US3556489A

US3556489A - Wet type gas scrubber

Info

Publication number: US3556489A
Application number: US660342A
Authority: US
Inventors: Akiyoshi Ueda
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1966-08-15
Filing date: 1967-08-14
Publication date: 1971-01-19
Anticipated expiration: 1988-01-19
Also published as: AT279564B; DE1671413B1; GB1200641A

Abstract

A wet gas scrubber, wherein a mechanism for dividing a gas flow into two and for making the cross-sectional area of the gas flow paths variable is provided in a throat part and guides are provided respectively on the upstream side and downstream side of said mechanism so that the pressure loss may be reduced and further the relation between control variables of the variable cross-sectional area mechanism and the gas flow rate may be linearized. The guides are wedge-shaped with the broad ends at the variable mechanism. In one embodiment the variable mechanism comprises a rotor shaft extending transversely of the throat part and a rotor mounted on the shaft. The rotor has a rectangular longitudinal cross section and a transverse cross section which has a different length than width. The rotor has a transverse cross section bounded by a closed curve. In another embodiment the variable mechanism comprises a pair of spaced flexible and stretchable plate members extending along the inside portions of the throat parts. Plate moving elements are connected between the plate parts and are coupled to the plate members for bending the plate members outwardly into the throat parts. In still another embodiment the variable mechanism comprises two spaced sets of bulkhead plates extending along the inside portions of the throat parts. Each set including a first bulkhead plate having one end pivotally mounted on the venturi tube adjacent one gas flow guide and a second bulkhead plate slidably mounted adjacent the other gas flow guide and hingedly coupled to the first bulkhead plate. Plate moving members are connected between the sets of plates and are coupled to the sets of plates for moving the sets of bulkhead plates outwardly into the throat parts.

Description

United States Patent [72] Inventor Akiyoshi Ueda Kitakyushu, Japan [21] Appl. No. 660,342

[22] Filed Aug. 14, 1967 [45] Patented Jan. 19,1971

{73] Assignee Nippon Steel Corporation Tokyo,,lapan [32] Priority Aug. 15, 1966 [33] Japan [54] WET TYPE GAS SCRUBBER 6 Claims, 9 Drawing Figs.

52 user 261/62, 261/118. 138/46, l37/525,239/265.43

51 1m.c1 B0lf3/04, B01d47/10,B01d47/06 so FieldofSearch 261/115,

62, 52,44,118, V.S., VV, U.V., 11,12,13; 251/358. 334. 342. 60: 60/271; l38/44,45,46: 239/265.43', 137/525 [56] References Cited UNITED STATES PATENTS 1,045,613 11/1912 Roth 261/52 1,555,489 9/1925 Spencer et a1. 261/44 2,059,687 11/1936 Gagg 251/358X 2,424,654 7/1947 Gamble 261/V.S. 2,472,949 6/1949 Jacksonm. 138/45 2,797,904 7/1957 Voorheis 261/1 18X 2,905,543 9/1959 Schreter et al.. 48/180X 3,134,223 5/1964 Ball,Jr. 60/271X 3,284,064 1 1/1966 Kolm et a1. 261/62 3,350,076 10/1967 Crommelin, Jr

ABSTRACT: A wet gas scrubber, wherein a mechanism for dividing a gas flow into two and for making the cross-sectional area of the gas flow paths variable is provided in a throat part and guides are provided respectively on the upstream side and downstream side of said mechanism so that the pressure loss may be reduced and further the relation between control variables of the variable cross-sectional area mechanism and the gas flow rate may be linearized. The guides are wedge-shaped with the broad ends at the variable mechanism. In one embodiment the variable mechanism comprises a rotor shaft extending transversely of the throat part and a rotor mounted on the shaft. The rotor has a rectangular longitudinal cross section and a transverse cross section which has a different length than width. The rotor has a transverse cross section bounded by a closed curve. In another embodiment the variable mechanism comprises a pair of spaced flexible and stretchable plate members extending along the inside portions of the throat parts. Plate moving elements are connected between the plate parts and are coupled to the plate members for bending the plate members outwardly into the throat parts. In still another embodiment the variable mechanism comprises two spaced sets of bulkhead plates extending along the inside portions of the throat parts. Each set including a first bulkhead plate having one end pivotally mounted on the venturi tube adjacent one gas flow guide and a second bulkhead plate slidably mounted adjacent the other gas flow guide and hingedly coupled to the first bulkhead plate. Plate moving members are connected between the sets of plates and are coupled to the sets of plates for moving the sets of bulkhead plates outwardly into the throat parts.

FIG.2

FIG.

INVENTOR Ak/yosh/ Ueda wa r PATENTEU m1 9 I97! 3553489 SHEET 2 OF 4 INVETOR Akl'yoshi Ueda I Q Mat/441% 2m PATENTEDEJAN 1 9 m7:

SHEET 3 OF 4 IN VENTOR Ak/yoshi Ueda PATENTEDJANWQ?! 3556.489

SHEET 4 BF 4 INVENTOR Akiyosh/ Ueda BY v w y/M WET TYPE GAS SCRUBBER This invention relates to improvements in venturi-type gas scrubber.

In venturi-type gas scrubber, there are already known various methods whereby the cross-sectional area of the throat part can be varied in response to operating conditions. That is to say, a controlling equipment for varying cross-sectional area is provided in the throat part of a scrubber so that the gas flow rate passing through the throat part may be varied. In such method, unnecessary vortex and separation of boundary layer will be produced in the gas flow after the throat part. and the recovery of the pressure loss to be obtained in the diffusing part, that is, the portion to be regained by converting the dynamic pressure to a static pressure will be entirely lost. Further, as the relation between the gas flow rate and the control variable is not of a linear function, the controlling of gas flow rate by means of an actuator of the conventional controlling device can not cover the entire actuating span, but can be carried out only in a limited narrow range each time, while dividing the entire span to several such narrow ranges.

Therefore, as compared with the present invention such conventional method had various disadvantages such as an increase in gas pressure loss, power and size up of blowers or a reduction in gas pressure after passing through the scrubber, resulting in increases of various equipment costs and operat ing costs. Further, even the gas flow rate had to be controlled by partially linearizing the nonlinear characteristics of the actuator.

The present invention is a venturi-type gas scrubber wherein, for example. a rotatable rotor or a variable-shape diaphragm formed of a material high in the elongation percentage and elasticity or a variable-shape bulkhead plate having a rotating joint and a sliding joint to vary the cross-sectional area of the gas flow path is provided in a substantially intermediate part of the gas flow path in a throat part so that the gas passing through the throat part may be divided into two paths and the gas flow rate may be variable and an introducing part is formed in the contracting part of the gas flow 1 path arranged on the upstream side of the throat part and a pressure recovering part is formed in the diffusing part of the gas flow path arranged on the downstream side of the throat part. It is one of the features that, with the introducing part and the pressure recovering part the gas flow path is divided into two and the greater part of the variable cross-sectional area mechanism is enclosed so that the gas will not collide directly with the variable cross-sectional area mechanism in the throat part and unnecessary vortexes and separation of boundary layer produced in the gas flow paths can be prevented. Further, when the shapes of the parts of the variable crosssectional area mechanism inserted in the throat part to vary the cross-sectional area of the flow paths are made proper, the relation between the gas flow rate through the paths and the control variable (such as, for instance, in the case of the rotor a rotating angle of the axis) of said mechanism may be made close to a linear function over a wide range, whereby the characteristics of the actuating part for the controlling equipment can be made excellent. Further, according to the present invention a high dust collecting efficiency can be obtained even with the varying gas flow rate.

As described above, in the present invention a variable cross sectional area mechanism is inserted in the throat part of the gas scrubber so that the cross-sectional area of the gas passage can be varied in response to the varying gas flow rate and further a gas introducing part and a pressure recovering part are formed as follows: That is, guide plates are provided respectively on the upstream side and downstream side of the variable cross-sectional area mechanism so as to divide the gas path in two. By such formation, in the throat part a conversion from a static pressure of gas to a dynamic pressure and in the pressure recovering part a conversion from the dynamic pressure to the static pressure can effectively be performed, and the pressure loss of the entire equipment can be reduced. Further, by selecting properly the form of the curve made on the outer periphery of the variable bulkhead plate part in contact with the gas, the relationship between the gas flow rate and the control variable of the cross-sectional area mechanism can be linearized in a wide range. Therefore. it can be used effectively as an actuating part for the controlling device over a wide range of the input amount (control variables) in said mechanism. 1

An object of the present invention is toprovide a wet gas scrubber in which the pressure loss is small and a high dust collecting efficiency can be obtained.

Another object of the present invention is to provide a wet gas scrubber in which the cross-sectional area of the gas passage can be varied in response to the changes of the gas flow rate and which has excellent characteristics as an actuating part for the controlling device.

Other objects will become clear from the following explanation and accompanying drawings.

FIG. 1 is a vertically sectioned view of an embodiment of the present invention in which a rotor is applied for the variable cross-sectional area mechanism in a venturi-type gas scrubber.

FIG. 2 is a sectioned view on line 1-1 in FIG. 1.

FIG. 3 is a sectional view of a variable cross-sectional area mechanism formed mostly of a material capable of high elongation and having high elasticity.

FIG. 4 is an enlarged view of a part of FIG. 3.

FIG. 5 is a sectional view of a variable cross-sectional area mechanism formed of variable-shape bulkhead plates having a rotating joint and a sliding joint.

FIG. 6 is a schematic view of an embodiment of the present invention wherein a rotor is used for the variable cross-sectional area mechanism.

FIG. 7 is a schematic view illustrating the case of removing the guide plates in the contracting part and the diffusing part occupying a part of the present invention shown in FIG. 6.

FIG. 8 is a graph in which the distance from the inlet of a venturi scrubber is taken on the abscissa and the static pres sure at each point in the direction of the flow of the venturi scrubber is taken on the ordinate.

FIG. 9 is a graph in which the abscissa is the same as in FIG. 8 and the velocity at each point in the direction of the flow of the venturi scrubber is taken on the ordinate. In FIGS. 8 and 9, the static pressure and velocity at each point in the case of FIG. 6 are indicated with solid lines and the static pressure and velocity at each point in the case of FIG. 7 are indicated with dotted lines for comparison.

The details of the present invention shall be explained with reference to the drawings.

FIGS. 1 and 2 show an equipment of the present invention in a venturi-type gas scrubber wherein a rotor is applied to the variable cross-sectional area mechanism. The inside of an outer wall 2 and the outer periphery of a wedge-shaped guide 1 form two-divided contracting parts A and P of the flow path as introducing parts into a scrubber for raw gas. The inside of an outer wall 5 and the outside of a rotor 3 form throat parts B and Q. The inside of an outer wall 7 and the outside of a wedge-shaped guide 6 form two-divided diffusing parts C and The raw gas will gradually increase its velocity while passing through the contracting parts A and P and will proceed to the throat parts B and Q. When the gas passes through the narrowest parts between the projecting end parts of the rotor 3 and the inside of the outer wall 5 in the throat parts B and Q, the gas velocity will reach a maximum value.

An example of the rotor 3 to be used in this embodiment as shown in FIG. 2 is a rectangular column which has such a right cross-sectional area as the area enclosed by any closed curves and in which the ratio of the length to the width of the cross section is different. Therefore, by rotating a rotor axis 4 intersecting at right angles with the longitudinal axis of gas flow, the cross-sectional area of the throat pan can be made variable, the fluid resistance can be reduced and further the rela tion between the control variable and the gas flow rate can be made a linear function. A solid having a closed and curved surface can also be used instead of the above mentioned rectangular column.

Another embodiment of the variable cross-sectional area mechanism is shown in FIG. 3. A part of FIG. 3 as magnified is shown in FIG. 4. That is, a plurality ofliners 11 are attached to the gas side surface of a flexible plate 10 formed of a material which can be highly elongated and having a high elasticity so as to protect the flexible plate 10 so that a diaphragm of a variable shape can be formed by the variation of the clearance between the liners 11 in response to the elongation and contraction of the flexible plate 10.

The torque from a driving axle 17 is transmitted to a rod 14 through a pin 15 from a crank plate 16. As the rod 14 is fitted through a fitting seat plate 12 fixed to the flexible plate 10 and liners I1 and a pin 13, the positions of the flexible plate 10 and liners 11 are so determined that the torque acts to push out or pull back the flexible plate 10, liners 11 and fitting seat plate 12 as a whole, whereby a desired cross-sectional area of the throat parts B and Q can be obtained.

Thus, the cross-sectional area of the throat part can be made variable. At the same time, a guide plate 1 is provided in the upstream part to divide the gas current in two so that the gas will not collide directly with the variable cross-sectional area mechanism and a guide plate 6 is provided in the downstream part to recover the velocity obtained in the throat part again as a static pressure so that the pressure loss can be reduced.

The shape of each of the

guide plates

1 and 6 is not specified but is preferably wedge-shaped. Specifically, it is preferable that the guide plate 6 should have a length of about to 7 times as large as the width of the throat part B. Further, its apex angle a may be 6 to 13.

A third embodiment of the variable cross-sectional area mechanism is shown in FIG. 5.

That is to say,

bulkhead plates

19 and 20 having any crosssectional shapes are connected with each other at a rotating joint through a pin 21. The lower bulkhead plate 19 is connected so as to be rotatable around a fixed pin 18 and the upper bulkhead plate 20 is movable while sliding between guide 1 and a guide roller 22.

A seat plate 23 is fixed to the

bulkhead plate

20 or 19 so that the force finally pushing and pulling the bulkhead plate can be given to the seat plate 23. The positions of the

bulkhead plates

19 and 20 are so determined that a desired crosssectional area of the throat parts B and Q can be obtained.

The torque from the driving axle 17 is also transmitted as described above.

The variable cross-sectional area mechanism is constructed as follows: The first bulkhead plate has at one end a rotary axis fixed to the side plate 7 and is connected at the other end in the form of a hinge with the second bulkhead plate through a rotary axis rotatable around the said rotary axis fixed to the side plate 7, the second bulkhead plate is connected at the other end with one end of the third bulkhead plate in the form of a hinge as described above, a plurality of bulkhead plates are thus connected in turn and the forward end of the final bulkhead plate is of any cross-sectional form so as to move, while sliding between the guide and a guide roller. By means of this construction as above mentioned the cross-sectional area can be made variable.

Further, when the rotating angle of the driving axis 17 and the

torque transmitting elements

12 and 16 of FIGS. 3 and 4 and 23 and 27 and

bulkhead plates

19 and 20 of FIG. 5 are properly selected, the relation between the control variable and the gas flow rate can be made to be a linear function.

Dust collecting water pumped by means of another apparatus is sprayed by spray nozzles 8 through a header 9 and is injected into the parts B and Q. In the case of handling a large flow rate of gas, in order to inject the spray into the entire throat part, a spraying assembly may be provided, for example, inside the rotor. In the diffusing parts C and R, the raw gas and the spray droplets injected in the throat parts B and Q mix together and the dust in the raw gas is absorbed by the actions of contact, collision and diffusion. Then, in the turning part of the gas flow (not illustrated) provided after the gas scrubber, the water droplets containing dust are separated from the gas and the raw gas is cleaned. At the same time, the gas velocity gradually decreases and the dynamic pressure of the high velocity gas in the narrowest part is effectively recovered as a static pressure. For the change of the gas flow rate to be treated, the clearances in the narrowest parts in the throat pans B and Q of the present gas scrubber are varied so that the gas passing cross-sectional area of the narrowest parts can correspond to the respective gas flow rates. Further, by making the gas velocity in the narrowest part constant, the pressure loss and dust collecting efficiency can be kept constant.

A further important advantage attributable to the construction of the equipment of the present invention will be made clear from the comparison of FIG. 6 showing a graph of a variable cross-sectional area mechanism, which is provided with the

guide plates

1 and 6, with FIG. 7 showing also a graph of the variable cross-sectional area mechanism, in which however, the guide plates are removed. when comparing both FIGS. 6 and 7 in view of FIGS. 8 and 9 showing graphs, in which the velocity and static pressure are taken on the respective ordinates and the distance from the inlet of the venturi scrubber is taken on the abscissa, it is found that, when producing the same the gas velocity V in the throat part 1 which constitutes one of the most important factors in determining the dust collecting efficiency, for both cases of FIGS. 6 and 7, the following differences are seen between them:

I. In the case of FIG. 7, between 1 and as the gas velocity suddenly changes from V to V and the gas flow collides directly with the rotor 3, the loss of the static pressure at 1 will be considered to be P P I 2. Though the gas velocity is the same V =V 1 the static pressure used until then will be P P Therefore, until 1 the difference P P3 of the static'pressure loss will be already produced between the cases of F I68. 6 and 7.

3. The lowest static pressure will be reached atI Here, too, due to the influence from 1 to I in the upstream part, that is, due to the above mentioned points 1. and 2., there will be a difference P P between the static pressures of both and P P 4. In the case of FIG. 7, between I and the vortexes and separation of boundary layer are produced on the downstream side of the rotor and the static pressure P, including the static pressure portion used already as a dynamic pressure will be lost and only P P will be recovered as a static pressure.

5. On the other hand, in the case of FIG. 6, the vortexes and separation of boundary layer are only slightly produced on the downstream side and, as the guide plate 6 is provided to gradually reduce the velocity from V to V between 1 and I there will be only a slight loss and the static pressure I, including the static pressure portion already used as a dynamic pressure will be effectively recovered to P 6. That is to say, in comparing the static pressure recovered portion P,,P in FIG. 6 and the static pressure recovered portion P P in FIG. 7 between I, and 1 with each other, it will be found that, as P -,P P P and P P the pressure loss between [0d 16 will be P P As is evident from the above mentioned points I. to 6., an

advantage of the equipment of the present invention in power costs and equipment costs, which correspond just to the difference P P of the pressure loss, is obtained in the case of FIG. 6.

An example of the application of the gas scrubber of the present invention to a small-sized apparatus for recovering waste gas from a converter in an unburnt state shall be explained in the following:

For treating an exhaust gas, which fluctuated in amount to be treated from 0 to 1700 Nm3/l-I and had a temperature of 40 C., the internal pressure of the gas cooler was maintained at a certain value, while adjusting the amount to be sucked-in by means of the equipment of the present invention.

The adjustment of the internal pressure of the gas cooler was favorable. The results of the measurements of the respective amounts were as follows:

Test N 0. 1 2 3 Maximum exhaust gas volume in Nm /H 1, 500 1, 425 1, 250 Mean pressure loss in mm. of Water column 3 963 1, 175 Pressure loss in mm. of water column when the exhaust gas flow rate was maximum 720 780 1, 050 Amount of injected water in liters/Nrn tor the maximum exhaust gas flow rate 7 1. 4 2. 4 Dust collecting efiiciency in percent 98. 4 99. 2 99. 2 Amount of blown oxygen in Nm /H 42s 136 431 Thus favorable results were shown. 7

After the equipment was used without sweeping the respective parts for more than 8 months, the contamination degree of the respective parts with deposited dust was so slight as to have no influence on the functions of the respective parts of the present invention.

I claim:

1. A wet venturi type gas scrubber comprising a venturi tube having a throat part with a substantially rectangular cross-sectional area transversely of the axis of said venturi tube, a mechanism in said throat part dividing the gas flow path in the throat part into two parts, said mechanism being movable for changing the cross-sectional areas of the parts of the gas flow path, an upstream gas flow guide for dividing the gas flow path into two parts and positioned in said venturi tube on the upstream side of the throat part and the downstream end of said upstream flow guide covering the greater part of said movable mechanism, a downstream gas flow guide positioned in said venturi tube on the downstream side of said throat part for preventing vortexes from being produced in the gas flow, said downstream gas flow guide having the upstream end in con tact with said movable mechanism, and means connected to said throat part for injecting a liquid into the throat part.

2. A gas scrubber as claimed in claim 1 in which said gas flow guides are wedge-shaped with the broad ends at said movable mechanism.

3. A gas scrubber as claimed in claim 1 in which said movable mechanism comprising a rotor shaft extending transversely of the throat part, and a rotor mounted on said shaft, said rotor having a rectangular longitudinal cross section and having a transverse cross section which has a different length than width.

4. A gas scrubber as claimed in claim 3 in which said rotor has a transverse cross section bounded by a closed curve.

5. A gas scrubber as claimed in claim 1 in which said movable mechanism comprises a pair of spaced flexible and stretchable plate members extending along the inside portions of the throat parts, and plate moving means between said plate members and coupled to said plate members for bending the plate members outwardly into the throat parts.

6. A gas scrubber as claimed in claim 1 in which said movable mechanism comprises two spaced sets of bulkhead plates extending along the inside portions of the throat parts, each set including a first bulkhead plate having one end pivotally mounted on the venturi tube adjacent one gas flow guide, and

a second bulkhead plate slidably mounted adjacent the other gas flow guide and hingedly coupled to said first bulkhead 5 plate, and plate moving means between said sets of plates and coupled to said sets of plates for moving the sets of bulkhead plates outwardly into the throat parts.

Claims

1. A wet venturi type gas scrubber comprising a venturi tube having a throat part with a substantially rectangular crosssectional area transversely of the axis of said venturi tube, a mechanism in said throat part dividing the gas flow path in the throat part into two parts, said mechanism being movable for changing the cross-sectional areas of the parts of the gas flow path, an upstream gas flow guide for dividing the gas flow path into two parts and positioned in said venturi tube on the upstream side of the throat part and the downstream end of said upstream flow guide covering the greater part of said movable mechanism, a downstream gas flow guide positioned in said venturi tube on the downstream side of said throat part for preventing vortexes from being produced in the gas flow, said downstream gas flow guide having the upstream end in contact with said movable mechanism, and means connected to said throat part for injecting a liquid into the throat part.

6. A gas scrubber as claimed in claim 1 in which said movable mechanism comprises two spaced sets of bulkhead plates extending along the inside portions of the throat parts, each set including a first bulkhead plate having one end pivotally mounted on the venturi tube adjacent one gas flow guide, and a second bulkhead plate slidably mounted adjacent the other gas flow guide and hingedly coupled to said first bulkhead plate, and plate moving means between said sets of plates and coupled to said sets of plates for moving the sets of bulkhead plates outwardly into the throat parts.