Sticky Particles Research Articles

Experimental study on the ash deposition and NO emission of high-alkali coal under the staged O2/CO2 and O2/RFG conditions

The oxy-fuel combustion contributes to carbon capture, while the recirculation of flue gas brings about high concentrations of SO2 and H2O, which can affect the transformation of minerals in high-alkali coal. The staged oxy-fuel combustion, as an effective method for NOx reduction, can also change the ash deposition behavior of high-alkali coal. Two kinds of diluting agents, including pure CO2 for O2/CO2 combustion and simulated “recycled flue gas” (CO2, SO2, and H2O) for O2/RFG combustion, were employed in the present work. The ash deposition and NO emission of high-alkali coal during the staged oxy-fuel combustion were simultaneously studied under O2/CO2 and O2/RFG conditions. The conversion ratios of fuel-nitrogen to NO (CNO) and ash deposition efficiencies (Ed) at different stoichiometric ratios in primary combustion zone (SR1) and different oxygen concentrations were obtained. Afterwards, a series of tests were performed to further analyze the ash deposits. The experimental results show that as SR1 increases from 0.6 to 1.2, CNO jumps from 2.0 % to 23.5 % (O2/CO2 combustion) and from 1.9 % to 19.9 % (O2/RFG combustion). The additions of SO2 and H2O can reduce the NO emission. With the rising SR1, Ed under the O2/CO2 and O2/RFG conditions decreases from 4.0 % to 2.6 % and from 4.8 % to 2.1 %, respectively. At high SR1, the CaSO4 amount declines and the iron contributes less to the ash deposition. In O2/RFG combustion, the small sticky particles of sodium aluminosilicates on large particle surfaces reduce, and the large particles of calcium aluminosilicates shrink because some calcium produces CaSO4. Moreover, the exposure of ferrous iron to H2O helps its oxidization so iron is harder to cause severe adhesion. As O2 concentration rises from 21 % to 40 %, CNO shows an upward trend. Meanwhile, Ed under the O2/CO2 and O2/RFG conditions increases from 2.6 % to 3.7 % and from 2.3 % to 2.7 %, respectively. The present work is expected to provide some conducive information for the clean utilization of high-alkali coal and secure operation of boiler, as well as large-scale CO2 capture.

Discrete element contact model and parameter calibration of sticky particles and agglomerates

The soil in southwest China is a cohesive soil in which discrete cohesive particles and aggregates coexist. In view of the problem that there are many studies on discrete cohesive particles and a lack of research on aggregates, discrete element software DEM is used to conduct a study on cohesive particles and agglomerates parameter calibration. The angle of repose is selected as the target value to calibrate the simulation parameters of sticky particles. Then, the simulation parameters of the viscous particles are used as the basis for the calibration of the contact parameters of the agglomerates, and shear experiments are conducted on the agglomerates, with the ultimate shear depth and ultimate shear force as target values. The results show that the parameters of the agglomerate are: Normal Stiffness per unit area is 5.627 × 108 N/m3, Shear Stiffness per unit area is 4.359 × 108 N/m3, Critical Normal Stress is 3.5 × 106 Pa, Critical Shear Stress is 4.5 × 106 Pa and Bonded Disk Radius is 5.43 mm. Through the particle sliding friction angle test and the agglomerate compression test, it was verified that the errors of sticky particles were 0.30 % and 0.37 % respectively, and the error of agglomerates was 1.69 %.

Asymptotics of the sticky particles evolution

We study the long-time asymptotic behavior of the Sticky Particles dynamics on the real line. The time average of the Sticky Particles Lagrangian map has a limit which arises as a general property of projections onto closed convex cones in Hilbert spaces. More notably, we prove that the map itself has an asymptotic limit in the case where the sticky particles dynamics is confined to a compact set.

Escape from textured adsorbing surfaces.

The escape dynamics of sticky particles from textured surfaces is poorly understood despite importance to various scientific and technological domains. In this work, we address this challenge by investigating the escape time of adsorbates from prevalent surface topographies, including holes/pits, pillars, and grooves. Analytical expressions for the probability density function and the mean of the escape time are derived. A particularly interesting scenario is that of very deep and narrow confining spaces within the surface. In this case, the joint effect of the entrapment and stickiness prolongs the escape time, resulting in an effective desorption rate that is dramatically lower than that of the untextured surface. This rate is shown to abide a universal scaling law, which couples the equilibrium constants of adsorption with the relevant confining length scales. While our results are analytical and exact, we also present an approximation for deep and narrow cavities based on an effective description of one-dimensional diffusion that is punctuated by motionless adsorption events. This simple and physically motivated approximation provides high-accuracy predictions within its range of validity and works relatively well even for cavities of intermediate depth. All theoretical results are corroborated with extensive Monte Carlo simulations.

Determination of the Mass Fractions of the Heavy Metals in the Recycled Cellulose Pulp.

In the process of paper recycling, certain amounts of metals can be found in the cellulose suspension, the source of which is mainly printing inks. The paper industry often uses different technologies to reduce heavy metal emissions. The recycling of laminated packaging contributes to the formation of sticky particles, which affects the concentration of heavy metals. This study aimed to determine the mass fraction of metals in the different phases of the deinking process to optimize the cellulose pulp's quality and design healthy correct packaging products. In this research, the deinking flotation of laminated and non-laminated samples was carried out by the Ingede 11 method. As a result of the study, the mass fractions of metals in cellulose pulp were divided into four groups according to the mass fraction's increasing value and the metals' increasing electronegativity. The quantities of metals were analyzed using Inductively Coupled Mass Spectrometry (ICP-MS). The separation of metals from cellulose pulp is influenced by the presence of adhesives and the electronegativity of the metal. The results of the study show that the recycling process removes certain heavy metals very well, which indicates the good recycling potential of pharmaceutical cardboard samples.

Effects of SO2 and H2O on the ash deposition and NO emission during oxy-fuel combustion of high-alkali coal

The oxy-fuel combustion is promising to realize the large-scale CO2 capture and effective reduction of nitric oxides. The recirculation of flue gas in oxy-fuel combustion can lead to high concentrations of SO2 and H2O, which probably affects the ash deposition of high-alkali coal because SO2 and H2O are important for the transformation of alkali and alkaline earth metals (AAEMs). In the present work, the effects of SO2 and H2O in recycled flue gas on the ash deposition and NO emission during the oxy-fuel combustion of high-alkali coal were experimentally evaluated in a vertical two-stage furnace system. The conversion ratio of fuel-nitrogen to NO (CNO) and ash deposition efficiency were measured, and then the ash deposits were subjected to a couple of tests for further analyses. The experimental results show that SO2 helps to reduce the NO emission and its impact on ash deposition depends heavily on its concentration. In the case with modest SO2 addition, the sulfations of sodium and calcium are enhanced to some extent. Consequently, the amount of small sticky particles (NaCl and sodium aluminosilicates) that attached to large particles decreases, and the large particles mainly made of calcium aluminosilicates become smaller and less sticky. The newly generated Na2SO4 and CaSO4 are insufficient to overcome the inhibiting effects, thus the ash deposition efficiency decreases. Under the condition of excessive SO2 addition, the sulfations are further promoted. The small particles rich in Na2SO4 and CaSO4 are substantially more, which can not only serve as the initial ash layer on the heating surface, but also strengthen the stickiness of large particles by attaching to their surfaces. Therefore, the ash deposition efficiency increases·H2O can reduce the NO emission, while it aggravates the ash deposition because H2O enhances the sulfation.

Theoretical study of kinetic arrest, shear elastic modulus, and yielding in simple biphasic colloidal mixtures.

Based on integrating microscopic statistical mechanical theories for structure and ideal kinetic arrest at the naive mode coupling level, we study dynamic localization, the linear elastic shear modulus, applied stress induced modulus softening, and the absolute yielding of simple biphasic binary mixtures composed of equal diameter hard and attractive spheres. The kinetic arrest map is a rich function of total packing fraction, strength of attraction, and mixture composition. The gel to attractive ideal glass transition, the degree of glass melting re-entrancy, and the crossover boundary separating repulsive glasses from attractive glasses vary with the mixture composition. Exponential and/or apparent (high) power law dependences of the elastic shear modulus on the total packing fraction are predicted with effective exponents or exponential prefactors that are sensitive to mixture composition and location in the kinetic arrest map. An analysis of the effective mean square force on a tagged particle that induces dynamic localization reveals a compensation effect between structural correlations and degree of particle localization, resulting in the emergence of a weaker dependence of the shear modulus on mixture composition at very high attraction strengths. Based on a microrheologically inspired formulation of how external stress weakens particle localization and the shear modulus, we analyze mechanical-induced modulus softening and absolute yielding, defined as a discontinuous solid-to-fluid stress-induced transition that can occur in either one or two steps. Estimates of the corresponding yield strains predict that the binary mixture becomes more brittle with increasing sticky particle composition and/or attraction strength.

Probability measures on path space for rectilinear damped pressureless Euler-Poisson equations

We show global existence of a measure-valued solution to the Cauchy problem for the rectilinear Euler-Poisson equations, which govern flow of pressureless dust experiencing linear damping in the gravitational field generated by its own mass, and a given background charge field modeling exterior gravitational force. The velocity of the dust is a Borel measurable function, and the distribution of mass is given by time-dependent probability measures on the real line. Upon adapting the method established in Hynd (2020) [25], we obtain the solution by construction of a probability measure on the path space, through approximation of finite sticky particles.

Investigation on combustion characteristics and ash-related issues of Calliandra calothyrsus and Gliricidia sepium using thermogravimetric analysis and drop tube furnace

Calliandra calothyrsus and Gliricidia sepium are developed as wood energy forest plantations in degraded land. They have good survivability, are fast to be harvested, and have good calorific value to be utilized as biomass fuel. This study aims to investigate their combustion characteristics by thermogravimetric analysis and their ash-related issues by combustion experiments in drop tube furnace and ash observation. The results show that G. sepium has a better combustion performance with higher values of ignition index, comprehensive combustion index, and flammability index, while C. calothyrsus shows better ash-related issues with less risk in theoretical slagging prediction, clearer metal surface in the fouling area, and less ash deposit formation. The domination of K, Ca, and S elements in the ash deposits of both biomasses results in several sticky aggregate particles and low-melting minerals. This study provides an in-depth understanding of C. calothyrsus and G. sepium combustion for broader utilization.

Dynamic compaction of cohesive granular materials: scaling behavior and bonding structures.

The compaction of cohesive granular materials is a common operation in powder-based manufacture of many products. However, the influence of particle-scale parameters such as bond strength on the packing structure and the general scaling of the compaction process are still poorly understood. We use particle dynamics simulations to analyze jammed configurations obtained by dynamic compaction of sticky particles under a fixed compressive pressure for a broad range of system parameter values. We show that relative porosity, representing the relative importance of porosity with respect to its minimum and maximum values, is a unique function of a modified cohesion number that combines adhesion force, confining pressure, and particle size, as well as contact stiffness, which is often assumed to be ineffective but is shown here to play an essential role in compaction. An asymmetric sigmoidal form based on two power laws provides an excellent fit to the data. The statistical properties of the bond network reveal self-balanced force structures and an exponential fall-off of the number of both tensile and compressive forces. Remarkably, the properties of the bond network depend on the cohesion number rather than the modified cohesion number, implying that similar bond network characteristics are compatible with a broad range of porosities mainly due to the effect of contact stiffness. We also discuss the origins of data points escaping the general scaling of porosity and show that they reflect either finite system size or rigid confining walls.

Study on the interaction between inherent minerals of coal with refuse derived fuel (RDF) during co-firing

In this paper, refuse derived fuel (RDF) and bituminous coal were co-fired to investigate the particulate matter (PM) yields and the interaction between the inherit minerals in a lab-scale drop tube furnace (DTF). The PM1-10 yields during the co-firing of coal and RDF dramatically decreased by 16.29 %∼28.5 % of the combustion of coal alone. In addition, methane auxiliary combustion inhibited the PM1 yields by 7.95 % at air atmosphere. The Si-rich minerals in coal interreacted with the organic alkali (earth) metals in RDF, massively generating sticky particles with high liquid amount of K-Al-Si and Ca-Al-Si, promoting the transformation of fine grains into coarser mode. Moreover, it was proved that both methane auxiliary combustion and co-firing can reduce the emission of fine particles. The additional heat accelerated the burn of the char at the early stage of combustion, providing adequate time for the interaction between the inorganic species. Through thermodynamic equilibrium calculations of 1500 ∼ 3000 fly ash grains, it was found that co-firing increased the formation of sticky particles by 64.8 %∼70.3 %, resulting in a significant enhancement in capturing fine particles and Na, K vapor. Therefore, the co-firing of coal with RDF offers a promising approach to realize the harmless and resourceful treatment of municipal solid waste (MSW), and inhibit land resource losses caused by landfill

The Influence of the Production Stages of Cardboard Pharmaceutical Packaging on the Circular Economy

Packaging appearance is important in a competitive market. Designers strive to create products that attract customers and often use laminated packaging, due to the attractive appearance and quality characteristics of the material. The circular economy in the recycling of cardboard packaging helps to reduce waste, saves natural resources and increases the quality of the environment. All of the above contributes to sustainable production, but the quality and properties of the obtained recycled paper materials should not be ignored. Recycling of laminated cardboard packaging often has a negative impact on the quality of recycled paper, due to the formation of sticky particles that can affect the optical properties of recycled paper and the efficiency of the recycling process. This article provides insight into the influence of each stage of production of packaging intended for pharmaceutical products on the properties and characteristics of recycled paper. The standard INGEDE 11 deinking method was used to remove dyes and other impurities from the pulp. The obtained optical results of the characteristics of recycled laboratory sheets obtained from laminated and non-laminated cardboard samples were compared in order to determine the impact of each stage of box production on the quality of the paper pulp. The acquired knowledge can be applied in the design phase of a more sustainable product, and laminated materials can be used in luxury products or to increase the functionality of the packaging. Designing for recycling will contribute to an increase in the quality of the obtained paper mass, which is directly related to an increase in the productivity of recycling and the sustainability of the packaging production process.

Escape of a sticky particle

Escape of a sticky particle

Study on the mechanical properties of embankment soil under long-term immersion conditions

During flood season, embankments are often submerged in high water levels for extended periods, leading to deterioration in their soil mechanics performance and increasing the risk of slope instability and other hazards. In order to investigate the changes in mechanical properties of embankment slopes during long-term water immersion, direct shear tests were conducted. Scanning electron microscopy, chemical composition analysis, and laser particle size analysis were conducted on samples taken at different immersion periods. Clay samples were taken from the embankments at Jiangxinzhou in Nanjing, Jiangsu Province, China. Results showed the shear strength of the soil gradually decreases with the increase of immersion time, while the cohesive force and internal friction angle gradually decrease as well. This suggests that immersion has a softening effect on the shear strength of the soil. As the immersion time increases, the colloidal particles (soluble salt) rapidly dissolves, the microstructure of the soil is destroyed, and sticky particles increases, resulting in a change in the shear strength of the soil. The research results provide a basis for flood control and prevention of embankments immersed in high water levels for long periods during the flood season.

On the sticky particle solutions to the multi-dimensional pressureless Euler equations

In this paper we consider the multi-dimensional pressureless Euler system and we tackle the problem of existence and uniqueness of sticky particle solutions for general measure-type initial data. Although explicit counterexamples to both existence and uniqueness are known since [6], the problem of whether one can still find sticky particle solutions for a large set of data and of how one can select them was up to our knowledge still completely open.In this paper we prove that for a comeager set of initial data in the weak topology the pressureless Euler system admits a unique sticky particle solution given by a free flow where trajectories are disjoint straight lines.Indeed, such an existence and uniqueness result holds for a broader class of solutions decreasing their kinetic energy, which we call dissipative solutions, and which turns out to be the compact weak closure of the classical sticky particle solutions. Therefore any scheme for which the energy is l.s.c. and is dissipated will converge, for a comeager set of data, to our solution, i.e. the free flow.

On conservative sticky peakons to the modified Camassa-Holm equation

We use a sticky particle method to show global existence of (energy) conservative sticky N-peakon solutions to the modified Camassa-Holm equation. A dispersion regularization is provided as a selection principle for the uniqueness of conservative N-peakon solutions. The dispersion limit avoids the collision between peakons, and numerical results show that the dispersion limit is exactly the sticky peakons. At last, when the splitting of peakons is allowed, we give an example to show the non-uniqueness of conservative solutions.

Effect of External Moisture Content on Screening Performance of Vibrating Flip-Flow Screen and Circular Vibrating Screen

Moisture content has an important influence on the stratification and screening of materials on the surface of screens, and materials with different external moisture concentrations present different screening characteristics. A vibrating flip-flow screen (VFFS) is a two-body vibration system with a high-vibrating-strength screen surface developed based on a circular vibrating screen (CVS), which offers significant advantages in terms of handling sticky fine particles. To better understand the difference in screening performance between a VFFS and CVS under different external moisture concentrations, it is necessary to conduct a comparative study on the distribution characteristics of materials on the screen’s surface. In this paper, a CVS dynamic model considering the stiffness force and position of the damping spring is proposed, and the influence of different arrangements of damping springs on the amplitude and angular displacement of the screen is analyzed. Under different external moisture concentrations, the screening percentages of the 3–1 mm sized fractions in sections I–IV of a VFFS and a CVS are greater than those of 1–0 mm sized fractions. The screening efficiencies of CVSs and VFFSs are 92.54% and 92.19%, respectively, at an external moisture content of 4.30%, so the screening effect of a low-vibration-intensity screen surface is better in the case of better material stratification. When the external moisture content of the material was increased from 4.30% to 8.19%, the screening efficiency of the VFFS and the CVS decreased by 33.85% and 41.32%, respectively. The screening efficiency of the CVS is more sensitive to the external moisture content of a material.

Sticky particle Cucker–Smale dynamics and the entropic selection principle for the 1D Euler-alignment system

We develop a global wellposedness theory for weak solutions to the 1D Euler-alignment system with measure-valued density, bounded velocity, and locally integrable communication protocol. A satisfactory understanding of the low-regularity theory is an issue of pressing interest, as smooth solutions may lose regularity in finite time. However, no such theory currently exists except for a very special class of alignment interactions. We show that the dynamics of the 1D Euler-alignment system can be effectively described by a nonlocal scalar balance law, the entropy conditions of which serves as an entropic selection principle that determines a unique weak solution of the Euler-alignment system. Moreover, the distinguished weak solution of the system can be approximated by the sticky particle Cucker–Smale dynamics. Our approach is inspired by the work of Brenier and Grenier on the pressureless Euler equations.

Second Order Two-Species Systems with Nonlocal Interactions: Existence and Large Damping Limits

We study the mathematical theory of second order systems with two species, arising in the dynamics of interacting particles subject to linear damping, to nonlocal forces and to external ones, and resulting into a nonlocal version of the compressible Euler system with linear damping. Our results are limited to the 1 space dimensional case but allow for initial data taken in a Wasserstein space of probability measures. We first consider the case of smooth nonlocal interaction potentials, not subject to any symmetry condition, and prove existence and uniqueness. The concept of solutions relies on a stickiness condition in case of collisions, in the spirit of previous works in the literature. The result uses concepts from classical Hilbert space theory of gradient flows (cf. Brezis, Operateurs maximaux monotones et semi-groupes de contractions dans les espaces de Hilbert, 1973) and a trick used in Brenier et al. (J. Math. Pures Appl. 99(5):577–617, 2013). We then consider a large-time and large-damping scaled version of our system and prove convergence to solutions to the corresponding first order system. Finally, we consider the case of Newtonian potentials - subject to symmetry of the cross-interaction potentials - and external convex potentials. After showing existence in the sticky particles framework in the spirit of Brenier et al. (J. Math. Pures Appl. 99(5):577–617, 2013), we prove convergence for large times towards Dirac delta solutions for the two densities. All the results share a common technical framework in that solutions are considered in a Lagrangian framework, which allows to estimate the behavior of solutions via L^{2} estimates of the pseudo-inverse variables corresponding to the two densities. In particular, due to this technique, the large-damping result holds under a rather weak condition on the initial data, which does not require well-prepared initial velocities. We complement the results with numerical simulations.

Effects of the addition of RPF and woody biomass on PM emissions during co-firing with coal

Two Cl-free refuse plastic and paper fuels (RPFs) produced by hydrothermal treatment with Ca(OH)2, as well as two biomasses, were co-fired with bituminous coal in a lab-scale drop tube furnace (DTF). The results indicate that the addition of biomass and RPF partially reduced the emission of SO2, which can readily cause corrosion, deposition and pollution. For the biomass co-firing, the particulate matter (PM) emissions from the black pellet (BP) series were 5.0% higher than those from the white pellet (WP) series because more sticky particles were formed with the increment of Ca-Al-Si and K-Al-Si, which absorbed alkali vapor and fine grains in the gas bulk to inhibit the PM emissions. For RPF, the major origins of sticky particles turned into Ca-Al-Si and Ca-K-Al-Si, the proportion of which was dramatically higher than that from the biomass, resulting in a stiffer suppression of PM formation. In general, the promotion of Ca from additives conversely restrained its transformation into PMs during both biomass and RPF co-firing. It can be concluded that the co-firing of RPF with bituminous coal provides an alternative approach to simultaneously control the emissions of greenhouse gases, gaseous pollutants and PM while remediating plastic waste.