Background of the invention
The invention relates to a method and devices for short-time
heat treatment and/or quenching of bulk materials and can be used at the stage of
thermochemical activation in producing catalysts, carriers, adsorbents, dehydrators,
fillers, ceramics, magnetic materials, inorganic pigments, solid electrolytes, medical
and cosmetic preparations, etc., in processes of drying/cooling in chemical, food,
woodworking and other industries.
A method for activating crystalline oxygen-containing compounds
by quick heating at the rate of hundreds and thousands degrees/minute of powder
particles due to their contact with gas flow, for example smoke fumes, or solid
heat carrier (the method for thermochemical activation /TCA/) is known (
, C01F7/30, 1975;
, CO1F7/02, 1981;
, C01F7/44, 1994). Such heating results in formation of decomposition products
having valuable chemical properties. Products of activation are subjected to cooling-quenching
at an outlet from a hot zone for fixation of amorphous state. The disadvantages
of this method are dust-laden gas emissions containing hazardous admixtures (NOx
, SOx, CO, hydrocarbons), contamination of initial substances by fuel
admixtures and products of incomplete burning, relatively long time required for
cooling-quenching process (10 minutes up to temperature 60°C) and low efficiency
of using energy of heat carriers leading to high specific power inputs.
An analogous method for heat treatment of initial of bulk
materials is its heating by moving along the surface of a vibrating groove in the
field of radiation gas burners at a temperature from 400 to 600°C for 5-30
, C01F7/44, 1973). Heating due to heat transfer in contact of initial material
particles with hot metal is more effective than heating particles through their
contacts between themselves or due to convective heat exchange in hot air flow.
The disadvantage of the known method is relatively low speed of material movement
along the groove and difficulties in providing uniform distribution of initial bulk
material along the heated surface of the groove due to its vibration. This disadvantage
is practically impossible to overcome when attempting to increase the size of the
groove for achieving output of more than 2 kg/hour.
Similar technical solution is an installation for pulse
heat treatment of bulk materials (patent
, C04B35/52, 20.07.1998). The installation comprises a tank for an initial
material, heaters and a drive for rotation. In the patent a method for pulse heat
treatment of bulk materials is also disclosed; the method comprises feeding, distributing
and moving initial material along a heated surface wherein particles of the material
are in relative motion and contact, and discharge of finished product in a storage
A device and a method for pulse heat treatment of bulk
materials are a most similar to the present invention (patent
, 7 BO1J8/10, 10.08.2002).
The invention according to the closest prior art solves
the following problems:
- controlling flow rate of bulk materials; even and dense distributing along a
heated surface; increasing the rate of heating a bulk material tights; fast cooling-quenching
of the thermal treatment product for fixing a metastable structure; increasing productivity;
decreasing power consumption.
The above problems are solved by using the method of pulse
heat treatment of bulk materials including feeding, distribution and movement along
a heated surface of initial material with particles being in relative displacement
and contact; discharge of the finished product in a storage reservoir. After feeding
the initial material is mixed and at the same time heated, then it is metered, evenly
distributed and moved along rotating surface heated to 100-1500°C, superheated
vapor is bled off, and at the moment of leaving the heated surface the product is
Relative movement of the material and contacts of the particle
with then heated surface are due to centrifugal force, and the time of the contact
and the force of pressing material against the heated surface are controlled by
the speed of rotation. Heating of the initial material particles is due to heat
transfer during the contact with the plate. In addition to gravity the compression
of particles due to the centrifugal force increases the tightness of their contact
with the operative heated surface of the plate and enhances the heat transfer process.
Such method of heating provides for increased speed of particle relative movements
thereby increasing productivity of the process.
Quenching at the moment when product leaves the heated
surface is provided by contact with cooled side surface of the device. The product
is cooled to a temperature of at most 150°C for not more than 5 s. The process
of heating-quenching takes 0.5 to 5.0 s. Vapor is extracted in the plate zone at
a maximum pressure of superheated vapor. For metering bulk material the metering
gap area is controlled. In metering the flow rate of the bulk material remains constant
when the number of plate turns is changed.
Objectives according to the closest prior art are achieved
by using a device for pulse heat treatment of bulk materials, the device comprising
a vertical shaft with a drive and attached plate mounted in a housing; a tank for
an initial material with a flow rate regulator in the lower part; a storage enclosure.
The device is equipped with heaters, a superheated steam evacuation system, a cooling-quenching
system for the products of pulse heat treatment, wherein the operational (upper)
surface of the plate is conical or has a curvature providing upward widening.
The plate heater can be placed on the plate or above it.
The heat sources are electric heaters, gas or other fuel burners. The heater is
secured in thermally insulated base of the device housing. The upper part of the
thermally insulated housing of the device is designed to be displaced in axial direction
forms a slot with the operational surface of the plate; said slot transforms into
a cooling zone. The cooling zone for the product of pulse heat treatment is a cavity
defined by the side housing and the bottom surfaces of the device. The side housing
and the bottom surfaces are subjected to forced cooling. The cooling zone is connected
with the inside of the storage for collecting product. The side surface of the device
housing is conical or has another shape narrowing downwards. Initial material flow
rate regulator is a movable in axial direction bushing interacting with conical
(or of another shape) portion extending in the feeding surface of the plate. The
storage for the initial bulk material is equipped with a heater. The slot between
the plate and the upper part of the housing is connected with the cavities for evacuated
superheated vapor and for heating the storage for initial product.
The axial moves of the flow rate regulator between the
bushing lower end and a conical part of the vertical shaft allows controlling bulk
material flow rate.
The side surface of the bottom and the side surface of
the housing define the cooling cavity and they are provided with a system of cooling
liquid supply. The cooling cavity transforms into a conical cavity of the product
The known solution has the following disadvantages: low
effectiveness of impulse heat treatment of bulk materials due to complicated configuration
of the heat carrier (the plate) which does not provide for uniform distribution
of treated material on the heated surface. Moreover, the known device is highly
inertial in terms of heating/cooling. In case of heavy thermal insulation of the
housing and a large size of the plate (a diameter of 1 m and thickness of 1 cm),
the time required for heating from 20 to 300°C is about 1 hour when the power
of heaters is 50 kW. In case of halting operations of the device according to the
prior art it can be opened only after cooling the plate for a few hours. What is
more during the process of heating/cooling the plate must continue rotation to avoid
Summary of the Invention
It is an object of the present invention to solve the problem
of enhancing effectiveness of bulk material pulse heat treatment.
The present invention offers a method for pulse heat treatment
of powdered bulk materials practically free of the disadvantages of the closest
prior art and other analogues due to optimal method of treatment with the same result
but at lower temperatures allowing the use of a wide range of high-temperature and
corrosion-resistant materials for the rotating heated surface and of centrifugal
activator of simple design. What is more, it becomes possible to treat in one step
both dry and wet bulk materials. It makes the treatment method economical and competitive.
As the treatment process for wet materials is more complex than for dry materials,
further description is focused on processing wet materials. The method and device
for treatment of dry material are similar but the method is simpler and carried
out according to specially selected modes.
Description of the drawings
Detailed Description of the invention
- Fig.1 - A device for pulse heat treatment of bulk materials
The object is accomplished by using the claimed method
and device for implementing thereof.
The method of pulse heat treatment of bulk materials comprises
the following steps: evaporation surface moisture; fast heating to a required temperature
and consequent cooling with simultaneous feeding particles on a rotating surface
heated to a temperature above 100°C, contacting particles with the heated surface
under the action of centrifugal force wherein the contacting time and pressure of
the particles against the surface are controlled by changing the speed of rotation;
and the step of quenching particles on the surface of a cooler by fast cooling an
then collecting the finished product in the storage.
Treatment of moving bulk material particles is carried
out on the surface of a truncated cone or a cylinder rotating around a vertical
axis, and the steps of vaporization and heating to a required temperature are combined.
Time of motion of the material on the heated surface under gravity is controlled
by the friction force and the friction force is controlled by changing the speed
A bulk material having moisture content of 5.0 wt% is fed
in the form of extrusion granules. The process of pulse heat treatment is carried
out on the inner surface of a dram having the shape of a vertically rotating cylinder
or a truncated cone, and the material is fed from above. The time of treated material
movement on the rotating heated surface increases when the speed of rotation is
increased. Under the condition that the time of contact is predetermined the productivity
of the activator is increased if the diameter of the drum is increased and the speed
of rotation is decreased. Depending on the drum diameter selected for determined
productivity the initial material is fed on one or a few sectors of a distributing
ring from above. The number of sectors depends on the area of distribution along
the surface of the drum without overlapping of the distribution areas. The quenching
step is carried out on the surface of the cooler located below the drum by rapid
cooling in not more than 3 s to a temperature not higher than 150°C. Total
treatment time at all steps is not less that Is.
A method of pulse heat treatment of powdered bulk materials
comprises: feeding wet material with moisture content of up to 20 wt%, removal of
surface moisture from particles with simultaneous heat pulse on the rotating surface
heated to a temperature higher than 100°C; consequent rapid quenching by cooling
to a temperature not higher than 150°C for not longer than 3 s, and collecting
the finished product in a storage. There are the following requirements for conducting
the steps of this method:
- 1. The wet material is fed in the form of not very strong microgranules having
a diameter of up to 3 mm produced by any known process (for example, by extrusion
on a screw type extruder). The granules moves along a groove in the mode of broken
flow (to avoid blockage due to hang-ups) to the heated rotating surface.
- 2. Contact of wet granules with the surface heated to 600-700°C results
in their immediate heating and breakage by vapor of moisture evaporating from the
surface of the particles since the bonds (adhesion) between particles in granules
is not strong. Tests has shown that for breaking granules having a diameter of up
to 3 mm it is enough to let them fall from the groove arranged at some height on
the heated rotating surface. The duration of evaporation and heat pulse is about
Thus this process provides for continuous treatment of wet material in one step
with the heat pulse.
- 3. In the claimed method as well as in the closest prior art the basic part
is treatment of particles on a rotating heated surface in the field of action of
gravitational and centrifugal forces but the difference of the claimed method is
in that gravitational forces have determining influence on the particle movements
along the heated surface and centrifugal forces provide for creation of friction
on the surface, and friction controls the speed of powder motion, i.e. it controls
the time of contacts. The weight of powder material does not depend on the shape
of contact surfaces, and centrifugal forces always acting in one direction perpendicular
to the axis of rotation are practically the same in such contacts. It means that
such resolution of forces can be achieved not on a horizontal surface but on a vertical
one in a shape of cylindrical drum of corresponding height feeding particles on
the inside surface from above. As the centrifugal forces are perpendicular to the
surface and commensurable with the particle weight, the force pressing them against
the drum and the speed of their sliding is easy to control changing the speed of
drum rotation, and the centrifugal force determining the time of particle contact
is constant for any cylindrical surface .
It is known that the formula of centrifugal force is Fc
= m&ohgr;2r where m is a particle mass, &ohgr; is
an angular velocity (turning speed) and r is a radius of drum circumference.
If values of Fc
and m are constant, an increase in r should be followed by a
decrease in &ohgr; = 2&pgr;n, i.e. a decrease in number of turns
n per unit of time.
Thus use of centrifugal force not contrary to gravitational force leads to a positive
result: with increase of the drum diameter and simultaneous decrease its speed of
rotation the action of the gravitational forces and centrifugal force on particles
remains the same. Therefore the productivity of centrifugal activators depends only
on the size of the drum and its number of turns: the bigger is drum diameter, the
lower is the number of turns. It is reasonably reliable solution for a design. It
also allows flexible control over the process for treatment of bulk materials with
wide range of parameters. Choice of drum size is limited by its surface area required
for heat transfer of determined amount of heat from heaters and their arrangement
in the drum of big size.
- 4. Material is fed uniformly on one or a few sectors (depending on the diameter
of the drum chosen for required productivity) in the upper part of the drum. If
there are a few places of supply, each particle flow slides on the surface along
a helical curve and scatters along the surface of the quenching cooler in sectors
of certain length when leaving the edge of the drum. There should be no overlapping
of these sectors if there is no overlapping when dissipating along the drum surface.
It determines the number of points for powder feed at the beginning.
- 5. The design of the drum is very simple and can be produced from thin sheets
quick to be heated (it is important at start of an activator) and cooled down at
stops. Material for the dram can be any heat-resistant stainless steel. A drum can
be quickly replaced when worn-out.
- 6. After leaving the hot surface the material is quenched due to contact with
the surface of a cooler. Cooling is controlled by regulating supply of a refrigerant.
The product is cooled to a temperature not higher than 150°C in not more than
- 7. The complete process of evaporating-heating-quenching of bulk material particle
is carried out in the wide range of time. It can be a short-time treatment for 0.5-1.0
s as well as longer one for more than 1 s. Temperature is controlled by zones with
the help of thermocouples placed in zones of the heater, product storage, inlet
and outlet of refrigerant and outlet of vapor.
The inventive method is implemented using a device, a centrifugal
activator, for pulse heat treatment of bulk materials. The device comprises a vertical
console shaft arranged in a housing with a remote electric drive for its rotation,
one end on the shaft is mounted in a housing cover in cooled bearing box; one or
more ducts for feeding the initial material on the rotating surface; a surface for
pulse heat treatment in the shape of vertical cylindrical or conical drum; a unit
of cooling-quenching the product after pulse heat treatment; and a storage unit
for the product. The activator is equipped with heaters of the drum and a unit for
discharging superheated vapor.
The heater can be arranged outside and/or inside the drum.
Electric heaters in heat-insulating housings are used. The unit of cooling-quenching
the product is a cylindrical quenching cooler consisting of one or more cooling
chambers with individual control of refrigerant supply in each chamber. The storage
unit is an extension of the cooler body with an annular slot of 3-5 mm between them
for avoiding heat transfer between the housings of the cooler and the storage. If
such slot is not arranged, the storage upper part can be cooled resulting in particle
sticking to it. The storage has a distribution ring arranged outside with openings
into its zone.
The method for treatment of bulk materials is realized
in the device, the centrifugal activator, shown on Figure 1 for two variants of
the design: one with a conical rotatable drum 8 shown to the left from the axis,
and the other with a cylindrical drum 6 shown to the right. The activator comprises
body 1 with removable cover 2, quenching cooler 3, storage 4 with locking means
5 of a gate type, cylindrical rotatable drum 6 with conical collar 7 or conical
drum 8 with electric heaters 9 mounted outside and/or inside (shown in a dotted
line) of the drums. Electrically driven (not shown in the Figure) shaft 11 is fixed
in cooled bearing housing 10, the housing is mounted on activator. At the lower
end of shaft 11 distribution ring 14 is arranged on hub 12 with the help of ribs
13. There is gap 15 between drum 6, 8 and ring 14. The bulk material fed through
duct 16 having cover 17 to distribution ring 14 is thrown to rotatable drum 6, 8
through gap 15. Quenching cooler 3 consisting of a few chambers separated by solid
partitions (one chamber is shown in the Figure) is mounted under drum 6, 8 with
the electric heaters. Each chamber has an inlet and outlet for the refrigerant.
The cooler is protected by metal screen 18 from inside. The screen is arranged with
gap 19 of 5-7 mm for free sliding of particles on the surface of cooler 3. Storage
4 is located below cooler 3 so that there is gap 20 between them. The storage is
fixed to the cooler by ribs. Distribution collector 21 with openings 22 and air
inlets is provided at the outer side of the storage. The holes are protected by
shield 23. Detachable packaging 24 (a polyethylene bad, etc.) is fixed to the storage
and placed on floor scales 25. There is outlet tube 26 in the upper part of housing
1 for discharging overheated vapor equipped with a ventilator. Opposite to it there
is inlet tube 27 with controllable gate 28 for supplying air to shaft 11 for its
additional cooling. Housing 1 has thermal insulation 29, cover 2 has thermal insulation
30 and storage 4 has thermal insulation 31.
The device is operated in the following way.
At first a refrigerant is filled in quenching cooler 3
and in bearing housing 10 and fix packaging 24 from the bottom. Then drum 6, 8 is
heated by electric heaters 9 to predetermined temperature. At the next step the
drive of shaft 11 is switched on, the ventilator at the vapor outlet is switched
on, and granules of wet bulk material flow is directed through duct 26 to rotating
distribution ring 14. Under the action of centrifugal force the particles of the
bulk material are pressed to the inner surface of the drum and move downwards in
rotational-translational motion along a trajectory of a helical curve. The particles
are under the action of a vertical gravitational force and friction force controlled
by a centrifugal force (a number of turns). The frictional force determines the
speed of particle sliding along the surface thereby providing predetermined time
of contact. When leaving the drum lower edge, the powder retains its acquired circumferential
component of speed and falls on the conical surface of quenched cooler 3. Wet vapor
escaping from particles is removed through the central opening of distribution ring
14 and further through outlet tube 26.
The material further slides along the surface of cooler
3 at a temperature controlled by refrigerant supply and cools to a required temperature.
The zone of storage 4 is a continuation of the zone of
cooler 3. There is gap 20 (3-5 mm) between the zones for preventing cooling of the
storage upper part from the cooler and particle sticking in the zone. Then the product
accumulates in storage 4 on gate 5 (closed) and eventually poured into packaging
24. After the packaging is filled to certain weight fixed by floor scales 25, storage
4 is closed with gate 5 while the packaging is replaced.
Outside air is supplied through inlet tube 27 for additional
cooling of shaft 11 (basic cooling is in housing 10). The air is either removed
by the vapor ventilator or forced in case vapor is evacuated through a hood depending
on the mode of operation.
During operation in some modes dry air for partial ventilation
of the inner part of the activator is supplied through openings 22 in distribution
Further the invention is illustrated with the following
Example 1. A wet powder of technical alumina hydrate Al(OH3) (mudstone)
comprising particles having sizes between 0-150 µm and moisture of 17 wt% after
being discharge from a screw extruder in the form of granules of 2-3 mm is continuously
fed along an inclined groove in the rotating drum of 200 mm in diameter heated to
a temperature of 650°C ± 10°C. The powder is fed in one point of
the distribution ring in the amount of 5 kg/h. The gap between the drum and the
distribution ring is 5 mm. The speed of rotation is determined experimentally at
90 rev/min providing for the contact of the powder with the drum operational surface
for about 1 s. The flow rate of water in the cooling system of the quenching cooler
is 150 1/h, 50 1/h per each chamber. Power consumption of the device is 6.8 kW.
After cooling the powder passes into a storage bin. The amount of the activated
product in the storage bin is 4.2 kg after one hour of operation. X-ray phase analysis
shows that the product of the heat treatment has an amorphous structure and enhanced
reactivity revealed by a speed of dissolving in an alkali that is 5 times higher
that for the initial substance. The initial substance - aluminum (III) hydroxide
- is present in the product in the amount less than 5%.
Example 2. Example 2 is similar to Example 1. The difference is only in that
a preliminary dried non-granulated powder of mudstone is treated. The gap between
the ring and the drum is 2 mm. The result of the heat treatment of the particles
is the same as in Example 1, and the initial substance is present in the product
in the amount not more than 3%.