Experimental Analysis of Dilute Phase Pull Push Type Pneumatic Conveying System to convey Powdered and Granular Material

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VSRD-MAP, Vol. 1 (1), 2011, 19-26

R RE EV VIIE EW W A AR RT TIIC CLLE E

Experimental Analysis of Dilute Phase Pull Push Type Pneumatic Conveying System to convey Powdered and Granular Material 1

LP Dhole*, 2LB Bhuyar and 3GK Awari

ABSTRACT Pneumatic conveying system is a conventional material handling system like belt conveyor or chain conveyor. The main advantage of pneumatic conveying system is that material is transferred in close loop, thereby preventing the environmental effect on the material and vice versa. The experimental analysis of venturi feeding system, which can be used for the suck blow type pneumatic conveying system, is presented. The objective of the work was to develop the venturi feeding system to create automatic suction effect, and to convey material further in the stream of air. Such type of feeding system can be then used for many industrial applications, for example automatic feeding of bulker with powdered or granular material. The four systems having different configurations were fabricated for the analysis purpose, and reciprocating compressor as well as centrifugal blower was used as a source for air and trials were taken. This paper mainly deals with the experimentation of the venturi feeding system, and the suction effect developed at the venturi throat is presented. Keywords : Pneumatic Conveying, Venturi Feeder, Dilute Phase.

1. INTRODUCTION Pneumatic conveying is a practical method for in-plant distribution of large amounts of dry powdered, granular, and palletized materials[1]. Based on the quantity of air used and pressure of the system, pneumatic conveying system is divided in to two type’s viz. dense phase pneumatic conveying system and dilutes phase pneumatic conveying system. In dilute phase conveying, solid particles are introduced into a fast flowing gas stream where solids remain suspended. Such process systems operate at relatively low pressure and consequently are comparatively inexpensive to install[1]. Dense-phase pneumatic conveying is defined as the conveying of ____________________________ 1

Assistant Professor, Department of Mechanical Engineering, Government College of Engineering, Chandrapur, Maharastra, INDIA. 2Professor, Department of Mechanical Engineering, Prof. Ram Meghe Institute of Technology & Research, Amravati, Maharastra, INDIA. 3Principal, Department of Mechanical Engineering, Tulsiramji Gaikwad Patil College of Engineering & Technology, Nagpur, Maharastra, INDIA. *Correspondence : [email protected]

LP Dhole et. al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 1 (1), 2011

particles by air along a pipe which is filled with particles at one or more cross-sections. There is much confusion over the use of the term dense-phase conveying and, as a result, many different definitions have been proposed, based on the solid loading ratio, pressure and quantity of air used[2]. Easiness in controlling and flexibility in installations are some of the favourable features of pneumatics applications in many industrial and nonindustrial fields. It has a wide range of applications, with examples ranging from domestic vacuum cleaners to the transport of some powder materials over several kilometers[3]. The industrial field where pneumatic conveying system is extensively used includes Chemical process industry, Pharmaceutical industry, Mining industry, Agricultural industry, Mineral industry, and Food processing industry. Virtually, all powders and granular materials can be transported using this method. Murilo D.M. Innocentini et al[4] experimentally investigated the dehulling process of cracked soybeans in 2008 and it has been shown that the efficiency of the pneumatic device to remove hulls from the cracked soybean was very high, with the recovery of meats with purity around 99%. In Ref.[5-6], a list of more than 380 different products, which have been successfully conveyed pneumatically, is presented. It consists of very fine powders, as well as the big crystals such as quartz rock of size 80 mm Lot of experimental work has been carried out on the bulk transportation using pneumatic conveying system. R. Pan and P.W. Wypych presented test design procedure for low-velocity slug flow pneumatic conveying of bulk solid materials with irregular-shaped materials like muesli, maize germ[7]. Based on the particle properties and data from a simple vertical test chamber, the pressure drop and slug velocity in low-velocity slug flow can be predicted accurately by this method in large-scale systems. Experimental analysis was carried out by Jens Reppenhagen, Arwed Schetzschen, and Joachim Werther[8] to find the optimum cyclone size with respect to the fines in pneumatic conveying systems. Two different design aspects for cyclones were considered. The first aspect was to keep the product as free of fines as possible and the second one was to minimize the cyclone loss rates. Besides the mechanisms of the true gas-solids separation, the production of fines due to particle attrition was identified to affect these two aspects. A first approach of a new design procedure was therefore provided, where an attrition model is implemented in a conventional cyclone model. P. Guiney, R. Pan, J.A. Chambers used Scale-up technology in low-velocity slug-flow pneumatic conveying[9]. The mechanisms involved at the boundaries were investigated. Based on the understood mechanisms, a small and specific test rig was designed and built. As long as a sample of the conveyed product is tested in such test rig, the boundaries for the product can be determined directly and accurately. Hence, by combining the procedure for predicting the total pipeline pressure drop and the method for locating the boundaries, a simple and reliable scale-up technology was presented for the design of low-velocity slug-flow pneumatic conveying systems. Recent work on pneumatic conveying falls into the more general framework of powder technology and gasparticle flow. Tsuji[10] discusses the multi-scale modeling of dense phase flow. Takei, Ochi, Saito, and Horii[11] and Takei, Ochi, and Saito[12] experimentally investigate the mechanism of plug flow. Hirota, Sogo, Marutani, and Suzuki[13] examine the mechanical properties of powders on the dense-phase flow in an inclined pipe. Futamura[14] discusses the design of plug conveying lines. Li and Tomita measures particle velocity and concentration in horizontal (Li & Tomita,)[15] and vertical (Li & Tomita,)[16] dilute swirling flow pneumatic

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conveying, and examines the characteristics of horizontal swirling flow including curved pipe (Li, 2000)[17]. (Li)[18] proposes application of wavelet multi-resolution analysis to pressure fluctuations of gas-solid two-phase flow in a horizontal pipe. As related topics, there are numerical simulations of tribo-electrification (Tanoue, Tanaka, Kitano, & Masuda,)[19] and electrostatic charge (Watano, Saito, & Suzuki,)[20], control of electrification (Watano,)[21], attrition of granules (Konami, Tanaka, & Matsumoto, 2002)[22] and snow conveying (Kobayashi, 2005)[23]. This is the present status of experimental work, which has been carried out by research in the recent time. The basic objective of this work is to use the venturi feeder system for the pull push type pneumatic conveying system, thereby achieving the automatic suction of the material for industrial applications. The work is divided into two parts viz. develops the feeding system for automatic feeding of material into the system and secondly takes the trial on this feeding system for the industrial application. This work is an attempt to present the experimental work, which has been carried for the feeding system, especially venturi feeding system. Though the venturi feeder is a commonly used device for pipeline feeding purpose, but the main objective of the work was to use venturi-feeding system for pull-push type pneumatic conveying system to create automatic suction effect. Such type of work is not carried in the field of pneumatic conveying system.

2. PIPELINE FEEDING DEVICES Many diverse devices have been developed for feeding pipelines. Some are specifically appropriate to a single type of system, such as suction nozzles for vacuum systems. Others, such as rotary valves, screws and gate valves, can be used for both vacuum and positive pressure systems. The approximate operating pressure ranges for various pipeline-feeding devices is shown in figure 2.1.[24] It will be seen that there is no scale on the vacuum side of figure 2.1. This is because the pressure of operation is only atmospheric and there will be essentially no pressure difference across the feeder, regardless of the type of feeder. In some situations a small resistance may be built into the system but this is generally only to help promote flow into the feeding device. Developments have been carried out on most types of feeding device, both to increase the range of materials that can be successfully handled, and to increase the operating pressure range of the device. Each type of feeding device, therefore, can generally be used with a number of different types of conveying system, and there are usually many alternative arrangements of the feeding device itself.

Fig. 2.1 : Approximate operating pressure ranges for

Fig. 2.2 : Basic Type Of Venturi Feeder

various pipeline-feeding devices

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2.1. Venturi Feeders The basic problem with feeding positive pressure systems is that the air leakage arising from the adverse pressure gradient can interfere with the flow of the material into the pipeline; this situation can be improved, to a certain extent, by using venturi feeders. Venturi feeders work on the principle of reducing the pipeline crosssectional area in the region where the material is fed from the supply hopper, as shown in figure 2.2. It will be seen that there are no moving parts with this type of feeding device, which has certain advantages with regard to wear problems. There are, however, no inherent means of flow control either, and so this has to be provided additionally.

3. VENTURI FEEDING SYSTEM FOR PULL-PUSH TYPE PNEUMATIC CONVEYING SYSTEM If venturi feeding is required to be used for the pull push type pneumatic conveying system, the feeding system has to perform two functions viz. to create the suction effect followed by the pushing the material through the pipeline in the stream of air. System 1: Length of converging part=102.24mm Length of diverging part=179.24 mm Diameter of throat=38.1 mm Inclination of throat inlet = 450

System 2: Length of converging part=70mm Length of diverging part=100mm Diameter of throat=56mm Inclination of throat inlet = 450

System 3: Length of converging part=165mm Length of diverging part=245mm Diameter of throat=25.7mm Inclination of throat inlet = 450

System 4: Length of converging part = 102.24mm Length of diverging part=179.24 Diameter of throat=38.1 Inclination of throat inlet = 900

Fig. 3.1 : Four Systems Used For Experimentation The reduction in flow area results in increasing the entraining air velocity and a corresponding decrease in pressure in this region. For the venturi throat is the section of least cross section, so the least pressure will be at the throat, if we can reduce the throat pressure below atmospheric pressure, then suction effect can be achieved.

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Then inlet provided at the throat will create the suction effect of the material. As the air passes towards the divergent section, air pressure will goes on increasing; this pressurized air will convey the material further into the pipeline. Thus the pull push effect will be achieved with the help of venturi feeding system. The venturi for the pull push type conveying system is designed considering general considerations as Convergent cone of venturi has a total included angle of 21°±1°, length of convergent cone parallel to axis = 2.7(D-d), Where Ddiameter of inlet section, d-diameter of throat. Diameter of throat varies from 1/3 to ¾ of the pipe diameter (Generally ½ times diameter of pipe). Length of throat was taken equal to the diameter of inlet section. The divergent cone has a total included angle lying between 5° to 15°. Length of inlet pipe kept as 1500mm whereas the length of outlet pipe was kept as 2000mm for all the systems. The systems used for the experimentation purpose are shown in fig. 3.1.

4. TRAIL & ANALYSIS Single stage reciprocating compressor and centrifugal blower were used for the experimentation. The results obtained for the reciprocating compressor was not satisfactory so are not discussed here. Then we decided to use centrifugal blower for experimentation. After this we fabricate four venturimeter with different dimensions and readings were taken by following the same procedure as above with centrifugal blower. The centrifugal blower was then used for taking trials created the suction effect at the throat opening. Blower discharge for full opening was 0.521m3/sec. The blower efficiency was around 35%. The objective of the experiment was to measure the suction pressure developed at the inlet provided at the throat. The pressure developed at the inlet of the venturi and at the throat opening is presented in the table 1 below for all the four systems. Table 1: Pressure Developed At Inlet & Throat Section Blower Opening ¼ ½ ¾ 1 ¼ ½ ¾ 1

Head at Inlet of System h1 (cm) h2 (cm) 20.3 37.8 17.4 40.8 16.5 41.7 16 42 29 30.4 28.5 31 28.5 31 28.4 31.1

Pi (bar) 1.0304 1.0359 1.0377 1.0385 1.0116 1.0117 1.0117 1.0118

Head at Throat of System h3(cm) h4 (cm) Pt (bar) 20 40 0.933 16.5 43.5 0.9866 15.1 45.2 0.9834 15 45.4 0.9830 19.5 21.3 1.0112 19.3 21.7 1.0106 19 22 1.010 18.9 22.1 1.0092

SYSTEM III

¼

26

36.5

1.0233

14.8

26.2

1.00185

SYSTEM IV

½ ¾ 1 ¼ ½ ¾ 1

25.5 25.4 25.2 20.3 17.4 16.5 16

34 34.1 34.4 37.8 40.8 41.7 42

1.0214 1.0215 1.0220 1.0302 1.0359 1.0377 1.0385

14.5 14.3 14.2 40 43.4 45.2 45.4

26.5 26.6 26.7 20 16.5 15.1 15

1.00126 1.00097 1.00077 0.9933 0.9866 0.9834 0.9831

SYSTEM I

SYSTEM II

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1.05 1.04 1.03 1.02 1.01 1 0.99 0.98 0.97 0.96 0.95

1.05 1.04 1.03 1.02 1.01 1 0.99 0.98 0.97 0.96 0.95

throat pressure inlet pressure

throat pressure inlet pressure

1/4th 1/2 3/4h full open open opent open

System-II

System-I

1.05 1.04 1.03 1.02 1.01 1 0.99 0.98 0.97 0.96 0.95

throat pressure inlet pressure

1/4th open

1/2 open

3/4h opent

full open

System-III

1.05 1.04 1.03 1.02 1.01 1 0.99 0.98 0.97 0.96 0.95

throat pressure inlet pressure

1/4th open

1/2 open

3/4h opent

full open

System-IV

Fig. 4.3.1 : Graphical representation of throat & inlet pressure vs blower opening for system I to IV We were interested in developing negative pressure at the throat opening provided for the material inlet at the throat, so that considerable materials flow rate can be achieved. It can be seen from the observation table-I that negative pressure is achieved for all the four systems. It is clear the graph that suction at the throat section increases with the blower opening. It is maximum for full opening i.e. at full discharge. The maximum suction is developed for the system-IV at full opening. Figure 4.3.1 shows the graphical representation of throat & inlet pressure vs. blower opening for system I to IV. Throat pressure decreases as the increase in supply of the quantity of air where as inlet pressure increases. This nature of the graph is same for all the systems. So by increasing the quantity of air suction effect at the throat can be increased. Using scaling up technique further analysis of the system can be carried out.

5. CONCLUSION The main objective of the work was to use venturi-feeding system for the pull push type pneumatic conveying system, thereby developing the suction effect at the venturi throat. This will help to create the automatic suction of the material into the system through the inlet provided at the throat. This system then can be operated by the single person and has numerous practical applications for the automatic transportation of powdered and granular

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material. We have fabricated four systems and achieved suction effect at the inlet provided at the throat. The maximum quantity of air used for the experimentation purpose was 0.521 m3/min and maximum suction effect achieved was 0.9831 bars. So by increasing the quantity of air and by changing the dimensions suction effect can be increased. This suction effect in now required to be tested for the material transportation.

6. REFERENCES [1] L.B. Bhuyar, L.P. Dhole, G.K. Awari, Experimental Analysis of Venturi Feeder System for Pull Push Type Pneumatic Conveying System, Proceedings of the 4th International Conference on Advances in Mechanical Engineering (ICAME) SVNIT 23-25, Sepember 2010, Surat India. [2] F. Pon, K.K. Botros, P. Grabinski, B. Quaiattini, L. Motherwell. Experimental and Plant Data of Pneumatic Conveying Characteristics of Seven Granular Polyethylene Resins in Horizontal and Vertical Pipes. Presentation at the AIChE Annual Meeting, Particle Technology Forum, Pneumatic Conveying November 7-12, 2004, Austin, Texas. [3] Konrad, K. Dense-Phase Pneumatic Conveying: A Review. Powder Technology, 49 (1986) 1 – 35. [4] Murilo D.M. Innocentini, Wellington S. Barizana, Maicon N.O. Alvesa, Reinaldo Pisani Jra. Pneumatic separation of hulls and meats from cracked soybeans Food and bioproducts processing. Volume 87, Issue 4, December 2009, Pages 237-246 [5] Chandana Ratnayake. A Comprehensive Scaling Up Technique for Pneumatic Transport Systems, Ph.D.Thesis Norwegian University of Sceince and Technology (NTNU), Porsgrunn, September 2005, 1721 [6] AIR-TEC System: Official Website, http://www.air-tec.it/index_materialitrasp_uk.html [7] Pan R., Wypych P.W. Pressure drop and slug velocity in low-velocity pneumatic conveying of bulk solids. Powder Technology 94 (1997) 123- 132. [8] Reppenhagen Jens, Schetzschen Arwed, Werther Joachim. Find the optimum cyclone size with respect to the fines in pneumatic conveying systems. Powder Technology 112 (2000) 251–255. [9] Guiney P., Pan R., Chambers J.A. Scale-up technology in low-velocity slug-flow pneumatic conveying. Powder Technology 122 (2002) 34–45. [10] Tsuji, Y. (2007). Multi-scale modeling of dense phase gas-particle flow. Chemical Engineering Science, 62(13), 3410–3418. [11] Takei, M., Ochi, M., Saito, Y., & Horii, K. (2006). Extraction of particle concentration distribution from plug flow CT images using 3D wavelet multi resolution. International Journal of Wavelets Multi resolution and Information Processing, 4(2), 239–252. [12] Takei, M., Ochi, M., & Saito, Y. (2004). Image extraction of particle concentration at the plug front using 3D wavelets and comparison with LDV. Powder Technology, 142(1), 70–78. [13] Hirota, M., Sogo, Y., Marutani, T., & Suzuki, M. (2002). Effect of mechanical properties of powder on pneumatic conveying in inclined pipe. Powder Technology, 122(2–3), 150–155. [14] Futamura, M. (2005). Pressure drop and scale-up design of the plug type pneumatic conveying lines. Powder Handling and Processing, 17(1), 12–17. [15] Li, H.,&Tomita,Y. (2000). Particle velocity and concentration characteristics in a horizontal dilute swirling flow pneumatic conveying. Powder Technology,107(1–2), 144–152. [16] Li, H.,&Tomita,Y. (2002). Measurements of particle velocity and concentration for dilute swirling gas-solid

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flow in a vertical pipe. Particulate Science & Technology: An International Journal, 20(1), 1–13. [17] Li, H. (2000). Characteristics of a horizontal swirling flow pneumatic conveying with a curved pipe. Particulate Science & Technology: An International Journal, 18(3), 187–198. [18] Li, H. (2002). Application ofwavelet multi-resolution analysis to pressure fluctuations of gas-solid twophase flow in a horizontal pipe. Powder Technology, 125(1), 61–73. [19] Tanoue, K.-I., Tanaka, H., Kitano, H., & Masuda, H. (2001). Numerical simulation of tribo-electrification of particles in a gas-solids two-phase flow. Powder Technology, 118(1–2), 121–129. [20] Watano, S., Saito, S., & Suzuki, T. (2003). Numerical simulation of electrostatic charge in powder pneumatic conveying process. Powder Technology, 135/136, 112–117. [21] Watano, S. (2006). Mechanism and control of electrification in pneumatic conveying of powders. Chemical Engineering Science, 61(7), 2271–2278. [22] Konami, M., Tanaka, S., & Matsumoto, K. (2002). Attrition of granules during repeated pneumatic transport. Powder Technology, 125(1), 82–88. [23] Kobayashi, T. (2005). Pneumatic conveying for snow storage plants. Particulate Science and Technology, 23(1), 93–98. [24] Mills David. Pneumatic Conveying Design Guide. Elsevier Butterworth-Heinemann, Burlington. 2004.

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