Title of Invention	AN AIR KNIFE AND A METHOD OF REDUCING SOLIDS BUILDUP AT THE ENTRANCE OF A VESSEL
Abstract	Cyclone separators are used for separating solids from a gas/solid mixtures. The removed solids can collect in piping downstream of the separator as they encounter cooler surfaces or higher humidity conditions, complicating their recovery. The invention concerns a circumferential air knife that can be placed downstream at these susceptible locations. The air knife (300) [FIG.3] comprises a plurality of overlapping wall sections (308, 310, 312) which define a circumferential passage through which the solids (302) pass, with at least two of the overlapping wall sections (308, 310 and 310, 312) forming a gap between them facing in the flow direction (306), and a gas intake (314) connected to the gap so inert gases can be fed through the gap and along the circumference of the passage. The gases sweep clear the circumference of the passage in locations susceptible to solids buildup.

Title of Invention

AN AIR KNIFE AND A METHOD OF REDUCING SOLIDS BUILDUP AT THE ENTRANCE OF A VESSEL

Abstract

Cyclone separators are used for separating solids from a gas/solid mixtures. The removed solids can collect in piping downstream of the separator as they encounter cooler surfaces or higher humidity conditions, complicating their recovery. The invention concerns a circumferential air knife that can be placed downstream at these susceptible locations. The air knife (300) [FIG.3] comprises a plurality of overlapping wall sections (308, 310, 312) which define a circumferential passage through which the solids (302) pass, with at least two of the overlapping wall sections (308, 310 and 310, 312) forming a gap between them facing in the flow direction (306), and a gas intake (314) connected to the gap so inert gases can be fed through the gap and along the circumference of the passage. The gases sweep clear the circumference of the passage in locations susceptible to solids buildup.

Full Text	AN AIR KNIFE AND A METHOD OF REDUCING SOLIDS BUILDUP AT THE ENTRANCE OF A VESSEL The present invention relates to an air knife and a method of reducing solids buildup at the entrance of a vessel and generally, relates to the use of a novel air knife to help prevent solid particulars from blocking the entrance to a vessel. More specifically, the present invention is particularly useful for reducing blockage by solid chlorides removed from a titanium tetrachloride product gas by a cyclone or by some other gas/solids separation device, in processes for producing titanium tetrachloride. The production of titanium tetrachloride ("TiCl4") via the chlorination of titanium values in a titanium-containing starting material is generally known in the art The production of("TiCl4") is useful, for example, in the production of titaniummetal or titanium dioxide ("TiCl4"). As is known in the art, ("TiCl4") can be produced by reacting chlorine gas with titanium- containing starting materials in a chlorinator. During this process, a solids-laden gas mixture comprised of the desired ("TiCl4") gas and residual solid chlorides is removed from the chlorinator, cooled, and conventionally is then transferred to a cyclone separator to remove the solids from the solids-laden gas mixture. The solids are then dumped into a suspension vessel, frequently referred to as a chlorinator sump, where the solids are mixed with water to form a uspension. These removed solids are typically very warm upon entering the suspension vessel. The mixing of these hot solids with water in the suspension vessel results in a high humidity gas phase in the space above the suspension in the vessel, including the length of pipe that carries the cyclone dust from the cyclone to the suspension vessel. The cyclone dust contains metal chlorides, which are hygroscopic, and as such become sticky when entering the high humidity areas of the pipe that transfers the cyclone dust from the cyclone to the suspension vessel. The sticky solids gradually build up on the walls of the pipe until the pipe is completely plugged, stopping further discharge of solids from the cyclone. Clearing the blockage requires operation downtime to unclog and can be a safety hazard. US 5,620,643 describes a process for producing fused particle agglomerates having improved coating properties and reduced dust generation during powder application, such as materials used for powder coating of metals. The apparatus used for carrying out the process feeds (by gravity) a compounded premixed powder material from a nozzle of a feed hopper into the first portion of a substantially transparent tubular powder processor. In the tubular powder processor, the powder encounters energy from one or more water-cooled, high-intensity light sources, which energy causes the particles of powder to soften and become tacky, so that they adhere to one another and emerge from a subsequent cooling section of the tubular powder processor as the desired agglomerated powder particles. To prevent the tacky particles from adhering to the inner wall of the tubular processor and to correspondingly facilitate the continued exposure of the particles to further light energy over a greater length of the processor, an air knife is illustrated for sweeping the internal surface of the first portion of the processor. However, the air knife of US 5,620,643 is an independent device introduced into the particulate passage at its entrance, whereas in the device according to the invention, which will be described and claimed hereinafter, the air knife is formed in the passage itself by a gap between overlapping wall sections of the passage. Consequently, while the air knife of US 5,620,643 must be at the entrance of the particulate passage, in the device according to the invention the gas that is supplied to prevent tacky particles from adhering to the interior walls of the passage (and to thus prevent fouling of the passage) can be supplied at any point in the passage where such help is needed, or at several such points. The present invention addresses the issues presented above by placing a novel air knife at or near the entrance to the suspension vessel. The cyclone dust passes through the air knife on its way to the suspension vessel. The novel air knife is circumferential. That is, the novel air knife injects a gas stream along the inside walls of the air knife. The gas stream is injected at a rate sufficient to reduce the buildup of hygroscopic cyclone dust on the walls of the air knife (and thus at the entrance to the chlorinator sump), so that the chlorinator sump can continue to receive solids from the cyclone, improving time-on-line and safety. In one embodiment, the present invention is a novel air knife adapted to reduce hygroscopic solids from building up at the entrance to a suspension vessel enclosing a high- humidity environment. In a second embodiment, the present invention is a method for preventing hygroscopic solids from building up at the entrance to a suspension vessel enclosing a high-humidity environment The present invention is illustrated by way of example in the following drawings in which like references indicate similar elements. The following drawings disclose various preferred embodiments of the present invention for purposes of illustration only and are not intended to limit the scope of the invention. FIG. 1 is a diagram of a ("TiCl4") production process. FIG. 2 illustrates a process utilizing an air knife according to the present invention in conjunction with a cyclone separator and a suspension vessel. FIG. 3 illustrates a cut-away view of an air knife according to the present invention. FIG. 4 illustrates a top-down view of the air knife shown in Figure 3. Figure 1 illustrates a schematic of a typical ("TiCl4") production process 100. The process 100 illustrated in Figure 1 involves chlorination of titanium-bearing ores. Ore 104 and coke 106, preferably petroleum coke, are conveyed to a chlorinator 102 on a timed basis to maintain a certain bed level 108 and composition. Chlorine gas 110 is fed up to the bed through a distributor in the bottom of the chlorinator 102. The chlorinatiqn reaction occurs as the chlorine gas 110 flows up through the bed. Most of the titanium values in the bed are reacted to form ("TiCl4"). Metal oxides in the ore 104 largely are converted into gaseous metal chlorides. Other gases are also formed including carbon dioxide ("CO2") and carbon monoxide ("CO") Impurities in the ore are also chlorinated, forming chlorides such as FeCl2 and MnCl2, for example. A hot reaction solids-laden gas mixture exits 112 from the chlorinator 102 and typically may comprise CO, CO2, COS, HC1,N2, low-boiling and high-boiling chlorides such as TiCl4, FeCl3, FeCl2, MnCl2, SnCl4, SiCl4, VOC13, NaAlCl4, and unreacted solids such as TiO2, SiO2 as well as unburned coke. The solids-laden gas mixture is cooled in a cooling conduit 114, sometimes referred to as a chlorinator crossover, and then sent to a cyclone separator 116 where the gases and solids are separated. Cyclone separators comprise well known means for separating gases and solids. Cyclone separators generally are constructed of the tubular or cylindrical-shaped main body connected to a lower tapered conical portion. A tangential side inlet is provided near the top of the cylindrical main body. A gas outlet tube is provided and generally extends downwardly through the cyclone top into the main body of the cyclone. The tube usually must extend down to a level slightly below the lowest portion of the inlet to assure efficient separation of solids and gases. In operation, the solids-laden gases are introduced at high velocity through the tangential inlet. They follow a vortex-shaped path around the outside of the gas outlet pipe downwardly towards the bottom of the separator. The solids, which are heavier than the gases, are thrown against the walls of the cyclone by centrifugal force. Gravity then causes the solids to fall to the bottom of the cyclone. The separated gas follows a vortex path upwardly and passes out of the top of the cyclone separator through the gas outlet tube. The separated solids flow through a solids outlet at the base of the tapered conical section. These separated solids are typically referred to as cyclone dust or waste solids. To minimize the amount of gas that is dumped along with the cyclone dust, a two- valve dump spool leg is typically used on the bottom of the cyclone. The opening and closing of these valves is interlocked so only one valve can possibly be open at any given time. When the top valve is opened, the bottom is closed. This allows cyclone dust to fall through the top valve and fill the dump spool leg. When the top valve closes, the bottom valve is opened to empty the dump spool leg to the suspension vessel. The valves continuously operate on a timer. In Figure 1, the solids-laden gas mixture flows from the chlorinator crossover 114 into the cyclone 116 through a tangential inlet 118. The gases from the solids-laden gas mixture exit cyclone 116 through the gas outlet tube 120 at the top of the cyclone 116 and the solids exit the cyclone 116 through the dump spool leg 122 at the base of the cyclone 116. The cyclone dust collected at the bottom of the cyclone exits the bottom of the cyclone, is transported through a tube or pipe by force of gravity, and is deposited into a suspension vessel. The section of pipe connecting the cyclone and the suspension vessel can vary in length, typically being from about 20 feet to about 50 feet in length. The suspension vessel is frequently referred to as a chlorinator sump. Once deposited into the suspension vessel, the cyclone dust is mixed with water to form a suspension. Typically, any gas in the suspension vessel is removed through a vent in the top of the vessel and the suspension is pumped out of the vessel as waste or for further processing. Figure 1 shows the cyclone dust 124 entering the suspension vessel 132, water 126 being added to the suspension vessel 132, gas 128 being removed from the suspension vessel 132, and suspension 130 being pumped out of the suspension vessel 132. The cyclone dust is typically very warm upon entering the suspension vessel. The mixing of these hot solids with water in the suspension vessel results in a high humidity gas phase in the space above the suspension in the vessel. This high-humidity environment can extend into the length of pipe that carries the cyclone dust from the cyclone to the suspension vessel. The cyclone dust contains metal chlorides, which are hygroscopic, and as such become sticky when entering the high humidity areas of the pipe that transfers the cyclone dust from the cyclone to the suspension vessel. The sticky solids gradually build up at the opening of the pipe into the suspension vessel or on the walls of the pipe until the pipe is completely plugged, stopping further discharge of solids from the cyclone. Clearing the blockage requires operation downtime to unclog and can be a safety hazard. Stopping the production process to clear a blockage is not only an economic disadvantage, allowing an operator access to the inside of the pipe to clear the blockage creates a risk of gas emissions. The blockage can also result in condensed ("TiCl4") being present, which can hydrolyze explosively should an operator try clearing the line with water. According to the present invention, a novel air knife is advantageously utilized to reduce or eliminate the buildup of hygroscopic materials on the inside of the pipe that transports the cyclone dust from the cyclone separator to the suspension vessel. The novel air knife is connected to the cyclone separator in the sense that the novel air knife is attached to the tube or pipe that transports cyclone dust from the cyclone to the suspension vessel in a manner that requires the cyclone dust to pass through the air knife either before the dust enters the suspension vessel or as the dust enters the suspension vessel. Preferably, the air knife is placed at or near the entrance to the suspension vessel. Air knives according to the present invention are circumferential. By circumferential it is meant that the air knife creates a stream of gas inside the air knife along the circumference of the passage in the air knife through which the cyclone dust passes. Typically, the pipe carrying the cyclone dust from the cyclone to the suspension vessel is circular and the inside of the air knife will have a circular passage through which the cyclone dust passes. However, the present invention is not so limited. Other geometric shapes are within the scope of the present invention. For example, the pipe transporting the cyclone dust and the inside passage of the air knife could be oval shaped or even rectangular. The gas stream created by air knives of the present invention has a velocity sufficient to blow most or all hygroscopic material from the inside wall of the air knife. In this manner, the air knife reduces the amount of hygroscopic material that can accumulate, significantly reducing the chance that the entrance to the suspension vessel can be blocked by accumulated hygroscopic material. When used in a ("TiCl4") production process to reduce cyclone dust accumulation, the gas stream will preferably have a velocity of at least 30 meters/second (100 feet per second), and more preferably, at least 60 meters per second (200 feet per second). Still more preferably, the gas stream will have a velocity of at least 120 meters/second (400 feet per second). While some applications of the present invention may require a gas stream velocity of greater than 150 meters/second (500 feet per second), preferably the gas stream velocity is no more than 150 meters/second (500 feet per second). The gas stream created by the air knife generally travels in the same direction as the direction in which the hygroscopic material moves through the air knife. In one embodiment, the gas stream travels parallel to the direction of the hygroscopic material. However, it is within the scope of the present invention to adapt the air knife to create a gas stream that travels at an angle to the direction of the hygroscopic material, causing the gas stream to travel in a spiral motion when the air knife passage is circular. Figure 2 illustrates a process 200 utilizing an air knife 202 according to the present invention in conjunction with a cyclone separator 206 and a suspension vessel 204. The solids-laden gases are introduced into the cyclone separator 206 at the tangential inlet 208. Inside the cyclone separator 206 the solids and gases are separated. The gases exit the cyclone separator through a gas outlet tube 210 and gravity causes the solids to collect at the bottom 212 of the cyclone separator 206. A two-valve dump spool leg 214 minimizes the amount of gas that is dumped along with the cyclone dust. A pipe 216 connects the dump spool leg 214 with the air knife 202. Cyclone dust that is dumped from the two-valve dump spool leg 214 falls through the pipe 216 and through the air knife 202 into the suspension vessel 204. Figure 3 illustrates a cut away view of an air knife 300 according to the present invention. Hygroscopic material 302 enters the air knife 300 via a pipe 304 such as the pipe 216 shown in Figure 2 and travels down through the air knife 300 in the direction indicated by the arrow 306. The air knife 300 comprises three overlapping wall sections 308,310, and 312. The overlapping portions of the wall sections form gaps through which gas is forced. The gaps face in the same direction in which the cyclone dust moves. By facing in the same direction it is meant that the gas forced through the gaps moves through the air knife in the same direction as the cyclone dust. Preferably, air knives of the present invention will comprise at least two different circumferential gaps through which gas is forced. Generally, the size of the gap (that is, the distance between two wall sections) is no more than 0.18 cm (0.07 inches), and preferably no more than 0.13 cm (0.05 inches). In one embodiment, air knives having a gap size of 0.09 cm (0.036 inches) have been advantageously utilized in a ("TiCl4") production process to keep hygroscopic cyclone dust from accumulating on the walls of the air knife. Air knives according to the present invention have at least one gas intake. Typically, air knives of the present invention will have between two and four gas intakes. In Figure 2, gas flows into the gas intake 314 and travels in the direction indicated by the arrows. The gas is forced through the gaps between the wall sections 308,310, and 312 at a velocity sufficient to blow most or all hygroscopic material from the inside part of the wall sections 308,310, and 312 of the air knife. The gas velocity is calculated in a conventional manner, by dividing the gas flow into the gas intakes by the cross-sectional area of the circumferential gap. Figure 4 illustrates a top-down view of the air knife 300 shown in Figure 3. As seen in Figure 4, the air knife 300 has four gas intakes. The air knife 300 also comprises a series of bolts 316. The bolts 316 on this embodiment of the present invention are used to fasten the air knife 300 to a suspension vessel. However, other methods for attaching air knives to suspension vessels are within the scope of the present invention. Figure 4 also shows the opening 318 at the center of the air knife 300 through which the cyclone dust passes on its way to the suspension vessel. Air knives according to the present invention have been advantageously utilized at the entrance to a suspension vessel in a ("TiCl4") production process without requiring additional ventilation in the suspension vessel. As shown in Figure 4, the wall sections of the air knife 300 can be attached to each other by small spot welds 320 placed between the wall sections of the air knife 300. That is, these spot welds 320 are in the gaps between the wall sections. The size of the spots welds 320 is not particularly critical so long as they are not so large as to interfere with the flow of gas through the gaps. Air knives of the present invention can be manufactured using any material suitable for the intended application. An appropriate material can be determined without undue experimentation. Typically, air knives utilized in a ("TiCl4") production process will be manufactured from a corrosion resistant alloy such as Inconel 600 or Inconel 601 (commercially available from various steel and alloy distributors). Gases suitable for use with air knives of the present invention may depend on the particular application in which the air knife is used. However, appropriate gases can be determined without undue experimentation. Gases preferred for use with air knives in a ("TiCl4") production process include air, nitrogen, argon, carbon dioxide or any other gas that will not appreciably react under the conditions prevailing in the air knife. While the present invention has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. For example, air knives of the present invention can be 5 advantageously utilized in applications in addition to the production of ("TiCl4") It is within the scope of the present invention to utilize the novel air knives of the presenfinvention in many applications benefiting from the present invention's ability to reduce buildup of materials during transport from one vessel to another, such as through a tube or pipe. Accordingly, the scope of the present invention should be assessed as that of the appended claims and any 10 equivalents thereto. WE CLAIM : 1. An air knife, comprising: a plurality of overlapping wall sections defining a passage having a circumference, the passage being adapted to allow solid materials to pass through the air knife in a first direction; at least two of the plurality of the overlapping wall sections forming a gap between them, the gap facing in the first direction; and at least one gas intake connected to the gap in a manner causing gas entering the intake to pass through the gap and into the passage along the circumference of the passage. 2. The air knife as claimed in claim 1, wherein the circumference is circular. 3. The air knife as claimed in claim 1, wherein the gap is no more than 0.18 centimeters. 4. The air knife as claimed in claim 1, wherein the gap is no more than 0.13 centimeters. 5. The air knife as claimed in claim 1, wherein the air knife is connected to a cyclone separator by a pipe. 6. The air knife as claimed in claim 5, wherein the cyclone separator separates hygroscopic solids from gases. 7. The air knife as claimed in claim 1, wherein the air knife is attached to a suspension vessel adapted to receive solids including hygroscopic solids from a cyclone separator. 8. The air knife as claimed in claim 7, wherein the suspension vessel encloses a high-humidity environment. 9. A method of reducing solids buildup at the entrance of a vessel, by employing an air knife as claimed in claim 1 to said vessel, said method comprising the steps of: allowing solid materials to pass through a passage defined by the plurality of overlapping wall sections of the air knife, in a first direction, and injecting a gas stream through the gap formed between at least two of the plurality of overlapping wall sections of the air knife, in the said first direction, along which the solid materials pass through said passage. 10. A method as claimed in claim 9, wherein buildup of hygroscopic solid material is reduced. 11. A method as claimed in claim 9, wherein buildup of cyclone dust from a cyclone separator is reduced. 12. A method as claimed in claim 10 or 11, wherein the air knife is positioned to reduce solids buildup from exposure of the solids to a downstream higher- humidity environment. 13. A method as claimed in claim 9, wherein the gas stream is injected at a velocity of at least 30 meters per second. 14. A method as claimed in claim 9, wherein the gas stream is injected at a velocity of at least 60 meters per second. 15. A method as claimed in claim 9, wherein the gas stream is injected at a velocity of at least 120 meters per second. Cyclone separators are used for separating solids from a gas/solid mixtures. The removed solids can collect in piping downstream of the separator as they encounter cooler surfaces or higher humidity conditions, complicating their recovery. The invention concerns a circumferential air knife that can be placed downstream at these susceptible locations. The air knife (300) [FIG.3] comprises a plurality of overlapping wall sections (308, 310, 312) which define a circumferential passage through which the solids (302) pass, with at least two of the overlapping wall sections (308, 310 and 310, 312) forming a gap between them facing in the flow direction (306), and a gas intake (314) connected to the gap so inert gases can be fed through the gap and along the circumference of the passage. The gases sweep clear the circumference of the passage in locations susceptible to solids buildup.

Full Text

AN AIR KNIFE AND A METHOD OF REDUCING
SOLIDS BUILDUP AT THE ENTRANCE OF A VESSEL
The present invention relates to an air knife and a method of reducing
solids buildup at the entrance of a vessel and generally, relates to the use of a
novel air knife to help prevent solid particulars from blocking the entrance to a
vessel. More specifically, the present invention is particularly useful for reducing
blockage by solid chlorides removed from a titanium tetrachloride product gas by a
cyclone or by some other gas/solids separation device, in processes for producing
titanium tetrachloride.
The production of titanium tetrachloride ("TiCl4") via the chlorination of titanium
values in a titanium-containing starting material is generally known in the art The
production of("TiCl4") is useful, for example, in the production of titaniummetal or titanium
dioxide ("TiCl4").
As is known in the art, ("TiCl4") can be produced by reacting chlorine gas with titanium-
containing starting materials in a chlorinator. During this process, a solids-laden gas mixture
comprised of the desired ("TiCl4") gas and residual solid chlorides is removed from the
chlorinator, cooled, and conventionally is then transferred to a cyclone separator to remove
the solids from the solids-laden gas mixture. The solids are then dumped into a suspension
vessel, frequently referred to as a chlorinator sump, where the solids are mixed with water to
form a uspension.
These removed solids are typically very warm upon entering the suspension vessel.
The mixing of these hot solids with water in the suspension vessel results in a high humidity
gas phase in the space above the suspension in the vessel, including the length of pipe that
carries the cyclone dust from the cyclone to the suspension vessel. The cyclone dust contains
metal chlorides, which are hygroscopic, and as such become sticky when entering the high
humidity areas of the pipe that transfers the cyclone dust from the cyclone to the suspension
vessel. The sticky solids gradually build up on the walls of the pipe until the pipe is
completely plugged, stopping further discharge of solids from the cyclone. Clearing the
blockage requires operation downtime to unclog and can be a safety hazard.
US 5,620,643 describes a process for producing fused particle
agglomerates having improved coating properties and reduced dust generation
during powder application, such as materials used for powder coating of metals.
The apparatus used for carrying out the process feeds (by gravity) a
compounded premixed powder material from a nozzle of a feed hopper into the
first portion of a substantially transparent tubular powder processor. In the
tubular powder processor, the powder encounters energy from one or more
water-cooled, high-intensity light sources, which energy causes the particles of
powder to soften and become tacky, so that they adhere to one another and
emerge from a subsequent cooling section of the tubular powder processor as
the desired agglomerated powder particles. To prevent the tacky particles from
adhering to the inner wall of the tubular processor and to correspondingly
facilitate the continued exposure of the particles to further light energy over a
greater length of the processor, an air knife is illustrated for sweeping the internal
surface of the first portion of the processor.
However, the air knife of US 5,620,643 is an independent device
introduced into the particulate passage at its entrance, whereas in the device
according to the invention, which will be described and claimed hereinafter, the
air knife is formed in the passage itself by a gap between overlapping wall
sections of the passage. Consequently, while the air knife of US 5,620,643 must
be at the entrance of the particulate passage, in the device according to the
invention the gas that is supplied to prevent tacky particles from adhering to the
interior walls of the passage (and to thus prevent fouling of the passage) can be
supplied at any point in the passage where such help is needed, or at several
such points.
The present invention addresses the issues presented above by placing a novel air
knife at or near the entrance to the suspension vessel. The cyclone dust passes through the air
knife on its way to the suspension vessel. The novel air knife is circumferential. That is, the
novel air knife injects a gas stream along the inside walls of the air knife. The gas stream is
injected at a rate sufficient to reduce the buildup of hygroscopic cyclone dust on the walls of
the air knife (and thus at the entrance to the chlorinator sump), so that the chlorinator sump
can continue to receive solids from the cyclone, improving time-on-line and safety.
In one embodiment, the present invention is a novel air knife adapted to reduce
hygroscopic solids from building up at the entrance to a suspension vessel enclosing a high-
humidity environment. In a second embodiment, the present invention is a method for
preventing hygroscopic solids from building up at the entrance to a suspension vessel
enclosing a high-humidity environment
The present invention is illustrated by way of example in the following drawings in
which like references indicate similar elements. The following drawings disclose various
preferred embodiments of the present invention for purposes of illustration only and are not
intended to limit the scope of the invention.
FIG. 1 is a diagram of a ("TiCl4") production process.
FIG. 2 illustrates a process utilizing an air knife according to the present invention in
conjunction with a cyclone separator and a suspension vessel.
FIG. 3 illustrates a cut-away view of an air knife according to the present invention.
FIG. 4 illustrates a top-down view of the air knife shown in Figure 3.
Figure 1 illustrates a schematic of a typical ("TiCl4") production process 100. The
process 100 illustrated in Figure 1 involves chlorination of titanium-bearing ores. Ore 104
and coke 106, preferably petroleum coke, are conveyed to a chlorinator 102 on a timed basis
to maintain a certain bed level 108 and composition. Chlorine gas 110 is fed up to the bed
through a distributor in the bottom of the chlorinator 102. The chlorinatiqn reaction occurs as
the chlorine gas 110 flows up through the bed. Most of the titanium values in the bed are
reacted to form ("TiCl4"). Metal oxides in the ore 104 largely are converted into gaseous metal
chlorides. Other gases are also formed including carbon dioxide ("CO2") and carbon
monoxide ("CO") Impurities in the ore are also chlorinated, forming chlorides such as FeCl2
and MnCl2, for example.
A hot reaction solids-laden gas mixture exits 112 from the chlorinator 102 and
typically may comprise CO, CO2, COS, HC1,N2, low-boiling and high-boiling chlorides such
as TiCl4, FeCl3, FeCl2, MnCl2, SnCl4, SiCl4, VOC13, NaAlCl4, and unreacted solids such as
TiO2, SiO2 as well as unburned coke. The solids-laden gas mixture is cooled in a cooling
conduit 114, sometimes referred to as a chlorinator crossover, and then sent to a cyclone
separator 116 where the gases and solids are separated.
Cyclone separators comprise well known means for separating gases and solids.
Cyclone separators generally are constructed of the tubular or cylindrical-shaped main body
connected to a lower tapered conical portion. A tangential side inlet is provided near the top
of the cylindrical main body. A gas outlet tube is provided and generally extends
downwardly through the cyclone top into the main body of the cyclone. The tube usually
must extend down to a level slightly below the lowest portion of the inlet to assure efficient
separation of solids and gases.
In operation, the solids-laden gases are introduced at high velocity through the
tangential inlet. They follow a vortex-shaped path around the outside of the gas outlet pipe
downwardly towards the bottom of the separator. The solids, which are heavier than the
gases, are thrown against the walls of the cyclone by centrifugal force. Gravity then causes
the solids to fall to the bottom of the cyclone. The separated gas follows a vortex path
upwardly and passes out of the top of the cyclone separator through the gas outlet tube. The
separated solids flow through a solids outlet at the base of the tapered conical section. These
separated solids are typically referred to as cyclone dust or waste solids.
To minimize the amount of gas that is dumped along with the cyclone dust, a two-
valve dump spool leg is typically used on the bottom of the cyclone. The opening and
closing of these valves is interlocked so only one valve can possibly be open at any given
time. When the top valve is opened, the bottom is closed. This allows cyclone dust to fall
through the top valve and fill the dump spool leg. When the top valve closes, the bottom
valve is opened to empty the dump spool leg to the suspension vessel. The valves
continuously operate on a timer.
In Figure 1, the solids-laden gas mixture flows from the chlorinator crossover 114
into the cyclone 116 through a tangential inlet 118. The gases from the solids-laden gas
mixture exit cyclone 116 through the gas outlet tube 120 at the top of the cyclone 116 and the
solids exit the cyclone 116 through the dump spool leg 122 at the base of the cyclone 116.
The cyclone dust collected at the bottom of the cyclone exits the bottom of the
cyclone, is transported through a tube or pipe by force of gravity, and is deposited into a
suspension vessel. The section of pipe connecting the cyclone and the suspension vessel can
vary in length, typically being from about 20 feet to about 50 feet in length.
The suspension vessel is frequently referred to as a chlorinator sump. Once
deposited into the suspension vessel, the cyclone dust is mixed with water to form a
suspension. Typically, any gas in the suspension vessel is removed through a vent in the top
of the vessel and the suspension is pumped out of the vessel as waste or for further
processing. Figure 1 shows the cyclone dust 124 entering the suspension vessel 132, water
126 being added to the suspension vessel 132, gas 128 being removed from the suspension
vessel 132, and suspension 130 being pumped out of the suspension vessel 132.
The cyclone dust is typically very warm upon entering the suspension vessel. The
mixing of these hot solids with water in the suspension vessel results in a high humidity gas
phase in the space above the suspension in the vessel. This high-humidity environment can
extend into the length of pipe that carries the cyclone dust from the cyclone to the suspension
vessel. The cyclone dust contains metal chlorides, which are hygroscopic, and as such
become sticky when entering the high humidity areas of the pipe that transfers the cyclone
dust from the cyclone to the suspension vessel. The sticky solids gradually build up at the
opening of the pipe into the suspension vessel or on the walls of the pipe until the pipe is
completely plugged, stopping further discharge of solids from the cyclone.
Clearing the blockage requires operation downtime to unclog and can be a safety
hazard. Stopping the production process to clear a blockage is not only an economic
disadvantage, allowing an operator access to the inside of the pipe to clear the blockage
creates a risk of gas emissions. The blockage can also result in condensed ("TiCl4") being
present, which can hydrolyze explosively should an operator try clearing the line with water.
According to the present invention, a novel air knife is advantageously utilized to
reduce or eliminate the buildup of hygroscopic materials on the inside of the pipe that
transports the cyclone dust from the cyclone separator to the suspension vessel. The novel air
knife is connected to the cyclone separator in the sense that the novel air knife is attached to
the tube or pipe that transports cyclone dust from the cyclone to the suspension vessel in a
manner that requires the cyclone dust to pass through the air knife either before the dust
enters the suspension vessel or as the dust enters the suspension vessel. Preferably, the air
knife is placed at or near the entrance to the suspension vessel.
Air knives according to the present invention are circumferential. By circumferential
it is meant that the air knife creates a stream of gas inside the air knife along the
circumference of the passage in the air knife through which the cyclone dust passes.
Typically, the pipe carrying the cyclone dust from the cyclone to the suspension vessel is
circular and the inside of the air knife will have a circular passage through which the cyclone
dust passes. However, the present invention is not so limited. Other geometric shapes are
within the scope of the present invention. For example, the pipe transporting the cyclone dust
and the inside passage of the air knife could be oval shaped or even rectangular.
The gas stream created by air knives of the present invention has a velocity sufficient
to blow most or all hygroscopic material from the inside wall of the air knife. In this manner,
the air knife reduces the amount of hygroscopic material that can accumulate, significantly
reducing the chance that the entrance to the suspension vessel can be blocked by accumulated
hygroscopic material. When used in a ("TiCl4") production process to reduce cyclone dust
accumulation, the gas stream will preferably have a velocity of at least 30 meters/second
(100 feet per second), and more preferably, at least 60 meters per second (200 feet per
second). Still more preferably, the gas stream will have a velocity of at least 120
meters/second (400 feet per second). While some applications of the present invention may
require a gas stream velocity of greater than 150 meters/second (500 feet per second),
preferably the gas stream velocity is no more than 150 meters/second (500 feet per second).
The gas stream created by the air knife generally travels in the same direction as the
direction in which the hygroscopic material moves through the air knife. In one embodiment,
the gas stream travels parallel to the direction of the hygroscopic material. However, it is
within the scope of the present invention to adapt the air knife to create a gas stream that
travels at an angle to the direction of the hygroscopic material, causing the gas stream to
travel in a spiral motion when the air knife passage is circular.
Figure 2 illustrates a process 200 utilizing an air knife 202 according to the present
invention in conjunction with a cyclone separator 206 and a suspension vessel 204. The
solids-laden gases are introduced into the cyclone separator 206 at the tangential inlet 208.
Inside the cyclone separator 206 the solids and gases are separated. The gases exit the
cyclone separator through a gas outlet tube 210 and gravity causes the solids to collect at the
bottom 212 of the cyclone separator 206. A two-valve dump spool leg 214 minimizes the
amount of gas that is dumped along with the cyclone dust. A pipe 216 connects the dump
spool leg 214 with the air knife 202. Cyclone dust that is dumped from the two-valve dump
spool leg 214 falls through the pipe 216 and through the air knife 202 into the suspension
vessel 204.
Figure 3 illustrates a cut away view of an air knife 300 according to the present
invention. Hygroscopic material 302 enters the air knife 300 via a pipe 304 such as the pipe
216 shown in Figure 2 and travels down through the air knife 300 in the direction indicated
by the arrow 306.
The air knife 300 comprises three overlapping wall sections 308,310, and 312. The
overlapping portions of the wall sections form gaps through which gas is forced. The gaps
face in the same direction in which the cyclone dust moves. By facing in the same direction
it is meant that the gas forced through the gaps moves through the air knife in the same
direction as the cyclone dust. Preferably, air knives of the present invention will comprise at
least two different circumferential gaps through which gas is forced. Generally, the size of
the gap (that is, the distance between two wall sections) is no more than 0.18 cm (0.07
inches), and preferably no more than 0.13 cm (0.05 inches). In one embodiment, air knives
having a gap size of 0.09 cm (0.036 inches) have been advantageously utilized in a ("TiCl4")
production process to keep hygroscopic cyclone dust from accumulating on the walls of the
air knife.
Air knives according to the present invention have at least one gas intake. Typically,
air knives of the present invention will have between two and four gas intakes. In Figure 2,
gas flows into the gas intake 314 and travels in the direction indicated by the arrows. The gas
is forced through the gaps between the wall sections 308,310, and 312 at a velocity sufficient
to blow most or all hygroscopic material from the inside part of the wall sections 308,310,
and 312 of the air knife. The gas velocity is calculated in a conventional manner, by dividing
the gas flow into the gas intakes by the cross-sectional area of the circumferential gap.
Figure 4 illustrates a top-down view of the air knife 300 shown in Figure 3. As seen
in Figure 4, the air knife 300 has four gas intakes. The air knife 300 also comprises a series
of bolts 316. The bolts 316 on this embodiment of the present invention are used to fasten
the air knife 300 to a suspension vessel. However, other methods for attaching air knives to
suspension vessels are within the scope of the present invention. Figure 4 also shows the
opening 318 at the center of the air knife 300 through which the cyclone dust passes on its
way to the suspension vessel. Air knives according to the present invention have been
advantageously utilized at the entrance to a suspension vessel in a ("TiCl4") production process
without requiring additional ventilation in the suspension vessel.
As shown in Figure 4, the wall sections of the air knife 300 can be attached to each
other by small spot welds 320 placed between the wall sections of the air knife 300. That is,
these spot welds 320 are in the gaps between the wall sections. The size of the spots welds
320 is not particularly critical so long as they are not so large as to interfere with the flow of
gas through the gaps.
Air knives of the present invention can be manufactured using any material suitable
for the intended application. An appropriate material can be determined without undue
experimentation. Typically, air knives utilized in a ("TiCl4") production process will be
manufactured from a corrosion resistant alloy such as Inconel 600 or Inconel 601
(commercially available from various steel and alloy distributors).
Gases suitable for use with air knives of the present invention may depend on the
particular application in which the air knife is used. However, appropriate gases can be
determined without undue experimentation. Gases preferred for use with air knives in a
("TiCl4") production process include air, nitrogen, argon, carbon dioxide or any other gas that
will not appreciably react under the conditions prevailing in the air knife.
While the present invention has been described in detail with respect to specific
embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an
understanding of the foregoing, may readily conceive of alterations to, variations of, and
equivalents to these embodiments. For example, air knives of the present invention can be
5 advantageously utilized in applications in addition to the production of ("TiCl4") It is within the
scope of the present invention to utilize the novel air knives of the presenfinvention in many
applications benefiting from the present invention's ability to reduce buildup of materials
during transport from one vessel to another, such as through a tube or pipe. Accordingly, the
scope of the present invention should be assessed as that of the appended claims and any
10 equivalents thereto.
WE CLAIM :
1. An air knife, comprising:
a plurality of overlapping wall sections defining a passage having a
circumference, the passage being adapted to allow solid materials to pass
through the air knife in a first direction;
at least two of the plurality of the overlapping wall sections forming a gap
between them, the gap facing in the first direction; and
at least one gas intake connected to the gap in a manner causing gas
entering the intake to pass through the gap and into the passage along the
circumference of the passage.
2. The air knife as claimed in claim 1, wherein the circumference is circular.
3. The air knife as claimed in claim 1, wherein the gap is no more than 0.18
centimeters.
4. The air knife as claimed in claim 1, wherein the gap is no more than 0.13
centimeters.
5. The air knife as claimed in claim 1, wherein the air knife is connected to a
cyclone separator by a pipe.
6. The air knife as claimed in claim 5, wherein the cyclone separator
separates hygroscopic solids from gases.
7. The air knife as claimed in claim 1, wherein the air knife is attached to a
suspension vessel adapted to receive solids including hygroscopic solids from a
cyclone separator.
8. The air knife as claimed in claim 7, wherein the suspension vessel
encloses a high-humidity environment.
9. A method of reducing solids buildup at the entrance of a vessel, by
employing an air knife as claimed in claim 1 to said vessel, said method
comprising the steps of:
allowing solid materials to pass through a passage defined by the plurality
of overlapping wall sections of the air knife, in a first direction, and
injecting a gas stream through the gap formed between at least two of the
plurality of overlapping wall sections of the air knife, in the said first direction,
along which the solid materials pass through said passage.
10. A method as claimed in claim 9, wherein buildup of hygroscopic solid
material is reduced.
11. A method as claimed in claim 9, wherein buildup of cyclone dust from a
cyclone separator is reduced.
12. A method as claimed in claim 10 or 11, wherein the air knife is positioned
to reduce solids buildup from exposure of the solids to a downstream higher-
humidity environment.
13. A method as claimed in claim 9, wherein the gas stream is injected at a
velocity of at least 30 meters per second.
14. A method as claimed in claim 9, wherein the gas stream is injected at a
velocity of at least 60 meters per second.
15. A method as claimed in claim 9, wherein the gas stream is injected at a
velocity of at least 120 meters per second.
Cyclone separators are used for separating solids from a gas/solid
mixtures. The removed solids can collect in piping downstream of the
separator as they encounter cooler surfaces or higher humidity conditions,
complicating their recovery. The invention concerns a circumferential air knife
that can be placed downstream at these susceptible locations. The air knife
(300) [FIG.3] comprises a plurality of overlapping wall sections (308, 310,
312) which define a circumferential passage through which the solids (302)
pass, with at least two of the overlapping wall sections (308, 310 and 310,
312) forming a gap between them facing in the flow direction (306), and a gas
intake (314) connected to the gap so inert gases can be fed through the gap
and along the circumference of the passage. The gases sweep clear the
circumference of the passage in locations susceptible to solids buildup.

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Patent Number

223776

Indian Patent Application Number

01133/KOLNP/2005

PG Journal Number

39/2008

Publication Date

26-Sep-2008

Grant Date

23-Sep-2008

Date of Filing

13-Jun-2005

Name of Patentee

TRONOX LLC

Applicant Address

123 ROBERT S. KERR AVENUE OKLAHOMA CITY

Inventors:

#	Inventor's Name	Inventor's Address
1	FLYNN, HARRY, EUGENE	10001 WEATHERS BROOK LANE, EDMOND, OK 73003
2	MAKER, JOE, BERT	6901 MARIE LANE, GUTHRIE, OK 73044
3	CROWDER, LESLIE, E	175 SHER WOOD DRIVE, COLUMBUS, MS 39705
4	PERKINS, JOHNNY, B	40246 MCDUFFIE CEMENTARY ROAD HAMILTON, MS 39740

PCT International Classification Number

B01D 49/00

PCT International Application Number

PCT/US2003/037443

PCT International Filing date

2003-11-21

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10/318,796	2002-12-13	U.S.A.