Mixing method and apparatus

Method of mixing particulate materials comprising contacting a primary source and a secondary source thereof whereby resulting mixture ensues; preferably at least one of the two sources has enough motion to insure good mixing and the particulate materials may be heat treated if desired. Apparatus for such mixing comprising an inlet for a primary source, a reactor communicating therewith, a feeding means for supplying a secondary source to the reactor, and an inlet for the secondary source. Feeding means is preferably adapted to supply fluidized materials.

The present invention relates to a new and novel method and apparatus for 
mixing particulate materials. More particularly, the invention relates to 
such a method and apparatus for the mixing of fluid media containing 
particulate materials dispersed therein. Still more particularly, the 
invention relates to such a method and apparatus in which certain chemical 
and/or physical reactions result from such mixing, and in which certain 
useful products result. Even more particularly, the invention relates to 
such a method and apparatus which is continuous. 
Coaxial fluid jet streams have been used in the past to promote the 
turbulent mixing thereof for the purpose of producing a well integrated 
combustible mixture. Combustible mixtures have also resulted from the 
introduction of a primary jet stream of a particle laden material into a 
secondary air stream. Such stream mixing has not been applied to mixing 
streams, each containing fine particulate material, nor has it been used 
as a method to transfer thermal energy between the streams. 
Multiple nozzle systems for contacting multiple jet streams in order to 
promote the mixing thereof usually result in a high degree of abrasion in 
the apparatus employed because high velocities are required as a rule; 
such systems are also characterized by a high pressure drop in the 
apparatus which causes lesser efficiency in the operation thereof. 
Prior methods of mixing particulate materials have not been as rapid or as 
thorough as might be the case. 
Literature relating to prior art mixing applications is found: 
1. Perry, R. H., et al., Chemical Engineers Handbook, McGaw Hill (1963), 
pp. 5-18. 
2. Hill, B. J., J. Fluid Mech., 51(4) pp. 773-779 (1972). 
3. Tufts, L. W., and Smoot, L. D., J. Spacecraft, 8(12) pp. 1183-1190 
(1971). 
It is therefore an object of the present invention to provide a new and 
novel apparatus and method of mixing particulate materials. 
Another object of the present invention is to provide apparatus and method 
of such types which involve contacting a source of particulate materials 
of a selected type with a second source of particulate materials of 
another selected type. By another selected type of particulate material is 
meant that the second solid particulate material is different in substance 
from the first particulate material. 
Still another object of the present invention is to provide apparatus and 
method of such types in which certain of the particulate materials are 
first preheated before use, whereby thermal energy is transferred to the 
other particulate materials in the method, upon contact. 
Yet another object of the present invention is to provide apparatus and 
method for mixing particulate materials which appreciably reduce the 
degree of abrasion in apparatus encountered normally in the prior art. 
A further object of the present invention is to provide apparatus and 
method of the aforementioned types which significantly reduce the amount 
of pressure drop normally encountered in the prior art. 
Still a further object of the present invention is to provide apparatus and 
method of the aforementioned types which are more efficient than those of 
the prior art. 
Yet a further object of the present invention is to provide apparatus and 
method of the aforementioned types which are faster and more thorough than 
those of the prior art.

The present inventive method of mixing essentially involves the step of 
contacting a primary source of particulate materials and a secondary 
source of particulate materials, whereby a resulting mixture ensues. 
Preferably the materials are then allowed to stay in contact sufficiently 
long enough for a desired chemical and/or physical reaction to proceed 
appreciably. Then preferably, desired reaction products are removed from 
the resulting mixture of particulate materials. 
The secondary source may be non-moving or moving, preferably relatively 
stagnant or slow-moving with respect to the primary source which 
preferably has more motion. The only requirement is that when the two 
sources are brought together, there be sufficient total motion from both 
sources to insure good enough mixing of the particulate materials to be 
able to detect an appreciable degree of the desired chemical and/or 
physical change. Preferably, the primary source is given considerable 
motion and most of the mixing done thereby, while the secondary source 
gets little. 
The secondary source of particulate materials may be any conventional one, 
but preferably is an inert fluid medium in which the particulate materials 
are dispersed; more preferably the materials are uniformly dispersed in 
the medium. More preferably, the fluid medium is a gaseous one and may 
include a mixture of gases if desired. 
The particular particulate materials present in the secondary source may be 
any which are desired to be brought into contact with the primary source. 
In many applications, the particular particulate material is preferably 
coal and/or coal chars. 
The particulate materials which are preferably dispersed in a fluid medium 
to form the secondary source may be dispersed by conventional means, 
entrainment for example, but are preferably dispersed by means of 
fluidizing the particulate materials, preferably by the gas injection 
thereof or by treatment in a fluidizing chamber. 
The secondary source of particulate materials preferably takes the form of 
a slow moving stream or entrained stream in comparison with the primary 
source of particulate materials which is preferably a fast moving stream 
or entraining stream. Contact of the two streams produces a resulting 
mixture, a stream also preferably. 
The primary source of particulate materials may be conventional but 
preferably is a fluid medium containing the materials, more preferably, 
the medium is gaseous and may include mixtures of gases if desired. Even 
more preferably, the medium is steam or an inert gas mixture. The 
particulate materials are preferably dispersed throughout the medium; more 
preferably, the particulate materials are preferably dispersed uniformly 
throughout the medium. 
The particular particulate materials present in the primary source thereof 
may be any having suitable properties. In many applications, the materials 
are preferably the char resulting from the pyrolysis of coal or coal 
itself. 
The particulate materials present in the primary source and preferably 
dispersed uniformly therein may be so dispersed by any conventional means 
but preferably are dispersed by means of imparting turbulent flow to the 
source by pressurizing it sufficiently and giving it direction. 
Considerable motion is also imparted to the primary source as a result 
which is useful for contacting the secondary source of particulate 
materials later on. 
The particulate materials of the present method may be heat treated as an 
additional step if desired; either the primary or the secondary source 
thereof or both sources may be heat treated before or after contacting 
them together if desired. In many applications, the primary source is 
preferably preheated before contact in order that the thermal energy 
thereof be imparted to the secondary source of particulate materials upon 
contact. More preferably, recycled char from the pyrolysis of coal is used 
to heat the primary source. Additional treatment heat may be supplied to 
the resulting mixture from the contact of the primary and secondary 
sources, if desired. 
The resulting mixture, preferably a stream, from the contact of the primary 
source and the secondary source contains a mixture of particulate 
materials dispersed therein which will react physically and/or chemically, 
given sufficient time. The materials in the mixture are preferably 
dispersed throughout, more preferably uniformly dispersed throughout the 
mixture, preferably by means of imparting a turbulent flow thereto by 
sufficient pressurization and by giving it direction. More preferably, the 
primary source is made turbulent enough initially to impart turbulence to 
the resulting mixture after contacting the secondary source of particulate 
materials. 
After the desired reaction has taken place, desired products are separated 
from the resulting mixture. Volatile products may be taken off directly, 
resulting char may be recycled back to the present primary source for 
reuse in the method, and some gas taken off and recycled back to the 
secondary source of particulate materials for use in fluidizing them. 
The present inventive apparatus is directed to a mixing section for mixing 
particulate materials which has a first inlet, preferably generally 
vertically disposed, for admitting a primary source of particulate 
materials or entraining stream. The first inlet has an end which 
terminates within the mixing section which is preferably constricted to 
form a nozzle for increasing the velocity of the stream as it passes 
therethrough, the nozzle preferably being refractory-lined. 
The mixing section also has a reactor which communicates with the 
aforementioned end of the first inlet to receive the entraining stream 
therefrom and also communicates with a cyclone receiver which separates 
gaseous and solid products from the resulting mixture after reaction has 
taken place. 
The mixing section further has feeding means for receiving and feeding an 
incoming secondary source of particulate materials or entrained stream to 
the entraining stream coming in through the first inlet. The feeding means 
communicates with the reactor, providing access for a supply of 
particulate materials. The inlet to the reactor forms a weir means for the 
flow of the secondary source of particulate materials from the feeding 
means into the reactor. The entrained stream may enter the feeding means 
from any direction or angle as long as the materials introduced can work 
their way into the reactor. 
The feeding means is preferably a fluidizing means for fluidizing the 
incoming particulate materials. Preferably, the fluidizing means is a 
fluidizing chamber adapted for such purposes. In some applications, the 
chamber is adapted to fluidize the incoming materials by imparting 
sufficient motion thereto. More preferably the chamber is annular and 
adapted to impart such motion as a result. The direction or angle at which 
the entrained stream comes into the chamber may also be adapted to help 
impart such motion thereto as may be the location of the point of entry of 
the stream into the chamber and the velocity thereof. 
In certain applications, the entrained stream comes into an annular chamber 
at a lower portion thereof and generally horizontally thereto the chamber 
being so adapted; more preferably, the stream comes in tangentially to the 
chamber which is suitably adapted and a swirling motion is imparted as a 
result. 
In other applications the fluidizing chamber is adapted for fluidizing by 
virtue of having injection means provided therewith. The injection means 
provides apparatus for the injection of particulate materials by fluid, 
preferably gas, and preferably takes the form of a porous bed or plate 
which is adapted to operate on gas, preferably recycle gas from the 
method; the porous bed or plate allows some gas to get through it when 
pressurized sufficiently which gas does the injecting. Particulate 
materials coming into the chamber are thus fluidized. 
The injection means provided for the fluidizing chamber is preferably 
positioned inside the chamber and more preferably at the bottom thereof. 
The particulate materials coming into the chamber may be introduced from 
any direction or angle but are preferably introduced generally vertically 
from above. 
The mixing section still further has a second inlet for receiving a 
secondary source of particulate materials or entrained stream; the second 
inlet is connected to the feeding means, preferably generally horizontally 
at a lower portion thereof. More preferably the feeding means is annular 
and the second inlet is connected tangentially thereto. 
In some applications, the second inlet is provided with additional 
fluidizing means for fluidizing the particulate materials prior to entry 
into the feeding chamber. The additional fluidizing means are preferably 
additional injection means and preferably an air slide connected to the 
second inlet whereby particulate materials moving through the inlet are 
injected by air from the slide. More preferably, the air slide is adapted 
to operate on recycle gas from the method. 
In other applications, the second inlet is preferably connected 
substantially vertically to the feeding means. 
Turning now to the drawing, the first three FIGS. are directed to a 
secondary source of particulate materials which is coal and to a primary 
source of particulate materials which is char resulting from the pyrolysis 
of coal dispersed in stream; FIG. 4 is directed to a secondary source of 
particulate material which is char resulting from the pyrolysis of coal 
dispersed in steam and the primary source of particulate materials is 
coal. 
In FIG. 1, the char stream comes rapidly enough into the mixing section, 
generally designated 10, through a generally upright annular first inlet 
12 which has an end 14 terminating within the section and constricted at 
16 to form a nozzle, so that a fluid jet is formed thereby. A reactor 20, 
also annular, has an upper end 22 which is open and of larger diameter 
than the nozzle which surrounds the nozzle, leaving an opening between the 
upper end and the nozzle. In the embodiment shown in the FIGS., the inlet 
inside periphery of the reactor is substantially equal to the inside 
periphery of conduit reactor 20. In this embodiment, the inlet inside 
periphery is significantly greater than the outside periphery of the 
turbulent solid particulate stream forming means or nozzle 16. In general, 
inlet 22 of reactor 20 is completely open ended except for nozzle 16. In 
general, the opening is substantially larger than a slit. The reactor has 
an elbow in the middle which rests upon a support and has a lower end 24 
connected to a cyclone receiver for separating gaseous from solid 
products. An annular fluidizing chamber 28 is formed by an annular section 
30 which connects the first inlet and the upper end 22 of the reactor, the 
chamber surrounding the nozzle and a portion of the upper end of the 
reactor. A second annular inlet 32 is generally horizontally connected to 
the annular fluidizing chamber at a low portion 34 thereof for receiving a 
stream of coal dispersed in air, the inlet also being tangentially 
positioned with respect to the annular chamber wall to impart a swirl to 
the incoming stream. Incoming coal builds up in the fluidizing chamber 28 
and is expelled over the upper end 22 of the reactor, through the opening 
between the upper end thereof and the nozzle, into the reactor itself. 
Once inside the reactor, the coal soon falls into the path of the 
turbulent fluid jet of the char stream coming from the nozzle, where it is 
acted upon by the jet as shown by broken lines. Once inside the reactor, 
the jet has a free core region extending considerably into the reactor but 
expansion of the jet also occurs which entrains coal present, with 
complete mixing of the coal and the jet later on. 
In FIG. 2, the apparatus is the same as that in FIG. 1 except that the 
second annular inlet is different. The inlet 35 has a generally horizontal 
portion 36 like second inlet 32 and adapted to receive an air slide 38 and 
being so equipped; the air slide is preferably adapted to operate on 
recycle gas instead of air. The inlet also has a generally upright portion 
40 communicating with the horizontal portion 36 through which coal is 
introduced. Coal so vertically introduced is fluidized by injected gas 
from the slide before its introduction into the fluidizing chamber. 
In FIG. 3, the apparatus is the same as in FIG. 2 except that the second 
annular inlet 42 for introducing coal comes generally vertically instead 
of horizontally into the fluidizing chamber and in that a porous bed or 
plate 44 has been provided at the bottom of the chamber and connected to a 
source of recycle gas and adapted to operate thereon in order to fluidize 
such incoming coal by injecting the coal with gas. 
In FIG. 4, the apparatus is similar to that of FIG. 3, except that the coal 
stream is introduced through the first inlet instead of the char stream, 
the char stream being introduced generally vertically instead to the 
fluidizing chamber from an upright second inlet 46. The flow paths of the 
char and coal streams are in FIG. 4 exactly the opposite of what they are 
in FIG. 3. The coal stream in FIG. 4 is introduced rapidly enough to form 
a jet stream which acts upon the char stream as shown by the broken lines, 
like in FIG. 1. 
In practice, a hot char recycle stream is fed to the mixing section shown 
in FIG. 1 through a seven-foot diameter vertical first inlet. The char 
stream velocity is 20 feet per second in the inlet but is increased to 94 
feet per second by passing through a nozzle 39 inches in diameter and 
positioned at the end of the inlet inside the mixing section. 
Feed coal is pneumatically conveyed by recycle gas to the mixing section in 
a 5 inch diameter generally horizontal second inlet. The coal is then 
discharged tangentially into a low portion of the annular fluidizing 
chamber and fluidized thereby. 
The coal is then expelled over the outer wall of the reactor and through 
the open end thereof, through the opening between the open end of the 
reactor and the nozzle and then into the inside of the reactor where it 
falls into the path of the char stream jet coming from the nozzle which is 
turbulent. The reactor is annular and has the same diameter as the first 
inlet. 
Fluidized coal in the reactor is entrained by the turbulent jet which 
expands once inside the reactor. 
About ten feet of reactor length is required for such entrainment and 
another six feet is required for the jet to disappear and the two streams 
to mix completely. About 0.5 to 0.6 seconds is required for complete 
mixing. 
The resulting mixture stream leaves the reactor at a velocity of 21 feet 
per second. The jet from the nozzle is maintained at turbulent flow by 
having a Reynolds number of 100,000. The resulting mixture stream is also 
maintained at turbulent flow by having a Reynolds number of 220,000. 
Other details of the apparatus and method are tabulated below: 
______________________________________ 
Product Product 
Char Recycle 
Coal Feed Gas Char 
______________________________________ 
Solids rate 
pounds/hour 
14,300,000 860,737 -- 14,760,659 
Gas rate, 
pounds/hour 
134,794 10,000 603,502 
-- 
Temperature, 
Degrees 
Fahrenheit 
1,789 145 1,600 1,600 
Pressure, 
pounds/ 
sq. inch 
absolute 64 66 62 62 
Gas 
Molecular 
Weight 18 31.5 27 -- 
______________________________________ 
Some materials exhibit a plastic or tacky state when heated sufficiently 
which could plug the present mixing apparatus if used therein. For 
example, some coals exhibit this property but will lose their tackiness 
upon being heated sufficiently additionally; tackiness is thus a 
transitory state which can be overcome with sufficient heat. 
Particulate materials exhibiting such tackiness can be used in the present 
apparatus without fear of plugging if they are heat treated sufficiently, 
either before or during the present method. That is, if sufficient heat is 
applied to the particulate materials, the tacky state is gone through 
rapidly enough to avoid the problem. Preferably, the primary or entraining 
stream of particulate materials is heated sufficiently during the 
contacting of the secondary or entrained stream to transfer sufficient 
heat to get such materials in the former stream through the tacky state 
rapidly enough after mixing to avoid the plugging problem. 
For example, some Eastern coals exhibit the property of tackiness when 
first heated, but the tackiness disappears with additional heating. 
Particulate material going to the reactor from the feeding means may be 
entrained rather than fluidized but the present apparatus and method would 
not be as efficient in operation. Such particulate material is preferably 
not introduced to the reactor at very high velocity because it would 
require too high a velocity of the entraining stream otherwise. 
The mixing time of the present process is dependent upon the geometry of 
the apparatus and the flow conditions of the streams. It is desirable to 
minimize such time. 
The entraining stream or primary source of particulate materials from the 
first inlet is preferably always turbulent and is assigned an appropriate 
Reynolds number to insure this condition. The entrained stream or 
secondary source of particulate materials from the second inlet is 
preferably always maintained at a rate of flow much less than turbulent. 
The resulting mixture stream from the contacting of the entraining and the 
entrained streams is preferably always turbulent also and is maintained at 
an appropriate Reynolds number to accomplish the result. The relatively 
fast moving entraining stream thus preferably picks up the relatively slow 
moving entrained stream, comparing the two streams together, to form a 
resulting mixture stream which is still fairly fast moving in comparison 
with the entraining stream. 
The nozzle which is preferably refractory-lined may be lined with any 
conventional material such as a variety of annealed stainless steel, 
inconel, cast steels, and the like. 
In operation, an acceptable fluid velocity to the cyclone receiver is first 
selected and this velocity is chosen also for the resulting mixture stream 
in the reactor. Once the reactor velocity is selected, then the velocity 
of the entraining stream through the end, preferably constricted to form a 
nozzle, of the first inlet is picked to be substantially higher than the 
reactor velocity. Then the velocity of the entrained stream is selected to 
provide secondary particulate materials to the reactor at a lower velocity 
than the resulting mixture stream. 
The velocity of the entraining stream above the nozzle does not matter nor 
does the diameter of the first inlet as long as it is larger than that 
required for entraining the primary particulate materials. The nozzle 
velocity must be substantially greater than the inlet velocity however. 
The diameter of the nozzle does not matter as long as it is substantially 
less than the inlet diameter, in order that the velocity of the entraining 
stream be stepped up sufficiently to operate properly. 
The diameter of the reactor does not matter as long as it is significantly 
greater than the nozzle diameter, so as to permit proper expansion of the 
jet coming into the reactor from the nozzle. The nozzle velocity of the 
entraining stream entering the reactor must be greater than that of the 
resulting mixture stream, however, in order to have flow through the 
reactor. 
It will be apparent to those skilled in the art that all the objects and 
advantages previously set forth for the present invention have been 
accomplished. 
It is to be understood that only the preferred embodiments of the present 
invention have been set out and described in detail herein and that the 
invention may be practiced otherwise than as specifically set forth and 
described and within the scope of the appended claims.