CA1036926A - Mixing apparatus and the uses thereof - Google Patents

Abstract

ABSTRACT
An apparatus for use in atomizating a combustible material into a form for improved combustion comprising (i) an atomization zone, (ii) an ante-chamber connecting with the atomization zone, (iii) at least tow feed inlets to the ante-chamber at least one being for a said combustible material at least one other for an auxiliary atomizing gas, and (iv) nozzle means at or in the immediate vicinity of the exit of the atomization none for modifying the profile of atomized material exiting from the zone;
and in which apparatus the atomization zone is of generally cylindrical cross-section and is provided internally with means which are adapted to impart to the streams of the combustible material and atomizing gas passing therethrough multiple shearing action and changes of rotational direction.

Description

This invention relates to the atomisation of certain combustible materials and also to their combustion thereafter.

The combustible materials envisaged in this invention are materials which are, or at a temperature up to 300C are, a gas, a liquid, a particulate solid,or a liquid containing particulatesolids, and are, or at said temperature are, pumpable or flowable.

Such materials,.for example ga~eous or liquid fuels, only burn com-p}etely if they are.mixed with the gas containing oxygen. Liquid fuel burners,include.eQsentially an atomiser. This atomiser i9 generally accommodated.in.the.burner head,.which i9 mounted.at the extremity of the body or tube of the.burner. -The,burner forms an integral part of a-~Dre or less comFlicated apparatu~ which includes suitable means for.
mixing,the,,atomi~ed.fuel with a gas containing oxygen and for producing the,..desired flame.

.. ....
The known,burners.~ake:u~e of three atomising processes, atomising.by an auxiliary fluid,.mechanical atomising by the pressure of the fuel and.,atomising by rotating cup. Some burners embody a combination of ~' thes,e processes.
,, . ..., ., ...., .: , .. . ..
Atomising.by an.auYiliary.gas,uses the enèrgy liberated by the ,, expansion.of,compre~set air or vapour.under pressure for dispersing,.
the,,fuel., This,dispersion is.produced by,the meeting of a jet of liquid,fuel and a jet of the auxiliary gas. The atomising obtained :,-' ~, ,' ~ - 2 -"

by this process,is very.coarse, above all in the case of the.~ore .
viscous fuels...~oreover~ the consumption of auxiliary.fluid i9 quite , considerable, genera}ly in excess of 10 kg vapour to 100 kg heavy fue~
oil. .Consumptions of 15 to 20 kg vapour per 100 kg heavy fuel oil are normal.

In a.burner with mecba~ical atomising by pressure,,the fuel i8 in3ected tangentially.into a cavity-within ~hich-it,performs,a rapid rotary:.
vement, while maving.towards rhe.orifice,of:the.burner. This...orifice.
i9 arranget in the centre of a cap which.cover~ the cavity.and.consti-tutes..the.burner.3et. .At the.outlet:of the 3et.or nozzle,.the ~et of .

liquid is in the_form of a.co~ical sheet.. Thi8 type of atomiser only ailo~s,variation~:in-delivery between -20 ant..t20~... Uariau~ improue-.
ments~.in particu}ar_the heavy oi}.-return burner and.the-touble.feet.
bùr~e~,,allow..greater:flexibility.in.operation;..in spite..of the compleYity of these burners..and of their supply.circuit, the..extreme deli~erie~ are at mo~t,in,the.-ratio,of.lO to l. All the.. mechanical .. .
atomiaing.bur~ers produce.drop}ets which,-are.larger the-more..uiscous the fuel. ,The aize,of the drops also.increases..~ith the..de~iuery..
The nQzzle, ~hich ic e~posed,to the:radiation..of:the flame..and the.
furnace, is frequently obstructet by the formation of coke.

Rotating,cup,burners are,far:less uset:than:r~e.pre~iou~.-ones. The cup~ which is,drisen-;by:compressed air or an electric motor, atomises the fuel by centrifuging.

103~;'9Z6 If the problems inherent in the use of liquid fuels, such as heavy fuel ails, have found satisfactory solutions from a technical point of view whereas from an economic point of view these solutions are not free from imperfections, the same cannot be said of the problem raised by the combustion of by-products that very much more viscous than the usual uel_oi~ contain suspended solid constituents. For instance, it is no~ possibIe with any known burner to atomise certain tars and make them burn properly. Either the burner is obstructed too quickly, or the atomising of the fuel is far too coarse.

The present invention has as one object the overcoming of this problem whereby it is possible to burn fuels of very different kinds, only requiring a moderate consumption of auxiliary fluid and having great flexibility of operation as regards both the delivery of the fuel and its physical state.

.
In prior proposals for atomising by an auxiliary gas, the energy released by the expansion of the latter is first of all used to form a jet of gas in which this energy is converted into kinetic energy.
Next, in the impact produced between the jet of gas and the jet of liqu-id fuel, a fraction of the kinetic energy of the two jets is used ta av~rcome the forces of cohesion of the liquid. The efficiency of this process is poor for the mere impact of the jets anly makes it p~s~ible to use a small fraction of the kinetic energy of the fluids t~-bring about the dispersion-of-the liquid. In othèr prior proposals, thc inieial jet oi the auxiliary gas is produced by only a partial ; - 4 -r~an~.ion r~f thi-. g-ls an~l th~ mix~ure formed by ~h~ meetiny of thc two j~ts undergoes a further partial oxpc~nsion or expan-siorls, bv ~assirlg ~hrouqh a nlrrow passaye or several succes-sive narrow passages, in which fresh divisions of the liquid ~lrops ar~ pLoduc~(l through shearirlg str-~sses. IIowever, the greater part of the energy liberated under these conditions by the expansion of the gas is dissipated in heat, so that with burners that are thus improved, the consumption of auxiliary gas remains very considerable. Moreover, highly viscous fuels rapidly choke this type of burner.
According to a broad aspect of the present invention, there is provided a process for the atomization of a flowable combustible material in an elongated atomization zone having an inlet and an outlet, comprising the steps of: ta) feeding in a substantially concentric and relatively independent feed relationship at least one stream of an auxiliary gas and at least one stream of said combustible material, under pressure, into said inlet of and through said elongated atomization zone and characterized by having substantially all of the pressure drop which occurs in said auxiliary gas and said combustible material in said atomization zone between said inlet and said outlet thereof, said feeding of said streams being characterized by said stream of combustible material being substantially non-atomized by said auxiliary gas stream prior to entry into said inlet of said atomization zone and said auxiliary gas and said combustible material streams being mixed substantially completely in said atomization zone, (b) expanding said auxiliary gas and simultaneously at spaced intervals along substantially the entire length of said zone splitting said gas and combustible material streams into partial streams and recombining said partial streams and changing the rotational direction of flow of said streams to i 10;~69Z6 produce an atomized combustlble material at said outlet, (c) regulating the relative ratio of feed of said auxiliary gas stream and said combustible material stream into the inlet of said zone so that at the outlet of said zone there is provided a substantially continuously atomized combustible material in-cludinq said auxiliary gas which occupies a substantially :~
`~1 greater volume than that occupied by said combusti~le material, and (d) passing the atomized combustible material from said atomization zone through nozzle means located adjacent said - 10 outlet of said zone and constraining said atomized combustible ~:
material into a predetermined profile. .
~s This prosess makes it possible, for example, to obtain a very fine ~ disperson of the liquid fuel, In this form, the stream of fuel can ~3 ~ ' ', ~ .

! ~:

:"~ ,' :' . ~ ': ' .:-~ 3 :

' :.' ' "' '`
. . .

,' ' - 5a - ;;

.

be-mixea very intimately with a stream of oxygen or gas containing oxygen. The result of this io. that the formation of unburnt matter can be greatly reduced or even avoided.

Th2re is no critical limit determinîng the minimum value of this ra-tio. The energy needed to disperse and propel a given delivery of liquid fuel i8 furnished by the expansion of the auxiliary gas în~ide the atomiser; it i9 equally possible to use a relatively small supply of auxiliary gas by injecting it at high pressure into an atomiser offering high resistance to the flow of fluids as it is on the:ather hand to use a larger delivery of auxiliary gas injected at lowEr ~res~urè-into an atomiser offering less resistance to the flow of fluids.

- . ~

For a given delivery of fuel, however, too small a supply of-auxiliary gas, even at initial pressure which is increased proportionately, may:le~d-either to the production of an emulsion in which the gas is the dispersed phase, or-to the production of a m;xed e~ulsion; in ei~he~:ca~e, this can lead to the production of an emulsion which does not mLx-satIsfactorily with the gas containing oxygen. As a general r~le-it:is possible:-to:obtain the results aimed at by-the invention by using deliveries of:auxiliary gas and fuel whose ratio is such that the-volume:occupIed by the gas-at the outlet of the mixer is at least 20 to 30 times-greater than that of the liquid, provided that the gas pres~ure at the inlet of the atomiser is sufficient.

,"

- 6 ~

10361~26 The delivery of liquid fuel ca~ be indefinitely small in relation to that of the auxiliary gas. Indeed, one af the advantages of the process is that the delivery of fuel can be reduced and made to approach zero, while maintaining.constan~ the approprlate pressure and therefore the delivery of gas to.the atamiser inlet. The atom-ising of a very small delivery of the fuel is excellent, and if the aùxiliary gas is compressed air, subsequent combustion of the atomised fuel is very satisfactory.

In-principle, there is no maximum or minimum limit as regards the pr-ess~res that can be used at the inlet of the atomiser. Indeed, the ne-ce8sary-pressure is linked, as has been explained above, to the deliv~ry of gas and to the characteristics of the mixer. To atomise a-give~-delivery of fuel, it is possible to use a pressure of about

2-b-ars, or-even less, at the inlet of the atomiser, provided that a rath~ large supply of auxiliary gas is used, with an atomiser offering-moderate resistance to the flow of the flu;ds. In practice, pre-s~res higher than 3 bars, and for preference higher than 5 bars, make it possible to atomise the fuel, using reasonable deliveries of auxiliary air. There is no upper limit as regards the pressures that can be used, but since the delivery of gas has to remain sufficiently high in relation to that of the fuel, there is no point in usi~g.e~tremely high pressures. It is-therefore reasonably possible to use a pressure between 3 and 20 bars. For preference, the auxiliary gas is taken to the atomiser inlet at a pressure of 5 rO 10 bar~.

- 7 _ -, :
.. .

l036æ6 For example, in order to burn a fuel that i5 as viscous, and even more ao-, a heavy fuel oil, it can be atomi~ed by using a delivery of auxIliary gas such that the volume occupied by the gas at the outlet of-th~.mixer is about 60 times as great as the volume of the liquid an~-by.in~ecting-the fuel and the auxiliary gas at a pressure of abaut 6 bars-at the inlet of the appropriate atomiser, such as one de~cribed hereafter, this atomiser delivering to a furnace at atmospheric pressure.

The auxiliary fluid is a gaseous substance at the pressure and temper-at~re.-at which it is used. The auxiliary gas i8 for preference compressed air or steam under pressure, but many other gases can be use~. .In particular, a fuel gas such as methane can be employed. Very low quantities can be used. For example, as little as 2 to 3 kg stea~ to atomise 100 kg heavy fuel oil.

.
For Freference, the pressure of the auxiliary gas at the inlet to the at~mi~4r, and therefore its-delivery, are largely constant. It is then poasible to alter the delivery of fuel by merely acting on its pressure at-the:inlet. The process-makes it possible to vary within hitherto unequalled proportions the delivery of atomised gas.

The-.iDsention.makes.-it.yassible.to.use several combustible materials simu-ltaneously or otherwise, with the same apparatus. It is undertood that the-cumbu~tible.material.can be heterogeneous and that it can cantain in suspension insoluble solid particles. An example of par-1036~;26 ticulate solids is pulverised coal. A slurry of pulverised coal canalso be employed.

An esp-~cially useful aspect of the invention lies in its opening up the posgibility of using heterogeneous or very viscous materials such as, for e~ample, viscous petroleum by-product tars, such as tars from a petroleum refinery steamcracking process.

Again the invention enables the disposal of sludges containing organic matér~als. The purification of urban effluents and certain industrial effluents as a rule comprises the separation of sludge containing organic materials. This sludge is eliminated by spreading or inciner-ation. Incineration is performed in special furnaces.

Rotary. fur~aces are regularly used with staggered combustion, in the ' upper ~tages-of which the drying of the sludge takes place. Some pyralysis of the organic materials is unavoidable, and ignition is very gradua-}. These-furnaces give off nauseating smoke, whose purification requirQs post-combustion.

The use af so-called fluidised bed furnaces is tending to become generalised, especially for the treatment of the waste water from petro~eum refinerie~. These furnaces have a number of advantages.
~ They have no inner partitiion or machinery. They do not emit gaseous ; organic compounds and combustion in them is complete. Nevertheless, , :, _ g _ 1036~Z6 the operstion of an incinerator of this type is delicate, the running costs are quite high and the calorific yield is poor.

The present invention makes it possible to incinerate sludge and makes-it possible to burn the organic matter contained in the sludge substantially completely. The invention makes it possible to incin-erate pu~pable sludges derived from industrial effluent, for instance, or from waste water from papermills, sugar refineries, petroleum refineries, etc. It may be derived from urban effluent. It i9 thus passible to-incinerate the sludge from sewage stations. The sludge can be very wet. Polluted water could even be incinerated directly by this process. It suffices to use a delivery of make-up fuel in rel~tion to the delivery and composition of the sludge. As make-up fuel, ~-gas or any pumpable liquid can be employed. It is possible to us~ natural gas, petroleum gas, a liquefied petroleum gas, a heavy fuel oil, etc.

In anather aspect-the-invention provides an apparatus for use in the afareaaid atomisation-and combustion processes, which apparatus com-prises in combination (i) an atomisation zone, (ii) an ante-chamber cannecting with the atomisation zone, (iii) at least two feed inlets to-the ante-chamber, at least one being for a said combustible material, at least one other for a said auxiliary gas, and (iv) means at or in the i;l, ediate vicinity of the exit of the atomisation zone for-modifying, in use; the profi~e of atomised material exiting from the zone; and in whi~h apparatus the atomisation zone is of generally cylindrical ~0369Z16 cross-section an~ is proviclcd internally with means ~hicil, by use of the apparatus, are adapted to impart to streams of fluids multiple shearing action and changes of rotational direction.

The preferred form of the atomisation zone or chamber is one employing one of the known stationary mixers, that is to say of the type consisting of a cylindrical tube in which are inserted appropriate fixed devices which have the effect of imparting to the fluids passing through the tube multiple shearings and changes of direction. One example of such a mixer is disclosed in U.S. Patent No. 3,286,992 issued on Nov.
22, 1966 to Armeniades et al.
The mixer may consist in partlcular of a tube in which a packing is inserted. This packing may consist of a stack of elements of suitable shape. Or again, the mixer may consist of a cylindrical tube in which a series of spirals or stationary helicoidal components are inserted.
Thus a preferred form of atomisation zone containing a succession of curved elements or vanes whose shape and arrangement are defined as follow~:-(a) the width of each vane is very largely equal to the innerdiameter-of the zone and the length of each vane is at least equal to 1.25 times the inner diameter of the zone, , (b) each vane is curved so as to impart in use, to the fluids passing through the zone, a rotary movement in relation to the axis of the zone, ., ~ 11 --(c) the shape of this vane is that which is obtained from a rectangular plate whose width is equal to the inner diameter of the tube, by twisting this plate so as to rotate the short sides in relation to one another by a certain angle about the great median, (d) the long sides of each vane bear in the inner surface of the tube and each vane divides in two the transverse section of the tube, (e) the vanes are oriented in such a way that the lead;ng edge of ~ach vane, except for the first vane above the mixer, forms an angle with the trailing edge of the preceding vane, and ~f) the vanes are fixed in the zone by any suitable means.

It i8 preferred that:

~a~ the length of each vane is between 103 and 3 times the inner tiameter of the zone, ,. (b) the angle formed between them by the leading edge and the -trailing edge of each vane is between 120C and 240C, (c) same vanes are curved in one directian and al-ternate with vanes curved in the opposite direction, in largely equal numbers, ` and total between 5 and 30 vanes, /

103~ Z~;
(d) the leading edge of each vane, except Eor the first vane up-stream, is in contact and forms an angle of 90 with the trailing edge of the preceding vane.

The atomisation zone may contain from 5 to 30 vanes. For preference it c~ntains between 10 and 20.

The vanes can be fixed at a certain distance from one another. For preference the leading edge of each wing, except for the first vane above..the mixer, is in contact and forms an angle that is not zero with the t~ailing edge of the previous vane. This angle can, for instance, be between 30 and 150. For preference it is about 90.

Use.is:-made for preference of a stationary mixer having largely equal numb~r~.of vanes-that are curved in both directions. The vanes of both types.can be distributed at random. For preference, they are arranged in equ~l:groups, the groups of vanes curved in one direction alternating with groups.:of vanes curved in the other directionO

.
Special preference is given to the following arrangement: the angle of twist.of.each vane is about 180; the adjoining vanes are twisted in apposite.directions; they touch one another, and the edges in contact form an angle of about 90 For preference, the.vanes.are fixed to.one another by-their points of contact. This fixing can take place in particular by soldering, welding v~'~

/

1()369Z6 or bra~ing. The vanes thus assembled can be kept stationary in the tube by any-suitable means. For preference, ~he lateral edges of the first vane above the tube are welded/soldered or brazed înside a ring which has the same inner diameter as the tube and is supported on an extremity of the latter. This form of assembly makes it possible to take the mixer-apart and replace the vanes.

Any skilled technician will be able to calculate the characteristics of the mixer to be used whatever its type, in particular the inner diamater of the tube, the length of tube occupied by the fixed devices inserted therein, etc. in relation to the delivery and initial pressure of the auxiliary gas, as has been fully explained above, so that the mixer-opposes the flow of that gas with the appropriate resistance.

Certain stationary mixers impart a rotary movement to the stream of fluids passing through the tube. If the gyratory component of the the tube, below the last element of the mixer, is considerable, the speed of the droplets at the outlet from the tube may have a transverse component such that the angle of opening of ~he jet is ill-adapted to the shape or aerodynamic characteristics of the furnace. In such a case, it is desirable for suitable means to be inserted in the tube immediately below the last element of the mixer, to reduce or cancel out the gyratory component of the current. These means may consist in particular of a curved element or vane, having a curve and a length such that it imparts to the fluids the necessary impetus for reducing or cancelling the gyratory component of the stream. For example, if ''" ~.

1036~
the mixer comprises a 3uccession of adjoinir~g vanes, in which two consecutive vanes are twisted in the opposite directions, this mixer can be modified by docking the last vane of about a quarter of it8 length; the gyratory component of the current below the last vane of the mixer thus modified is virtually nil.

It is preferred that the curved elements or vanes are inserted forcibly in the tube and the last vane downstream of the tube rests on a nozzle forming one part with the latter.

This method of assembly has several advantages. The vanes are no~
expelled from the tube if a weld has given way. The vanes, in particular the last one downstream, are perfectly stationary and this avoids the need for welding them to the tube. It is easily possible to replace the vanes in the event of tamage.

, The n~zzle is attached to the exit of the mixer, and gives the desired profi~e to the jet of atomised fuel, and therefore to the flame when the atomised fuel i8 subsequently burnt.
. .

This nozzle may comprise one or more-cylindrical or conical holes. The dismeter of the holes is sufficiently large for the stream of fluids to undergo only a slight 1088 of pressure in traversing them.

If the nozzle is a single cylindrical apertured nozzle then its diameter is suitably between 0.5 to 0.9, preferably 0.6 to 0.8 of the internal 2~
diameter of the atomi~ation zone. Where a plurality of holes are pro-vided in the nozzle, they are suitable arranged to provide a conically-profiled jet.

The effect of the nozzle gives the jet of atomised fuel and auxiliary gas tke desired profile. It also greatly improves the homogeneity of the aIstribution of the fuel in the auxiliary gas. This result was in no way foreseeable. Finally, the nozzle is advantageously used as a stop for retaining the curved elements in the atomisation tube.

The st~ream of fluids undergoes a 1088 of pressure in traversing the a~omiser and it sustains a further 1088 in traversing the nozzle.
Accor~ing to a preferential characteristic of the invention, the atomiser and the-nozzle act in conjunction in such a wsy that the 1088 of pres-snre through the nozzle is relatively slight. For preference, the mixer-and the nozzle-are calculated so that the 1088 of-pressure through the nazzle-is less than 80~, or better still, less than 50~ of the total 1088 of pressure.

..
The rate of flow of the fluids in the atomiser exerts a decisive in-fluence on the atomising of the fuel. The atomiser is calculated 80 that ~ith the desired deliveries, the flow of the fluids is very turbulent.

According to a preferred form of carrying out the present invention, the characteristics of the atomiser, in particular the inner diamater .

1036~Z~i of the tube and the length occupied by the parts inserted in it, are calculated so that the auxiliary gas undergoes a loss of pressure exceeding 3 bars, for preference between 5 and 20 bars, between the inlet and the outlet of the atomiser, the delivery of auxiliary gas being-such that it occupies after expansion, at the outlet of the nozzle, a volume of at least 30 times, or for preference 50 to 150 times, greater than that of the liquids admitted to the burner operating at its maximum output. For preference, the characteristics of the atomiser are also calculated so that under the conditions of pressure and delivery thus defined, the rate of flow of the fluids at the inlet to the atomiser is higher than 10 metres/second, or better still, than :
25 metres/second.

In all cases it is necessary to have as little dead space as possible downstream of the last element in the atomisation zone, to prevent caal-escence of atomised droplets. Hence the shortened last curved element is at the exit to the chamber; or the last full element abuts the nozzle~

Some embodiments of apparatus for use in atomisation and combustion proces.s of-the invention will now be described, by way of non~limitative e~amp~es, reference being made to the accompanying drawings in which:-Fig. 1 shows one device in longitudinal cross section, ~ig, 2 shows another device in longitudinal cross section, 1~36~2f~
Figs. 3 and 4 show modifications of the outlet from the device shown in Fig. 2, Fig. 5 shows a modification for varying the injection orifice of the device of Fig. 2, Fig. 6 shows further modifications of the device of Fig. 2, and Fig. 7 is a graph showing the supply of tar as a function of its pressure above the burner.
Referring to Fig. 1, the device comprise5 an inner feed tube 1, leading through an injecting orifice 9 into ante-chamber 3. A concentric tube 2, having inlet 20, also leads to the chamber 3. Chamber 3 leads to an atomisation zone comprising a tube 6 in which are housed fifteen curved elements 4 and one partial such element 5. The tube 6 has an internal-diameter of 14 mm. The elements 4 are each 20 mm long and twist through-an angle of 180, alternately in left hand-and right hand direction. The elements make close fit with the wall of tube 6 and the e~ements are brazed or otherwise secured to each other at their points of contact ~at which point the contacting edges are at about to each other).

The first of elements 4 is secured to a ring 8 secured to tube 6. The final element 5 is of reduced length, being about three-quarters that of elements 4, giving an angle of twist of about 135.

The extremity of tube 6 is conically shaped to enable a conical spray to be obtained.

,~' ' 'S,~,. ' ~,,.

Referring to Fig. 2, the basic con~truction is very similar to that in Fig. 1, like parts being given like reference numerals. A modification occurs, however, at the exit portion of atomisation zone 6. The elements 4 terminate with a full element and not the shortened element 5. The-e~tremity of tube 6 is formed into a nozzle 10 which acts to determine the shape of the spray issuing from the zone and act~ to retain elements 4 in the tube should they for any reason start to be ejected. The nozzle outlet 10 i8 for both these reasons located in the immediate vicinity of the final element 4.

In Fig. 3 the nozzle 10 is a member secured to the end of tube 6. The nazzle--has a truncated conical inner profile of angle alpha between 60 and 120.

In Fi&. 4 the nozzle lO has several cylindrical apertures 21 distri-buted in a conical manner to give a spray of a-conical shape of includ-ed angle beta. Preferably, to avoid dead space, the nozzle 10 has an inwardly projection portion 22.

Wi-th reference to Fig. 5, the apparatus can-be provided with means for varying-the-injection orifice 9. This means comprises needle valve rod-13, 14j movable into and from a corresponding seating in the orifice 9.

~inally, referring to Fig. 6, modifications are made ta provide further feed inlets such aj 24. Furthermore, for use in atomising certain :~ "

10369;26 combustible materials, the curved elements 4 are replaced by a first set 26a each element of which is of length about ten times that of those in the immediately following set 26b, The following examples illustrate, in non-limitative manner, processes in accordance with the invention.

Example 1 An apparatus as described with reference to Fig. 1 was employed.
The combustible material used was a hydrocarbon tar having the following characteristics:-o Density at 15 C1.131 Heptane-insoluble17.5 Viscosity at 50 C 975 cst Hexane-insoluble 43.2%
Viscosity at 100C 31 cst Carbon 87.8%
Residual carbon20.5% Hydrogen 7.1%
(Conrsdson method~ Sulphur 5.1%

The tar was preheated to 140C and fed at 8 to 15 bars pressure at a rate of from 400 to 900 kg/hour. The auxiliary gas was steam at conatant pressure of 6 bars and feed rate 30 kg/hour.

Upon issuing from the atomisation zone the atomised product was burnt in-an industrial furnace. A white flame was produced with no offensive smoke.

, 103t~9.26 This is a major advance since previously i-t has not been pos-sible to burn this type of hydrocarbon tar without producing black smoke.

Referring now to Fig. 7, the tar pressure, measured upstream of the tube 1 in bars, is plotted as abscissa. The corres-ponding supply of tar, in kg/h, is plot-ted as ordinate.

The steam pressure, measured upstream of the tube 2 is con-stan-t and equal to 6 bars.

In this figure, curve A represents the tar deliveries that are obtained with a device according to the invention provided with an injection orifice 9 whose diameter is 2.5 mm. Curve B rep-resents those which are obtained when the diameter is 3.5 mm.

An attempt was made to burn the same tar under the same condi-tions, but using injection of the usual type, with atomising by an auxiliary fluid. This usual type was identical with that which is represented in Fig. 1, except that no device was in-serted in the tube 6; the orifice 9 had a diameter of 2.5 mm.
Atomising was faulty and the flame obtained emitted black smoke, whatever the pressure and delivery of the tar and the steam above the burner.

"~

Example 2 An apparatus was used, as represented in the attached Fig. 6, for incinerating in a furnace sludge derived from the waste liquor of a petroleum refinery.

The tube 6 has a length of 3.90 m and an inner diameter of 14 mm. In this tube there was inserted a series of 18 curved elements 26a 200mm long, and a series sf fifteen curved elements 26b 20mm long. The leading and trailing edges of each formed an angle of 180. Element~
twisted ~n one rotational direction alternated with tho~e twisted in the opposite rotational direction.

By means of this apparatus a sludge was atomised (and thereafter burnt) derived from the residual liquor of a petroleum refinery.
This sludge contained 65Z water, 28% organic material and 7~
solid particles. It was fed into tube 1. A make-up fuel was used, being a heavy fuel oil having a viscosity of 200 cst at 50 C. The fuel oil was preheated to 140 C, and was fed into tube 2.

r i To ensure that the atomising and the propulsion of the sludge - and the fuel oil, an auxiliary gas was used being steam at a - pressure of 6 bars; being fed into tube 24.

,~ The deliveries were as follows:

,.
/
; - 22 -10369,Z~

700 kg/hour sludge 200 kg/hour fuel oil 50 kg/h steam.

The combustion of the fuel oil and the organic materials contained in the sludge was complete.

Example 3 The same operation was used for incinerating a sludge which con-tained 20% water, 70% liquid organic material and I0% solid particles. This sludge, like that of Example 2, came from the waste liquor of an oil refinery.

An auxiliary gas was steam at a pressure of 6 bars.

The deliveries were as follows:

700 kg/hour sludge 50 kg/hour steam :, No make-up fuel was needed. The sludge burnt completely.

"

'~' .,

Claims (20)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A process for the atomization of a flowable combus-tible material in an elongated atomization zone having an inlet and an outlet, comprising the steps of:
(a) feeding in a substantially concentric and relatively independent feed relationship at least one stream of an auxiliary gas and at least one stream of said combustible material, under pressure, into said in-let of and through said elongated atomization zone and characterized by having substantially all of the pressure drop which occurs in said auxiliary gas and said combustible material in said atomiza-tion zone between said inlet and said outlet thereof, said feeding of said streams being characterized by said stream of combustible material being substan-tially non-atomized by said auxiliary gas stream prior to entry into said inlet of said atomization zone and said auxiliary gas and said combustible material streams being mixed substantially completely in said atomization zone;
(b) expanding said auxiliary gas and simultaneously at spaced intervals along substantially the entire length of said zone splitting said gas and combustible material streams into partial streams and recombining sand partial streams and changing the rotational di-rection of flow of said streams to produce an atomized combustible material at said outlet;
(c) regulating the relative ratio of feed of said auxil-iary gas stream and said combustible material stream into the inlet of said zone so that at the outlet of said zone there is provided a substantially continuously atomized combustible material including said auxi-liary gas which occupies a substantially greater volume than that occupied by said combustible material; and (d) passing the atomized combustible material from said atomization zone through nozzle means located adja-cent said outlet of said zone and constraining said atomized combustible material into a predetermined profile.

2. A process according to claim 1, wherein a liquid fuel and an auxiliary gas are employed whereby the atomized product is an emulsion whose dispersed phase is the liquid fuel.

3. A process according to claim 1 or 2, wherein a liquid fuel and an auxiliary gas are employed and in which the deliver-ies of the auxiliary gas and the liquid fuel are in a ratio such that the volume occupied by the gas at the outlet of the mixer is at least 20 times greater than that occupied by the liquid.

4. A process according to claim 1 or 2, in which the pressure of the auxiliary gas, at the inlet to the mixer, is between 2 and 20 bars.

5. A process according to claim 1, in which the com-bustible material is a sludge containing organic matter.

6. A process accroding to claim 1, in which the com-bustible material is a sludge containing organic matter, and in addition to an auxiliary gas, a fuel such as natural gas, liquid petroleum gas or fuel oil is employed.

7. A process according to claim 1 or 2, wherein the auxiliary gas is selected from compressed air and pressurized steam.

8. A process according to claim 1, in which atomization zone comprises stationary mixer of the type consisting of a cylindrical tube in which a series of fixed curved elements or vanes are inserted, whose shape and arrangement are defined as follows:
(a) the width of each vane is very largely equal to the internal diameter of the tube and the length of each vane is at least equal to 1.25 times the inner diameter of the tube, (b) each vane is curved so as to impart to the fluids traversing the mixer a rotary movement in rela-tion to the axis of the tube, (c) the shape of each vane is that which is obtained from a rectangular plate whose width is equal to the inner diameter of the tube, by twisting the plate so as to rotate the short sides one in rela-tion to the other by a certain angle about the longer axis, (d) the long sides of each vane rest on the inner surface of the tube and each vane divided into two the cross-section of the tube, (e) the vanes, are orientated in such a way that the leading edge of each vane, except for the first vane upstream of the mixer, forms an angle with the trailing edge of the preceding vane, and (f) the vanes are fixed in the tube by any suitable means.

9. A process according to claim 1 or 2, in which the nozzle has a single cylindrical hole therethrough, said hole having a diameter between 0.5 and 0.9 of that of the inner diameter of the atomization zone.

10. A process according to claim 1 or 2, in which the nozzle has at least tow holes therethrough whose axes are distributed on a cone, whose angle of aperture is chosen as a function of the shape of flame it is desired to obtain.

11. A process for the combustion of a combustible material as defined in claim 1, which combustion process comprises ato-mizing the combustible material and thereafter burning the ato-mized material in the presence, if necessary, or a supply of oxygen or oxygen-containing gas.

12. A process according to claim 1 or 2, including the step of feeding said stream of combustible material at a pres-sure greater than that of said stream of auxiliary gas.

13. A process according to claim 1 including the step of passing said combustible material stream internally of said auxiliary gas stream.

14. A process for the atomization of a flowable combust-ible material in an elongated atomization zone having an inlet and an outlet, comprising the steps of:
(a) feeding in a substantially concentric and relatively independent feed relationship at least one stream of an auxiliary gas and at least one stream of said combustible material, under pressure, into said inlet of and through said elongated atomization zone and characterized by substantially all of the pressure drop in said streams being taken through said atomi-zation zone, and said stream of combustible material being substantially non-atomized by said auxiliary gas stream prior to entry into the inlet of said atomization zone and said auxiliary gas and said com-bustible material streams being mixed substantially completely in said atomization zone;
(b) expanding said auxiliary gas simultaneously at spaced intervals along substantially the entire length of said zone splitting the gas and said com-bustible material streams into partial streams and recombining said partial streams and changing the rotational direction of flow of said streams to produce an atomized combustible product at said outlet, (c) regulating the relative ratio of feed of said auxiliary stream and said combustible material stream into the inlet of said zone so that at the outlet of said zone there is provided a substan-tially continuous atomized combustible product in-cluding said auxiliary gas which occupies a sub-stantially greater volume than that occupied by said combustible material, delivering said combus-tible material into said atomization zone at a pressure greater than that of said auxiliary gas delivery pressure into said zone and maintaining said auxiliary gas pressure at a substantially con-stant level with respect to the delivery pressure of said combustible material and feeding said com-bustible material into said inlet of said atomiza-tion zone centrally with respect to said auxiliary gas stream, and further maintaining the temperature of said combustible material in respect to that of said auxiliary gas such that minimum condensation of said auxiliary gas occurs.

15. An apparatus for atomization of a flowable combust-ible material, said apparatus comprising in combination (i) an atomization zone, (ii) an ante-chamber connecting with the ato-mization zone, (iii) at least two feed inlets to the ante-chamber at least one being for a said combustible material at least one other for an auxiliary gas, said feed inlets being disposed in a substantially concentric and relatively indepen-dent non-impinging feed relationship, and (iv) nozzle means at or in the immediate vicinity of an exit of the atomization zone for modifying the profile of atomized material exiting from the zone; and in which apparatus the atomization zone is of generally cylindrical cross-section and is provided internally with means which are adapted to impart to streams of fluids multiple shearing action and changes of rotational direction.

16. Apparatus according to claim 15, comprising in com-bination:
(a) an atomization zone having an inlet and an outlet end, said zone being cylindrical in shape and having a uniform cross-section;
(b) a chamber connected adjacent said inlet end of said atomization zone and including a cross-section greater than said cross-section of said zone;
(c) a first inlet for said chamber for feeding said com-bustible material therein and a second inlet for said chamber for feeding said auxiliary gas therein;
(d) mixing means internally secured in said atomiza-tion zone for the length thereof for imparting to said combustible material and auxiliary gas flowing therethrough a multiple shearing action and change in rotational direction thereof along the length of said zone; and (e) nozzle means adjacent said outlet end of said ato-mization zone for providing a predetermined profile to the atomized combustible material which exits said atomization zone.

17. An apparatus according to claim 15, in which the said internal means are a succession curved elements or vanes whose shape and arrangement are defined as follows:
(a) the width of each vane is very largely equal to the inner diameter of the zone and the length of each vane is at least equal to 1.25 times the inner diameter of the zone, (b) each vane is curved so as to impart in use, to the fluids passing through the zone a rotary movement in relation to the axis of the zone, (c) the shape of each vane is that which is obtained from a rectangular plate whose width is equal to the inner diameter of the tube, by twisting this plate so as to rotate the short sides in relation to one another by a certain angle about the great median, (d) the long sides of each vane bear on the inner surface of the tube and each vane divides in two the transverse section of the tube, (e) the vanes are oriented in such a way that the leading edge of each vane, except for the first vane above the mixer, forms an angle with the trailing edge of the preceding vane, and (f) the vanes are fixed in the zone by any suitable means.

18. An apparatus according to claim 17, in which (a) the length of each vane is between 1.3 and 3 times the inner diameter of the zone, (b) the angle formed between them by the leading edge and the trailing edge of each vane is between 120 and 240°, (c) some vanes are curved in one direction and alternate with vanes curved in the opposite direction, in largely equal numbers, and total between 5 and 30 vanes, (d) the leading edge of each vane, except for the first vane upstream, is in contact and forms an angle of 90° with the trailing edge of the preceding vane.

19. An apparatus according to claim 15, 17 or 18, in which said nozzle has a single passage therethrough, said passage having a diameter between 0.5 and 0.9 of that of the internal diameter of the atomization zone.

20. An apparatus according to claim 15, 17 or 18, wherein the nozzle has at least two passages therethrough, the axes of said passages diverging conically with respect to the axis of the atomization zone.