FR2683546A1 - Process for the manufacture of a solid fuel material from urban waste - Google Patents

Abstract

Process for the manufacture of a solid fuel material from urban and/or industrial and/or agricultural waste. The said waste, which is free from contaminating metallic materials and glass, is ground to obtain a granulated or stick-shaped product which contains quicklime combined with the original water to form a calcium hydroxide which is as little carbonated as possible during the process and the treatment with steam at pressures of between 1 and 20 atmospheres. A subsequent drying is then performed with CO2-free hot air at temperatures of between 100 and 200@C so that the moisture decreases in relation to the original moisture from 1.5 to 1% by weight. Application especially to the treatment of household rubbish.

Description

The subject of the present invention is a method for manufacturing, from

  urban solid residues (R S U) and industrial solid residues similar to urban residues (R.S I A U), a material capable of being used as fuel in thermoelectric plants, cement works, etc. Nowadays, with the increase of the population, there is an increasing problem of the elimination of all types of industrial manufacturing residues in mines, industries, as well as the elimination of urban solid residues and residues industrial solids comparable to urban residues; urban solid residues which can be estimated at a minimum of 1 kg per person per day In the case of Spain, it is possible to quantify this quantity at

  some 14 million tonnes per year.

  The lack of landfills for garbage and the problems they cause, as well as the lack of fuel are two problems that arise today In order to offer an acceptable solution to these problems, it is proposed to transform the solid residues solid and industrial solid residues comparable to urban residues after grinding and elimination of glass, metallic elements

  and humidity and, after carrying out a heat treatment

  chemical, into a shaped solid product capable of being transported and stored and which can be used as fuel in thermoelectric plants, cement works and

similar industries.

  There are many patents which carry out the pyrolysis of organic residues and carry out the mixing of carbonized products as in the French patent publication 2 376 894 of 08 09 78 and also the publication 2369505-7806 0 Similarly, the combustion of organic materials in a fluidized bed has been the subject of a patent on behalf of the

  NIPPON STEEL CORP under NOJP 53049001 dated 04 05 78.

  The products of combustion are polymerized and pyrolyzed with the addition of other fuels by means of an auxiliary burner. In some cases, limestone is added as desulfurizer and slag eliminator, as in US patent 4078914 dated 14 03 78 and in US patent 410386 of 20 09 89 with drying preceding the pyrolysis at a temperature of 240 to 750 ' F However, it is not specified when this process can be used to make compost, since it is possible to conceive that it is only a

  partial solution in patent US 356224 of 24 05 89.

  The use of pressurized steam to recover the latent heat so as to dry the residues to perform incineration without using additional fuel, at super critical temperatures and supercritical pressures,

  is described in US patent 294424 of 09 01 89.

  It is also not necessary to take into account the process of incineration of US patents such as 176782 of 01 04 88 or US patent 180879 of 13 04 88 or the

US patent 293546 of 03 01 89.

  In certain processes such as that of patent US 399295, a pre-drying is carried out which reduces the humidity to a value of between 8 and 10% by compression or briquetting as originality The melting of the ash obtained is claimed in US patent 132058 of 20 03 80, which offers combustion in a fluidized bed at high temperatures and

passage through the ashes.

  The use of a reduction in atmospheric pressure allows a positive air flow and avoids the problems for the personnel The use of limestone as purifier of the exit gases is used in the patent EP

2846032 of 30 04 80.

  In Italian patent 105230 of 28 10 85, urban residues are pulverized and are dried to a predetermined level to avoid the production of fungi and possible fermentations Certain chemicals are added to avoid the production of toxic gases in the subsequent combustion of product produced in the form of pellets. In summary, among the hundred patents studied, the majority ends with the use of incineration

direct from urban waste.

  In some cases, the outlet gases are purified using limestone, in particular to remove the 502 In various cases, urban residues are used to obtain methane and hydrogen by biocatalysis In many cases, pyrolysis The fluidized bed and the preliminary separation of metals have been patented profusely for the production of energy in boilers, directly and without other preliminary treatments. The preliminary drying is carried out by the formation of briquettes or shaped products.

  various in the aforementioned Italian patent.

  French patent application 2472 421 describes a process for treating household waste to transform it

in artificial aggregates.

  For this purpose, the metallic elements are eliminated and a reaction is produced on the resulting mass, which can contain 30% of cellulose and include humidity between 20 and 50% by using quicklime and / or a calcium salt. at a temperature between 250 ° C. and 450 ° C., so that a pulverulent product is obtained, which is agglomerated by compression with the prior addition of a binder to form granules The same patent 2472421 also indicates that the granules are subjected to a final or subsequent heat treatment at temperatures between 1500 ° C. and 350 ° C. for a time sufficient to heat them to the core. As a binder, it is recommended to use a mixture of monocalcium phosphate, lime, urea. , casein, bone jelly and polyvinyl acetate The patent indicates that fillers such as industrial residues, resins and silicates can be incorporated. However, this patent does not offer or claims use like this

  demand as combustible material.

  Regarding the use of combustible materials for boilers, there are many patents that use household waste, but in no case do they

  use drying, with the exception of GB 1597443 of 09-

  09-81, in which, following a ballistic classification followed by humidification and drying, a pelleting is carried out with an agglomerant of polyethylene and of lignite In the patent GB 1604948 of 16-12-81, metals and also plastics and glass are also separated, and alcohols are used

  obtained by fermentation as fuel.

  The processes according to the techniques explained above

  above are not completely satisfactory.

  Particularly due to the fact that the use of energy for the elimination of water is lost, and that the corrosive properties of certain gases which arise during combustion are increased, such as for example 502, N Ox and HC 1, whereas in the present application, they combine with the calcium hydroxide contained in the resulting material and thus make it possible to reduce the possible corrosions by the elements heated in steam boilers, while reducing the presence of compounds possible aromatic contaminants, organic products, biphenols and chlorinated compounds, such as furans and dioxynes, as is desirable to make a fuel for power plants

thermoelectric.

  On the other hand, the biological stability of the product is important since its prior contaminating potential

  is eliminated and remains odorless.

  The object of the present invention is to provide a process which makes it possible to obtain a material which exhibits, as has been said, an optimal combination of chemical and physicochemical properties which are particularly useful for its use as a material fuel for power stations, cement factories, etc. The process according to the invention will now be described for manufacturing, from urban solid residues and industrial solid residues comparable to urban residues,

combustible material.

  The solid residues are crushed, after elimination of the ferro-magnetic, they are then crushed in smaller dimensions, the glass and the paramagnetic metals are eliminated and in a worm, one incorporates quicklime and steam water A drying is then carried out between 1000 C and 2000 C, so that the maximum temperature is lower than the ignition point of combustible materials which may exist in urban residues, particularly if these are already partially dried out, this is ie their water content is less than 1% The outlet temperature of the drying oven must be close to the boiling point of water, 1000 C, in order to obtain

  maximum drying performance at normal pressure.

  The material obtained is then granulated and can be used as fuel in power plants with the advantages that it does not contain moisture, that it is stable, odorless, can be transported, is not likely to produce exaggeratedly toxic products and helps reduce corrosion of the steam production system in thermal power plants The ash obtained during combustion can be used for the manufacture of cement (as raw material) to purify

  fumes or as additives to Portland cement.

  The method according to the invention is characterized in that solid urban residues and solid industrial residues similar to urban residues are mixed without containing contaminating metallic materials or glass with a powdered mineral product which contains calcium oxide . The mixture thus obtained is treated with steam at a high temperature of between 100 ° C. and 200 ° C. in order to destroy the organic structure of the materials making up urban or industrial solid residues, proteins, fats and mainly hydrates of carbon, so as to subsequently facilitate shaping by passing between rollers intended to increase the density and facilitate subsequent drying which is carried out in a rotary kiln having internal helical walls which facilitate the internal progression of the material The drying is carried out by means of hot air, which does not contain C 02, and which is produced in an exchanger with water vapor, by means of which the carbonation of the calcium oxide formed by the reaction of water is avoided with quicklime and which helps maintain

  the chemical-biological properties of the material.

  According to the invention, this means that the combination of heat treatment with quicklime, the shaped material obtained by low pressure lamination of a mixture of detritus mixed with quicklime, and a second process for pressure granulation of the product. obtained as a result of the heat treatment, confer the properties necessary for transport and storage, such as density, absence of odor, optimal size and absence of biologically degradable products, etc. It has been found that, surprisingly, this set of operations makes it possible to obtain a combustible product which has biological inertia, a notable reduction in the possibilities of corrosion in combustion plants.

  and a significant reduction in the production of polluting gases.

  Due to their lime content, ash can be used to remove gases in purification systems, as a raw material in the manufacture of cement, with reduced energy consumption or as a material

  pozzolanic which can be added to Portland cement.

  The lime which can also come from calcined dolomites, that is to say of which magnesium oxide is not precisely a disadvantage, has a percentage which oscillates between 4 and 8% with a dosage preferably of the order 5% dry matter The fact that the material, urban or industrial residue comparable to an urban residue, is contaminated bacteriologically, is not a drawback for its use, since the sterilizer process for temperatures or vapor pressures of water used, by addition of quicklime and by drying in 2000 later,

does not prevent any vital process.

  The invention will be better understood on reading the

  description which follows and refers to the attached drawing for

  explain how the treatment of solid urban or industrial residues comparable to urban or agricultural residues is carried out, with a view to their transformation into fuel

industrial or similar.

  In the present case, the conventional prior grinding treatment 1 and 2 is carried out, reducing to small dimensions, of the order of 10 cm, and magnetic separation 3 and subsequently, a new grinding 4 to dimensions of 1 cm After separation by density 5 of ceramics, glasses and paramagnetic metals, and addition of quicklime in a worm screw 6, the product contained in said screw is subjected to the action of water vapor at a temperature of 100 'C to 2000 C in the same screw 7, which has the effect of disintegrating and breaking the cell membranes of the organic part of the detritus mainly of proteins and carbohydrates, and of starting to break down the sugars and starches which they hydrolyze The screw acts simultaneously as a mixer, transporter and

compressor.

  This part of the process increases the density of the material which, after conformation, decreases the size of the system after drying and more substances are formed with a light binding or caking power, such as the passage of starches to dextrin, which allow the step which consists in passing through the rolling means without loss of shape On the other hand, the treatment with water vapor at pressures of between 0.1 and 2 N / mm 2, causes the total destruction of the bacteria , viruses and fungi and also, various contaminants that may contain urban residues Quicklime contributes to this mission and, due to the highly basic p H produced, prevents the possibility that the product after treatment of garbage can become food rodents and insects The drying temperature and the low final moisture content contribute to this anti-vital process. Then, at its exit from the worm, the material enters a series of four pairs of cylinders 8 intended to ensure rolling which are arranged in a horizontal position with spacings of between 1.5 cm, 1 cm, 0, 5 cm and 0.25 cm with the possibility of separation by means of springs placed on their axes perpendicular to the direction of passage of the material, so as to allow the passage of substances which may be large and which are not liable to be compressed These cylinders act as molding and shaping means, and

remove excess moisture.

  In this way, the density of the residues increases from 0.1 g / ml to 0.4 g / ml and, in some cases, to 1 g / ml, and the humidity decreases from 30% to 15%, the product passes then for approximately 20 to 30 minutes in a drying oven in an axial direction through said rotary tubular oven 9, placed with its axis of rotation in a substantially horizontal position, or with a slight slope in the direction of progression of the materials in the oven and with internal ramps

helical.

  The drying in the oven is carried out by means of hot air at temperatures between 1000 C and 200 'C, thanks to which carbonation of lime and contamination by Co 2 is avoided and an increase in drying efficiency is achieved , since the products of combustion of the fuel, C 02 and H 20, are not in contact and, consequently, the air is less humid The hot air causes an exchange between the residual water vapor at low enthalpy with air and thus, water vapor is used without other possible use because of its low enthalpy The product dried with a humidity of 1% can be shaped in the form of squares or circles when it leaves the screw without end using a series of rollers similar to those at the entrance 10 Conformation is facilitated by calcium hydroxide which is present and which acts as a binder together with the soaps

  formed calcium which help reduce frictional forces.

  Another variant consists in carrying out the conformation into cylinders by means of a pellet machine 11 which acts at a high pressure of the order of 600 bars. The shaped product is stored under shelter infinitely until it is used as fuel Its higher calorific value has an average value greater than 3500 kcal / kg This fuel can advantageously be used to produce steam in heating installations or also to drive steam turbines The combustion is carried out in a Conventional fluidized bed with which good thermal yields are obtained On the other hand, the ash produced can be used advantageously with energy saving since they are already partially activated and require less heat of reaction to react with the lime to give tricalcium silicates as raw material for the production of cement clinker

  Portland, as well as for the production of silica bricks

  limestones and also, as pozzolanic additives since the heat supported during combustion and formation in the presence of lime has activated the pozzolanic properties Its high lime content allows partial recycling to replace the lime added to the origin and also its use for the purification of smoke In the case of thermal power plants, this allows the content to be reduced

final in SO in smoke.

  We have given below a series of practical examples of implementation of the invention

Example 1

  A homogeneous mixture of a weight of approximately 945 kg of garbage is obtained which has an initial humidity of the order of% by weight (obtained after separation of 45 kg of scrap from an initial mass of 1000 kg of urban residues obtained directly from the landfill and also, 45 kg of glass, bricks, and various metals), 25 kg of quicklime having been added to the mixture. This mixture is treated with air and / or steam at a temperature of 1500, after which it is formed into parallelepipeds or cylinders of 1 cm in width or radius with a length of approximately 5 cm. , using a horizontal system of shaping rollers The mixture undergoes a water loss of 15% as a result of which, the weight of this mixture at the inlet of the oven is 795 kg during a

drying at 100 'C-200' C.

  These temperatures are obtained by the passage of air from a hot current produced in turn by exchange with

water vapour.

  During a stay of 30 minutes in the drying oven, the mixture loses another 14% of water, so that the residual product reaches a mass of approximately 655 kg, with a moisture content of 1% This product could supply, during its combustion, 3895 Kcal and abandon approximately 163 kg of ash usable as pozzolan This product can be put in the form of granules to facilitate its transport and its combustion under a pressure of the order of 600 bars by means of a rotary granulating machine comprising rollers, so as to produce cylindrical bodies of approximately

  8 mm in diameter and between 10 and 20 mm in length.

  It is also possible to give the product different shapes by passing through a series of cylinders which shape the material in the form of parallelepipeds or cylinders of dimensions similar to those which they have to

entering the oven.

  These granules produced by either of the systems burn at temperatures above 8500 for a time greater than 2 seconds and with a minimum of oxygen of 6% so as to destroy or prevent the formation of chlorinated toxic compounds. such as dioxynes or furans on a fluidized bed to produce water vapor in a boiler at temperatures suitable for driving a steam turbine which operates an alternator to produce electrical energy Water vapor with a lower enthalpy is recycled for the treatment and drying of the ash produced and can also be partially reused due to its lime content, as well as as decontamination or purification material for combustion gases such as SO, N Ox and the dioxynes and for them

uses cited above.

Example 2

  In this case, we start from 1000 kg of urban waste with a humidity of 25% from which 58 kg of scrap metal, 60 kg of glass and 20 kg of paramagnetic metallic materials, mainly copper and aluminum, have been extracted. porcelain 30 kg of quicklime and 20 kg of ash are added in a fluidized bed. Following the shaping and drying process, the humidity is reduced to 0.75%, which gives a water loss of 249 kg and 662.7 kg of dry granules are thus obtained which allow a calorific value of 3820 kcal to be obtained with an ash content of kg.

Example 3

  A similar process is followed with respect to those indicated above in Examples 1 and 2. We start with 1000 kg of urban residues which contain a humidity of 35% by weight with 6% of scrap, 5% of glass and 5% of residues paramagnetic, porcelain, ash and bricks After adding 25 kg of quicklime and drying the remaining material to 1.5% humidity, we obtain 530 kg of granules which can have a calorific value of 3885 kg / cal in leaving an ash content of 133 kg after combustion in a fluidized bed.

Claims (7)

  1 Process for the manufacture of a solid combustible material from solid urban and / or industrial residues comparable to urban and / or agricultural residues; characterized in that the grinding of said residues, free of contaminating metallic materials and of glass, is carried out in order to obtain a granulated or rod-shaped product which contains quicklime combined with the original water to form a hydroxide of the least carbonated calcium possible during the process and treatment with steam at pressures between 1 and 20 atmospheres; then a subsequent drying is carried out with hot air free of C 02 at temperatures between 100 and 200 ° C so that the humidity decreases compared to the original humidity by 1.5 to 1 % in weight. 2 Method according to claim 1, characterized in that the solid combustible material obtained produces, during its combustion, 25% of ash and more 3500 kcal / kg.   3 Method according to claim 1, characterized in that the calcium oxide can be used with also magnesium oxide.   4 Method according to claims 1 and 3,   characterized in that the Ca O content is of the order of 5%   by dry weight of urban residues.   Method according to any one of   previous claims, characterized in that   introduces the ash obtained into combustion on a fluidized bed so as to reduce the amount of lime added to the residues. 6 Method according to any one of   Claims 1 to 4, characterized in that the ashes   obtained during combustion are used as material   first to make cement clinker.   7 Method according to claims 1 to 4,   characterized in that the ash obtained during combustion is used as a pozzolan-forming material.   8 Method according to one of claims 1 to 4,   characterized in that the ash from the fluidized bed combustion of this fuel is used as a gas purifying agent to remove 502, N Ox and furan or dioxyne.   9 Method according to claim 1, characterized in that, to carry out the granulation of the product, conformation cylinders are used with intermediate spaces 1.5 to 0.5 cm.   Method according to claim 1, characterized in that the combustible material is used in the form of   fluidized bed in a combustion plant.