FR2547033A1 - APPARATUS FOR THERMALLY TREATING SOLID MATERIAL, IN PARTICULAR CEMENT RAW MATERIAL - Google Patents

Abstract

THE OBJECT OF THE INVENTION IS A THERMAL TREATMENT APPARATUS OF PULVERULENT SOLID MATERIAL, CONSTITUTING A TUBULAR MIXING CHAMBER 2 WITH A VERTICAL AXIS, INCLUDING AT ITS BOTTOM PART A LOWER ORIFICE 21 FOR INTRODUCING A CURRENT C1 OF HOT GAS, A LATERAL PORT 22 FOR INTRODUCING A CURRENT C2 OF OXIDIZING GAS AND MEANS FOR INTRODUCING MATERIAL AND A FUEL INTO CHAMBER 2. ACCORDING TO THE INVENTION, THE CURRENT C2 OF OXIDIZING GAS IS DIRECTED TOWARDS THE CENTER OF COLUMN 2 AND THE LOWER ORIFICE 21 OF THE UPSCURRENT C1 INPUT IS OFFSET WITH THE AXIS 20 OF COLUMN 2 ON THE SIDE OF THE LATERAL ENTRY 22 OF THE CURRENT C2, THE SIDE WALL 26 OF COLUMN 2 FACING THIS BEING CONNECTED TO THE LOWER ORIFICE 21 BY AN INCLINED WALL 27 OF DEVIATION OF THE UPSCURRENT C1 FROM THE OPPOSITE SIDE TO THE CROSS CURRENT C2 BY LEADING FROM THE SIDE OF THE LATERAL ENTRY 22 A ZONE FROM THE SIDE INTRODUCTION OF AT LEAST THE LARGEST E PART OF THE FUEL. THE INVENTION APPLIES SPECIFICALLY TO THE PRECALCINATION OF RAW MATERIAL IN A PLANT FOR THE MANUFACTURE OF THE CEMENT CLINKER.

Description

2 1 U 7033

  The invention relates to an apparatus for heat treatment of pulverulent solid material that can be used in particular as a precalciner.

  in a cement clinker production facility.

  In dry cement production plants, the pulverulent raw material, before arriving at the clinkerisation furnace, passes into a suspension preheating device comprising a series of cyclone type superimposed mixing chambers connected to each other. by

  ducts and through which are sucked by a fan the exhaust gas

  both of the oven; these successively cross from bottom to top the differences

  cyclones, while the material undergoes a preheating descending from one chamber to another from top to bottom Each cyclone includes indeed an upper outlet of desgaz outlet, opening into the connecting duct with the cyclone placed on the floor upper and a lower outlet of the recovered material opening into the supply duct of the cyclone placed in the lower stage In this way, the material is suspended upstream of each cyclone in the gas updraft and goes down until the last cyclone, usually at the fourth level and

  whose lower orifice is connected to the entrance of the furnace by a pipe of

  Feeding material usually leading to the inclined bottom of a hood placed at the end of the oven to collect the gases leaving the oven

  and direct them towards a vertical connecting sheath emerging in the last

  cyclone and into which is introduced the preheated material coming from

  upper stages of the preheater.

  The heat required for the clinkerization reaction is produced

  by introducing a fuel into the furnace which is provided with a burner placed at its opposite end to the outlet hood and a preheated air inlet in a cooling device of the clinker coming out of the

  The calories of the gases leaving the oven are thus used in the oven.

  seems to cyclones for the preheating of matter However, we know

  cement clinker preparation is carried out in two stages, corresponding to

  one to an endothermic reaction of decarbonation of matter

  raw material and the other to the exothermic reaction of clinkerisation These two re-

  actions, which take place at different temperatures, are

  made in different enclosures.

  In this case, only the reaction of clink

  and the decarbonation reaction, also called calcination, is

  made in a separate heat treatment apparatus, called precalcine-

  and which consists of a mixing chamber interposed on the path of the material between the penultimate and the last cyclone of the preheating device. The purpose of the precalciner is to achieve a significant part of the decarbonation of the previously preheated material in the

  first three stages of the preheater It is therefore equipped with means of introduction

  combustion of a fuel such as burners and traversed by a stream of oxidizing gas consisting of heated air in the clinker cooler and, in some cases, by the gases leaving the furnace and containing a

certain amount of oxygen.

  Many embodiments of precalciner are known, all of which are intended to ensure an excellent heat transfer obtained, on the one hand by ensuring a good combustion of the fuel and on the other hand by realizing inside the chamber a mixing vigorous materials

  and different gas streams to homogenize as much as possible the tempera-

  In some cases, these two

  functions are performed in separate chambers, a combustion chamber

  in which the fuel, combustion air and any

  the material, and a mixing chamber which is traversed by the gases

  from the furnace and therefore containing a quantity of oxygen which depends on

combustion conditions in the oven.

  In other cases, the same gases are introduced into the same chamber.

  furnace, combustion air, fuel and preheated

  prefers, then, to divide this single room into several

  a pre-combustion zone in which the fuel is introduced into the air stream, a dispersion zone of the material and an intense mixing zone with the gases coming from the furnace. In one embodiment often adopted, to separate the different zones, the mixing chamber

  is provided at its lower part with a lateral orifice generally in

  te, through which a transverse flow of gas forming a vortex into the interior of the mixing chamber and which is provided in its axis with a lower orifice, generally with narrowed section, by which is made

  enter an updraft of a second gas that goes up in the axis of the turn-

  before mixing with it. Generally, the cross-sectional current

  sal consists of hot air and forms the oxidant necessary for

  combustion of the fuel introduced by burners placed on the wall la-

  lateral of the room; the pulverulent material is dispersed over the burners in this swirling stream and the assembly then mixes with the axial flow in the upper part of the mixing chamber which is

  connected to the last separator of the preheating device.

  All known precalciner chambers are generally expensive and cumbersome because of the desired performance when

  are installed in existing installations, they require

  very important changes to them and in particular to the

  preheating system Of course, these modifications are normally

  the increase in production resulting from the installation of the precalciner, but such an installation is less justified in the case of smaller installations in which only a

  modest increase in production which does not justify

  costly arrangements of the preheating device.

  The subject of the invention is a new type of precalcine

  However, it is significantly simplified compared to existing devices and still retains interesting performance, which makes it possible to use it in cases where the installation of a conventional precalciner would not have been justified. According to the invention, the mixing chamber having the shape of a vertical axis column provided at its lower part with a lower orifice

  with narrowed section for the introduction of the gas updraft, the

  The transverse flow of oxidizing gas is directed towards the center of the column and the bottom inlet of the upflow is offset from the axis of the cross sectional side of the cross flow.

  and the side wall of the column facing the latter is connected to the o-

  lower wall by an inclined wall of rising current deflection

  opposite side to the transverse current, leaving the side of the lateral entrance

  the one area of introduction of the transverse current in which are found

  placed the means of introduction of at least the greater part of the

tible.

  According to an additional feature, the mixing chamber has

  a rectangular cross section.

  The solid material is preferably introduced into the transverse flow of gas through a downcomer opening into the feed pipe of the transverse flow in a direction substantially

  vertically, immediately upstream of the exit orifice of the latter

  the cross-flow supply line is equipped with a

  horizontal division of the current, arranged across the pipe along a substantially vertical plane tangent to the pipe

  supplying the material opposite to the transverse current.

  According to another important characteristic, the apparatus comprises

  additional fuel injection ports in the area of

  In a particular embodiment, a plurality of fuel injection orifices, distributed over the

  two zones of the lower part of the mixing chamber and the means of

  fuel production consist of burners removably attached to only part of the orifices, the other orifices being

  plugged removably; the burner attachment holes and the

  respective fuel supply bits are then determined as a function of

  desired operating conditions, taking into account, in particular,

  temperatures observed in the different areas of the apparatus.

  In the accompanying figures, there is shown by way of example a particular embodiment of an apparatus according to the invention adapted to

  a cement production facility.

  Figure 1 schematically shows a production facility

  cement composition provided with a treatment apparatus according to the invention.

  FIG. 2 is an enlarged view, in axial section, of

  the lower part of the device.

  FIG. 3 is a view from above in cross section according to

III-III, Figure 2.

  FIG. 1 diagrammatically shows the lower part

  of a cement production plant comprising a rotary kiln

  1, a precalcinator according to the invention 2, a device

  suspension preheating system 3, of which only the

  lower part and a clincker cooling device 4.

  The inclined rotary kiln 1 is provided at its lowest end with

  It is supplied with fuel and at its upper end a hood 12 which directs the gases that passed through the furnace to the mixing chamber 2 This consists essentially of a tubular column with vertical axis, connected by its lower part to a lower inlet

  21 with narrowed section through which is introduced a rising current Cl cons-

  by the gases coming from the hood 12 The clinker formed in the rotary kiln

  1 down in the cooling device 4 which is traversed by air introduced by an inlet 41 and discharged through a pipe 42 after

  to be heated in contact with the clinker The pipe 42 feeds a collection of

  43 connected by a bent conduit 44 to a lateral inlet 22 formed on the side wall of the chamber 2, the lower part thereof,

  and by which is introduced a transverse flow C 2 of gas, in a di-

substantially horizontal rection.

  At its upper part, the chamber 2 is connected by an outlet sheath 23 to the last cyclone 5 of the preheating device 3.

  comprises a lower outlet 51 through which the solids separated

  The gases in the cyclone 5 are discharged via a pipe 52 opening onto the inclined bottom 13 of the hood 12 which thus leads them to the furnace and an upper outlet 53 which opens into a pipe 31 connecting with

  the penultimate cyclone 6 of the preheating device.

  The material introduced to the upper part (not shown) of the preheater 3 goes down from one stage to the next, is dispersed at 32 in the gases coming from cyclone 5 and carried by line 31 to cyclone 6

  from which it is evacuated by the exit 61 and the descending pipe 62 which de-

  mouth at its lower end in the conduit 44 for introducing the neck.

  transverse rim C 2, just upstream of the lateral inlet 22 of the chamber 2. FIGS. 2 and 3 show in more detail the operation

  of the mixing chamber 2 This consists of a tubular column

  vertical axis 20 preferably having, as shown in FIG.

  3, a rectangular section with two long sides corresponding to

  lay on the sidewalls 24 and two small sides, respectively one

  king before 25 in which is placed the lateral inlet 22 of the trans-

  versal and a rear wall 26 opposite the wall 25.

  On the other hand, according to an essential characteristic, the axis 10 of the inlet 21 of the ascending current C1 is offset with respect to the axis 20 of the column 2 on the side of the lateral inlet 22 of the transverse current placed in

  the front wall 25 The lower inlet opening 21 preferably has a sec-

  square and is connected to the rear wall 26 by an inclined wall 27.

  This arrangement allows the ascending current C1 to be deflected towards the rear wall 26 when it enters the chamber 2 under the action of the current C 2 which

  opens in a transverse direction through the inlet 22.

  Thus, the lower part of the mixing chamber 2 is divided into

  two zones placed substantially on either side of the median plane P parallele-

  the front 25 and rear 26 of the chamber 2, a front zone A of

  troduction of the transverse current C 2 and a rear zone B of passage of

  ascending current C1 after deflection.

  In the connection mode of FIG. 1, in which the

  ascending rant Ci is constituted by the gases coming from the furnace and the current

  transverse C 2 by heated air, the rear zone B contains less o-

  xygen than the area before A and it is therefore in the latter that we place

  the fuel introduction means constituted by burners 7.

  In this way, the preheated material arriving via the pipe 62 is dispersed in the transverse stream C 2 which then entrains it to the front zone A of the mixing chamber -o the fuel is introduced. The material is thus dispersed in a uniform in the hot air stream before being subjected to the heat produced by the combustion of the fuel

  and this occurs under good conditions given the strong

  oxygen portion of the front zone A Only then, in the

  medium of the mixing chamber and in the upper part, that the gases

  of combustion and the material mix with the furnace gases B which allows

  attempt to increase the temperature further and complete the combustion,

  ble being discharged through the outlet sheath 23 to the separation device which feeds the furnace. Of course, the calcination yield of the chamber according to

  the invention may not be as good as in the more perfected rooms.

  However, as can be seen in FIG. 1, the mixing chamber according to the invention has the advantage of being able to be placed in the place of

  the connecting duct between the oven hood and the last cyclone without

  significant development of gas and material circuits and positioning

different devices.

  Other provisions make it possible to improve the func-

  mixing chamber.

  Thus, it is advantageous to place horizontal bars 45 across the line 44 for introducing the transverse current C 2. As shown in the figure, the bars 45 are preferably arranged

  along a plane substantially vertical and tangential to the line 62 of food

  In this way, the transverse bars 45 divide the stream C 2 into a plurality of parallel flows which take up the material M down the line 62 and the clods break when they fall down. on the bars

  which thus ensure a better dispersion of the material.

  The lower wall of the pipe 44 is connected to the wall of the inlet orifice 21 by an inclined plane 46 placed below the outlet of the supply pipe 62 so as to take up the heavier particles which might not not have been driven by the current C 2 and direct them towards the current Cl which, then, makes them go up in the

mixing chamber 2.

  According to another important characteristic, it is advantageous to

  place additional burners 71 in the rear part of the walls la-

  24 of the chamber 2 to the lower part thereof, that is to say in the zone B passage of the rising current Cl after deflection The fuel flow introduced depends on the proportion of oxygen contained in the gases out of the oven and we can in this way use all the oxygen sucked by the inlet port 41 of the cooling device 4 Indeed, the primary air 15 for the combustion of the burner 1 liet secondary air

  16 from the clinker cooler 4 and back into the furnace collects

  to form the thermal current CI which therefore contains all the necessary oxygen relative to the amount of fuel introduced into the furnace.

  The auxiliary sprinklers 71 thus make it possible to provide a quantity of

  fuel and to make the best use of the amount of oxygen

  contained in the gases sucked by the fan through the preheat

  By placing the precalciner and the furnace

  kill the two combustion stations of the installation, we avoid a trimming

  sensitivity of the proportionality of air and fuel flows in each

one of them.

  Of course, without departing from the protection framework defined by

  the claims, amendments could be made to the

  tions which have just been described in detail as a simple example.

  Thus, in order to take into account, under the best conditions, the distribution of the gaseous currents between the two zones A and B of the mixing chamber, it is possible, according to an advantageous characteristic of the invention, to provide on the side walls. 24 several orifices 7

fixing burners.

  In this way, by observing the combustion conditions and / or

  measuring the temperatures at different points of the chamber, we can

  the burners on the holes best placed according to the conditions

  operating conditions (composition and flow of materials and gases by

  example), the other orifices 72 being closed by removable plugs.

  We thus realized a precalcination chamber that we can

  easily and economically fit into an existing facility or

  average capacity and which, despite its simplicity, can give an

préciable.

Claims (5)

  1 Apparatus for heat treatment of pulverulent solid material   te, constituted by a tubular mixing chamber (2) in the form of a column with a vertical axis, comprising at its lower part a lower orifice (21) with a narrowed section relative to that of the column 2, through which a pipe ( 21) for introducing an updraft (Cl) of hot gas,   a lateral orifice (22) through which an introducer line (44) opens   cross-flow (C 2) of oxidizing gas and means for introducing   ducting the material and a fuel in the chamber (2), the assembly being driven towards the upper part of the chamber (2) and then discharged to a device (5) for separating solids and gases, characterized by the the transverse flow (C 2) of oxidizing gas is directed towards the center of the column (2) and the lower inlet (21) of the upward flow inlet (Cl) is offset with respect to the axis ( 20) of the column (2) on the side of the side inlet (22) of the transverse stream (C 2), the side wall (26) of the column (2) facing it   being connected to the lower orifice (21) by an inclined wall (27) of   viation of the updraft (Cl) on the opposite side to the transverse current   (C 2) by providing on the side of the lateral entrance (22) a zone (A) of introduc-   tion of the transverse current (C 2) in which the   means (7) for introducing at least the largest part of the fuel.   Heat treatment apparatus according to claim 1,   characterized in that the mixing chamber (2) has a trans- rectangular versale.   Heat treatment apparatus according to claim 1,   characterized in that the solid material is introduced into the neck.   transverse flow (C 2) of gas via a downcomer (62) opening   in the line (44) supplying the transverse current in a direction   substantially vertical, immediately upstream of the exit aperture tie (22) thereof.   4 heat treatment apparatus according to claim 3, characterized in that the conduit (44) for supplying the transverse current (C 2) is provided with a plurality of horizontal bars (45) for dividing the current (C 2) arranged across the pipe (44) along   a plane substantially vertical and tangential to the feed pipe (62)   in materials opposite to the transverse current (C 2).   Heat treatment apparatus according to one of Claims 2 and 3, characterized in that it comprises additional fuel injection orifices (71) in the upflow zone (B). thermal device according to claim 5, characterized in that it comprises a plurality of fuel injection orifices distributed over the two zones A and B of the lower part of the mixing chamber (2) and that the means of fuel introduction are   constituted by burners (7) removably attached to a single part   holes, the other orifices 72 being closed in a removable manner.   the positioning of the burners (7) and the respective feed rates of   fuel consumption being determined on the basis of the operating conditions desired.   7 Heat treatment apparatus according to one of the claims   prior art, characterized in that it constitutes a device for precalcination of the raw material, interposed, in a cement manufacturing plant, on the path of gases from a clinkerisation furnace (1) to an assembly (3) for preheating the material suspended in the gases, comprising a succession of stages for separating the material, the upward flow being constituted by the gases coming from the furnace (1) and the transverse current   (C 2) by hot air coming from a cooling device (4) of the clin-   ker and the mixing chamber (2) opening at its upper part (23)   in the last stage (5) for separating the preheating assembly (3).