WO2013184434A2

WO2013184434A2 - Device and method for dispensing catalyst pellets

Info

Publication number: WO2013184434A2
Application number: PCT/US2013/042849
Authority: WO
Inventors: Clifford Johns; Dennis Mcandrews; Munaf Chasmawala
Original assignee: Extundo Incorporated
Priority date: 2012-06-06
Filing date: 2013-05-28
Publication date: 2013-12-12
Also published as: TW201408364A; WO2013184434A3

Abstract

A device and method for dispensing catalyst pellets from a hopper to a chemical reactor. The hopper receives and holds the catalyst pellets at an elevation above the elevation of the chemical reactor. The flow of the catalyst pellets is controlled so they flow into and through a conduit in a widely spaced-apart arrangement to the chemical reactor. This controlled, spaced-apart flow is created by providing a sieve between a hopper and the conduit having openings small enough that the catalyst pellets form bridges above the openings, and then repeatedly breaking up the bridges in a controlled manner.

Description

Device and Method for Dispensing Catalyst pellets

BACKGROUND

The present invention relates to a device and method for dispensing catalyst pellets to a chemical reactor, such as into a chemical reactor vessel or into the vertical tubes of a chemical reactor vessel.

Many chemical reactors are essentially a large shell and tube heat exchanger vessel, with the reaction occurring inside the tubes and a coolant circulating in the vessel outside the tubes. A chemical reactor vessel also can be a simple tank with a single volume of catalyst inside it, or it may be a single large tube. Some chemical reactions occur in furnace or reformer tubes, which may be a part of a system with 10 to 500 or more such tubes. In any of these reactor vessels, catalyst, typically in the form of pellets (including spacer pellets), may be loaded into the reactor to facilitate the reaction. The pellets are replaced periodically.

The reactor tubes may be quite long, housed in a structure several stories tall, and the catalyst pellets may be transported up several stories to an elevation above the top of the tubes so they may then flow by gravity into the tubes. The catalyst pellets typically are supplied in 2,000 pound (or larger) "super sacks", 55 gallon drums, mini drums, metal bins or plastic bags loaded in pallet-mounted cardboard boxes.

The catalyst pellets may be dispensed onto the reactor tube sheet by flowing down through a large diameter hose. The diameter of the hose is large enough that the catalyst pellets do not bridge inside the hose. However, the hose is very heavy and difficult to handle, since it is essentially filled with catalyst. Also, the catalyst pellets rub against each other, abrade and crush each other as they pass through the hose, creating dust.

Once the catalyst pellets are dispensed from the hose, they are then carefully loaded into each reactor tube (there may be several thousand tubes in a single reactor) to try to uniformly fill each tube. Summary

The present invention relates to a device and method for controlled and gentle dispensing of catalyst pellets.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic of the upper portion of a reactor vessel when dispensing catalyst into the reactor vessel in the prior art;

Figure 1 A is a schematic of the reactor vessel of Figure 1 , showing the vertical tubes;

Figure 2 is a schematic, similar to that of Figure 1 , but when dispensing catalyst into the reactor vessel using an embodiment of a pellet dispensing device made in accordance with the present invention;

Figure 2A is a top view looking down on the upper and lower plates of Figure 2;

Figure 2B is the same as Figure 2A but showing an alternative embodiment of the upper plate;

Figure 2C is a section view of the upper and lower plates of Figure 2, with pellets bridged above the plates;

Figure 2D is the same view as Figure 2C but after the upper plate has shifted position and broken the bridge;

Figure 2E is a section view through the upper plate of Figure 2;

Figure 3 is a more detailed side view of the de-dusting adapter of Figure 2; Figure 4 is a view along line 44-44 of Figure 3;

Figure 5 is a schematic, similar to Figure 2, but for a fully automatic arrangement for dispensing of catalyst into the reactor vessel and loading of the catalyst into the reactor tubes;

Figure 6 is a schematic, similar to Figure 5, but with the discharge hose of the device in a fully extended position;

Figure 7 is a view along line 47-47 of Figure 5, with tube openings omitted for clarity;

Figure 8 is a view similar to Figure 7, but for a different arrangement for a cord retracting mechanism;

Figure 9 is schematic plan view of the tubesheet of Figure 7 showing one possible tracking pattern for the lightweight hose as it distributes catalyst pellets onto the surface of the tubesheet;

Figure 10 is a view similar to Figure 9, but showing in phantom an additional tracking pattern to provide a substantially uninterrupted flow of catalyst pellets onto the surface of the tubesheet;

Figure 1 1 A is a schematic similar to Figure 5, showing the loading device being used to load catalyst into a fixed bed reactor;

Figure 1 1 B is a schematic similar to Figure 1 1 A, showing a first, horizontal catalyst bed level in phantom and a second catalyst bed level in solid showing an undesirable skewed condition;

Figure 1 1 C is a schematic similar to Figure 1 1 B, showing a first horizontal catalyst bed level in phantom, a second level, also in phantom, in an undesirable skewed condition, and a third catalyst bed level in a corrected horizontal level achieved via a correction of the operating parameters;

Figure 12 is an illustration of various symbols which may be used when mapping the catalyst bed level in the fixed bed reactor of Figures 1 1A-1 1 C; and

Figure 13 is a schematic of a display which maps the loading profile of the fixed reactor bed of Figures 51A-51 C using the symbols shown in Figure 12.

DESCRIPTION

Figures 1 and 1A depict a typical chemical reactor vessel 10, which is a shell and tube heat exchanger, having an upper tube sheet 12 and a lower tube sheet 14 with a plurality of vertical tubes 16 welded or expanded to the tube sheets 12, 14 to form a tightly packed tube bundle. There may be from one to many hundreds or even thousands of cylindrical tubes 16 extending between the tube sheets 12, 14. Each tube 16 has a top end adjacent the upper tube sheet 12 and a bottom end adjacent the lower tube sheet 14, and the tubes 16 are open at both ends, except that there may be a clip at the bottom end to retain catalyst pellets inside the tube. The upper and lower tube sheets 12, 14 have openings that are the size of the outside diameter of the tubes 16, with each tube 16 located in its respective openings in the tube sheets 12, 14.

The vessel 10 includes a top dome (or top head) 13 and a bottom dome (or bottom head) 15, as well as manways 17 for access to the tube sheets 12, 14 inside the vessel 10. The manways are closed during operation of the reactor but are opened for access, such as during catalyst handling. In this instance, the tubes 16 are filled with catalyst pellets, which facilitate the chemical reaction. (It may be noted that similarly-shaped shell and tube heat exchangers may be used for other purposes, such as for a boiler or other heat exchanger.)

This particular reactor vessel 10 is fairly typical. Its tubes may range in length from 5 feet to 65 feet, and it may be surrounded by a structural steel skid or framework (not shown), which includes stairways or elevators for access to the tube sheet levels of the reactor vessel 10 as well as access to intermediate levels and to a topmost level which may be located at or near the level of the top opening of the reactor vessel 10. On a regular basis, which can be every 2 to 48 months or longer, as the catalyst becomes less efficient, less productive, or "poisoned", it is changed out, with the old catalyst being removed and a new charge of catalyst being installed in the tubes 16 of the reactor vessel 10. Catalyst handling also may have to be done on an emergency basis, on an unplanned and usually undesirable schedule.

A catalyst change operation involves a complete shutdown of the reactor, resulting in considerable cost due to lost production. (The dispensing devices shown and described herein may be used both for the initial loading of a new reactor and for catalyst change operations.) It is desirable to minimize the amount of time required for the catalyst change operation in order to minimize the lost production and accompanying cost caused by the reactor shutdown. Device used for dispensing and de-dusting catalyst

As explained earlier, in the background section, the reactor tubes may be quite long, housed in a structure several stories tall, and the catalyst pellets may be transported up several stories to an elevation above the top of the tubes so they may then flow by gravity into the tubes. The catalyst pellets typically are supplied in 2,000 pound (or larger) "super sacks", 55 gallon drums, mini drums, metal bins or plastic bags loaded in pallet-mounted cardboard boxes.

Figure 1 is a broken away schematic of the transportation and dispensing of catalyst pellets from a super sack 210, as practiced in the prior art. The super sack 210 is picked up and supported above the reactor vessel 10 by a crane 212. A heavy duty hose 214 (typically a 4 inch to 6 inch diameter hose) is connected to the bottom of the super sack 210 and extends through a top opening 216 in the top flange 218 of the reactor vessel 10. Personnel (not shown) standing on the upper tube sheet 12 of the reactor vessel 10 manually handle the hose 214 inside the reactor vessel 10 to load the catalyst pellets from the super sack 210 onto a template or onto loading sleeves (not shown) placed on top of the upper tube sheet 12.

The hose 214 becomes full of catalyst pellets as the operator chokes off the free end of the hose 214 to regulate the flow of catalyst onto the tube sheet 12. This makes the hose 214 very heavy and very difficult to move around to various positions within the reactor. This also generates a large amount of dust due to the abrasion of the catalyst both in the super sack 210 and in the hose 214. In addition, the catalyst pellets tend to segregate themselves by size as they come out of the super sack 210, which prevents consistent loading into the reactor tubes.

Figures 2-4 show a device 220 for dispensing catalyst pellets from a super sack, or from any other container, to a delivery point in the reactor vessel 10. The catalyst dispensing device 220 includes a hopper 222 preferably sized to handle at least all the contents of the container being emptied, such as the 2,000 pounds of catalyst in a super sack. This hopper 222 rests atop a funnel-shaped transition piece 224, which necks down to the smaller diameter of a de-dusting adapter 225, which connects the transition piece 224 to a flexible hose (or conduit) 226. It should be noted that the diameter of the hopper 22, of the de-dusting adapter 225 and of the conduit 226 are many times the diameter of the catalyst pellets that are being dispensed (at least eight times the largest dimension of the catalyst pellets), so there is no bridging of catalyst pellets as they pass through the hopper 22, the funnel 224, the adapter 225, and the conduit 226. As explained in more detail below, the hose or conduit 226 may be a flexible, light duty hose, as it is not intended for this hose 226 to be fully loaded with catalyst pellets. The flexible and light-weight nature of the hose 226, and the fact that it is not completely filled up with catalyst pellets, makes it easy to move the hose around to where the catalyst is needed within the reactor.

Between the hopper 222 and the transition piece 224 is a reciprocating plate 228, which has a plurality of through openings 36, which are evenly spaced over the entire plate 228. Only a few of the openings 36 are shown in Figure 2A for clarity, but Figure 2E shows that the openings 36 are arranged over the entire plate 228. Linear motion drive devices 230 are used to cause the plate 228 to reciprocate. The drive devices 230 may cause the plate 228 to reciprocate back and forth in a linear horizontal direction, or a plurality of drive devices 230 may be arranged to allow various horizontal motions of the plate 228, such as in an oval, circular, star-shaped, or other pattern, as shown in Figures 12A-12H of US Publication 201 1 -0283666, published November 24, 201 1 . The reciprocating plate (upper plate) 228 lies on top of a second plate (lower plate) 232. Both the upper and lower plates 228, 232 are flat and are oriented in the horizontal direction. This second plate 232 has its own linear motion drive 234. The second plate 232 also defines a plurality of through openings 34, each of which substantially aligns with a corresponding opening in the upper reciprocating plate 228 when the second plate 232 is in a first position.

However, when the linear motion drive 234 of the second plate 232 is actuated, the second plate 232 moves to a second position, wherein each of the openings on the second plate 232 is in complete misalignment with its corresponding through opening on the reciprocating upper plate 228. When it is in the second, non-aligned position, the second plate 232 acts as a positive shut-off valve to interrupt all flow of catalyst pellets from the hopper 222 to the hose or conduit 226.

The openings 34 in the second plate 232 have a diameter that is four times the largest dimension of the catalyst pellets or less, or of a size that causes bridging of the catalyst pellets above the openings 34 in the second plate 232. (The second plate 232 may be referred to as a sieve, or the upper and lower plates together 228, 232 may be referred to as a sieve.) The openings 36 in the reciprocating upper plate 228 are preferably somewhat larger than the openings in the second plate 232. A large number of openings in the second plate 232 creates a large number of individual pathways by which catalyst pellets pass from the hopper 222 into the large diameter conduit 226.

Figure 2B shows an alternate embodiment of the upper plate 228', in which the openings 36' of the upper plate 228' are lobed, with each upper plate opening 36' overlying three of the openings 34 in the lower plate 232.

Figures 2C and 2D show how catalyst particles 18 bridge above the openings

34 and how the bridges are broken, allowing a catalyst particle 18A to fall through the aligned openings 36, 34 as the upper plate 228 reciprocates relative to the lower plate 232.

As shown in Figure 2C, some of the catalyst pellets 18 that are forming a bridge are in contact with the top surface of the lower plate 232. Figure 2D shows what happens when the upper plate 228 moves to the left. The vertical edge of the opening 36 in the upper plate 228 contacts the catalyst pellet 18A, which is resting on the top surface of the lower plate 232 and pushes it to the left, into the opening 34 of the lower plate 232, so that pellet 18A falls through the openings 36 and 34. Since the pellet 18A was supporting the bridge adjacent to the opening 36, its movement relative to the other catalyst pellets 18 causes the bridge to fall and allows other catalyst pellets 18 to fall through the openings 36, 34 until another bridge is formed adjacent to the opening 36, which will occur relatively quickly. This process is repeated as the upper plate 228 reciprocates relative to the lower plate 232, repeatedly breaking the bridges and allowing the catalyst particles 18 to fall through the aligned openings 36, 34 in a controlled manner. The hopper 222 includes a hinged, watertight cover 236, which can be opened for bulk dispensing of catalyst pellets as from a super sack. A second, smaller cover 238 may be used to load smaller quantities of catalyst pellets (as from small boxes or bags) or for continuous dispensing of catalyst pellets (as through a hose). In a preferred embodiment, both of these covers 236, 238 are watertight to allow continued dispensing of catalyst pellets into the reactor vessel 10 even in adverse weather conditions. For instance, one or more super sacks may be emptied into the hopper 222 via the cover 236 while it is not raining. Then, even if it starts to rain, the hopper 222 may be unloaded into the reactor vessel 10. A weather shield 240 may be installed over the de-dusting adapter 225 and the flange connection 218 for further assurance of water-tightness, if required.

Referring now to Figures 3 and 4, the de-dusting adapter 225 has a cylindrical wall 227 equidistant about an imaginary vertical axis, and that cylindrical wall 227 has an outer surface and an inner surface. A nozzle 248 extends horizontally from a large, circular opening 249 in the cylindrical wall 227. The cylindrical wall 227 defines a plurality of radially-arranged slotted openings 242 for admitting air into the interior of the cylinder 227, as shown by the arrows 244 in Figure 4. A partial cylindrical baffle wall 246 creates a tortuous path 247 for the air being drawn through the de-dusting adapter 225 to ensure that only lighter-weight dust particles are pulled out of the de-dusting adapter 225 via a vacuum source (not shown) connected to the nozzle 248 projecting from one side of the de-dusting adapter 225. Note that the baffle 246 could be replaced by a fairly tight wire mesh screen which covers the opening 249 into the nozzle 248, such that only small dust particles are extracted from the de-dusting adapter 225 while larger catalyst pellets are rejected and allowed to fall into the hose 226.

It should also be noted that, even if there is no provision for slotted openings 242 around the de-dusting adapter 225, air may be drawn up through the free end of the hose 226, up through the length of the hose 226, through the dedusting apparatus 225 and out the nozzle 248 to the vacuum source discussed above. In either case, the vacuum level in the vacuum source is adjusted to provide the degree of de-dusting that is desired, vacuuming a stream of gas out of the side of the cylinder 227 (which is part of the conduit) as the catalyst pellets flow through the cylinder 227 in order to remove dust from the catalyst pellets.

To operate the catalyst dispensing device 220, the device 220 is first installed onto the top flange 218 of the reactor vessel 10, as shown in Figure 2. Pneumatic air is provided for the linear motion drives 230 of the reciprocating plate 228 as well as for the linear motion drive 234 of the second plate (shut-off plate) 232. The hopper 222 is at least partially filled with catalyst pellets, which enter through the large cover 236 or the small cover 238 while the shut-off plate 232 is in the closed position. A vacuum source is also connected to the nozzle 248 of the de-dusting adapter 225.

Once the personnel are ready and inside the reactor vessel 10, the actuator 234 for the shut-off plate 232 may be actuated to open the path, allowing catalyst pellets to fall from the hopper 222, through openings in both plates 228, 232, to the hose 226. Since the effective diameter of the aligned openings in the upper plate 228 and lower plate 232 are only slightly larger in diameter than the catalyst pellets (usually less than two times the largest dimension of the catalyst pellets), there will be bridging of catalyst pellets above the plates 228, 232. Only a small amount of catalyst pellets will fall through the aligned openings in the plates before bridges of catalyst pellets form in the hopper 222 above the respective openings, preventing more catalyst pellets from falling into the hose or conduit 226. The actuators 230 for the reciprocating upper plate 228 are actuated to provide localized, direct mechanical force to continuously and gently break the bridges forming in the hopper 222, allowing the catalyst pellets to fall continuously through the aligned openings in the upper and lower plates 228, 232 and into the hose 226. This creates a controlled flow of catalyst pellets into the conduit 226, with the catalyst pellets being

homogeneously spaced apart from each other, so they flow with minimal or no contact with each other. This minimizes the opportunity for the catalyst pellets to rub against each other and abrade each other. It also results in the conduit 226 being relatively lightweight and easy to move around.

This spaced-apart flow of the catalyst pellets will be referred to herein as "star flow", since it evokes the image of the stars flowing toward the viewer in a common screen-saver for a computer monitor. In practice, this "star flow" is such that, if one takes a horizontal cross-section across the conduit 226 at any given time as the catalyst pellets are flowing through the conduit, that cross-sectional area will be filled 26% or less by catalyst pellets, with the remainder being open space. This contrasts with the full flow in the prior art conduit of Figure 41 , in which the cross-sectional area would be filled 55% or more with catalyst pellets.

Another way to consider "star flow" is to contrast it with full flow or maximum flow, with full flow or maximum flow being defined as the maximum number or maximum weight of catalyst pellets that can flow through the conduit, and "star flow" being half of the maximum flow or less. In maximum flow, the catalyst pellets are packed together and are in maximum contact with each other as they flow through the conduit, with the conduit being as full of catalyst pellets as it can be. This is the condition in the prior art conduit of Figure 1 . With "star flow", the catalyst pellets are in minimal or no contact with each other and are spaced apart in a homogeneous manner across the cross-section of the conduit as they flow through the conduit. Thus, the weight of catalyst pellets in the conduit as the catalyst pellets are flowing through in a star flow arrangement is half or less of the weight of catalyst pellets in the conduit as the catalyst pellets are flowing through in a typical prior art full flow or maximum flow arrangement.

The operator directs the free end of the hose 226 as required to deposit the de-dusted catalyst pellets at delivery points where they are needed, finding the conduit to be much lighter and easier to handle and encountering far less dust than in the prior art arrangement.

In a preferred embodiment, the operator inside the reactor vessel 10 has direct control of the pneumatic air to the linear motion drive 234 of the shut-off plate 232 in order to stop the flow of catalyst pellets to the upper tube sheet 12 of the reactor vessel 10. Preferably, the operator also has direct control of the pneumatics to the linear motion drives 230 of the reciprocating plate 228 so he can regulate the frequency of reciprocation of the plate 228, which regulates the flow of catalyst pellets by regulating the frequency with which the bridges impeding the flow of catalyst pellets are broken. In one extreme, if the frequency of reciprocation of the plate 228 is reduced to zero (the air to the linear motion drives 230 is shut off), the flow of catalyst pellets will quickly stop due to bridging of catalyst above the openings in the reciprocating upper plate 228.

Using the catalyst dispensing device 220, the hopper 222 is emptied evenly, gradually, gently, and from the bottom. That is, the catalyst pellets closest to the reciprocating plate 228 are always the first to be drawn out of the hopper 222. A metered flow rate of catalyst pellets, controlled by the operator, flows down through the transition piece 224 and through the de-dusting adapter 225, where the dust generated thus far by the handling of the catalyst pellets is removed, as discussed earlier. The de-dusted catalyst pellets proceed down the hose 226 to where the operator wants them to be deposited. Since the flow rate can be controlled by the operator, and the flow of catalyst pellets can be stopped at the bottom of the hopper 222 by the operator (either by stopping the reciprocation of the upper plate 228 or by actuating the actuator 234 for the lower, shut-off plate 232), the hose 226 need not ever be full of catalyst pellets. This makes it much easier for the operator to handle the hose 226, and a lighter weight hose can be used than is the case with the prior art arrangement shown in Figure 1 .

Device used for dispensing and de-dusting catalyst and for fully automatic loading of catalyst into a chemical reactor

As explained in the previous section, the catalyst unloading device 220 may be used for dispensing catalyst pellets from a super sack, or from any other container, to a delivery point in the reactor vessel 10. Personnel inside the reactor vessel 10 move the lightweight hose 226 (See Figure 2) to deposit catalyst pellets in a desired pattern to load the reactor tubes. Also, as indicated earlier, catalyst pellets may be deposited directly over the tubesheet 12, or over a plurality of loading sleeves installed in the openings of the tubes in the tubesheet 12, or over a template placed over the tubesheet 12, or over a catalyst loading device.

It should be noted that chemical reactors have many different configurations. Many chemical reactors have a very large plurality of small diameter tubes extending between the upper and lower tubesheets, as shown in Figures 1 and 2. Other chemical reactors have a smaller number of larger diameter tubes. Still other chemical reactors, known as fixed-bed reactors, may have no tubes at all. Instead, the entire chemical reactor vessel is filled with one or more layers of catalyst pellets. The different layers usually contain different types of catalyst, and some of the layers may be inert catalyst pellets which separate two layers of active catalyst pellets.

Loading catalyst pellets into a fixed bed reactor is different from loading catalyst pellets in a multi-tube reactor in that there is no concern about the catalyst pellets bridging in the tubes of a fixed bed reactor, since the diameter of the fixed bed reactor is many times larger than the diameter of the catalyst pellets. However, it is desirable to deposit the catalyst pellets evenly across the cross-sectional profile of the vessel so that, when one layer of catalyst pellets has been loaded and the vessel is ready for another, different layer of catalyst pellets, the depth of the bed of catalyst (the loading profile) is the same throughout the vessel. It is undesirable to have peaks, valleys, doughnuts, or skewed loading of the catalyst pellets.

Catalyst loading of fixed bed reactor vessels is often accomplished by pouring catalyst pellets onto a broadcast spreader (such as the broadcast spinner, item 68 on Figure 5 of U. S. Patent 7,695,215, Method and System for Broadcast Sediment Capping, "Buhr", dated April 13, 2010, which is hereby incorporated herein by reference). For a broadcast spreader to operate correctly, it is important that the outlet of the hose feeding the spreader (and the spreader itself) be at the geometric center of the vessel and that the hose be substantially vertical (plumb). If there are any obstacles that impede the even distribution of catalyst pellets on the surface of the vessel (for example, any structural members extending vertically along the height of the vessel), it may become necessary to reverse the direction of rotation of the spreader head to ensure an even fill around the obstruction.

Figures 5-1 1 C show a loading device 250 for fully automatic loading of catalyst pellets onto a chemical reactor 10. As will be explained later, this loading device 250 may be utilized in multi-tube chemical reactors as well as in fixed bed reactors.

Comparing Figures 2 and 5 it may be appreciated that the loading device 250 of Figure 5 includes substantially all the elements of the loading device 220 of Figure 2, including the upper and lower reciprocating plates 228, 232 with a plurality of openings for flow control. The weather shield 240 of Figure 2 has been omitted for clarity in Figure 5). The main difference is that the distal end 252 of the lightweight hose 226 is now tethered to the walls of the reactor vessel 10 via a collar 254 and cords 256, as described in more detail below.

Referring to Figures 5 and 7, a collar 254 encircles the distal end 252 of the lightweight hose 226. A plurality of cords 256 extends from the collar 254 to corresponding retracting reels 258, which are secured at or near the walls of the reactor vessel 10. In the embodiment shown in Figure 7, three cords 256 extend from the collar 254 and are anchored at points that are equidistant from each other around the perimeter of the collar 254, with one end of each cord 256 secured to the collar 254 and the other end of each cord 256 attached to its corresponding retracting reel 258. The retracting reels 258 also are substantially equidistant from each other around the perimeter of the wall of the reactor vessel 10.

In the embodiment shown in Figures 5 and 7, the retracting reels 258 are secured to the wall of the reactor vessel 10. They may be secured by a permanent means, such as by a bracket welded to the inner surface of the reactor vessel 10, or they may be secured by a releasable means, such as permanent magnets or electromagnets. The retracting reels 258 need only be mounted in some manner that fixes them relative to the tubesheet 12 of the reactor vessel 10 during the loading process. The retracting reels 258 may, for instance, be secured to the tubesheet 12 or to a device, such as the "mirror" tubesheet, which is in turn secured to the tubesheet 12, or to the wall of the reactor vessel 10.

In this embodiment, the retracting reels 258 are "powered reels", and each retracting reel 258 includes an encoder which is in communication with a controller to enable the controller (not shown) not only to determine the location of the distal end 252 of the lightweight hose 226 relative to the tubesheet 12, but also to actively guide the distal end 252 of the lightweight hose 226 along a programmed path or track 260 (See Figure 49) by powering the appropriate reel 258 to cause that reel 258 to retract or extend its corresponding cord 256.

Even though the cords 256 may attach directly to the lightweight hose 226, preferably in an area adjacent the distal end 252 of the lightweight hose 226, it is preferred for the cords 256 to attach to a collar 254. The collar 254 is able to rotate about the longitudinal axis 270 (See Figure 5) of the lightweight hose 226. The collar 254 may be described as resembling a ball bearing with the inner race of the bearing secured at or near the distal end 252 of the lightweight hose 226. The cords 256 are secured to the outer race of the bearing. Also mounted to the outer race of the bearing (See Figures 5 and 7) are a level 272, an inclinometer 274, and a distance measuring device 276, such as a laser or a LIDAR, mounted on a gimbal arrangement 278 which allows the distance measuring device 276 to be accurately aimed as desired (as explained in more detail later). LIDAR is an acronym for Light Detection and Ranging, an optical remote sensing technology that can measure the distance to a target, often using pulses from a laser.

In this embodiment, the level 272, the inclinometer 274, the distance measuring device 276, and the gimbal arrangement 278 are electronic devices which communicate with a remotely-located controller. Their measurement outputs may be remotely accessed and used as feedback to control the actuator reels 258 and to generate a map of the loading profile, as explained later.

Referring back to Figure 5, the lightweight hose 226 is allowed to telescope up and down over a truncated section of heavier hose or cylinder 264 (shown in phantom). A cord 266 attaches the proximal end 262 of the lightweight hose 226 to a retracting reel 268 secured to the heavier hose 264 (as shown in Figure 5) or to any other structure which is substantially fixed relative to the tubesheet 12. It should be noted that this retracting reel 268 and corresponding cord 266 may be replaced, in some embodiments, by a simple spring (not shown) which allows the lightweight hose 226 to be pulled down (against the spring) as required to reach toward the perimeter of the tubesheet 12, as shown in Figure 6, but which automatically, telescopically retracts the lightweight hose 226 upwardly, over the heavier hose 264 in order to take up the extra length of the lightweight hose 226 when this extra length is not required (as shown in Figure 5).

Figure 8 shows a slightly different arrangement for moving the distal end 252 of the lightweight hose 226. It uses four equidistant retracting reels 258, 258* instead of the three retracting reels 258 shown in Figure 7. In this instance, two of the retracting reels 258* may be replaced by springs, if desired, which exert a biasing force that pulls the distal end 252 of the lightweight hose 226 toward the position on the wall where the respective spring 258* is mounted. It should be noted that the arrangement may include any number of retracting reels 258 or springs 258* to ensure that the distal end 252 of the lightweight hose 226 follows the desired track 260 (See Figure 9).

The track 260 may be pre-programmed into a controller, not shown, so that the controller can ensure that the distal end 252 of the lightweight hose 226 follows this track 260 based on inputs the controller receives from encoders in the retracting reels 258. It should be noted that the controller may receive other inputs in order to ascertain the position of the distal end 252 of the lightweight hose 226 and may use these inputs to extend or retract the encoded retracting reels 258 in order to move the distal end 252 of the lightweight hose 226 along the desired track 260. For instance, a laser may be used to determine the distance between the distal end 252 of the lightweight hose 226 and fixed points on the tubesheet 12 (or mirror tubesheet), and this information can then be used to actuate the retracting reels 258 in order to move the distal end 252 of the lightweight hose 226 along the desired track 260.

Figure 10 shows a different path which may be followed by the distal end 252 of the lightweight hose 226. It includes the original path 260 of Figure 9, and it adds a second path 260* which complements the original path 260 and allows

uninterrupted deposition of catalyst pellets on the tubesheet 12. The combined paths 260, 260* may be repeated seamlessly until all the tubes in the reactor vessel 10 have been loaded with catalyst pellets.

To operate the loading device 250 in a conventional chemical reactor 10 having a plurality of reactor tubes 16 which are to be loaded with catalyst pellets, the catalyst pellets are first unloaded from a super sack (or other container) into the hopper 222, and from there the catalyst pellets are evenly unloaded from the bottom of the hopper 222 and through a de-dusting arrangement using the mechanism 220 described earlier with respect to Figure 2. The unloading of the catalyst pellets from the bottom of the hopper 222 is controlled by controlling the frequency of

reciprocation of the of the plate 228, which regulates the flow of catalyst pellets by regulating the frequency with which the bridges impeding the flow of catalyst pellets are broken, as was discussed earlier. In a preferred method of operation, the flow of catalyst pellets is controlled so as to obtain a star flow as opposed to a flooded flow (or plug flow) which is characterized by the hose 226 being packed or filled with catalyst pellets which abut each other, as explained earlier. Since there are far fewer catalyst pellets at any given time within the hose 226 using the star flow, the total weight of the hose 226 and of the catalyst pellets flowing through the hose 226 is much less than with flooded flow, making it much easier to move the distal end 252 of the hose 226 around within the reactor 10.

Referring now to Figure 6, the distal end 252 of the hose 226 is moved along a path 260 (See Figure 9) over the tubesheet 12 in order to deposit catalyst pellets. In one embodiment, the tubesheet 12 is covered by a mirror tubesheet that duplicates the tubesheet 12 itself in terms of the location of the openings of the reactor tubes 16. The reactor tubes 16 may be loaded with catalyst pellets by using this mirror tubesheet as a pristine starting surface, uninterrupted by any irregularities on the tubesheet 12. A loading device may be placed directly over the mirror tubesheet for loading catalyst pellets into the reactor tubes 16, or loading sleeves may be installed in the openings mirror tubesheet with the loading device placed over these loading sleeves.

The catalyst pellets will have been uniformly emptied from the hopper 222, de-dusted in the process of being transferred to the tubesheet 12, and evenly deposited over the tubesheet 12 following a pre-programmed path 260.

Fixed-Bed Reactor Loading Figures 1 1A-C, 12, and 13 show the loading device 250 of Figure 5 being used for loading a fixed-bed reactor 10*. Referring to Figure 1 1A, the fixed-bed reactor 10* is a substantially empty vessel which, in this view, is partially loaded with catalyst pellets to the level indicated by the line 280. As discussed earlier, a broadcast spreader 282 is suspended at the geometric center of the fixed-bed reactor 10*, for rotation about the longitudinal axis 270 of the catalyst pellet delivery hose 226. Catalyst pellets are delivered to the broadcast spreader 282 via the hose 226, creating a star flow, and are then evenly broadcast, as denoted by the dotted lines 284, over the cross-sectional area of the fixed-bed reactor 10*. In order to ensure an even loading profile of the catalyst pellets in the fixed-bed reactor 10* it is important that the broadcast spreader 282 and the hose 226 be substantially in the geometric center of the fixed-bed reactor vessel 10* and that the broadcast spreader 282 is substantially horizontally aligned. Since, in this embodiment, the broadcast spreader 282 is horizontally suspended from the hose 226, it is important that the hose 226 be substantially vertically aligned (that is, the longitudinal axis 270 of the hose 226 should be substantially plumb).

The level 272, mounted on the collar 254 of the hose 226, may be used to ascertain that the broadcast spreader 282 is substantially horizontally aligned. An electronic output from the level 272 is used by the controller (not shown) to actuate the retractable reels 258 in order to extend or retract their respective cords 256 until the level 272 indicates that the broadcast spreader 282 is substantially level

(horizontally aligned).

A distance measuring device 276 mounted on a gimbal arrangement 278 is used to provide an indication of the loading profile 280 of the catalyst pellets in the reactor vessel 10*. The distance measuring device 276 takes a distance reading to each of the points a, b, c, d, e, f, g, h. An inclinometer 274, also mounted on the gimbal arrangement 278, provides an electronic indication of how far the conduit 226 is off of plumb. This information is corrected with the reading from the level 272, as explained later. The controller, given the distance reading for each point a, b, c, d, e, f, g, h as indicated by the distance measuring device 276 (such as a laser beam) and the angle off of plumb as indicated by the inclinometer 274, can then calculate the loading profile 280 across the entire cross-sectional profile of the vessel 10*.

(Namely, the vertical component of the distance "D" from the positioning device 276 to the measured point is equal to the measured length "L" as indicated by the positioning device 276 times the cosine of the angle Ω as measured by the inclinometer 274).

Note that the feed of catalyst pellets may be momentarily halted before the distance measurements "L" at each of the plurality of points a, b, c, d, e, f, g, h are taken to ensure that the laser beam (or LIDAR) does not mistakenly measure the distance to a falling catalyst pellet during a measurement, thus giving an erroneous distance "L" reading. However, the readings may be taken "on the fly", without halting the feed of catalyst pellets, by incorporating an algorithm to ensure that the laser beam (or LIDAR) is not measuring the distance to a falling catalyst pellet. For example, a series of distance measurements may be taken over a very small time interval (for example, three measurements within a one second interval) and the measurements are then compared to ensure that they all match within a very small range (for instance, within the size of one or two catalyst pellets). If one or more of the measurements were taken off of a falling catalyst pellet, then the measurements will show a much larger variance than the specified range. The readings will then be deemed suspect and an additional set of readings will be taken for the point in question.

Also note that, for clarity, only one set of level 272, inclinometer 274, positioning device 276, and gimbal arrangement 278 is shown in the figures.

However, it may be desirable to provide more than one set, preferably evenly spaced along the perimeter of the collar 254 in order to generate a more accurate map of the loading profile of the vessel 10*, such as the readings in the x, y, and z directions shown in the upper set of measurements of the map 286 of Figure 13.

Figure 1 1 B shows the reactor vessel 10* of Figure 1 1 A but at a later point in time, when more catalyst pellets have been loaded into the vessel 10*. The new loading profile 280' is shown to be undesirably skewed so it is at a higher elevation on the right than on the left. To correct this undesirable condition, the broadcast spreader 282 may be tilted, as shown in Figure 1 1 C, to bring the loading profile 280" back to horizontal. (Note that this is only given as an example. It may be necessary to tilt the broadcast spreader 282 in a different direction, or to take some other corrective action, to correct this particular undesirable condition).

Figure 13 shows a loading profile map 286 which may be generated to provide a graphical display of the loading profile of the vessel 10* at several stages of catalyst loading. The map 286 shows the results from only two points in time but the map could be generated to show the loading profile at any one or more points in time. Figure 12 provides the key for the symbols used in the map 286 of Figure 13. The vertical line 288 is an indication of the range allowed within the specification. For instance, the specification may allow the height to vary ¾" above or below the target elevation before the measurement is considered to be out of spec. The vertical line with a clear triangle pointing down 290 indicates that the measurement at the point taken is below the target elevation but still within the range allowed by the specification. The location of the tip of the arrow relative to the line provides a quantitative indication of the extent to which the measurement is below the target elevation within the allowable range. In this instance the reading is low by approximately 60% of the allowable range. The vertical line with a solid triangle pointing up 292 indicates that the measurement is above the target elevation but still within the allowable range. In this instance the reading is high by approximately 80% of the allowable range. The solid diamond shaped symbol 294 indicates the measurement is high and outside of the allowable range. The clear diamond shaped symbol 296 indicates the measurement is low and outside of the allowable range. Finally, the cross-hatched circle 298 indicates that the measurement is substantially at the target elevation (at the threshold of the target elevation).

Referring again to Figure 13, the map 286 shows the measurements taken at two different points in time, when the pellet level is at two different elevations. At the lower elevation, the measurement at point "a" is at the specification elevation, at points "b" and 'c" the measurements are below the target elevation at approximately 50% of the allowable range, at points "d" and "g" the measurements are above the target elevation at approximately 50% of the allowable range, and at points "e" and "f the measurements are above the target elevation at approximately 100% of the allowable range.

The line 300 represents the centerline of the vessel 10*. The dotted line 302 represents the actual centerline of the broadcast spreader 282, and the individual, sloped, line segments 303 represent the degree to which the axis of the broadcast spreader 282 is tilted relative to plumb (Note that these line segments 303 are not shown all the way up to the upper elevation measurement. The line segments 303 in the upper portion are omitted for clarity so that the dotted line 302 representing the actual centerline of the broadcast spreader 282 can be readily visible). It should be obvious that the broadcast spreader 282 can be moved off-center while remaining horizontal, or it can remain in the geometric center of the vessel 10* while being tilted, or it can both be moved off of the geometric center of the vessel 10* and it can be tilted in any direction about its axis of rotation in order to address any irregularity in the loading profile of the vessel 10*. The line 304 is a visual indication of the centerline correction or offset of the centerline of the broadcast spreader 282 relative to the centerline of the vessel 10*.

The centerline offset 304 of the broadcast spreader 282 is caused by the extension or retraction of the cords 256 by their respective retraction reels 258, which is controlled by the controller. The broadcast spreader 282 is internally supported for rotation by the hose 226. A similar extension and retraction

mechanism can be used to tilt the shaft which rotationally supports the broadcast spreader 282 in order to cause the desired degree of tilt of the broadcast spreader 282, or the hose 226 may be tilted, as shown in Figure 1 1 C, for a similar effect. In the event that the hose 226 is tilted, the level 272 provides an indication of the degree of tilt of the hose 226.

In order to load the vessel 10* of a fixed-bed reactor with catalyst pellets, the procedure is similar to that discussed earlier with respect to loading reactor tubes in the vessel 10 (See Figure 5), except that, in this instance, there are no reactor tubes to load so there is no template and no loading sleeves. The reactor is set up initially as shown in Figure 1 1 A, with the broadcast spreader 282 in the geometric center of the vessel 10*. The broadcast spreader 282 is started rotating and the catalyst pellets are started dropping from the hopper 222 through the loading device 220, as discussed with respect to Figure 2, to establish a star-field flow of de-dusted catalyst pellets descending onto the broadcast spreader 282.

Several parameters can be adjusted in the arrangement shown in Figure 1 1 A in order to establish the desired loading profile 280 in the vessel 10*. These parameters include the rotational speed and direction of the broadcast spreader 282, the height of the broadcast spreader 282 above the loading profile 280, the degree of offset 304 (See Figure 13) of the centerline 302 of the broadcast spreader 282 relative to the centerline 300 of the vessel 10*, and the degree of tilt 303 of the broadcast spreader 282 relative to vertical. Referring to Figure 1 1 B, as the loading progresses, it may become apparent that the loading profile 280' is skewed or otherwise does not conform to the desired loading profile (which typically will be a flat and smooth loading profile across the entire cross-section of the vessel 10*). The continuous readings of the height of the catalyst pellets at a plurality of points along the loading profile 280' are displayed in a map 286 (See Figure 13) so that the operator can immediately see the loading profile at any elevation. The operator can also see the trend of the loading profile as he changes some (or all) of the parameters so he can determine whether the changes he has made are correcting the loading profile anomaly or exacerbating the condition.

As shown in Figure 1 1 C, the correction initiated by the operator, which in this instance included tilting the broadcast spreader 282, corrected the loading profile 280 " back to a desirable flat and unskewed condition. It should be noted that the controller may be programmed to actuate the retracting reel 268 so as to maintain a constant height of the broadcast spreader 282 above the loading profile of the catalyst pellets in the vessel 10*. Of course, this condition can be over-ridden by the operator if he deems it necessary to correct an anomalous loading condition.

As the operator becomes more proficient with the use of the loading device 250, and with the aid of the map 286 of Figure 13, he will be able to look at the trend of the loading profile and he will know what corrections or changes to make to the operating parameters to anticipate any problems and maintain a desirable loading profile.

It also should be noted that, while the use of upper and lower plates with openings is preferred, any of the methods of breaking up bridges above an opening that have been described in U.S. Publication 201 10283666 with respect to bridges above the openings into the reactor tubes may be used to create the star flow from the large hopper into the large diameter conduit, to meter the flow of catalyst pellets through the plurality of openings and into the large diameter conduit by allowing bridges to form and then repeatedly breaking up the bridges in a controlled manner.

It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention as claimed.

Claims

What is claimed is:

1 . A method for dispensing catalyst pellets to a chemical reactor, comprising the steps of:

providing a hopper for holding a plurality of catalyst pellets at an elevation above the chemical reactor;

loading a plurality of catalyst pellets into the hopper;

providing a large diameter open conduit through which the catalyst pellets pass in order to flow from the hopper to the chemical reactor, with the diameter of the conduit being at least eight times the largest dimension of the catalyst pellets; providing a sieve between the hopper and the conduit defining a plurality of openings that are small enough relative to the size of the catalyst pellets so that the catalyst pellets form bridges above the sieve; and

repeatedly breaking the bridges to allow the catalyst pellets to flow through the openings in a controlled manner to form a flow in which the catalyst pellets are separated from each other in a homogeneous manner and have minimal or no contact with each other as they fall through the open conduit.

2. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 1 , wherein a cross-section taken through the conduit as the catalyst pellets are flowing through the conduit has 26% or less of the cross-sectional area occupied by catalyst pellets.

3. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 2, wherein the sieve comprises upper and lower plates, with the upper plate lying on top of the lower plate, wherein said upper plate defines a plurality of upper openings and the lower plate defines a plurality of lower openings which can be aligned with respective upper openings, wherein, when the upper and lower plates are stationary, with the upper and lower openings aligned, the upper and lower openings together form the plurality of openings that are small enough relative to the size of the catalyst pellets so that the catalyst pellets form bridges above the openings; and wherein the step of breaking up the bridges includes moving at least one of the upper and lower plates parallel to the other of the upper and lower plates, thereby breaking up the bridges of catalyst pellets above the upper openings and further including the step of allowing the catalyst pellets to flow through the aligned upper and lower openings and then into and through the conduit.

4. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 2, and further comprising the step of vacuuming a stream of gas out of the side of the conduit as the catalyst pellets flow through the conduit to remove dust from the catalyst pellets.

5. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 3, and further comprising the step of moving at least one of the upper and lower plates parallel to the other of the upper and lower plates so that the upper and lower openings are out of alignment with each other, thereby preventing the flow of catalyst pellets from the hopper to the conduit.

6. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 5, and further comprising the steps of providing a cover on top of the hopper and opening the cover to load catalyst pellets into the hopper.

7. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 6, and further comprising the step of vacuuming a stream of gas out of the side of the conduit as the catalyst pellets flow through the conduit to remove dust from the catalyst pellets.

8. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 5, wherein said upper and lower plates are planar plates, oriented horizontally.

9. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 7, wherein said upper and lower plates are planar plates, oriented horizontally.

10. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 1 , wherein the conduit has a first end adjacent to the hopper and a second end at a lower elevation than the first end, and further comprising the step of automatically controlling the movement of the second end of the conduit inside the reactor vessel along a desired path in order to provide uniform loading.

1 1 . A method for dispensing catalyst pellets to a chemical reactor as recited in claim 9, wherein the conduit has a first end adjacent to the hopper and a second end at a lower elevation than the first end, and further comprising the step of automatically controlling the movement of the second end of the conduit inside the reactor vessel along a desired path in order to provide uniform loading.

12. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 1 , wherein a maximum flow rate is defined as the maximum number of catalyst pellets that can pass through the conduit per unit of time, and wherein the flow rate of catalyst pellets as the catalyst pellets are flowing through the conduit is not greater than half of the maximum flow rate.

13. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 12, wherein the sieve includes upper and lower plates, with the upper plate lying on top of the lower plate, said upper and lower plates being located between the hopper and the conduit, wherein said upper plate defines a plurality of upper openings and the lower plate defines a plurality of lower openings which can be aligned with respective upper openings, wherein, when the upper and lower plates are stationary, with the upper and lower openings aligned, the upper and lower openings together form the plurality of openings that are small enough relative to the size of the catalyst pellets so that the catalyst pellets form bridges above the openings; and wherein the step of breaking up the bridges includes moving at least one of the upper and lower plates parallel to the other of the upper and lower plates, and further comprising the step of allowing the catalyst pellets to flow through the aligned upper and lower openings and then into and through the conduit.

14. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 12, and further comprising the step of vacuuming a stream of gas out of the side of the conduit as the catalyst pellets flow through the conduit to remove dust from the catalyst pellets.

15. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 13, and further comprising the step of moving at least one of the upper and lower plates parallel to the other of the upper and lower plates so that the upper and lower openings are out of alignment with each other, thereby preventing the flow of catalyst pellets from the hopper to the conduit.

16. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 15, and further comprising the steps of providing a cover on top of the hopper and opening the cover to load catalyst pellets into the hopper.

17. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 16, and further comprising the step of vacuuming a stream of gas out of the side of the conduit as the catalyst pellets flow through the conduit to remove dust from the catalyst pellets.

18. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 15, wherein said upper and lower plates are planar plates, oriented horizontally.

19. A method for dispensing catalyst pellets to a chemical reactor as recited in claim 17, wherein said upper and lower plates are planar plates, oriented horizontally.