Spray Granulation Process Research Articles

Preparation of quaternary spherical TiO2-B4C-C-Cu composite powder for laser cladding

Powder preparation is the key step in producing laser cladding coatings with desired properties. In this paper, quaternary TiO2-B4C-C-Cu composite powder with high sphericity and good densification has been successfully prepared by a powder fabrication process combining spray granulation with densification sintering. The effects of slurry characteristics, spray granulation process parameters, and densification sintering temperature on particle morphology and performance were studied. The formation mechanism of quaternary spherical TiO2-B4C-C-Cu composite powder was revealed by analyzing the process of heat transfer and water transfer in the droplets, and the optimization direction of the powder preparation was indicated. The optimized process parameters for the quaternary spherical TiO2-B4C-C-Cu composite powder are: slurry solid content of 52 wt%, dispersant content of 1.25 wt%, binder content of 2 wt%, inlet temperature of 180 °C, the airflow rate of 310 L/h, slurry feed rate of 4.5 ml/min, and the two-stage temperatures of densification sintering are 500 ℃ and 900 ℃ for 1 h, in turn. Under the optimized process, the fluidity of the powder reaches 112 s/50 g, the apparent density reaches 1.2 g/ml, and more than 70% of the particles are between 15–53 µm. The powder has been verified by laser cladding to prepare in-situ synthesized TiB2-TiC-Cu composite coatings, which could have a better prospect for potential application.

The effect of Al/oxidizers interfacial structure on the mechanical properties of composite propellants

In this paper, the mechanical properties of a typical four-component composite solid propellants with various designed Al/oxidizer interfaces have been studied. The Al/oxidizer interfacial control is mainly realized by using the core-shell composites AP@Al and Al@RDX with different particle sizes, where Al powder was coated with a thin layer of polydopamine (PDA) as the binding sites, so that the oxidizers could crystalize on it during a rapid spray granulation process. The stress-strain curves of the above propellants at different temperatures and different tensile rates have been obtained. The dependence of the loss factor on temperature was studied by using a dynamic thermomechanical analysis (DMA). It has been shown that the fracture elongation of the interfacial modified propellants can reach 51.81% at room temperature, which is 127.3% higher than that of the blank formulation under the same formulation. Moreover, the temperature and strain rate sensitivity of interfacial controlled HTPB propellants is much less than that of traditional ones. The microstructure of these propellants at the crack sites was investigated by scanning electron microscopy (SEM) supported with micro-area in-situ tensile CT scanning technology, to clarify their damage and failure mechanisms.

High efficiency CO2 sorption property of Li4SiO4 sorbent pebbles via a simple rolling ball method

At present, the Li4SiO4 sorbents have been getting widespread attention for mitigating the release of CO2 gas owing to its stable cyclic property, higher capturing ability, and lower regeneration temperatures. In this work, a facile rolling ball method is first proposed to fabricate Li4SiO4 sorbent pebbles, which overcomes the low production efficiency, poor adsorption stability, and high production cost adopted in the previous literature. In the rolling ball process, the spray granulation process was involved to decrease the specific surface area of ceramic powder, which makes it easier for powder self-agglomerate to form pebbles via the centrifugal force with the assistance of PVA polymer solution. Moreover, the phase composition, the specific surface area, the shaping principle, and the microstructure of Li4SiO4 sorbent pebbles were studied, respectively. The result shows that the Li4SiO4 pebbles sintered at 900 °C for 2 h present a superior comprehensive performance with a homogeneous diameter of 1.2 mm, good sphericity of 0.95, high crushing load of 65 N, and suitable porosity of 6.28 %. Compared with Li4SiO4 powder, the spherical pebbles performed superior CO2 adsorption ability (0.304 g CO2/g sorbent) and excellent cyclic stability in a 100% CO2 environment owing to its large number of uniform pores channels produced by binder solution at high temperature. Therefore, the rolling ball process is a potential method for the batch production of Li4SiO4 pebbles to capture CO2 stably in the future.

Parallel compensator for zero dynamics stabilization in fluidized bed spray granulation

This contribution is concerned with the stabilization of continuous fluidized bed spray granulation processes with external sieve mill cycle. To keep the overall mass of particles inside the granulation chamber in well-defined bounds these processes are in general operated with a mass controller. This configuration is well-known to become unstable for certain ranges of the milling diameter. Here, the instability results in a nonlinear limit cycle of the particle size distribution. As has been shown in a previous contribution the stability problem is not inherent to the process, which is open-loop stable over a wide range of operating conditions. In fact, the root cause for the instability is the mass controller, which interacts with the unstable zero dynamics of the granulation process. To overcome this problem a parallel compensator will be designed, which allows to stabilize the process zero dynamics and thus solves the problem of control induced instabilities.

Microstructure, phase constitution and mechanical properties of WC-Cr3C2-CoNiLa coatings fabricated by using HVOF spraying core-shell powder

To reduce the decarburization of WC, the core-shell WC-16Cr3C2-10Co4Ni-La2O3 (named as WC-Cr3C2-CoNiLa in following) powder was prepared through second agglomeration and spray granulation process and deposited using high velocity oxygen fuel (HVOF) spraying. Microstructure and phase constitutions of the deposited coating were characterized using scanning electronic microscopy (SEM) with energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. Microhardness, elastic modulus, and fracture toughness of the coating were tested by indentation method. Wear properties of the coating under different applied loads were evaluated by two body dry sliding wear using a pin-on-disc tester. Experimental results showed that the HVOF sprayed WC-Cr3C2-CoNiLa coating was mainly consisted of WC, Cr3C2, Co, Ni phases and a little of Cr2O3 without any WC decarburized phases including W2C, M6C and M12C). Most of WC carbide in the coating presented a round outline with the average particle size of 0.54 ± 0.35 μm and average crystal sizes 401 ± 91.41 Å in different crystal orientation index. The coating presented dense microstructure with the porosity about 1.16 ± 0.39%, and some lamella features with well bonded interfaces of carbide particles/binder phase, inter-splats and coating/substrate. Microhardness, elastic modulus, fracture toughness and wear rate of the coatings were 12.57 ± 0.52 Hv0.3, 153.91 ± 31.66 GPa, 5.31 ± 0.51 MPa⋅m1/2 and 6.67*10−3-11.11*10−3 mg/(Nm) when the applied load increased form 5 N to 15 N, respectively. The abrasive wear of the coating occurred mainly in the form of gouging and plastic deformation as well as peeling off carbide particles.

Gender-Based Eye Movement Differences in the Ilab-X Platform Using: An Eye-Tracking Study

Continuous fluidized bed spray granulation processes are known to be prone to non-linear oscillations, which requires a stabilizing controller design. In this article, a purely data-driven Koopman-based system linearization and control is proposed, which does not need any prior model knowledge and uses only systems input-output measurements. The linearization achieved by the Koopman embedding allows for linear-quadratic control design, which does not depend on the operating point. The proposed method was validated in a simulation study of a fluidized bed granulation process and was able to stabilize the particle size distribution in different operating points.

Koopman-based data-driven control for continuous fluidized bed spray granulation with screen-mill-cycle

Continuous fluidized bed spray granulation processes with external screen-mill cycle are known to be susceptible to nonlinear oscillations. As has been shown recently, mass control may induce periodical oscillation of the particle size distribution in fine grinding regimes, which requires the design of additional stabilizing control. In this contribution a data-driven control approach is investigated. It is based on the identification of the Koopman-based linear representation of the system and does not require any manual system modeling as it is based purely on input–output measurements. The resulting representation makes possible a linear–quadratic control design, that does not depend on a specific operational point. The proposed approach was successfully validated in a numerical study.

Koopman-based data-driven control for continuous fluidized bed spray granulation

Abstract Continuous fluidized bed spray granulation processes are known to be prone to non-linear oscillations, which requires a stabilizing controller design. In this article, a purely data-driven Koopman-based system linearization and control is proposed, which does not need any prior model knowledge and uses only systems input-output measurements. The linearization achieved by the Koopman embedding allows for linear-quadratic control design, which does not depend on the operating point. The proposed method was validated in a simulation study of a fluidized bed granulation process and was able to stabilize the particle size distribution in different operating points.

Novel dry-suspension granulation process for preparing pressed powders of ceramic tiles

Herein, we propose a novel dry-suspension granulation process and compare it with the conventional spray granulation process used in the ceramic industry. The proposed granulation process, which is based on dry grinding, uses airflow as the driving force and raw material particles combined with atomized water, bonded together within a humidifying chamber. Then, this mixture is reformed and separated inside a cyclone to prepare the pressed powders. The results showed the novel process can effectively prepare powders, with less energy and water required than that by the wet granulation process. Under the current working conditions, the receiving rate was 87%, the water content of the product was 5.8%, and 63% of the particles were bigger than 0.2 mm. Both the fluidity and compressibility were able to meet the basic requirements for pressed powders in industrial production. Therefore, this proposed process can be expected to be widely used in ceramic tile production in the future.

Control induced instabilities in fluidized bed spray granulation

This contribution is concerned with the stability problems occurring during the operation of continuous fluidized bed spray granulation processes with external sieve mill cycle. These processes are in general operated by a mass controller, which guarantees that the overall mass of particles in the granulation chamber stays in well-defined bounds. It is well-known that, depending on the milling diameter, instabilities may occur, which result in a nonlinear limit cycle of the particle size distribution. To overcome this problem two approaches have been proposed in the literature, constrain the admissible parameter space to exclude regions of instability and design additional stabilizing control loops. In the present contribution, the cause of this instability phenomenon will be studied. It will be shown that the instability is not inherent to the process, which turns out to be open-loop stable over the studied parameter range, but due to the mass controller. More specifically, it will be demonstrated that the zero dynamics of the granulation process become unstable for certain parameter ranges resulting in closed-loop unstable process behavior. To point out, that this behavior does not depend on the specific mass controller design procedure, three prototypical mass controllers of practical relevance are designed and analyzed.

PARTEC 2019 – Overcome the Challenges in Particle and Powder Technology

AbstractNo abstract.

A facile route for producing spherical granules comprising water reactive aluminium nitride added composite powders

In this contribution, a simple and cost-effective spray-granulation process has been developed for producing spherical, ready-to-press (RTP) granules comprising highly water reactive powder like aluminium nitride along with other powders such as silicon nitride, aluminium oxide and yttrium oxide for producing SiAlON product. The novelty of this process stands on the instantaneous drying of granules at ambient temperature without the requirement of additional drying set-up. The salient properties of granules such as apparent density, tap density, Carr index, and Hausner ratio were evaluated. The Hall flow measurement shows good gravimetric flow of granules. The resultant granules which were used for producing complex shaped product with the help of cold isostatic pressing, showed good compaction behaviour as it is evident from green density of the product (≈ 55–59% of theoretical density) and from good compaction ratio (2.7:1). The X-ray diffraction pattern confirms that crystalline phase of sintered sample corresponds to β-SiAlON.

Self-lubrication and wear-resistance mechanism of graphene-modified coatings

To reduce the friction coefficient of WC-17Co wear-resistant coatings, Graphene oxide were used to mix with WC-17Co powder. The SEM, EDS and Raman results were used to analyze the morphology and phase composition of graphene oxide in the powder and coating obtained by plasma spraying processes. The mechanical properties of the coatings were studied by using a microhardness tester and a universal testing machine. The friction and wear properties of the coatings were studied by using a UMT-2 friction and wear tester. The results show that among the pulverization processes, the spray granulation process can achieve a stronger and more uniform adhesion of graphene oxide on the surface of WC-17Co particles, and the graphene oxide content in the coating is higher. Graphene is still embedded in the coating as transparent, thin sheets. The bonding strength is approximately 63 MPa, the hardness is approximately 931 HV0.1, and the friction coefficient of the graphene oxide coating is reduced by approximately 22% compared to that of the coating without graphene. The formation of lubrication films in the micro-area improves the self-lubrication and antiwear effects.

Discontinuous Galerkin solution of the convection-diffusion-reaction equations in fluidized beds

In this work, the Discontinuous Galerkin (DG) schemes were studied for the solution of convection-diffusion-reaction equations which arise from mathematical modeling of fluidized bed spray granulation process (FBSG). The discontinuous Galerkin method for space discretization is employed to treat the dominated convection behavior in the governing equations. The implicit Euler method for the temporal discretization is used. The mathematical analysis of the governing equations with a priori bounds for all the state variables is demonstrated. The investigation of experimental order of convergence is presented for test functions of degrees one and two. Finally, parallel efficiency of strong scaling is presented for the employed DG schemes.

Properties of GO/WC–Co coatings prepared via different pulverisation processes

ABSTRACTGraphene-modified WC–Co self-lubricating (GO/WC–Co) coatings were prepared via different powder production processes. Compared with the wet ball milling, wet mixing, and sintering and crushing processes, the spray granulation process produces uniform and tight adhesion of the graphene on the surface of the WC–Co powder. The bonding strength and hardness of the resultant coating are approximately 70 MPa and 1000 HV0.3, respectively. Graphene modification causes a 40% reduction in the friction coefficient. During the friction process, the graphene constantly forms a lubricating film that serves as an excellent self-lubricating layer.

Control of Multi-Chamber Continuous Fluidized Bed Spray Granulation

Abstract This paper is concerned with control of multi-chamber continuous fluidized bed spray granulation processes with external sieve-mill cycles. The process is described by a population balance equation for the particle size distribution in each chamber, resulting in a system of nonlinear partial integro-differential equations. Therefore, control design is challenging. In order to overcome these difficulties the control problem is formulated using a generalized distance measure, the discrepancy. It is shown that discrepancy based control allows to design a simple and effective nonlinear control law for multi-chamber continuous fluidized bed spray granulation processes with external sieve-mill cycles.

Non-identifier-based adaptive control of continuous fluidized bed spray granulation

This paper is concerned with stabilizing control for continuously operated fluidized bed spray granulation with internal product classification. It is well-known that these processes may become unstable for certain operating conditions giving rise to nonlinear oscillations in the particle size distribution. In contrast to previous works, in this contribution a model-free adaptive control is proposed. It is shown that the given fluidized bed spray granulation process fulfills the required structural assumptions. The designed control schemes, universal adaptive and λ-tracking control, are tested in a noise-free scenario and including measurement noise.

Influence of process conditions on the product properties in a continuous fluidized bed spray granulation process

This work focuses on continuously operated spray granulation processes in horizontal fluidized beds highlighting the influence of process conditions on the particle properties of the resulting product granules. The drying process has a decisive influence on the kinetics of the growth rate and thus also on the properties of the particles, such as the morphological structure, particle moisture content and porosity as well as density, compression strength and the wetting behavior. This influence has been considered in this study in more detail on the basis of the model material sodium benzoate. In order to compare the produced granules at different drying conditions and spray rates of the suspension an external product classification was used to achieve a certain product granule size. The obtained experimental results show a deep influence of the thermal conditions onto granule morphology and structural properties, which is in qualitative agreement with recent experimental observations (Rieck et al., 2015; Hoffmann et al., 2015a; Schmidt et al., 2017b). The overall trend of the results reveal smoother product granules with decreasing spray rates of the suspension and increasing drying temperatures. These smoother surface morphologies lead to a more homogeneous layering which has as a consequence that the internal particle porosity is decreasing while the solids density and the compression strength of the particles are increasing at the same time. In this study the purely qualitative classification of the surface texture from previous experimental studies was extended by the topographic analysis of the product granules, giving the possibility to quantify the morphological structure by means of roughness measurements. This makes the morphological design accessible as product property and permits the utilization of models that describe the morphology according to the process conditions.

Use of Spouted‐Bed Spray Granulation Process for Fabrication of Metal/Ceramic‐Polymer Composites

Use of Spouted‐Bed Spray Granulation Process for Fabrication of Metal/Ceramic‐Polymer Composites

CFD-PBE simulation to predict particle growth in a fluidized bed melt granulation batch process

The fluidized bed spray granulation process unites the steps of solid formation and product formulation in one apparatus and is used to produce granulate products out of a liquid. According to different applications of granules, a specific product particle size distribution is required. Thus, the ability to predict the development of the particle size distribution is crucial for process design, optimization and scale-up. For this reason, population balance equations can be solved where the knowledge of particle size-dependent growth rates are the important quantities, which are difficult to obtain by experiments.Using a computational fluid dynamics multiphase model with one nozzle at its center, an advanced two-fluid model with five fluid phases is solved for short process times (~s) considering a high local and temporal resolution of the granulation process (including fluid dynamics, drop deposition and energy equations) to evaluate size-dependent growth rates, as a function of the current state of the process. By transferring particle growth rates to population balance equations, the development of particle size distribution can be finally predicted for long process times (~min).The present work applies the predictive model to an industrial melt spray granulation process in batch mode. Experimental data show that this model could be implemented successfully.