High pressure control system and method for pneumatic conveying

Abstract

Described is a system for conveying dense-phase material comprising: a pressure vessel; a material conveying line; a compressed gas supply, a primary gas feed line; a primary line control valve and a flow meter; a plurality of pressure sensors and control valves; and a control system for the air flow volume by controlling the control valves, and the primary line control valve; wherein the primary gas feed line comprises a first control valve, and the system comprises a first bypass line, which connects the primary gas feed line to the material conveying line and is located upstream of the first control valve, and wherein the first bypass line comprises a second control valve; wherein in use, the control system monitors the pressures of the pressure vessel, the material conveying line, and the compressed gas supply discharge, to maintain a set volume flowrate of the conveying gas along the conveying line.

Description

[0001] 24030P-WO Qlar Europe GmbH

[0002] High pressure control system and method for pneumatic conveying

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a pneumatic conveying apparatus. Specifically, the invention relates to a dense phase material pneumatic conveying apparatus which uses a high pressure compressed gas feed, wherein the system comprises a control loop to optimise the efficiency of the material conveying method, the system comprising a plurality of pressure sensors and control valves.

[0005] BACKGROUND OF THE INVENTION

[0006] Dense phase material conveying via pneumatics is a well known method in the material conveying industry. Most industrial powders and bulk granular materials can be conveyed by pneumatic means in dense phase, but systems have to be designed to suit individual material characteristics such as density, particle size distribution, moisture content, particle shape etc. Changes in conveyed material characteristic from the designed parameters can lead to inefficient or unreliable operation.

[0007] Airflow into the system most commonly uses fixed flow control such as square edge orifice plates , delaval nozzles or manual flow control valves. These fixed flow devices are often permanently adjusted either at commissioning or over time by operators to suit changeable material characteristics. This leads to inefficiencies when material characteristics change for the better, as the system is often left set up for a worst case situation.

[0008] Current dense phase conveying vessels for conveying other higher bulk density powders and bulk materials use compressed gas typically at pressures of around 1 bar gauge to 16 bar, and at a specified volume flow in order to achieve a specified conveying capacity.24030P-WO Qlar Europe GmbH

[0009] Pressures in this document are given in bar, however they should be understood to refer to gauge pressure, and not absolute pressure. Gas will be referred to throughout this application so as to cover any type of conveying gas, however it should be apparent to the skilled person that air is the most common conveying gas.

[0010] Typically the gas flow and pressure is distributed to several points on the conveying vessel at the start of the conveying pipeline. Some of this gas flow will go to the top of the vessel and some to the aeration on the vessel if fitted, and some to the outlet of the vessel and / or the conveying pipeline.

[0011] The gas flow to the vessel is to provide a positive pressure gradient between the vessel and the material outlet, to provide the conveying force to discharge the material. The gas flow to the conveying line is set and stabilise the density of the conveyed material and to prevent blockages within the conveying line from forming.

[0012] The gas flow to each point is typically controlled (restricted) with a square edged orifice plate or de Laval (sonic) nozzle, with the gas flow volume being determined by the geometry of the orifice, the upstream and the downstream pressure. The upstream pressure is usually set with a pressure regulator, or by the discharge pressure directly from the compressor. The proportion of air going to each point is determined during pre-commissioning trials and also during commissioning of the system or by empirical test work and scaling.

[0013] In some cases the selection of orifice geometry and regulator pressure does not provide for energy optimised conveying performance across different operating conditions, and may need to change for different materials with different conveying pressures to maintain optimum performance. In prior art systems the orifice geometry to change the distribution of air for different conditions is changed manually, which is not always desirable due to the requirement to dismantle the24030P-WO Qlar Europe GmbH

[0014] equipment, and also with frequently varying conveying conditions would have to be frequently dismantled and changed.

[0015] Varying conveying conditions can arise for many reasons, for example conveying different bulk solids, conveying to different destinations over different conveying distances, and also variability within the bulk solid itself even though nominally the same. Such variability could be particle size distribution, permeability or cohesiveness. All of these variations affect the pressure downstream of the restricting orifices, which in turn affects the volume of air which can pass.

[0016] The present invention is for an arrangement of valve and control philosophy that automatically and adaptively adjusts the conveying air flow to each connection point according to the conveying conditions, to optimise performance and energy efficiency of the system.

[0017] This airflow control and distribution method requires high pressure losses through the supply manifold and often results in the compressed air source being at much higher supply pressures than the back pressure in the conveying pipe resulting from the conveyed material. This leads to very inefficient systems according to the art, which need excessive compressor pressures to function. Compressor output pressures according to the art are also fixed at a high value - to ensure blockages do not occur. As systems according to the art do not have variable compressor pressures orflow, they are not customised to individual loads of material.

[0018] Although systems in the art can be known for the low consumption of conveying air, there is a large energy penalty forthe higher levels of compression which are required for this kind of fixed air flow control.24030P-WO Qlar Europe GmbH

[0019] Performance of dense phase pneumatic conveying systems are highly dependent on material characteristics. Often systems are set up, commissioned, and adjusted overtime for worst case conditions. Many systems that have predictably changeable materials address this using multiple air supply manifolds to adjust when it is known a material characteristic will change.

[0020] If material characteristics change unpredictably, then system are often run sub optimally causing inefficiencies, system wear and loss of reliability.

[0021] Having a commercially viable self-adjusting manifold has been a desirable product since the invention of dense phase conveying systems.

[0022] For the above reasons, there remains a need to address or mitigate at least one or more of the aforementioned problems.

[0023] It is therefore an object of at least one aspect of the present invention to provide an improved system and method for pneumatic conveying of dense phase materials.

[0024] It is a further object of at least one aspect of the present invention to provide an improved system and method, which is more energy efficient, and more effective at conveying than systems according to the art.

[0025] SUMMARY OF THE INVENTION

[0026] A pneumatic conveying system for conveying dense-phase material, the system comprising:

[0027] a pressure vessel for receiving material from a material supply feed;

[0028] a material conveying line for conveying material away from the pressure vessel; a compressed gas supply for supplying gas to the pressure vessel and the material conveying line, wherein gas is supplied to the pressure vessel via a primary gas feed line;24030P-WO Qlar Europe GmbH

[0029] a primary line control valve and a flow meter;

[0030] a plurality of pressure sensors and a plurality of control valves; and

[0031] a control system for controlling the air flow volume introduced to the system from the compressed gas supply, by controllingthe plurality of control valves, and the primary line control valve;

[0032] wherein the primary gas feed line comprises a first control valve, and the system further comprises a first bypass line, which connects the primary gas feed line to the material conveying line and is located upstream of the first control valve, and wherein the first bypass line comprises a second control valve;

[0033] wherein in use, the control system monitors the pressure vessel pressure, the material conveying line pressure, and the compressed gas supply discharge pressure, to maintain a set volume flowrate of the conveying gas alongthe conveying line.

[0034] The output pressure from the compressed gas supply may be 1 bar and above. The output pressure may be around 1 bar to 16 bar. The pressure used may be considered to make the system a high pressure system.

[0035] The pressure vessel may further comprise an outlet material valve, an inlet material valve, and a pressure relief valve. The system may comprise any number of valves, includingthe valves as described herein.

[0036] Downstream of the first control valve, the primary gas feed line may branch into an upper feed line, which enters the top of the pressure vessel, and a lower feed line, which enters the bottom of the pressure vessel. The pressure vessel may only be fed with one feed line. Alternatively, the pressure vessel may be fed with more than one feed line. The pressure vessel may be fed with feed lines which enter at multiple locations. The feed lines may enter at locations which are important for effective clearing of the material inside the pressure vessel.24030P-WO Qlar Europe GmbH

[0037] The pressure vessel pressure may be measured with an upper feed line pressure sensor.

[0038] The system may further comprise a second bypass line, which connects the primary gas feed line to the material conveying line and is located upstream of the first bypass line. The second bypass line may comprise a third control valve. The pressure vessel pressure may also be measured with any suitable device located proximate to the pressure vessel.

[0039] The first bypass line may comprise a first bypass line pressure sensor, located downstream of the second control valve. The second control valve may be a proportional valve, capable of being partially opened. The pressure sensors described herein may be any type of suitable pressure sensor.

[0040] The second bypass line may comprise a second bypass line pressure sensor, located downstream of the third control valve. The second bypass line may comprise a third control valve. The second bypass line may further comprise a fixed orifice. The third control valve may be a proportional valve, cable of being partially opened. Proportional valves which allow partial opening allow for varied flowrates of gas, from 0 - 100% of the flow.

[0041] The control system may dynamically change the airflowvolume of the conveying gas allowed into the system, usingthe primary line control valve, using data from the flow meter, which is comprised of a fixed orifice, a pressure sensor, and a differential pressure sensor. The system may control the volume of the gas based on various factors, such as the type of material being conveyed, the conditions of the material, or the conditions of the system. The volume of the gas may change dynamically, and be updated every minute for example.24030P-WO Qlar Europe GmbH

[0042] In another example, there is provided a method of controlling a dense phase pneumatic conveying system according to any previous example, the method comprising:

[0043] measuringthe pressure at each pressure sensor;

[0044] adjusting the control valves and primary line control valve to maintain a set volume flowrate of the conveying gas along the conveying line. This method described leads to an efficient use of energy, and improved and optimised material conveying.

[0045] When the pressure at the first bypass line pressure sensor is below a threshold value, the second control valve and optionally the third control valve, may be opened to their minimum value, such that the conveying gas is primarily directed towards the pressure vessel. This technique directs all of the air towards the pressure vessel, which has the effect of clearing material from the pressure vessel, towards the material conveying line.

[0046] When either the first bypass line pressure sensor or the upper feed line pressure sensor exceed upper threshold values, the second control valve may open fully in order to direct all of the conveying gas to the material conveying line, thus reducing the conveying pressure as the pressure vessel discharge rate is reduced to a minimum. This technique is useful when the material conveying line comprises a blockage or a slug, as uninterrupted air is forced into the material conveying line without passing through the pressure vessel.

[0047] The third control valve (if fitted) may modulate to maintain an increased pressure differential between the second bypass line pressure sensor and the first bypass line pressure sensor, to help clear potential material plugs in the material conveying line. The modulation mayvarythe amount the valve is opened, ranging from 0-100% open.24030P-WO Qlar Europe GmbH

[0048] During operation of the second control valve and the third control valve, the control system may vary the volume of gas allowed into the system, via the primary line control valve, to ensure the required total air flow volume is directed to the system. The total air flow volume may be measured at several locations throughout the system.

[0049] The method may be a closed-loop feedback method. The system may measure pressures and flowrates, and feed these measurements back into the control variables such as gas speed and valve positions.

[0050] A method of filling a pneumatic conveying system according to any previous embodiment with material to be conveyed, the method comprising the steps of: stopping gas flow to the pressure vessel by closing the valve 120. If the optional vessel outlet valve is not fitted then the primary air control valve, secondary air control valve, and tertiary air control valves are also closed to stop air flow completely.

[0051] If the optional vessel outlet valve is fitted valve 120 is closed to stop gas flow to the pressure vessel, the optional vessel outlet valve is closed and the secondary and tertiary air control valves can continue to direct gas flow to the conveying line to transport residual material in the conveying line.

[0052] During either of these alternatives the pressure vessel inlet valve and pressure relief valve can be opened to enable filling of the pressure vessel with material.

[0053] Square edge orifice plate or nozzles are still used within the manifold however they can be used well within the unchoked region of pressure differentials. The flow control is achieved by the use of the flow meter and the primary air control valve. The orifice plates or nozzles are only used for distribution of gas.24030P-WO Qlar Europe GmbH

[0054] Compared to standard pressure vessel based dense phase conveying systems, the pressure and / or energy losses due to the flow control are greatly reduced and the compressed gas source pressure can closely match the required conveying pressure. Energy losses associated with over compression are avoided. This can save as much as 50% of the power consumption when comparing like for like applications.

[0055] The system may be used on with the method as previously described.

[0056] Having the air flow thorough the conveying pipeline during conveying can have the benefit of keeping the pipe route warm and free of condensation and can also be used to keep residual material in the pipe line fluidised and prevent blockages once filling is complete.

[0057] There are a number of advantages associated with the invention.

[0058] • The use of the second control valve to dynamically adjust the conveying gas distribution in the system instead of flip flopping the supply allowing the system to be automatically adjusted to varying conveying or material conditions without manual intervention.

[0059] 1. The system allow greatly optimised conveying of varying material characteristics and conveying conditions at all times.

[0060] 2. Possibility for the system to use algorithms to be self commissioning / self optimisingfor example using Al technology.

[0061] • The use of a cost efficient flow meter to enable commercial feasibility for use in control of dense phase conveying system.24030P-WO Qlar Europe GmbH

[0062] • To separate the total gas flow control from the gas flow distribution devices. This allows the use greatly oversized orifice plates for flow distribution and less energy losses due to pressure drops.

[0063] • Combining the flow control regulator and flow meter also results in lower energy losses for flow control, (flow control regulated is operated from small volume of higher pressure control gas and does not need high supply pressure for piloting).

[0064] • Controlling primary line control valve on both flow and pressure so that both flow and pressure limits can be maintained within the conveying system.

[0065] • Usingthe conveying pressure to adjust the conveying gas flow set point during the conveying cycle, (constant velocity control)

[0066] • Dynamically controlling the flow through the conveying line supplementary gas injection points by adjusting the differential pressure between the supplementary air supply pressure and conveying line pressure transmitter.

[0067] BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Embodiments of the present invention will now be described, byway of example only, with reference to the following figures:

[0069] Figure 1 is example of a pneumatic conveying system for dense phase materials, accordingto the prior art;

[0070] Figure 2 is another example pneumatic conveying system according to the prior art; and

[0071] Figure 3 is an example system accordingto the present invention.24030P-WO Qlar Europe GmbH

[0072] DETAILED DESCRIPTION

[0073] Generally speaking, the present invention relates to a pneumatic conveying system for pneumatically conveying bulk material, wherein the system comprises a feedback loop to control the flowrate of the bulk material.

[0074] Figure 1 is example of a pneumatic conveying system 800 for dense phase materials, according to the prior art. The system 800 comprises a material feed 802 and a pressure vessel 804 which are connected together. There is a conveying pipe 806 connected to the base of the pressure vessel 804, which conveys material from the pressure vessel 804 to a silo.

[0075] The system 800 also comprises a compressed gas supply 808, which is connected to the primary gas feed line 810 and the secondary gas feed lines 812. The secondary gas feed line 812 is fed into an injection manifold 814.

[0076] The pressure regulator 816 is used to stabilise and limit the maximum pressure. The conveying gas flow and distribution is set by manually adjustable proportion flow control valves 814 at many positions on the conveying system. By removing the pilot pressure to the pressure regulator, the pressure regulator is additionally used to stop the conveying gas flow to enable material to be filled into the pressure vessel.

[0077] The primary feed line valve 818 is a much larger valve than the other proportional valves. This means that a large proportion of conveying air is always directed to the top of the vessel 804 to force material into the conveying line 806. This always tries to discharge material as quickly as possible and conveying pressures tend towards the set point of the pressure regulator 816.

[0078] As the conveying pressure reaches the same pressure as the pressure regulator 816 the differential across the primary feed line valve 818 is reduced so flow to this point24030P-WO Qlar Europe GmbH

[0079] naturally reduces. Gas is then naturally biased along the conveying pipe through the supplementary air valve 820 as the pressure in the conveying pipe reduces towards the silo / reception point and therefore the supplementary air valves 820 have a greater differential pressure across them (and hence a greater flow).

[0080] Control valves 814 are also connected to the higher pressure side of the pressure regulator 816 and in the situation where the conveying pressure at the pressure vessel804is lowerthan a set point, controlvalves814are pulsed to encourage more material discharge and increase the conveying pressure further.

[0081] This manifold arrangement suffers from variable conveying gas flow.

[0082] Although the manually adjustable valves can be change more easily than fixed orifice plates or nozzles, this can be disadvantageous as operators often increase conveying gas flows to deal with conveying issues. These rarely get returned to optimum / as commissioned positions leading to progressively worsening efficiencies and / or performance of the system.

[0083] Figure 2 is another example pneumatic conveying system 900 according to the prior art. This system 900 is known as a ‘flip flop valve arrangement’ in the art.

[0084] Similar to the previous prior art system, there is a compressed gas supply 908, along with a material feed 902 and a pressure vessel 904, leading to a conveying line 906.

[0085] This arrangement sets the overall gas flow using a flow regulator 916 and orifice nozzle 930. This air is distributed through either top control valve 932 or bottom control valve 934. If the conveying pressure measured on at the pressure vessel 904 is below a set point then gas is routed through top control valve 932 and if the pressure is above a set point then gas is routed though bottom control valve 934.24030P-WO Qlar Europe GmbH

[0086] This is a common system used to artificially try and create / control slugs of the conveyed material in the conveying line.

[0087] It should be emphasised that the control valves in the prior art systems described above are manually adjusted. The systems according to the art are therefore a very inaccurate and crude way of controlling the gas flow around the system.

[0088] Performance of dense phase pneumatic conveying system are highly dependant on material characteristics. Often systems are set up, commissioned, and adjusted overtime for worst case conditions. Many systems that have predictably changeable materials address this using multiple air supply manifolds to adjust when it known a material characteristic will change.

[0089] If material characteristics change unpredictably, then system are often run sub optimally causing inefficiencies, system wear and loss of reliability.

[0090] Having a commercially viable self-adjusting manifold has been a desirable product since the invention of dense phase conveying systems.

[0091] Figure 3 is an example system 100 according to the present invention. Specifically, the figure shows a schematic of the process and instruments.

[0092] The system 100 comprises a pressure vessel 102 for receiving material from a material supply feed 104. The material supply feed 104 may be controlled via a inlet material valve 106. Connected to the pressure vessel 102 is the material conveying line 108 which transports the conveyed material from the pressure vessel 102 to the desired destination.24030P-WO Qlar Europe GmbH

[0093] The system 100 also comprises a compressed gas supply 110 for supplyinggas to the pressure vessel 102 and the material conveying line 108. The compressed gas supply 110 supplies gas via the primary gas feed line 112. This line 112 is connected to the compressor 110 and the conveying line 108.

[0094] The system also comprises a plurality of pressure sensors and a plurality of control valves, as well as a control system 114, for varying the volume of compressed air, controlling conveying pressure and for controlling the position of the control valves.

[0095] The control valves may be on / off valves, or may offer proportional control (i.e. maybe partially opened and closed).

[0096] The inlet material valve 106 is located at the top of the pressure vessel 102, and controls the amount of material entering the top of the pressure vessel 102. Material is typically fed into the pressure vessel 102 via gravity or via mechanical conveying device.

[0097] Typically, the pressure vessel 102 will also comprise a form of a pressure vent valve, this is used to vent residual pressure from the conveying vessel 102 after each batch of material is transferred, and additionally to allow air displaced by material during filling to be vented from the conveying vessel 102. The pressure relief valve 118 usually vents to the feed hopper. A distinct advantage with the invention over the prior art is that it can be used with various material types and conditions, all whilst being easily / electronically adjustable and more energy efficient.

[0098] The system 100 shown also comprises a first control valve 120 which is located on the primary gas feed line 112. The first control valve 120 is located upstream of a branch in the primary gas feed line 112. The primary gas feed line 112 branches into an upper feed line 112a and a lowerfeed line 112b. The upper feed line 112a inserts24030P-WO Qlar Europe GmbH

[0099] the top of the pressure vessel 102, and the lower feed line 112b inserts the bottom of the pressure vessel 102.

[0100] In this example, both upper and lower feed lines comprise fixed orifices 122. The purpose of these orifices or nozzles is not to set the total gas flow to the system but to provide a back pressure at each gas entry point and ensure a distribution of gas flow into the pressure vessel 102. The orifice plates or nozzles will be well be operating well below choked flow condition.

[0101] The pressure vessel pressure in this example is measured via an upper feed line pressure sensor 124. In alternative embodiments, the pressure vessel pressure may be measured within the pressure vessel 102.

[0102] The system 100 also contains a first bypass line 126, which connects the primary gas feed line 112 to the material conveying line 108. The first bypass line is located upstream of the first control valve 120.

[0103] The first bypass line 126 comprises a second control valve 128. The second control valve 128 controls the amount of gas flow through the first bypass line 126. If the second control valve 128 is closed, then the gas flow is forced to travel through the pressure vessel 102 to reach the material conveying line 108. If the second control valve 128 is fully open, then due to the fixed orifices 122 in the primary gas feed line 112 which create some back pressure, the gas flow follows the path of least resistance, and thus diverts immediately to the material conveying line 108, thus bypassing the pressure vessel 102. This can be extremely useful if slugs of material form in the material conveying line 108, as the diverted conveying gas can move the slug on with more force, or break down the slug altogether. The first bypass line 126 and second control valve 128 also coarsely control the rate of material discharge from the conveying vessel 102. By forcing more gas through pressure vessel 10224030P-WO Qlar Europe GmbH

[0104] material is discharged more rapidly, and conversely less material when gas flow is biased through the first bypass line 126.

[0105] A third function of the first bypass line 126 can be to pass all of the gas flow when the outlet valve of the vessel 102 and valve 120 are closed to fill material into the vessel. In the situation control valve 128 is full open.

[0106] The system 100 shown can also comprises a second bypass line 130 this is fitted depending on material characteristics and is not always required. Like the first bypass line 126, connects the primary gas feed line 112tothe material conveying line 108. The second bypass line 130 is located upstream of the first bypass line 126, i.e. is closerto the compressor 110 than the first bypass line 126.

[0107] The second bypass line 130 comprises a third control valve 132. This is used to set the pressure measured by pressure transmitter in the second bypass line 130. By changing the difference in pressure between the supplementary air supply pressure 136 and conveying line pressure transmitter 134, more air can be diverted from the pressure vessel 102 and first bypass line 126 directly in to the conveying pipe line 108 at regular intervals along the length conveying pipe.

[0108] In this embodiment, the second bypass line 130 also comprises a fixed orifice 122. This can be set and sized depending on the material properties to be conveyed, along with the diameter of the conveying pipeline 108.

[0109] Both bypass lines comprise a pressure sensor located down stream of their respective control valves i.e. on the material conveying line 108 side of the control valve.24030P-WO Qlar Europe GmbH

[0110] These pressure sensors are coupled to the control system 114, along with the upper feed line pressure sensor 124 and the primary gas feed line pressure sensor 138, which is located proximate to the compressor, upstream of both bypass lines.

[0111] The invention separates the flow control and air distribution which is typically done by the same devices (distributed square edge orifice plates, delaval nozzles or manually adjusted flow restriction valves etc.).

[0112] The total volume of conveying gas going to the conveying system is measured by a flow meter 150 comprised of an assembly flow meter fixed orifice 152, differential pressure transducer 154 and primary gas feed line pressure sensor 138, which is the typical arrangement of an orifice based flow meter, but any flow meter can be used if it is pressure compensated.

[0113] The primary line control valve 156, which is located downstream of the flow meter 150 operates to maintain a target airflowvolume for conveying, usingthe signalfrom the flow meter 150 to adjust its position (Control loop 1 ).

[0114] The primary line control valve 156 will also have a maximum open setting (Control Loop 2) determined by the pressure in either the vessel (measured by the upper feed line pressure sensor 124) or the first bypass line pressure sensor 134 to ensure the pressure is not allowed to go too high for reliable conveying.

[0115] The proportion of conveying gas going to the vessel is restricted by the fixed orifices 122. These orifices are dimensioned to provide sufficient air volume to empty the vessel and start conveying, but not to necessarily achieve full conveying capacity with all conveyed materials.24030P-WO Qlar Europe GmbH

[0116] Additional air can be directed to the pipeline by the second control valve 128 and the third control valve 132 (optional if supplementary pipeline air injection is used), the second control valve 128 and the third control valve 132 will be proportionally operated between set points according to the pressure in the conveying pipeline measured by the first bypass line pressure sensor 134.

[0117] When the pressure measured by the first bypass line pressure sensor 134 is below the required value, the second control valve 128 and the third control valve 132 will be opened to their minimum value (which could be e.g. 0% to 75%). As the value of the first bypass line pressure sensor 134 increases, the second control valve 128 and the third control valve 132 will proportionally increase their opening to direct more air volume to the pipeline and less to the vessel through the fixed orifices 122, reducing the discharge rate from the vessel and reducing the conveying pressure. (Control Loop 3 and 4)

[0118] When the first bypass line pressure sensor 134 decreases, the second control valve 128 and the third control valve 132 will proportionally decrease their opening to direct more air to the vessel through the fixed orifices 122, to increase the discharge rate from the vessel and increase the conveying pressure. (Control Loop 3 and 4)

[0119] In the case either the first bypass line pressure sensor 134 or the upper feed line pressure sensor 124 exceed upper threshold values, the second control valve 128 will open fully in order to ensure all the conveying air is directed to the conveying pipeline, this should reduce the conveying pressure as the vessel discharge rate had been reduced to a minimum. (Control loop 3)

[0120] During this high pressure situation the third control valve 132 (if pipeline supplementary air points are fitted) will modulate to maintain an increased differential between the second bypass line pressure sensor 136 and the first bypass24030P-WO Qlar Europe GmbH

[0121] line pressure sensor 134, this actsto bias more of the conveying gas flow through the pipeline supplementary injection points and help clear and plugs in the conveying line. (Control loop 4)

[0122] During the operation of the second control valve 128 and the third control valve 132, the primary line control valve 156 will modulate to ensure the required total air flow volume is directed to the system, but will ensure that the pressure isn’t allowed to go above the upper threshold as this could be indicative of pipeline blockages or reduced performance.

[0123] The invention separates the flow control and air distribution which is typically done by the same devices (distributed square edge orifice plates, de Laval nozzles or manually adjusted flow restriction valves). This is a unique advantage over the prior art because it gives more controllability over systems according to the art. The increased controllability also allows the system to be more energy efficient over systems in the art.

[0124] The total volume of the conveying gas going to the conveying system 100 may be calculated from the measured discharge pressure, measured by the primary gas feed line pressure sensor 138.

[0125] The proportion of conveying gas going to the pressure vessel 102 is restricted by fixed orifices the fixed orifices 122 located on the upper and lower feed lines. These orifices are dimensioned to provide sufficient air volume to empty the vessel and start conveying, but not to necessarily achieve full conveying capacity with all conveyed materials and operates in the non-choked region of pressure differentials.

[0126] Additional air can be directed to the pipeline via the second control valve 128 and the third control valve 132. The third control valve 132 should be considered to be24030P-WO Qlar Europe GmbH

[0127] optional, and is only required when supplementary pipeline gas injection is used. The second control valve 128 and the third control valve 132 will be proportionally operated between set points according to the pressure in the conveying pipeline measured by the first bypass line pressure sensor 134.

[0128] When the pressure measured by the first bypass line pressure sensor 134 is below the required value, the second control valve 128 will be opened to its minimum value (which could be for example 0% to 75% of their maximum value). As the value of the first bypass line pressure sensor 134 increases, the second control valve 128 will proportionally increase its opening to direct more air volume to the material conveying line 108 and less to the pressure vessel 102 through the fixed orifices 122, reducingthe discharge rate from the pressure vessel 102 and reducingthe conveying pressure. (Control Loop 2)

[0129] When the first bypass line pressure sensor 134 decreases, the second control valve 128 will proportionally decrease its opening to direct more air to the vessel through the fixed orifices 122, to increase the discharge rate from the pressure vessel 102 and increase the conveying pressure. (Control Loop 2)

[0130] In the case either the first bypass line pressure sensor 134 or the upper feed line pressure sensor 124 exceed upper threshold values, the second control valve 128 will open fully in order to ensure all the conveying gas is directed to the material conveying line 108, which reduces the conveying pressure as the pressure vessel discharge rate is reduced to a minimum. (Control loop 2)

[0131] During this high pressure situation the third control valve 132 (if pipeline supplementary gas points are fitted) will modulate to maintain an increased differential between the second bypass line pressure sensor 136 and the first bypass line pressure sensor 134. This acts to bias more of the conveying gas flowthrough the24030P-WO Qlar Europe GmbH

[0132] pipeline supplementary injection points (i.e. through the fixed orifice 122 on the second bypass line 130) and help clear and plugs in the material conveying line 108. (Control loop 3)

[0133] During normal pressure situation the third control valve 132 (if the second bypass line 130 is fitted) will modulate to maintain a slight differential between the second bypass line pressure sensor 136 and the first bypass line pressure sensor 134. This acts to prevent material flow from conveying pipe 108 into the supplementary air supply pipe.

[0134] There are a number of other distinct advantages with the invention overthe prior art.

[0135] The use of the second control valve 128 to dynamically adjust the conveying gas distribution in the system 100 instead fully alternating the first control valve 120 and second control valve 128 between fully open and fully closed conditions changes the distribution of air between the conveying line 108 and pressure vessel 102 to create a continuous stable flow of material instead of the pulsed flow that alternating that alternating valves 120 and 128 creates.

[0136] The invention allows the system 100 to separate the total gas flow control from the gas flow distribution devices. This allows the use of greatly oversized orifice plates for flow distribution , which results in significantly less energy losses due to the requirement for high differential pressure drops.

[0137] Using the conveying pressure to adjust the conveying gas flow set point during the conveying cycle. This in effect creates a feedback loop within the system 100. The system can therefore dynamically change depending on the conveying conditions.24030P-WO Qlar Europe GmbH

[0138] Another advantage is the ability to dynamically control the flow through the first bypass line 126 and the second bypass line 130 by adjustingthe differential pressure between the third control valve 132 and the second control valve 128.

[0139] The proposed invention has the advantage of allowing the system to operate with lower supply pressures, or conversely to allow the conveying pressures to be much closer to the supply pressure which increases the conveying capacity. These advantages result in lower power consumption per tonne of material conveyed: which has obvious environmental benefits.

[0140] The proposed invention also allows the conveying system to adapt to different conveying conditions, typically defined by the pressures in the conveying vessel, conveying pipeline and required total air flow volume for reliable conveying. This has the advantage of allowing the system to reduce the chances of pipeline blockages without sacrificing energy efficiency.

[0141] The proposed invention also allows tool-less changing of the conveying settings, as the air distribution can be set from the control system, reducing the risks associated with operator mechanical intervention and increasing overall safety.

[0142] The inclusion of the flow meter in the manifold arrangement means that operating condition of the system is always known.

[0143] As the total gas flow and gas flow distribution is all set and controlled electronically it also allows self-optimisation, commissioning algorithms, and / or Al to be applied in the future.

[0144] These distinct advantages are neither taught nor suggested in the prior art documents.24030P-WO Qlar Europe GmbH

[0145] Bulk material may be defined as dry or substantially dry materials which may be in the form of any one of or combination or the following: powder; granular; lumpy etc. Examples of bulk materials may be any one of or combination of the following: any type of foodstuff; minerals; ores; coal; cereals; woodchips; cement; sand; gravel; clay; cement; ash; salt; chemicals; ore; refined minerals; grain; sugar; flourand stone in loose bulk form.

[0146] Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention. For example, any suitable type of sensor may be used to detect and / or measure the velocity of the pneumatically conveyed bulk material.

Claims

24030P-WO Qlar Europe GmbHCLAIMS1. A pneumatic conveying system for conveying dense-phase material, the system comprising:a pressure vessel for receiving material from a material supply feed; a material conveying line for conveying material away from the pressure vessel;a compressed gas supply for supplying gas to the pressure vessel and the material conveying line, wherein gas is supplied to the pressure vessel via a primary gas feed line;a primary line control valve and a flow meter;a plurality of pressure sensors and a plurality of control valves; and a control system for controlling the air flow volume introduced to the system from the compressed gas supply, by controllingthe plurality of control valves, and the primary line control valve;wherein the primary gas feed line comprises a first control valve, and the system further comprises a first bypass line, which connects the primary gas feed line to the material conveying line and is located upstream of the first control valve, and wherein the first bypass line comprises a second control valve;wherein in use, the control system monitors the pressure vessel pressure, the material conveying line pressure, and the compressed gas supply discharge pressure, to maintain a set volume flowrate of the conveying gas along the conveying line.

2. A pneumatic conveying system accordingto claim 1, wherein the output pressure from the compressed gas supply is 1 bar and above.24030P-WO Qlar Europe GmbH3. A pneumatic conveying system according to any preceding claim, wherein the pressure vessel further comprises an outlet material valve, an inlet material valve, and a pressure relief valve.

4. A pneumatic conveying system according to any preceding claim, wherein downstream of the first control valve, the primary gas feed line branches into an upperfeed line, which enters the top of the pressure vessel, and a lowerfeed line, which enters the bottom of the pressure vessel.

5. A pneumatic conveying system according to claim 4, wherein the pressure vessel pressure is measured with an upper feed line pressure sensor.

6. A pneumatic conveying system according to any preceding claim, wherein the system further comprises a second bypass line, which connects the primary gas feed line to the material conveying line and is located upstream of the first bypass line, and wherein the second bypass line comprises a third control valve.

7. A pneumatic conveying system according to any preceding claim, wherein the first bypass line comprises a first bypass line pressure sensor, located downstream of the second control valve.

8. A pneumatic conveying system according to claim 7, wherein the second bypass line comprises a second bypass line pressure sensor, located downstream of the third control valve.

9. A pneumatic conveying system according to any preceding claim, wherein the control system dynamically changes the air flow volume of the conveying gas allowed into the system, using the primary line control valve, using data from the flow meter, which is comprised of a fixed orifice, a pressure sensor, and a differential pressure sensor.24030P-WO Qlar Europe GmbH10. A method of controlling a dense phase pneumatic conveying system according to any of claims 1-9, the method comprising:measuringthe pressure at each pressure sensor;adjusting the control valves and primary line control valve to maintain a set volume flowrate of the conveying gas along the conveying line.

11. A method according to claim 10, wherein when the pressure at the first bypass line pressor sensor is below a threshold value, the second control valve and optionally the third control valve, will be opened to their minimum value, such that the conveying gas is primarily directed towards the pressure vessel.

12. A method according to claim 10, wherein when either the first bypass line pressure sensor or the upper feed line pressure sensor exceed upper threshold values, the second control valve will open fully in order to direct all of the conveying gas to the material conveying line, thus reducing the conveying pressure as the pressure vessel discharge rate is reduced to a minimum.

13. A method according to claim 11 or 12, wherein the third control valve (if fitted) modulates to maintain an increased pressure differential between the second bypass line pressure sensor and the first bypass line pressure sensor, to help clear potential material plugs in the material conveying line.

14. A method according to any of claims 11 to 13, wherein during operation of the second control valve and the third control valve, the control system varies the volume of gas allowed into the system, via the primary line control valve, to ensure the required total air flow volume is directed to the system.

15. A method according to claim 17, wherein the method is a closed-loop feedback method.24030P-WO Qlar Europe GmbH16. A method of filling a pneumatic conveying system according to any of claims 1-9 with material to be conveyed, the method comprising the steps of:stopping the gas flow to the pressure vessel by closing the first control valve; and if the optional vessel outlet valve is not fitted then the primary air control valve, secondary air control valve and tertiary air control valves are also closed to stop air flow completely;fillingthe pressure vessel with material.

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