Note: Descriptions are shown in the official language in which they were submitted.
~0~4S
SUPPRESSION OF POLLUTION
IN MINERAL FIBER MANUFACTURE
In considering the following description it is
to be kept in mind that certain portions of the subject
matter disclosed are also disclosed and claimed in the
companion application Serial No. 210,777 of Marcel Levecque
and Jean A. Battigelli, filed October 4, 1974.
The present invention is concerned with a process,
and the devices for implementing it, which assures the sup-
pression of harmful factors and permits the elimination
of at least the majority of the ecologically objectionable
pollutant elements-- noxious or undesirable due to their
toxicity, their odor, and their opaqueness--contained in
the gas or liquid wastes discarded by installations manu-
facturing mineral fibers.
The invention is of particular use in installations
for the manufacturing of fiber blanket, mat padding, or
boards of mineral fibers and especially glass, agglomerated
by thermosetting or thermoplastic binders, which coat the
fibers and/or bring about close binding between fibers in
the finished product.
The binders commonly used in this type of manufac-
turing have a base consisting of pure or modified phenoplast
or aminoplast resins, since these present advantageous charac-
teristics for the manufacturing of agglomerated fibrous
products. They are thermohardenable, soluble or emulsifiable
in water, they adhere well to the fibers, and are relatively
low in cost.
.. . . .
. .
:1069~S
Generally, these binding agents are used dissolved
or dispersed in water to which certain ingredients are added,
in order to form the binder which is sprayed on the fibers.
Under the effect of the heat to which they are
subjected during the fiber products manufacturing processes,
these binders release toxic volatile elements having a per-
ceptible pungent odor even at very weak concentrations,
such as phenol, formaldehyde, urea, ammonia, and decomposi-
tion products of organic materials.
Other binders are used for certain applications
due to their very low cost. Certain extract of natural
products are hardened by drying and cross linking, such
as occurs with linseed oil upon oxidation. Others are thermo-
plastic, as for example bitumen. During the fiber binding
process, they are all, at least to some exten~, increased
in temperature and to a temperature sufficient to cause
the release of volatile elements, noxious or otherwise un-
desirable, among other reasons, due to their odor.
In the text below, the word "binder" will be used
to designate any one or all of the binding products mentioned
above, whether they are used in liqu~d form, dissolved or
suspended in water or in other liquid, or in an emulsion.
In a fiberizing plant, it is in the fiber collect-
ing or ~orming section that large quantities of gases and
water have contact with the binder which contains the pollu-
tant elements, and are contaminated according to a pollution
,,~3 , .. .
- , ..
.: . , .
. , . . - -,: . .
- - .
. . .
~ 5 ~-~
process which is common to all known processes for the manu- ~ -
facture of blankets, mats, or boards of fibers agglomerated
by a binder, and which will now be described.
a) The pollution of the gaseous effluents takes ~-
place according to the following process:
'.,' .; '
The binder is projected into the current made
up of fibers and gases, coming from the fiber production
apparatus, the binder being present in the form of clouds
of fine droplets. Some of this binder is entrapped by the
fibers, some is unavoidably deposited on the walls of the
installation, and finally some is found in the gases or
fumes in the form of fine droplets and in the form of vapor.
Thus two fluid contamination modes coexist, the
one consisting of contamination by droplets of the binder
and the other consisting of contamination by vapors of the
binder. In the binder application, the binder atomization
or dispersion devices used furnish particles or droplets
within a very wide range of diameters. The finest droplets
are not entrapped by the fibers and are drawn through the
blanket being formed by the gaseous current, in which they
are present in suspension.
The droplets of binder deposited on the fibers
during the binder application are subjected to the kinetic
effects of the gaseous current passing through the blanket
being formed. A large quantity of droplets is extracted
from the fibers, migrates through the blanket, and is found
' :, ' -. ' '............ . . :
.
. .. ,.. ' .
10~6~:~s
in suspension in the exhausted gases.
Finally, the desire to obtain a homogeneous distri-
bution of the binder in the blanket makes it necessary to
disperse the binder in the fiber and gaseous current in
an area situated near the fiber production apparatus, where
this current still has a well-defined geometric form but
where its temperature may still be high enough so that some
of the binder, or at least its most volatile components,
are evaporated. These pollutant vapors mix with the gases
and contaminate them.
In the text below, the word "fumes" will be used
to designate the gaseous effluents which pass through the
fiber blanket and are evacuated outside of the collecting
unit, i.e., the gases used for attenuating or guiding the
fibers, the fluids induced by these gases, and the pollutant
elements in the form of droplets or vapor suspended in these
fluids. It is to be understood that various features of
the invention, such as treatment steps and components of
the apparatus, may be employed with "fumes" having a wide
2~ range of compositions and pollutants. It is preferred to
treat all components of such fumes, but various features
of the invention may also be employed with gases originating
in fiber production operations in which the gases have pol-
lutant components, whether or not the pollutants have their
origins in fiber binders.
b) The functions performed by the water in a
fiber collecting unit make a large degree of pollution in-
evitable in any installation in which binders are used.
_4_
.
, . , . . . -:
. . -- ~
- . . . :,, , ~ . . . :
,. . . ~. ..
.
.
.
~0696~S ~:
:, .
In operation, water is used:
--(1) to dilute and carry the binder when the
latter is used in liquid form;
--(2) to wash or scrub the fumes, an operation
which consists:
--(2a) of causing the largest possible `
amount of pollutants contained in the fumes in the form
of droplets or vapor to be captured by the droplets of the
scrubbing water, thus causing the pollutant charge of the
fumes to be transferred to the wash water;
- (2b) of capturing and entraining on the
walls of the collecting unit the fibers suspended in the
fumes;
--(3) to wash the different parts of the collecting
installation (perforated belt, fume flues, etc.) in order
to evacuate the binder and the fibers deposited therein.
During these operations the wash water is charged
with binder components which are soluble, insoluble or in
the vapor state, and the concentration of pollutant elements
may reach hiyh values.
It is an object of the invention to render insoluble
the thermohardenable resins contained in the water. These
resins are rendered insoluble, according to the invention,
by means of a heat treatment--preferably at a temperature
greater than 100 C., and more advantageously ranging between
approximately 150 and 240 C., and under pressure.
~ he application of the above process (for render-
ing resins insoluble) to at least some of the cooling and
washing water is advantageously used to render insoluble
--5--
~''' .
' . , ' ' : ', ~ ' . ' ~
.
. :
10696~
the dissolved binder components contained in the water, in
order to subsequently be able--by means of known techniques--
to extract insoluable materials and thus to maintain the
concentrations of the pollutant constituents in the washing
and cooling waters at a level compatible with the continuous
re-utilization of these waters in the installation. The wash
water thus circulates in a closed circuit and any external
rejection of pollutants with the wash water is eliminated.
In summary of the above, therefore, the present
invention provides a method for separating water soluble but
heat insolubilizable resin constituents from an aqueous solution
thereof, which method comprises insolubilizing the constituents
by heating the solution to a temperature between about 150C.
and about 240C., at an absolute pressure of from about 6 to
about 40 bars, and thereafter separating the insolubilized
constituents from ~he water.
The above method may be carried out in apparatus for
separating heat hardenable resin constituents from an aqueous
solution thereo~, comprising pressuriæed treatment equipment
for heating the solution to a temperature sufficient to
insolubilize the constituents and for maintaining the solution
heated and under superatmospheric pressure for a time suf~icient
to effect such insolubilization, the treatment equipment
comprising a batch treatment vessel having means for heating
the interior of a batch of the solution therein and having
means for cooling the walls of the vessel during the heating,
the pressurized treating equipment having an inlet for receiving
pressurized solution to be treated and having an outlet for
discharge of treated solution at atmospheric pressure, a supply
source for solution to be treated, means connecting the supply
source with the inlet including means for preheating the solution
being supplied, and means recei~ing the treated solution
ywl/~ 6 -
. . - . . - ,- - - . ~ .
. ~ . ; . - . . . . .
- .
`" 10~i96~S
discharged from the outlet and for separating the insolubilized ~ `
constituents from the heat treated solution at atmospheric
pressure.
The drawings illustrate the general arrangement of
fiber production installations and also several preferred
embodiments of equipment according to the invention adapted
to be used in such installations, all of the figures being
at least in part diagrammatic and in general showing elevàtional
or vertical sectional views.
Figure 1 shows a fiber collection installation of
the general kind to which the equipment according to the
present invention is applicable.
Figure ~ depicts the evolution of the efficiency
level for the insolubilization treatment based on treatment
temperatures and times.
Figure 3 shows a set-up providing for batch treatment
of wash waters by heating under pressure, as is contemplated
by the invention.
~3 '
. .
ywl/~14~ - 6a -
10~ s
Figure 4 shows a set-up in continuous operation
for treating the waters.
In Figure 1 the installation comprises a fiber
production device, represented by 11, for instance of a
known type such as is ordinarily used in installations
for the manufacturing of agglomerated or bonded fibrous
blankets, panels or boards, in which the material to be
attenuated is subjected to the action of a centrifugal or
àerodynamic force, or to a combination of the two. The
aerodynamic force is applied to the material to be attenuat-
ed or to the fibers by means of gaseous jets which are gene-
rally at a high temperature and high speed. An example
of such equipment is shown in Levecque U.S. Patent No.
3,285,723. The fibers produced leave device 11, dispersed
in a current 12 of fluids generally in the gaseous state
formed by high-energy jets and the air or other gases which
they induce from the surrounding medium, a current which
envelops the fibers and directs them, in the form of a stream
with fairly well-defined contours, towards the collection
device.
The equipment further includes a zone for application
of binder, placed in the path of the fiber and gas current,
between the fiber production device 11 and the collection
device, in which atomizers 13 disperse the binder, in the
state of a cloud made up of fine droplets, into the fiber
and gas current. A large proportion of these droplets in-
tercepts the fibers and clings to them, the remainder being
present in suspension in the gases accompanying the fibers ~ -
either in the form of droplets or in the form of vapors.
. .
~ ~ ~7~
lO~9f~S
A fiber distribution device which may be any one
of several known types, indicated diagrammatically at 14,
placed in the path of the fibers and the gases 12, either
between the production device 11 and the binder application
zone or between the binder application zone and the forming
section, as is shown in Figure 1, which by imparting an
oscillating movement to the current of fibers and gas or
by deforming this current, makes it possible to distribute
the fibers on the collection surface so as to form a blanket
whose weight per unit of area is essentially uniform.
The collection surface is provided by an endless
perforated belt 15, on which the fibers accumulate to form
the blanket 23.
A chamber 16, placed beneath the perforated belt,
in the area where the fibers are deposited and the blanket
or mat is formed, i.e. the forming zone or section, and
in which a pressure reduction or negative pressure created
by a fan 19 causes all of the gases accompanying the fibers
along their path between production device 11 and perforated
belt 15 to traverse the blanket being formed, so that no
fluid in the gaseous state is entrained with the fibers,
outside of the area where the blanket is formed.
Vertical walls 21, which extend from the perforated
belt 15 to a level near the fiber production device 11,
and which mark off the area where the blanket is formed,
define a section or chamber 22, surrounding the current
of fibers and gas, open at its upper end, in an area near
the fiber production device. This is commonly designated
as the forming "hood".
$ ~ -8-
106~;45
The fan 19, provides a negative pressure in chamber
16 sufficient to force all of the gases accompanying the
fibers (as they are being deposited in the forming section)
through the blanket being formed, and evacuates the fumes
for recirculation as is described below.
In Figure 1, the upper part of receiving chamber
22 is closed by a cover 32 containing an orifice through
which current 12 of fibers and accompanying gases coming
from fiberization device 11 penetrates forming section 22.
The edges 33 of this orifice are tangential to current 12
and are of such a profile as to facilitate passage of the
above-mentioned current.
For the sake of operating convenience, cover 32
may be placed at a distance H from fiberization device ll.
The set-up of Figure 1 consists of a washing chamber
17, placed dow~stream from the suction chamber 16 and generally
larger in section than the latter, chamber, equipped with
apparatus in which fumes 29--i.e., the gases accompanying
the fibers between production device 11 and collection belt
15, and the pollutants in suspension--are placed in contact
with a washing fluid, in particular water. In this washing
chamber 17, the fumes are separated from a portion of the
elements that they contain in suspension--the latter elements
essentially consisting of fibers and the binder with which
they are charged upon passing through the zone where binder
is applied and the fiber blanket is formed. In contact
with the washing water, the fibers contained in the fumes
.. . . .. .. .. . .. - .
lQ6964S
retain droplets of water and subsequently have a tendency to
be deposited by gravity on the bottom of chamber 17, this
phenomenon being moreover accelerated by the abrupt reduction
in speed of the fumes as a result of the variation in the
flow section along their path of travel from chamber 16
to chamber 17. Some of the droplets or pollutant vapors
are intercepted by the droplets of washing water, and are
dissolved by this water. It is the functioning of these
two operations together which constitutes the washing of
the fumes. The water which was used for washing, and to
which at least some of the pollutant charge of the fumes
was transferred, is discharged through orifice 24.
This set-up also contains a separation system
18, of the cyclone or electrostatic type, placed between
washing chamber 17 and the suction fan 19, in which the
fumes are at least partially stripped of the water droplets
with which they are charged during the washing operation,
and which it is important to eliminate before entering fan
19. The washing water extracted from the fumes in the liquid
form is evacuated from the separation system through orifice
25.
A collector 26 leads the washing water evacuated
through orifices 24 and 25 towards the treatment zone.
As above mentioned, the current of fibers and
gases passes the binder devices 13 and then fiber distribution
device 14. The fibers are deposited on collection belt
15 and the fumes 29 ~ass through the fiber blanket 23 being
--10--
~ j~ .!,
. ', ' . ' . .. . ' ' ' , . ' . ' ,,
1o6964s : :
formed, through chambers 16, and through water separating
unit 18, and are driven upwards by a fan 19 into duct 34.
Some of these fumes are evacuated from the system through
orifice 35. The rest are led through duct 34 towards form-
.. . . .
ing section 22, into which they enter through an opening36 placed in a zone situated near the fiber production device
11.
The quantity of gas entering the forming section
through opening 33 is equal to the sum of the quantity
of gas coming from production device 11 and the quantity
of air induced by the latter as they pass in the open air,
along the length H. The quantity of gas entering the chamber
therefore increases with the length H.
For the system to be in equilibrium, it is necessary .::
that the quantity of fumes evacuated from the system through
discharge orifice 35 be equal to the quantity of gas entering
the system through orifice 33. The quantity of fumes to
be evacuated will thus decrease when the distance H is reduced.
In the installations built according to that repre-
sented in Figure 1, the recycled quantities of gases correspondto the quantities induced by the jets coming from device
11, and this ~low of the fluids through the section 22 will
take place in the direction of flow of the attenuating jets,
and therefore in the absence of disturbing eddies. The
recycled fumes essentially follow the current lines repre-
sented by arrows 37.
-11- :
.
.. .. . . . . . .
~06~
Provision may be made for treating the fumes
evacuated through orifice 35 by burning, an operation which
consists of heating the fumes to a temperature sufficient
to burn organic components, preferably greater than
600 C.--beyond which the pollutants of the fumes, and especially
the phenol compounds, are transformed by combustion into
non-pollutant elements, such as CO2 and H20. This treatment
also has the advantage of destroying odors. AS shown in
Figure 1, the burning procedure takes place in device 38,
of a known type, consisting of a combustion chamber 39,
a burner 40 supplied with a combustible mixture, and pro-
vided with a grid or any other flame stabilization device
41. The treatment temperature may be reduced to a value
ranging between 300 and 400C. in the presence of a com-
bustion catalyst.
The purified fumes are discharged to the atmospherethrough stack 42. At the outlet of stack 42, the temperature
of the fumes is high enough, and due to recycling their
output is small enough, so that the steam contained in these
fumes is not condensed before total dilution of the fumes
in the atmosphere. Thus no cloudy plume appears at the
outlet of stack 42.
In the installations represented in Figure 1,
since the small volume of fumes evacuated to the atmosphere
only eliminates a very small quantity of heat, means are
provided for cooling the forming section 22.
-12-
~ ' .
....
- . . . . . - . , . :
~O~ S
In the arrangement represented in Figure 1, atomizers
45 disperse cooling water in the form of sheets or curtains
of fine droplets, these sheets being generally perpendicular
to the direction of flow of fumes as indicated at 29. Once
the fumes have traversed the fiber blanket being formed,
they enter chamber 16 at a temperature on the order of from
80 to 100C. and are cooled by contact with the sheets
of water to a temperature on the order of 30 C. The tem-
perature of the water at the entrance to atomizers 45 is
on the order of 15 to 20 C., according to the capability
of the cooling devices serving to supply the atomizers.
By contact with the fumes, the water is reheated to a tempera-
ture on the order of 30 to 40 C., according to the flow
rate through the atomizers 45.
The recycled part of the cooled fumes, after passing
through separating device 18 and fan 19, reenters forming
section 22 where, by mixing with the gases from fiber pro- -
duction device 11, the recycled fumes cool these gases and
the fibers.
It is also contemplated to directly cool the current
12 of fibers and gas by projecting water on it, and dis-
charging this water outside of forming section 22 to thereby
remove the heat brought in by the materials to be fiberized
and the attenuating or guiding fluids. The projection of
water on the current thus takes place in the zone where
the contact surfaces cannot be very large since the available
space is small, but where the temperature differential between
the fluid to be cooled and the cooling fluid is large.
-13-
~,,,: - '
~06~64~i
For example in the embodiment represented in Figure 1,
atomizers 49, placed between fiber production device 11
and binder devices 13, project a cloud of fine droplets
of water against the attenuated fibers and gases of the
current to be cooled.
The droplets reach the current of gas and fibers
in a zone where this current is at a high temperature, which
may reach 600 C., and are immediately vaporized, thereby effect-
ing cooling at high efficiency. The large quantities of
heat--on the order of 650 to 700 Kcal per kg of water--nec-
essary to vaporize the droplets are taken from the current
of fibers and gas, which consequently undergoes a very rapid
cooling. This reduces the temperature of the current, at
the level of binder devices 13, to a value on the order
of 100 to 120 C. The vapor produced is evacuated with
the fumes, through fiber blanket 23, into chamber 16 and
washing chamber 17, where in contact with the curtain of
water sprays emitted by atomizers 45, the vapor condenses,
transferring its latent heat of vaporization to the cooling
water coming from atomizers 45. This heat is thus discharged
from the system along with the water from the atomizers -
45. :
The placement of the spray devices 49 for projecting
the cooling water against current 12, between fiber produc- :
tion device 11 and binder nozzles 13, is preferred since
in operation this arrangement has certain special advantages:
-14-
B~ ' . .
. .
-- , .
6~
First of all, it is in this zone that the tempera-
ture differential between the current to be cooled and the
water is the greatest and where the heat transfer is con-
sequently the highest.
The binder is then sprayed on a current of cooled
fibers and gases, at a temperature that is sufficiently
low (100 to 120 C.) so that breaking down of the binder -
due to volatilization of constituents thereof is very limited
or non-existent.
As a result, there is an increase in the binder
efficiency of the order of 5%, and a consequent reduction
in the pollution from the fumes.
The cooling water is discharged externally of
the installation by orifices 24 and 25 placed at low points
in chambers 16 and 17 and in water separating unit 18, into
device 51, in which the solid particles in suspension in
the water, notably fibers, are separated.
Device 51 may be either a filter, with meshes,
of a known rotating or vibrating type, or a decanter, or
a centrifuge, also of known type.
The water, free of suspended solid particles,
is collected in a tank 52 and the water is then directed,
by gravity or by means of a pump 53, into a cooling station
54. Upon leaving this station, the cooled water may be
discharged outside or reused in the system.
~ D -15-
. . ~ , . . .
... . .
106~964S
As shown in Figure 1, station 54 may include a
cooling tower 106, of known type, in which water is cooled
by contact with air. The cooling water is circulated through
the spray cooling tower by means of a pump 107. The water
from tank 52 is brought into indirect heat exchange relation
to the cooled water of the tower 54 by means of the heat
exchanger indicated at 105, from which the cooled water
may be returned to the tank 52. Make-up water may be intro-
duced as by the water supply connection indicated at 111.
It is preferred to cool the washing water by in-
direct heat exchange with the cooling water (or other cooling
fluid) circulating through the cooling tower 106, because
this completely avoids polluting the air with any remaining
volatile pollutants in the wash water, although the content
of such remaining pollutants in many installations is so
very low (for instance, less than 5% of the quantity discharged
by the gas offtake of a nonrecycled installation such as
shown in Figure 1) that it may be practicable to directly
cool the wash water in the spray cooling tower 106.
An advantage provided by the invention, is that
it is contemplated that no water in liquid state be discharged
outside of the installation, so as not to contaminate the
environment even by the small content of pollutants that
the water still contains.
-16- :
'' ,
,~,~
- . .
~0696~S
This implies that the water introduced through
nozzles 49 or 50 and the washing water circulate in a closed
circuit within the installation.
In installations represented by Figure 1, the
closed circuit of the cooling and washing water is the
following:
--The water leaving cooling station 54 is sent
via pump 55 to the cooling spray devices 49 situated in
chamber 22, and also to the vapor condensation devices and
fume washing devices placed in chamber 17, which include
the atomizers 45 as shown in Figure 1.
--The washing water and the condensed vapor, charged
with pollutants, fibers, and binder components, flow through
orifices 24 and 25 placed at low points in washing chamber
17 and water separator 18, into a collector 26 which leads
them towards filtration device 51; this separates solid
wastes 56 in suspension/ fibers, and insoluble binder com-
ponents from the washing water.
These wastes are collected on a conveyor 57.
Since the filtered washing water only contains dissolved
binder components and pollutants, it is sent by gravity .
or via pump 53 towards cooling station 54.
The applicants have observed that when the washing
water circulates in a closed circuit, it is necessary to
maintain the concentration of the materials dissolved or
-17-
106964~-
suspended in the filtered water below a certain value, this
being on the order of 3 to 4%--computed in unit of mass
of dry materials per unit of mass of water. Above this
value some of the materials dissolved or suspended in the
washing water (essentially microfibers or microparticles
of binder not captured by filtration device 51, and soluble
binder components) are deposited on different parts of the
installation. The binder is polymerized, forming viscous
or solid layers which progressively obstruct the washing
water ejection orifices 45, 49 and 50 and also the orifices
in collection belt 15 for the passage of fumes 29. As a
result, there is a reduction in the quantity of fumes evac-
uated from the hood and in the cooling of these fumes, soon
leading to shutdown of the installation.
In order to maintain the concentration of materials
carried in the water below the value which will obstruct
spraying or fume evacuation, it is necessary to extract
large quantities of materials from the washing water. In
operation, a large proportion, on the order of 20 to 30%
of the binder sprayed on the fibers by nozzles 13 ends up
in the washing water, in the manner already described.
For large plants, this makes it unavoidable that 3,000 to
5,000 kilograms of binder per day (counted in dry material)
will be introduced into the closed circuit for circulation
of the washing water, and it is necessary to extract from
the water quantities of binder identical to those introduced
in order to maintain the concentration at an equilibrium
value.
-18-
.
~' .
~ ~,~ ,..
, . .
~ g64~
According to the present invention this is done
as follows:
A small portion--on the order of 1 to 5%--of the
flow of washing water charged with dissolved binder circulat-
ing in the circuit, is heated so as to insolubilize thebinder, followed by separating the binder from the water
by any appropriate means of separation such as filtration,
flocculation, centrifuging...
~' , ''
In operation, the applicants have observed that
if the water used for cooling and washing of the fumes--
and thus, after filtration, containing the binder or dissolved
binder components--is maintained at a given temperature
for a given period of time, a proportion of the dissolved
binder increasing with the temperature and the time would
be transformed into insoluble particles and would subseq-
uently be found in suspension in the water and could then
be easily separated from the water.
The proportion of dissolved material--insolubilized
by the treatment--characterizes the efficiency of the treatment.
The treatment temperature has a very important
influence on the efficiency. For example, it has been found
that for a water containing 1% dissolved binder component,
the treatment efficiency is:
--19--
.....
.
., . ~ : .
.
~0696~
40% if the water is maintained at 40C. for
eight days;
40% if the water is maintained at 70C. for
three days;
40% if the water is maintained at 160C. for
three minutes;
60% if the water is maintained at 180C. for
three minutes;
95~ if the water is maintained at 240C. for
three minutes.
Figure 2 shows the evolution of the treatment
efficiency as a function of the temperature and of the treat-
ment time.
In large capacity plants manufacturing panels
of agglomerated fibers, since the quantities of water to
be treated may reach 50 m3/h, in order to avoid the installa-
tion of treatment plants of considerable dimensions, it
is necessary to determine the shortest treatment times and
thus to work at high temperatures, greater than 100 C.
This means carrying out the treatment in a pressurized chamber,
at a temperature maintained at approximately 5 C. below
the boiling temperature of water at the pressure of the
chamber, so that the water remains in the liquid phase through-
out the duration of treatment. This solution also has the
advantage o~ requiring only a small energy expenditure which,
with respect to the wastes, only corresponds to the increase
in heat imparted to the water in order to raise its tempera-
ture.
;:~, ~:
.,.. ~ . .
.:
,: .
. .
, . .
106964~i
One of the disadvantages ordinarily encountered
when heating in a chamber water containing the binder or
dissolved binder components, even in a weak concentration,
is that an insolubilized binder deposit forms on the walls
of the chamber which very quickly becomes thick enough to
obstruct the evacuation orifices of the chamber, or the
chamber itself.
The applicants have observed that if the heat
necessary for treatment is released in the water mass to
be treated and the wall of the chamber is maintained throughout
the treatment at a temperature less than that of the water
mass treated, there is no formation of deposit on the wall,
the insolubilized binder remaining in suspension in the water.
This leads to heating the water, either by mixing with hot
fluids such as steam that has preferably been superheated,
or with immersed burner combustion gases, or by means localizing
the energy in the midst of the water mass such as an electric
arc.
A wide range of operating conditions is possible,
for example 6 to 40 bars for the absolute pressures, from
150 to 240 C. for the temperatures, and from 3 to 10 minutes
for the treatment duration.
The following conditions are the result of a satis-
factory compromise between the energy cost and the equipment
maintenance cost:
~ ,
-21-
,~ . .
~,.
,
10~64S
--temperature: 2Q0 C.
--pressure : 16 bars absolute
--duration : 5 minutes
--efficiency : from 70 to 80%.
This method of treatment may be applied to a dis-
continuous operation set-up or to a continuous operation
set-up.
Figure 3 shows a discontinuous operation set-up
for the application of this treatment process. The water
to be treated is introduced to chamber 68 through motorized
valve 67. The quantity of water introduced, or the charge,
represents 70 to 80~ of the capacity of this chamber. The
heating fluid or vapor--preferably superheated--then penetrates
the chamber through injector 69, whose outlet orifice is
immersed. The quantity of vapor is regulated by motorized
valve 70, controlled by regulator 71.
The treatment cycle takes place as follows.
Chamber 68 contains a water charge to be treated
which is initially under atmospheric pressure.
The treatment pressure desired, for example 16
bars absolute, is recorded on regulator 71.
Valve 70 opens and the vapor flows through injector
69, mixes with the water to be treated, and upon condensing
transmits all of its latent and sensible heat to the water. -~
The temperature and the pressure in chamber 68 rise until
reaching approximately 200 C. and 16 bars absolute.
-22-
- , , -
~)6~6~S
The introduction of vapor is then terminated.
Injector 69 has been adjusted so that this temperature and
pressure rise is rapid, occurring in less than one minute.
"
The water is maintained at 200 C. and 16 bars
absolute for two to four minutes.
At the end of this period of time, a pump 72 is
put in operation in order to deliver through jacket 74 a ,
new charge of water to be treated, into a vat 73. As it
passes through the jacket the water to be treated--which
is at a temperature of approximately 40 C. at the entrance-
-initiates the cooling of the treated water contained in
chamber 68. The dimension of jacket 74 is adjusted so that
the water to be treated reaches vat 73 at a temperature
of approximately 80 C.
A supplementary cooling fluid circulates in the
jacket 75 and completes the cooling of the treated water
contained in chamber 68. This cooling is considered to
be completed when the temperature of the treated water drops
below 100 C., and preferably 40 to 50 C. At this moment,
a motorized valve 76 is progressively opened in order to
decompress chamber 68.
The treated water flows towards a filtration station
51, or a flocculation, decantation, or centrifuging device,
which separates the binder insolubilized by the treatment
from the treated water.
-23-
~'`'
' ' ' .
.,: - . ~ - .
.
.
106g 6 L/~ ~
The filtered water flows into vat 52 and the extract-
ed wastes 56 are delivered to a conveyor 57.
When chamber 68 is empty, valve 76 is closed and
valve 67 is opened, thus permitting the preheated charge
of water in vat 73 to flow by means of gravity into chamber
68. An exhaust 67a completes the installation.
A new cycle may be started again.
Figure 4 shows a continuous operation set-up for
the application of the treatment process.
A pump 77, under the treatment pressure, sends
the water to be treated to a mixer 78 in which an injector
79 is arranged, through which the heating fluid consisting
of steam is introduced. This steam mixes with the water
to be treated and, upon condensing, transmits its total
heat to this water. The steam flow is regulated by motorized
valve 80 controlled by regulator 81, in order to maintain
the desired treatment temperature at the outlet of mixer
78. Subsequent to leaving mixer 78 in which it has remained
for 10 seconds, the water to be treated passes through a
reactor 82, where insolubilization of the binder takes
place--the dimensions of which are adjusted so that the
retention time of the water to be treated corresponds to
the duration of treatment, for instance 2 to 4 minutes.
-24-
~ .
1o6g64~ . '
Subsequent to leaving the reactor, the water is
cooled in an exchanger 83, to a temperature less than 100
C., and preferably from 40 to 50 C. Some of this cooling
is provided by the water to be treated, which is thus preheated
in coil 84 from approximately 40 C. to approximately 80
C.
The rest of the cooling is provided by a cooling ~:
fluid circulating in coil 85.
Subsequent to leaving exchanger 83, the treated
and cooled water is decompressed to atmospheric pressure .
through a pressure-reducing valve 86 which, controlled by
a regulator 87, maintains the treatment pressure in the
installation.
The decompressed water flows towards a filtration
device 51, or a flocculation-decantation or centrifuging
device, which separates the binder insolubilized by the
treatment from the treated water. The filtered water flows
towards vat 52 and the wastes 56--residues of the treatment- :
-are delivered to a conveyor 57.
The set-up shown in Figure 4, of the continuous
operation type, permits a more flexible and less costly
treatment than that shown in Figure 3.
-25- ~ -
. d~ , .,
, ~, . .
.
