The present disclosure relates to an apparatus and a method for mixing a first fluid with a second fluid, particularly for mixing steam into pulp.
This disclosure is an improvement to the apparatus and method for introducing a first fluid into the flow path of a second fluid and use of such an apparatus disclosed in U.S. Pat. No. 9,427,716, issued 30 Aug. 2016.
As used herein, fluid means a gas, a liquid, steam or a mixture of these. As used herein, fluid is also meant to include a system comprising a mixture of solid particles and a liquid or gas, where the mixture has fluid-like properties. One example of such a system is a suspension, for example, a cellulose pulp suspension.
As used herein, introducing one fluid into the flow path of another fluid means injection, mixing, dispersion or other admixing of one fluid, which is also called the admixture fluid, into the flow path of the other fluid.
It is not unusual in industrial processes that fluids are mixed with each other. In for example, the paper industry, it is not unusual that process chemicals, for example, oxygen gas, chlorine dioxide or ozone, are introduced into a flow of pulp suspension. It is also common in this industry that steam is introduced into the flow of pulp suspension with the purpose of heating the pulp suspension.
There are a number of previously known methods and apparatuses for introducing one fluid into another fluid. One problem with these devices is that they are relatively energy intensive and that they require relatively much maintenance.
When introducing one fluid into the flow path of another fluid, it is generally always desirable to obtain a mixing or dispersion of the fluids which is as effective and uniform as possible.
One objective when injecting one fluid into another fluid, particularly when injecting steam into pulp suspension, is to admix i.e., to mix and disperse the added steam.
If the mixing or dispersion is not sufficient, there is a risk of steam bubbles forming in the liquid or suspension, wherein said steam bubbles may subsequently implode. These steam implosions cause pressure shocks in the liquid or suspension, which in their turn may propagate to machine supports, apparatuses and other process equipment and cause knocks and vibrations, which can be so powerful that mechanical damage results. This is especially a problem when a large amount of steam is added to a cellulose pulp suspension and especially to a cellulose pulp suspension of medium consistency. As used herein, a pulp suspension of medium consistency means a pulp suspension having a dry solids content in the range of approx. 8-14%.
Accordingly, there is a need to maximize and improve the mixing and dispersion of the fluids in order to increase efficiency and minimize the risks of damaging equipment.
Disclosed is an apparatus for mixing a first fluid into a flow path of a second fluid, the apparatus comprising: a chamber enclosing the flow path, the chamber including a second fluid first inlet for receiving its respective fluid. The apparatus also includes a second inlet arranged downstream of the first inlet and receiving the first fluid, as well as an outlet arranged downstream of the second inlet for discharging a mixture of the first fluid and the second fluid. The second inlet flows into the flow path and is formed by a shared fluid injector mounted transverse to the axial direction that one fluid and the two fluid flows through its chamber. The flow path includes two respective throttle bodies, each of which is pivotally arranged inside the chamber and attached to opposed sides of the chamber for controlling the flow area of the flow path.
Disclosed is a high-speed injector apparatus intended to be used in a process plant for mixing a second fluid, in the form of steam, into the flow path of a first fluid, in the form of a cellulose pulp suspension, wherein the hot steam is intended for heating the pulp suspension to a desired temperature, for example, to a temperature that is suitable for a subsequent bleaching step. It will be appreciated, however, that the principle of the disclosure may be used for mixing other fluids, such as gases, such as oxygen gas, chlorine gas or ozone, or liquids, such as pH-adjusting liquids, chlorine dioxide or other treatment liquid, into a pulp suspension. It will also be appreciated that the first fluid may be of another type than a pulp suspension, for example, process liquor.
The apparatus comprises a substantially parallelepipedic housing 1, for receiving a pulp suspension from a first conduit 2 located upstream (see
The housing 1 is delimited externally by an upper delimiting surface, constituted by a roof portion 6, lateral delimiting surfaces, constituted by side walls 7 and 8 and by a short side wall 9 located upstream and a short side wall 10 located downstream, and a lower delimiting surface, constituted by a base portion 11.
Internally, the housing 1 comprises a substantially parallelepipedic chamber 12, which is approx. 500-700 mm long, approx. 200-250 mm wide, and approx. 150-300 mm high. The chamber 12 exhibits a circular first inlet 13 for receiving the pulp suspension from the first conduit 2 disposed upstream, and a rectangular outlet 14 for discharging the pulp suspension into the second conduit 3 disposed downstream. The first inlet 13 is formed by an opening in the short side wall 9 located upstream and has a diameter of approx. 80-200 mm. Accordingly, the inlet 13 has an area that is smaller than the cross-sectional area of the chamber 12. The rectangular outlet 14 is substantially equally large as the cross-sectional area of the chamber 12.
Accordingly, the chamber 12 encloses a flow passage 44 for the pulp suspension, said flow passage 44 extending from the first inlet 13 to the outlet 14.
Furthermore, the chamber 12 exhibits an elongated second inlet 15 for receiving the pressurized, hot steam from the supply means 4, said inlet 15 opening into the flow passage 44. The inlet 15 is arranged in the roof portion 6 of the housing and is located approx. 100-150 mm from the outlet 14 of the chamber. The supply means 4 connects to the second inlet 15 from the top side of the roof portion 6. The second inlet 15 is arranged with its longitudinal direction transversely to the chamber 12 and the flow passage 44, i.e. transversely to the flow direction of the pulp suspension, and extends across substantially the entire width of the flow passage 44. In other words, the second inlet 15 has a length that is substantially equal to the width of the chamber 14. The width of the inlet 15, i.e. its extension in the longitudinal direction of the chamber 14, is approx. 25-70 mm.
The base portion 11 exhibits an elongated recess 16, which extends transversely to the longitudinal direction of the chamber 12 close to the first inlet 13, and each of the side walls 7 and 8 exhibit a respective crescent-shaped opening 17, which connects to the recess 16 at the ends thereof. A tubular cover 41 is fixedly disposed in these recesses 16, 17, as is evident from
Two removable stoppers 45 and 56 are arranged in the base portion 11 of the housing 1 and in the cover 41. The stoppers 45, 56 enable rinsing of the housing 1 and the cover 41 in case of so-called plugging, i.e. that the pulp suspension clogs the housing 1 and the cover 41.
The supply means 4, for supplying the pressurized, hot steam to the chamber 12 and the flow passage 44 via the second inlet 15, comprises a pipe flange 19 that connects to a steam conduit (not shown) for feeding pressurized steam to the supply means 4. Furthermore, the supply means 4 comprises a pipe part 20, which exhibits a first end 21 and a second end 22. The first end 21 connects to the pipe flange 19 and the second end 21 connects to an elongated valve 23 of the supply means 4. The second end 22 is compressed, as is evident from
The distance between the valve spindle 25 and the orifice of the inlet 15 is relatively short, approx. 20-50 mm. This, together with the simple geometry of the outlet, ensures that any pulp suspension, which may have accumulated in the inlet during an interruption of the steam supply, easily can be pushed out by the steam when the steam supply is resumed, which provides for good operating reliability.
The control unit 5 comprises a throttle body in the form of a flap or lip 29, a pivotal axle 37, two lever arms 48 and 49, and pivoting means in the form of two pneumatic cylinders 50 and 51.
The axle 37 is pivotally arranged inside the axial space of the cover 41 by means of self-lubricating bearings 43, as is evident from
The flap 29 is arranged inside the chamber 12 and has the shape of a substantially rectangular plate, having a thickness of approx. 25-35 mm. The flap 29 exhibits a top side 30, facing away from the base portion 11 of the housing, a bottom side 31, facing toward the base portion 11 of the housing, two parallel long sides 32, 33, facing toward the side walls of the housing, a first end 34 or short side 34 located upstream, and second end 35 or short side 35 located downstream.
The flap 29 has its first end 34 fixedly connected to the pivotal axle 37 by means of bolts 36 and extends, through the recess 16 in the base portion 11, downstream in the flow direction of the pulp suspension. The second end 35 of the flap 29 is free, and its connection to the top side 30 is chamfered, as is evident from
The lever arms 48, 49 are fixedly disposed on the free ends of the axle journals 46, 47 of the axle 37, at right angles to the longitudinal direction of the axle 37. Accordingly, the lever arms 48, 49 rotate together with the axle 37 and the flap 29, when these are turned. The respective lever arm 48, 49 abuts against one of said pneumatic cylinders 50, 51. In the shown embodiment, these pneumatic cylinders are constituted by piston rod-free bellows cylinders 50, 51, which exhibit end plates 52, 53 abutting against the lever arms 48, 49. In the shown embodiment, the respective bellows cylinder 50, 51 is fixedly disposed on a respective side wall 7, 8 of the housing 1.
The flap 29 is pivotable between a lower end position, where the bottom side 31 of the flap abuts against the base portion 11 of the chamber 12, and an upper end position, where the free end 35 of the flap 29 abuts against the roof portion 6 of the chamber 12. The flap 29 has a width that is substantially equal to the width of the chamber 12. Accordingly, when using the apparatus, the pulp suspension is forced to pass over the top side 30 of the flap 29. Thus, the upper end position of the flap 29 constitutes a fully closed position, where the flow passage 44 is fully closed, and the lower end position of the flap 29 constitutes a fully open position, where the flow passage 44 is fully open. Accordingly, when the flap 29 is located between its end positions, the flap 29 forms a constriction in the flow passage 44, where the flow area of the flow passage decreases continuously from the end 34 of the flap 29 located upstream to the free end 35 thereof located downstream. Immediately downstream of the flap 29, i.e. directly downstream of its free end 35, the flow area of the flow passage 44 suddenly increases to its initial value, i.e. to the same value as directly upstream of the flap 29. The inlet 15 opens near the free end 35 of the flap 29, and the steam is thus supplied in the region where the cross-section of the flow passage 44 suddenly increases, which is advantageous for the mixing and dispersion of the steam into the pulp suspension.
While the pulp suspension passes over the flap 29, the pulp suspension exerts a torque about the axle 37 on the flap 29, which tends to push the flap 29 down, i.e. to pivot the flap 29 clockwise about the axle 37 in
At a constant flow rate of the pulp suspension, the flap 29 adjusts itself to an equilibrium position, where the torque that the flow of pulp suspension exerts on the flap 29 is balanced by the torque that the bellows cylinders 50, 51 exert on the flap 29. In other words, the bellows cylinders 50, 51 are adapted to continuously exert a torque on the flap 29, which balances the torque that the pulp suspension exerts on the flap 29 at every flow rate of the pulp suspension.
If the flow rate of the pulp suspension increases, the flap 29 is pushed down, so that the smallest flow area of the flow passage 44, i.e. its flow area at the end 35, increases. If the flow rate of the pulp suspension stabilizes at this new, higher level, the flap 29 adjusts itself to a new equilibrium position, where the flow area of the flow passage 44 at the end 35 is larger than in the previous equilibrium position. If the flow rate of the pulp suspension decreases, the flap 29 is pushed up by the bellows cylinders 50, 51, so that the flow area of the flow passage 44 at the end 35 decreases. If the flow rate of the pulp suspension stabilizes at this new, lower level, the flap 29 thus adjusts itself to a new equilibrium position, where the flow area of the flow passage 44 at the end 35 is smaller than in the previous equilibrium position. Accordingly, an increasing flow rate of the pulp suspension causes the flow area of the flow passage at the end 35 to increase, and a decreasing flow rate causes the flow area to decrease.
It will be appreciated that this controlling of the flow area compensates for the decrease and increase, respectively, in the flow velocity of the pulp suspension that results from a decrease and an increase, respectively, of its flow rate. If for example, the flow rate of the pulp suspension decreases, also the flow velocity of the pulp suspension in the region upstream of the flap 29 decreases, since the flow area in this region is unchanged. However, due to the decreasing pressure of the pulp suspension on the flap 29 in this situation, the flap is pivoted 29 upward and the flow area at the flap 29 decreases. This, in its turn, implies that the flow velocity of the pulp suspension at the end 35 is maintained at substantially the same level as before the flow rate decrease. If the flow rate of the pulp suspension increases, an adjustment is effected in the other direction, i.e. due to the increasing pressure of the pulp suspension on the flap 29, the flap 29 is pushed down, the flow area above the flap 29 increases, and the flow velocity of the pulp suspension at the end 35 is maintained substantially at the same level as before the flow rate increase. Accordingly, the flap 29 acts as a throttle body, which controls the flow area of the flow passage 44 while being actuated by the cylinders 50, 51, so that the flow velocity of the pulp suspension is maintained within a desired range. Accordingly, the control unit 5 ensures that a decrease of the flow rate of the pulp suspension does not lead to a situation, where the flow velocity of the pulp suspension at the steam supply position falls below a level where the mixing of the steam risks becoming so inadequate that there is a risk of damaging steam implosions occurring.
In addition to the fact that the bellows cylinders 50, 51 abut against the lever arms 48, 49 with a pushing force, the bellows cylinders 50, 51 also dampen any pressure waves which may occur in the pulp suspension, for example, when the pulp suspension passes over the flap 29, or if damaging steam implosions still occur. Accordingly, the bellow cylinders 50, 51 also constitute spring or damping means.
Accordingly, the flap 29 adjusts itself to an equilibrium position, where the flow of pulp suspension imposes a pushing force on the flap 29, which is balanced by the force from the bellows cylinders 50, 51. Thus, the flap 29 is self-adjusting and its actual angle relative to the base portion 11 is dependent on the magnitude of the pulp flow. The predetermined flow velocity range can be set by adjusting the abutting force of the bellows cylinders 50, 51 against the lever arms 48, 49, whereby the desired equilibrium position can be set. By increasing the abutting force of the bellows cylinders 50, 51 against the lever arms 48, 49, the axle 37 is rotated so that the flap 29 is pushed up to a new equilibrium position. This implies that the cross-sectional area above the flap decreases, which causes the flow velocity of the pulp suspension at the second inlet 15 to increase.
Accordingly, the apparatus is self-adjusting in that the control unit 5 ensures that the flow velocity of the pulp flow at the second inlet 15 is always sufficiently high to avoid, or at least reduce the occurrence of steam implosions. The control unit 5 also ensures that an increase of the flow rate of the pulp suspension does not lead to an undesirably high flow resistance across the apparatus.
It will be appreciated that the minimum allowable flow velocity of the pulp suspension at the steam supply position is dependent on a number of factors, for example, the concentration of the pulp suspension, the steam flow rate, i.e. the amount of steam supplied, etc. As an example of a suitable flow velocity range when supplying steam to a pulp suspension, it may be mentioned that, when mixing steam at a flow rate of approx. 2-20 kg/s into a pulp suspension of medium consistency, the flow velocity of the pulp suspension at the free end 35 should be within the range of approx. 30-35 m/s, if the embodiment shown in the figures is used.
Since the cross-sectional area of the second conduit 3 is larger than the cross-sectional area of the outlet 14, the pulp suspension will decelerate after the outlet 14 in those regions of the second conduit 3 which are located radially outside the outlet 14, and be retained against the inside surface of the second conduit 3. Therefore, a volume of fibers will be built up successively by stagnant pulp, along the inside shell surface of the second conduit 3, which can absorb pressure waves in the pulp suspension which may occur due to any steam implosions. The pulp suspension in the middle of the second conduit 3, on the other hand, will continue at a high velocity through the second conduit 3 to a subsequent third conduit 54, which has a diameter that is substantially smaller than the diameter of the second conduit 3.
It will also be appreciated that the apparatus does not necessarily have to comprise a conduit in accordance with the second conduit 3 of
It will also be appreciated that the throttle body may have a different design than the above-described flap 29. The throttle body can for example, be wedge-shaped.
Improved Valve of this Disclosure
The valve spindle housing outlet 15′ is defined by an opening having an edge 72, and the cylinder 84 is positioned closely adjacent the edge 72 so that when the cylinder 84 is rotated (clockwise as shown in
Further, in the embodiment disclosed
More particularly, the cylinder 84′ of the valve 80′ shown in
Improved Apparatus of this Disclosure
Illustrated in
The disclosed apparatus 100 comprises a first chamber 12′ and a second chamber 12″, each chamber enclosing a respective flow path 44′ and 44″. Each chamber includes a respective one fluid or two fluid first inlet 13′ and 13″ for receiving its respective fluid, a respective second inlet 115 and 115′ arranged downstream of the first inlet and receiving the first fluid, as well as an outlet 14′ arranged downstream of the respective second inlet 115 and 115′ for discharging a mixture of the first fluid and the one fluid and the two fluid. Each flow path extends from its respective first inlet to the outlet. Each second inlet flows into a respective flow path and is formed in a shared fluid injector 80″ mounted transverse to the axial direction that one fluid and the two fluid flows through the respective chambers.
In the illustrated embodiment, the one fluid and the two fluid is a second fluid. A splitter (not shown) separates the second fluid into each of the first inlets 13′ and 13″. By splitting the second fluid between the first inlets, the first fluid second inlet engages twice as much of the second fluid. In other embodiments, the one fluid and the two fluid could be different fluids. Further, each supply to the one fluid or two fluid first inlets can be throttled (not shown), and throttled differently, if desired.
More particularly, as shown in
Further, as illustrated in
The cylinder 84″ in one position is positioned so that the cylinder 84″ completely obstructs the valve spindle housing outlets 115 and 115′, not allowing any fluid to pass around the cylinder 84″, the cylinder walls being solid except for having the openings 68′ through a portion of the cylinder 84″, so that when rotated to a closed position, the solid portion of the cylinder 84″ fully obstructs the valve spindle housing outlets 115 and 115′, and when rotated to an open position, the first fluid can pass into the inside of the cylinder 84″ and then through the openings 115 and 115′ and out of the valve spindle housing 27″. Intermediate positions permit variably limited flow through the valve 80″.
An advantage of the disclosed valve over conventional valves is that there are two first fluid sealing surfaces. In other words, when the cylinder first fluid outlets 68″ are facing the enclosed portion of the spindle housing 27″, the valve 80″ is closed. Further, when the cylinder outlets 68″ face the enclosed portion of the spindle housing 27″, the cylinder inlets 22′ and 22″ are also closed. This dual closure of the valve 80″ helps to prevent the passage of the first fluid through the valve when the cylinder is in the closed position.
Further, as illustrated in
The flap first end is pivotally arranged, via a respective axle 37′ and 37″, on a wall of the respective chamber opposite the first fluid injector 80″. And at least one respective compressively loaded lever arm 48′ and 49′ is arranged on the axle. The pivoting means comprises a respective pneumatic cylinder 50′ and 51′, which is adapted to produce the compressive load on the lever arm. Further, the flap 29′ and 29″ has a width substantially equal to the chamber width.
In an alternate embodiment 100′, as shown in
Filing Document | Filing Date | Country | Kind |
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PCT/US17/66229 | 12/13/2017 | WO | 00 |
Number | Date | Country | |
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62433707 | Dec 2016 | US |