WO1990014927A1

WO1990014927A1 - Particle blast cleaning and treating of surfaces

Info

Publication number: WO1990014927A1
Application number: PCT/CA1990/000174
Authority: WO
Inventors: Somyong Visaisouk; Terry B. Mesher; Robert D. Rowe
Original assignee: Ixtal Blast Technology Corp.
Priority date: 1989-05-30
Filing date: 1990-05-29
Publication date: 1990-12-13
Also published as: AU5662290A; CA1321478C

Abstract

There is disclosed a method of particle blast cleaning and treating of surfaces including the step of preparing a supply of and metering a flow of particles, positively feeding the particle flow from the metering stage into a mixer or fluidizer, fluidizing the particle flow with a controlled, metered flow of fluid taken from a pressurized fluid source, conveying by fluid flow a particle-fluid stream from the fluidizing stage to a blast head, and controlling the fluid flow rates and the particle amount rates and the mass flow ratios of the two flows precisely and over fairly wide ranges to provide a particle blast cleaning and treating effect for a wide range of surfaces and objects. Apparatus in which this method is carried out is provided.

Description

PARTICLE BLAST CLEANING AND TREATING OF SURFACES

FIELD OF THE INVENTION

This invention relates to a method and apparatus for particle blast cleaning and treating of surfaces. BACKGROUND OF THE INVENTION

Sand blast technology has been well developed and widely used and acceptable cleaning results are able to be obtained with crude systems and low cost abrasives. However, many types of surfaces of materials are not able to be cleaned in this way because of damage to the surfaces and possible effect on the integrity of the objects being cleaned . Also, aside from environmental considerations nearby objects are often inconvenienced or damaged by over spray effects and clean-up is normally time consuming and costly. Over the last few years the use of other abrasive materials such as plastic chips and frozen liquids such as water (H20) ice, dry ice (C02) , and pellets of these mixed with certain chemical materials have been proposed for use in air blast technology to clean, wash, decontaminate or otherwise treat surfaces of a wide range of objects and materials.

The following are patents that show methods and apparatus using these types of materials:

British Patent No. 1,397,102 filed March 22, 1972 Published June 11, 1975

U.S. Patent No. 4,703,590 issued November 3, 1987 U.S. Patent No. 4,769,956 issued September 13, 1988 French Patent App. 80-03099 filed February 8, 1980 Publication No. 2,475,425 French Patent App. 80-24375 filed November 17, 1980 Publication No. 2,494,160 British Patent App. GB 2,171,624A Published

September 3, 1986 Japanese Public Disclosure No. 97533 dated August 2, 1975

U.S. Patent No. 3,676,963 issued July 18, 1972 United States patent 4,769,956 is an example of a sand blast machine employing two or more blast nozzles for propelling abrasive sand at interior and exterior exposed surfaces of a component to be treated. Control is exercised on the respective blast nozzles to vary the pressure from low to high levels to thereby vary the extent of abrasion on various surfaces interior and exterior of the workpiece being treated.

The remaining patents disclose various devices which employ ice particles in blast nozzles for treatment of work surfaces. All of these systems function on the basis of propelling the ice particles through the blast nozzle in the same manner that sand blasting is achieved such as, for example, in the aforementioned United States patent 4,769,956. No consideration is given to controlling air flows in transporting the ice particles to the blast nozzle in a manner to minimize degradation of the ice particles in the transport stream. Hence as is characteristic of previously known ice blasting equipment, the effectiveness of the ice particles in doing work on the surface to be treated is not commercially effective. It has been found, in accordance with this invention, that suitable control of mass flow rates, fluid flow rates and ratios thereof provide a commercially viable form of ice blast technology for treating and cleaning various surfaces. SUMMARY OF THE INVENTION

According to an aspect of the invention, a method of particle blast cleaning and treating of surfaces comprises: a) metering a flow of particles from a supply, b) positively feeding the particle flow from the metering stage into a fluidizer, c) fluidizing the metered particle flow with a controlled, metered flow of fluid taken from a pressurized fluid source, d) conveying by fluid flow a particle-fluid stream from the fluidizing stage to a blast head which directs the particle-fluid stream at a surface to be cleaned and treated, and e) controlling the fluid flow rates and the metered amount of particle rates and the mass flow ratios of the fluid and particle flows precisely and over fairly wide ranges to provide a particle blast cleaning and treating effect for a wide range of surfaces and objects. According to another aspect of the invention, a method of particle blast cleaning and treating of surfaces comprises: a) controlling particle size from a supply of particulate material by one or more of the steps of grinding, crushing or sizing the supply of particle material to provide a controlled particle size, b) metering a flow of particles in or from the grinding/ crushing/sizing stages, c) positive feeding of this particle flow into a fluidizer, d) fluidizing the particle flow with a metered flow of air from a compressed air source, e) conveying by air flow a fluidized particle-air stream from the fluidizing stage to a particle blast head which directs the particle-air stream at a surface to be cleaned or treated, and f) controlling the air flow rates and the particle amount rates and the mass flow ratios of the air and particle flows precisely and over fairly wide ranges to provide a particle blast cleaning and treating effect for a wide range of surfaces and objects.

According to another aspect of the invention, a method of particle blast cleaning and treating of surfaces comprises: a) forming a supply of ice by refrigeration, b) grinding or crushing this ice supply and classifying to a controlled particle size, c) metering by means of a positive displacement means a flow of ice particles from the grinding or crushing stage and feeding this flow into a fluidizer, d) fluidizing the ice particle flow with a metered flow of air from a compressed air supply source, e) conveying by air and accelerating such fluidized ice particle-air stream from the fluidizer to an ice particle blast head which directs the particle-air stream at a surface to be cleaned or treated, and f) controlling the air flow rates and the ice particle amount rates and the mass flow ratios of the air and particle flows precisely and over fairly wide ranges to provide an ice particle blast cleaning and treating effect for a wide range of surfaces and objects. According to another aspect of the invention, a method of particle blast cleaning and treating of surfaces comprises: a) metering a flow rate of particles of frozen liquid from a supply of said particles to provide a predetermined mass flow rate of said particles; b) positively feeding said metered flow of particles to means for fluidizing said particles to impart kinetic energy thereto; c) fluidizing said metered flow of particles by directing a controlled metered flow rate of one or more fluidizing and transporting fluid flows taken from a pressurized fluid source into said metered flow of particles to suspend said particles in said fluid flow and impart thereby kinetic energy to said particles in a fluidized state; d) conveying said particles in said fluidized state from said fluidizing means to a blast head by said metered flow rate of fluidizing and transporting fluid flows; e) blasting said particles through said blast head towards a work surface by accelerating said particles with a controlled metered flow rate of accelerating fluid flows introduced to said blast head from said pressurized fluid source to accelerate said particles during travel through said blast head; f) controlling flow rate of: i) said fluidizing and transporting flows which fluidize and deliver particles to said blast head; and ii) said accelerating flows which accelerate said particles whereby a ratio of group i) flow rate and group ii) flow rate is in the range of 0.1 to 1.5.

According to another aspect of the invention, particle blast cleaning and treating equipment comprises: a) means for metering a flow of particles from a supply, b) positive displacement means for receiving output of a flow of particles from said metering means for positively displacing a controlled, metered flow of particles, c) a fluidizer for receiving and fluidizing output of a positively displaced flow of particles from said positive displacement means, means for supplying a pressurized source of metered, controlled fluid flow to said fluidizer for fluidizing the particle flow and to transport such fluidized particle flow along a length of pipe to a blast head, d) a blast head connected to said length of pipe for directing such fluidized flow of particles towards a surface to be treated, and e) control means connected to the metering means, the positive displacement means, the fluidizer and pressurized fluid supply means to control the particle and pressurized fluid flow rates and the mass flow rates of the fluid and particle streams precisely and over fairly wide ranges to provide a particle blast cleaning and treating effect for a wide range of surfaces and objects. BRIEF DESCRIPTION OF DRAWING

Preferred embodiments of the invention are shown in the drawings wherein:

FIGURE 1 is a flow diagram of a particle blast cleaning and treating system according to an embodiment of the invention wherein a wide variety of material including frozen liquids may be used;

FIGURE 2 is a flow diagram of a particle blast system similar to that of Figure 1 but with acceleration input to the blast head;

FIGURE 3 is a flow diagram of a blast cleaning and treating system using a batch supply of particles with conditioning of media particles and air supply;

FIGURE 4 is a flow diagram of a complete system using a continuous production of a frozen liquid such as (H20) as the treating material and with integrated system control;

FIGURE 5 shows typical equipment for a batch media input system according to the flow diagram of Figure 1; FIGURE 6 is a cross-section of the fluidizer accelerator assembly as used in the apparatus shown in Figure 5;

FIGURE 7 is a cross-section of a single stage accelerator/blast head nozzle as used in the apparatus shown in Figure 2;

FIGURE 8 is a cross-section of a blast head consisting of a two stage accelerator, nozzle set as used in the apparatus shown in Figures 3 and 4;

FIGURE 9 is a broken sectional view of the system in a mobile unit;

FIGURE 10 is a diagrammatic view of the air supply system; and

FIGURE 11 is a diagrammatic view of the refrigeration and ice supply system. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION:

Figure 1 is a flow diagram of a blast system using a media including frozen liquids or non-frozen particulates where the input particles are fed either from a media fresh or recycle supply to a hopper 2 open to atmospheric pressure. From the hopper the material is fed by batch to surge tank 3. Compressed air (or other suitable gases) is taken from supply 1 and after passing through filter la, dryer lb having a condensate trap lc to condensate return line Id, and inlet valve le provides a fluidizing air supply via surge fluidizer valve 3a controlled by pressure meter 3b to the surge tank. The media materials then go to metering device 4 which would typically be a scroll or chambered positive displacement pump driven by variable speed motor 4a and controlled from computer station 7 to provide a precisely controlled input to fluidizer/ ccelerator 5. Device 5 also has pressurized air inputs via air flow control valve 5a controlled from computer station 7 and fluidizer air control valve 5b connected via pressure control 5c to pressure control 3b and computer 7 through flow indication and controller 7a to precisely control the rate, amounts and ratios of the air and treating particle streams. Output from the fluidizer/accelerator 5 is conveyed pneumatically to blast nozzle 6.

Figure 2 is a blast system similar to that of Figure l but where the metering device4 provides controlled media at a pressure consistent with higher pressure of the fluidizer 5. This is achieved by the pressurized air supply through the control valve 5a to the metering device 4. Fluidizer 8 is supplied with pressurized air through control valve 8a assist in pneumatically transporting the media from hopper 2 to metering device 4. Fluidizer 5 provides only enough energy to transport the particle mix through the hose without undue damage of the media particles such as ice, plastic chips, nut shells, glass beads, sand, gritty materials, etc.

Acceleration energy is added to the blast head 6 at 6a via additional controlled air through valve 9. This air input is taken from the air supply 1 via air flow control valve 9 controlled by flow indicator and controller 9a connected to computer 7. If desired additives such as cleaning and chemical agents may be introduced into the system by adding to the particle media feed as shown. The controller 7 provides control through valve controllers 5c, 7a and 9a which control respectively valves 5b, 5a and 9. The computer controlled valves used in the various embodiments of this invention, and in particular with the valves 5a, 5b and 9 of Figure 2 are of variable throat design to provide from the fully closed to the fully opened position a range of flow rates for pressurized fluid through the respective valve. The controller 7 , by way of the electronic valve controllers 5c, 7a and 9a, controls the degree to which the valves are open to thereby control the respective air flows. The controller 7 determines the degree of valve opening by transmitting a suitable signal to each controller which effects a positioning of the valve in the desired open position to produce a corresponding flow rate. Such types of computer controlled valves are well known and are readily available from a variety of suppliers. Controller 7 is programmed to control the respective flow rates of pressurized fluid to the metering device for the fluidizer 5 and the blast head 6. By appropriate control of flow rates of pressurized fluid to these devices, the optimum work efficiency of the particles employed in the media can be achieved to provide the desired degree of surface cleaning and/or treatment. This is particularly advantageous when the particles employed for the media are derived from a supply of ice. Ice particles and other types of particles, such as plastic chips and glass beads, are sensitive to break down or deterioration during the fluidization and transport stage. This significantly alters the effectiveness of the particles as they pass through the blast head to perform work on the surface to be treated. It is therefore desirable to control the flow rates of pressurized fluid which may be used in the metering device and particularly in the fluidizing device to effect adequate fluidization of the particles in the pressurized fluid stream for purposes of transport of the particles to the blast head. It has been determined that the ratio of flow rates of pressurized fluid to the fluidizer and other upstream equipment, such as the metering device and the like, should be controlled in a manner so that the ratio of the flow rate of pressurized fluid to these upstream devices relative to the flow rate of pressurized fluid to the blast head is in the range of 0.1 to 1.5. As applied to ice particles, it has been determined that ratios of flow rates in this range provide for fluidization and transport of the ice particles in a manner which minimizes degradation of the ice particles upon delivery to the blast head. The additional pressurized fluid then required at the blast head is adequate to sufficiently accelerate the particles, particularly ice particles, to a velocity which develops the necessary pressure at the work face to effect the desired degree of surface treatment and/or cleaning. It is appreciated that the longer the pipe required to transport the fluidized particles from the fluidizer 5 to the blast head 6 usually results in the ratio being in the range of 1 to perhaps up to 1.5. For standard lengths of piping of the fluidized particles to the blast head, that is in the range of 20 to 80 feet, it has been found that a ratio of the flow rates in the range of 0.1 to 0.5 is useful and ensures that the ice particles have maintained their size distribution before delivery to the blast head.

Figure 3 is a more detailed flow diagram of the system with air as the propellant and ice as the treating media. Air from a compressed air source 1 is passed through after-cooler 17 to reservoir 18 and from there through air filter 19a to dryer 20. The after-cooler, reservoir and dryer are connected through traps 21a, 21b, and 21c to condensate return line 22. Air under pressure from the reservoir and dryer is fed through air filter 19b to air flow control valves 23, 24, and 25 with the three flow rates being measured and controlled by flow meters 23a, 24a, and 25a. Ice from a batch supply source 2a is fed into hopper 2 whose output feed is controlled by the rate at which ice crusher/sizer 29 processes ice as determined by variable speed motor drive 47 and controlled by transport air supply from the compressed air sources via control valves 2c and 2d.

Crusher/sizer 29 as connected to variable speed motor drive 47 and cooled by the refrigerant supply 42, crushes and sizes the ice from the hopper to a controlled working size after which it is fed into surge tank 30. Pressurized air input via control valve 48 acts with control valve 49 as an automatic purge system sending reject fines and purge air to output line 50. Ice is fed from the surge tank into metering device 31 which would typically be a chambered or scroll positive displacement pump connected to a variable speed drive motor 52 to positively feed a measured supply of ice particles into fluidizer 32. Control valves 48' and 49', as connected to the metering device, can be used to remove from the metering device 31 any unwanted particle sizes by use of differing settling velocities and/or screen sizes in the metering device to effect a classification of particle size. The ice particles are combined and fluidized with a pressurized air flow from control valve 23. Sizer 29 may be a multiple stage unit as required and can provide thereby further control on particle size. Line 33 carries the fluidized air and treating ice particles into blast head 34 where this flow has injected into it at entry points 34a and 34b two high velocity air streams from control valves 24 and 25 via lines 36 and 37 resulting in a treating particle blast at a work piece for cleaning purposes. With reference to the system of Figure 3, pressurized fluid is provided to the fluidizer with multiple introduction of pressurized fluid to the blast head. As previously explained the ratios of the flows of pressurized fluid to the fluidizer in any upstream components relative to the flow rates to the blast head are desirably within the range of 0.1 to 1.5. Within this ratio, it has been determined that the flow rate of pressurized fluid to the blast head, particularly when introduced at multiple points as shown in Figure 3, provides for an enhanced acceleration of the particles whereby degradation of the particles in terms of sizing is minimized. The multi-stage boosting of the particle velocity provides for a somewhat more gradual acceleration of the particles and hence less particle disintegration before striking the work surface. Thereby the desired particle size distribution is maintained to ensure optimum performance at the work surface.

It has been determined that the preferred range of particle sizes, as determined at the ice crusher/sizer 29, varies from approximately 1 mm to 5 mm. It is especially preferred with ice particles that the majority of the particles be in the range of 3 mm to 5 mm in size. It is appreciated that the sizing of the particles is established by standard screening techniques, where particles falling through a certain screen mesh size are being retained whereby the screen mesh size determines the particle average size. By maintaining the flow rates in the ratio prescribed, the desired distribution of particle sizes of the media in the fluidizer is essentially maintained up to delivery of particles to the blast head. It is appreciated, however, that in the transport of the particles particularly the more fragile ice particles, there is some breakage of the particles to produce fines in the particle/air stream. However, this is minimized so as to achieve optimum performance at the work face. A more elaborate computerized control of the pressurized fluid flows will be discussed with respect to the embodiment of Figure 4.

Figure 4 is similar to Figure 3 but shows a complete system including ice making apparatus and a computerized control system. Water is fed to precooler/deaerator 26 and then to ice maker 27. If desired chemicals may be added to the feed water via line 28. Other media may be added by similar process systems for multiphase treating flows. Precooler 26 is operated through valve 40 controlled by automatic temperature control 41 to a refrigerant supply 42 having a temperature control 43. The rate of ice making in ice maker 27 is controlled by variable speed drive 44 which is responsive to demand of metering rates set by ice crusher/sizer 29 and/or metering device 31, where metering device 31 is itself the master control point for ice particle flows through the system. Where there is more than one ice maker 27, the rate of ice making may be controlled by sequencing of the multiple ice makers to supply the desired rate of ice to be treated by crusher 29. Coolant demand is through valve 45 controlled by automatic temperature control 46 to the refrigerant supply 42. The surge tank 30 when required is also cooled by the refrigerant source and has its level monitored by the level control 51 which controls variable speed drives 44 and 47 to maintain the appropriate ice supply levels to supply metering device 31. Valves 48 and 49 serve to purge rejects from the surge tank and valves 48' and 49* purge unwanted fines which are removed by a classification step carried out in the metering device 31. As in Figure 3 ice from the surge tank is fed to metering device 31 and to fluidizer 32 which provides an air/ice supply via line 33 to blast head 34.

As with the embodiment of Figure 3, a master control system 60 is provided for the ice blast apparatus of Figure 4. The master controller 60 is designed to control the speeds for the variable speed drive of the ice maker 27, the speed of the ice crusher 29 and the speed of the metering device 31 through respective controllers 44, 47, 52. The central control system also monitors the level in the surge tank 30 through level control 51. As well the metering device 31 is controlled by master controller 60 through controller 52. The master controller 60 is linked to these respective controllers through lines A, B, C and D. The master controller 60 is also linked to sub-control units 61a, 61b and 62. Sub-controller 61a is connected to sensor 34c in the blast head, whereas sub-controller 62 is connected to the sensor 34d in the blast head. Also, sub-controller 62 is coupled to valves 48 and 49 to control fluid flow through valve 48 into the surge tank and return of rejected fines through valve 49. Sub- controller 61b is also linked to sub-controller 62. Sensors 34c and 34d in the blast head sense the flow rates of fluid flow through the blast head and provide feedback to the sub-controllers. The sub-controllers provide feedback to the master controller 60 which, in turn, controls valves 24 and 25 which supply pressurized fluid to the multi-stage blast head at 34a and 34b. The master controller also controls the supply of pressurized fluid to the fluidizer 32 through valve 23. As already noted for shorter line lengths of 40 to 80 feet, the sub- controller 62 controls valves 48, 49 and 49'. In accordance with the master controller's program, air flows to the fluidizer and upstream components relative to the air flows to the blast head are controlled to provide the already-noted ratio of approximately 0.1 to 1.5. With this sophisticated degree of computerized control of the various component air flows, not only can the ratio of air flows be finely tuned, but with feedback from the sensors 34c and 34d, a constant monitoring of the air flows is provided to ensure that the ratio of flows is always within the prescribed range. As already noted with ice particles, it is particularly desirable to provide the ratio in the range of 0.1 to 0.5.

In essence the overall system is arranged to prepare treating material in suitable form and to monitor and control the mass flows of the air and particle flows and the ratios of these as previously defined in an extremely precise manner and over fairly wide range such that a wide spectrum of material surfaces can be treated without damage to these surfaces and with best overall effect. The system provides a positive, metered controlled flow of both air and media with propellant energy added at appropriate points resulting in less energy loss and media damage.

Figure 5 shows the media feed equipment for a batch pressure pot blast system as shown in Figure 1. The particle media is fed into open hopper 65 at atmospheric pressure and then to pressure surge vessel 66. At the inlet 66' to the surge vessel, a pressure sealing valve is provided to isolate pressure in the surge vessel from the open hopper during introduction of material to the vessel as well as after material is introduced to the vessel. A compressed air input is taken from a supply through air flow control valves 67 which is item 7a of Figure 1 and 68 which forms items 5a and 5b of Figure 1 into fluidizer 69. The feed passes to metering pump 70 which is item 4 of Figure 1 connected to a variable speed drive which is not shown in Figure 5, but which is Item 4a of Figure 1 and to fluidizer/accelerator 71 having compressed air inputs 71a and 71b. Output from the fluidizer/accelerator is piped to the blast head.

Figure 6 shows the fluidizer/accelerator assembly as shown in Figure 5 (Item 71) . Controlled, metered particulate blast media from the metering pump enters at 72 and is accelerated by a controlled, metered air input from air line 71a to jet nozzle 73. Fluidizing air

(metered and controlled) from air line 71b is injected at 74 and further fluidizes and accelerates the air/particle media stream with the output being piped to the blast head 6 of Figure 1.

Figure 7 shows a single stage fluidizer/accelerator of a type that could be used as the blast head 6 of Figure 2 with the non or partially fluidized media stream (metered and controlled) entering at 75 and a metered, controlled air stream injected at 76 which is location 6a of Figure 2. This flow passes into annular distributing chamber 77 through a gap formed by pressure 0-ring seal 78 into the venturi shaped interior to form a fluidizing, accelerating stream. The output provides a fluidized and accelerated air stream, controlled and metered to a required degree for transport, conveying and work energy at the blast head. Figure 8 is a two stage accelerator/fluidizer similar to that of Figure 7 but for a more precise control of conditions. The blast head has a second air input at 76a passing into the interior via annular distributing chamber 77a and the gap formed by 0-ring seal 78a. This device is used as the blast head shown in , Figures 3 and 4 as Items 34, 34a and 34b.

A mobile version of the system is shown in Figure 9 with the air supply portion in Figure 10 and the refrigeration and ice supply portion shown in Figure 11. Power plant 80 drives compressor 81 drawing ambient air from air intake 82 and sending it via line 83 to air cooler 84. The air is then passed through condensate trap 84a to air reservoir 85 having condensate trap 86, through air filter 87 and dryer 88 and through air filter 89 to control valves 90. Alternatively, some or all of the drying steps may be performed by placing the components of the drying equipment upstream of the air compressor.

The power plant also drives refrigeration plant 91 to provide refrigerant for ice making and cooling the ice process components. Water from tanks 92 passes through deaerator 93, and precooler 94 to ice maker and εizer 95. The ice is crushed in crusher 96 and passed to metering device 97 and fluidizer 98 which also has an air input from control valves 90 to direct a fluidized ice-air stream via line 99 to the blast heads. As shown, two compressed air flows are taken from valves 90 via lines 100a and 100b to supply the pressurized air from the multi-stage blast head of Figure 8. Other elements shown are refrigerant cooler 101, engine cooler 102, fuel tank 103, control room 104 and control panel 105 (Figure 10). As previously noted, the size and distribution of ice particles for the media can greatly affect the efficiency of the ice blast in doing work on the desired surface. The desired range of particle sizes is from approximately 1 mm to 5 mm. It has been found that ice particles outside of this range are either too small and are not effective or too large and waste too much energy. By use of an ice crushing and sizing device of the type discussed, it has been found that the size of ice particles in the range of 1 mm to 5 mm can be attained. Preferably the distribution of the particles in this range are in the majority of approximately 3 mm to 5 mm in size. By use of appropriate sizing and/or screening devices, this distribution of particle sizing can be achieved. By control of the flow rates of pressurized fluid to the fluidizer to the blast head, this particle size distribution can be maintained up to the blast head at which point minimal deterioration of the particles is achieved so that the particles, as they impact on the work surface, are still within the desired size range. Preferably the flow rate of pressurized air for delivering the ice particles to the blast head is sufficient to provide particle velocities in the transport lines in the range of 10 to 20 feet/sec. The flow rate of pressurized air to the blast head is sufficient to provide particle velocities at the exit of the blast head in the range of 400 ft/sec. Although preferred embodiments of the invention are described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

1. A method of particle blast cleaning or treating of surfaces comprising: a) metering a flow of particles fro'm a supply, b) positively feeding the particle flow from the metering stage into a fluidizer, c) fluidizing the metered particle flow with a controlled, metered flow of fluid taken from a pressurized fluid source, d) conveying by fluid flow a particle-fluid stream from the fluidizing stage to a blast head which directs the particle-fluid stream at a surface to be cleaned or treated, and e) controlling the fluid flow rates and the metered amount of particle rates and the mass flow ratios of the fluid and particle flows precisely and over fairly wide ranges to provide a particle blast cleaning or treating effect for a wide range of surfaces and objects.

2. A method of particle blast cleaning or treating of surfaces as in Claim 1 further comprising piping at least one high pressure controlled fluid stream from a pressurized fluid source to the blast head to interact with the conveyed fluidized particle-fluid stream to provide a particle blast for surface cleaning or treating purposes.

3. A method of particle blast cleaning or treating of surfaces as in Claim 1 or in Claim 2 wherein the particle material is in a frozen state.

4. A method of particle blast cleaning or treating of surfaces as in Claim 1 or Claim 2 wherein said supply particle material is selected from the group consisting of plastic chips, glass beads, nut shells, sand and other similar gritty materials.

5. A method of particle blast cleaning or treating of surfaces comprising: a) controlling particle size from a supply of particulate material by one or more of thee steps of grinding, crushing or sizing the supply of particle material to provide a controlled particle size, b) metering a flow of particles in or from the grinding/ crushing/sizing stages, c) positive feeding of this particle flow into a fluidizer, d) fluidizing the particle flow with a metered flow of air from a compressed air source, e) conveying by air flow a fluidized particle-air stream from the fluidizing stage to a particle blast head which directs the particle-air stream at a surface to be cleaned or treated, and f) controlling the air flow rates and the particle amount rates and the mass flow ratios of the air and particle flows precisely and over fairly wide ranges to provide a particle blast cleaning and treating effect for a wide range of surfaces and objects.

6. A method of particle blast cleaning or treating of surfaces as in claim 5 further comprising metering at least one pressurized air stream from a compressed air source through a flow control valve to the blast head to interact with the particle-air stream to provide particle blast for surface cleaning or treating purposes.

7. A method of particle blast cleaning or treating of surfaces as in claim 5 or claim 6 wherein the treating material is a frozen liquid.

8. A method of particle blast cleaning or treating of surfaces as in claim 5 or claim 6 wherein the supply of particle material is selected from the group consisting of plastic chips, glass beads, nut shells, sand and other similar gritty materials.

9. A method of particle blast cleaning or treating of surfaces as in claim 5 wherein particle size is controlled by said one or more steps to provide a controlled particle size having a distribution of particles sizes in the range of 1 mm to 5mm.

10. A method of particle blast cleaning or treating of surfaces as in claim 9 wherein a majority of said particles are in the size range of 3 mm to 5 mm.

11. A method of particle blast cleaning or treating of surfaces comprising: a) forming a supply of ice by refrigeration, b) grinding or crushing this ice supply and classifying to a controlled particle size, c) metering by means of a positive displacement means a flow of ice particles from the grinding or crushing stage and feeding this flow into a fluidizer, d) fluidizing the ice particle flow with a metered flow of air from a compressed air supply source, e) conveying by air and accelerating such fluidized ice particle-air stream from the fluidizer to an ice particle blast head which directs the particle-air stream at a surface to be cleaned or treated, and f) controlling the air flow rates and the ice particle amount rates and the mass flow ratios of the air and particle flows precisely and over fairly wide ranges to provide an ice particle blast cleaning and treating effect for a wide range of surfaces and objects.

12. A method of particle blast cleaning or treating of surfaces as in claim 11 further comprising piping at least one metered and controlled air stream from a compressed air supply source to the blast head input line to interact with and accelerate the ice particle-air stream.

13. A method of particle blast cleaning or treating of surfaces as in claim 11 further comprising metering said supply of ice to said grinding or crushing step.

14. A method of particle blast cleaning or treating of surfaces comprising: a) metering a flow rate of particles of frozen liquid from a supply of said particles to provide a predetermined mass flow rate of said particles; b) positively feeding said metered flow of particles to means for fluidizing said particles to impart kinetic energy thereto; c) fluidizing said metered flow of particles by directing a controlled metered flow rate of one or more fluidizing and transporting fluid flows taken from a pressurized fluid source into said metered flow of particles to suspend said particles in said fluid flow and impart thereby kinetic energy to said particles in a fluidized state; d) conveying said particles in said fluidized state from said fluidizing means to a blast head by said metered flow rate of fluidizing and transporting fluid flows; e) blasting said particles through said blast head towards a work surface by accelerating said particles with a controlled metered flow rate of accelerating fluid flows introduced to said blast head from said pressurized fluid source to accelerate said particles during travel through said blast head; f) controlling flow rate of: i) said fluidizing and transporting flows which fluidize and deliver particles to said blast head; and ii) said accelerating flows which accelerate said particles whereby a ratio of group i) flow rate and group ii) flow rate is in the range of 0.1 to 1.5.

15. A method of claim 14 wherein step (b) feeding of said material flow of particles includes pressurizing said flow of particles with fluid from said pressurized fluid source.

16. A method of claim 14 wherein step (e) introducing said accelerating flows to at least two points of introduction for said blast head to enhance acceleration of said particles and to reduce particle disintegration during travel through said blast head.

17. A method of claim 14 wherein said ratio of flow rates is in the range of 0.1 to 0.5.

18. A method of claim 14 wherein said supply of ice particles is crushed ice, separating said crushed ice to provide said ice particles of a size range from 1mm to 5mm.

19. A method of claim 17 wherein said group i) flow rates provide a gentle conveyance of said crush sensitive ice particles to said blast head whereby said fluidized state of said ice particles is maintained during conveyance to said blast head.

20. Particle blast cleaning or treating equipment comprising: a) means for metering a flow of particles from a supply, b) positive displacement means for receiving output of a flow particle from said metering means for positively displacing a controlled, metered flow of particles, c) a fluidizer for receiving and fluidizing output of a positively displaced flow of particles from said positive displacement means, means for supplying a pressurized source of metered, controlled fluid flow to said fluidizer for fluidizing the particle flow and to transport such fluidized particle flow along a length of pipe to a blast head, d) a blast head connected to said length of pipe for directing such fluidized flow of particles towards a surface to be treated, and e) control means connected to the metering means, the positive displacement means, the fluidizer and pressurized fluid supply means to said fluidizer to control the particle and pressurized fluid flow rates and the mass flow rates of the fluid and particle streams precisely and over fairly wide ranges to provide a particle blast cleaning and treating effect for a wide range of surfaces and objects.

21. Particle blast cleaning or treating equipment as in claim 20 further comprising means for supplying pressurized fluid to said blast head for providing an accelerating effect to the fluid-particle stream transported in said length of pipe to said blast head.

22. Particle blast cleaning or treating equipment as in claim 20 further comprising means for sizing a supply of particles to provide a controlled particle size.

23. Particle blast cleaning or treating equipment as in claim 20 wherein a supply of particles is in the form of ice, means for crushing/grinding and/or sizing particles of ice to provide a controlled particle size having a distribution of particle sizes in the range of 1 mm to 5 mm.

24. Particle blast cleaning or treating equipment as in claim 21 wherein said control means controls separately said pressurized fluid supply means for said fluidizer and said pressurized fluid supply means for said blast head, said control means being adapted to control flow rates of: i) said pressurized fluid flow of said supply means for said fluidizer; and ii) said pressurized fluid flow of said supply means for said blast head to provide a ratio of group (i) flow rate and group (ii) flow rate in the range of 0.1 to 1.5.

25. Particle blast cleaning or treating equipment as in claim 21 wherein said means controls group (i) and group

(ii) flow rates to provide a ratio in the range of 0.1 to 0.5.