Title of Invention | " AN IMPROVED INSTRUMENTATION SYSTEM FOR MEASUREMENT OF VELOCITY OF SOLID PARTICLES IN A TWO-PHASE GAS-SOLID FLOW THROUGH A PNEUMATIC CONVEYOR" |
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Abstract | The invention provides an improved instrumentation system for measurement of velocity of solid particles in a two-phase gas-solid flow through a pneumatic conveyor, comprising (i) tv/o sensors fitted at an adjustable distance from each other along the length of a tube of an electrical non-conducting material, used for conveying a mixture of a gas and solid particles at a given flow rate; (ii) two electronic amplifiers for amplifying the fluctuations in the electrostatic charge collected on said solid particles and picked by said tv/o sensors; (iii) an analog to digital (A/D) converter for converting the analog voltage output of each said electronic amplifier into corresponding 12-bit digital data; and (iv) a 406 based personal computer (PC) which is provided with a software programmed in C language, for calculating and displaying the velocity of the said solid particles flowing through said tube from the cross correlation function of the outputs of said two electronic amplifiers. The said sensors are of electrodynamic 'ring' or 'horn' types and the said electronic amplifiers are operational amplifiers of relatively simple design and construction, each having an integrated circuit and a low-pass filter. |
Full Text | The invention relates to an improved instrumentation system for measurement of velocity of solid particles in a two-phase gas-solid flow through a pneumatic conveyor. The invention relates more particularly to an instrumentation system for measurement of velocity of solid particles flowing in bulk in two-phase gas-solid flow through a pipe line made of electrical non-conductive material by detecting the electrostatic charge on the solid particles with two electrodynamic type of sensors and amplifying the charge by two electronic amplifiers, both the said sensors and amplifiers being designed and constructed for this purpose, along with the use of an Analog to Digital (A/D) converter for converting the analog output of the amplifiers into digital data and a personal computer (PC) with a software suitable for measuring the velocity of the solid particles instantly without using any indirect method as normally adopted in the prior art. An instrument system for measurement of velocity of materials in a two-phase flow has been disclosed in the pending Indian Patent Application No.481/Del/97, in which the sensor used is of capacitance type requiring incorporation of one each of a band pass amplifier, phase-sensitive detector and instrumentation amplifier, of relatively complex circuitry and construction, along with the use of an Analog to Digital (A/D) converter and a personal computer (PC). The main drawtback of the said Instrument system is that it is not found to be suitable for the measurement of velocity of solid particles in a two-phase gas-solid flow through a pneumatic conveyor. One object of the present Invention is to provide an instrument system based on the use of an electrodynamic sensor which is particularly suitable for measurement of solid particles moving in bulk in a two-phase gas-solid flow through a pneumatic conveyor and requires also an electronic amplifier of relatively simple design and construction for amplifying the output of the sensor. The other object is to provide a means for locating the blockage part of a pipe line of a pneumatic conveyor for gas and solid particles. The electrodynamic sensor designed and constructed for use in the invented instrument system is of two basic types, namely "Ring and 'Horn1. A ring type electrodynamic sensor is formed by fixing an inner ring of stainless steel strip on the outer surface of a perspex or flexi glass tube, wrapping the outer surface of inner ring with paper and fixing an outer ring of stainless steel strip of axial length somewhat larger than that of the inner ring on the said paper wrapping to act as an electrical shield of the inner ring. A horn type electrodynamic sensor is formed by fixing two inner arcuates of stainless steel strip on the outer surface of a flexi glass or perspex tube, the said strips being disposed diametrically opposite to each other and electrically connected together; wrapping the two inner arcuate strips with paper; and fixing on the paper wrapping an outer ring of stainless steel strip of axial length somewhat larger than that of each said inner arcuate strips to act as an electrical shield for the latter. The electrostatic charge accumulated on the solid particles moving through the flexi glass or perspex tube in the two phase gas-solid flow induces, a corresponding electrostatic charge in the said inner ring or said inner arcuates of an electrodynamic sensor. Fluctuations in the said induced charge are, as already stated, amplified by means of an electronic amplifier of relatively simple design and construction,made for the purpose. The ourput of the amplifier is fed through an A/D converter to a PC which is provided with a suitable software for determining the velocity of the solid particles. The invention is described fully and particularly in an unrestricted manner with reference to the accompanying drawings in which - Figure 1A is the cross sectional view of the ring type electrodynamic sensor; Figure 1B is the axial sectional view of the ring type electrodynamic sensor; Figure 2A is the cross sectional view of the horn type electrodynamic sensor; Figure 2B is the axial sectional view of the horn type electrodynamic sensor; Figure 3 is the schematic circuit diagram of the electronic amplifier; and Figure 4 is a sketch of the set up for direct measurement of velocity of solid particles flowing in a gas medium through a pipe line; Figure 5 shows graphically the agreement between the velocity (VI) measured by the instrumentation system and velocity(VD) obtained by direct measurement. Referring to Figs. 1A and 1B, the inner ring (14) of stainless steel strip is fixed on the outer surface of the flexi glass or perspex tube (13) by means of a known glue. The ring (14) is wrapped with paper (16) and the outer ring (15) of stainless steel strip is fixed on the outside surface of the paper wrapping (16) by means of the said glue. The axial length (Ls) of the outer ring (15) is made larger than the axial length (Le) of the inner ring (14) by one 1 ran on either end thereof. The outer ring (15) is connected to ground to act as an electrical shield for the inner ring (14). In a particular embodiment of the ring type electrodynamic sensor, the stainless steel strip is of thickness 0.04 ran, the axial length (Le) of the inner ring (14) is 10.0 mm, the axial length of the paper wrapping (16) and outer ring (15) each is 12.0 mm, with 1.0 mm of their axial lengths lying beyond the axial length of the inner ring (14) on either end thereof. The outside surface of the outer ring (15) is also wrapped with a layer of thick paper (not shown). The outside diameter (2R1) of the flexi glass or perspex tube (13) is 12.0 mm which is also the inside diameter of the inner ring (14). The inside diameter (2R2) of the flexi glass or perspex tube (13) is 10.0 mm and the inside diameter (2R3) of the outer ring (15) is 18.5 ram. Referring to Fig. 2, the construction of the horn type electrodynamic sensor is otherwise similar to that of the ring type sensor shown in Fig. 1, except that the inner ring (14) of ring type sensor is replaced by two arcuates (18A, 18B) of stainless steel strip, disposed diametrically opposite to each other, each subtending an angle (e) of preferably 120° at the axis of the sensor, the said arcuates being electrically connected to each other. A two-core shielded cable (17) is used to connect each type of sensor to an electronic amplifier designed and constructed for the purpose. Referring to Fig. 3, the electronic amplifier comprises an operational amplifier (IC)(20) which is capable of amplifying the fluctuations(Ve)inthe electrostatic charge q(t) accumulated at any instant (t) in the ring or horn type electrodynamic sensor (Figs, 1 and 2) during the movement of solid particles in a gas medium through a flexi glass or perpex pipe line and converting the same into a corresponding amplified voltage output (V6) which is connected to a PC (not shown) through an A/D converter card of type PCL-208 (not shown). The resistor (R) and capacitor (c) are connected in parallel across (IC)(20) to act as a low pass filter with a cut off frequency (fc), according to relationship (I) : (Equation Removed) The(IC)l20) therefore acts as a low pass amplifier of cut off frequency (fc). The values of R and C are chosen to vary the cut off frequency (fc) as required. Typical value of (R) is 1MΩ, that of (C) is 47pf and that of cut off frequency (fc) is 3386 HZ. The software used for the PC which is 486 based, comprises the said A/D card to convert the analog voltage outpu of the operational amplifier (20) into a 12-bit digital data and to transfer the same through a random access memory (RAM) of the PC to a Data file on hard disk for data, storage, by executing a program written in C language. The algorithm of the software uses the cross correlation function of the two signals (Vo) received from the two electrodynamic sensors disposed at two different locations, along the length of said pipe line conveying the solid particles in a gas medium for calculation and display of the velocity of the solid particles by the PC. Referring to Fig. 4, sand which is used as the solid particle is stored in bin (6) and compressed air used as the gas medium is supplied to flexible pipes (11A and 11B) from source (S). Perspex or flexi glass tube (P) which is fitted with two similar electroflynamic sensors (E1 and E2) is mounted vertically at the side of the bin (6) to act as the velocity measuring pipe. Another perspex or flexi glass tube (Q) is mounted vertically at the side of tube (P) to act as the sand collecting pipe. A collecting tank (12), mounted on a weighing machine (M) , is provided at the lower end (B2) of tube (Q) for collecting the sand flowing down the tube (Q). Bin (6) is a mild steel cylindrical vessel of preferred length 4 70 mm and diameter 250 mm in its upper cylindrical part, the lower conical part of which converges at an angle of 45° for allowing easy flow of the sand through it under the combined pressure of the compressed air supplied at its top through flexible pipe (11A1), throttle valve (1) and pressure regulator (4), and the action of gravity. The bin is provided with a removable top cover (C), throttle valve (1A) to allow bleeding of compressed air, a pressure gauge (10) and a sight glass (10A) to allow inspection of the sand level in the bin. The bottom end (B) of the conical section of the bin is connected to a mixer (T) through a quick-closing valve (7) and a relatively short connecting pipe (11A). Compressed air from source (S) is supplied to mixer (T) through throttle valve (2), flexible pipe (11B), rotameter (5), flexible pipe (11C), pressure tapping point (X,) for connection to manometer (MM1) and coupler (Y1). Throttle valve (3) is connected to Flexible pipe (11B) to allow bleeding of compressed air flowing through the same. A mixture of sand and air is formed in mixer (T), which is allowed to flow through couplet (Y2), flexible pipe (11D), union Joint (z), pressure tapping point (X2) for connection to manometer (PW2), quick-closing valve (8), tube (P), quick-closing valve (9), pressure tapping point (X^) for connection to manometer (MM3), flexible pipe (11E), coupler (Y3), Tube (Q), and to accumulate the sand in tank (12) connected to bottom end (B2) of tube (Q). The top end (B^) of tube (Q) is covered by a wire mesh (V) for allowing only the air to escape into the atmosphere and not the sand present in the said mixture of sand and air. Tube (P) is of length 848 mm, inside diameter 10.0 mm and outside diameter 12.0 mm. Two sensors (E1 and E2) mounted on tube (P) are separated from each other with a gap of 60.0 mm, the lower sensor (Ep) being located at a distance of 625.0 mm from valve (8). Tube (Q) is of length 1105 am, outside diameter 25.4 mm and inside diameter 23.4 mm. In carrying out the direct measurement of velocity of solid particles using the set-up shown in Pig.4, compressed air from source (S) is supplied to flexible pipes (11A and 11B) \at a pressure of 2-3 kg/cm2 . When a two-phase sand-air flow through tube (P) is established, two quick-closing valves (8 and 9) are clos€»d simultaneously by operating a common handle provided for them. The sand - air mixture is entrapped in tube (P) and sand (being heavier) settles down and is deposited at the bottom part (C2) of tube (P). The sand collected at the bottom part (C2) of tube (P) is removed by opening the union Joint (z) and flexible pipe (11D), and weighed to determine the weight (Ws) of the sand flowing through tube (P) at any instant under the steady flow condition of the sand-air mixture. The weight of sand flowing through tube (P) under the steady flow condition during a given time (TS) is determined from weight (Wg) of the sand collected in tank (12) during the time (TS) which is measured by a stop watch. The average rate (R) of the flow of sand through (P) is : (Equation Removed) The time (Tg) required for the flow of sand of weight (¥g) through tube (P) is :- (Equation Removed) The velocity (V) of sand flowing through tube (P) of length L is ; (Equation Removed) (IV) or, (Equation Removed) (V) from relation (III) or, (Equation Removed) (VI) from relation (II). So the average velocity of sand flowing in tube (P) is determined directly from relation (VI) by measuring L, ¥ , O T and WS in the method as described above, s Beside sand, the solid particle in the two-phase flow may be lime dust, coal dust and similar other material also. The values of velocity (V1) obtained by using the invented instrumentation system at different rates of airflow and air pressures on the sand (or lime dust) charged into bin (6) have been compared in Pig. 5, with the corresponding values of velocity (VD) determined by direct measurement in the method described hereinbefore. It is noted that the agreement between VI and VD is fairly close. The direct method of measurement of velocity of solid particles is time-consuming and not suitable for use under industrial conditions. The invented instrumentation system provides a ready and rapid means of determining the velocity of solid particles in a two-phase solid-gas flow through pipe lines under industrial conditions. We Claim :- 1. An improved instrumentation system for measurement of velocity of solid particles in a two-phase gas-solid flow through a pneumatic conveyor, comprising (i) two sensors (E1, E2) fitted at an adjustable distance from each other along the length of a tube (P) of an electrical non-conducting material, such as flexi glass or perspex, used for conveying a mixture of a gas, such as air, and solid particles such as sand, line dust and coal dust at a given flow rate; (ii) two electronic emplifiers for amplifying the fluctuations in the electrostatic charge collected on said solid particles and picked by said sensors; (iii) an analog to digital (A/D) converter of type PGL-208 for converting the analog voltage output of each said electronic amplifier into corresponding 12-bit digital data; and (iv) a 486 based personal computer (PC) which is provided with a software programmed in C language, for calculating and displaying the velocity of the said solid particles flowing through said tube from the cross correlation function of the outputs of said two electronic amplifiers,characterised in that the said sensors are of electrodynamic types, such as herein described, and the said electronic amplifiers are of relatively simple design and construction, such as herein described. 2. The system as claimed in claim 1, wherein the said electrodynamic sensor is of ring type having an inner ring (14) of stainless steel strip of thickness 0.04 mm and axial length 10.0 mm, fixed on the outer surface of a flexi glass or perspex tube (13) of outside diameter 12.0 mm and inside diameter 10.0 mm, being covered with a paper wrapping (16); and an outer ring (15) of stainless steel strip of thickness 0,04 mm and axial length 12.0 mm with 1.0 mm protruding beyond each axial end of the said inner ring, being connected to ground to act as an electrical shield of the inner ring and being wrapped with a layer of paper. 3. The system as claimed in Claims 1 and 2, wherein tie said electrodynamic sensor is of horn type, the construction of which is otherwise similar to that of the ring type electrodynamic sensor with the only difference that the inner ring of the ring type sensor is replaced by two arquates (18A, 18B) of stainless steel strip, which are disposed diametrically opposite to each other, subtending an angle of 120° each at the axis of the sensor, and being connected to each other electrically. 4. The system as claimed in any preceding claim, wherein the electronic amplifier comprises an operational amplifier of type 741 having an integrated circuit (20) and a low pass filter, formed by a resistor (R) and capacitor (C), of cut off frequency 3386 HZ, which is capable of amplifying the fluctuations in the electrostatic charge accumulated in the ring or horn type electrodynamic sensor during the movement of solid particles in a gas medium through the flexi glass or perspex tube to the extent required for converting the amplified analog output into corresponding 12-bit digital data by means of an A/D converter connected to a PC. |
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3004-del-1997-correspondence-others.pdf
3004-del-1997-correspondence-po.pdf
3004-del-1997-description (complete).pdf
Patent Number | 232035 | |||||||||||||||||||||||||||
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Indian Patent Application Number | 3004/DEL/1997 | |||||||||||||||||||||||||||
PG Journal Number | 13/2009 | |||||||||||||||||||||||||||
Publication Date | 27-Mar-2009 | |||||||||||||||||||||||||||
Grant Date | 15-Mar-2009 | |||||||||||||||||||||||||||
Date of Filing | 20-Oct-1997 | |||||||||||||||||||||||||||
Name of Patentee | STEEL AUTHORITY OF INDIA LTD. | |||||||||||||||||||||||||||
Applicant Address | IRON & STEEL ENTERPRISE, ISPAT BHAWAN,LODHI ROAD,NEW DELHI-110003,INDIA. | |||||||||||||||||||||||||||
Inventors:
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PCT International Classification Number | B65G 51/08 | |||||||||||||||||||||||||||
PCT International Application Number | N/A | |||||||||||||||||||||||||||
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