FR2623878A1 - PROCESS FOR THE COMBUSTION OF A FUEL FROM GARBAGE IN A CLINKER BURNER BURNER FOR CEMENT AND BURNER FOR CARRYING OUT SAID METHOD - Google Patents

Abstract

In this process, the fuel is incinerated in a cement clinker production furnace burner 8, in which it serves as an auxiliary fuel to conventional fuels. This method includes storing the mass of garbage, dosing and transporting it in the burner and the incineration or combustion itself. The fuel is therefore loaded into a feed box 2 with a moving base; then, under the action of cooperation of fluidizing rollers 3 filled with tips, it is transferred to a weigh feeder 4 where it is sent to the burner 8 of the oven 9 by means of a pneumatic conveyor 6, 7 under the control of an alveolar dispenser 5 which ensures the sealing and the constant distribution of this material.

Description

PROCESS FOR COMBUSTION OF FUEL FROM GARBAGE

  IN A BURNER OF CLINKER PRODUCTION OVEN FOR

  CEMENTS AND BURNER FOR CARRYING OUT SAID METHOD

  The present invention relates to a method for the combustion or incineration of waste fuel and its simultaneous use as an auxiliary fuel for conventional fuels (coal, oil, etc.) in the production of clinker for cements it relates in in addition to one or more means

to achieve this goal.

  It is well known that the uncontrolled discharge of solid garbage on the soil and on the banks of watercourses has produced and still produces vast phenomena of soil pollution, and the social, technical and economic problem posed by their collection and disposal is now at the same level of severity as those posed by water purification and by

the purification of the air.

  The technical solutions adopted today to avoid, or at least to minimize, the disadvantages and dangers of the improper discharge are: controlled discharge, thermal destruction with or without heat recovery, composting, composting with production of waste fuel. An operation of a complementary character, which is not new in principle, but which has only been carried out on an industrial scale for a few years, is recycling, that is, recovery and recycling.

  reuse of still usable materials.

  Although the most common disposal method is the controlled landfill, incineration and recycling are often used, even if the latter is considered to have enormous potential for reducing waste. The thermal destruction of raw waste, on the other hand, exploits the combustible properties of certain parts of the garbage, by transforming the latter into inert solid residues (ash and slag) which occupy a reduced volume (up to 20% of the volume).

  initial), and gaseous residues (combustion fumes).

  These fumes, which lead to gases and powders, must be purified before being sent to the atmosphere. The incineration plants consist essentially of the incinerator furnace and the corresponding services (garbage collection pit, means of loading, slag unloading and slaking systems) and flue gas cleaning equipment (electrostatic precipitators, cooling towers). washing, etc.) whose cost is, for small or medium installations, of the same order of magnitude as that of ovens. One of the problems of thermal destruction facilities today is to overcome prejudices

  the inadequacy of incineration facilities of the past.

  The composting process separates and recovers the organic substance contained in the garbage and its transformation, by aerobic processes, into a stabilized product made hygienic and used in the soil to supplement their organic content. What's left of the garbage is the

  "surplus" (paper, fibers, plastics, wood, etc.).

  In an installation carrying out only the transformation into compost, the discharge is an integral part of the installation, because it is in this one that

the "surplus" is deposited.

  A particular case of composting is that which allows the production of waste fuel. This is done in practice in an installation that uses the previous diagram for the transformation into compost, while the "surplus" undergoes a subsequent selection process (metals, glass, etc.), crushing, homogenization, etc. ., whose final product, which has a lower calorific value equal to approximately 4000 kcal / kg, is designated by the name of

fuel from garbage.

  The Applicant has found that it is possible to achieve an optimal recovery of the thermal content in the case where the fuel-garbage is used as auxiliary fuel material in clinker kilns for cements, according to the method and using the series of facilities that will be specified

further.

  As is known, the cement is obtained from agglomerates of raw materials, mainly limestone or clay, extracted from the quarry by various systems, and then transformed into a product called "clinker", which, combined with other constituents, gives rise to various types of cement. Natural clinker and artificial clinker are distinguished according to whether they are obtained from materials (marls) which already contain in adequate proportions the necessary constituents, or from mixtures prepared artificially. The manufacture of the clinker takes place through two basic phases: the preparation of the crude mixture (crushing, mixing, homogenization) and the cooking of the mixture to a temperature of about 1450 C, generally performed in large rotary kilns; the production of the cement is the result of a subsequent operation, which consists in mixing in proportion established in advance of the clinker (cooled) and the other constituents (according to the type of final product) and grinding this new mixture, until to obtain a

very fine and homogeneous powder.

  The production of cement is generally distributed according to the location of the demand, and in this respect it should be emphasized that, while the problems related to the availability of the raw material are of little importance, the installation of a modern cement works requires, on the one hand, that considerable capital is available for the initial investment, and on the other hand that there are

adequate sources of energy.

  The method offered by the present invention, while being limited to the clinker forming phase, allows the use of a convenient source of energy (while at the same time solving the problem related to the disposal of garbage,

  as previously stated).

  Therefore, the invention includes a method for the incineration or combustion of garbage, in particular solid garbage, incineration which is carried out in a particular design burner which in turn becomes

  a second object of the present invention.

  The process as a whole should not be understood as relating to the only combustion phase, but this latter operation must be considered in terms of all those which precede it and which, as a whole, constitute the nature of the invention.

herself.

  In accordance with the present invention, the garbage fuel is thus incinerated in a burner of an oven for the production of cement clinker, in which the auxiliary fuel function is performed for conventional fuels. The process, as a whole, provides for the storage of the mass of the garbage, the dosing and the transport of the same in the burner and the incineration itself: the garbage fuel is loaded into a feed box & moving bottom ; then, with the aid of spiked rollers, it is transferred into a weight dosing system where it is introduced into the burner by means of a pneumatic transport under the control of a honeycomb distributor which seals and the constant distribution of the

matter itself.

  In broad outline, the method of the present invention therefore comprises the storage phase of the mass of garbage, the metering and transport thereof in the burner, incineration or combustion itself; this method is implemented in a compact structure installation and fully automated that can exist in fixed or mobile version. The installation, in view of the fact that the storage box must be fed from above in continuous running conditions and also by its rear part for discontinuous operation, can be carried out partially as well.

  buried only totally above the ground.

  The sizing of the installation, which naturally depends on the required capacity and the physicochemical characteristics of the material to be burned, and even less the location of the latter, for which it is naturally advised a protected enclosure to avoid the negative effects of atmospheric agents as

rain or wind.

  Referring explicitly to the figure, it will be seen that this represents a possible scheme of the plant in which the process of the present invention may be carried out: other embodiments are of course possible or, more , various practical solutions, but all must be considered as falling within the scope of the present invention, the embodiment to which it is made

  reference here given by way of example only.

  In the figure mentioned above, reference numeral 1 designates the loading box, 2 the feed box, 3 the series of fluidized point rolls, 4 the weight dispenser, the honeycomb distributor, 6 the compressor, 7 the feed pipe , 8 the burner, 9 the oven, 10 the pump unit, 11 the hydraulic oil tank

and 12 the oil filter.

  The method, as indicated, provides for a series of operations and is fully regulated by electronic devices which allow centralized and constant control of all cycles and operations which, with reference also to the diagram of the figure, may be listed as follows: - storage and extraction; - weighted dosage; - pneumatic transport;

- incineration.

  The storage and extraction phase is carried out in an area that is essentially composed of a parallelepiped shaped hopper, dimensioned and endowed with mechanical characteristics that depend on the nature of the material to be treated, supported by an adequate metal framework, constructed it also depends on the version of the required installation, which, as mentioned, can be fixed or mobile. With regard to the storage and extraction phase, it should be noted that the movable bottom box described in the patent application can be used.

Italian NO 18126 A / 85.

  The bottom of the hopper is a moving plane consisting of pearls or pearl elements, preferably aluminum, sliding relative to each other according to a logic cycle appropriately controlled by electronic devices for advancing or retreating the material However, depending on the requirements, the automated control allows progress or gradual settlement of the material to the dosing system. On the discharge path of the material of the box are inserted, in series, spiked ginners and fluidifiers which allow a constant supply of the discharge hopper. The control of these spiked rollers may be independent or not, the attachment being arranged

  to allow the desired positioning.

  The progressive dosing stage is effected efficiently via a storage hopper loading / unloading hopper, which permits unencumbered feeding of the conveyor belt weight meter (4 of FIG. electronic charging cells, which guarantee the continuity and accuracy of the dosing of the

treated matter.

  As storage box and feed, it is advantageous to use the box with movable bottom described in the Italian patent application N 18126 A / 85, which will be referred to for possible details: anyway, any other practical solution is possible, provided that the dosing hopper 4 is set in such a way that the flow of material can be automated according to the requirements of the evacuation cycle.

garbage / clinker production.

  By means of the compressor 6, the material is sent via line 7 to the burner; the function of the honeycomb distributor 5 is to ensure the sealing and the constant distribution of the material, however, given that the size of the compressor, the honeycomb distributor and the transport pipe depends on the capacity of the installation, physical characteristics

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  the material and the route of the transport pipe, the transport speed advantageously remaining

between 18 and 27 meters per second.

  The material, as well dosed appropriately, is sent to the clinker burner. In this case also, it is clear that the dimensions of the burner can be chosen according to the physical characteristics of the material to be burned (specific weight, particle size, humidity, ignition point, lower heating value, percentage of volatile matter, etc.) and / or operating characteristics and conditions of the combustion chamber, or depending on the internal construction of the furnace for the production of clinker. Thus, the form of construction must be such as to guarantee the greatest possible duration; the speed of the air-fuel mixture at the exit of the burner varies according to the aforementioned parameters, anyway

in the range of 30:60 m / sec.

  For building materials, the use of refractory steels must be provided; the burner is protected against deformations due to radiant heat by refractories resistant to high temperatures. The burner of these solid materials in pieces can be arranged relative to the support fuel burner concentrically, superimposed or even peripheral. This results in a burner of the compound type with injection, followed by the burner of the other solid or traditional liquid fuels: the best positioning is defined by knowing the shape of construction of the combustion chamber and the

  process in which the burner itself is inserted.

  Therefore, respecting the conditions mentioned above, and considering that any over-sizing or undersizing of the burner described below will not be a solution outside the scope of the present invention, this burner which, inserted in a furnace for the production of clinker, makes it possible to use the energy from the combustion of solid waste for the preparation of it constitutes a second object of the present invention. This burner comprises the following basic sections: 1) an outer annular chamber which allows the passage of primary axial combustion air; 2) an intermediate annular chamber which allows the transport and introduction or insufflation of

  traditional solid fuels; -

  3) an internal annular chamber which allows the passage of the radial primary combustion air; 4) an internal nozzle for the burner housing

  main traditional liquid fuel.

  Compared to traditional burners, it has the following differences and benefits: 1) Great flexibility with the ability to make

  vary the combustion capacity from 10 to 30 x 106 kcal / h.

  2) A great adaptability with the possibility of giving the flame lengths and shapes

very diverse.

  3) A high combustion efficiency due to the possibility to vary the flow rate and the pressure of the primary air by giving the flame a strong dynamic. 4) Energy saving in that the burner can operate with a minimum of primary air: 3 to 4% of

total combustion air.

  As a simple example, one will describe in detail, a type of burner fueled by a fuel

from garbage.

  Type of oven - clinker production furnace, 3.30 x 3.0 x 3.30 m wet process - heat recovery, chains and crossings clinker coolers: planetary - daily production: 400 t maximum heat load 30 x 106 kcal / h - carrier fuel, coal dust - coal dust with characteristics: calorific value: 7300 kcal / kg; volatile matter

27%; ash 7%.

  Characteristics of the waste fuel - Particle size <49 mm - Specific gravity 0.2 - 0.25 kg / dm3 - Moisture <20% - Heating value 3500-4500 kcal / kg - Ash <15%

BURNER

  - Capacity 800 kg / h of waste fuel - Transport air 650 m3 normal The burner consists of a central tube 78 mm internal diameter in steel AISI 310 S = 6, particularly resistant to both abrasion and 'to

high temperatures.

  At a distance of 360 mm from the end a reduction is made which, in 160 mm, carries the internal diameter to mm. The last long part of 200 mm is cylindrical. The above reduction is dimensioned to obtain a better air-fuel mixture from garbage, and to adjust the rate of insufflation which

must be 55-60 m / sec.

  The above burner is lined with a tube of 102 mm internal diameter, also steel AISI 310 S = 6 to protect it from the fallout of the clinker and the temperature. The jacket is protected on its side by a 40 mm thick refractory rammed material and is provided with hooking hooks to the nozzle of the main burner of 0-4 mm, 30 mm, hook height 20 mm in AISI steel. 310. Hooks and surfaces to be coated with rammed earth shall be coated with thick varnish or melted tallow before casting. The space left by this material once destroyed when the temperature increases will allow the

dilation of the coating.

  The burner will be installed superimposed on the primary burner with the possibility of modifying the

  positioning by moving it at a maximum angle of 45o.

  For this purpose, the zone of passage of the burner in the part

  rear of the oven will be properly arranged.

  Still as an example, a normal operation of the installation for carrying out the process according to the present invention provide that the material will be supplied (discontinuously) by the storage hopper. From this, via the mobile plan, it will be transferred to the weigh feeder which sends the quantities determined in advance to

pneumatic conveyor.

  The level indicator placed on the feed hopper of the weight dispenser allows a constant load thereof by intervening on the movement of the movable plane of extraction of the material of the storage hopper. The pressure switch mounted on the air compressor line protects from clogging of the material transport pipe. The pressure acts on the step of the weigh feeder. The pressure switch placed at the end of the pneumatic conveyor serves for the detection of sections

  potential of the transport line engorged.

  Any type of garbage can be used for carrying out the process according to this

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  invention, particular advantages having been obtained by the use of solid waste selected from: fuels from garbage or detritus of various sizes or densities, sawdust, etc.

Claims (4)

  1. A method for the combustion of a waste fuel in a burner of a clinker production furnace for cements, this fuel serving as an auxiliary fuel for conventional fuels, the aforementioned method comprising the storage of the garbage mass , the metering and transporting thereof in the burner and the actual combustion or incineration being characterized in that the waste material as fuel is loaded into a moving-bottom feed box (2) and then with the aid of fluidizing point rollers (3), is transferred to a weight feeder (4) where it is sent to the burner (8) by means of a pneumatic conveyor under the control of a honeycomb distributor (5). ) who assures   the tightness and constant distribution of this material.   2. Method according to the preceding claim, characterized in that the material is transported in the burner at a speed between 18 and 27 meters per second.   3. Process according to any one of the claims   previous, characterized in that the storage and extraction phase is carried out in a parallelepiped-shaped hopper, the bottom of which is a mobile plane constituted of pearls.   4. Burner allowing an exit velocity of the air-fuel mixture in the range of 30 to 60 m / sec,   usable in the process according to the claims   preceding, and comprising the following basic sections: -external annular chamber for the passage of axial primary combustion air, intermediate annular chamber for the transport and insufflation of traditional solid fuels, -internal annular chamber for the passage of the primary combustion radial air, - internal nozzle for the burner housing   main traditional liquid fuel.