WO1999016611A2

WO1999016611A2 - Method and apparatus for the essentially adiabatic compaction of waste materials to ashlars of homogeneous material

Info

Publication number: WO1999016611A2
Application number: PCT/IT1998/000258
Authority: WO
Inventors: Roberto Spina; Francesco Maria Piccari
Original assignee: Roberto Spina; Francesco Maria Piccari
Priority date: 1997-09-30
Filing date: 1998-09-30
Publication date: 1999-04-08
Also published as: IT1297059B1; WO1999016611A3; ITRM970587A1; EP1042117A2; AU9366598A

Abstract

In order to produce ashlars or quarry-stones and/or building cut stones by using municipal and/or industrial solid wastes as raw material possibly mixed with inert quarry materials, an essentially adiabatic compression of such waste materials is carried out. This can be made by using a hammer (14) that strikes the material so as to cause a very quick reduction of the total and specific volume without internal heat exchange among the components of the original material. The ashlar obtained has the characterisitcs of an elastic solid.

Description

^{AD,ABAΉC COMPAC}™^{N OT}™^«*■»""TO

The present invention relates to the environment- friendly recovery of the cast off, exhausted dumps as well as the reuse of wastes as inert filler. Particularly, this invention proposes the production of ashlars or quarry-stones and/or building cut stones by using municipal and/or industrial solid wastes as raw material possibly mixed with inert quarry materials . The method according to the invention provides the compression of such waste materials by dynamic strokes which allow the total, specific volume of such materials to be quickly reduced without internal heat exchange among the original components of the waste materials. Such a method meets two strongly demanded requirements at the same time.

It is well known how the problem of wastes is heavy and how it is difficult to find new places for dumps capable of holding more and more high volumes of wastes . The environmental shock associated to such dumps is hard to be controlled as their filling time is still short.

Another problem of increasing importance relates to the exhausted quarries that among other things cause environmental disaster as far as the geology and both the vegetable and animal ecologies is concerned. In such cases the restoration of the environmental conditions is very difficult and expensive as a considerable handling of inert filling materials from very far places is requested.

One object of the invention is to provide a method of compacting wastes that allows a better dump filling efficiency by unit volume so as to both extend the life of the dumps and reduce the need of providing some new one .

A second object of the present invention is to provide inert filling materials at low cost and in large amount so that they can be used for the restoration of the exhausted or in any case deserted quarries .

A third object of the invention is to provide a method of reusing and/or reopen old dumps that had been closed as they were completely filled, thus improving the use of the place . Still another object of the invention is to provide a method of providing ashlars that can be used as inert materials to be accumulated in a quarry, as building materials for civil and/or industrial and/or road works, and as inert filling and/or ballast materials. Another object of the invention is to provide a method capable of transforming municipal and/or industrial waste materials into ashlars provided with a certain degree of elasticity.

These and other objects will be more readily understood from the following detailed description with reference to the accompanying drawings that show only by way of example schematic operating blocks and a preferred embodiment . In the drawings :

Fig. 1 is a schematic plan view of the whole apparatus ;

Fig. 2 is a front elevation view of the same apparatus .

The method according to the invention provides the compaction of wastes and/or inert materials by a compression approaching a perfect adiabatic compression. This is obtained particularly by compacting non-toxic wastes and any inert materials mixed thereto by a stroke of a hammer, i.e. a very high compression force applied during a minute time interval .

With the same produced work, physics teaches that the power is as greater as the time interval, during which such a work is produced, is shorter. According to the invention three consecutive steps that can be described by the physics laws regarding gases, liquids and solids can be discriminated in a compression of such a type. Thereafter the reasons why the behaviour of the rubbish in bulk under quick compression can be compared in the initial step with that of a perfect gas will be briefly investigated. Then the reasons why the stroke of a hammer makes the behaviour of a perfect gas similar to that of an ideal liquid in a second step will also be explained. At last, it will be illustrated why the "real liquid" behaves as an elastic body during the last step of compression by a stroke of a hammer.

A gas is perfect when it is formed by molecules which are not bound by cohesion forces (as a result of which a perfect gas does not have any determined volume as the rubbish!) so that it is necessary that such a gas meets the following three conditions:

- compliance with the Boyle and Mariotte and the Gay-Lussac laws;

- its internal energy being a function only of temperature ; its specific heat being independent of the temperature .

These three conditions are met enough by the wastes when they are compressed almost instantaneously. In fact, the ejection of the air in the gaps among the components occurs in the first step of the hammer stroke .

A liquid is characterized by the fact that its molecules are relatively free of moving to one another but are bound by cohesion forces that constrain them to fill a determined volume. Such a liquid is said ideal when its viscosity is null .

Wastes are relatively free to slip over one another in the intermediate stroke step, however, the friction produced is rather a viscosity which is a dynamic characteristic above all of liquids.

Municipal and/or industrial wastes are usually not liquid but the compression to which they are subjected in a very short time forces them to collide in a non- destroying manner so that they are provided with a viscosity similar to wax, clay and the like. Finally, a solid is characterized in that the relative motion of its molecules is limited so that the latter tend to keep their mutual positions unchanged. Even if they show such a feature, solids may be rigid or resilient: the first ones break but do not bend, the second ones bend but do not break.

In the third compression step carried out by a stroke or a knock of a hammer, wastes are linked to one another so as to show a resistance to an external force that tends to modify their arrangement . As it is not conceivable that the ashlar obtained by such a way is a crystal (i.e. a rigid body) , it should be admitted that it is a resilient body.

Thereafter the invention will be illustrated first of all according to its theoretical aspect and then according to an embodiment of the method and the apparatus . According to the invention the compaction of wastes mixed with inert materials is carried out by causing a weight to fall within a container filled with rubbish. Such a container that will hereinafter be referred to as a die consists of vertical walls and preferably a square bottom. If "q" is the side of the bottom square and "h" the height of the die, the inside volume of the die is equal to q²h. If the die is completely filled with wastes, the initial volume of the latter is of course the same as the inside volume of the die, while the final volume after the stroke compression is that of a parallelepiped with square bottom of side "q" and height "z" which varies as a function of the ratio between the initial and final volumes, i.e. the "compression ratio" h/z.

The change of height h-z is the path covered by the hitting weight within the die, and the ratio h - z ε = h expresses the unit shortening of the waste volume during the shaping of the ashlar .

The modulus of elasticity E of a material is defined by the ratio between the unit tension σ [N/mm² or kg/cm²] to which the material is subjected, and the unit deformation ε, i.e.: a

E = — ε

Therefore, if for instance a material having E = 12 undergoes a shortening of 20% (i.e. an unit shortening ε = 0,2) , the unit tension withstanding the stroke of weight M falling from a certain height is σ = 0,2 * 12 = 2,4.

The hitting hammer makes a work L because of its kinetic energy E_c : L = P * H = E_c where P is its weight and H the difference in heights of its initial position and the mouth of the die. Moreover, such a hammer covers a further vertical path which is equal to the above-mentioned height difference h-z and accordingly makes a compression work that is the instant product of the dynamic pressure p_d by the change of volume:

W = p_d * (h-z) * q² Let assume in our case that the instantaneous pressure p_d is always constant and the instantaneous volume is always decreasing.

The final static pressure is of course the pressure exerted by weight P of the hammer on the ashlar after its stop, i.e. the ratio P/q².

Supposing the hammer of mass m and weight P is uniformly decelerated from the time it enters the die, its speed will reduce from the initial value to zero along the vertical path h-z. Physics teaches that such initial speed is:

(where g is the acceleration of gravity) . In order to calculate the deceleration "a" it is necessary to use the same formula for the change of speed of the hammer along path h-z:

where V = 0 because the hammer stops . Therefore :

V, 2gH H a = = g

2(h-z) 2(h-z) h-z As mentioned above, force F making compression work W is equal to the product of mass M of the hammer by the deceleration of the latter along path h-z:

F = M a = = P * — g accordingly:

H H

F = P g g h-z h-z Therefore, the compression work is:

W = F * (h-z) = P * * (h-z) = P * H h-z

Turning now to σ, i.e. the force per unit surface:

F 1 PH PH σ = — = — * =

^ ^ q h(l ) h

It should be noted that z/h is the waste compaction factor that depends on the nature of the wastes .

To sum up, it could be stated that the invention allows a potential energy (PxH) to be transformed into an elastic, still potential energy (σ = ε E) .

Numerical example:

In an exemplifying case according to a simulation we suppose to make a comparison with a good concrete having an ultimate tensile stress sr=600 kg/cm² and assume shape and size of the product in question such as to take into consideration the emblematic nature of this example. Therefore, after having examined several assumptions and looked for a size approaching the optimum solution as far as the capability of controlling stresses connected to size is concerned, let us assume an ashlar with a base surface of 33x33 cm. Such a surface together with a height of 33 cm would exactly refer to the concrete test pieces subjected to experimental load tests. Let us then assume a waste die with h=330 cm, z being 16.5 cm so that the ratio between z and h as well as the ratio between final volume and initial volume is equal to 1/20. After development of the calculations:

PH sr

16.5.

33x33x330 (1 -)

330

PH PH sr

359,370 x 0.95 341,402 supposing sr = 600:

PH = 341,402 x 600 = 204,841,200 kg cm. If H = 1000 cm, then P = 204.9 tons

The results are significant but far from the real facts, although the method appears certainly effective and reliable. Therefore, it should be thought about a simple real circumstance. To imagine that the compactness of wastes can be compared with that of concrete looks of course exaggerated. In fact, it is enough to say that the ratio between the inside volumes (about 13 m³) of a rubbish collecting vehicle, the so-called shark, and a garbage can is 11-12, and that such a vehicle is able to empty about 150 cans. Therefore, if a good compaction factor should take up a position in a high band, say 15-20, it is certainly wrong to make reference to concrete as a material with comparable compactness . On the basis of the experience it should be remembered that a designer would regard as ideal a soil for foundation plinths of reinforced concrete which has a sigma of about 1.5 kg/cm², i.e. a soil wherein a plinth support surface of a square meter can be loaded by 15 tons. Such a condition is certainly more representative than the former and allows the calculation to be developed by quadruplicating the reference tension as follows:

PH st =

16.5,

33x33x330 (1 -) 330

PH PH st =

359,370 x 0.95 341,402 supposing st = 6 kg/cm² :

PH = 341,402 x 6 = 2,048,412 kg cm. If still H = 1000 cm, then P = 2,049 kg

The result is such as to state in conclusion that 2.1 tons falling from a height of 10 meters in a die with a base of 33 x 33 cm² and a height of 330 cm filled with various wastes allows the behaviour of the accumulation to be tested in a representative, biyiUj-iCαuL. manner.

According to the preferred embodiment the method of the invention consists essentially of the following steps : loading wastes in a predetermined weight amount into a box-like die of metal sheet with a rectangular base and without bottom and cover; transferring the die to a hitting position where it is subjected to the stroke of a hammer with suitable weight that reduces the volume of the wastes and produces an ashlar with the same surface area of its horizontal section; hoisting the hammer from the die; transferring the die to a position where the ashlar is discharged from its bottom; transporting the ashlar discharged from the die to a finishing and/or waterproofing bath and then to a storage yard.

A preferred embodiment of an apparatus for carrying out the above-mentioned method automatically and cheaply will hereinafter be described.

The apparatus is shown in Figs . 1 and 2. As can be seen it includes a belt conveyer 2 that continuously supplies a rocking platform 4 having symmetric axis with materials from the first storage yard, such a rocking platform resting alternately on the edges of two hoppers 6 placed on the right and left so as to distribute the materials. Each hopper 6 which in turn is rocking about a symmetric axis is provided with a scale and is charged on a horizontal plane. As soon as a predetermined weight is reached, a group of sensors connected to a hydraulic circuit connected in turn to the scale switch over the discharging position of platform 4 by electrovalves and then cause the hopper to tilt to the mouth of a die 8 located under its funnel .

Said die 8 consists of a strengthened, calibrated metal sheet with a shape of truncated pyramid having internal mirror walls and is integral with another twin die 8a. As can be seen from Fig. 2, each die consists of a box-like container with four fixed walls but without top and bottom walls. Once the die is filled, it is caused to slide by a hydraulic circuit along side guides 10 from the stationary loading position C, where the bottom of the die is closed by a plunger 12 with hinged head, to the stationary stroke position B, where the bottom of the die is closed by the bed-plate of the apparatus .

Hammer 14 preferably consists of a T-shaped body the head of which slides in vertical guides formed of four tubular sections 16 suitably braced both at the top and the bottom at the height of the die . Tubular sections 16 form as a whole a hammer carrying tower 18 having a total height of about 17 meters, 10 meters of which are the path covered by the hammer when falling down, the balance being the height of the hammer and the height of the die .

A safety release retainer 20 is provided at the starting position. After the impact the hammer is caused to return to the safety retainer 20 by a rope 22 running about a pulley 24 mounted on the vertical line at a higher height. Rope 22 comes freely down together with the hammer and is put under tension and caused to return after the impact of the hammer by a counterweight system that allows the energy consumption to be reduced.

In order to facilitate the discharge of the ashlar from the die there is provided a suitable discharging device comprising in combination an upper plunger 26 capable of coming down from the top and a plunger 12 forming the bottom of the die. Such a device is located at position C to which the die is brought after the ashlar is formed. After having pushed downwards the ashlar resting on the head of plunger 12, plunger 26 moves back and goes to misalignment so as to leave the mouth of the die free .

When coming down plunger 12 meets a retainer 28 that causes its head to tilt and the ashlar to slide on an inclined plane 30 so as to reach a position in which it can be caught by a pliers. As soon as plunger 12 is disengaged from the ashlar, it rises again to reach the bottom position of the die, the mouth of which already disengaged from plunger 26 is charged by the hopper, and the cycle starts again. Meanwhile the ashlar is raised by pliers moved by a belt conveyer 32 and is brought to a finishing bath consisting of a tank containing suitable fluid products and afterwards to a storage yard.

The invention has been described according to a preferred embodiment, however, a number of modifications can be made by those skilled in the art. For example, since the product PxH allows H to be increased and P to be decreased and viceversa, the apparatus is flexible as far as height H and weight P of the hammer is concerned. This also allows the shapes and the volumes of the ashlars to be differentiated. Furthermore, the die may also be a cylinder besides a parallelepiped under the assumption that the cylinder is the projection of any open or closed, straight or oblique line from a point at infinity. It should be understood, however, that such modifications and changes are included in the scope of the present industrial invention as defined in the appended claims .

Claims

1. A method of producing ashlars or quarry-stones and/or building cut stones by using municipal and/or industrial solid wastes as raw material, characterized in that there is provided an essentially adiabatic compression of such material .

2. The method of producing ashlars or quarry- stones and/or building cut stones by using municipal and/or industrial solid wastes as raw material according to claim 1, characterized in that the compression of said waste material is carried out by the stroke of a hammer which allows a very quick reduction of the total and specific volume without internal heat exchange among the components of the original material .

3. The method of producing ashlars or quarry-stones and/or building cut stones according to claims 1 and 2, characterized in that the municipal and/or industrial solid wastes are mixed with inert quarry materials .

4. The method according to the preceding claims, characterized in that the stroke of the hammer is provided by the fall of a weight from a height into a container or die in which the waste and the inert materials have been filled.

5. The method according to the preceding claims, characterized in that said container or die has the shape of a parallelepiped.

6. The method according to the preceding claims, characterized in that the wastes contained in said die can be considered alike a perfect gas in a first step after the stroke of the hammer, a perfect liquid in a second step, and a perfect solid in a third step.

7. The method according to the claim 6, characterized in that said solid is an elastic solid.

8. The method according to the preceding claims, characterized in that the following steps are provided: loading wastes in a predetermined weight amount into a box- like die of metal sheet with a rectangular base and without bottom and cover; transferring the die to a hitting position where it is subjected to the stroke of a hammer with suitable weight that reduces the volume of the wastes and produces an ashlar with the same surface area of its horizontal section; hoisting the hammer from the die; transferring the die to a position where the ashlar is discharged from its bottom; transporting the ashlar discharged from the die to a finishing and/or waterproofing bath and then to a storage yard.

9. An ashlar or quarry-stone and/or building cut stone obtained according to the method of the preceding claims, characterized in that it can be used for filling the empty spaces excavated in the deserted quarries so as to allow an environment-friendly use as well as the conservation of natural resources .

10. The ashlar or quarry-stone and/or building cut stone according to the preceding claim, characterized in that it consists of wastes stored in a volume resisting to weather and underground agents.

11. An apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes, characterized in that it includes a belt conveyer (2) that continuously supplies a rocking platform (4) having symmetric axis with materials from the first storage yard, such a rocking platform resting alternately on the sides of two hoppers (6) placed on the right and left so as to distribute the materials, each hopper (6) being in turn rocking about a symmetric axis and provided with a scale and charged on a horizontal plane.

12. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claim 11, characterized in that as soon as a predetermined weight is reached, a group of sensors connected to a hydraulic circuit connected in turn to the scales which are provided in hoppers (6) switch over the discharging position of platform (4) by electrovalves and then cause the hopper to tilt to the mouth of a die (8) located under its funnel.

13. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claims 11 and 12, characterized in that said die (8) consists of a strengthened, calibrated metal sheet with a shape of truncated pyramid having inside mirror walls and is integral with another twin die (8a) .

14. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claims 11 to 13, characterized in that each die (8, 8a) consists of a box-like container with four fixed walls but without top and bottom walls that after its filling is caused to slide by a hydraulic circuit along side guides (10) from the stationary loading position (C) , where the bottom of the die is closed by a plunger (12) with hinged head, to the stationary stroke position (B) , where the bottom of the die is closed by the bed-plate of the apparatus .

15. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claims 11 to 14, characterized in that a hammer (14) having a T-shaped body, the head of which slides in vertical guides formed of four tubular sections (16), is located above the stationary hitting position (B) .

16. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claims 11 to 15, characterized in that said tubular sections (16) form as a whole a hammer carrying tower (18) .

17. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claims 11 to 16, characterized in that said hammer carrying tower (18) has a total height of about 17 meters, 10 meters of which are the path covered by the hammer when falling down, the balance being the height of the hammer and the height of the die.

18. The apparatus for the production of ashlars from non-toxic, non-radioactive, municipal and/or industrial wastes according to claims 11 to 17, characterized in that the ashlar is brought to a finishing bath to make it waterproof.