IE914344A1 - Procedure for the manufacture of a solid combustible¹material based on solid urban and/or industrial waste¹assimilable to urban and/or agricultural waste - Google Patents

Abstract

Prodn. of solid combustible material base don solid town and/or industrial waste, which can be assimilated into town and/or agricultural waste, involves (a) grinding waste freed from contaminating metallic material and glass, to give a prod. as granules or pieces contg. lime in combination with the original water, so that Ca(OH)2 is formed during the process and treatment with steam under pressures of 1-20 atmos., with as little carbonisation as possible, and (b) drying in air at 100-200 deg.C, without CO2, so that the original moisture content is reduced to 1.5-1 wt.%.

Description

PROCEDURE FOR THE MANUFACTURE OF A SOLID COMBUSTIBLE MATERIAL BASED ON SOLID URBAN AND/OR INDUSTRIAL WASTE AND ASSIMILABLE TO URBAN AND/OR DESCRIPTION The present invention refers to a procedure to manufacture, based on solid urban waste (S.U.W.) and solid industrial waste assimilable to urban waste (S.I.W.A.U.), a material that can be used as fuel for electrical power plants, cement factories, etc..

Today, with the increase in population there is a proportional increase in the question of the elimination of all types of waste material from industrial production in mining, industry and also the elimination of solid urban waste (S.U.W.) and solid industrial waste assimilable to urban waste (S.I.W.A.U.),- solid urban waste (S.U.W.) is estimated at a minimum of 1 kg per person/day. In the case of Spain, this amount can be calculated at 14xl06 t per year.

The lack of rubbish tips and the problems these involve, as well as the lack of fuels, are two problems that arise today. In order to offer an acceptable solution for these problems it is proposed to transform solid urban waste (S.U.W.) and solid industrial waste assimilable to urban waste (S.I.W.A.U.), following grinding and the removal of glass, metal elements, humidity and undergoing a thermochemical treatment, with solid, shaped material that can be transported and stored, and which can be used as fuel in electrical power plants, cement factories, and similar.

STUDY OF PREVIOUS PATENTS There are various patents that carry out pyrolysis of organic residues and mix carbonized products, such as the French 2376894 dated 78.09.08 and also 2369505-7806.0. Also the burning of organic material on a fluid bed is patented by the NIPPON STEEL CORP, under patent JP 53049001 dated 78.05.04. The products of combustion are polymerized and pyrolized, adding other fuels with an auxiliary burner.

In some cases limestone is added as a desulphurer and slag remover, as in US patent 4078914 dated 78.03.14 and US patent 410386 of 89.09.20 with drying prior to pyrolysis at 240-700eF. However, this is not cited when used to make conpost since we believe that this is only a partial solution in US patent 356224 of 89.05.24. The use of water steam under pressure to recover latent heat in order to dry ,ε 914344 - 2 supercritical temperatures and subcritical pressures, is covered in US patent 294424 of 89.01.09.

Neither do we consider the incineration process in US patents such as 176782 dated 88.04.01 nor US 18.0879 of 88.04.13, nor US 293546 of 89.01.03.

In some processes such as that of US patent 399295, pre-drying is carried out that reduces humidity to 8-10% by compression and briquetting as an original item. The fusion of the ash obtained is claimed in US patent 132058 of 80.03.20, using combustion on a filter bed at high temperatures and passing through the ash.

The use of an atmospheric pressure reduction allows a positive air flow and avoids problems for personnel. The use of limestone as an outlet gas scrubber is used in patent PB 2846032 dated 80.04.30.

In the Italian patent 105230 of recent date 85.10.28, urban waste is pulverized and dried at a predetermined level to avoid the production of fungi and possible fermentations. Specific chemical products are added to avoid the production of toxic gases in later combustion of the pelleted product.

To summarise, from same 100 patents previously examined, the majority end by using direct incineration of urban waste.

In some cases the outlet gases are purified with limestone, mainly to eliminate the SO2. In various cases urban waste is used for the biocatalysis producers of Methane and Hydrogen. Pyrolysis is used in many cases. The filter bed and prior separation of metals are profusely patented for the production of energy in direct boilers and without other treatments. Prior drying is carried out by briquetting or in a scarcely defined form in the mentioned Italian patent.

The application for French patent N° 2472.421 describes a treatment process for urban rubbish to artificial aggregates.

To do this, the metallic elements are removed and a reaction is caused in the resulting mass that may have 30% cellulose and humidities between 20 and 45%, with quicklime and/or calcium salt at temperatures of between 250®C and 450°C, so that a dust-like product is obtained that is agglomerated by compression after the addition of a binder to form granules. The same patent N* 2472.421 also indicates that the granules are subjected to a final thermal treatment, or following the above, at temperatures between 150’C and 350°C with sufficient duration to heat them completely through. The preconceived - 3 binder is a mixture of monocalcium phosphate, chalk, urea, casein, bone gum and polyvinyl acetate. The patent indicates that charges can be incorporated such as industrial waste, resins and silicates. However, it does not preconceive or claim its use as in our case as combustible material.

If combustible materials are used as boilers, there are numerous patents that use urban waste, but in no case do they use drying except in British patent 1597443 of 81-09-09 in which, following ballistic classification followed by humidification and drying, pelleting with a polyethylene and lignite agglomerate. In British patent 1604948 of 81.12.16 there is also a separation of metals and also of plastics and glass, and the alchols are used obtained from the fermentation as fuels.

The procedures in accordance with the techniques explained above are not completely satisfactory. Particularly because the use of energy to eliminate the water is lost and this increases the corrosive properties of some gases given off during combustion, such as SO2, NOx and HCl meaning that in our case they combine with the Calcium Hydroxide contained in the resulting material thus diminishing the possible corrosion by heating elements in the steam boilers, while decreasing possible contaminating aromatic, organic, biphenol and chlorate compounds such as furanes and dioxines, as is desirable in a fuel for electrical power plants.

On the other hand, its biological stability is important since its previous contaminating potential is eliminated and it remains odourless.

The present Invention has the objective of offering a procedure that allows a material to be obtained that presents, as we have said, an optimum combination of biological and physical chemical properties that are particularly useful for its use as a fuel material for electrical power plants, cement factories, etc.. - 4 PRQCBDURB FOR THB MANUFACTURE OP A COMBUSTIBLE MATERIAL BASED ON SOLID URBAN AND SOLID INDUSTRIAL WASTE ASSIMILABLE TO URBAN WASTE Solid urban waste (S.U.W) and solid industrial waste assimilable to urban waste (S.I.W.A.U) are ground, ferro-magnetic materials are removed, it is then ground to smallers size, glass and para-magnetic materials are removed, and quicklime and water steam added using a worm. It is dried between 100‘C and 200’C so that the maximum temperature is less than the flame point of combustible materials that may be found in the urban waste, particularly if they are already partially dried, i.e. their water content is lower than It. The outlet temperature from the drying oven must be near to the boiling point of water - 100°C to obtain maximum output from drying at normal pressure.

This material is reground and can be used as fuel in electrical power plants with the advantages of: containing no humidity, being stable, odourless, transportable, not giving off or having a minimum of toxic products during combustion and decreasing corrosion in the steam producing system in power plants. The ash obtained from combustion can be used to manufacture cement (as a raw material), to clean smoke or as additives for Portland cement.

The procedure according to the invention is characterized because solid urban waste (S.U.W.) and solid industrial waste assimilable to urban waste (S.I.W.A.U.) are mixed without containing contaminating metallic materials and glass, with a powdered mineral material containing calcium oxide.

The mixture thus obtained is treated with water steam at high temperature, l00eC - 200eC, in order to destroy the organic structure of the materials composing the solid urban waste (S.U.W.) and solid industrial waste assimilable to urban waste (S.I.W.A.U.), proteins, fats and mainly carbohydrates, and to make easier their later shaping through lamination between rollers, in order to increase their density and make easier their later drying which is carried out in a rotating oven with internal helicoidal track to aid the internal advance of the material. Drying is carried out by hot air without CO2 and causes an exchange with the water steam, thus avoiding the carbonating of the Calcium Hydroxide formed by the reaction of the water with the quicklime, and maintaining the chemical-biological properties of the materials. - 5 According to the basis of the invention, this indicates that the combination of the thermal treatment with quicklime, the shaped material obtained by lamination under pressure from a mixture of waste materials ground with quicklime, and from a second grinding process under pressure of the product obtained following thermal treatment, confers the properties necessary for its transport and storage such as density, absence of odour, optimum size, no biological degradables, etc..

Surprisingly, it has been noted that this group of operations allows a combustible product to be obtained that presents biological inertia, a notable decrease in corrosion possibilities for combustion installations and an important decrease in the production of polluting gases. Due to their lime content, the ash may be used to eliminate gasee in depuration systems, as raw material in the production of cement, with a decrease in energy consumption, or as pozzolanic material for adding to portland cement.

The lime may also come from calcinated dolomites, i.e. its content in Magnesium Oxide is not exactly a problem. Its percentage will vary between 4% and 8%, with contents of 5V of dry material being preferred. That the material - urban waste or industrial waste assimilable to urban waste - is bacteriologically contaminated, is not a problem for its use since the sterilizing process using temperatures or water steam pressure, the addition of quicklime and the later drying at 200°C, impede any vital process.

In order to understand the invention, a description is given below with reference to the attached drawing, for carrying out the treatment of solid urban waste, solid industrial waste assimilable to urban and/or agricultural waste to transform it into industrial fuel or similar.

In this case, the classic, prior treatment is carried out of grinding 1 and 2, breaking down to small sizes of some 10 cm and magnetic separation 3, and later a further grinding to sizes of l cm 4. Following density separation 5 of ceramics, glass and paramagnetic metals, and combination with quicklime in a worm 6, the product in the worm undergoes the action of water steam at 100*C-200*C in the same worm 7, which desegregates and breaks down the cellular membranes in the organic part of the waste, principally proteins or carbohydrates. The worm acts simultaneously as a mixer, transporter and compressor. - 6 This part of the process increases the density of the material that, after shaping, decreases the size of the prior drying system, and furthermore substances are formed with some slight binding or agglutinant powers - such as the change of starches to dextrines that permit the step through the laminators without loss of shape. Furthermore, treatment with water steam at pressures of 0,1 - 2 N/mm2 causes the total destruction of bacteria, viruses and fungi and other contaminating organisms that are or may be contained in the urban waste. The quicklime contributes to this mission and according to the strongly basic pH produced inpedes the possibility of the waste serving after treatment as food for rodents or insects. The drying temperature and low final humidity content contribute to this antivital process.

Thereafter at the end of the worm the material enters a series of four pairs of lamination cylinders 8 in a horizontal position, with spaces of 1,5 cm, 1 am, 0,5 cm and 0,25 cm, with the possibility of separation by spring action with springs placed on their axis perpendicularly to the direction of passage of the material, in order to allow the passing of possible voluminous and non-compressible substances. These cylinders act as molder-shapers and remove excess humidity.

In this manner the density of the waste increases from 0,1 g/ml to 0,4 g/ml and in some cases to 1 g/ml, and humidity decreases from 30% to 15%, the product then goes for some 20 to 30 minutes to a drying oven in an axial direction through the said rotating tubular oven 9, placed with its rotating axis in a practically horizontal position, or with a slight slope in the direction of advance of the materials in the oven, and with internal helicoidal paths.

Drying in the oven is carried out using hot air at temperatures of 100°C to 200°C, thus avoiding carbonation of the lime and contamination by CO2 and an increase in drying output since the products of fuel combustion, CO2 and H2O, are not in contact and therefore the air is less humid. The hot air causes an exchange of residual water steam of low enthalpy - air and thus the water steam is used without any other possible use due to its low enthalpy. The dried product, with a humidity of 1%, can be formed into squares or rounds when it leaves the worm using a series of rollers similar to those at the entrance 10. Shaping is aided by the Calcium Hydroxide - 7 present that acts as a binder, simultaneously with the calcium soaps formed that aid in decreasing drawing friction.

Another variation is the shaping in cylinders using a granulator ll that acts at high pressure of some 600 bars. The shaped product is stored under cover indefinitely until used as fuel. Its upper calorific power is in the order of an average of more than 3.500 Kcal/kg. This fuel may be used to advantage to produce water steam for heating use or also to move steam turbines. Combustion is carried out on a conventional fluid bed which gives good thermal outputs. Furthermore, the ash produced can be used to advantage, with thermal energy saving since they are already partially active and need less reaction heat in order to react with lime to produce tricalcium silicates as raw material for the production of portland cement clinker, also for the production of silico-calcareous bricks, and also as a pozzolanic additive since the heat it has undergone during combustion and shaping, together with its lime content, have activated its pozzolanic properties. It high lime content allows partial recycling to substitute the lime originally added and also its use in smoke depuration. In the case of power plants, it would decrease the final SO content in the smoke.

Reference is made below to a series of practical exaiiples of the invention: Example 1 A homogeneous mixture of waste is obtained with a weight of some 945 Kg with an initial humidity of some 30% by weight (obtained after having separated 45 Kg of scrap from the initial mass of 1.000 Kg of urban waste, obtained directly from waste collection and a further 45 Kg of glass, bricks, tile and various metals), to which has been added 25 Kg of quicklime.

This mixture is treated with air and/or water steam at 150°C and thereafter is shaped into parallelpipes or cylinders with 1 cm side or radius x 5 cm long approximately - using a horizontal system of shaping rollers. The mixture undergoes a water loss of 15%, with which the weight of the same on entering the oven is 795 Kg during drying at 100’C-200°C.

These temperatures are obtained by the passage of hot air produced, in turn, by exchange with water steam. - 8 During the 30 minutes stay in the drying oven a further 14% of water is lost and thus the resulting product has a mass of 655 Kg approximately with a humidity content of 1%. During combustion this product can supply 3.895 Kcal and leave some 163 Kg of ash that may be used as pozzolan. This product can be ground for ease of transport and combustion under a pressure of some 600 bars using a rotating inline roller granulator, to form cylindrical bodies some 8 mm in diameter and with a length of between 10 and 20 ran.

It is also possible to give them the desired form by making the dried material pass through a series of cylinders that shape the material to the size required in parallelpipe or cylindrical shapes of similar sizes to those on entering the oven.

These granules produced by either system are burned at temperatures above 850’C for more than 2 seconds and with 6% minimum oxygen, in order to destroy or impede the formation of chlorate toxic conpounde such as dioxines or furanes on a fluid bed to produce water steam in a boiler at tenperatures appropriate to move a steam turbine that activates an alternator in order to produce electrical energy. The water steam with less enthalpy is recycled for the treatment and drying of the ash produced and may also be partially reused due to its lime content, as a decontamination or purification material for combustion gases such as SO, NOx and dioxines, and for the uses cited previously.

Example 2 In this case, starting with 1.000 Kg of urban waste with a humidity of 25%, 58 Kg of ferro-magnetic scrap, 60 Kg of glass and 20 Kg of paramagnetic metallic materials, mainly copper and aluminium together with porcelains, have been removed. 30 Kg of quicklime and 20 Kg of fluid bed ash have been added. After the shaping and drying process has decreased humidity to 0,75%, giving a water loss of 249 Kg, 662,7 Kg of dried granules are obtained that offer the possibility of producing 3.820 Kcal and giving 167 Kg of ash.

Example 3 A similar process is followed to those indicated in examples 1 and 2. It starts with 1.000 Kg of urban waste containing 35% humidity by weight and a content of 6% ferric scrap, 5% glass and 5% paramagnetic scrap, porcelain, ash and brick. Following the addition of 25 Kg of quicklime and drying of the remaining material to 1,5% ,E 914344 - 9 humidity, 530 Kg of granules are obtained that can produce 3.885 Kcal leaving an ash content of 133 Kg following combustion in a fluid bed.

Having sufficiently described the nature of the invention and the manner of carrying it out in practice, it should be stated that the dispositions indicated above and shown in the attached drawings may be modified in their details provided their fundamental principle is not altered.

Claims (12)

1. Procedure for the production of solid combustible material based on solid urban waste and/or industrial waste assimilable to urban and/or agricultural waste; characterized because the said waste, cleaned of contaminating metallic materials and glass, is ground to obtain a granulated or stick-shaped product containing quicklime combined with the orginal water forming calcium hydroxide the least carbonated possible during the process and treatment with water steam at pressures of 1 to 20 atmospheres; with later drying being carried out with hot air without CO 2 at temperatures between 100 and 200°C, so that humidity decreases from the original 1,5 to 1% by weight.

2. Procedure according to claim 1 characterized because the solid combustible material obtained produces during combustion 25% ash and more than 3500 Kcal/kg.

3. Procedure according to claim 1 characterized because the calcium oxide can also be used with magnesium oxide.

4. Procedure according to claims 1 and 2 characterized because the content of CaO is some 5% by dry weight of urban waste.

5. Procedure according to any of the above claims, characterized because the ash obtained from combustion on the fluid bed is incorporated in order to reduce the content of quicklime added to the waste.

6. Procedure according to any of the claims 1 to 4 characterized because the ash obtained during combustion is used as raw material to make cement clinker.

7. Procedure according to claims 1 to 4 characterized because the ash obtained from combustion is used as pozzolanic material.

8. Procedure according to claims 1 to 4 characterized because the ash from the fluid bed combustion of this fuel is used as a purifying agent for combustion gases to eliminate S0 2 , NOx and Furanes or dioxines.

9. Procedure according to claim 1 characterized because in order to granulate the product shaping cylinders are used with intermediate spaces of 1,5 to 0,25 cm.

10. Procedure according to claim 1 characterized because the combustible material is used in a fluid bed fuel installation.

11. Procedure according to any of the preceding claims, substantially as described herein.

12. Combustible naterial produced by a procedure according to any of the preceding claims.