Method for magnetic stabilizing of fluidal layers

The method for magnetic stabilizing of fluidal layers consists in placing fluidal layers of ferromagnetic particles in a magnetic field that is axially gradient and oriented parallel to the direction of fluidizing. In order to achieve dynamic uniformity of the layer the magnetic field can be oriented colinearly to the direction of fluidizing. For manifold increase in the fluidizing flow the magnetic moment of the particles can be oriented against the direction of the fluidizing flow. This method can be used in heterogenic and physical processes with fluidal layers of ferromagnetic particles, f.e. catalytic processes, filtration etc.

The invention refers to a method for magnetic stabilizing of fluidal layers 
that can be used in heterogenic and physical processes with fluidal layers 
of ferromagnetic particles, i.e. catalytic processes, filtration, etc. 
A method for magnetic stabilizing of fluidal layers is known in which the 
fluidized and magnetized particles of the layer are placed in the volume 
of a solenoid creating an uniform magnetic field. The magnetic device 
forming the magnetic field is disposed around the fluidal layer. 
A disadvantage of the known method is that it can be used only with low 
layers for which the ratio between the layer and the diameter of the 
apparatus is smaller than 1. The small height of the layer deterioates the 
gas distribution. The homogenic action of the field can not remove the 
gradient of the gravity forces with respect to the particles along the 
height of the layer and no uniform structure can be attained during the 
stabilisation of the particles. The uniformity of the field depends on the 
geometric dimensions of the layer and apparatus. This hampers the 
technological use of the method and limits the linear velocity of the 
passing fluid. 
The object of this invention is to provide a method for magnetic 
stabilizing of fluidal layers that can be used for high layers 
independently of the ratio between the layer's height and the apparatus 
diameter; to eliminate the requirement for axial uniformity of the field; 
to improve the gas distribution; to eliminate the influence of the 
gradient of the gravity forces along the layer height and to limit the 
friction forces between the layer and the walls of the apparatus that is 
ensuring an uniform structure of the layer. 
This object is attained by a method for magnetic stabilizing of fluidal 
layers in which the fluidal layers of ferromagnetic particles are placed 
in a magnetic field whereby the magnetic field is axially gradient and is 
oriented parallel to the direction of fluidizing. 
In order to achieve dynamic uniformity of the layer the magnetic field is 
oriented colinearly to the direction of fluidizing. For multiple increase 
in the fluidizing flow the magnetic moment of the particles can be 
oriented against the direction of the fluidizing flow. 
The advantage of the method according to the invention are the following: 
The height of the stabilized layer is increased with respect to same 
diameter of the apparatus; the difficulties in providing an axial 
uniformity of the magnetic field are surmounted; the gas distribution 
along the layer height is improved; the gradients of the gravity forces 
along the layer length are removed; the friction between the layer and the 
walls of the apparatus is limited; the axial structure uniformity of the 
stabilized layer is increased.

The FIGURE shows an embodiment of the invention. 
The generating in the particles of gradiently changing magnetic moment that 
is colinear to the direction of the fluidizing flow provides a dynamic 
uniformity in the behaviour of the layer. The axial gradient orientation 
of the magnetic moment neutralizes the longitudinal gradient of the 
gravity forces. This permits the increase in the layer's height and 
ensures a reduced resistance from friction with the walls of the 
apparatus. 
The generating in the particles of a gradiently changing magnetic moment 
against the direction of the fluidizing flow eliminates the axial gradient 
of the gravity forces and provides the necessary conditions for a manifold 
increase in the velocity of the fluidizing flow without arising of 
circulation and bubble forming in the layer. 
The following examples illustrate better the substance of the invention 
however without limiting its scope: 
EXAMPLE 1 
In a tube with diameter 100 mm are poured ferromagnetic particles with size 
60 to 80 microns. The ratio between the height of layer "h" and the 
diameter of the apparatus "D" is 0.8. The apparatus is placed in the 
volume of a solenoid that generates a field with gradient .DELTA.H, 
colinear to the direction of the fluidizing flow. After the velocity for 
minimal fluidizing are obtained the following values for hydraulic 
resistance .DELTA.P and the velocity "V" at which the magnetic stabilizing 
is perturbed: 
______________________________________ 
Intensity of 
magnetic field 
.DELTA.H 
.DELTA.P Velocity 
Height of 
H, Oe % mm,w. column 
v,m/s layer,h cm 
______________________________________ 
165 35 47 0,12 8,2 
165 42 53 0,20 8,9 
165 40 51 0,29 9,1 
165 40 51 0,35 10,2 
______________________________________ 
The value of .DELTA.H is determined by the difference of H, the value 
measured between the centre of the solenoid and the centre of the layer. 
The data indicate that with the increase in .DELTA.H, of .DELTA.P is 
relatively constant that is due to the increase in the free volume as a 
result of expansion of the layer. 
EXAMPLE 2 
In a tube with diameter "D"=90 mm is poured a layer with height 100 mm. The 
size of the particles is 60 to 80 microns. The apparatus is disposed in 
the volume of a solenoid whose gradient is oriented against the direction 
of the fluidizing flow. The intensity of the magnetic field is 224 Oe. The 
following values for .DELTA.P, the height of the layer and the velocity 
"v" have been obtained at which the magnetic stabilizing is perturbed: 
______________________________________ 
.DELTA.H 
.DELTA.P h v 
% mm w. column cm m/s 
______________________________________ 
15 57 10,2 0,32 
30 53 10,4 0,41 
42 55 10,6 0,53 
52 54 12,2 0,56 
60 53 13,1 0,62 
______________________________________ 
The change in the values of .DELTA.H ensures a constancy of the hydraulic 
resistance .DELTA.P and an increasing velocity at which the magnetic 
stabilizing is perturbed. The expansion of the layer is also linked with 
.DELTA.P. 
EXAMPLE 3 
In the conditions of examples 1 and 2 is poured a different quantity 
ferromagnetic material with height of layer "h" that is modified with 
respect to the diameter of the apparatus "D". The intensity of the 
magnetic field is 320 Oe. The gradient of the field is generated by 
different positions of the magnetic device along the height of the layer. 
Following values for .DELTA.P and "h" are obtained depending on .DELTA.H. 
______________________________________ 
h = 
h = 0,5 D h = D 1,5 D h = 2 D h = 2,5 D 
.DELTA.H 
.DELTA.P mm 
h h h h h 
% w. cln cm .DELTA.P 
cm .DELTA.P 
cm .DELTA.P 
cm .DELTA.P 
cm 
______________________________________ 
15 27 58 54 120 92 162 112 221 148 272 
30 29 60 56 122 96 170 114 228 150 278 
42 28 60 55 120 90 170 116 230 152 280 
62 27 60 54 121 92 172 112 226 150 280 
60 27 58 54 120 92 173 112 223 150 280 
______________________________________ 
In increasing the linear velocity and the changing of .DELTA.H, the value 
of .DELTA.P remains constant due to the eliminating of the gradient forces 
of gravity without limitations from the height of the layer for the 
experimental conditions. 
EXAMPLE 4 
In a convertor for synthesis of ammonia with diameter of the reaction tube 
30 mm is poured in a catalyst for ammonia synthesis with particle size of 
300-400 microns. The height of the layer is 3.14 times greater than the 
diameter of the reaction tube. The apparatus is placed in the volume of a 
solenoid which generates a magnetic field due to the running along the 
windings of direct current. The disposition of the solenoid along the 
height of the layer modifies the axial gradient of the field from 0 to 
60%. The catalytic process is performed under pressure 10, 20 and 30 MPa 
and at temperature 500.degree. C. The degree of conversion evaluated after 
the ammonia content in the converted gas for volumic rate 120,000 
h.sup.-1, linear velocity 0.2 m/c for intensity of the field 125 Oe is the 
following: 
______________________________________ 
pres- 
sure 10 MPa 20 MPa 30 MPa 
.DELTA.H, % 
0 30 60 0 30 60 0 30 60 
______________________________________ 
vol. % 
4,95 4,85 5,30 9,45 9,65 9,40 14,4 13,89 
14,40 
NH.sub.3 
______________________________________ 
The data show that the modification of the magnetic axial gradient .DELTA.H 
is not causing a change in the degree of conversion which means that the 
gradient stabilizing of the layer is not calling forth structure defects 
and a not effective contact in the catalytic process. 
EXAMPLE 5 
In a tube of organic glass with diameter 80 mm is poured in a layer with 
height 100 mm composed of ferromagnetic particles with size 150 to 215 
microns. The tube is placed in the volume of the solenoid on the windings 
of which is running the direct current. The field intensity is 180 Oe. The 
axial disposition of the solenoid generates a gradient along the height of 
the layer that attains 100% with respect to the intensity of the magnetic 
field generating it. After the velocity for minimal fluidizing through the 
layer is passed polluted air with size of the dust particles up to 25 
microns. The degree of dust removal after the layer is 99.4 to 99.9%. The 
high degree of dust removal is a prove for the structural homogenity of 
the layer. The increase in the free volume augments the filtering capacity 
of the gradiently stablized layer.