Hopper Wall Research Articles

Research on ash accumulation surface measurement methods based on the dot laser principle

Dust collectors are essential environmental protection equipment in thermal power plants. However, in recent years, collapses caused by excessively high material levels in the ash hopper in dust collectors have increased frequently, resulting in serious casualties and significant economic losses. The level gauge of the ash hopper is a crucial device for detecting the material level in the ash hopper and plays a vital role in preventing the ash hopper from collapsing due to excessive material load. However, level gauges of the ash hopper currently in use have various problems. Laser-ranging technology is characterized by concentrated energy, a small divergence angle, and the ability to penetrate dust. We have proposed a new material-level measurement method based on the dot matrix laser ranging principle. This method utilizes dot-matrix laser ranging and visualizes the optimized measurement data to ultimately derive information about the material surface's morphology and level. A physical hopper model is used to conduct verification experiments on various material surface morphologies, material levels, and the material hanging on the hopper wall. The results indicate that this method can accurately identify the material level and the material hanging on the hopper wall, preventing false alarms due to “false material levels.”

Perbaikan Desain Mesin Pencacah Daun Pelawan Untuk Meningkatkan Kemampuan Proses Pencacahan

The Pelawan leaf chopper machine is an annual product of LPPM Universitas Brawijaya Malang and in collaboration with several universities, one of which is Bangka Belitung University which is focused on the Pelawan forest, Namang village, Central Bangka Regency. The chopping machine used has dimensions of 30 x 30 x 3 mm, and uses a 200-watt electric motor drive with a voltage of 220 V/150 Hz, with Rpm 2800 and 2 blades in the hopper. During the machine testing process, there were still deficiencies in the tool components which caused the results of the chopping to not be chopped properly. Therefore, it is necessary to identify existing problems and make design improvements to the pelawan leaf chopper machine to increase the capability of the chopping process. Identification was carried out on a pelawan leaf chopper machine in the Mechanical Engineering Laboratory at Bangka Belitung University. From the identification it is obtained; Firstly, the number of blades is 2, which causes the chopping process to not be optimal. Second, the distance between the hopper wall gaps is too wide, which affects the level of fineness of the chopped results. For this reason, design improvements were carried out to provide several alternative concepts (sketches) for the number of blades from various constructions on the machine. The alternatives given are 3 concept variants, the first is a 90° tilt propeller concept variant, the second is a 45° tilt screw layout concept variant and the third is a straight concept variant and a 90° tilt layout. In this research, variations of the concept following the assessment criteria and a distance between the blades of 45° enabled maximum results to be obtained.

Effect of bevelled silo outlet in the flow rate during discharge

We investigate the effect of a bevelled (or slanted) outlet on the discharge rate of mono-sized spheres from a quasi-two-dimensional silo, using the discrete element method. In contrast to hopper discharges, where the bevelling is across the entire base of the container, we study a bevelled opening that is significantly smaller than the silo width and in which the slanting is limited to half a sphere diameter at the boundary of the outlet. We show that the bevelling increases the flow rate comparably to the inclination in hopper walls. Using Beverloo’s model, we relate this increase in rate to what we define as the ‘effective opening’ of the silo and analyse the velocity profiles associated with the discharges. We show that different openings, having effectively the same discharge rates, give rise to distinctly different internal dynamics in the silo. These results have the potential to aid industrial processes by fine-tuning and improving control of silo discharges, with a minimal impact on silo design, thus significantly reducing production and handling costs.

Granular stresses in granular flows subjected to different obstacles

Although the application and development of continuum approaches demonstrate immense promise to model granular flows, the assumption of isotropic stress state in a constitutive law needs to be carefully examined, especially for accurately modeling the kinematics and kinetics of obstructed granular flows. This paper investigates the effect of obstacles on granular stresses and stress ratios in 3D granular silo flows by using discrete element method (DEM). The adopted obstacles include a conical insert, disk insert, BINSERT, hollow cylinder insert and hollow silo insert, as well as the absence of any insert for comparison. A novel (simple but robust) method with ring measurement cells was proposed to determine average stress tensors for granular flows. An innovative slice method with null friction boundaries was also proposed to significantly reduce DEM computational time. The validity of the proposed DEM model was justified by a repose angle experiment and two numerical verification examples. Results reveal that the blocking effect from the obstacles and the hopper wall of the silos led to a significant increase in normal and shear stresses. The normal stresses exhibited slight anisotropy in steady and uniform granular flows, and resulted in a stress ratio of approximately 1.0, indicating an approximately isotropic stress state. Unlike the normal stresses, the shear stresses however showed strong anisotropy even in the steady and uniform regime. The obstructed granular silo flows exhibited strong anisotropy not only in normal stresses, but also in shear stresses. The stress ratio in the obstructed granular flows can appreciably deviate from unity, varying between 0.27 and 2.24. Moreover, the vertical stresses dominated the contact force transmission in the granular silo flows, and showed the formation of dynamic granular arching.

The role of entrained air from the top of the aerated bin in the discharge of cohesive powder

The effect of aeration was investigated as strong wheat flour is discharged from the orifice of open bins. If the orifice diameter is small, part of the aeration air will escape from the top of the bin, and there will be no further increase in powder discharge rate. If the orifice size is large, the additional air is entrained from the top of the bin by accompanied aeration air, and then the discharge rate will increase. The airflow at the top of the bin was estimated by two models. Two aeration methods were investigated: from the conical hopper wall and from the flat bottom. The aeration air was varied in the range up to 30L ∙ min −1 . The diameter of the cylindrical bin was 284 mm, the diameter of the orifice varied from 10 mm to 50 mm, and the flour was not discharged without aeration when the diameter was below 50 mm. • The air entrainment is estimated by two models and confirmed their correspondence. • Two aeration methods were investigated from the conical hopper and the flat bottom. • A part of the aeration air will escape from the top of the bin. • The additional air is entrained from the top of the bin by accompanied aeration air. • The driving force to the particles at the orifice collapses the static arch formation.

Wedge-Shaped Hopper Design for Milled Woody Biomass Flow

The bioenergy industry has been challenged by unstable flow and transport of milled biomass in material handling operations. Handling issues such as hopper clogging and auger jamming are attributed to knowledge gaps between existing handling units designed for bulk solids and their suitability for milled biomass with high compressibility. This work investigates various flow behaviors of granular woody biomass in wedge-shaped hoppers. Hopper flow physical experiments and numerical simulations are conducted to study the influence of the critical material attributes and critical processing parameters on the flow pattern, arching, and throughput. The results show that (1) the preferred flow pattern, mass flow, can be achieved by controlling the material’s internal friction angle, hopper inclination, and hopper wall friction; (2) hopper arching, governed by the competing gravity-driven force against flow resistance from material internal friction and material–wall friction, can be controlled by the hopper wall friction angle and the inclination angle; and (3) flow throughput can be accurately estimated from our empirical equation with inputs of hopper outlet geometry and particle-scale to bulk-scale material attributes. This study elucidates woody biomass flow physics and provides guidance for industrial equipment design.

Modernization of hopper car for transportation of agglomerate and other materials

The paper considers results of the analysis of operability of the transporting equipment at agglomeration shops of the Ural metallurgical enterprises. It was established that during long-term operation of the hopper car for transportation of hot agglomerate, dust settles on its walls, growths of accumulated dust are formed, and the effect of vaulting occurs. Due to compaction and increase in dust layer, useful volume of the hopper car decreases which in turn leads to the need to carry out dangerous work to clean the dust directly inside the hopper car. Manual labor is used for this purpose. Such works are very dangerous for human health due to high dust content and high injury risk. In order to eliminate the problem of vaulting and accumulation of dust on the car walls, it is proposed to use the installation of two vibrating devices of the “False wall” type together with a vibrating neck (vibrating beam). The vibrating element of the device is a plate that is mounted on the inner wall on flexible suspensions (round link chain). Rubber shock absorbers are installed between the plate and the hopper wall, which are used as rubber-fabric conveyor belt. A vibrator is mounted to the plate through the support post, and the transmission of vibrations to the agglomerate is carried out using a vibrating hump, which is welded to the plate (false wall). Introduction of the designed device ensures reduction of unplanned downtime of the hopper cars team and rejection of hazardous to human health work related to the bunkers cleaning. The economic calculation confirms feasibility of the ongoing measures for reengineering of hopper cars in the conditions of agglomerate production at metallurgical enterprises.

Parametric study and design procedure for planar silos and hoppers

This paper presents a parametric study and a new design procedure for wedge-shaped (planar) silos. The analytical part of the study is based on a previously reported theoretical model and considers the influence of granular material properties, material height, bin and hopper geometrical dimensions, and the possible difference between the bin and hopper wall friction coefficients. This study includes new experimental results and analyses regarding the influence of various parameters. It was found that the mass–funnel flow boundaries were almost indifferent to the bin sidewall roughness. In addition, according to the new results, the mass flow mode could be achieved even for very rough hopper walls, but in that case, a stagnant layer of material exists next to the hopper walls. Finally, a new design procedure for planar silos was proposed. The new procedure should help operators and designers of silos to increase the accuracy and flexibility in the assessment of granular flow regime, and therefore it might significantly improve the process efficiency.

Discrete Element Modeling (DEM) based investigation of tribocharging in the pharmaceutical powders during hopper discharge

Triboelectric charging is defined as the phenomenon of charge transfer between two different material surfaces when they are brought into contact and separated. The focus of this research is the development of a Discrete Element Method (DEM) based simulation model to predict tribocharging during hopper discharge. Due to decreased particle-wall interactions and reduced particle wall contact times, net charges generated during hopper discharge are low. The simulation model confirmed this effect and was implemented to predict the triboelectric behavior of glass beads and MCC particles during hopper flow, along with the prediction of percent charged and uncharged particles. Approximately one-third of the particles were predicted to remain uncharged during the hopper discharge simulations for mono-dispersed particles, thus rendering a comparatively high amount of charge distribution into a small concentration of materials. The DEM model acted as a tool to predict charges that can be generated during hopper discharge at a specified geometry, with a potential to mitigate particle charging, when used for appropriate selection of hopper angles, and hopper wall materials.

Substantiation of the parameters of the auger of the feed preparation unit and placement of knives on it

Annotation Purpose. Approbation of the method of determining the design parameters of the auger spiral of the feed preparation unit in the preparation of feed components for feeding, taking into account the interaction of elements: auger, knives, hopper walls. Methods. Theoretical determination of the regularities of reducing the radius of the auger, which is in the hopper of the feed preparation unit in the process of preparing the feed mixture, determines the analytical method of research based on compilation and analysis of equations in the interaction of elements: auger, knives, and hopper walls. Experimental researches are carried out with application of methods of the theory of probability, mathematical statistics, planning of full-factor experiment. The analysis of theoretical data and results of experimental researches is executed with application of applied computer programs and systems. Results. In the feed preparation unit the main working body is a vertical auger. In order to determine the optimal design parameters of the working body, expressions are given for the construction of the auger and the rational interaction of elements: auger, knives, and hopper walls. It is experimentally proved that depending on the design and technological parameters of the feed preparation unit there is an impact on the profitability of the livestock industry. In the process of studying the preparation of feed components for feeding, the influence of the screw speed and the number of knives on the specific energy consumption and quality indicators (grinding and mixing) of the feed mixture was considered. Conclusions 1. During the study of the process of preparation of feed mixture for feeding it was found that in the hopper of the feed preparation unit the lower part of the coil performs the function of collecting feed mixture and feeding it in the vertical direction for further mixing in the middle part of the auger through the unloading window of the hopper. The initial radius of the auger turn is equal to the radius of the hopper at the bottom, except for the technological gap. The upper coil with a knife mounted on it provides active destruction of rolls and packs. 2. With increasing speed of the auger n specific energy increases, and the greater the value of the speed, the more intense the impact on grinding and mixing has the number of knives on the auger, with a stepwise effect. It is experimentally proved that the rational values, of the specific energy, obtained by installing on the auger coil 8 knives and the rotor speed of 25 min-1, while the processing time of the feed components is 7 min. Keywords: auger, mixing, number of knives, lower turn, spiral pitch, efficiency.

Granular material flow regime map for planar silos and hoppers

This study presents a new theoretical model for granular materials flow regimes during discharge from wedge-shape (planar) silos. The new model takes into account the influence of granular material properties, material height, bin and hopper geometrical dimensions and consider the possible difference between the bin and the hopper wall friction coefficients. In addition, the model allows to found an appropriate transition between mass flow and two kinds of funnel flow regimes. By comparing the new model assessments to experimental results, which were found in the literature, good agreement was achieved. Based on the new model equations a generalized flow regime map was presented. The proposed generalized flow regime map should help designers to increase accuracy and flexibility in the granules flow regime assessment and therefore might improve significantly the process efficiency.

Assessment method for fresh concrete spreadability

The results of studies of the fresh concrete spreadability using 3D printing of construction products are presented. The 3D printer is an automated device for the construction of buildings and erectioins, the manufacture of specific structures and products by the method of three-dimensional printing of fine-grained fiber-reinforced concrete with special additives, sand concrete, geopolymer concrete, etc. Assessment methods for the concrete consistency occurring during installation are considered. The applied methods for assessing the spreadability of fresh concrete take into account only its own mass of concrete and do not reflect dynamic processes. The use of the ultrasonic method allows mass testing of products of any shape repeatedly, to continuously monitor the growth or decrease in strength. The disadvantage of this method is the error in the transition from acoustic characteristics to strength. The spreadability of the concrete mixture is estimated depending on the amplitude-frequency characteristics. The dependences of the amplitude of vibrations and accelerations of the paver hopper on the density of the concrete mixture are given. Particular optimization of vibration accelerations by the amplitude of the oscillations of the hopper walls, the amplitude of the oscillations of the charge layers and the stiffness of the vibration dampers is performed.

Secondary air distribution in a 600 MWe multi-injection multi-staging down-fired boiler: A comprehensive study

Multi-injection multi-staging combustion technology was designed to provide high boiler efficiency together with low pollutant emissions when employing hard-to-burn coal, and showed good application prospects. In this technology, to achieve the first staged air and more flexible combustion regulation on the arches, the secondary air employs a more complicated distribution surrounding the coal/air flows. This design concept significantly affects the flow and combustion characteristics of the actual boiler. Elucidating the underlying mechanisms by which the various secondary air parameters affect the boiler operation requires a comprehensive analysis of the secondary air distribution on the arches. In this work, small-scale cold modeling tests combined with industrial-scale trials using two actual 600 MWe down-fired boilers were conducted. The results show that the secondary air distribution can significantly affect the near-burner flow and mixing as well as the decay of the downward airflow velocity. High velocity secondary air, especially the secondary air surrounding the fuel-rich flow, evidently promotes the advanced mixing of fuel-rich and fuel-lean flows. Increasing the secondary air flux around the fuel-rich flow and raising the secondary air velocity decrease the pulverized coal heating rate, while a decreased inner secondary air velocity advances the coal ignition. Adjusting the secondary air also greatly affects the downward flame depth and the unburnt coal proportion in the near wall region of the furnace hopper, such that the flame kernel location and the temperatures near the hopper wall are modified. In addition, NOx formation can be accelerated by a high secondary air flux near the fuel-rich flow or a large contact area between the secondary air and the fuel-rich flow.

New mass flow limiting lines based on segregation pattern and magnitude

Mass flow, by definition, means all of the mass in a hopper will move when some material is discharged from the outlet. Mass flow has been the recommended means to solve segregation issues. This generally works under conditions where the segregation pattern is radial and when the process operation is nearly steady state flow into and out of the hopper. If the segregation pattern is either axial or radial, but the mode of operation is to fill followed by completely emptying the bin, then segregation can easily be an issue – even in mass flow designs. Segregation prevention is all about velocity control, and matching the velocity to the segregation pattern and mode of operation.Ideally, one would like to estimate segregation using easily measured flow properties, segregation potential tests, and a description of the process geometry. This paper looks at a method of predicting segregation problems using flow properties like wall friction angle and effective internal friction angles coupled with the radial stress theory to compute the expected velocity profiles in a variety of process geometries. Using slope stability models, one can also relate the cascade behavior of cohesive material down a pile or slope. Imposing radial stress velocity profiles and cascade velocity profiles in a bin or hopper, then using particle tracking techniques, one can compute the time at which any particle in any portion of the bin might exit the system. Furthermore, imposing a measured segregation profile on the material initially placed in the bin, and then tracking groups of particles with an assigned segregation concentration through the bin, can help determine when and how segregated material might exit the bin. Doing enough of these calculations for a range of wall friction angles and hopper slope values, the velocity profile can be related to the segregation intensity exiting the bin as a function of these two variables. Since these two variables also determine the propensity for mass flow, this analysis can relate mass flow to segregation tendency for material subject to a filling and discharge mode of operation. Selection of an optimal mass flow design would then depend on the segregation pattern and the desired segregation intensity the process can live with.Applying this methodology to a conical hopper suggests that a material prone to segregation will segregate significantly in a funnel flow design. This is to be expected. However, this work also indicates that mass flow bins, when filled and then emptied completely, may experience significant segregation if the hopper walls are designed with traditional mass flow limits in mind. This work suggests that mass flow hoppers must be considerably steeper to mitigate segregation effects for a fill-then-empty mode of operation.

Aerodynamic Characteristics of a 600-MWe Utility Boiler Incorporating Multi-Injection and Multi-Staging: Influences of the Distance between Adjacent Two Burners

ABSTRACTThis work studied the effect of varying the distance between adjacent two burners (DBATB) in a 600 MWe supercritical down-fired utility boiler incorporating multi-injection and multi-staging. Cold-state tests involving airflow trajectory tracing in an actual boiler with a DBATB of 971 mm and 1:20 scale model tests with DBATB values of 971, 1329, and 1687 mm were conducted to study the effects of adjusting DBATB on aerodynamic characteristic. The results indicate that increasing the DBATB had a minimal effect on the symmetric W-shaped flow pattern. A downward airflow rushing the hopper wall was observed at a DBATB of 971 mm, while increasing the value from 971 to 1687 mm promoted decay of the downward airflow velocity in association with gradually enhanced airflow diffusion toward the furnace center. Simultaneously, the airflow rushing the hopper wall disappeared, while the airflow dimensionless penetration depth and the volume of air flowing into the hopper zone were respectively reduced by 12% and 20%. Increasing the DBATB contributes to prevent the actual downward flame from rushing the hopper water wall and form a more uniform heat release along the furnace width. This effect would be expected to avoid local overheating and bursting of the water-wall tube in an actual operational boiler, and an optimal DBATB value of 1687 mm is recommended for this purpose.

Finite element analysis of stresses in a flexible bulk solid container

Current theories and design codes pertaining to storage structures for bulk solids have been developed in the context of rigid-walled silos and may not be applicable for smaller and highly flexible containers that are often used for industrial packaging and intermediate storage. The focus of this study is to investigate the effect of wall flexibility on the bulk stresses and wall pressures during storage using finite element analysis. The results show that when the wall stiffness is low, the computed bulk stresses in the vertical bin section are dominated by plasticity, while the stresses in the hopper section remain in the elastic state. In this situation, the wall pressure in the bin section is heavily influenced by the strength of the stored solid, which controls the extent of plastic flow. Overall, the normal wall pressure in the bin section is found to decrease with wall flexibility leading to a corresponding increase in vertical stress in the stored solid. As a consequence, the stresses in the hopper also increase leading to increasing loads on the hopper walls and potential exacerbation of handling issues for cohesive materials in highly flexible containers.

Design, fabrication and evaluation of fish meal pelletizing machine

A 113.1kg/h fish meal pellet processing machine which produced 4mm diameter pellet, with an average length of 6mm was designed and fabricated. Design values of 210 was used for the maximum angle that the hopper wall formed with the vertical in the discharge zone, a critical stress of 1.3kPa of the ground particulate materials, and a density of 2.4521kg/m3 of the particulate materials, were used to obtain a hopper smallest outlet diameter of 12.7cm with a capacity of 24,118cm3 which proved efficient for the pelletizing machine. Two 3-cm diameter shafts carried the speed reduction gears with the perforated disc attached to the roller cutters on one end, while at the other end a 5hp motor was connected to the speed reduction gear by pulleys with diameters of 6cm and 12cm respectively. The speed reduction was 1:5 over a motor speed of 2000rpm. The fish meal pelletizing machine utilized 4kg of ingredients to produce 3.77kg pellets at an efficiency of 94.2%. The percentage loss due to unprocessed ground particulate materials was 5.8%.The moisture content of the fish meal pellets after 7days of drying in open air was 26.5% (wet basis). When tested for floatation, the pellets stayed afloat for 9 days, while the un-dried pellets only remained afloat for 2days. A combination of the weight of the twin roller cutters and the addition of some starch to the ground particulate materials assisted the compacting and gelatinization of pellet formed. This machine will be useful to medium and small scale aquaculture farmers and also reduce the need for foreign sources of fish meal in the aquaculture industry, thus conserving foreign exchange.Keywords: Ground particulate materials; mixing; compacting; gelatinizing; pelletizing

Influence of the mass ratio of pulverized-coal in fuel-rich flow to that in fuel-lean flow on the gas/particle flow and particle distribution characteristics in a 600 MWe down-fired boiler

Fuel rich/lean combustion is an important means of reducing NOx in coal-fired boilers. The mass ratio of pulverized-coal in fuel-rich flow to that in fuel-lean flow (MRL) is a key parameter in fuel rich/lean combustion that affects the gas/particle flow characteristics and in turn the coal ignition and NOx formation. In this work, using a 1:40 scale model furnace and a particle dynamics anemometer measurement system, the effects of various MRLs (6:4, 7:3, 8:2 and 9:1) on the gas/particle flow characteristics in a 600 MWe down-fired boiler incorporating multiple-injection and multiple-staging were studied. The results demonstrate that airflows injected from the front-arch burners flow downwards along the front wall and then turn upward in the furnace center zone, forming a U-shaped flow pattern. Increasing the MRL significantly raises the maximum particle volume flux under the fuel-rich flow nozzle, which favors advanced pulverized-coal ignition and improves the fuel rich/lean combustion in the boiler. The velocity decay of the downward gas/particle flow is also accelerated. The particle volume flux in the hopper zone is gradually reduced while the location of the maximum particle volume flux gradually moves away from the hopper declined wall. This scenario avoids the downward flame flushing the furnace hopper and prevents both hopper wall overheating and tube bursts in the actual down-fired boiler. Based on these results, an MRL of 9:1 is recommended as optimal.

The effects of fluidised bed and high shear mixer granulation processes on water adsorption and flow properties of milk protein isolate powder

The effects of fluidised bed (FB) and high shear mixer (HS) granulation processes on water adsorption and flow properties of milk protein isolate powder (MPI) were investigated and compared. The agglomerated granules were characterised by different size fractions. It was found that granules produced from the HS process adsorbed less moisture, with slower adsorption kinetics, compared to those produced from using the FB. Granulation reduced the cohesiveness of the MPI powder, with HS having a significant greater impact due to the formation of the particles with higher bulk density and larger size. Particle size played a critical role that influenced water adsorption and flowability. Granulation processes contributed to different degrees to reducing the minimum outlet diameters of hoppers based on either mass-flow or core-flow discharges. HS granules had large wall friction angles, suggesting a need for steeper hopper walls for effective discharge.

Stress pulsation mechanism during filling and discharging granular materials form silos

AbstractIn this paper, we investigate numerically the dynamic pulsation nature of stresses acting on hopper walls during filling and discharging granular materials from silos. From the results, at the end of filling process, it can be concluded that the larger the frictional wall coefficient is, the less the ultimate stress values acting on the hopper wall will be. Furthermore, for smaller values of internal friction, a consistent stress fluctuation appears for a slightly long period of time before the stress trace turns to a straight line. For the discharging process, the required time for the discharging of the silo is almost the same for different values of wall frictions. Moreover, for large values of internal friction coefficients, the discharging process takes more time.