Title of Invention

AN IMPROVED DUST-GAS SEPARATOR

Abstract

An improved dry solid gas separator which comprises a chamber (18) having an inlet port (19) at one end for passing dust laden gas to be purified and an outlet (20) at the other end for removing the collected dust, characterised in that the chamber being provided with an opening (22) at the said other end, the said opening (22) being an extension of a top open central pipe (21), for removing purified gas, the said, chamber (18) being provided with an insert (13, 14, 15, 16, 17) placed concentrically above the said central pipe (21), the said insert consisting of a conical central core (13) with its apex pointing towards the dust laden gas entry port (19) provided with a matching reversely oriented conical cap (14) at the opposite end, a pair of helical vanes (15) having maximum width (16) at the said end near the gas entry port (19) and minimum width (17) at the opposite end towards the said gas exit port (20), the said helical vanes (15) being joined to the said conical central port (13) in a diametrically opposite manner

Full Text

This invention relates to an improved dust gas separator. The present invention particularly relates to a dry solid gas separator of centrifugal type. The device of the present invention is a variable swirl dust separator which imparts necessary rotary motion to dust laden gas stream at different velocity at different stage while being passed along the equipment inside a chamber. The device of the present invention is useful for dry solid-gas separation. This equipment may be used to clean dust laden industrial gas or atmosphere effectively by separating the dust particles contained in it. The equipment may be useful in various plants such as ceramic, cement, boiler, steel, etc where the flue gas contains dust particles. The device of the present invention is useful mainly in the pollution abatement section by separating and thereby controlling the dust emissions in industrial gaseous effluents. Two types of commercial centrifugal separators, commonly known as cyclones,have so far been developed. They are reverse flow and straight through cyclones. In Fig 1 of the drawings accompanying this specification, a reverse flow cyclone is depicted wherein there is tangential entry of the gas stream through an inlet port (1) with velocity not less than 15 m/sec which imparts the necessary spinning motion to the dusts in the gas inside the cylinder (2) with a conical bottom (3). The dusts in the gas are thrown radially to the inside wall of cylinder (2) and fall to the cone (3) and finally exit through dust outlet port (4) . There is an open pipe (5) at the top closed end of the cylinder (2) . The clean gas exits through outlet port (5) . The pressure drop across the cyclone is above 5.0 cm water gauge (WG). In reverse flow cyclone because of tangential entry of gas at high velocity, the pressure drop in the cyclone is at least 5.0 cm WG. In the straight through cyclone as shown in Fig 2 of the drawings accompanying this specification, the gas stream enters axially through the inlet port (6) of the cylinder (7). An insert (8) with impeller type vanes (9) fitted on it and with conical downstream head (10) is inside the cylinder (7). The vanes impart swirling motion to the gas. From the swirling gas,the dusts are thrown to the wall of the cyclinder and exit through a radial opening (11) along with a small amount of purge gas. The clean gas exits through exit pipe (12) . The pressure drop of the cyclone is around 2.5 cm WG. Both reverse flow and straight through cyclones which are commercially available have a major drawback of pressure drop resulting in higher consumption of energy. In straight through cyclone the pressure drop is around 2.5 cm WG. But this cyclone, requires another cyclone attachement at the dust laden purge gas exit to collect the dusts. As such the straight through cyclone in conjunction with an additional cyclone will have high pressure drop, much more than 2.5 cm WG. The main object of the present invention is to provide an improved dry solid gas separator which obviates the drawbacks of the hitherto known prior art devices. Another object is to provide a device having high dust collection efficiency which would incur a lesser energy input (pressure drop) in comparison to the conventional cyclone type dry solid gas separator explained above. The device of the present invention is depicted in Figs 3 A & 3B of the drawings accompanying this specification Fig 3A shows the schematic of the swirl dust separator insert and Fig 3B shows the device complete with chamber. Accordingly, the present invention provides an improved dust- gas separator which comprises a chamber (18) having an inlet port (19) at one end for passing dust laden gas to be purified and an outlet (20) at the other end for removing the collected dust, characterised in that the said chamber being provided with an opening (22) at the said other end, the said opening (22) being an extension of a top open central pipe (21), the said chamber (18) being provided with an insert (13, 14, 15, 16, 17) placed concentrically above the said central pipe (21), the said insert consisting of a conical central core (13) with its apex pointing towards the said dust laden gas entry port (19) provided with a matching reversely oriented conical cap (14) at the opposite end, a pair of helical vanes (15) having maximum width (16) at the said end near the gas entry port (19) and minimum width (17) at the opposite end towards the said gas exit port (20), the said helical vanes (15) being joined to the said conical central core (13) in a diametrically opposite manner. The width of the vane is variable and is maximum at the top (near the gas entry port) of the equipment where the core diameter is zero. It is minimum at the other end where the gas leaves the insert and the core diameter is maximum. In this way, the gas stream spin velocity is forced to carry to reach the maximum at the bottom end of the central core. A number of design systems have been developed with height excluding the conical cap and width in the range 15-30 cm and 10-20 cm respectively. The extreme area reduction ratio of the insert is also carried from 0.25-0.75 by altering the variable vane width. The device of the present nature is to be operated for separating dry solid dust particles, the size of which may vary from 1-70 micron, from gas stream. Most of the dust particles present in the gas are forced to concentrate towards the periphery of the device on the inner wall of the chamber while moving along the vanes and fall through the annular space between chamber and central to the - -bottom of chamber by gravitational action for collection of dusts giving a collection efficiency of at least 78% with a pressure drop of only 1.8 cm WG, manufacturing cost being not higher than the existing related systems. As shown in Fig 3B, the gas stream enters axially into the closed chamber (18) through the inlet port (19) at the top. The device (13,14,15,16,17) fixed in the closed chamber (18) above the central pipe (21) with its axis vertical serves dual purpose Firstly, it imparts the spinning motion to the gaseous stream. Secondly, due to the construction of the device as shown in Fig 3A, the width of the helical vane structure (15) along the wall of a conical central core (13) is maximum at one end (16) and is minimum at other end (17) . Therefore the spinning velocity is minimum at the staring line (16) of the device and is maximum at the end of the vane structure (17) . A reverse oriented matching cap (14) is joined with the central core. Such a construction helps to separate the coarse particles towards the initial stage of spinning motion and the finer particles towards the end, maintaining the pressure drop as low as 1.8 cm WG. The concentrated dusts at the periphery of the device in its motion with the gas stream, fall along the inner wall of the chamber through the annular space between chamber and cenral pipe (21) by gravitational action to get passed out of the closed chamber through the bottom outlet (20) . The relatively clean gas passes out of the closed chamber through the open central pipe (21) connected to the outlet port (22). The working of the device of the present invention is illustrated below which should not be construed to limit the scope of the invention. An embodiment of the device, variable swirl dust separator of the present invention has been fabricated with a typical dimension of 22.5 cm height and 14.5 cm width. Performance has been measured from a number of experimental runs at different conditions . The gas stream flow rates is varied in the range of 100-300 Nm3hr while the dust concentration was in the range 1.0-5.0 gm/Nm3. Four sample runs with different parameters including the gas flow rate and dust concentration at the input of the device, the ratio of cross sectional area available for gas movement at the bottom (towards purified gas exit side) of the insert to that at the top (towards the dust laden gas entry side) of the insert (i.e area reduction ratio of the insert, the ratio of cross sectional area of the clean gas outlet central pipe to that of dust laden gas inlet of the chamber (i.e area reduction ratio of the separator), percentage separation of dust on weight basis by the device and incurred pressure drop. The result are shown in Table 1 below : Table 1 (Table Removed) Table 2 shows the grain size distribution of the dust particle at the input of the device on which the specified sample runs have been taken. Table 2 (Table Removed) The novelty of the device of the present invention is in the combination of the variable vane gradually decreasing from upper extreme to the lower extreme and the concentrically placed top open central pipe. The gas stream velocity at the top end of the device is lower in comparison to that at the lower end. With gradual increase in spining velocity, relatively finer particles tend to get separated at the periphery towards the lower end while the coarse particles are already separated at the upper end. This method of separating particles under dry system reduces the pressure drop in comparison to a conventional cyclones of either reverse flow type or straight through type provided through out remains same. The pressure drop in the device of the present invention as obtained experimentally is as low as 1.0 cm WG in comparision to the existing devices which at best are as low as 2.5 cm WG. We Claim: 1. An improved dust - gas separator which comprises a chamber (18) having an inlet port (19) at one end for passing dust laden gas to be purified and an outlet (20) at the other end for removing the collected dust, characterised in that the said chamber being provided with an opening (22) at the said other end, the said opening (22) being an extension of a top open central pipe (21), the said chamber (18) being provided with an insert (13, 14, 15, 16, 17) placed concentrically above the said central pipe (21), the said insert consisting of a conical central core (13) with its apex pointing towards the said dust laden gas entry port (19) provided with a matching reversely oriented conical cap (14) at the opposite end, a pair of helical vanes (15) having maximum width (16) at the said end near the gas entry port (19) and minimum width (17) at the opposite end towards the said gas exit core (20), the said helical vanes (15) being joined to the said conical central core (13) in a diametrically opposite manner. 2. An improved dust - gas separator substantially as herein described with reference to the examples and with reference to figures 3A and 3B of the drawings accompanying the specification.

Documents:

497-del-1998-abstract.pdf

497-del-1998-claims.pdf

497-del-1998-correspondence-others.pdf

497-del-1998-correspondence-po.pdf

497-del-1998-description (complete).pdf

497-del-1998-drawings.pdf

497-del-1998-form-1.pdf

497-del-1998-form-19.pdf

497-del-1998-form-2.pdf