COMBUSTION FURNACE PARTICULARLY FOR WASTES

Description

Technical Field

[0001] The present invention has for object a waste combustion furnace, also for the wood manufacturing and plastic material scrapes.

Background Art

[0002] In prior art the waste combustion furnaces are already known.

[0003] Clear reference to the patents IT-83433A/90 and IT-91A000161 (in the name of one of same inventors GIUST ANDREA) is hereby made.

[0004] A same solution is disclosed in DE 3941759 A (PAULI BALDUIN) and in Patent Abstracts of Japan vol.007 n.020 (M-188) 26 Jan.83 & JP 57175811 A (INSINAA KOGIO KK).

[0005] All these patents disclose a waste combustion furnace, characterised in the presence of an entry step structure (stepped floor-stoker) with reciprocating pusher means stepped floor (stoker) for support and advancement of the material during its combustion, towards a discharge area. Furthermore in IT-83433A/90 and DE 3941759 air pushing flow means from below the said floor supporting the material to burn, is further provided.

[0006] These solutions even if advantageous allow to easily burn also wet and of the most different type waste materials.

[0007] For what concerns instead the wood industries waste material combustion, the problem is more difficult, considering that the wood manufacturing waste material contains substances with a high combustion level in a dry state, such as for instance the materials coming from the chip and MD = "Medium Density" panels manufacturing.

[0008] These are therefore materials which contain both wood and resins and highly combustible plastic and with a high calorific power materials.

[0009] Furthermore, the material has a rather large size, or is in dust, in chips and in small pieces and in more or less large pieces.

[0010] The consequence is that such a type of material is very difficult to be burnt homogeneously and with a low level of unburnt gases, which notoriously pollute the environment, because of the presence of dusts which mainly derive from the sawing.

[0011] Thus the material contains saw-dust, chips and small pieces of wood, resinous substances and plastic materials.

[0012] The plastic materials derive from the laminated panels coating such as for instance the ones used for the furniture manufacturing.

[0013] The resinous substances derive from the glues and from the binding plastic materials forming chips and thickened products such as the MD.

[0014] These resins and plastic materials have the most different origins, such as for instance phenolic resins, epoxidic resins, ureic resins and melamine resins.

[0015] All these resins and plastic materials together with dry wood, are more or less combustible and with a high calorific power, but are also very polluting because of the unburnt smokes high rate emission (particularly for the resins and plastic materials).

[0016] This caused the need of being able to control the combustion temperature level and of reducing at the minimum the unburnt smokes and the still unburnt smokes, also by means of a post-combustion action.

[0017] The combustion temperature may considerably increase, and it is difficult to be controlled, and it is dangerous for the combustion control.

[0018] The furnace life is limited, the maintenance is frequent.

[0019] In particular, in any of above cited prior art (IT-83433A/90, IT-91A000161, DE-3941759 and JP-57175811), the high temperature presence may especially compromise the system of pushers which move in a reciprocating way for the material advancement, because of the high temperature which makes the metal material little resistant, which when in presence of obstacles may also be deformed.

[0020] For such reason some systems for decreasing or at least for limiting the combustion temperature by using heat exchange known means were studied, but this brings the drawback of worsening the combustion performance. so the solution does not find an easy way out, either the temperature decreases and a furnace structures long life is obtained but there is a polluting combustion, or the combustion temperature increases with a good yield, but in this case the furnace life is considerably reduced. The presently existing solutions are not yet able to supply a suitable performance to the plant for the treatment of these materials and even to make it suitable to the combustion both of damp or wet materials with a low calorific power and or alternatively of the highly combustible ones with a high calorific power where a suitable combustion control or restraint or at least a suitable heat regeneration is needed. In particular the same above stated IT-83433A/9 and even US-5323718 discloses an incinerator with a combustion chamber provided with a pair of side walls, a floor-stoker disposed in the combustion chamber between the said walls and an underfire air system, an overfire air system generally consisting of a first means for injecting:

• a variable volume of air under pressure into the combustion chamber at a level above the floor-stoker, and
• a second means for injecting a variable volume of air under pressure into the combustion chamber at a level above the floor stoker

said second variable volume of air injecting means, including means for conveying air supplied to the combustion chamber in heat exchange relationship with at least one side wall of the combustion chamber for cooling such wall (to see the abstract, whole description and claim 1 in particular).

[0021] EP-A-0290317 discloses an air supply duct from below the combustion material.

[0022] Purpose of the present invention is that of obviating the above mentioned drawbacks and allowing to realise a universal furnace able to treat the most different materials:

• also the ones containing powdery material, and
• also the ones with a high calorific power and thus of being able to provide the combustion chamber with very high temperatures, but without endangering the same furnace structure (e.g. also combustibles deriving from the urban solid wastes).

Essence of the invention

[0023] The problem is solved as claimed by means of a combustion furnace particularly for wastes, of the type provided with a structure for the advancement of waste material in the combustion chamber, having a floor with stair-down sectors overlapped by retractable advancement elements with a to-and-fro reciprocating movement having a pusher function for advancing the combustion material towards a downstream area for the ashes discharge, wherein cooling air flow jet means under pressure, into the combustion chamber are provided, characterised in that,

• just at the material entry and under it, in the respective combustion chamber, a first air flow means with air-jet nozzle series is further provided, said air-jet nozzle series being able to separate the dust from the biggest sized dust;
• a second separation and throwing dust air-jet means from underneath the material advancement grate or steps is further provided.

Advantages of the new solution

[0024] In this way there is the advantage of having a considerable combustion improvement with a higher yield and performance and a plant universality of use, reaching rather high temperatures and allowing a complete combustion of the material with a smaller amount of polluting residuals.

[0025] In fact with this type of plant it will be possible to burn both non-powdery heterogeneous materials and powdery materials (in this latter case by activating said air-jet).

Preferential variations

[0026] Advantageously for improving the device efficacy a transversal piping in said step structure and in the side walls for the temperature decrease in these areas and at the same time for obtaining a heat regeneration by heat exchange fluid (preferably hot or overheated water) is provided.

[0027] As much advantageously two ventilation systems will be obtained, the first one as said for the separation and throwing of said dusts and the second one for a ventilation from the whole furnace walls, both from underneath, and by side and above the entry mouth of the materials to be burnt.

[0028] Thus, controlling and decreasing the excessive temperature in the furnace structural and functional parts is possible, in addition to supplying a suitable contribution of comburant and oxidising air.

[0029] Substantially this furnace is suitable to treat different types of wastes and therefore:

high calorific power and powdery wastes deriving from the wood manufacturing and with the function of obtaining a combustion high yield which is fundamental in the adiabatic and non-adiabatic chambers, and

high humidity degree wastes (30-35%) such as biological mud, barks, but also wastes.

[0030] By this solution the furnace is able also to carry out the combustion of high calorific power dry residuals such as plastic laminates, varnishing smudges, melamine, phenolic papers and other industrial wastes in general.

Description of at least one form of invention embodiment.

[0031] These and other advantages will appear from the following description of a preferential embodiment solution, with the aid of the enclosed drawings, whose execution details are not to be considered as limitative but are only given as examples.

[0032] Figure 1 is a longitudinal section schematic view of the furnace on the vertical plane.

[0033] Figure 2 is a front schematic view of the combustion chamber, with a particular view of the heat regeneration system with fluid side piping.

[0034] Figure 2A is a partial view of the heat exchange side piping with the thermal regeneration fluid (advantageously water).

[0035] figures 3,4,5 show the side, plan, and front view of the pusher combs or teeth or grate pusher elements, which move in a reciprocating motion for making the material advance in the various steps and which make up the combustion grate plane.

[0036] Figures 6,7,8,9 show in view: 6 from the bottom, 7 in longitudinal section and 8 and 9 transversal section, of a comb tooth of the previous figures.

[0037] From the figures it may be understood that:

[0038] The furnace function is that of obtaining the thermodistruction of the material which is made advance at first on the tilted plane 21 and then on the steps 22, 23, 24 by movable sectors 32, 33, 34 which ensure the wastes advancement during the combustion process.

[0039] These are therefore reciprocating movable grate sectors "reciprocating grate".

[0040] The furnace is made up of a fixed part in refractory casting and a movable part in refractory steel (movable step structure 32,33,34), is particularly suitable to the treating of manufacturing residuals and high calorific power wastes (p.c.i. kcal/kg. 4000-8000).

[0041] This furnace comprises:

• wastes feeding (1) with checking door (11) and following advancement inside of the combustion chamber (2) by means of an Archimedean screw or pusher with oleodynamical functioning (12) which push the wastes, at first on the tilted plane (21).
• said tilted plane (21) is fixed and it has an inclination of about 30-35% such to allow en easy entry and downflow of the wastes in the combustion chamber; the other steps (22, 23, 24) are also fixed in refractory or grate metal material with water cooled piping, and are horizontally placed on line and the wastes movement from one step to the other is ensured by the mechanical action of the cast or refractory steel pushers (32, 33, 34) on a bearing frame (31), mounted on trolley wheels moved by an oleodynamical cylinder with gear motor;
• the series of fixed steps (22,23,24) has at least the corner of each step made up of a rectangular section pipe, fixed on the heads of the steps (62), in which the hot water or other secondary fluid such as overheated water passes.

[0042] The fluid passage in the pipes allows a cooling of the fixed steps head when high calorific power wastes are burnt, avoiding the fast wear and the subsequent continuous maintenance.

[0043] The secondary fluid, contained in the pipes placed on the grate fixed steps, is conveyed through the suitable pipe bundle along the refractory side walls (61) for allowing a high and better energy regeneration respect to traditional solutions, and subsequently conveyed to the overhanging side collectors (62).

[0044] Such a solution ensures a better efficiency of the total thermal regeneration because the recovered heat may be conveyed in the heat regenerator (8, 81) with a primary circuit (8) or in a separate circuit by the exit of the combusted gases flow (81).

[0045] The primary and secondary combustion air is distributed in a separate and autonomously controlled way:

• by a first plant (4-41) both under the grate (32-33-34), thus under the steps (22-23-24), and on the grate side, that is from the furnace side walls (43), and on the furnace head above the entry mouth (42);
• by a second plant (5) with horizontal air-jet nozzles under the entry mouth (51) for separating and throwing in the air the advancing material dust so that it will burn better, at the same time easing the combustion of the underlying heavier size now freed from the dust presence which would otherwise choke the combustion.

[0046] The two air plants are activated by means of respective centrifugal fans (6, 5) which supply the amount of air necessary for the combustion process whose delivery is controlled by an inverter.

[0047] The inventive essence thus derives from that together with the previous characteristics and what already said, on the furnace head next to and underneath the feeding Archimedean screw (12), a series of horizontal air-jet nozzles (51) are positioned, with the function of making the waste inserted as dust advance (e.g. smoothing dust, polyester dust) thus easing the combustion of this material in suspension and at the same time allowing the combustion on the grate of the waste having a rougher and heavier size.

[0048] The thus designed furnace allows a first drying of the wastes in the upper steps by means of the surrounding hot smokes and the complete combustion of the wastes along the whole grate also eased by the wastes mixing movement carried out by the toothed pushers (30) (32,33,34) which move in a reciprocating way above said steps (22,23,24).

[0049] The movement speed and frequency of the pushers are determined each time according to the physical-chemical characteristics of the treated wastes and residuals, in order to ensure at the advancement end and before the discharge area, provided with a manhole 25, by an opening control (25'), the complete combustion of the wastes into ash.

[0050] The ashes fall, at the timed opening of the discharge refractory door (25) with oleodynamical drive (25'), into an underlying collection system, which may be made up of a palletizable trolley placed on rail (7) or of a "redler" belt for conveying the ashes outside of the incinerator room.

[0051] In an alternative variation the manholes are two and a discharge Intermediate pre-chamber is formed, so that for the ash discharge:

• the first one opens discharging the ashes in an intermediate underlying chamber (25');
• subsequently, the first one closes and the second one of the intermediate underlying chamber opens, discharging the ashes into said underlying trolley.

[0052] Thus the advantage of preventing the air passage into the combustion chamber is obtained, a fact which may endanger the normal optimal plant functioning.

[0053] The operational advantages which derive from adopting the piped heat exchange structure in the steps and side walls (6,61,62) are:

• combustion temperature reduction avoiding formation of ash melting on grate and along the refractory side walls (61).
• smoke delivery reduction because of the air excess decrease in the combustion chamber.
• reduction of the maintenance interventions on the corners and on the steps and on the side walls.
• optimisation of energy regeneration by exploiting the direct radiancy principle, in addition to the convection one, during the thermal exchange process.
• the pipe bundle on the grate allows to keep the same grate cooled, reducing the excessive air contribution.
• it is particularly useful also for the specific treatment of high calorific power wastes.

[0054] Advantageously the access to said post-combustion or post-treatment chamber (8) is obtained by means of an upper opening opposed to a baffle plate projecting into the combustion chamber (9).

[0055] Thus a plant yield increase is obtained.

[0056] The post-combustion furnace (8) may alternatively be used also for a complete oxidising in a single chamber of a large surface and/or volume also having a decantation function and comprising single-block heat exchange piping.

Claims

1. Combustion furnace particularly for wastes, of the type provided with a structure for the advancement of waste material in the combustion chamber (2), having a floor with stair-down sectors (21, 22, 23, 24, 25) overlapped by retractable advancement elements (32, 33, 34) with a to-and-fro reciprocating movement (3) having a pusher function for advancing the combustion material towards a downstream area for the ashes discharge (25), wherein cooling air flow jet means under pressure, into the combustion chamber are provided, characterised in that,

- just at the material entry and under it, in the respective combustion chamber, a first air flow means (5) with air-jet nozzle series (51) is further provided, said air-jet nozzle series (51) being able to separate the dust from the biggest sized dust;

- a second separation and throwing dust air-jet means (4) from underneath the material advancement grate or steps (21,22,23,24) is further provided (41).

2. A furnace, according to the previous claim, characterised in that the combustion furnace comprises a heat recovery conveyance (62) with liquid-cooling-fluid which is heated by passing through the refractory side-walls (61) of said stair-down sectors, the combusting chamber side walls in ducts (6) and then is conveyed in a heat regenerator of a post-combustion chamber (8).

3. A furnace, according to the previous claims, characterised in that it further comprises independent forced conveyance of air (4):

- above said material entry (42), and

- laterally to the respective side walls (43).

4. A furnace, according to the previous claims, characterised in that downstream of said combustion chamber (2) there is a post-treatment chamber having the function of smoke post-combustion and/or decantation and heat exchange with heat regeneration piping bundle (8).

5. A furnace, according to the previous claim, characterised in that the access to said post-combustion chamber (8) is obtained by an upper opening opposed to a baffle plate projecting into the combustion chamber (9).

Ansprüche

1. Verbrennungsofen besonders für Abfall, mit einer Struktur für das Vorrücken des Abfallmaterials im Brennraum (2), mit einem Boden mit abfallenden Sektoren (21, 22, 23, 24, 25) überlappt von einziehbaren Vorrückelementen (32, 33, 34) mit einer Hin- und her-Bewegung (3) mit einer Schiebefunktion, um das Verbrennungsmaterial zu einer unterhalb gelegenen Fläche zur Aschenentladung (25) zu bewegen, wobei Kühlungsluftstromdüsen unter Druck im Brennraum vorgesehen sind,, gekennzeichnet dadurch, dass,

- unmittelbar am Materialeingang und darunter, in dem betreffenden Brennraum, ein erstes Luftstrommittel (5) mit einer Reihe von Luftdüsen (51) des weiteren vorgesehen ist, wobei besagte Reihe von Luftdüsen (51) in der Lage ist, den Staub von dem gröbsten Staub zu trennen;

- eine zweite Trenn- und Staubwerf-Luftdüse (4) von unterhalb des Materialvorrückgitters oder -stufen (21,22,23,24) des weiteren vorgesehen (41) ist.

2. Ofen nach dem vorherigen Anspruch, gekennzeichnet dadurch, dass der Verbrennungsofen einen Hitzerückgewinnungs-Transport (62) mit Flüssigkeitskühlungs-Flüssigkeit umfasst, die dadurch erhitzt wird, dass sie die feuerfesten Seitenwände (61) von besagten abfallenden Sektoren und die Brennkammerseitenwände in Rohrleitungen (6) durchquert und dann in einen Hitzeregenerator einer Nachverbrennungskammer (8) befördert wird.

3. Ofen nach den vorherigen Ansprüchen, gekennzeichnet dadurch, dass er des weiteren einen unabhängigen gezwungenen Lufttransport (4) umfasst:

- oberhalb besagten Materialseingangs (42), und

- seitlich von den betreffenden Seitenwänden (43).

4. Ofen nach den vorherigen Ansprüchen, gekennzeichnet dadurch, dass unterhalb von besagtem Brennraum (2) eine Nachbehandlungskammer mit der Funktion der Rauchnachverbrennung und/oder Dekantieren und des Wärmeaustauschs mit einem Hitzeregenerations-Rohrleitungs-Bündel (8) vorhanden ist.

5. Ofen nach dem vorherigen Anspruch, gekennzeichnet dadurch, dass der Zugang zu besagter Nachverbrennungskammer (8) durch eine obere Öffnung gegenüber einer Ablenkplatte erfolgt, die in den Brennraum (9) hineinragt.

Revendications

1. Four à combustion particulièrement pour des déchets, du type pourvu d'une structure pour l'élévation des déchets jusqu'à la chambre de combustion (2), ayant un sol avec des zones en escalier (21, 22, 23, 24, 25) recouvert par des éléments d'élévation rétractables (32, 33, 34) avec un mouvement alternatif de va-et-vient (3) ayant une fonction poussoir pour faire avancer le matériau de combustion vers une zone en aval pour la coulée de cendres (25), dans lequel les moyens de refroidissement par jet d'air sous pression sont pourvus dans la chambre de combustion, caractérisé en ce que,

- juste à l'entrée du matériau et en-dessous, dans la chambre de combustion respective, un premier moyen de débit d'air (5) avec des séries de diffuseur d'air (51) est en outre pourvus, ces séries de diffuseur d'air (51) pouvant séparer la petite poussière de la plus grande poussière;

- une seconde séparation et des moyens d'écouler la poussière par jet d'air (4) au-dessous du grill ou des marches d'élévation du matériau (21,22,23,24) est en outre pourvus (41).

2. Four, selon la revendication antérieure, caractérisé en ce que le four à combustion comprend un conduit de récupération de la chaleur (62) avec un liquide de refroidissement qui est chauffé en passant à travers les murs latéraux réfractaires (61) de ces secteurs en escalier, les murs latéraux de la chambre de combustion en tuyaux (6), et qui est ensuite transporté dans un régénérateur de chaleur d'une chambre de postcombustion (8).

3. Four, selon les revendications antérieures, caractérisé en ce qu'il comprend en plus un transport d'air forcé indépendant (4):

- au-dessus de cette entrée du matériau (42), et

- latéralement aux murs latéraux respectifs (43).

4. Four, selon les revendications antérieures, caractérisé en ce qu'en aval de cette chambre de combustion (2) il existe une chambre de post-traitement ayant la fonction de postcombustion de fumée et/ou décantation et un changement de chaleur avec une unité de canalisation de régénération de chaleur (8).

5. Un four, selon la revendication antérieure, caractérisé en ce que l'accès à ladite chambre de postcombustion (8) est obtenu par une ouverture supérieure opposée à une plaque déflectrice se projetant sur la chambre de combustion (9).

Drawing