Spiral jet mill with multiple product injector nozzles and method of grinding a granular product

Description

1 / 16 Spiral jet mill with multiple product injection nozzles and grinding method for a granular product. BACKGROUND

[001] Spiral jet mills are used to grind granular materials, for example, the fragmentation of powdered materials, to reduce the particle sizes of the granular material. A spiral jet mill includes a generally planar circular grinding chamber, which is surrounded by a manifold with a number of grinding steam injectors that inject grinding steam into the grinding chamber. Typically, each of the grinding steam injectors is oriented at the same angle relative to the radial, i.e., tangentially to the centerline, so as to promote a relatively uniform flow in both clockwise and counterclockwise directions around the grinding chamber. A cover covers the upper end of the grinding chamber and includes a single product injector nozzle, which is used to inject mixed inlet steam and the granular product into the grinding chamber.The product injector nozzle is typically oriented tangentially to the centerline and at an acute angle to the horizontal so as to inject product vapor and introduce steam along the same clockwise or counterclockwise direction as the grinding steam. As the granular particles rotate around the outer periphery of the grinding chamber, impacts with the grinding steam eventually fragment the granular particles. Smaller ground particles migrate to the center of the grinding chamber, where an exhaust outlet allows the ground particles to be ejected from the grinding chamber with the exhaust steam. An example of a conventional spiral jet mill can be seen in US Patent No. 7,150,421.

[002] Spiral jet mills that use steam as the Petition 870250085933, dated 09 / 23 / 2025, p. 7 / 35 2 / 16 Inlet gas and / or grinding gas can use a large amount of steam, and thus energy, to grind a given quantity of granular product. Therefore, it would be desirable to improve the efficiency of the spiral jet mill to reduce input costs and / or have a smaller carbon footprint to be more environmentally friendly. SUMMARY OF THE INVENTION

[003] In one aspect of the invention, a spiral jet mill includes a collector surrounding and at least partially defining a grinding chamber, a grinding gas injector orifice extending through the collector to the grinding chamber to inject grinding material into the grinding chamber, a cover over the collector, the cover at least partially defining the grinding chamber, and an exhaust orifice to exhaust the ground product from the grinding chamber. A first product injector nozzle is directed to the grinding chamber and configured to mix and inject a first inlet gas vapor and a granular product into the grinding chamber, and a second product injector nozzle is directed to the grinding chamber to mix and inject a second inlet gas vapor and the granular product into the grinding chamber.

[004] Any one or more of the product injection nozzles may extend through the cover. For example, the first product injection nozzle may extend through the cover and the second injection nozzle may extend through another part of the spiral jet mill, such as through a lower wall of the grinding chamber and / or through the collector. Preferably, at least one of the first and second injection nozzles extends through the cover. Optional additional product injection nozzles may similarly extend through the cover or through another part of the spiral jet mill provided they are configured to inject a stream of product into the grinding chamber to be ground by the grinding material. Petition 870250085933, dated 09 / 23 / 2025, page 8 / 35 3 / 16 in the same.

[005] In some optional configurations, the spiral jet mill may include more than two product injection nozzles. For example, the spiral jet mill may optionally include a third product injection nozzle extending through the cover to mix and inject a third stream of steam and the granular product into the grinding chamber. In other optional configurations, the spiral jet mill may include four, five, six, seven, eight, or really any number of product injection nozzles that can fit into the available physical space.

[006] The product injector nozzles can be aligned in any suitable manner to inject product into the grinding chamber to allow for product grinding. Some optional configurations are described later here. For example, any or all of the product injector nozzles can be aligned tangentially and offset from a centerline of the grinding chamber. Any or more of the product injector nozzles can be aligned to inject the respective flows in the same clockwise or counterclockwise direction around the grinding chamber. The first and second product injector nozzles can be arranged on opposite sides of the centerline, for example, at the same diameter across the centerline.

[007] The product injector nozzles may be aligned in parallel sets, as in parallel pairs. For example, the first product injector nozzle may be aligned parallel to the second product injector nozzle, for example, in parallel vertical planes that are equidistant from and on opposite sides of the centerline of the grinding chamber. When there are four, six, or other multiples of pairs of product injector nozzles, two or more pairs may be aligned parallel to each other, for example, in parallel vertical planes. Petition 870250085933, dated 09 / 23 / 2025, page 9 / 35 4 / 16 of them, with each pair being angularly offset around the circumference of the grinding chamber from one or more of the other pairs.

[008] Any one or more of the product injection nozzles may have an injection end disposed within the grinding chamber, so as to inject the product directly into the grinding chamber. In some arrangements, the injection end of two or more product injection nozzles may be located at the same radial distance from the centerline.

[009] The manifold may take any form suitable for injecting the grinding material into the grinding chamber. For example, the manifold may include a plurality of grinding gas injector orifices extending through the manifold into the grinding chamber to inject the grinding material into the grinding chamber. In some configurations, the manifold may include between one and thirty grinding gas injector orifices, although any number capable of physically fitting into the manifold could be used. Preferably, some or all of the grinding gas injector orifices are aligned tangentially rather than radially through the centerline so as to cause gases and product within the grinding chamber to rotate in a single clockwise or counterclockwise direction.In some arrangements, all grinding gas injection orifices and product injection nozzles may be tangentially aligned in the same general clockwise or counterclockwise orientation to promote uniform circumferential gas and product flow within the grinding chamber. However, in other arrangements, one or more grinding gas injection orifices and product injection nozzles may be oriented in other orientations, for example, in opposite clockwise / counterclockwise directions, radially, or tangentially to circles of different radii or other arcs, to increase turbulence and / or promote different flow patterns within the grinding chamber. Petition 870250085933, dated 09 / 23 / 2025, page 10 / 35 5 / 16

[0010] Product injector nozzles may assume any suitable form for injecting a stream of a mixture of the product to be ground and a pressurized gas. In some arrangements, any one or more of the product injector nozzles may have a primary inlet orifice for the gas and product and one or more secondary inlet orifices to add one or more dosing substances or other materials to the stream. In one example, the primary inlet orifice and the secondary inlet orifice may converge and / or otherwise connect to a mixing chamber where the product from the secondary inlet orifice(s) mixes with the vapor of the product and pressurized inlet gas(es). A passage may extend from the mixing chamber to the grinding chamber to inject the mixed stream into the grinding chamber. However, the inclusion of the secondary inlet orifice is not required and may be omitted, or any number of secondary inlet orifices may be provided.

[0011] In another aspect of the invention, a method is provided for grinding a granular product using a steam jet mill as described herein. The method includes the steps of simultaneously injecting the first stream of an inlet gas and granular product mixture into the grinding chamber through the first product injector nozzle and injecting a second stream of an inlet gas and granular product mixture into the grinding chamber through the second product injector nozzle. The grinding material is injected into the grinding chamber through the grinding gas injector orifice so as to impact and grind the granular product of the first and second streams into smaller particle sizes.

[0012] The spiral jet mill can be operated with essentially any type of pressurized gas, such as steam, air, nitrogen, or similar gases, and combinations thereof. Preferably, the pressurized gas(es) is / are inert and / or flammable, although some Petition 870250085933, dated 09 / 23 / 2025, page 11 / 35 6 / 16 but applications may use flammable or otherwise reactive gases. In some arrangements, the inlet gas and / or grinding material may be or include pressurized gas, for example, steam, air and / or nitrogen.

[0013] The spiral jet mill is considered to be usable for grinding and reducing the particle size(s) of granular material of almost any substance. For example, the granular product may be and / or include TiO2 (titanium dioxide) pigment particles having particle sizes between approximately 0.1 µm and 5 cm. However, other types of granular product and / or particle sizes may be ground in the spiral jet mill.

[0014] The ratio of pressurized gases to granular material can be selected to improve grinding capacity and / or energy efficiency. In some example configurations, the first and second flows comprise an inlet gas ratio (e.g., inlet steam) to granular material ratio (e.g., TiO2 pigment particles) that may be less than about 2:1, more preferably between about 1.1:1 and about 1.9:1, even more preferably about 1.5:1. For example, in some arrangements, the inlet gas to granular material ratio in the flows may be about 1.54:1; however, other ratios are also considered.

[0015] In some configurations and methods, the spiral jet mill and / or method of the present invention can provide a more efficient system for reducing the particle sizes of granular material compared to known spiral jet mills having only a single product injection nozzle. Other advantages, uses and / or features will become apparent upon review of the following detailed description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS Petition 870250085933, dated 09 / 23 / 2025, page 12 / 35 7 / 16

[0016] Figure 1 is a side view of a spiral jet mill according to certain aspects of the present invention with the cover shown in cross section; Figure 2 is a top plan of the spiral jet mill showing the cover; and Figure 3 is a detailed cross-sectional view of the product injector nozzle of the cover along lines AB of Figure 2. DETAILED DESCRIPTION

[0017] The following description aims to describe what is shown in the drawings and / or in various embodiments considered and / or related to what is shown in the drawings. Any of the features shown and / or described in relation to one embodiment may be combined with any one or more features shown and / or described in relation to another embodiment. Any dimensions shown in the drawings are exemplary only and are not intended to limit the scope of the invention.

[0018] Returning now to the drawings, Figures 1-3 illustrate an exemplary spiral jet mill cover 10 according to certain non-limiting aspects of the invention. The spiral jet mill 10 includes a mill body 12 and a cover 14. The mill body 12 includes a collector 16 that surrounds and defines an outer periphery of a grinding chamber 18. In this example, the collector 16 generally has a planar circular shape defining a circular grinding chamber 18 with a central line 19 which in this example is defined by a vertical central axis, and having a height defined by the height of the collector along the vertical central axis and a diameter extending through the vertical central axis and through the grinding chamber. Other shapes of the grinding body 12 and collector 16 are possible, and the shapes need not be limited to circular shapes. Petition 870250085933, dated 09 / 23 / 2025, page 13 / 35 8 / 16

[0019] At least one, and in this example twelve, grinding gas injection orifices 20 extend through the manifold 16 to allow the injection of grinding material, such as steam or other compressed gas, into the grinding chamber 18. The manifold 16 may have more than twelve grinding gas injection orifices 20 or may have fewer than twelve gas injection orifices. In another example, the manifold 16 has six grinding gas injection orifices 20. Preferably, the grinding gas injection orifices 20 are angularly spaced uniformly around the periphery of the manifold 16. The grinding gas injection orifices 20 are oriented tangentially to the central axis to promote circumferential gas flow and particulate matter within the grinding chamber 18 in a single direction.In this example, each of the twelve grinding gas injection orifices 20 is oriented at an angle between about 10° and about 20° (for example, around 15°) from the radial direction in order to promote gas flow in a counterclockwise direction when viewed from above; however, other orientations, such as other angles, different angles between the various grinding gas injection orifices 20, and / or orientation to promote flow in the clockwise and / or counterclockwise direction may be implemented. The mill body 12 may include other features, such as other grinding gas inlets, grinding gas outlets, a bottom wall, and / or additional features in any manner suitable for directing and / or exhausting the grinding gas into the grinding chamber 18.

[0020] The cover 14 is arranged on the upper part of the mill body 12 so as to cover and enclose the grinding chamber 18. In this way, the cover 14 defines at least partially an upper surface of the grinding chamber 18. The cover 14 is preferably removablely coupled to the mill body 12 in an operating position, as shown in Figure 1, for example, with screws. Petition 870250085933, dated 09 / 23 / 2025, p. 14 / 35 9 / 16 sos 22 or other types of fasteners. Other mechanisms for fixing the cover 14 to the mill body 12 so as to enclose the grinding chamber 18 are also possible. The cover 14, in this example, has the shape of a generally flat disc with stepped external peripheral projections that are complementary with stepped internal peripheral projections on the upper surface of the mill body 12. The cover 14 may have other shapes, such as a dome, a cylinder with a closed end, or another shape configured to promote the flow of gases and product within the grinding chamber 18 in a desired manner.

[0021] Unlike conventional spiral grinding mills, the spiral jet mill 10 includes at least two product injector nozzles 24, such as a first product injector nozzle 24a and a second product injector nozzle 24b, configured to inject compressed gas streams, such as steam, and a granular product, such as titanium dioxide (TiO2) pigment particles, into the grinding chamber 18. In this example, the first and second product injector nozzles 24 are carried by and extend through the cover 14. However, in other examples, one or more of the product injector nozzles 24 may extend through other parts of the spiral jet mill 10, such as through a grinding chamber floor 18 and / or through a grinding chamber side wall, such as through the collector 16.As best seen in Figure 3, each product injector nozzle 24 extends downwards at an acute angle with respect to the horizontal plane of the cover 14 (as seen in reference to the drawings) into the grinding chamber 18.

[0022] As seen best in Figure 2, each product injector nozzle 24 is oriented tangentially to the central axis of the grinding chamber 18 at an angle from the radius. Each product injector nozzle 24 thus oriented tangentially and offset from the central axis of the chamber Petition 870250085933, dated 09 / 23 / 2025, p. 15 / 35 10 / 16 grinding chamber 18 and aligned to inject the first and second flows in the same clockwise or counterclockwise direction around the grinding chamber. Preferably, each product injector nozzle 24 is offset the same distance from the central axis, although the product injector nozzles 24 may be offset at different distances and / or oriented at different angles and / or in different orientations with respect to the central axis. In other arrangements, one or more of the product injector nozzles 24 may be oriented in different orientations, such as radially, in different directions, clockwise or counterclockwise, and at different offsets or without offset from the central axis, to promote fluid flow in different patterns and / or particle collision within the grinding chamber 18.

[0023] The first and second product injector nozzles 24a and 24b are arranged and oriented to form a pair of parallel product injector nozzles 24 aligned along parallel planes on opposite sides of the central vertical axis, each pointing in the opposite direction, and offset on opposite sides of the central vertical axis so as to inject the respective streams of granular product and compressed gas in a counterclockwise direction similar to the grinding gas injector orifices 20.

[0024] The spiral jet mill 10 may include more than two product injection nozzles 24. For example, there may be three, four, or almost any number of product injection nozzles 4 with the practical limitation being the physical space available to fit the product injection nozzles through the cover 14 and / or other locations through the mill body 12.

[0025] As best seen in Figure 3, each product injector nozzle 24 may include a primary inlet orifice 26 for gas and product and a secondary inlet orifice 28 for a dosing substance. The secondary inlet orifice 28 may be in the form of a Petition 870250085933, dated 09 / 23 / 2025, p. 16 / 35 The 11 / 16 smaller nozzle can be used to dose other liquids, such as silicone oil, trimethylpropane, or others, to provide a so-called organic coating of the particles that occurs during grinding in the mill. The primary inlet orifice 26 and the secondary inlet orifice 28 converge in a mixing chamber 30 where the compressed gas vapor and granular product mix with any dosing substance that is desired to mix in the vapor. However, the secondary inlet orifice 28 can be omitted and / or other orifices can be included. A passage 32 extending from the mixing chamber 30 to the grinding chamber 18 directs and injects the vapor directly into the grinding chamber 18 through an injection end 34 of the product injector nozzle 24, which is disposed within the grinding chamber and below the cover 14.

[0026] Although the first and second product injector nozzles 24a, 24b, in this example, are shown to be substantially identical, it is considered that any one or more of the product injector nozzles 24 may not be identical but may be configured to deliver different products and / or additives to the grinding chamber 18.

[0027] An exhaust orifice 36 allows ground particulate matter to be exhausted from the grinding chamber 18. In this example, the exhaust orifice 36 extends upwards through the cover 14 and is aligned with the central axis of the grinding chamber when the cover 14 is operatively fixed to the mill body 12, as shown in Figure 1. The exhaust orifice 36 includes a generally cylindrical tube section that is generally oriented vertically in the operative position and extends through the cover 14; however, other shapes, forms, and / or locations of the exhaust orifice 36 may be used. For example, the exhaust orifice 36 may also or alternatively extend downwards through a wall Petition 870250085933, dated 09 / 23 / 2025, p. 17 / 35 12 / 16 of the lower part of the grinding chamber 18. The exhaust orifice 36 is preferably aligned with the central vertical axis so that smaller particles will migrate radially into and eventually exhausted from the grinding chamber 18 through the exhaust orifice(s) 36.

[0028] The spiral jet mill 10 can be used to grind a granular product, such as TiO2 pigment particles and / or other granular products, by simultaneously injecting a first stream of an inlet gas and granular product mixture into the grinding chamber 18 through the first product injector nozzle 24a and injecting a second stream of an inlet gas and granular product mixture into the grinding chamber through the second product injector nozzle 24b. The grinding material is also injected into the grinding chamber 18 through the grinding gas injector orifice so as to impact and grind the granular product of the first and second streams into smaller particle sizes. The grinding material is preferably pressurized gas, such as steam, air, and / or nitrogen, but may be or include other compressed gases, and / or other grinding materials, such as hard grinding particles. The inlet gas is preferably steam, but may be or include other compressed gases.Ideally, the first and second streams of inlet gas and granular product, as well as the grinding material, are all injected into the grinding chamber simultaneously, although this may not be strictly necessary.

[0029] The ratio of total injected gas (e.g., inlet steam plus grinding steam) to grinding product (e.g., TiO2 pigment particles) can be in a wide range. For example, the ratio of total injected gas to granular product can be between about 0.1:1 to 10:1, preferably between about 0.2:1 to 5, and more preferably between about 0.5:1 to 3:1. In a pre-processing method Petition 870250085933, dated 09 / 23 / 2025, page 18 / 35 13 / 16 injured, the ratio of total injected gas (e.g., inlet steam plus grinding steam) to granular product (e.g., TiO2 pigment particles) is approximately 1.5:1, for example, 1.54:1, with the inlet gas being approximately 54% of the total gas (i.e., inlet gas plus grinding gas) injected into the grinding chamber per unit time. As seen from the detailed examples below, this total gas to TiO2 pigment inlet ratio (~1.5:1) provides a 23% energy input saving compared to conventional TiO2 jet grinding techniques that use a total gas to TiO2 pigment inlet ratio of 2:1. However, the method and apparatus need not be limited to these particular ranges because the energy efficiencies and yield advantages of a multi-inlet micronizer (spiral jet mill) as described here could be realized over a much wider range.In fact, the benefit will be greater the higher the actual or standard ratio (total steam:product) with only one inlet. For example, if the ratio of a conventional spiral jet mill having only a single inlet (i.e., one product injector) is 5:1, and with a new spiral jet mill having a double inlet (i.e., two product injectors), the new spiral jet mill will be able to reduce the ratio of total steam inlet to product inlet in the mill by about 25%, resulting in a ratio of 3.75:1 and a saving of 1.25 tons of steam per ton of product. In comparison, for a conventional spiral jet mill (single product injector) using a total steam:product ratio of 2:1 to grind TiO2 pigment particles, the same 25% reduction when using a spiral jet mill with two product injectors results in a total steam:product ratio of 1.5 and a saving of 0.5 tons of steam per ton of product.For other types of granular products being ground, the conventional ratio... Petition 870250085933, dated 09 / 23 / 2025, page 19 / 35 14 / 16 The ratio of total gas inlet versus total granular product inlet may differ from that for TiO2 particles. However, the use of multiple nozzles to reduce the total vapor:product ratio to a conventionally lower ratio, according to the concepts discussed here, would also be possible.

[0030] As shown below, the use of a spiral jet mill with two (or more) nozzles according to certain aspects of the invention can lead to significant energy savings in grinding TiO2 pigments for use in various end products. In the following examples, the energy consumption required to grind a granular product, which in these examples are TiO2 pigment particles, consists primarily of the inlet steam and grinding steam. If, instead of the single product injection nozzle of the conventional mill, one or more additional product injection nozzles are fed into the mill and the grinding steam input is kept constant, there is a potential saving in the required energy requirement. Compared with a mill with only one product injection nozzle, there is a higher solids face, i.e., there are more particles per volume in the grinding chamber 18, which leads to a greater probability of particle-particle collisions and thus to more efficient grinding.Furthermore, the total volume flow of granular product and inlet gas is increased by the additional inlet, which leads to increased velocities within the grinding chamber, and which in turn increases fragmentation efficiency. The increase in radial velocity also leads to greater selectivity of the static visualization process, which prevents coarse material from leaving the mill when the mill is discharged.

[0031] The following are some investigations and some non-limiting examples that illustrate certain, but not necessarily all, potential applications of the principles described above. Petition 870250085933, dated 09 / 23 / 2025, page 20 / 35 15 / 16

[0032] Baseline Example 1: In a first comparative baseline example, a conventional method of using a conventional spiral jet mill having a single product injection nozzle and fourteen grinding nozzles is considered. The spiral jet mill is operated with a throughput of four tons per hour of granular product to be ground (e.g., TiO2 pigment particles) at a total steam to pigment ratio of 2:1 with inlet steam being 54% of the combined inlet steam and grinding steam, i.e., inlet steam of 4320 kg / h and grinding steam of 3680 kg / h distributed over fourteen grinding nozzles. (Note, all tons in this and subsequent examples are metric tons = 1000 kg).

[0033] Example 2: In a second example according to certain aspects of the invention, a spiral jet mill with two product inlet nozzles (as described above) and fourteen grinding nozzles is considered. A double inlet of TiO2 pigment particles (granular product to be ground) and inlet steam, i.e., 8 ton / h of product and 54% of the combined inlet steam and grinding steam, provides an inlet of 2 x 4320 kg of inlet steam = 8640 kg / h of steam and 8 ton / h of pigment plus 1 x 3680 kg / h of grinding steam (total combined steam inlet of 12,320 kg / h). This example leads to an energy saving of 3680 kg / h of steam. In this example, the total steam to pigment ratio is 1.54:1 (instead of 2:1), which corresponds to an energy saving of 230 in direct comparison with baseline example 1 and a simultaneous 100% increase in yield capacity of granular product (e.g., the product) being ground.

[0034] Baseline Example 3: In a third comparative baseline example, a conventional spiral jet mill with one product injection nozzle and six grinding nozzles is used Petition 870250085933, dated 09 / 23 / 2025, page 21 / 35 16 / 16 of 130 kg / h of pigment, 140 kg / h of inlet steam, and 120 kg / h of grinding steam distributed over 6 grinding nozzles is injected into the spiral jet mill. The total steam-to-pigment ratio is 2 tons of steam per 1 ton of pigment (i.e., 2:1).

[0035] Example 4: In a fourth example according to certain aspects of the invention, a spiral jet mill with two product injection nozzles (as described above) and six grinding nozzles is used. A double pigment and steam inlet is used, i.e., 2 x 130 kg / h = 260 g / h of product, 2 x 40 kg / h of steam inlet, plus 1 x 120 kg / h of grinding steam = 400 kg / h of total steam output. This example leads to an energy saving of 129 kg / h, where the total steam to pigment ratio is 1.54:1 (instead of 2:1). This corresponds to an energy saving of 23% compared with baseline example 3 with a 100% capacity increase.

[0036] From these examples, it can be seen that a spiral jet mill with two or more product injection nozzles can provide significant energy savings over conventional grinding mills, as well as increased product yield, in a way not previously considered. As such, a spiral jet mill and operation of such a mill according to certain aspects of the invention can also provide a more energy-efficient way to grind TiO2 pigment particles and other granular products. Petition 870250085933, dated 09 / 23 / 2025, page 22 / 35

Claims

1 / 4 CLAIMS 1. Spiral jet mill (10), comprising: a collector (16) surrounding and at least partially defining a grinding chamber (18); a grinding gas injector orifice (20) extending through the collector into the grinding chamber to inject grinding material into the grinding chamber; a cover (14) over the collector, the cover at least partially defining the grinding chamber; and an exhaust orifice (36) to exhaust the ground product from the grinding chamber; and a first product injector nozzle (24a) directed into the grinding chamber and configured to mix and inject a first inlet gas vapor and a granular product into the grinding chamber; characterized in that the spiral jet mill further comprises: a second product injector nozzle (24b) directed into the grinding chamber to mix and inject a second inlet gas vapor and the granular product into the grinding chamber.

2. Spiral jet mill (10), according to claim 1, characterized in that at least one of the first and second product injector nozzles (24a, 24b) extends through the cover (14).

3. Spiral jet mill (10), according to either of claims 1 and 2, characterized in that each of the first and second product injector nozzles (24a, 24b) extends through the cover (14).

4. Spiral jet mill (10), according to any one of claims 1 to 3, characterized in that each of the Petition 870250085933, dated 09 / 23 / 2025, page 23 / 35 2 / 4 first product injector nozzle (24a) and second product injector nozzle (24b) is tangentially aligned and offset from a centerline (19) of the grinding chamber (18).

5. Spiral jet mill (10), according to any one of claims 1 to 4, characterized in that each of the first product injector nozzle (24a) and second product injector nozzle (24b) is aligned to inject the first and second respective streams in the same clockwise or counterclockwise direction around the grinding chamber (18).

6. Spiral jet mill (10), according to any one of claims 1 to 5, characterized in that the first product injector nozzle (24a) is aligned parallel to the second product injector nozzle (24b).

7. Spiral jet mill (10), according to any one of claims 1 to 6, characterized in that the first product injector nozzle (24a) and the second product injector nozzle (24b) are arranged on opposite sides of the center line (19).

8. Spiral jet mill (10), according to any one of claims 1 to 7, characterized in that each of the first product injector nozzle (24a) and second product injector nozzle (24b) has an injection end (34) within the grinding chamber (18), wherein the injection end of each of the first product injector nozzle and the second product injector nozzle is located at the same radial distance from the centerline (19).

9. Spiral jet mill (10), according to any one of claims 1 to 8, characterized in that it further comprises a third product injector nozzle (24) directed to the grinding chamber (18), configured to mix and inject a third stream of inlet gas and granular product into the grinding chamber.

10. Method of grinding a granular product using the spiral jet mill, as defined in any one of claims 1 to 9, characterized in that it comprises the steps of: simultaneously injecting the first stream of an inlet gas and granular product mixture into the grinding chamber (18) through the first product injector nozzle (24a) and injecting the second stream of an inlet gas and granular product mixture into the grinding chamber through the second product injector nozzle (24b); injecting the grinding material into the grinding chamber through the grinding gas injector orifice (20) so as to impact and grind the granular product of the first and second streams into smaller particle sizes.

11. Method according to claim 10, characterized in that the inlet gas comprises inlet steam.

12. Method, according to any one of claims 10 and 11, characterized in that the granular product comprises TiO2 pigment particles.

13. A method according to any one of claims 10 to 12, characterized in that the grinding material comprises pressurized gas.

14. Method, according to any one of claims 10 to 13, characterized in that the pressurized gas comprises at least one of grinding steam, air, and / or nitrogen.

15. A method according to any one of claims 10 to 14, characterized in that the first and second streams and the grinding material have a ratio of total inlet gas and grinding material to granular product between about 0.1:1 and 10:

1.

16. Method, according to any one of claims 10 to 15, characterized in that the granular product comprises TiO2 pigment particles, the inlet gas comprises steam, and the grinding material comprises steam, and wherein the first and second streams and the grinding material have a total steam to TiO2 pigment particle ratio of less than about 2:1.

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