have the same effect on oil from other fields. The research includes studies of selected reagents for paraffinic oils from different fields. Using the «cold finger» method, the efficacy of the selected reagents against paraffin deposition was investigated and their optimum doses were determined. Keywords: reagent; sendiment; paraffin; asphaltene; resin; well bottom zone; viscosity; depressor.

Aspects Regarding of Oil Sludge Cleaning from Crude Storage Tanks Using Robots

One of the problems of the oil industry is the accumulation of sludge at the bottom of crude oil storage tanks. Oil sludge obtained from crude oil storage tanks is a semi-solid waste. It is actually a complex emulsion made up of numerous petroleum hydrocarbons, water and solid particles or mineral impurities from the rock. Oil sludge is generated during the storage of crude oil production, but also during the transportation, storage, and refining of crude oil. Through its nature - organic and inorganic, dark brown / black in color and semi-fluid physical state - it is a very dangerous waste, as it includes many poisonous substances, such as: polycyclic aromatic hydrocarbons, xylene, benzene, ethyl benzene, toluene, but also metals heavy. Therefore, oil sludge deposition is a dynamic, long-term, and ever-changing process. The authors, under the auspices of AOȘR and AGIR, present - through this scientific paper - a modern technology used for the successful cleaning of oil sludge from crude oil storage tanks and, obviously, it can be a recommendation for organizations in the oil industry.

A numerical study on the effect of particle surface wettability on homogeneous and heterogeneous condensation processes in supersonic flows

Supersonic separators are an emerging device for processing natural gas impurities. Natural gas contains solid particulate impurities in addition to gaseous impurities, which can trigger heterogeneous condensation within the supersonic separator. There is a lack of research on the effect of particle wettability on supersonic condensation flow, although there have been studies on the effect of particle surface wettability on heterogeneous condensation in this area. Therefore, in this paper, the supersonic condensation flow is modeled considering the contact angle, and the effects of particle contact angle on heterogeneous condensation and homogeneous condensation are investigated separately. The results show that homogeneous condensation is inhibited and heterogeneous condensation is promoted by decreasing the particle contact angle. The reason is the smaller contact angle leads to the reduction of the free energy barrier for heterogeneous nucleation, which makes the conditions for heterogeneous nucleation lower and condensation more likely to occur.

CO2 capture utilizing Li4SiO4 from spent lithium-ion batteries and iron tailings offers eco-friendly benefits

Carbon capture and storage stand as a pivotal technology in the battle against global climate change. The development of economically viable CO2 capture materials, coupled with the recycling of solid wastes, poses a significant challenge in the pursuit of carbon neutrality. Herein, we propose a process to synthesize a promising high-temperature sorbent, Li4SiO4, using spent lithium-ion batteries and iron tailings. Li4SiO4 synthesized under optimal process conditions demonstrates exceptional CO2 capacity and cycle stability (0.25 g/g, 100 cycles), with a preparation cost merely amounting to 1/7 of traditional methods, rendering it industrially feasible. Moreover, elucidating the intricate relationship between impurity elements in the feedstock and the CO2 capture capacity of the adsorbent holds considerable significance in guiding material synthesis strategies. A systematic evaluation of solid waste purity and impurity elements on CO2 capture capacity, through a combination of experiments and theoretical calculations, reveals that lower purity solid waste containing favorable impurities (96.78 % Li2CO3 and 90.35 % SiO2) enhances the CO2 capture efficiency of the synthesized Li4SiO4. This innovative work establishes a direct link between trace impurities and macroscopic properties, providing a viable decarbonization pathway and fostering high-value secondary utilization of solid waste under short and economical processes.

Experimental Study on Vacuum Distillation Separation Characteristics of Tar Containing Solid Particles: Distributions of Light Components.

The impacts of the composition and properties of tar products on their utilization are of great importance, while the consequences of varying tar separation conditions on distillation fractions remain underexplored. Solid impurities in special tar products (e.g., subsurface in situ pyrolysis-derived tar-like substances) can contribute to the separation as well. In the present study, low-temperature coal tar (LTCT) was used as an analogue to pyrolysis product, mixed with semi-coke and coal dust, representing pyrolytic byproducts and nonpyrolytic substances, respectively. The LTCT mixtures were tested with vacuum distillation at various pressures and temperatures. The results revealed the role of pressure in fraction distribution across temperatures, with higher pressure concentrating fractions at lower temperatures. The impact of solid impurities on distillation primarily stemmed from adsorption. Minimal concentrations of solid impurities carried coal dust/semi-coke into the distillation, but higher levels retained them in the residue. The adsorption of coal dust was quite high at lower temperatures and waned as temperature increased, unlike semi-coke, which had consistent adsorption throughout the distillation. The present study can advance the understanding of vacuum distillation for tar products in the presence of solid impurities, offering a framework for the effective distillation/utilization of coal tar. By probing separation conditions, tar properties, and solid impurity effects, the present research will refine strategies for optimizing coal tar use, crucial for enhancing energy security and sustainable progress in China.

Optical measurements of solid nitrogen solubility in hydrogen at cryogenic temperatures

The solubility of impurities in hydrogen at cryogenic temperatures is essential information for the design of liquid hydrogen plants. However, large data scatter and inconsistent predictions of impurity solubility by thermodynamic models mean that expensive engineering design margins are required to avoid blockages in cryogenic equipment. Here we report the combination of a stereomicroscope, commercial cryocooler and pressure cell to directly visualise solid impurity freeze-out and melting in stirred hydrogen at low temperatures and elevated pressures. Scattered literature data for nitrogen's solubility in hydrogen are compared to new solid-fluid equilibrium (SFE) measurements for a 1000 ppm N2 in H2 mixture at (1.8–5) MPa, and (42–52) K. These results were used to improve solubility models implemented in the ThermoFAST software package, achieving a three-fold decrease in the root-mean-square deviations between the SFE predictions and the data, helping lower the risk of impurity freeze-out in hydrogen liquefaction.

A TGA-FTIR study on the pyrolysis of oil-based drilling cuttings and the influence of its solids on pyrolysis characteristics

During the drilling process in oil and gas fields, rock cuttings and other solid impurities are returned to the wellhead along with oil-based drilling fluids, forming oil-based drill cuttings. Organic pollutants in oil-based drill cuttings can be removed through pyrolysis. Although there has been some research on the pyrolysis of oil-based drilling cuttings, there is little analysis of the impact of rock-solid impurities in oil-based drill cuttings on the pyrolysis of organic components. Therefore, in this study, thermogravimetry coupled with infrared spectroscopy was used to analyze the pyrolysis characteristics of oil-based drill cuttings, exploring the major volatile components at different pyrolysis temperatures. Meanwhile, the oil and solids in oil-based drilling cuttings were separated by Soxhlet extraction, and the influence of solids on pyrolysis characteristics was studied. The results showed that the average pyrolysis activation energy and pre-exponential factor of the main pyrolysis stage of oil-based drill cuttings obtained by the FWO method were 50.6 KJ/mol and 3.951×104 s−1, respectively, while those of the separated residual oil were 84.7 KJ/mol and 2.905×109 s−1, respectively. This indicates that solids in oil-based drilling cuttings is increasing the mass loss rate during pyrolysis. The difference in pyrolysis kinetics between oil-based drilling cuttings and residual oil indicates that the solid in oil-based rock cuttings provides a surface for the reaction, which provides a reaction site for the decomposition of hydrocarbons to produce lighter volatile hydrocarbons. Additionally, the results of infrared spectroscopy indicated that the volatile products of the pyrolysis of oil-based drilling cuttings include CH4, CO, CO2, H2O, aldehydes, organic acids, etc. CH4 is the main product of the first weight loss stage, mainly released between 150°C and 200°C. With the increase in temperature, the concentrations of H2O, CO2, aldehydes, and organic acids gradually increased. At 600°C, the maximum concentration of CO2 release occurred, and the release of CO2 was the main reason for the third-stage weight loss in the pyrolysis of oil-based drilling cuttings

Homogeneous Organic Crystal Nucleation Rates in Solution from the Perspective of Chemical Reaction Kinetics

It is demonstrated for 11 different combinations of organic solutes and solvents that the supersaturation dependence of homogeneous organic crystal nucleation rates from solution can be predicted from the solubility, bar a single empirical rate constant, when it is assumed that nucleation takes place in reversible aggregates of solvated solutes formed in supersaturated solutions. Reversible solute aggregation represents natural solute density fluctuations that take place in any solute/solvent system. For thermodynamically ideal solutions, the steady state size distribution, and thus the population of reversible aggregates in supersaturated solution, can be predicted quantitatively from the overall solute concentration by a simple mathematical expression. Supersaturation creates an excess of reversible aggregates with sizes exceeding that of the largest aggregate in saturated solution. It is shown that the number of these excess aggregates is proportional to experimental homogeneous nucleation rates, suggesting a rate equation for homogeneous nucleation that has only one empirical parameter, namely, a rate constant specific to the solute/solvent combination. This rate constant can be determined from standard nucleation rate data. The system-specificity of homogeneous nucleation rates thus appears to be encoded solely in a rate constant for the transformation of the large excess aggregates into crystal nuclei. The driving force for triggering nucleation events in these aggregates is likely the extremely high local supersaturation, which provides the conditions for spatiotemporally aligned bond-breaking (e.g., de-solvation) and bond-forming (e.g., solute–solute bonding) events that create stable crystal nuclei. The possible influence of heterogeneous nucleation by solid impurities is considered.

Effects of thermal disposal of oil-water residues on operation heating plant boiler

Industrial zones are often the source of specifically polluted waters, depending on type of industry. These waters are usually not in the limits for outtake into public sewers and it is necessary to dispose them externally or build-up technologies for their pre-treatment. The article is about the real case of an industrial. A separate sewage network is built for oily water. Solid impurities are separated from the oily water and oily water is treated by evaporation technology. The evaporator produces two types of products - condensate and concentrate. Condensate is a water with high organic content, and it is necessary to purified it by a chemical treatment plant in next step. Evaporator technology remove from water the most of metal content and significantly decrease organic and water content in concentrate. Concentrate is oily stream with lower water content. Water content in concentrate decreased in next technology steps to ca. 40-50 %. The final product is certificated technological fuel, and its final elimination is in the heating plant fluidized bed boiler. The article is detailed focused on the influence of concentrate combustion. A local temperature increases around 10-15 °C extending across the combustion chamber was confirmed. There was also an increase in HF concentration in flue gas. CO concentrations were higher in the first moments of combustion, but the control system responded by increasing the combustion air supply, and CO concentrations were finally lower at the level of 3 mg·m-3. During combustion, there was no provable increase in concentrations of NOX or other substances, and the co-combustion did not have a significant effect on the operation of the boiler, so this way was evaluated like technically and economically effective.

Particle distribution and two-phase flow characteristics of twin-screw pump during solid-liquid transfer

The twin-screw pump is a kind of positive displacement machinery with smooth pressure and flow pulsation and strong self-priming ability, which is widely used in the fields of oilfield production, marine engineering, and other fields. However, in the process of conveying liquid-phase media, it is difficult to avoid the inclusion of solid impurities and grit, resulting in wear of the pump casing and rotor, and the pump’s pressurization capacity is reduced or even shut down. At present, the solid-liquid two-phase flow characteristics within the twin-screw pump have not been clarified, which hinders the study of particle wear in the pump. In this paper, a solid-liquid two-phase flow study is carried out on a twin-screw pump through numerical simulation and experimental testing. The distribution of particles with different diameters in the rotor domain with the liquid-phase transport process is explored by simulating the two-phase flow under different differential pressures and particle concentrations. The results show that the particles in the rotor domain are mainly distributed in the region away from the male and female rotor engagement, and the number of particles near the engagement is small but the velocity is higher under the influence of the clearance jets; the elevation of the differential pressure and the particle concentration increase the risk of the particles to collide with the rotor more frequently and at higher velocity; at different particle concentrations, new localized vortices are caused by particle conveying which compared to pure liquid transport, but there are also cases where the original vortices are suppressed. The results will provide a theoretical basis for further research on particle wear characteristics in twin-screw pumps.

Intensifying the particle deposition from a colloidal solution for the purpose of liquid purification: Comparison of deposition mechanisms and rates

The deposition of particles from a layer of colloidal solution (water and microparticles) has been experimentally studied in the presence of laser heating. Instantaneous temperature and velocity fields are measured using a thermal imager and the Particle Image Velocimetry and the Particle Tracking Velocimetry methods. The unstable behavior of the velocity field in the presence of heating and a free liquid surface are assumed to be determined by the Bond number (Bo). Of interest is also an additional mechanism for the instability formation when the Peclet number (Pe) exceeds the critical value and when the ratio of characteristic velocities VT/Vavr > 1, where VT is the heat front velocity at the initial moment of laser heating, and Vavr is the average convection velocity. A new mechanism of particle deposition due to the use of local laser heating is proposed for the first time. The control over local heating and local deposition increases the particle deposition rate by 2–3 orders compared with that without convection. The particle deposition rate and the deposit area increase with increasing height of the liquid layer, reach maximum values at a critical height, and then decrease sharply with increasing height. The dependence for determining the area and mass of the deposit is proposed to take into account the deposition time, the height of the liquid layer and the rate of convection. The resulting particle deposition method and calculation method may be used in technologies related to the purification of liquid from solid impurities in small volumes, as well as in problems where deposition in a given direction is required to form an ordered nanocoating.

Effect of electric field on separation characteristics of oil–water–solid three phases separating device

Lubricating oil can decay as a result of the mixing of water with solid impurities in the working process, and this process can adversely affect the performance of the machinery. Therefore, desolidification and dewatering are key steps in overall oil purification. In general, a basic swirl device cannot sustain efficient dewatering and desolidification. Thus, a three-phase separating device enhanced by an electric field has been proposed. To study the performance of the oil-water-solid separation process, a numerical model of the device was conceived based on combining the governing equations of the flow field and the electric field with the particle-tracking equation giving due consideration to the population balance model. The tangential velocity and the distribution of solid particles at various voltage amplitudes were analyzed, and the effect of the electric field on the oil, water and particle separation process was studied. The results show that at 3 kV, the tangential velocity increased by 5.06%, compared with that at 12 kV. Application of an electric field to the device was found to accelerate more solid particles which assembled near the wall of the device, and where the number of the particles near the axial plane decreased. The maximum particle concentration near the wall at the z = 630 mm plane is 20.24%. Moreover, the average residence time of the solid particles initially exhibited an increasing and then a decreasing trend. Additionally, the increase in the droplet size and enhancement of the oil-water separation process are promoted through the action of the electric field. The rate for desolidification, deoiling and dewatering at 3 kV are 93.60%, 93.30% and 95.59%, respectively.

Valorization of beverage waste as a sugar source for 5-hydroxymethylfurfural production

This study highlights the valorization of beverage waste as a promising sugar-based raw material for 5-hydroxymethylfurfural (5-HMF) production. In this work, both beverage waste purification and 5-HMF production were experimentally demonstrated through the practicality and effectiveness of continuous-flow processes. In the purification process, solid and liquid impurities were wholly eliminated through membrane filtration and a two-stage adsorption process using activated carbon. The purified beverage waste primarily consisted of fructose, glucose, and sucrose, offering a plentiful source of sugar. A mini fixed-bed reactor was employed to thoroughly investigate the impact of various operating variables on continuous 5-HMF production from synthetic beverage waste. The variables considered included residence time, reaction temperature, catalyst type, solvent type, water content, and sugar concentration. The optimization analysis was conducted to achieve both high 5-HMF yield and productivity. The optimal condition, which resulted in the 5-HMF yield of 42.6% and productivity of 3.3e−3 kg5-HMF/kgcat-h, was obtained with a residence time of 15 min, sugar feed concentration of 10 g/L, reaction temperature of 120 °C, and water content of 10 g/L. Dimethyl sulfoxide (DMSO) and Amberlyst 15 were the selected solvent and catalyst, respectively. The feasibility of producing 5-HMF from actual beverage waste was validated under optimal conditions. Furthermore, the stability of the catalyst was demonstrated over 24 h of time-on-stream. The proposed processes offer the potential for continuous purification of beverage waste and the efficient production of 5-HMF.

Superhydrophobic epoxy resin coating with composite nanostructures for metal protection

Superhydrophobic coatings have high application value and wide range of practicality. However, in daily life, problems such as the stability of superhydrophobic coatings are unavoidable, which greatly hinders further developments in the application process. Through this research, we designed a highly stable superhydrophobic coating with a composite structure. That is, by using simple hydrothermal treatment and spraying technology, a superhydrophobic coating with rough structure was obtained by adding 1 H, 1 H, 2 H, 2 H-Perfluorooctyltrichlorosilane modified nano-SiO2 based on epoxy resin solution. Then, by adding stearic acid modified nano-ZnO (S-ZnO) particles, the structure and chemical bonding of the coating were enriched, and a stable superhydrophobic coating with composite nanostructures was prepared. The coating prepared under optimal conditions exhibited superb superhydrophobicity, the obtained water contact angle is 167.2° and the sliding angle is 2.1°. Meanwhile, the coating maintained marvellous superhydrophobicity under external mechanical damage (adhesive tape adhesion and sandpaper abrasion). In addition, the composite coating also exhibited good self-cleaning ability in dealing with solid pollutants and impurity liquids. Therefore, this composite nanostructured epoxy resin superhydrophobic coating can be used to effectively prevent matal corosion, and has the potential for mass production and daily uses.

Carbon dioxide absorption and anti-clogging performance of a novel millimeter-scale channel absorber

This study proposes a novel millimeter-scale channel absorber for the first time, which involves carbon dioxide (CO2) absorption in the channel to achieve efficient CO2 absorption while avoiding clogging. CO2 absorption experiments were conducted on such a channel absorber with an inner diameter of 2.3 mm to study its CO2 mass transfer and absorption characteristics. Al2O3 particles were introduced as solid impurities to evaluate its anti-clogging performance. The experimental results showed that a stable Taylor flow could be formed in the channel in appropriate gas and liquid flowrate ranges. The liquid-side volume mass transfer coefficient (KLa) reached 0.34 s−1 using a 6% DEA solution as the absorbent, which was approximately one order of magnitude higher than that of the conventional packed towers. When Al2O3 to a maximum extent of 2 wt% was added into the absorbents, no clogging was observed, and the values of KLa even increased. Due to the excellent CO2 absorption mass transfer and anti-clogging performance, millimeter channel absorbers have promising industrial applications for CO2 absorption. Therefore, means and application scenario for applying millimeter-scale channel absorber in the industrial CO2 absorption have been proposed.

The velocity field behavior and the nature of deposition of microparticles in a thin layer of colloidal solution at wall heating from one and two laser beams

To date, heat transfer, convection and particle deposition have been mainly investigated for the case of homogeneous wall heating. Convection and particle deposition during local heating, when there are one or more local heating sources, have not been practically studied. Experimental studies of free convection and particle deposition in a layer of colloidal solution have been carried out. Convection was created by heating the liquid using one and two laser beams. The colloidal solution consisted of water and microscopic TiO2 particles. The novelty of the work is the demonstration of the effectiveness of local heating in creating high rates of convection and particle deposition at low energy costs. With two-point laser heating, the convection rate is higher than with single-point heating. When using two laser beams, the Marangoni number increases in comparison with single-point laser heating. As a result, the Bo number becomes lower than the critical value and the stability of the velocity field increases. In contrast to single-point heating, the use of two laser beams does not change the vortex flow pattern with increasing layer height. The particle deposition rate is higher when using a single laser beam than when using two beams and is two orders higher than the deposition without convection. An expression linking the deposition rate with time, layer height and fluid velocity is derived. The obtained results on the use of local heating sources are applicable for enhancing convection, as well as in technologies for cleaning solutions from solid impurities.

Strong Enhancement of Nucleation Efficiency of Aqueous Ethylenediamine Sulfate Solutions by Nonphotochemical Laser-Induced Nucleation: Investigations on the Role of Solid Impurities in the Mechanism

Strong Enhancement of Nucleation Efficiency of Aqueous Ethylenediamine Sulfate Solutions by Nonphotochemical Laser-Induced Nucleation: Investigations on the Role of Solid Impurities in the Mechanism