Energy consumption and simulation of pneumatic conveying lateritic mineral in dense and fluid phase

Transcription

1 INTERNATIONAL JOURNAL OF MECHANIC Volume 11, 017 Enery consumption and simulation of pneumatic conveyin lateritic mineral in dense and fluid phase Eduardo J. Díaz, Enrique T. Tamayo, Diana M. Vélez, Dieo R. alazar, César M. Díaz and María P. Cedeño Abstract: The mineral pneumatic conveyin efficiency depends of different equipment that makes considerable impact on enerysavin. The systems are frequently operated in the dilute-phase reime or in the hih air velocity reion and cause hiher power consumption, pipe erosion and particle deradation. Therefore even small reductions in pressure drop and conveyin velocity can obtain improvements in enery-savin, pipe wear and particle deradation. The pneumatic conveyin should keep the pressure drop and conveyin velocity as low as possible. In order to reach this purpose, some enery-savin techniques have been developed. To observe the relationship between the parameters involved in the pneumatic transport of lateritic mineral and obtain the necessary information about the behavior of the variables, it is necessary to simulate the transport characteristics, for which was used the mathematical model in horizontal and vertical pipes, and the losses in elbows. The simulation of pneumatic conveyin systems is developed with the use of experimental - theoretical models to predict areas of lower enery consumption and make the correct selection of the systems. It plays the important role in the research of fluid and dense-phase as solid flow. This article ave the numerical simulation conclusions based on the experimental and theoretical research. The behavior of the specific enery consumption in function of concentration show the tendency to reduced enery consumption with increased concentration of the mixture and therefore the amount of material transported. This increased concentration is limited by the conveyin characteristics dependin on the system parameters and air feeder. The consumption values rane from 4.3 MJ/t to MJ/t, the latter values corresponds with the lower values of as-solid concentration (10 to 0 k/k). Keywords: Enery consumption, Pneumatic conveyin, Pressure drop, Conveyin characteristic. E. J. Díaz is with Equinoccial Technoloical University, Quito City, Ecuador Republic ( eduardo.diaz@ute.edu.ec). E. T. Tamayo is with, Cotopaxi Technical University, Latacuna City, Ecuador Republic ( enrique.torres@utc.edu.ec). D. R. alazar is with Equinoccial Technoloical University, Quito City, Ecuador Republic ( dieo.salazar@ute.edu.ec). D. M. Vélez is with, Cotopaxi Technical University, Latacuna City, Ecuador Republic ( diana.marin@utc.edu.ec). C. M. Díaz is with Julio Moreno Espinosa Technoloical, anto Domino de los Tsáchilas City, Ecuador Republic ( cesardiazk@yahoo.es). M. P. Cedeño is with Julio Moreno Espinosa Technoloical, anto Domino de los Tsáchilas City, Ecuador Republic ( mariapaulina1980@hotmail.com). I. INTRODUCTION The pneumatic transport in the nickel companies has hiher ecoloical indices to other mechanical conveyors. The use has been limited by excessive enery consumption. The causes of this difficulty are: the incorrect selection of the transport air speed and the infinite variety of physical and aerodynamic characteristics of materials to transport. Pneumatic conveyin is one of the most advanced means of solids transport. The most used are in the nickel industry and the transport of cement, coffee and rains. The pneumatic conveyin efficiency in the nickel industries depend of different equipment that make considerable impact on enery-savin. The systems are frequently operated in the dilute-phase reime or in the hih air velocity reion and cause hiher power consumption, pipe erosion and particle deradation. Therefore even small reductions in pressure drop and conveyin velocity can obtain improvements in enery-savin, pipe wear and particle deradation. Then as an important desin criterion, the pneumatic conveyin should keep the pressure drop and conveyin velocity as low as possible. In order to reach this purpose, some enery-savin techniques have been developed. The simulation of pneumatic conveyin systems is developed with the use of experimental - theoretical models to predict areas of lower enery consumption and make the correct selection of the systems. It plays the important role in the research of dense-phase as solid flow. This article ave the numerical simulation conclusions based on the experimental and theoretical research. By associatin with experimental condition and the applicability of experimental equations, transport equation was deduced by usin time averaed method based on instantaneous equation of as and solid. Two-fluid model of as-solid turbulence in process of dense-phase as solid two phase flow was founded, so did the correspondin numerical solution and calculatin flow. The model could mention reciprocity between as and solid, collision of particles and interaction between particle and wall. The model development for lateritic mineral pneumatic conveyin in dilute and dense phases in horizontal and vertical pipes was developed takin in consideration the variety of physical and aerodynamic characteristics the materials to transport. The principal parameters of the model are: difference of speed between the as and the solid and flotation speed. To obtain the parameters of the model was used the differential equations solution method, Rune - Kutta fourth order [1]. In order to reduce power consumption and conveyin IN:

2 INTERNATIONAL JOURNAL OF MECHANIC Volume 11, 017 velocity, Rinoshika and uzuki [] developed an experimental study of enery-savin pneumatic conveyin system in a horizontal pipeline. The maximum reduction rates of the minimum velocity and power consumption by the dune model are about 19 % and 34 %, respectively. Yan and Rinoshika [3] applied a new pneumatic conveyin system where soft fins are horizontally mounted on the center plane of pipe. The maximum reduction rates of the power consumption by usin soft fins are about 5.5 %. Li and Tomita [4] applied the swirlin flow to pneumatic conveyin system for reducin power consumption. Their studies concluded that the application of swirlin flow could reduce the critical and minimum conveyin velocities, the pressure drops, the fluctuations in the wall static pressure, and the power consumption. Wypych and Yi [5] proposed a description for dense-phase pneumatic conveyin and its boundaries based on a 3-layermodel. They also established a method to predict the pressure drop in a horizontal pipeline by slu-flow pneumatic conveyin. The effects of air inlet velocity and the conveyin capacity on the flow behavior were also discussed. Both parameters played a sinificant role in the conveyin flow pattern and also the pressure drop. Liu [6], Vasquez [7], antos [8], establish the behavior of dense and fluid phase and its effect on pressure drop. They take in consideration Visual analysis and distribution the particle over the pipe cross-section. arrami and Mohsen [9] perform the simulation of as-solid flow throuh pipelines. They analyses the effects of air inlet velocity and the conveyin capacity on the flow behavior. Both parameters played a sinificant role in the conveyin flow pattern and also the pressure drop. Numerical imulations of dilute and dense phase in pneumatic conveyin were developed in different investiations [10]- [13]. The authors take in consideration diverse conditions: conveyin in lon-distance pipe, horizontal and vertical pipes, particles throuh a 90 derees elbow, and as-solid heat transfer. In this paper, to reduce power consumption and conveyin velocity, with the values of the pattern parameters, the pneumatic conveyin after the lateritic mineral millin process is simulated. The behavior of the current parameters is compared with those obtained throuh the simulation. Transport characteristics are constructed and rational work area is established from considerations on enery consumption. The objective of the article is et values less enery consumption from transport characteristics of lateritic mineral. II. METHOD DEVELOPMENT The model development for lateritic mineral pneumatic conveyin in dilute and dense phases in horizontal and vertical pipes is elaborated from the simultaneous use of mass, momentum and enery balance equations.the expression (1) constitutes the theoretical model for calculation the pressure losses in lateritic mineral pneumatic conveyin in function of the pipe lenth [1]. ( V V ) ε ρ V 1 V + dp λ ε ρ 1+ + ε ρ µ = V + P P dx D (1) V V V f + + 0,165 ε ρ + 1+ senδ µ µ ε ρ cos δ V V V V D The simplifications of these expressions in horizontal and vertical pipes are in the equations () and (3). In horizontal pipes, the inclination anle is zero, for this reason ερv 1 V ( V + V) dp 1+ + ερ µ = P P dx () λ V ε ρ Vf 0,165 V + µ ερ + V D V V D In vertical pipes, the inclination anle is ninety, for this reason ( V V ) ε ρ V 1 V + dp λ ε ρ V 1+ + ε ρ µ = + P P dx D (3) V V 0,165 + ε ρ 1+ µ + V V µ ε ρ V D In table 1 the results of flotation and relative velocity are exposed for each one of particles diameters. The flotation velocity was determined experimentally in [1]; the relative velocity is determined by adjustment of the model. Table 1 Relative and flotation velocity values for different diameters of particles. Horizontal pipe Vertical pipe dx (mm) V A-V A Vf A E (%) V A-V A Vf A In the nickel company there are three main roups of pneumatic conveyin systems: Pneumatic conveyin from the dryin to the mills process (system 1). Pneumatic transport from the mills process to the silos (system ). Pneumatic conveyin from silos to the reduction furnaces process (system 3). Details of the systems shown in Table. Table Details of lateritic mineral pneumatic conveyin systems. ystem Diameter (mm) Lenth (m) Number Amount of Horizontal Vertical of material elbows (t/h) E (%) 0,50 4,7 5,1 7,84,3 5,1 7,10 0,1875 3,6 4,74 8,0 1,97 4,74 8,53 0,1075 3,39 3,83 9,31 1,51 3,83 10,07 Mezcla 5,18 5,1 9,54,74 5,1 7, For the construction of lateritic mineral pneumatic conveyin characteristics is necessary also to know the losses in elbows. The equation to determine the losses in elbows is the followin. IN:

3 INTERNATIONAL JOURNAL OF MECHANIC Volume 11, 017 PCT = PC + P (4) r When the material arrive to the inlet of the elbow, continues movin straiht ahead to the first impact zone (ΔP C ). The material is deflected at an anle toward the outlet of the elbow. The deflection anle is determined by the elbow desin, the product's characteristics, the conveyin velocity, and the specific load. The product will hit the secondary impact zone before exitin the elbow (ΔP r ). Losses in the first impact zone are obtained by the equation PC = P + P (5) Losses due to the material are obtained by equation V P = ξ ρ (6) The resistance coefficient, ξ 0,5 0, R 0,1 0,35 D 0,65 0,35 1,09 = A Re Res Frs Fr ξ D d µ Losses in the secondary impact zone are obtained by the equation V Pr = βρ (8) For the vertical confiurations 0,45 0,1 0,15 ρ D,59 β = 1,5510 Res µ (9) ρ d For the horizontal confiurations 0,9 0,5 0,4 0,8 0,3 ρ D 3,81 β = 0, 810 Re Res Fr µ (10) ρ d Enery cost The enery consumption of mineral pneumatic transport systems depends fundamentally on the air and material feeder. Considerin the pressure losses in the supply chamber and the separator, the power demand is estimated from the followin expression. P 1 N = 177 M Ln (11) P If the above equation is divided by the amount of transported material, the specific enery demand is obtained. With these results and the transport characteristics are estimated of rational parameters of lateritic mineral pneumatic conveyin systems and predict the behavior of any other system. III. REULT AND DICUION The behavior of the pressure loss for different pipe diameters, horizontal and vertical confiurations was simulated with the use of models obtained by Torres et al [1]. The fiures 1 and, examine the influence of as velocity in Pressure Loss durin pneumatic transport of lateritic mineral. In Fiure 1 the low as velocity values are observed for the low pressure losses, this area corresponds with the transition between the fluid and dense phase. From these values the pressure losses increase with increasin as velocity and a rapid reduction in the concentration of the mixture occurs. In horizontal pipes the averae value of the transport speed is 6.1 m/s. In the zone of low pressure drop, reducin the as speed causes a rapid increase in the concentration of solid. The as (7) cannot transport all the material and collect in the bottom of the pipe. In Fiure, for vertical pipes, the averae value of the transport speed is 5.1 m/s. In the systems is necessary to choose the conveyin minimum speed. Fi. 1 Pressure drop behavior in function of the as speed for horizontal pipes Once these results are known, in addition to settin the speed of chane between dense and fluid phases, can be built characteristics of pneumatic conveyin in industrial conditions, determine the rational parameters, define the specific enery consumption and simulate the behavior of any other system workin. Fi. Pressure drop behavior in function of the as speed for vertical pipes The pressure drop in the elbows increases with mass flow and concentration of the mixture (fiure 3). The hihest values of pressure losses correspond to concentrations of 60 k/k. The values of pressure drop reach.3x10 3 Pa/m when as mass flow is 0.8 k/s. Fi. 3 Pressure drop behavior in function of the as speed for elbows IN:

4 INTERNATIONAL JOURNAL OF MECHANIC Volume 11, 017 imulation of transport characteristics in horizontal and vertical pipes In the analysis of losses elbows is necessary to consider the position in which it is placed, can be horizontal or vertical; althouh the influence of the position is not sinificant in losses for industrial systems. These results are not sufficient to define the parameters of pneumatic transport, althouh allow to obtain preliminary criteria, which are complemented by the analysis of transport features, and enery specific consumption of the systems. To observe the relationship between the parameters involved in the pneumatic transport of lateritic mineral and obtain the necessary information about the behavior of the variables, it is necessary to simulate the transport characteristics, for which was used the mathematical model in horizontal and vertical pipes, and the losses in elbows (equations -10). The operatin point of a pneumatic conveyin system can be specified by three fundamental parameters: The variation of the solid mass flow throuh the pipe. The variation of as mass flow used for transportin solids. The pressure drop required to transport the flow. The first parameter specifies the point of system performance and the other, the operatin point of the air feeder (usually the most expensive component of the system). With the use of the three possible rane of operatin conditions achieved by a bulk material in a particular system is defined, this behavior is known as the transport of materials feature. The behavior of the solid mass flow dependin on as mass flow and pressure drop necessary to convey the material is exposed to different concentrations in the transport characteristics. These are simulated for horizontal, vertical pipes and elbows. In horizontal pipes this behavior is observed in Fiure 4. The values of rational work of pneumatic conveyin systems are to the left of the fiures, where the hihest concentration values and lower pressure losses are achieved. With increasin concentration of the mixture, increases the solid mass flow, but this is accompanied by increased pressure drop in the system. The selection of rational parameters and workin with the raphs of transport characteristics is necessary to consider the enery specific consumption. Fi. 4 Pneumatic conveyin characteristic of lateritic mineral in horizontal pipes, D=00mm The hihest values of pressure drop correspond to concentrations of 60 k/k. The pressure drop increases with the mixture concentration and the mass flow of as. The minimum values of the pressure drop (below to 3x10 3 Pa/m), correspond with the values of the mass flow of as, less than 0.8 k/s. The values of solids mass flow reach 10 t/h, allowin transport the quantity of material needed at each stae of the process (Fiure 4). Fi. 5 Pneumatic conveyin characteristic of lateritic mineral in horizontal pipes, D=50mm Transport speed of the solid-air mixture in horizontal pipes is reduced with increasin pipe diameter. Pressure drop in pneumatic conveyin of solids also is reduced. Comparin fiures 4 and 5 show that is possible to reduce the pressure drop around 30 %, when increase pipe diameter from 00 mm to 50 mm in the transport of lateritic mineral. Fi. 6 Pneumatic conveyin characteristic of lateritic mineral in vertical pipes, D=00mm Pneumatic conveyin characteristic of lateritic mineral in vertical pipes is observed in Fiure 6. The pipe diameter is 00 mm. Comparin fiures 4 and 6 for the same diameter; the pressure losses in the vertical transport are bier than the horizontal one. The values of pressure drop for a vertical transport reach 3.5x10 3 Pa/m when as mass flow is 0.8 k/s. The values in horizontal conveyin are less than 3.5x10 3 Pa/m. In vertical pneumatic conveyin, the total pressure drop is due to acceleration, ravity, and wall friction. Comparin fiures 6 and 7, for a fixed solid mass flow rate, reducin the as flow rate (increasin the pipe diameter from 00 mm to 50 mm) the frictional resistance of the flowin mixture is reduced. IN:

5 INTERNATIONAL JOURNAL OF MECHANIC Volume 11, 017 Fi. 7 Pneumatic conveyin characteristic of lateritic mineral in vertical pipes, D=50mm When decreasin the as velocity the chane in the frictional resistance predominates and the pressure drop decreases. A further lowerin of as mass flow causes a rapid rise in solid mass flow and static head that produces an increase in pressure drop. This opposition of forces that chane with flow rate in the opposite direction results in the occurrence of a minimum in the pressure drop curve, which is known as chockin behavior. Fi. 8 Behavior the specific enery consumption dependin on the mixture ratio The behavior of the specific enery consumption in function of concentration is shown in Fiure 8. The tendency to reduced consumption with increased concentration of the mixture and therefore the amount of material transported can be observed. This increased concentration is limited by the conveyin characteristics dependin on the system parameters and air feeder. The consumption values rane from 4.3 MJ/t to MJ/t, the latter values corresponds with the lower values of as-solid concentration (10 to 0 k/k). IV. CONCLUION In the analysis of losses elbows is necessary to consider the position in which it is placed, can be horizontal or vertical. The values of pressure drop reach.3x10 3 Pa/m when as mass flow is 0.8 k/s. The pressure drop increases with the mixture concentration and the mass flow of as. The minimum values of the pressure drop (below to 3x10 3 Pa/m), correspond with the values of the mass flow of as, less than 0.8 k/s. The values of solids mass flow reach 10 t/h, allowin transport the quantity of material needed at each stae of the process. The pressure losses in the vertical transport are bier than the horizontal one. The values of pressure drop for a vertical transport reach 3.5x10 3 Pa/m when as mass flow is 0.8 k/s. The values in horizontal conveyin are less than 3.5x10 3 Pa/m. In vertical pneumatic conveyin, the total pressure drop is due to acceleration, ravity, and wall friction. For a fixed solid mass flow rate, reducin the as flow rate (increasin the pipe diameter from 00 mm to 50 mm) the frictional resistance of the flowin mixture is reduced. When decreasin the as velocity the chane in the frictional resistance predominates and the pressure drop decreases. The behavior of the specific enery consumption in function of concentration show the tendency to reduced enery consumption with increased concentration of the mixture and therefore the amount of material transported. This increased concentration is limited by the conveyin characteristics dependin on the system parameters and air feeder. The consumption values rane from 4.3 MJ/t to MJ/t, the latter values corresponds with the lower values of as-solid concentration (10 to 0 k/k). Nomenclature: Ɛ - mixture porosity δ- anle of pipe V - as velocity, m/s V f - flotation velocity, m/s ρ - air density, k/m 3 λ - as friction coefficient ρ s - solid density, k/m 3 ξ - resistance coefficient μ- mixture ratio, k/k D- Pipe diameter, m d- material diameter, m ΔP CT - total losses in the elbow; Pa ΔP c - losses in the first impact zone; Pa ΔP r - losses in the secondary impact zone; Pa ΔP- losses for clean air; Pa ΔP s - losses due to the material; Pa A- Coefficient dependin on the elbow position Re, Re s - Reynolds number for air and solid Fr, Fr s - Froude number for air and solid R- elbow radius, m β- loss coefficient in the secondary impact zone N- power demand, kw R- air mass flow, k/s P 1, P - inlet and outlet pressure, bar REFERENCE: [1] Torres T. E., et al. Consideration about lateritic mineral pneumatic conveyin in dense phase. International Journal of Mechanics (015), vol. 9, pp IN: [] Rinoshika, A.; uzuki, M. An experimental study of enery-savin pneumatic conveyin system in a horizontal pipeline with dune model. // Powder Technoloy. 198, (010), pp [3] Yan F., A. Rinoshika. An experimental study on a horizontal enerysavin pneumatic conveyin system (015). The 7th World Conress on Particle Technoloy (WCPT7). Procedia Enineerin 10, pp [4] Li H., and Y. Tomita, An Experimental tudy of wirlin Flow Pneumatic Conveyin ystem in a Vertical Pipeline (1998), Trans. AME, J. Fluids En., 10, pp [5] Wypych P. W. and J. Yi. Minimum transport boundary for horizontal dense-phase pneumatic conveyin of ranular materials (003). Powder technoloy, Vol.19, pp [6] Liu. et al. Characteristics of as-solid two-phase flow in axial and swirlin flow pneumatic conveyin. Tehnički vjesnik 1, 4(014), pp IN:

6 INTERNATIONAL JOURNAL OF MECHANIC Volume 11, 017 [7] Vasquez et al, (008), Visual analysis of particle bouncin and its effect on pressure drop in dilute phase pneumatic conveyin, Powder Technoloy, 179, [8] antos. M. et al. Dilute-phase pneumatic conveyin of polystyrene particles: pressure drop curve and particle distribution over the pipe cross-section (011). Chemical Enineerin 8 (1), pp [9] arrami A F., Mohsen N. CFD imulation of as-olid Two-Phase Flow in Pneumatic Conveyin of Wheat (015). Chemical Enineerin Vol. 34, Issue 4, pp [10] Laín., M. ommerfeld, and B. Quintero (009). Numerical simulation of secondary flow in pneumatic conveyin of solid particles in a horizontal circular pipe. Chemical Enineerin 6 (3), pp [11] Zonmin Liu, uanbin Duan and Kun Wan (011). Numerical imulation of Dense Phase Pneumatic. Conveyin in Lon-Distance Pipe, Computational imulations and Applications IBN: , InTech, pp [1] Vashisth,. and race, J.R. (01). imulation of ranular Transport of eldart Type-A, -B, and -D Particles throuh a 90 Derees Elbow. Industrial & Enineerin Chemistry Research, 51, [13] Rajan, K.., rivastava,.n., Pitchumani, B. and Mohanty, B. (006) imulation of as-olid Heat Transfer durin Pneumatic Conveyin: Use of Multiple as Inlets alon the Duct. International Communications in Heat and Mass Transfer, 33, Eduardo Javier Díaz Chicaiza (M'016). He was born in Ecuador, Year 1977, raduate of Mechanical Enineer (004) in Polytechnic Hiher chool of Chimborazo, Ecuador. Electromechanical Master (015) in Cotopaxi Technical University, Latacuna City, Ecuador. Currently workin in the Electromechanical Enineerin Department, Enineerin Faculty, Equinoccial Technoloical University, Quito City, Ecuador Republic. He is expert in thermal and fluids process, has developed investiations related with heat transfer in industrial processes, transport of two-phase and sinle-phase fluids; modelin and simulation of thermal processes and transportation of fluids with the employment of finite elements method. Enrique Torres Tamayo (M'015). He was born in Cuba, Year 1966, raduate of Mechanical Enineer (1993) and Electromechanical Master (1999) in the Minin and Metallurical Hiher Institute of Cuba, Doctor in Technical ciences (PhD) in the Cuban ciences Academy (003). He worked in Mechanical Enineerin Department at Minin and Metallurical Hiher Institute of Cuba from 1993 to 014, currently workin in the Electromechanical Enineerin Department, Cotopaxi Technical University, Latacuna City, Ecuador. He is expert in thermal and fluids process, has developed investiations related with heat transfer in industrial processes, transport of two-phase and sinle-phase fluids; modelin and simulation of thermal processes and transportation of fluids with the employment of finite elements method. IN: