A SILO

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims the benefit of priority to U.S. Provisional Patent

Application No. 62/827,219, entitled High Efficiency Pneumatic Conveying of Granular Material Into a Silo , which was filed on April 01, 2019. The disclosure in the prior application is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

This application relates to high efficiency pneumatic conveying and, more specifically, high efficiency pneumatic conveying of granular material into a silo.

BACKGROUND

Silos are structures that can be used, for example, to store bulk granular material, such as proppant for hydraulic fracturing, cement, salt, fertilizer, grain, coal, woodchips, food products, sawdust, and the like. In this regard, for example, a silo may be placed at a worksite, such as a hydraulic fracturing wellhead, and used to store proppant (sand) to be used in connection with hydraulic fracturing processes. Proppant may be delivered periodically to the worksite with a delivery vehicle where the proppant is unloaded into the silo.

The inventors have recognized the need for improved efficiency with respect to these and other processes. SUMMARY OF THE INVENTION

In one aspect, a system includes a silo for storing granular material, a first inlet conduit that extends into the silo at a first location, and a second inlet conduit that extends into the silo at a second location. The first location and the second location are at different distances from a base of the silo.

In another aspect, a method includes providing a system at a worksite. The system includes a silo for storing granular material, a first inlet conduit that extends into the silo at a first location, and a second inlet conduit that extends into the silo at a second location. The first location and the second location are at different distances from a base of the silo (or height measured from or above grade). The method further includes pneumatically conveying the granular material into the silo through the first inlet conduit until the granular material in the silo reaches a first level, and, subsequently, ceasing the pneumatic conveying of the granular material into the silo through the first inlet conduit, and, instead, pneumatically conveying the granular material into the silo through the second inlet conduit.

In yet another aspect, a system includes a silo and an inlet conduit for conveying granular material into the silo. The inlet conduit includes a first conduit portion that extends in a vertical direction outside the silo, and a second conduit portion outside the silo and above the first conduit portion. The second conduit portion has an internal cross-sectional area that is larger than an internal cross-sectional area of the first conduit portion. The change in diameter of the pipe need not cause the air and product to decelerate. In a typical implementation, the goal is to prevent the air and material from speeding up, i.e., maintain the velocity at or above the minimum level required to keep the product in suspension. Preventing the air from speeding up reduces damage to the product, wear and wasting energy which would otherwise be consumed by friction. Overall, as the air moves from the start (high pressure) to the end of the conveying line (atmospheric pressure) the air is expanding along the entire path. In a pipe with constant diameter, this results in the air velocity increasing all along the pipe. The goal is to vary the pipe diameter to maintain a more-or-less consistent velocity (conveying velocity). Otherwise the increasing velocity might result in energy waste and unnecessary friction.

In some implementations, one or more of the following advantages are present.

For example, in some implementations, the efficiency of pneumatically conveying an amount of granular material from one container into another (e.g., a silo) can be improved considerably.

Additionally, in some implementations, the quality of granular material (e.g., proppant, or sand, for hydraulic fracturing or the like) can be preserved. More specifically, damage to the granular material that may otherwise occur from being conveyed pneumatically, may be avoided or at least reduced.

Moreover, in some implementations, the damage that might otherwise occur to structural parts of the silo or inlet conduits from impingement of high speed granular material thereupon, can be avoided or at least reduced.

Also, in some implementations, the systems disclosed herein are very easy to repair, if needed. In this regard, various parts of the system, including parts of the inlet conduits can be removed, inspected and reinstalled or replaced, as appropriate, with ease. For the inlet conduits, this is easy because every piece of the inlet conduits can be removed and/or replaced without having to access inside the silo. Additionally, in various implementations, any one or more of the foregoing advantages can be realized through a relatively simple, inexpensive configuration and/or by utilizing one or more relatively simple processes.

Other features and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. l is a schematic representation of an exemplary system for receiving and storing granular material.

FIG. 2 is a detailed perspective view showing a portion of one exemplary inlet conduit for the system of FIG. 1.

FIG. 3 A is a schematic, top, partial cross-sectional view of an alternative exemplary system for receiving and storing granular material.

FIG. 3B is a detailed perspective view showing the final portion of one of the inlet conduits from FIG. 3 A.

FIG. 3C is a perspective view showing a turning portion of one of the inlet conduits from FIG. 3 A.

FIG. 3D is a partial perspective view showing part of the final portion 124 of one of the inlet conduits of FIG. 3 A extending through an opening in an angled top surface of the silo.

FIGS. 4A-4C are a time sequence of schematic representations of the system from FIG. 1 being filled with granular material from an external source thereof.

Like reference characters refer to like elements. DETAILED DESCRIPTION

FIG. 1 is a schematic representation of an exemplary system 100 for receiving and storing granular material, such as proppant (e.g., sand for hydraulic fracturing), cement, salt, fertilizer, grain, coal, woodchips, food products, sawdust, etc.

The system 100 includes a silo 102 (for storing the granular material) and multiple inlet conduits 104a-104e (for delivering the granular material into the silo 102). The inlet conduits 104a-104e extend through a sidewall 106 of the silo 102 at different locations, with some of the locations being higher or lower than other locations, relative to a base 108 of the silo (i.e., the external surface of the silo, upon which the silo rests when the silo is oriented to perform its intended storage functionalities). For example, the first and second inlet conduits 104a, 104b extend through the sidewall 106 at a first height HI above the base 108 of the silo 102, the third and fourth inlet conduits 104c, 104d extend through the sidewall 106 at a second height H2 above the base 108 of the silo 102, and the fifth and sixth inlet conduits 104e, 104f extend through the angled top 109 of the silo at a third height H3 above the base 108 of the silo 102. In the illustrated implementation, the first height HI is closest to the base 108, the third height H3 is farthest from the base 108, and the second height H2 is between the first height HI and the third height H3.

For each pair of inlet conduits that enter the silo 102 at the same height (either at HI, at H2, or at H3), the locations where the inlet conduits in that pair extend through the silo 102 are displaced from each about the circumferential perimeter of the sidewall 106 of the silo 102, which is cylindrical where the inlet conduits enter. For example, the first and second inlet conduits 104a, 104b, which enter the silo 102 at height HI, do so at locations that are displaced from each about the circumferential perimeter of the sidewall 106 of the silo 102. Likewise, the third and fourth inlet conduits 104c, 104d, which enter the silo 102 at height H2, do so at locations that are displaced from each about the circumferential perimeter of the sidewall 106 of the silo 102. Similarly, the fifth and sixth inlet conduits 104e, 104f, which enter the silo 102 at height H3, do so at locations that are displaced from each about the circumferential perimeter of the sidewall 106 of the silo 102. The amount of displacement for each pair of inlet conduits (i.e., pair 104a,

104b, pair 104c, 104d, and pair 104e, 104f) in the illustrated implementation is close to 180 degrees about the circumferential perimeter of the sidewall 106 of the silo 102. Thus, in pair 104a, 104b, for example, inlet conduit 104a is extends out of the silo 102 on one side of the silo 102 and the other inlet conduit 104b (circumferentially displayed about 180 degrees) extends out of the silo 102 on an opposite side of the silo 102.

The illustrated configuration, therefore, offers six possible candidate conduits for conveying granular material (e.g., pneumatically) into the silo 102. Typically, in practice, only one of these conduits will be used for conveying granular material into the silo 102 at any given time. All other candidate conduits will typically be plugged or otherwise sealed. That said, in some instances, more than one of the conduits may be used in combination at a given time, but to preserve the advantage, the user would want to use the pair of pipes with outlets at the same height so that both operations can benefit from the minimized vertical conveying. If more than one of the conduits are being used at the same time, typically all of the other conduits will be plugged or otherwise sealed.

Typically, the inlet conduit selected to convey granular material at any given point in time will be the one that: 1) enters the silo 102 as lowest possible height (HI, H2, or H3) while still being able to convey granular material into the silo 102 given the current level of granular material inside the silo 102, and 2) is closest to the source of the granular material being conveyed (e.g., the storage container being unloaded into the silo). Once the selected inlet conduit is no longer able to effectively convey granular material into the silo (e.g., because the level of granular material inside the silo has gotten too high), one of the other higher inlet conduits may be selected instead. Switching between inlet conduits in this manner while pneumatically conveying the granular material into the silo helps to ensure that the pneumatic conveying occurs in a highly efficient manner.

Thus, for example, if a truck carrying a container of proppant for hydraulic fracturing pulled up on the left side of the silo 102 (e.g., near the first, third and fifth inlet conduits 104a, 104c, 104e) and the silo 102 were starting from a completely empty state, then, at least initially, the first inlet conduit 104a might be used to facilitate the transfer (e.g., via pneumatic conveying) of proppant into the silo 102. All other inlet conduits 104b-104f would be plugged or sealed while the first inlet conduit 104a is being used. Since the first inlet conduit 104a enters the silo 102 at a lower height (HI) than some of the other inlet conduits 104c-104f (at H2 or H3), the amount of energy required to lift the proppant into the silo 102 through the first inlet conduit 104a is less than the amount of energy that would be required to lift the proppant into the silo through any of these other inlet conduits 104c-104f (at height H2 or height H3).

Continuing this example, typically, the first inlet conduit 104a is used to convey proppant into the silo 102 until doing so were no longer possible or efficient (e.g., until the level of proppant inside the silo 102 reached a level that started restricting the flow of proppant through the first inlet conduit 104a) or no longer necessary (e.g., until there were no more proppant to convey). If the level of proppant inside the silo 102 reaches a level that starts restricting the flow of proppant through the first inlet conduit 104a and there is still more proppant to convey, then one might switch over to start using an inlet conduit at height H2 (e.g., the third inlet conduit 104c) for conveying proppant into the silo 102. At that point, one would plug or otherwise seal the first inlet conduit 104a. The third inlet conduit 104c (at height H2) is higher than the first inlet conduit 104a (at height HI). Therefore, conveying through the third inlet conduit 104c requires more energy than using the first inlet conduit 104a to convey proppant into the silo 102. Additionally, it takes longer to load a particular quantity of granular material into the silo using higher inlet conduits However, at this point in the example, the first inlet conduit 104a is no longer available to convey proppant into the silo 102. Therefore, the third inlet conduit 104c provides a next best option in terms of efficiency.

In general, significant potential gains in energy efficiency can be achieved by conveying the product to lower heights, rather than wasting energy elevating the product significantly farther than necessary.

The third inlet conduit 104a can be used to convey proppant into the silo 102 until doing so were no longer possible, efficient or necessary. If the level of proppant inside the silo 102 reaches a level that starts restricting the flow of proppant through the third inlet conduit 104c and there is still more proppant to convey, then one might switch over to start using the fifth inlet conduit 104e for conveying proppant into the silo 102. At that point, one would plug or otherwise seal the third inlet conduit 104c. The fifth inlet conduit 104e (at height H3) is higher than the first inlet conduit 104a (at height HI) and the third inlet conduit (at height H2).

Therefore, conveying through the fifth inlet conduit 104e requires more energy than using the first inlet conduit 104a or the third inlet conduit 104c to convey some amount of proppant into the silo 102. However, at this point in the example the first inlet conduit 104a and the third inlet conduit 104c are no longer available. Therefore, using an inlet conduit at height H3 (e.g., the fifth inlet conduit 104c) is the only remaining available option for continuing to convey proppant into the silo 102.

The illustrated silo 102 has a base 108, an angled top 109, and sidewall 106 that extends from the base 108 to the top 109. The silo 102 further has a flared base section 110 that extends in an upward direction from the base 108, a lower cylindrical section 112 that extends in an upward direction from the narrower upper end of the flared base section 110, a flared transition section 114 that extends in an upward direction from the lower cylindrical section 112, and an upper cylindrical section 116 that extends in an upward direction from the wider upper end of the flared transition section 114. The upper cylindrical section 116 has a larger cross-sectional diameter than the lower cylindrical section 112. In the illustrated example, each of the six inlet conduits 104a-104f has a vertical section that is entirely outside the silo; the inlet conduits only extend through the sidewall 106 or the angled top 109 of the silo 102 after turning or

transitioning toward a horizontal direction.

Each of the six inlet conduits 104a-104f in the illustrated implementation has multiple sections including a connection portion 118 that can be connected to receive granular material from a source thereof, a vertical portion 120 that extends in a vertical direction from the flexible connection portion 118, a turning portion 122 above the vertical portion 120 that defines a turn (e.g., a 90 degree turn) in the flow path for air and granular material, and a final portion 124 that extends from the turning portion 122 into the silo 102. In a typical implementation, such as the one shown in FIG. 1, only one part of the final portion 124 of an inlet conduit is inside the silo 102; the rest of the inlet conduits (including, e.g., the connection portion 118, the vertical portion 120, and the turning portion 122, and part of the final portion 124) are all outside the silo 102. In some implementations, the connection portions 118 of the inlet conduits are flexible. This flexibility may allow the connection portions 118 to be routed, as needed, to a

corresponding source of granular material, to which it can be connected. Moreover, the connection portions 118 have distal ends that are open and that can be connected to a source of granular material or can receive a plug or other sealer therein.

The vertical portions 120 of the inlet conduits in the illustrated implementation extend along the outside of the silo in a vertical direction and are supported periodically by support bracket assemblies 126 that are mounted to the outer surface of the sidewall 106 of the silo 102. Each support bracket assembly 126, in the illustrated implementation, has an inner member 128 and three outer members 130. The inner member 128 has an inwardly-facing surface that is curved to follow the circumferential contour of the silo 102. The inner member 128 has an outwardly-facing surface with three indentations that are curved to follow the contours of the vertical portions of three inlet conduits. In some implementations, the inner member 128 is attached (e.g., with adhesive, threaded connector(s), rivet(s), or the like) to the outer surface of the silo 102. Each outer member 130 has an inwardly-facing surface that is curved to follow the contour of a corresponding one of the vertical portions of the inlet conduits. In a typical implementation, the outer members 130 may be attached to the inner member 128 or to the silo 102 with adhesive, threaded connector(s), etc.

Once the support bracket assemblies 126 are in place and assembled, with the inlet conduits passing through them, the inlet conduits are held in a manner that ensures that the vertical portions of the inlet conduits are held, as shown, with a vertical orientation (at least from the lowest support bracket assembly in a run to the highest support bracket assembly in the run). FIG. 2 is a detailed perspective view showing only a portion of one exemplary inlet conduit (e.g., 104a from FIG. 1). In a typical implementation, every inlet conduit to a particular silo would have the same basic configuration as that shown in FIG. 2. The illustrated configuration shows the upper end of the vertical portion 120, the turning portion 122, and part of the final portion 124.

The vertical portion 120 of the inlet conduitl04a, in the illustrated configuration, is a cylindrical pipe.

The turning portion 122 of the inlet conduitl04a, in the illustrated configuration, includes a cylindrical pipe section 132 that is connected by a coupling 134 to the top of the vertical portion 120 of the inlet conduit 104a, an expansion and deceleration chamber 136 above the cylindrical pipe section, and a horizontal portion 138 that extends outward from the expansion and deceleration chamber 136 in a horizontal direction.

In a typical implementation, the cross-sectional area (in a plane that is perpendicular to flow) of the expansion and deceleration chamber 136 is larger than the cross-sectional area (in a plane that is perpendicular to flow) of the vertical portion 120 of the inlet conduitl04a. In various implementations, for example, the cross-sectional area of the expansion and deceleration chamber 136 may be 2 to 4 times larger than the cross-sectional area of the vertical portion 120 of the inlet conduitl04a.

During system operation (e.g., while granular material is being pneumatically conveyed through the inlet conduit 104a), the compressed air moving through the inlet conduit 104a expands. The compressed air tends to expand as it moves through the inlet conduit 104a, accelerating through the fixed cross-sectional area vertical portion 120 of the inlet conduitl04a, for example, as it expands. The increased cross-sectional area in the expansion and deceleration chamber 136 provides a space for the air to continue expanding without continuing to accelerate as the rate it would without the increased cross-sectional area. In some implementations, in fact, the air flow (and the granular material moving along with the flowing air) actually slows down (or begins to decelerate) when the air enters the increased cross-sectional area of the expansion and deceleration chamber 136.

The flowing air and granular material make a 90 degree turn in the turning portion 136 of the inlet conduit 104a. The slowing down of the flowing air and granular material in the expansion and deceleration chamber 136 of the turning portion 136 of the inlet conduit 104a is important because if the granular material is moving too quickly at the 90 degree turn, the granular material may slam into either the upper surface of the turning portion 136 (or other granular material pressed against the upper surface of the turning portion 136). This has the potential to damage or structurally compromise the integrity of the granular material and/or produce highly undesirable dust particles from the granular material. The fact that the flowing air and granular material slows down (or at least does not continue to accelerate as much) in the expansion and deceleration chamber 136 of the turning portion 136 of the inlet conduit 104a helps prevent the granular material from slamming into either the upper surface of the turning portion 136 or granular material pressed against that upper surface.

The horizontal portion 138 that extends out from the expansion and deceleration chamber 136 in a horizontal direction also has a cross-sectional area (in a plane that is perpendicular to flow) that is also larger than the cross-sectional area (in a plane that is perpendicular to flow) of the vertical portion 120 of the inlet conduit 104a. In a typical implementation, the cross- sectional area of the horizontal portion 138 is about 2.5 times larger (+/- 10%) than the cross- sectional area of the vertical portion 120 of the inlet conduit 104a. In one particular example implementation, the vertical portion 120 of the inlet conduit 104a is a 4 inch fill pipe (with a cross-sectional area of 12.56 square inches) and the expansion and deceleration chamber 136 has a square 5.5 inches by 5.5 inches cross-section (with a cross-sectional area of 30.25 inches).

The horizontal portion 138 extends out from an opening in a side surface of the expansion and deceleration chamber 136 below the top of the expansion and deceleration chamber 136. Thus, a portion of the expansion and deceleration chamber 136 extends upward, above where the horizontal portion 138 braches off, to form a pocket 140 (or“dead head”) that is inside the expansion and deceleration chamber 136. This pocket 140 is in line with the flow direction of (and directly above) the vertical portion 120 and is above where the horizontal portion 138 braches off from the expansion and deceleration chamber 136. During system operation (e.g., when granular material is being conveyed through the inlet conduit 104a), the pocket 140 collects and fills up with granular material. Once filled, the pocket 140 tends to remain filled with granular material for at least as long as the air and granular material are moving through the inlet conduit 104a.

The granular material that fills the pocket 140 during system operation helps to minimize the possibility of high speed granular material damaging an upper surface of the expansion and deceleration chamber 136. The granular material that fills the pocket 140 does this by covering the upper surface of the expansion and deceleration chamber 136 thereby preventing the granular material flowing out of the vertical portion 120 of the inlet conduit 104a from striking and abrading or wearing against the upper surface of the expansion and deceleration chamber 136. In a typical implementation, this helps reduce product degradation, reduce wear and extend service life. The granular material that fills the pocket 140 during system operation also helps to minimize dust production, which might otherwise result from abrasion, friction and speed. This is because, during system operation, instead of striking a solid wall (like the upper surface of the expansion and deceleration chamber 136), the granular material moving through the inlet conduit 104a may strike the significantly softer granular material within the pocket 140 instead.

There is an external mating flange 142 at a distal end of the horizontal portion 138. The external mating flange 142 is connected, with fasteners (e.g., screws, nuts and bolts, etc.) to a corresponding external mating flange 144 on the final portion 124 of the inlet conduit 104a. The sidewall (e.g., 106 in FIG. 1) of the silo is not shown in FIG. 2. However, in a typical implementation, the external mating flanges 142, 144 would be outside of the silo 102. In a typical implementation, locating this connection between mating flanges 142, 144 outside the silo 102 makes it easy to access (for repair or replacement) the final portion 124 of the inlet conduit 104a, which extends into the silo 102.

The final portion 124 of the inlet conduit 104a extends horizontally (perpendicular to a plane of the external mating flange 144) into the silo 102 through an opening in the sidewall of the silo 102. In the illustrated implementation, the final portion 124 of the inlet conduit 124 defines a flow passage with the same shape and dimensions as the horizontal portion 138 of the turning portion 122 of the inlet conduit 104a. In a typical implementation, the dimensions (e.g., the cross-sectional area) of the final portion 124 of the inlet conduit 104a allow continued expansion of air without significant (and in some cases any) acceleration of the air and granular material being conveyed by the air.

According to the illustrated implementation, there is an opening 150 in a bottom surface of the final portion 124 of the inlet conduit 104a inside the silo 102. In a typical implementation, all other surfaces of the final portion 124 of the inlet conduit 104a inside the silo 102 (i.e., the top surface, two side surfaces, and an end surface of the final portion 124) are solid and uninterrupted. The opening 150 in the bottom surface of the final portion 124 of the inlet conduit 104a extends lengthwise along the final portion 124 of the inlet conduit 104a. The opening 150 is configured to allow the air to flow out of the inlet conduit 104a and into the silo 102, carrying the granular material with it.

In a typical implementation, the cross-sectional area defined by the opening 150 is at least equal to the cross-sectional area of the air flow channel inside the final portion 124 of the inlet conduit 104a. Thus, if the final portion 124 of the inlet conduit 104a is 5.5 inches by 5.5 inches (with a cross-sectional area of 30.25 inches), then the opening 150 would have a cross- sectional opening of at least 30, 25 inches as well.

FIG. 3 A includes a schematic, top, partial cross-sectional view of a system 100a that is identical in many ways to the system 100 in FIG. 1 (and highly similar in other ways), The system 100a includes a silo 102 and two sets of three inlet conduits 104al-104fl. FIG. 3B is a detailed view of the inlet conduit 104dl by itself.

Referring to FIG. 3B, it can be seen that the opening 150 in the bottom surface of the final portion 124 of the inlet conduit 104dl does not extend all the way to the end of the final portion 124; this is typical. Instead, a portion of the final portion 124 of the inlet conduit 104dl extends beyond the end of the opening to form a pocket 152 (or“dead head”) that is inside the final portion 124 of the inlet conduit 104dl and in line with the flow direction of air into the final portion 124 of the inlet conduit 104dl. During system operation (e.g., when granular material is being conveyed through the inlet conduit 104dl, the pocket 152 collects and fills up with granular material. Once filled, the pocket 152 tends to remain filled with granular material for at least as long as the air moves the granular material through the inlet conduit 104dl . The granular material that fills the pocket 152 during system operation helps to minimize the possibility of high speed granular material damaging the end surface of the final portion 124 of the inlet conduit 104dl, and also helps to minimize dust production.

FIG. 3C is a perspective view showing a turning portion 122a that is similar to the turning portion 122 shown in FIG. 2. The physical configuration of the expansion and deceleration chamber 136a in FIG. 3C is slightly different than the physical configuration of the expansion and deceleration chamber 136 in FIG. 2.

FIG. 3D is a partial perspective view of the flanged end of the final portion 124 of inlet conduit 104fl extending through an opening in an angled top 109 of the silo 102.

FIGS. 4A-4C is a time sequence of schematic representations showing the system 100 in FIG. 1 (that includes the silo 102 and six inlet conduits 104a-104f) being filled with granular material from an external source thereof. It should be assumed, for purposes of this example, that the level granular material in the silo 102 at the start of the sequence is very low (e.g.

significantly lower than the portion of the lowest inlet conduits 104a, 104b inside the silo 102.

In the illustrated example, the external source of granular material includes a container 454 of granular material. In some instances, the container 454 of granular material may have arrived at the site mounted on the back of a delivery vehicle. The container 454 is configured to unload granular material into a pneumatic conveying system 458 through an airlock 456. The airlock 456 can be virtually any kind of airlock (e.g., a rotary airlock valve). The pneumatic conveying system includes a pneumatic conveying channel that receives air (for the pneumatic conveying) from an air compressor 460. A pressure gauge 462 is configured to measure pressure inside the pneumatic conveying channel of system 458 during operation. An increase in pressure at the pressure gauge 462 can correspond to a decrease in flow rate for the air and granular material inside the pneumatic conveying channel that system 458. This may indicate that the granular material inside the silo has reached a level that is blocking or starting to block the flow path of air and granular material into the silo 102, thus producing the increase in pressure at the pressure gauge 462. Thus, during system operation, if a human user notices an increase in pressure at the pressure gauge 462, that human system operator may switch from whatever inlet conduit is being used to a different, higher inlet conduit.

In FIG. 4A, the external source of granular material is connected to one of the lowest inlet conduits (i.e., 104a). In a typical implementation, this connection would be a simple connection of a tube or pipe to another tube or pipe. There are a variety of ways to accomplish or implement this kind of connection that are well known in the art. All of the other inlet conduits (104b-104f), in the illustrated implementation, are plugged— with physical plugs 462 that fit into and seal the open distal ends of those inlet conduits (104b-104f). This prevents air and/or dust from exiting the silo 102 through those conduits (104b-104f). In a typical implementation, the system would include a filtered opening (not shown) through which air (but not really dust or granular material) can exit the silo 102 while it is being filled.

Typically, the granular material would be delivered into the silo through the lowest inlet conduit 104a until the granular material in the silo 102 reaches a level that begins to restrict flow of air and granular material through the lowest inlet conduit 104a into the silo 102. At the point, the pressure gauge 462 will start to reflect an increase in pressure in the pneumatic conveying system 458. In response to the pressure gauge 462 showing the increase in pressure, a human system operator may turn the pneumatic conveying system off, disconnect the source of granular material from the lowest inlet conduit 104a, plug the lowest inlet conduit 104a, remove the plug from the next lowest inlet conduit 104b, connect the source of granular material to the next lowest inlet conduit 104c on the same side of the silo 102 as the previously-used lowest inlet conduit 104a, and turn the pneumatic conveying system back on. The resulting configuration is shown in FIG. 4B.

In FIG. 4B, the external source of granular material is connected to one of the second lowest inlet conduits (i.e., 104c) on the same side of the silo 102 as the previously-used inlet conduit 104a. All of the other inlet conduits (104a, 104b and 104d-104f), in the illustrated implementation, are plugged— with physical plugs 462 that fit into and seal the open distal ends of those inlet conduits.

Typically, the granular material would be delivered into the silo 102 through this second lowest inlet conduit 104c until the granular material in the silo 102 reaches a level that begins to restrict flow of air and granular material through the second lowest inlet conduit 104c into the silo 102. At the point, the pressure gauge 462 will start to reflect an increase in pressure in the pneumatic conveying system 458. In response to the pressure gauge 462 showing the increase in pressure, a human system operator may turn the pneumatic conveying system off, disconnect the source of granular material from the second lowest inlet conduit 104c, plug the second lowest inlet conduit 104c, remove the plug from one of the highest inlet conduit 104e, connect the source of granular material to the unplugged highest inlet conduit 104e, and turn the pneumatic conveying system back on. The resulting configuration is shown in FIG. 4C.

In FIG. 4C, the external source of granular material is connected to one of the highest inlet conduits (i.e., 104e) on the same side of the silo 102 as the previously-used inlet conduits (i.e., 104a and 104c). Inlet conduits (104a-104d and 104f), in the illustrated implementation, are plugged— with physical plugs 462 that fit into and seal the open distal ends of those inlet conduits. Typically, the granular material would be delivered into the silo 102 through the connected highest inlet conduit 104e until the granular material in the silo 102 until the silo 102 is full.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.

For example, although the system shown in FIG. 1 has six different inlet conduits, a system can include any number of two or more inlet conduits that enter the silo at different heights. An exemplary system might include a silo and as a few as two inlet conduits: a first inlet conduit that extends into the silo at a first lower height, and a second inlet conduit that extends into the silo at a second higher height. Other exemplary system mays have more than six inlet conduits. The inlet conduits for a particular system may all be on the same side of the silo or they may be at more than two locations around the perimeter of the silo. The inlet conduits can include more or fewer distinct pieces than explicitly described herein. In essence, an inlet conduit can be virtually any kind of physical structure or combination of physical structures that can define a space, through which a granular material can be pneumatically conveyed.

The size (both relative and absolute) and shape of various system components, including the size and shape of various subcomponents of the inlet conduits and/or the various subsections of the inlet conduit, can vary considerably. For example, certain portions of the inlet conduits are disclosed herein as being cylindrical. Those portions, however, could instead be rectangular in cross-section, or have any other shaped cross-section. Likewise, certain portions of the inlet conduit are disclosed herein as having a rectangular (or square) or non-circular cross-section. Those portions, however, could instead have circular cross-sections, or any other shaped cross- section. Plugs are described as being used to block the inlet conduits that are not being used to convey granular material. However, it is at least possible that other means (e.g., valve or the like) might be used instead.

The differences in height for the entry points into the silo of the different inlet conduits in a particular group can, of course, vary considerably as well. In one example, the lowest of the inlet conduits may enter a particular silo at a height of about 43 feet above ground level (or the base of the silo) and the highest of the inlet conduits may enter the particular silo at about 52 feet above ground level (or the base of the silo). The shorter inlet conduit in this example is approximately 17% shorter than the longer inlet conduit, which would result in significantly less conveying resistance through the shorter inlet conduit as compared to the longer inlet conduit.

The systems and techniques are disclosed herein as having a particular applicability to certain industries (e.g., proppant for hydraulic fracturing). However, the systems and techniques disclosed herein are not limited in their applicability to only certain industries. Instead, their applicability is, at least potentially, quite broad.

Additionally, the systems and techniques are disclosed herein as being used in connection with silos. The word silos (or silo) should not be limiting. Instead, it should be understood herein to encompass virtually any kind of container that may be used for bulk storage of granular material.

Certain words are used herein to express approximations. These words should be afforded their ordinary meaning. However, the ordinary meaning of“about,” for example, should be understood to include at least plus or minus 5% or 10% (e.g., plus or minus 8%).

Moreover, while this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub combination.

Similarly, while operations are disclosed herein as occurring in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all represented operations be performed, to achieve desirable results.

Other implementations are within the scope of the claims.