BACKGROUD
The present invention relates, in general, to flow pattern transition pipes used in pneumatic conveyance systems, and, more specifically, to flow pattern transition pipes used in pneumatic conveyance systems to transfer an instable flow pattern to a relative stabler flow pattern.
Pneumatic conveyance systems are usually used to transport powder such as rice, cement, and ash from one place to another place, in which conditions conveyance capability is the most important parameter. However, in some other situations, for example, when pneumatic conveyance systems are used to convey solid feed in gasification systems, for example, coal gasification systems, conveyance stability is as important as conveyance capability, because an instable conveyance may bring serious problems, such as over heat, to gasifiers.
One main factor affects the conveyance stability is the flow pattern in the pipeline. In dense phase pneumatic conveyance, plug flows or dune flows lead instable flow patterns, whereas uniformity flows lead stable flow patterns. In the gasification systems, solid feed discharged from a feed vessel is tend to form plug flows, in which the solid feed comprises both high concentration parts and low concentration parts, and therefore is extremely instable.
Therefore, there is a need to transfer an instable flow pattern to a relative stabler flow pattern in pneumatic conveyance systems.
BRIEF DESCRIPTION
In one aspect, embodiments of the invention provide a flow pattern transition pipe for use in a pneumatic conveyance system. The flow pattern transition pipe comprises a first expansion pipe section gradually increasing in inner diameter in an axial direction; a second shrink pipe section following the first section from a maximum inner diameter end of the first section, and gradually reducing in inner

diameter in an axial direction away from the first section; and a third pipe section following the second section from a minimum inner diameter end of the second section, with a substantially identical inner diameter smaller than a minimum inner diameter of the first section. A length of the first section is from about 3 to about 5 times of the second section.
In another aspect, embodiments of the invention provide a flow pattern transition pipe for use in a pneumatic conveyance system. The flow pattern transition pipe comprises a first expansion pipe section gradually increasing in inner diameter in an axial direction; a second shrink pipe section following the first section from a maximum inner diameter end of the first section, and gradually reducing in inner diameter in an axial direction away from the first section; and a third pipe section following the second section from a minimum inner diameter end of the second section, with a substantially identical inner diameter smaller than a minimum inner diameter of the first section. The flow pattern transition pipe is configured to enable a carrier gas velocity at the maximum inner diameter end of the first section lower than a saltation velocity and a carrier gas velocity at the minimum inner diameter end of the second section higher than a pick-up velocity, when the flow pattern transition pipe is used in a pneumatic conveyance system for conveying a feed via a carrier gas.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal section view of an exemplary flow pattern transition pipe in accordance with one embodiment of the present invention.
FIG. 2 is a schematic view showing an exemplary pneumatic conveyance system comprising a flow pattern transition pipe in accordance with one embodiment of the present invention.
DETAILED DESCRIPTION
Embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the subsequent description, well¬ed

known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.
The present disclosure provides a flow pattern transition pipe for use in a pneumatic conveyance system. The flow pattern transition pipe comprises a first expansion pipe section gradually increasing in inner diameter in an axial direction; a second shrink pipe section following the first section fi-om a maximum inner diameter end of the first section, and gradually reducing in inner diameter in an axial direction away from the first section; and a third pipe section following the second section from a minimum inner diameter end of the second section, with a substantially identical inner diameter smaller than a minimum inner diameter of the first section.
Upon installing in a conveyance pipeline of a pneumatic conveyance system, the flow pattern transition pipe is capable of transferring an instable conveyance flow pattern to a relative stabler flow pattern, as its first section enables a solid feed transmitted fi'om upstream of the pipeline with an instable flowrate to reduce its superficial velocity and change into a dune-flow, then its second and third sections enable the solid feed transmitted fi"om the second section to increase its superficial velocity and change into an uniformity-flow, and therefore to form a relative stabler flow pattern.
In one aspect, an axial length of the first section is from about 3 to about 5 times of the second section, to ensure an enough time for the solid feed to settle on the first section of the flow pattern transition pipe to form a dune-flow.
In one aspect, the flow pattern transition pipe is horizontally positioned in a pneumatic conveyance system for conveying a feed via a carrier gas, and is configured to enable a carrier gas velocity at the maximum inner diameter end of the first section lower than a saltation velocity and a carrier gas velocity at the minimum inner diameter end of the second section higher than a pick-up velocity. The "saltation velocity" used herein refers to an actual gas velocity at which the particles of a homogeneous solid flow will start to fall out of the gas stream. The "pick-up velocity" used herein refers to a gas velocity required to pick up particles fi-om rest.

The flow pattern transition pipe may further comprises a fourth expansion pipe section following the third section from an end of the third section away from the second section and gradually increases in inner diameter in an axial direction away from the third section. The maximum inner diameter of the fourth section may be substantially equal to the minimum inner diameter of the first section, such that the flow pattern transition pipe can be installed between two sections of a conveyance pipe which have a substantially identical inner diameter, to transfer an instable conveyance flow pattern to a relative stabler flow pattern.
A pneumatic conveyance system comprising the flow pattern transition pipe provided by the present invention is suitable for conveying solid feeds comprising one or more of coal, coke, biomass, bitumen, carbon-containing waste and etc., such as coal powder.
In certain embodiments, the flow pattern transition pipe is capable of reducing a flow fluctuation of a feed passed through the flow pattern transition pipe to less than 10%. In one embodiment, the flow fluctuation of a feed upstream the flow pattern transition pipe is about 10%, and the flow fluctuation of a feed downstream the flow pattern transition pipe is less than 10%.
Referring to FIG. 1, in the illustrated example, a flow pattern transition pipe 100 for use in a pneumatic conveyance system (not shown) comprises, sequentially fi"om an upstream side, a first expansion pipe section 102, a second shrink pipe section 104, a third pipe section 106 and a fourth expansion pipe section 108 along a flow direction 305 of a solid feed 300 flowing therethrough, i.e., an axial direction of the transition pipe 100. In one embodiment, the flow pattern transition pipe 100 extends along a substantially straight axial direction. The first section 102 gradually increases in inner diameter in the axial direction. The second section 104, which follows the first section 102 from a maximum inner diameter end of the first section 102, gradually reduces in inner diameter in the axial direction away from the first section 102. The third section 106, which follows the second section 104 from a minimum inner diameter end of the second section 104, has a substantially identical inner diameter which is smaller than a minimum inner diameter of the first section

102. The fourth section 108, which follows the third section 106 from an end of the third section away from the second section 104, gradually increases in inner diameter in the axial direction away from the third section 106. An axial length Li of the first section 102 is from about 3 to about 5 times of an axial length L2 of the second section 104. The flow pattern transition pipe 100 is configured to enable a carrier gas velocity at the maximum inner diameter end of the first section 102 lower than a saltation velocity and a carrier gas velocity at the minimum inner diameter end of the second section 104 higher than a pick-up velocity when the flow pattern transition pipe 100 is used in a pneumatic conveyance system for conveying a solid feed via a carrier gas.
The flow pattern transition pipe 100 is installed in a pipeline for conveying a solid feed, between two pipe sections 202 and 204 of the pipeline, to transfer an instable conveyance flow pattern to a relative stabler flow pattern. When a solid feed, for example, a powder feed discharged from a feed tank or vessel, flows through the pipeline via a carrier gas, a flow pattern in the pipe section 202 upstream the transition pipe 100 is typically a plug flow, in which the solid feed flow comprises high concentration parts 302 and low concentration parts 304. In such a flow pattern, the flowrate of the solid feed is extremely instable. As the solid feed flows into the first section 102 of the transition pipe 100, its superficial velocity reduces, and the flow pattern changes into dune-flow, in which the solid feed deposits on the bottom of pipe. Sequentially when the solid feed flows into the second and third sections 104 and 106 of the transition pipe, because of increasing of superficial velocity, the flow pattern changes into uniformity-flow, which is a stable flow pattern.
In one embodiment, the two pipe sections 202 and 204, which connected by the transition pipe 100 and therefore located upstream and downstream the transition pipe 100, respectively, have a substantially identical inner diameter, and a minimum inner diameter of the first section 102 of the transition pipe 100 is substantially the same as a maximum iimer diameter of the fourth section 108 of the transition pipe 100. In an alternative embodiment, the two pipe sections 202 and 204 respectively located upstream and downstream the transition pipe 100 have different inner diameters, and a minimum inner diameter of the first section 102 of the

transition pipe 100 is different from a maximum inner diameter of the fourth section 108 of the transition pipe 100.
The flow pattern transition pipe can be located in any position in pipelines of a pneumatic conveyance system, in a horizontal, vertical or angled position, depending on the layout of the pipeline in which it is installed. For example, as shown in FIG.2, the flow pattern transition pipe 100 can be installed in in any position between a feed tank or vessel 502 which discharges a feed with an instable flowrate and an apparatus or system 504 (e.g. a coal gasifier) which can benefit from reducing a flowrate fluctuation of the instable feed and thereby transferring the instable conveyance flow pattern to a relative stabler flow pattern. Moreover, in certain embodiments, there may be one or more aforementioned flow pattern transition pipes installed within a pneumatic conveyance system. For example, two or more flow pattern transition pipes may be installed in a same pipeline of a pneumatic conveyance system. In certain embodiments, the one or more flow pattern transition pipes are positioned in a substantially horizontal position.
While the disclosure has been illustrated and described in typical embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions can be made without departing in any way from the spirit of the present disclosure. As such, further modifications and equivalents of the disclosure herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the disclosure as defined by the subsequent claims.
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WE CLAIM :
1. A flow pattern transition pipe used in a pneumatic conveyance
system, comprising:
a first expansion pipe section gradually increasing in inner diameter in an axial direction;
a second shrink pipe section following the first section from a maximum inner diameter end of the first section, and gradually reducing in inner diameter in an axial direction away fi-om the first section; and
a third pipe section following the second section from a minimum inner diameter end of the second section, with a substantially identical inner diameter smaller than a minimum inner diameter of the first section;
wherein an axial length of the first section is fi-om about 3 to about 5 times of the second section.
2. The flow pattern transition pipe according to claim 1, ftirther comprising a fourth expansion pipe section following the third section fi-om an end of the third section away from the second section, and gradually increasing in inner diameter in an axial direction away fi'om the third section.
3. The flow pattern transition pipe according to claim 2, wherein a minimum iimer diameter of the first section is substantially the same as a maximum inner diameter of the fourth section.
4. The flow pattern transition pipe according to claim 1, wherein the flow pattern transition pipe is configured to enable a carrier gas velocity at the maximum inner diameter end of the first section lower than a saltation velocity when the flow pattern transition pipe is used in a pneumatic conveyance system for conveying a feed via a carrier gas.
5. The flow pattern transition pipe according to claim 1, wherein the flow pattern transition pipe is configured to enable a carrier gas velocity at the

minimum imier diameter end of the second section higher than a pick-up velocity when the flow pattern transition pipe is used in a pneumatic conveyance system for conveying a feed via a carrier gas.
6. The flow pattern transition pipe according to claim 1, wherein the flow pattern transition pipe is configured to enable a flow fluctuation of a feed flowed through the flow pattern transition pipe to be reduced to less than 10%.
7. A pneumatic conveyance system comprising at least one said flow pattern transition pipe according to claim 1.
8. A flow pattern transition pipe used in a pneumatic conveyance system, comprising:
a first expansion pipe section gradually increasing in inner diameter in an axial direction;
a second shrink pipe section following the first section fi"om a maximum inner diameter end of the first section, and gradually reducing in iimer diameter in an axial direction away fi'om the first section; and
a third pipe section following the second section from a minimum inner diameter end of the second section, with a substantially identical inner diameter smaller than a minimum inner diameter of the first section;
wherein the flow pattern transition pipe is configured to enable a carrier gas velocity at the maximum inner diameter end of the first section lower than a saltation velocity and a carrier gas velocity at the minimum inner diameter end of the second section higher than a pick-up velocity, when the flow pattern transition pipe is used in a pneumatic conveyance system for conveying a feed via a carrier gas.
9. The flow pattern transition pipe according to claim 8, fiirther
comprising a fourth expansion pipe section following the third section fi"om an end of
the third section away from the second section, and gradually increasing in inner
diameter in an axial direction away from the third section.
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10. The flow pattern transition pipe according to claim 9, wherein a minimum inner diameter of the first section is substantially the same as a maximum inner diameter of the fourth section.
11. The flow pattern transition pipe according to claim 8, wherein an axial length of the first section is from about 3 to about 5 times of the second section.
12. The flow pattern transition pipe according to claim 8, wherein the flow pattern transition pipe is configured to enable a flow fluctuation of a feed flowed through the flow pattern transition pipe to be reduced to less than 10%.
13. A pneumatic conveyance system comprising at least one saidflow pattern transition pipe according to claim 8.
MANISHA SINGH NAIR
Agent for the Applicant [IN/PA-740J
LEXORBIS
Intellectual Property Practice
709/710, Tolstoy House,
15-17, Tolstoy Marg,
New Delhi-110001