GB2038750A

GB2038750A - Method of and apparatus for conveying particulate material

Info

Publication number: GB2038750A
Application number: GB7935848A
Authority: GB
Original assignee: General Resource Corp
Current assignee: General Resource Corp
Priority date: 1978-12-29
Filing date: 1979-10-16
Publication date: 1980-07-30
Also published as: BE880899A; AU5191079A; JPS5593734A

Abstract

A method of conveying particulate material through a pipeline (18) comprises the steps of continuously metering the particulate material into a pipeline (18), and introducing pulses of highly pressurized gas periodically at spaced intervals (32a)-(32c) along the length of the pipeline and at delayed pulse times respectively sequenced at the spaced intervals in the downstream direction of the pipeline. The particulate material is introduced into the pipeline through a pressure vessel (16) and is propelled by a low pressure and low velocity into one end of the longitudinal pipeline (18). In the event that that particulate material is a powder, the pressurized gas is injected through a line fluidizer. <IMAGE>

Description

SPECIFICATION Method of and apparatus for conveying particulate material This invention relates to methods of and apparatus for conveying particulate material.

It has been the general practice to convey particulate material by mechanical conveying means such as by gravity pipelines which also sometimes utilize booster stations or by mechanical conveying systems. Particulate material which is transported by gravity is a preferred solution if the plant layout and conveying equipment layout permits a gravity conveying system. Where this is not possible, some other conveying system must be used. Mechanical conveying systems of particulate material are less than desirable due to the number of mechanically moving components which are subject to mechanical failure, etc.

Prior art conventional dense phase systems require booster stations which result in product breakage, product degradation, wear on the booster station system components and high energy requirements to convey the particulate material.

U.S. Patent Specification No. 3 973802 discloses an apparatus for conveying particles in suspension in an air stream through a pipeline, and is particularly adapted to convey powder or dust particles in air suspension. This apparatus is useful in conjunction with the present invention for conveying powdered particulate material.

U.S. Patent Specification No. 3 929 379 discloses a method and apparatus for the pneumatic conveying a bulk material. The apparatus includes a conveyor conduit and a bypass conduit which connects to the conveyor conduit by a plurality of connectors which are spaced from each other in the longitudinal direction of the two conduits.Each of the connectors has a non-return valve, while material to be conveyed is introduced into the conveyor conduit at a position downstream of the position at which conveyor gas is introduced into the conduit; when a pressure drop occurs in the conveyor conduit downstream of an accumulation of material, the increased relative pressure in the bypass conduit will cause one or more of the non-return valves in the connectors to open, but only the valve or valves downstream of the accumulation, so that a restricted flow of pressurized gas will be passed into the bypass conduit through the connector or connectors to break up the accumulation of material, while the accumulation is actually being formed.

According to one aspect of the present invention, there is provided a method of conveying particulate materia; comprising the steps of: metering particulate material into one end of a longitudinal pipeline; and introducing pulses of pressurized gas periodically at spaced intervals along the length of said pipeline and at delayed pulse times respectively sequenced at the spaced intervals in the downstream direction of said pipeline whereby said particulate material is propelled along the length of said pipeline by said pulses of pressurized gas, the expansion of said gas in the pipeline serving as a conveying medium.

As used herein, the term "particulate material" includes a particulate, granular, powder, etc. product and is not to be construed as a limiting term in any sense.

In the event that the particulate material is of a texture such as powder, line fluidizers in the pipeline may be used to fluidize the particulate material during its travel through the pipeline.

According to a further aspect of the present invention there is provided apparatus for conveying particulate material comprising: a pipeline; means for loading particulate material into one end of said pipeline; injecting means for injecting pulses of pressurized gas into said pipeline at the spaced intervals along its length, each said pulse having a specific pulse length at a specific frequency; and means for sequencing said pulses along said pipeline in the downstream direction at successive delayed times.

The invention is illustrated, merely by way of example, in the accompanying drawing which is a diagrammatic view of an apparatus according to the present invention for conveying particulate material through a pipeline.

The apparatus indicated generally by the reference numeral 10 includes a hopper 12, having a knife gate 14 at the lower end thereof, for loading particulate material into a pressure vessel 16. The particulate material can be of varying textile and composition, and is loaded into the hopper 12 by any suitable apparatus. The knife gate 14 regulates the flow of the particulate material into the pressure vessel 16. A longitudinal pipeline 18 having a curved section 18a is connected at one end to the pressure vessel 16.

The pipeline 18 transports the particulate material from the pressure vessel 16 to a predetermined location at the other end of the pipeline 18. A low pressure pipe 20 is connected to the curved section 18a ofthe pipeline 18 and an orifice 22 controls the flow of low pressure gas between a source (not shown) of low pressure compressed gas, such as air, from an air compressor, to the pipeline 18. Atakeoff low pressure pipe 24 connects between the low pressure pipe 20 and the pressure vessel 16. A butterfly shut-off valve 20a is positioned in the low pressure pipe 20 and a butterfly shut-off valve 24a is positioned in the takeoff low pressure pipe 24.A high pressure pipe connected to a source (not shown) of high pressure gas, such as air from an air compressor, interconnects a plurality (three shown) of longitudinally spaced pressurized gas holding tanks 28a-28c. While the higher pressure pipe is illustrated having three sections 26a-26c interconnecting three gas holding tanks 28a-28cthis is merely by way of example and for the purposes of illustration only, and the high pressure pipe can have any desired number of sections and there may be any number of gas holding tanks as required for a predetermined length of pipeline 18. Fast acting solenoid-operated diaphragm valves 30a-30c connect the respective gas holding tanks 28a-28cto the respective inlet holes 32a-32c of a suitable diameter in the pipeline 18 at a plurality of longitudinally spaced predetermined intervals on the pipeline 18.

Each of the inlet holes 32a-32e should preferably be of relatively large diameter to permit more easily the instantaneous introduction of pulses of pressurized gas into the pipeline. Each inlet hole 32a-32c can be in the form of a plurality of holes if desired. The more powdery the particulate material becomes, the more it is preferable to incline the inlet holes 32a-32c downstream towards the outlet end of the pipeline 18. A programmable valve controller 34 is connected to control the diaphragm valves 30a-30c. The valve controller 34 can be an electromechanical, analog, or digital controller capable of being programmed with input parameters to activate and open the valves 30a-30c for finite time periods over predetermined frequent intervals of time in a delayed sequence in the downstream direction of the pipeline 18.

In the event that the particulate material is a powder or other fine particulate material, line fluidizers (not shown) can be utilized between the pressure vessel 16 and the curves section 1 8a of the pipeline 18 and line fluidizers can be utilized at or adjacent to each of the diaphragm valves 30a-30cin place of the inlet holes 32a-32c. A suitable line fluidizer is disclosed in U.S. Patent Specification No. 3 973802 where the air inlet connects to the diaphragm valves and the inlet and outlet respectively connects into the pipeline 18.

The size of the longitudinal pipeline 18 is dependent upon the type and quality of particulate material to be conveyed. The physical spacing of the gas holding tanks 28a-28c is dependent upon the size of the pipeline 18 and the mass of the particulate material to be conveyed. The gas holding tanks 28a-28c are sized to permit large volumes of compressed gas to be contained at predetermined intervals along the high pressure pipe, the gas holding tanks preferably being positioned in very close proximity to the pipeline to permit the periodic discharge of large columns of gas instantaneously from the gas holding tanks 28a-28c into the pipeline 18.

Generally, the volume of the gas holding tanks 28a-28c is at least 0.028 m3(1 ft3) of compressed gas under a pressure of 7031 kg/m2 (10 p.s.i.) to 105461 kg ,m2 (150 p.s.i.), although higher pressure could be used, and spaced on the pipeline 18, for example, every 150 cm (5 ft.) to 1220 cm (40 ft.). The time interval spacing of the highly pressurized gas pulses into the pipeline is dependent upon the pipeline diameter, the type of particulate material and gas pressure.

The valve controller 34 is electrically connected to the diaphragm valves 30a-30c and programmed to control the interval of pulses of pressurized gas and the periodic frequency of the pulses discharged into the pipeline 18. An average pulse duration of the pulses of pressurized gas is in the range of 1/10 sec.

to 2 sec., and the periodic frequency of the pulses is in the range of 2 seconds to every 2 minutes. The frequency of the pulses of pressurised gas can also be actuated by a pressure sensor sensing a low pressure in the pipeline 18. A low gas pressure in the range of 3515 kg1m2 (5 p.s.i.) to 17577 kg/m2 (25 p.s.i.) is connected to the low pressure pipeline 20 to propel the particulate material into the pipeline 18 at the curved section 18a of the pipeline 18.

The particulate material is loaded into the hopper 12 and regulated into the pressure vessel 16 by the knife gate 14. The particulate material is then propelled into the pipeline 18 by the low pressure from the low pressure pipe 20 and takeoff low pressure pipe 24a which connects to the pressure vessel 16. The valve controller 34, when switched on to activate the flow of particulate material in the pipeline 18, introduces pulses of pressurized gas into the pipeline 18 through the inlet holes 32a-32c, the pulses having a frequency of between 2 second and 1 minute with each pulse having a duration of 1/10 second to 2 seconds. The pulses of pressurized gas expand in the pipeline and convey the particulate material along the length of the pipeline 18 at a velocity equal to or less than the introduction velocity of the gas pressure pulse into the pipeline 18.The valve controller 34 can also be connected to a pressure sensor in the pipeline 18 to actuate the diaphragm valves on sensing low pressure in the pipeline. The delayed pulse times of the pulses of pressurized gas sequenced along spaced intervals downstream of the longitudinal pipeline 18 by the valve controller 34 is adjusted for the best conveying and propagation results, and is dependent upon the characteristics of the particulate material being conveyed. The longitudinal pipeline characteristics are, for example, diameter, the horizontal angle of the pipeline, and the distance between the gas holding tanks spaced along the pipeline. The delayed pulse times are determined empirically, taking the relevant parameters into consideration, and fed to the valve controller 34.

In the event that the particulate material is a powder or other similar type of material, the gas pulses can be injected through line fluidizers for fluidizing air into the product.

The gas holding tanks 28a-28c should be positioned close the pipeline 18 to permit maximum flow of the gas into the pipeline 18. The holding tanks 28a-28c are separated from the pipeline 18 only by the diaphragm valves 30a-30c to permit optimum gas flow.

Claims

1. A method of conveying particulate material comprising the steps of: metering particulate material into one end of a longitudinal pipeline; and introducing pulses of pressurized gas periodically at spaced intervals along the length of said pipeline and at delayed pulse times respectively sequenced at the spaced intervals in the downstream direction of said pipeline whereby said particulate material is propelled along the length of said pipeline by said pulses of pressurized gas, the expansion of said gas in the pipeline serving as a conveying medium.

2. A method as claimed in claim 1 in which the duration of each pulse of pressurized gas is between one-tenth to 2 seconds.

3. A method as claimed in claim 1 or 2 in which said frequency of said pulses of pressurized gas is between 2 seconds to 2 minutes.

4. A method as claimed in any preceding claim in which said pulses of pressurized gas have a pressure between 7031 kg/m2 and 105461 kg/m2.

5. A method as claimed in any preceding claim including fluidizing said particulate material at each of said spaced intervals.

6. Apparatus for conveying particulate material comprising: a pipeline; means for loading particulate material into one end of said pipeline; injecting means for injecting pulses of pressurized gas into said pipeline at the spaced intervals along its length, each said pulse having a specific pulse length at a specific frequency; and means for sequencing said pulses along said pipeline in the downstream direction at successive delayed times.

7. An apparatus as claimed in claim 6 in which said injecting means comprises a plurality of pressure vessels for containing compressed gas, each positioned adjacent said pipeline whereby said compressed gas expands into said pipeline.

8. An apparatus as claimed in claim 7 including a diaphragm valve between each of said pressure vessels and said pipeline.

9. An apparatus as claimed in claim 8 including activation means coupled to each of said diaphragm valves for sequentially activating said valves along the longitudinal length of said pipeline.

10. A method of conveying particulate material substantially as herein described with reference to the accompanying drawing.

11. Apparatus for conveying particulate material substantially as herein described with reference to and as shown in the accompanying drawing.