Method and apparatus for minimizing ice buildup in and at the exit of a blast nozzle - Patents.com

Abstract

The method and apparatus prevents ice from obstructing the flow of cryogenic particles entrained in the flow exiting the blast nozzle during continuous operation of the particle blast system. A fluid stream having an appropriate temperature, moisture content, and flow rate flows through an annular passage surrounding the nozzle.

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for minimizing or eliminating ice buildup on the inner nozzle interior surface and adjacent the nozzle exit. [Background technology]

[0002] Particle blasting systems utilizing various types of blasting media are known. Systems for entraining cryogenic particles, such as solid carbon dioxide particles, in a transport fluid and for directing the entrained particles at an object / target, as well as various components associated therewith, such as nozzles, are known and include, for example, U.S. Pat. Nos. 4,744,181; 4,843,770; 5,018,667; 5,050,805; 5,071,289; 5,188,151; 5,249,426; 5,288,028; 5,301,509; 5,473,903; 5,520,572; 6,024,304; 6,042,451; and the like. Nos. 8, 6,346,035, 6,524,172, 6,695,679, 6,695,685, 6,726,549, 6,739,529, 6,824,450, 7,112,120, 7,950,984, 8,187,057, 8,277,288, 8,869,551, 9,095,956, 9,592,586, 9,931,639, 10,315,862, and 10,737,890, all of which are incorporated herein by reference in their entireties.

[0003] Further, U.S. Patent Application Publication No. 2009 / 0093196, which is U.S. Patent Application No. 11 / 853,194, filed September 11, 2007, for Particle Blast System With Synchronized Feeder and Particle Generator; U.S. Provisional Patent Application No. 61 / 589,551, filed January 23, 2012, for Method And Apparatus For Sizing Carbon Dioxide Particles; U.S. Provisional Patent Application No. 61 / 592,313, filed January 30, 2012, for Method And Apparatus For Dispensing Carbon Dioxide Particles; U.S. Patent Application No. 13 / 475,454, filed May 18, 2012, for Method And Apparatus For Forming Carbon Dioxide Pellets; Apparatus Including At Least An Impeller Or Diverter And For Dispensing Carbon Dioxide Particles And Method Of U.S. Patent Application Publication No. 2014 / 0110510, which is U.S. Patent Application No. 14 / 062,118, filed October 24, 2013, for Use; U.S. Patent Application Publication No. 2015 / 0166350, which is U.S. Patent Application No. 14 / 516,125, filed October 16, 2014, for Method And Apparatus For Forming Solid Carbon Dioxide; U.S. Patent Application Publication No. 2017 / 0106500, which is U.S. Patent Application No. 15 / 297,967, filed October 19, 2016, for Blast Media Comminutor; U.S. Patent Application No. 15 / 961,321, filed April 24, 2018, for Particle Blast Apparatus; U.S. Patent Application No. 16 / 999,633, filed August 21, 2020, for Particle Blast Apparatus and Method;U.S. Patent Application No. 17 / 139,292, filed December 31, 2020 for Method and Apparatus for Enhanced Blast Stream, Particle Blast Apparatus and Method; and U.S. Provisional Patent Application No. 63 / 185,467, filed May 7, 2021 for Method and Apparatus For Forming Solid Carbon Dioxide, all of which are incorporated herein by reference in their entireties.

[0004] To the extent that the material incorporated by reference conflicts with the disclosure of this patent, the disclosure of this patent controls.

[0005] Although the patent specifically refers to carbon dioxide in describing the innovation, the innovation is not limited to carbon dioxide but rather may be applied to any suitable cryogenic material, and therefore, references to carbon dioxide in this specification and claims, unless expressly so stated, should be read as including any suitable cryogenic material, and not as limited to carbon dioxide.

[0006] As is known, cryogenic particle blasting systems, such as carbon dioxide particle blasting systems, discharge a stream of cryogenic particles, such as carbon dioxide particles, entrained in a transport gas from a blast nozzle. The size of the particles used may depend on the particular application for which the blasting system is used. U.S. Patent No. 5,520,572 shows a particle blasting apparatus that entrains small particles in a transport gas stream. The entrained stream of particles flows through a delivery hose to a blast nozzle for eventual use, such as being directed at a workpiece or other target. The exiting stream may be subsonic, sonic, or supersonic.

[0007] Continuous operation of several blast nozzles under certain flow conditions and under certain ambient conditions can result in the accumulation of water ice on the outside of the nozzle. This accumulation can grow over time during continuous use of the system and can eventually impede or block the flow out of the outlet of the blast nozzle. The water ice that forms on the outside of the nozzle at the outlet can break off and become entrained in the outgoing flow of entrained particles, potentially damaging the target or workpiece. Summary of the Invention [Means for solving the problem]

[0008] The innovation can reduce, minimize, and eliminate ice buildup on the blast nozzle interior surface and outlet, reducing or completely eliminating blockages and blockages. According to the innovation, at least a portion of the length of the blast nozzle is surrounded by a fluid stream that is warm enough to reduce or eliminate ice buildup.

[0009] According to one aspect of the innovation, the fluid stream may be annular.

[0010] According to another aspect of the innovation, the fluid stream may flow through an annular passage defined by a structure surrounding the exterior of the blast nozzle.

[0011] In a further aspect of the innovation, the outlet of the annular passage may be proximate to the outlet of the blast nozzle.

[0012] The accompanying drawings illustrate embodiments that serve to explain the principles of the innovation. [Brief description of the drawings]

[0013] [Figure 1] 1 diagrammatically illustrates one embodiment of a particle blasting system constructed in accordance with one or more teachings of the present innovation. [Diagram 2]FIG. 1 is an exploded view of one embodiment of a shrouded blast nozzle assembly constructed in accordance with one or more teachings of the present innovation. [Diagram 3] FIG. 3 is a cross-sectional view of the shrouded blast nozzle assembly of FIG. 2 taken in a plane through the central axis. [Figure 4] FIG. 3 is an enlarged partial view of the discharge end of the shrouded blast nozzle assembly of FIG. [Diagram 5] FIG. 2 is an end view of the nozzle 20. [Figure 6] 3 is a cross-sectional view of the shroud of the blast nozzle assembly of FIG. 2 taken in a plane through the central axis. [Figure 7] FIG. 1 is a cross-sectional view of an alternative embodiment of a shrouded blast nozzle assembly constructed in accordance with one or more teachings of the present innovation, taken in a plane through the central axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In the following description, like reference numerals refer to like or corresponding parts throughout the several views. Also, in the following description, it should be understood that terms such as front, back, inside, outside, etc. are words of convenience and are not to be construed as limiting terms. The terms used in this patent are not intended to be limiting insofar as the devices described herein or portions thereof may be mounted or utilized in other orientations. Referring more particularly to the drawings, one or more embodiments constructed in accordance with the teachings of the present innovation are described.

[0015] Any patent, publication, or other disclosure material that is incorporated herein by reference, in whole or in part, is understood to be incorporated herein only to the extent that the incorporated material does not contradict existing definitions, statements, or other disclosure material set forth in this disclosure, and therefore, to the extent necessary, the present disclosure as expressly set forth herein takes precedence over any conflicting material incorporated herein by reference.

[0016] 1, a particle blast system 2 is shown diagrammatically comprising, in the depicted embodiment, a source 4 of entrained cryogenic particles in a flow of transport gas (also referred to herein as an entrained cryogenic particle source 4), an entrained flow delivery hose 6, a hand control 8, a discharge or blast nozzle assembly 10, and a shroud fluid hose 12. A fluid source 14 is connected to the shroud fluid delivery hose 12 and configured to supply shroud fluid to the discharge assembly 10. The fluid source 14 is shown as including a pressurized fluid source 16, such as an air compressor 16, and an aftercooler 26. The entrained cryogenic particle source 4 may be connected directly to the pressurized fluid source 16 as shown, which serves as a source of transport gas for the entrained cryogenic particle source 4, or may be connected to the aftercooler 26 for that source of transport gas.

[0017] The source 4 of entrained cryogenic particles may be of any configuration that entrains cryogenic particles into the transport gas stream. The source 4 of entrained cryogenic particles is shown diagrammatically as including a hopper 4a, which serves as a source of cryogenic particles for the feed section 4b. The feed section 4b may be of any suitable configuration, such as including a feed rotor (not shown) that introduces the particles into the transport gas stream. In the depicted embodiment, the cryogenic particles may be carbon dioxide particles, and although the innovation is described below in connection with the use of carbon dioxide particles as the cryogenic particles, such reference does not limit the innovation to the use of carbon dioxide particles. Thus, the source 4 of cryogenic particles entrained in the stream of entrained cryogenic particles is also referred to herein as the source 4 of entrained carbon dioxide particles, and does not limit the innovation with respect to a particular type of cryogenic particle.

[0018] The aftercooler 26 reduces the amount of steam in the pressurized fluid provided by the compressor 16. In the depicted embodiment, the pressurized fluid is air and the aftercooler 26 reduces the amount of water vapor therein. A separator may be combined with the aftercooler 26. Alternatively, a fluid heater may be used as part of or to replace the aftercooler 26 to better ensure that the temperature of the fluid stream entering the discharge assembly 10 through the shroud fluid hose 12 prevents the formation of water ice in the areas outside the nozzle 20 and over the interior surface 20h of the nozzle 20.

[0019] The hand control 8 holds the discharge assembly 10 and includes controls that communicate with a controller (not shown) to control operation of the blast system 2. The hand control 8 may be used by an operator to orient the discharge assembly 10 towards a target or workpiece such that entrained flow exiting the discharge assembly 10 impacts the target or workpiece. The discharge assembly 10 may be held by any suitable support other than the hand control 8, such as held by a controllable / movable structure such as a robot, or may be stationary, in which case the target or workpiece may be moved relative to the discharge assembly 10.

[0020] With reference to FIG. 2, an exploded view of one embodiment of a discharge assembly 10, also referred to herein as a blast nozzle assembly 10, is shown. In the depicted embodiment, the blast nozzle assembly 10 includes a nozzle base 18, a nozzle 20, a shroud 22, and a fitting 24. With reference also to FIG. 3, in the depicted embodiment, the nozzle base 18 includes a first male thread 18a for connecting the nozzle base 18 to a hand control 8 or any other support. The nozzle base 18 includes a second male thread 18b configured to threadably engage a first female thread 22a of the shroud 22, such that the nozzle base 18 may be attached to the shroud 22. The nozzle base 18 includes a female thread 18c (see FIG. 3), configured to threadably engage the male thread 20a of the nozzle 20. Threads are not the only way these components may be connected together. Any suitable connection configuration between the nozzle base 18, the nozzle 20, and the shroud 22 may be used. Although manufacturing techniques allow the blast nozzle assembly to be of unitary construction, there are advantages to using assemblable components, such as component group interchangeability that allows common parts to be assembled into different final assemblies for specific operating parameters and applications.

[0021] 3 constitute a converging-diverging nozzle which, when operated with appropriate parameters, discharges a supersonic entrained particle stream from outlet 20c. Alternatively, nozzle base 18 and nozzle 20 may be configured as a subsonic sonic nozzle or a sonic nozzle.

[0022] In the depicted embodiment, the nozzle base 18 includes an internal passage 18d that converges in a direction (flow direction) from an inlet 18e to an outlet 18f. In the depicted embodiment, the outlet 18f is formed at the upstream end of the internal threads 18c such that when connected to the nozzle 20, the outlet 18f abuts proximate to and coextensive with the inlet 20d of the nozzle 20.

[0023] Nozzle 20 includes an internal passage 20e which, in the depicted embodiment, diverges in a direction from inlet 20d towards outlet 20c. Internal passages 18d and 20e thus form a continuous converging-diverging passage whose throat (where sonic flow occurs, as is well known) is at outlet 18f / inlet 20d.

[0024] The combined internal passages 18d and 20e of the nozzle base 18 / nozzle 20 form a nozzle passageway. Whether the nozzle passageway is configured as a subsonic, sonic, or supersonic nozzle, the nozzle passageway is connectable to a source 4 of entrained carbon dioxide particles disposed in fluid communication therewith.

[0025] Referring also to FIG. 6, the shroud 22 defines an internal passage 22b having an outlet 22c. The shroud 22 includes a plurality of inlets 22d in fluid communication with the internal passage 22b at an end to which the nozzle base 18 is attached. In the depicted embodiment, there are two inlets 22d, although a single inlet or three or more inlets may be used. Each respective inlet 22d includes a respective second internal thread 22e configured to mate with a respective fitting 24. The inlets 22d are configured to be connected to a fluid source 14, which in the depicted embodiment includes a pressurized fluid source 16 and an aftercooler 26 (or, alternatively, a fluid heater or an aftercooler and heater, as previously described). In the depicted embodiment, the shroud fluid hose 12 places the inlet 22d and thus the internal passage 22b in fluid communication with the fluid source 18. Additionally, the fluid source 14 to the shroud fluid hose 12 may be provided separately from the pressurized fluid provided by the compressor 16 to the supply portion 4b.

[0026] As seen in FIG. 3, the blast nozzle assembly 10 includes a nozzle 20 coupled to a nozzle base 18 as described above, which is coupled to a shroud 22 via a second external thread 18b / first internal thread 22a, thereby disposing the nozzle 20 within the internal passage 20e. The nozzle 20 includes a plurality of spacers or standoffs 20b (see FIG. 5) extending radially outward from an outer surface 20f of the nozzle 20 proximate the outlet 20c. As seen in FIG. 5, the spacers 20b are radially spaced apart from one another by 120° in the depicted embodiment. The spacers 20b are spaced apart longitudinally (along the nozzle axis 20g) from the inlet 20d toward the outlet 20c and are positioned to support the nozzle 20 against the inner surface 22f and to align, within tolerance, the nozzle axis 20g with the shroud axis 22g. Thus, the outer diameter enclosed by the spacers 20b allows the nozzle 20 to be inserted into the internal passage 22b over the first female threads 22a and rotated within the internal passage 22b when the second male threads 18b of the nozzle base 18 are rotated to secure the nozzle base 18 to the shroud 22, while still providing support and alignment to the nozzle 20. Any suitable number and spacing of spacers 20b may be used. For example, each spacer 20b may be positioned at a different axial location, while still providing support and alignment that may improve fluid flow through the internal passage 22b of the shroud 22.

[0027] The placement / installation of nozzle 20 within shroud 22 defines from inner passage 22b an annular passage 22b' bounded for a majority of its length by outer surface 20f and inner surface 22f. Inlet 22d is in fluid communication with annular passage 22b'. When inlet 22d is connected to fluid source 14, annular passage 22b' is in fluid communication with fluid source 14.

[0028] 4, nozzle 20 and shroud 22 are positioned relative to one another such that outlet 20c may be aligned with outlet 22c. As will be described below, there are functional limits to the relative positions of outlet 20c and outlet 22c other than precise alignment.

[0029] During operation of the particle blast system 2, carbon dioxide particles are introduced into the flow of transport gas from the compressor 16 by the supply section 4b. The flow of entrained carbon dioxide particles travels through the entrained flow delivery hose 6 to the nozzle base 18. In the depicted embodiment, the flow accelerates as it flows through the converging internal passage 18d, reaching Mach 1 at the throat (outlet 18f / inlet 20d). The flow is then further accelerated by the diverging internal passage 20e, becoming supersonic, and finally exiting through the outlet 20c.

[0030] Regardless of whether the flow exiting the nozzle 20 is subsonic, sonic, or supersonic, the temperature of the flow leaving the outlet 20c is cryogenically very cold, for example, as low as -200°F.

[0031] Regardless of the actual temperature of the flow, if the temperature of the exterior surface of an unshrouded blast nozzle in accordance with the teachings of this innovation is below freezing, moisture in the surrounding environment will form water ice on the exterior surface of the nozzle. Under certain operating parameters, ice formed on the exterior surface of the nozzle adjacent the outlet will accumulate and eventually extend into the flow path of the exiting flow of entrained particles, reducing the outlet area and thus the effectiveness of the exiting flow. The outlet may become completely blocked.

[0032] In accordance with the teachings of the present innovation, the blast nozzle assembly 10 includes a nozzle 20 disposed at least partially within a shroud 22. The nozzle 20 is surrounded by a fluid stream, for example, but not limited to, air, flowing through an annular passage 22b'. The temperature, moisture content, and flow rate of this fluid stream are desirably sufficient to prevent ice from impeding the outgoing flow of entrained particles for an indefinite period of time during continuous operation of the particle blast system 2. If the temperature, moisture content, and flow rate of this fluid stream are sufficient to prevent ice from impeding the outgoing flow of entrained particles during continuous operation of the particle blast system 2 for the entire design period for continuous operation, performance may be acceptable.

[0033] Thus, in accordance with the teachings of the present innovation, ice does not accumulate on the nozzle or shroud during continuous operation, at least over the design period for continuous operation, resulting in obstruction of the outgoing flow of entrained particles. The temperature, moisture and flow rate of the fluid stream through the annular passage 22b' are sufficient to prevent ice from obstructing the flow of the fluid stream through the annular passage 22b'.

[0034] In the depicted embodiment, air is the fluid stream flowing through the annular passage 22b'. The temperature of the air at the outlet 22c is desirably above the dew point temperature of the ambient conditions and has a low moisture content. In the depicted embodiment, the aftercooler 26 reduces the moisture content of the air flowing into the annular passage 22b'. The flow rate of the fluid stream through the annular passage 22b' should be sufficient to perform the indicated functions, but is not itself intended to impede or affect the flow exiting the nozzle 20.

[0035] The nozzle 20 and shroud 22 may be made of any suitable material. For example, the nozzle base 18, nozzle body 20 and shroud 22 may be aluminum or titanium. Titanium provides strength and is resistant to damage even at small wall thicknesses. Titanium may also help avoid static electricity buildup if there is a suitable path for static electricity discharge.

[0036] The exit plane of nozzle exit 20c is shown as aligned with exit 22c in the depicted embodiment. There is a functional range for the relative location of exit 20c and exit 22c other than the exact alignment related to the temperature, moisture content and flow rate of the fluid stream through annular passage 22b'. Recessing exit 20c in annular passage 22b' relative to exit 22c may require the fluid stream flowing through annular passage 22b' to have a higher temperature, lower moisture content, or higher flow rate to prevent ice from blocking the outgoing flow of entrained particles during continuous operation of particle blasting system 2 throughout the entire design period for continuous operation. Insufficient temperature, moisture content, and flow rate parameters of the fluid stream flowing through annular passage 22b' may result in ice buildup and harmful bridging between the shroud and the nozzle.

[0037] The length of the nozzle surrounded by the annular passage should be sufficient to prevent ice from obstructing the outgoing flow of entrained particles during continuous operation of the particle blasting system 2 for the entire design period for continuous operation, and may depend on the temperature, water content, and flow parameters of the fluid stream flowing through the annular passage. The portion of the nozzle surrounded by the annular passage may include a diverging portion from the throat to the outlet as shown in Figures 2-6. The shrouded portion may include a converging portion.

[0038] 7 illustrates an alternative embodiment of the shrouded blast nozzle assembly 110 in which the annular passage 122b' does not surround the entire length of the shroud 122. A seal 122a is formed between the shroud 122 and the nozzle 120. The embodiment of FIG. 7 may not provide adequate minimization of water ice accumulation on the interior surface of the nozzle for all operating parameters.

[0039] Explicit definition "Based on" means that something is at least partially determined by the thing that is described as "based on." If something is completely determined by something, it will be described as "based solely on" that thing.

[0040] "Processor" refers to a device that may be configured, individually or in combination with other devices, to perform various functionalities described in this disclosure. Examples of "processors" include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), programmable logic controllers (PLCs), state machines, gate logic, and discrete hardware circuits. The phrase "processing system" is used to refer to one or more processors, which may be contained in a single device or distributed among multiple physical devices.

[0041] A statement that a processing system is "configured to" perform one or more operations means that the processing system includes data (which may include instructions) that can be used in performing the particular operations that the processing system is "configured to perform. For example, in the case of a computer (a type of "processing system"), installing Microsoft Word on the computer causes the computer to be "configured" to function as a word processor, using the instructions in Microsoft Word in combination with other inputs, such as an operating system, and various peripheral devices (e.g., keyboard, monitor, etc.).

[0042] The foregoing description of one or more embodiments of the present innovation has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments have been chosen and described to best illustrate the principles of the present innovation and its practical application, thereby enabling those skilled in the art to best utilize the present innovation in various embodiments and with various modifications as may be suited to the particular use contemplated. While only a limited number of embodiments of the present innovation have been described in detail, it should be understood that the present innovation is not limited in scope to the details of construction and arrangement of components set forth in the foregoing description or illustrated in the drawings. The present innovation is capable of other embodiments and may be practiced or carried out in various ways. Also, specific terminology has been used for the sake of clarity. It is understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish the same purpose. It is intended that the scope of the present invention be defined by the claims appended hereto.

[0043] [Embodiment] (1) A blast nozzle assembly comprising: a. a shroud including a shroud passage, the shroud passage comprising: i. an inner surface of a shroud passage; ii. A shroud outlet; and iii. at least one shroud inlet, each said at least one shroud inlet in fluid communication with said internal passage and said shroud outlet, each at least one shroud inlet configured to be connected to a source of shroud fluid; iv. a shroud flow direction defined in a direction from said at least one shroud inlet to said shroud outlet; a shroud including: b. a blast nozzle including an exterior surface and an internal nozzle passage configured to convey an entrained flow of cryogenic particles therethrough, the internal nozzle passage comprising: i. a nozzle inlet; ii. A nozzle outlet; iii. a nozzle flow direction defined in a direction from the nozzle inlet to the nozzle outlet; A blast nozzle including: Including, The blast nozzle assembly, wherein the blast nozzle is attached to the shroud such that at least a portion of the outer surface of the blast nozzle defines an inner boundary of the shroud passage. (2) A blast nozzle assembly as described in embodiment 1, wherein the nozzle outlet is aligned with the shroud outlet. (3) A blast nozzle assembly as described in embodiment 1, wherein the nozzle outlet is disposed downstream of the shroud outlet. (4) A blast nozzle assembly as described in embodiment 1, wherein the shroud passage is annular. (5) The blast nozzle assembly of claim 1, wherein the blast nozzle includes a plurality of spacers configured to support the nozzle against the shroud passage inner surface.

[0044] (6) The blast nozzle assembly of claim 5, wherein the nozzle includes a nozzle axis, the shroud includes a shroud axis, and the plurality of spacers are configured to align the nozzle axis with the shroud axis. (7) The blast nozzle assembly of claim 1, wherein the internal nozzle passage includes a converging portion and a diverging portion disposed downstream of the converging portion. (8) A particle blasting system configured for cryogenic particles, comprising: a. A source of entrained cryogenic particles; b. A source of shroud fluid; c. A blast nozzle assembly comprising: i. a shroud including a shroud passage, said shroud passage comprising: (a) an inner surface of a shroud passage; (b) a shroud outlet; (c) at least one shroud inlet, each said at least one shroud inlet in fluid communication with said internal passageway and said shroud outlet, each said at least one shroud inlet in fluid communication with a source of said shroud fluid; (d) a shroud flow direction defined in a direction from the at least one shroud inlet to the shroud outlet; and a shroud including: i. a blast nozzle including an exterior surface and an internal nozzle passage configured to convey an entrained flow of cryogenic particles therethrough, said internal nozzle passage comprising: (a) a nozzle inlet in fluid communication with a source of entrained cryogenic particles; (b) a nozzle outlet; (c) a nozzle flow direction defined in a direction from the nozzle inlet to the nozzle outlet; A blast nozzle including: a blast nozzle assembly including: Including, The blast nozzle is attached to the shroud such that at least a portion of the outer surface of the blast nozzle defines an inner boundary of the shroud passage. (9) The particle blasting system of embodiment 8, wherein the source of shroud fluid is configured to supply a shroud fluid having a temperature greater than a dew point temperature of ambient conditions. (10) The particle blasting system of claim 8, further comprising an aftercooler configured to reduce a moisture content of the shroud fluid.

[0045] (11) The particle blasting system of claim 8, further comprising a heater configured to increase a temperature of the shroud fluid. (12) A particle blasting system as described in embodiment 8, wherein the source of shroud fluid is configured to supply shroud fluid at a temperature, moisture content and flow rate sufficient to prevent ice from forming adjacent the nozzle outlet and obstructing the outgoing flow of entrained particles over a period of time during continuous operation of the particle blasting system. (13) The particle blasting system of embodiment 12, wherein the particle blasting system has a design period for continuous operation, and the source of shroud fluid is configured to supply shroud fluid during continuous operation of the particle blasting system, throughout the design period for the continuous operation, at a temperature, moisture content, and flow rate sufficient to prevent ice from forming adjacent the nozzle outlet and obstructing the outgoing flow of entrained particles. (14) A method of reducing ice buildup within and at an outlet of a blast nozzle having an entrained cryogenic particle flow therethrough, comprising the steps of: a. flowing cryogenic particles entrained in a flow of transport gas through and out of the outlet of the blast nozzle for a period of time; b. while performing the flowing step, flowing a fluid adjacent to and along a portion of an exterior surface of the blast nozzle proximate to the outlet of the blast nozzle, the fluid having a temperature, moisture content and flow rate sufficient to prevent impeding flow of cryogenic particles through and out of the outlet of the blast nozzle during said period; A method comprising: 15. The method of claim 14, further comprising removing moisture from the fluid prior to performing the step of flowing the fluid.

[0046] 16. The method of claim 14, further comprising the step of heating the fluid prior to performing the step of flowing the fluid. 17. The method of claim 14, wherein the step of flowing the fluid includes flowing the fluid through an annular passage defined in part by the exterior surface of the blast nozzle. 18. The method of claim 14, wherein the temperature of the fluid is above the dew point temperature of ambient conditions. (19) A method of reducing ice buildup within and at an outlet of a blast nozzle having an entrained cryogenic particle flow therethrough, comprising the steps of: a. flowing cryogenic particles entrained in a flow of transport gas through and out of the outlet of the blast nozzle for a period of time; b. while performing the flowing of cryogenic particles, flowing a fluid adjacent to and along a portion of an exterior surface of the blast nozzle proximate to the outlet of the blast nozzle, the fluid having a temperature, moisture content and flow rate; c. controlling the temperature, sufficient moisture, and flow rate of the fluid to prevent impeding flow of cryogenic particles through and out of the outlet of the blast nozzle during the period of time; A method comprising:

Claims

1. 1. A blast nozzle assembly comprising: a. A shroud including a shroud passage, said shroud passage comprising: i. A shroud passage inner surface; ii. A shroud outlet; iii. at least one shroud inlet, each said at least one shroud inlet in fluid communication with said internal passage and said shroud outlet, each said at least one shroud inlet configured to be connected to a source of shroud fluid; iv. a shroud flow direction defined in a direction from the at least one shroud inlet to the at least one shroud outlet; a shroud including: b. a blast nozzle including an exterior surface and an internal nozzle passage configured to convey an entrained flow of cryogenic particles therethrough, said internal nozzle passage comprising: i. a nozzle inlet; ii. A nozzle outlet; iii. A nozzle flow direction defined in a direction from the nozzle inlet to the nozzle outlet; A blast nozzle including: Including, The blast nozzle assembly, wherein the blast nozzle is attached to the shroud such that at least a portion of the outer surface of the blast nozzle defines an inner boundary of the shroud passage.

2. The blast nozzle assembly of claim 1 , wherein the nozzle outlet is aligned with the shroud outlet.

3. The blast nozzle assembly of claim 1 , wherein the nozzle outlet is disposed downstream of the shroud outlet.

4. The blast nozzle assembly of claim 1 , wherein the shroud passage is annular.

5. The blast nozzle assembly of claim 1 , wherein the blast nozzle includes a plurality of spacers configured to support the nozzle against the shroud passage inner surface.

6. The blast nozzle assembly of claim 5 , wherein the nozzle includes a nozzle axis, the shroud includes a shroud axis, and the plurality of spacers are configured to align the nozzle axis with the shroud axis.

7. The blast nozzle assembly of claim 1 , wherein the internal nozzle passage includes a converging portion and a diverging portion disposed downstream of the converging portion.

8. 1. A particle blasting system configured for cryogenic particles, comprising: a. a source of entrained cryogenic particles; b. A source of shroud fluid; c. A blast nozzle assembly comprising: i. a shroud including a shroud passage, said shroud passage comprising: (a) a shroud passage inner surface; (b) a shroud outlet; (c) at least one shroud inlet, each said at least one shroud inlet in fluid communication with said internal passage and said shroud outlet, each said at least one shroud inlet in fluid communication with a source of said shroud fluid; (d) a shroud flow direction defined in a direction from the at least one shroud inlet to the at least one shroud outlet; a shroud including: i. a blast nozzle including an exterior surface and an internal nozzle passage configured to convey an entrained flow of cryogenic particles therethrough, said internal nozzle passage comprising: (a) a nozzle inlet in fluid communication with a source of entrained cryogenic particles; (b) a nozzle outlet; (c) a nozzle flow direction defined in a direction from the nozzle inlet to the nozzle outlet; A blast nozzle including: a blast nozzle assembly including: Including, The blast nozzle is attached to the shroud such that at least a portion of the outer surface of the blast nozzle defines an inner boundary of the shroud passage.

9. The particle blasting system of claim 8 , wherein the source of shroud fluid is configured to supply a shroud fluid having a temperature greater than a dew point temperature of ambient conditions.

10. The particle blast system of claim 8 including an aftercooler configured to reduce a moisture content of the shroud fluid.

11. The particle blasting system of claim 8 including a heater configured to increase a temperature of the shroud fluid.

12. 10. The particle blasting system of claim 8, wherein the source of shroud fluid is configured to supply shroud fluid at a temperature, moisture content and flow rate sufficient to prevent ice from forming adjacent the nozzle outlet and obstructing the outgoing flow of entrained particles over a period of time during continuous operation of the particle blasting system.

13. 13. The particle blasting system of claim 12, wherein the particle blasting system has a design period for continuous operation, and the source of shroud fluid is configured to supply shroud fluid during continuous operation of the particle blasting system throughout the design period for continuous operation at a temperature, moisture content and flow rate sufficient to prevent ice from forming adjacent the nozzle outlet and obstructing the outgoing flow of entrained particles.

14. 1. A method for reducing ice build-up within and at an outlet of a blast nozzle having a flow of entrained cryogenic particles passing therethrough, the method comprising: a. flowing cryogenic particles entrained in a flow of transport gas through and out of the outlet of the blast nozzle for a period of time; b. while performing the flowing step, flowing a fluid adjacent to and along a portion of an exterior surface of the blast nozzle proximate to the outlet of the blast nozzle, the fluid having a temperature, moisture content and flow rate sufficient to prevent impeding flow of cryogenic particles through and out of the outlet of the blast nozzle during said period; A method comprising:

15. The method of claim 14, further comprising removing moisture from the fluid prior to performing the step of flowing the fluid.

16. The method of claim 14 including the step of heating the fluid prior to performing the step of flowing the fluid.

17. The method of claim 14 , wherein the step of flowing a fluid includes flowing the fluid through an annular passage defined in part by the exterior surface of the blast nozzle.

18. The method of claim 14 , wherein the temperature of the fluid is above the dew point temperature of ambient conditions.

19. 1. A method for reducing ice build-up within and at an outlet of a blast nozzle having a flow of entrained cryogenic particles passing therethrough, the method comprising: a. flowing cryogenic particles entrained in a flow of transport gas through and out of the outlet of the blast nozzle for a period of time; b. while performing the flowing step, flowing a fluid adjacent to and along a portion of an exterior surface of the blast nozzle proximate to the outlet of the blast nozzle, the fluid having a temperature, water content and flow rate; c) controlling the temperature, sufficient moisture, and flow rate of the fluid to prevent impeding flow of cryogenic particles through and out of the outlet of the blast nozzle during the period of time; A method comprising:

Images