FIELD OF INVENTION:

The present invention relates to a Gas Induction Reactor / Agitator, and more particularly to a novel impeller to be used in the Gas Induction Reactor.

BACKGORUND & PRIOR ART:

The Gas Induction Agitators are commonly used in process industry for inducing gas into the liquid for reactions. Typically, the agitator has a motor at the top nozzle, an impeller (or a set of impellers) joined to the shaft which effects a rotational motion. For operational purpose, the gas is pumped into the vapour space above the liquid level or sparged through dip tubes or spargers in the reaction mass.

In gas induction agitator designs the shaft is hollow and slots are made on the shaft in the vapour space. The gas induction impeller is also hollow and is connected to hollow shaft. The rotational motion of the agitator induces the flow of gas from the vapour space into the bulk liquid. The rate of gas induced is dependent on various parameters including impeller geometry, its location with respect to liquid height, speed of rotation etc.

US6250797 discloses an axial flow mixing impeller system for efficient mass transfer by control of size of the bubbles of the fluid which is being dispersed, especially gases and liquids with viscosities greater than the liquid into which dispersion occurs. This is obtained by creating passageways through the impeller blades for flow between the suction and pressure sides of the blades which disrupts the flow over the suction sides of the blades thereby reducing the tendency for bubbles to grow or coalesce into large bubbles which instead of being dispersed, rise to the surface without effective mass transfer to the liquid which is pumped by the impeller. The blades of the impeller may be slotted inwardly from the tips thereof to provide the passageways or may be formed from segments, gaps between which provide the flow passageways. The segmented blades have the advantage of enabling systems of large diameter impellers, of size approaching the diameter of the tanks or in closed tanks where access is by way of a manway smaller than the impeller blade dimensions, to be assembled within the tank, either upon initial installation or for replacement or retrofit. If the system is not used for gas or liquid dispersion, the segments may be in edge-to-edge abutment. Gas-to-liquid dispersion may also be improved by sparging below the impeller at the bottom of the tank and between the impellers in the tank, as with sparge rings of diameter less than the diameter of the impellers enabling gas supply at different pressures commensurate with the depth of the sparge rings, sufficient to overcome the head at the depth of the sparge ring.

Gas Induction agitators available in market are limited by the rate of gas induced and the efficiency of transfer of gas into the liquid mass in an energy efficient manner. SUMMARY OF INVENTION:

It is an object of the invention to provide an optimum and uniform gas-liquid mixing in the agitator.

In an aspect, the present invention discloses an impeller having novel geometry. The impeller comprises of a hub; an Inner cone; a top profile; a bottom profile and plurality of blades. The inner cone is provided with 45 degree downward pitch angle to obtain uniform gas distribution and certain flow pattern. The hub is provided with plurality of openings, whereas the inner cone is provided with the plurality of slots. The openings and slots are arranged in line to produce the optimized efficiency.

The said gas induction impeller is made up of any steel alloy. In a preferred embodiment, the impeller is glass lined which is suitable process fluid.

In another aspect, the impeller is designed with an advantageous geometrical shape. The angle of impeller blade with respect to the axis, determines the pumping efficiency of the said impeller.

BRIEF DESCRIPTION OF DRAWINGS:

Figure 1 illustrates a Gas Induction Reactor (1) in which an impeller of the present invention is to be employed. Figure 2 illustrates the bearing housing assembly (2)

Figure 3 illustrates the drive shaft assembly (3)

Figure 4 illustrates the extension shaft assembly (4)

Figure 5 illustrates the details of gas induction impeller (5) of the present invention

Figure 6 illustrates the comparative data of various impeller as compared with the impellers known in the art.

DETAILED DESCRIPTION:

The present invention may be understood by referring to figures appended at the end of the description.

Figure 1 illustrates a Gas Induction Reactor in which gas induction impeller (5) of the present invention is deployed. The Gas Induction Reactor comprises of a vessel body (1), an electric motor (M); a gear reducer assembly (G), a bearing housing assembly (2); a pedestal (6), a drive shaft assembly (3), an extension shaft assembly (4), a gas induction impeller (5), and a sealing component (7). The sealing component may be selected from a stuffing box, a mechanical seal or a magnetic seal. In a preferred embodiment, the stuffing box is chosen as a sealing component. The Electric motor (M) is directly coupled to the gear reducer assembly (G). A gear reducer assembly (G) is further coupled to the Bearing housing assembly (2), whereas the Bearing housing assembly (2) is coupled to the pedestal (6) which is mounted on the Gas Induction reactor (1).

Figure 2 illustrates the Bearing housing assembly (2) which comprises of a bearing housing body (2.1); plurality of Bearings (2.2) and a sealing cover (2.3). The major function of the bearing housing assembly (2) is to accommodate Static and Dynamic force transmitted on the Drive shaft (3) due to forces acting on the extension shaft (4).

Figure 3 illustrates a drive shaft assembly (3) comprising a drive shaft (3.1) and a locking means (3.2). The locking means (3.2) is preferably a locknut.

Figure 4 illustrates the extension shaft which comprises of a solid bar (4.1); a hollow pipe (4.2); a taper coupling (4.3); a locking plate (4.4). The Taper coupling (4.3) is joined to the drive shaft (3.1). The Solid shaft (4.1) and the Hollow pipe (4.2) are welded to the taper coupling (4.3) by means of a locking plate (4.4). The Holes (4.5) or the slots (4.5a) are fabricated on the hollow pipe (4.2). The factors, such as size of the holes (4.5) / slots (4.5. a) and total number of holes (4.5) / slots (4.5. a), are derived based on empirical data and engineering calculations. The function of these holes (4.5) / slots (4.5. a) are to provide a path for air / gas; which is sucked by the gas induction impeller (5). The said holes (4.5) / slots (4.5. a) are either in the perpendicular direction to the central axis of the extension shaft (4) or tangential to the central axis of the extension shaft (4).

The extension shaft (4) comprises plurality of slots (4.6), positioned according to the position of the Gas impeller (5). The significance of the said slots (4.6) is to provide a path to transfer the sucked air / gas to the Impeller with the help of the holes (4.5) / slots (4.5. a), positioned at the top of the impeller. The said slots (4.6) are positioned in the tangential direction to the central axis of the extension shaft

(4)·

Figure 5 illustrates the impeller (5) which is the subject of the present invention. The impeller (5) is immersed in liquid. Said impeller essentially comprises of a hub (5.1); an inner cone (5.2); a top profile (5.3); a bottom profile (5.4) and plurality of blades (5.5). In a preferred embodiment, the blades (5.5) are hollow. The hub (5.1) is coupled to the hollow pipe (4.2), wherein the hollow pipe (4.2), as described earlier, is provided with plurality of slots (4.6) at the holes (4.5) at the top portion for entry of a gas. The hub (5.1) is provided with plurality of openings (5.1. a) at a point of coupling to the hollow pipe (4.2), such that the gas entering from the holes (4.5) at the top portion of the hollow pipe (4.2) flows through the hub (5.1) and subsequently enters into the impeller blades (5.5) through the inner cone (5.2). The inner cone (5.2) comprises of plurality of slots (5.2. a) with respect to the hub slots (5.1.a). The inner cone slots (5.2. a) are tangential to the central axis of the extension shaft (4.2). The openings (5.1. a), which are provided at hub (5.1), and slots (5.2. a), which are provided at inner cone (5.2), are arranged in line to get the optimized result based on trials and analysis.

In an embodiment, the impeller (5) is prepared with any grade of alloy steel. In a preferred embodiment, the impeller (5) is made of Glass Lined steel material.

The impeller geometry, with reference to Figure 5, is explained as follows:

Plurality slots (5.1. a) are created on the hub (5.1) by determining the centre line of hub (5.1). Size of slots (5.1.a) is determined with the help of empirical database and certain engineering calculations. The Top profile (5.3) and the Bottom profile (5.4) is designed based on the process engineering fundamentals and analysis carried out. The role of Top profile (5.3) and Bottom profile (5.4) is to assure required flow pattern generation for mixing, uniform gas distribution and more gas hold up / prevent gas leakage in the process. To achieve these requirements, large engineering calculations are carried out. The Bottom Profile (5.4) is welded with the hub (5.1) by determining the width of impeller and equal distance provided to both end. The inner cone (5.2) is established on the bottom profile (5.4) and is provided with plurality of slots (5.2. a) in the tangential direction to the central axis of the hollow pipe (4.2). The slots (5.1. a) made on hub (5.1) and the slots (5.2. a) made on inner cone (5.2) are parallel to each other. The inner cone (5.2) is provided with 45 degree downward pitch angle to obtain uniform gas distribution and certain flow pattern. The impeller blades (5.5) are attached with the inner cone (5.2). The impeller blades (5.5) are also arranged at 45 degree downward pitch angle. An opening (5.6) is provided at the end of impeller blades (5.5). The size of opening (5.6) is determined with the empirical database and engineering calculations. The Top profile (5.3) is welded with the hub (5.1) and the impeller blades (5.5).

The impeller (5), having the geometry as explained before, is immersed in the liquid. The rotation of the impeller (5) results into the pressure differential Pd. At a critical rotation speed Rc or above, the said differential pressure is enough to overcome the overall pressure P, such that the gas flow is continued from the top portion (4.5) of the hollow pipe (4.2) to the impeller (5).

Figure 5 illustrates the comparative data of various impeller as compared with the impellers known in the art represents two data types which are being compared with Novel Impeller of the invention:

1. Filled Symbols represent performance of standard gas induction impeller at various superficial gas velocity.

2. Unfilled Symbols represent performance of standard agitator system without gas induction impeller at various superficial gas velocity.

The data points for both the above are been extracted from Ind Eng Chem. Res 1999,38,49-80 article “Design of Gas Inducing Reactors” by Ashwin W. Patwardhan and Jyeshtharaj B. Joshi. Advantageously, as can be seen from the data represented in Graph of Figure 6, the impeller (5) of the invention provides higher gas holdup at lower power per unit volume & higher superficial gas velocity thus results in higher mass transfer rate.

EXAMPLE:

Table 1

The data as presented in the Table 1 indicates value of gas hold up in % with respect to power per unit volume.

The relevant Graph, as illustrated in Fig. 5, represents two data types which are being compared with Novel Impeller of the invention:

1. Filled Symbols represent performance of standard gas induction impeller at various superficial gas velocity.

2. Unfilled Symbols represent performance of standard agitator system without gas induction impeller at various superficial gas velocity.

The data points for both the above are been extracted from Ind Eng Chem. Res 1999,38,49-80 article “Design of Gas Inducing Reactors” by Ashwin W. Patwardhan and Jyeshtharaj B. Joshi.