Flow change-over valve for the blowing of fluids into molten metal vessel

Disclosed herein is a flow change-over valve for the blowing of fluids into a molten metal vessel, which includes a housing provided with at least three inlet ports for different fluids and an outlet port, a valve body with a main passage communicating selectively between one of the inlet ports and the outlet port and rotatably supported in the housing to perform the changing-over of inlet passages. Among these inlet ports, an inlet port for purging fluid is opened in the housing, and a shroud-like gap surrounding the valve body is formed between the inner periphery of the housing and the outer periphery of the valve body in such a manner that it communicates with the inlet port for the purging fluid disposed in the housing and is always to be communicated with an opening of an inlet port of the main passage during the changing-over through the rotation of the valve body.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention: 
This invention relates to a flow change-over valve for the blowing of 
fluids into a molten metal vessel, and more particularly to a flow 
change-over valve which is advantageously used as a gas selecting valve 
when one of plural kinds of fluids (for instance, gaseous fluids 
containing powders which are unfavorable to be mixed with each other) is 
selectively blown into a bottom-blown converter with the change of times 
in the refining stage. 
(2) Description of the Prior Art: 
As a method of steel making and refining molten iron with a large amount of 
scrap in the bottom-blown converter, there has been proposed a technique 
in which a mixture of, for example, powdery coal and methane gas is blown 
into the converter through a part of bottom tuyeres and oxygen gas is 
simultaneously blown through the other remaining tuyeres to fuse the 
scrap, and after the inlet passage of the flow change-over valve is 
changed into another inlet passage, the resulting melt is refined by 
blowing oxygen gas containing powdery quicklime, etc. from such another 
inlet through the tuyeres used for the blowing of coal-containing methane 
gas as disclosed, for instance, in W. German Patent Application 
Publication No. 28 38 983 or Japanese Patent laid open No. 57-29,521. 
In this refining method, the kind of the fluids to be blown into the 
converter should be changed with the change of times in the refining 
stage, which requires the use of a flow change-over valve. As the flow 
change-over valve satisfying this requirement, there is proposed a flow 
change-over valve of the following structure in Japanese Patent laid open 
No. 56-33,415. This is, it relates to an apparatus for introducing both 
finely powdered carbon-containing fuel floating in a carrier gas and 
oxygen into a molten iron vessel, characterized in that a movable valve 
member is arranged in a housing comprising a fuel supply pipe, an oxygen 
supply pipe and a tuyere pipe, and the valve member opens into a fuel hole 
section or an oxygen hole section and is actuated by the oxygen pressure 
inside the supply pipes. 
In FIG. 1 is shown a vertical section view of the above apparatus (flow 
change-over valve), wherein numeral 2 is a movable valve member, numeral 4 
a sealing portion, numeral 6 a fixed valve member, and numeral 8 bellows. 
In this type of the flow change-over valve, however, when the movable 
valve member 2 is moved toward the sealing portion 4 for closing, there 
are fears that the powder enters therein and that the hermetric property 
is deteriorated in a long-term use to disable the reliable change-over 
between two gases. Further, when the inlet passage is changed into another 
one in the flow change-over valve, if it is intended to use two gases to 
be prevented from mixing with each other, for instance, methane gas 
containing powdery coal and oxygen gas, there is a possibility that the 
above two gases are mixed with each other in the interior of the flow 
change-over valve. In the latter case, there is a risk that the coal in 
the gas is burned by the mixing of both gases to overheat the flow 
change-over valve. Moreover, there is also a danger that the overheating 
causes the deformation and burning of the sealing portion, resulting in 
the deterioration of the sealing. In addition, the bellows are worn out 
with the blown powder to be bored, so that an explosion is caused through 
the mixing of the two gases. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the invention to eliminate the above 
drawbacks of the prior art and to provide a flow change-over valve which 
can surely prevent the mixing of two fluids and hold a gas pressure in an 
outlet passage at a given value during the changing-over of inlet passages 
for selecting an appropriate gas kind. 
It is another object of the invention to provide a flow change-over valve 
having such a structure that the biting of powder entrained in the gas is 
prevented between the valve body and the housing and a satisfactory 
hermetical property is held over a long period of time with an excellent 
durability. 
According to the invention, there is the provision of a flow change-over 
valve for the blowing of fluids into a molten metal vessel comprising a 
housing provided with at least three inlet ports for different fluids and 
an outlet port, a valve body provided therein with a main passage 
selectively communicating between a respective one of the inlet ports and 
the outlet port and rotatably supported in the housing to perform the 
changing-over of inlet passages, wherein an inlet port for purging fluid 
among the inlet ports is opened in the housing, and a shroud-like gap 
surrounding the valve body is formed between the inner periphery of the 
housing and the outer periphery of the valve body in such a manner that it 
communicates with the inlet port for the purging fluid disposed in the 
housing and is always to be communicated with an opening of an inlet port 
in the main passage during the changing-over through the rotation of the 
valve body. 
According to a modified embodiment of the invention, an inlet passage for 
the purging fluid is arranged in a lower extension portion of the valve 
body so as to communicate with the main passage of the valve body.

DETAILED DESCRIPTION OF THE INVENTION 
The invention will be described in detail with respect to an example of 
selectively blowing two fluids (powdery coal-containing methane 
gas.fwdarw.oxygen gas) into a bottom-blown converter from the bottom 
thereof with the change of times in the refining stage. 
The selective supply of the above two fluids to the converter is performed 
by the changing of inlet passages using a three-way flow change-over valve 
provided with three inlet ports, an outlet port and a single passage. In 
the changing of the inlet passage, it is necessary to prevent these two 
fluids from being mixed with each other as mentioned above. 
For this purpose, the flow change-over valve according to the invention is 
so constructed that when the inlet passage is changed into another one, a 
purging fluid is introduced into the main passage of the valve body to 
replace the fluid passing through the main passage of the valve body with 
the purging fluid. 
In FIGS. 2 and 3, numeral 12 is a housing with a space for supporting a 
valve body, which comprises a main housing body 14 and a housing cap 18 
fitted thereto by means of bolts and nuts 16. Numeral 20 is a packing 
gland connected to the housing cap 18 by means of bolts and nuts 16'. In 
the main housing body 14 are formed a first inlet port 22 and a second 
inlet port 24 for communicating the valve body-supporting space with the 
exterior, which ports are also connected to supply pipes for different 
gases A and B, respectively. Further, an outlet port 26 directing to the 
converter is formed in the housing 12 at a place perpendicular to the 
inlet ports 22 and 24. A spherical valve body 28 is hermetically fitted 
into the valve body-supporting space formed in the housing 12, and has 
upper and lower extension portions 30 and 32 in the axial direction of the 
outlet port 26, and is rotatably supported around the axis of the outlet 
port 26 through a gland packing 34 arranged between the extension portion 
30 and the housing cap 18. In the valve body 28 is formed an elbow-like 
main passage 36 for communicating either of the inlet ports with the 
outlet port. Referring to the illustrated embodiment, the elbow-like main 
passage 36 is so designed that one opening 38a thereof is communicated 
with the inlet port 24, while the other opening 38b is communicated with 
the outlet port 26. The outlet port 26 is communicated with a bottom 
tuyere (not shown) of the converter. Inside the first and second inlet 
ports 22 and 24 are fitted cylindrical seat rings 42, 42' through seat 
holds 44, 44' for the purpose of hermetically sealing that portion of each 
inlet port which contacts with the valve body 28. These seat rings are 
arranged under such a state that they are pushed against the outer 
periphery of the valve body, whereby the leakage of the gases A and B into 
a shroud-like gap 80 as mentioned later can be prevented. 
Furthermore, an inlet port 40 for a purging gas is opened in the housing 12 
at a position orthogonal to the inlet ports 22 and 24 in the same plane. 
This inlet port 40 is always communicated with the outlet port 26 during 
the rotation of the valve body 28 for moving the opening 38a of the main 
passage 36 in the valve body 28 from the first inlet port 22 to the second 
inlet port 24 and vice versa, that is, during the changing-over between 
the inlet passages, whereby the two gases A and B are prevented from being 
mixed with each other. 
For this purpose, according to the invention, a shroud-like gap 80 is 
formed between the inner periphery of the housing 12 and the outer 
periphery of the valve body 28 so as to surround, for example, about a 
half of the outer periphery of the valve body 28. Thus, a purging gas 
introduced from the inlet port 40 once enters into the shroud-like gap 80 
and then passes from the opening 38a of the main passage through the 
opening 38b thereof into the outlet port 26 directing to the converter. 
In order to change over the inlet passage, the valve body 28 is rotated by 
a driving means 48 as shown in FIG. 4. The driving means 48 comprises a 
pair of parallel cylinders 50, 50' partially communicating with each 
other, pistons 52 and 52' disposed in the cylinders 50, 50', rods 54, 54' 
connected to the respective pistons 52 and 52' and having racks 56 and 56' 
on the opposite faces thereof, and a pinion 58 engaging with both the 
racks 56, 56'. 
A coupling 60 is connected at its one end to the lower extension portion 30 
of the valve body 28 and at the other end to a pinion shaft 62 cooperating 
with the pinion 58. When the pinion 58 is rotated by moving the racked 
rods 54 and 54' with the reciprocal movement of the pistons 52 and 52', 
the valve body 28 is driven through the coupling 60 and the extension 
portion 30. 
In FIGS. 5a-5l is illustrated the relation of the inlet ports 22, 24 and 40 
to the main passage 36 when the valve body 28 is rotated for the 
changing-over of the inlet passage. The illustrated embodiment is a 
sequence of changing the kind of gases to be flown into the converter from 
gas A to gas B. When actuating the driving means 48 for the valve body 28, 
the complete communication state between the first inlet port 22 and the 
opening 38a of the main passage 36 as shown in FIG. 5a becomes gradually 
incomplete, and the supply of the gas A into the converter is completely 
stopped at such a state as shown in FIG. 5d. In this state, since a 
purging gas C is filled in the shroud-like gap 80 surrounding the valve 
body 28 through the inlet port 40, the gas A passing through the main 
passage 36 is completely purged with the purging gas C. Only the flowing 
of the gas C is continued until a state of FIG. 5i. When the valve body 28 
is rotated to a state of FIG. 5j, a part of the purging gas C is replaced 
with the gas B, and the amount of gas B gradually increases with the 
rotation of the valve body. Lastly, the gas C passing through the main 
passage 36 is completely replaced with the gas B in a state of FIG. 5l. If 
it is intended to change the gas B into the gas A, the pistons 52 and 52' 
are reversely moved to make the operation from FIG. 5l to FIG. 5a. 
The above changing-over is featured by the action of the shroud-like gap 80 
formed so as to surround the valve body 28. That is, the gap 80 is always 
filled with the purging gas (Ar, N.sub.2, or the like) at a pressure 
enough to overcome the static pressure of molten steel in the converter, 
preferably at a pressure equal to that of the gases A and B, so that the 
changing-over of inlet passage can be performed in such a state that both 
the gases A and B are completely prevented from being mixed with each 
other under the controlled pressure. 
FIGS. 6 and 7 show changes of flow rate in the gases A, B and the purging 
fluid C (in this example, gas) with the lapse of time in the 
aforementioned changing-over of inlet passage. As apparent from FIG. 6, 
when the valve body is rotated as shown by arrows in FIGS. 5a-5l, the gas 
C is supplied to the main passage 36 on the way where the gas A is changed 
to the gas B. Then, the gas B is flown into the main passage 36 after the 
gas inside the main passage 36 is completely replaced with the gas C. 
Thus, the mixing between the gases A and B is completely prevented. As 
shown in FIG. 7, when the valve body is rotated in the opposite direction, 
the gas C is supplied into the main passage 36 to purge the gas B inside 
the main passage 36, on the way where the gas B is changed to the gas A, 
so that the mixing between the gas B and the gas A is also prevented. 
FIG. 8 is a vertical sectional view of another embodiment of the flow 
change-over valve 110 according to the invention, which is disposed midway 
of a gas supply passage connected to a tuyere of a bottom-blown converter. 
In FIG. 8, numeral 112 is a housing, which comprises a main housing body 
114 and a housing cap 118 attached thereto by means of bolts 116. Numeral 
119 is an O-ring for sealing. Numeral 120 is a valve body-fitting portion 
formed in the housing 112. In the main housing body 114 are formed a first 
inlet port 122 and a second inlet port 124 so as to communicate the 
fitting portion 120 to the exterior and to supply gases A and B 
therethrough, respectively. An opening 126 is formed in the housing cap 
118. 
Into the valve body-fitting portion 120 is installed a spherical type valve 
body 128 having upper and lower extension portions 130 and 131 in an axial 
direction thereof, which are supported within the housing 112 by means of 
bearings 132 and 134. In the valve body 128 is formed a main passage 136, 
one end of which being opened to the side periphery of the valve body 128 
(numeral 138 being its opening) and the other being an opening 140 as an 
outlet port of the flow change-over valve. The outlet port 140 is 
communicated with a tuyere (not shown). A ring-like large diameter sealing 
member 142 is supported by a seal retainer 144 at an opening of each of 
the first and second inlet ports 122, 124 facing the valve body 128, while 
being urged to the valve body by means of a resilient member 146, whereby 
the gases A and B are prevented from flowing into a gap 180 as mentioned 
later. 
The valve body 128 is rotatably driven by a driving means 148. This driving 
means 148 comprises a cylinder 150, a piston 152 disposed in the cylinder 
150, a rod 154 connected to a piston 152, a rack 156 secured to the rod 
154, and a spring 158 causing a restoring movement of the piston 152. On 
the other hand, a shaft 160 is connected to the lower extension portion 
131 of the valve body 128, and a pinion 162 engaging with the rack 156 is 
attached to the tip of the shaft 160. A pressure Pa or Pb is applied to 
the cylinder 150 from a line 164 for the supply of a purging fluid through 
a pressure control valve 166 and a flow control valve 168 to move the 
piston 152. Moreover, the flow control valve 168 is arranged to diminish 
the fluctuation of the pressure inside the cylinder 150 during the 
changing-over of inlet passage (when the purging gas is flown) as 
mentioned later. When the pressure Pb higher than a force overcoming the 
spring force of the spring 158 is applied from the line 164 to the 
cylinder 150, the piston 152 is moved in the right direction in FIG. 8, 
during which the rack 156 is shifted to turn the pinion 162, whereby the 
valve body 128 is rotated in a forward direction. When the pressure 
applied from the line 164 to the cylinder 150 is a small pressure Pa, the 
piston 152 is returned to its original position (in the left direction in 
FIG. 8) by the resilient force stored in the spring 158, so that the 
pinion 162 and hence the valve body 128 are reversely rotated with the 
leftward movement of the rack 156. 
In the main housing body 114 and the valve body 128 are bored supply 
passages 170 and 172 for the purging fluid, respectively, which 
communicate the main passage 136 to the outside of the flow change-over 
valve 110, wherein the opening 174 of the passage 170 on the side of the 
main housing body 114 and an opening 176 of the passage 172 on the side of 
the valve body 128 are so arranged that they are opposed to each other to 
communicate the passage 170 with the passage 172 during the changing-over 
of inlet passage against the main passage 136 of the valve body 128. In 
FIGS. 9 and 10 are enlargedly shown portions of the openings 174 and 176, 
wherein FIG. 9 is a perspective view as viewed from the arrow IX of FIG. 8 
and FIG. 10 is a sectional view as taken along the line X--X of FIG. 8. 
The purging fluid is supplied into the purging fluid supply passage 170 
formed in the main housing body 114 from the purging fluid supply line 164 
through a pipe line 178. Further, a passage 182 for supplying a 
pressurized fluid is formed in the main housing body 114 to communicate 
the gap 180 between the valve body 128 and the housing 112 with the 
purging fluid supply passage 170. so that the purging fluid can be 
supplied into the gap 180 at the pressurized state. 
Moreover, a ring-like small diameter sealing member 184 is supported by 
means of a retainer 186 and resilient member 188 as in the case of the 
first and second inlet ports 122 and 124, whereby the leakage of the 
purging fluid is prevented. 
FIG. 8 illustrates such a state that the high pressure Pb is applied to the 
cylinder 150 so as to push the piston 152 up to the utmost pushed 
position. In this case, the main passage 136 communicates with the second 
inlet port 124, so that the gas B flows toward the tuyere through the main 
passage 136. When the pressure applied from the line 164 to the cylinder 
150 is reduced from Pb to Pa, the piston 152 is moved toward the left 
direction by the resilient force of the spring 158, whereby the valve body 
128 is rotated to communicate the main passage 136 with the first inlet 
port 122. In this changing-over of inlet passage, the main passage 136 is 
communicated with none of the first and the main passage 136 is 
communicated with none of the first and second inlet ports 122, 124 in the 
course of rotating the valve body 128. In this state, the purging fluid 
supply passages 170 and 172 are communicated with each other, whereby the 
purging fluid is supplied into the main passage 136 from the line 164. 
FIGS. 11a-11e illustrate the communication state between the opening 174 
and the opening 176 as viewed from the side of the opening 174 toward the 
extension portion 131 of the valve body 128. FIG. 11a shows the state in 
which the first inlet port 122 is communicated with the main passage 136. 
FIG. 11e shows the state in which the second inlet port 124 is 
communicated with the main passage 136. As the valve body is rotated from 
the state shown in FIG. 11a to states as shown by arrows 101, 102 and 103, 
the communicating area between the openings 174 and 175 gradually 
increases, and the purging fluid begins to flow. After passing through the 
maximum communication state of FIG. 11c, the valve body is further rotated 
to states as shown by arrows 104 and 105 to terminate the flowing of the 
purging fluid. When the valve body is reversely rotated as shown by arrows 
201, 202, . . . , 205, the purging fluid is supplied into the main passage 
136 through the passages 170 and 172 as similarly but reversely in the 
previous operation. The change of flow rate in the gases A and B and the 
purging fluid C (gas in this case) with the lapse of time during 
changing-over of inlet passage is substantially the same as in FIGS. 6 and 
7. 
As mentioned above, when the piston 152 is returned to its original 
position (moved in the left direction of FIG. 8), the pressure Pa lower 
than that at the forward movement is applied to the cylinder 150 (FIG. 12 
is a graph showing the change of the pressure in gas C with the lapse of 
time). This pressure Pa is so set that the pressure of the purging fluid 
to be introduced into the main passage 136 becomes enough to overcome the 
static pressure of molten metal imposed upon the tuyere. It is preferable 
that the spring constant of the spring 158 is set at such a degree that 
the difference between the pressures Pb and Pa is not extremely large in 
the reciprocal movement of the piston. 
Although the valve body 28 or 128 is rotated by the driving means 48 or 148 
of cylinder type in the above illustrated embodiment, it may be driven by 
a separate motor. Further, although the above explanation relates to the 
use of the flow change-over valve 10 or 110 in the tuyere of the 
bottom-blown converter, the invention may be applied to other molten metal 
vessel such as an outside furnace refining vessel and the like in which 
the mixing of two fluids, for instance, two gases must be avoided. 
As mentioned above, according to the invention, when changing-over the 
inlet passage of the flow change-over valve, the purging fluid is 
introduced into the main passage of the valve body to replace the fluid 
present in the main passage with the purging fluid, so that the mixing of 
two gases are assurely prevented. Moreover, the gas exchange can stably be 
made without causing of fear of reducing the gas pressure applied to the 
tuyere during the changing-over of inlet passage.