FR2793172A1 - Cleaning a material contaminated by residues comprises mixing it with a solid cleaning product and blunt objects - Google Patents

Abstract

Cleaning a material (22) contaminated by residues comprises bringing the material, by mixing, in contact with a solid cleaning product (21) and striking with blunt objects (20). Independent claims are also included for the following: (i) valued material obtained by the above process; (ii) solid fuel obtained by the above process; and (iii) a treatment apparatus for the above process, comprising a crusher, a rotating drum, a screen, a storage hopper, a sorting bank, and devices for transporting the material from the crusher to the rotating drum, from the drum to the screen, from the screen to the storage hopper, from the storage hopper to the rotating drum and from the screen to the sorting bank. . Preferred Features: The cleaning product is absorbent, such as sawdust, or an abrasive such as sand. The mixing is carried out in a rotating drum (1) which is loaded at one end by a supply and transport device in which the material to be cleaned and the cleaning product are supplied separately. The mixture is evacuated from the other end of the drum. The blunt objects are bars which extend the length of the drum, or balls (cannon-balls). The mixture of the material to be cleaned and the sawdust is screened to produce a valued material for the larger grain sizes and a solid fuel with the smaller grain sizes.

Description

 MATERIAL RECOVERY PROCESS.

 The present invention relates to the recovery of soiled material for recycling. It also relates to a substitute combustible product resulting from this recovery, preferably for cement factories.

 Whether it comes from industrialists or individuals, there are products in the recycling sectors whose material constituting them could be used as raw material for various manufacturing processes. However, other substances can be deposited on these products and constitute stains whose presence prevents the use of the products as raw material, because these stains would harm the quality of the manufacturing process using this raw material or of the product manufactured by this process. These products, which constitute a contaminated material, can be packaging, having residues of substances which they have contained, for example hydrocarbons, paints, oils, products of the chemical or food industry.

 Processes for the incineration of this contaminated material are currently known. The emission of combustion gases into the atmosphere from incineration plants poses environmental problems, and it is necessary to provide incinerators with complex and expensive smoke treatment plants. In this way the recovery as a material of most of the fuel elements is also lost. In addition, the treatment of metal packaging requires significant energy input and the metal parts from solid incineration residues are more difficult to recover because they incorporate clinker.

 The treatment of waste by thermolysis is also known. The contaminated material is brought to a medium temperature which allows certain components to be transformed into combustible gas. We also meet here the same requirements for smoke treatment, and high energy consumption. Likewise, the combustible material in packaging is not directly recovered.

 There is also known a cleaning technique by washing with water, possibly with additives such as detergents. Depending on the products that contaminate the material, the effectiveness of this technique is not in accordance with the cleanliness requirements defined by the users of the raw material. In addition, the process generates water polluted by the products contained by the contaminated matter and which require treatment before being discharged.

 The object of the invention is to respond to the problems indicated above.

 With these objectives in view, the invention relates to a process for cleaning material soiled by residues, characterized in that the material to be cleaned is brought by stirring in contact with a solid cleaning product and struck by blunt objects. The solid cleaning product detaches and collects liquid or pasty residues such as chemicals, hydrocarbons or paints.

Blunt objects are dense weights that do not have a sharp corner. When brewing, they strike or roll on the surfaces of the material to be cleaned. These shocks or crushing have the effect of breaking and pulverizing the solid residues which adhere to the material to be cleaned. Thus residues are no longer adherent to the material to be cleaned.

 The method according to the invention has the advantage of not requiring combustion or thermolysis.

Therefore there is no smoke to treat and no need for heavy and expensive installation to perform this treatment. This process also does not use washing water which would contain pollutants after passing over the material to be cleaned. This avoids the use of a water treatment installation to isolate the pollutants.

 Thanks to the invention, a sufficiently clean material is obtained with regard to the requirements for use in a material recovery cycle.

 Advantageously, the cleaning product is a fibrous product. Sawdust is advantageously used as a solid cleaning product, but other products, such as ground hemp, can be used. In addition to its absorption capacity, it has the advantage of not compacting, of not agglomerating during mixing, and also of having an abrasive effect. The passage of sawdust over the surfaces to be cleaned makes it possible to obtain an abrasive effect in order to leave adherent solid particles from the surfaces to be cleaned. To obtain an additional abrasive effect, it is advantageous to use sand as a solid cleaning product. Preferably, the sand is a siliceous sand which has a high hardness and therefore a reinforced abrasive effect. In another advantageous manner, the cleaning product can be a mixture of sawdust and sand to combine the effects of abrasion and absorption.

 The invention also relates to a particular mode of implementation of the process defined above, characterized in that the mixing of the material to be cleaned is carried out in a rotary drum with horizontal axis, and in that the loading with the inside this drum is carried out at one end of the drum by means of feeding and transport into which the material to be cleaned and the solid cleaning product are poured separately, and in that the mixture is discharged by the other end of the drum.

 The axis of this drum is horizontal. The rotation movement of the drum drives the material, the cleaning product and the weights along the wall where they are held by centrifugal force, until the imbalance causes them to fall back towards the bottom point of the drum. The product to be cleaned and the material fall back and slide over each other. The product to be cleaned thus passes over the surfaces of the material and absorbs the liquid or pasty residues therein. Due to their massive constitution, the weights fall heavily towards the wall of the drum, they crush the material which is interposed between the wall of the drum and the weights or between the weights themselves and roll over them. A mechanical effect is thus obtained which crushes solid and friable residues. In addition, if the cleaning product is interposed between one of the weights and the material to be cleaned, the latter is compressed against the material to be cleaned and slides on it with pressure. The abrasive effect is thus increased. It can thus be seen that the material to be cleaned introduced into the drum is then rid of the residues which adhered thereto. The same effect is obtained when the material to be cleaned and the cleaning product are caught between the weights.

 According to a particular arrangement of the invention, the blunt objects are bars which extend substantially over the length of the rotary drum. In this way, the bars cannot be concentrated in any privileged area of the drum, and the shocks generated by the movement of these bars are distributed over the entire length of the drum.

 According to another preferred arrangement, the blunt objects are balls of sufficient size to remain inside the drum.

 Preferably, the material to be cleaned is shredded beforehand into pieces of grain size less than 200 mm, for example from 100 to 200 mm, in at least one operation. This operation can be carried out for example by mills with rotary knives. The material thus shredded is poured onto a conveyor belt which feeds an Archimedes screw which itself feeds the rotary drum.

 The mixture treated in the rotary drum is conveyed at the outlet of the drum to a screen. The mixture is separated into a fine part which consists essentially of the cleaning product, and a coarse part which constitutes the recovered material. The sorting is completed by the separation of the metallic elements from the coarse part by a technique known per se, such as a magnetic separation. Optionally, the metallic elements of the fine part are also separated by the same technique, for the purpose of purification.

This fine part is then either reused as a product to be cleaned, or put in reserve to be used for example as solid fuel, for example in cement factories.

 Other characteristics and advantages will appear in the description which will be given by way of example of a process and device for treating contaminated material in accordance with the invention.

Reference is made to the appended drawings in which:
FIG. 1 is a plan view of an installation with the various material processing stations
FIG. 2 is a cross-sectional view of a drum
FIG. 3 is a perspective view of a rotary drum
By way of example, FIG. 1 shows an installation of an installation implementing the method which is the subject of the invention. In the material processing order, there is a grinder (2), a rotary drum (1), a screen (3), a storage hopper (4) of the cleaning product (22). Belt conveyors known per se connect the devices together. Other belt conveyors complete the installation, in particular a belt conveyor (9) connects the hopper to the belt conveyor (6) which feeds the rotary drum (1), and another conveyor (30) from the outlet of the screen to a sorting bench (5).

 The drawing of Figure 2 shows the rotary drum (1) into which have been poured the material to be cleaned (21) as well as the cleaning product (22), in the middle of which are the bars (20). In an exemplary embodiment, the drum (1) has a diameter of 1.90 m and a length of 3.90 m. The bars (20) are made of steel, and have a length of 3.50 m, with a diameter between 50 and 70 mm, ie a mass of 50 to 110 kg.

The number of bars (20) inside the drum (1) is typically from 50 to 70, but may be lower depending on the product to be treated. Only a few bars have been shown on the drawing for better readability thereof. The rotation speed of the drum (1) is approximately 20 revolutions per minute.

 In Figure 3, the representation of the rotary drum (1) shows at one end thereof an opening (17) formed in the center of the face (11) which closes the drum (1) and a screw d 'Archimedes (14) introduced into the drum (1) through this opening (17).

At the other end of the drum (1), oblong holes (13) are provided on the cylindrical part of the drum (1). These holes (13) extend tangentially to the cylinder and have a dimension of 100 x 200 mm. The drum (1) is guided in rotation by at least four rollers (15) distributed in two pairs, the axis of rotation of which is substantially horizontal and parallel to the axis of the drum (1), the axes of the rollers (15 ) of each pair being substantially combined and located on either side of a vertical plane passing through the axis of the drum (1). At least one of these rollers (15) is rotated by a motor (16). The mechanical power absorbed by an exemplary embodiment of this type is of the order of 60 to 100 kW for a treatment capacity of 4 to 6 tonnes per hour. This power is very modest in comparison with the powers necessary for the treatment of the material by a process by incineration or by thermolysis.

 The implementation of the method of the invention is obtained by these means. By the rotational movement of the drum (1) around its axis, clockwise in Figure 2, the contents of the drum (1) is driven and rises along the wall on the left side of the drum. The centrifugal force keeps all the content applied on the wall up to a point beyond which the content is unbalanced and falls back towards the bottom point of the drum. As the bars (20) are massive elements, they fall heavily against the wall (10) of the drum (1) or they collide with each other. The mechanical crushing effect is obtained on the material to be cleaned (21) and the cleaning product (22) which are interposed between the bars (20) or between a bar (20) and the wall (10) of the drum. (1).

 It can be seen in FIG. 3 that the mixture of the material to be cleaned (21) and the cleaning product (22) is poured out at one of the ends of the drum. Although it is a solid material, the movement imposed inside the drum creates a kind of fluidization of the mixture, and as a result, it is gradually distributed over the entire length of the drum (1). As a result, the mixture reaches the other end (12) of the drum where the discharge holes (13) made on the drum are located. The mixture passes through these and falls on a belt conveyor (7) which discharges it towards the screen (3).

 In a preferred installation, the material cycle includes the following operations. The material is first fed into a rotary knife mill (2). This mill, known moreover, has two parallel axes located in a substantially horizontal plane and on which discs are mounted. Each disc on a tree corresponds to a disc on the other tree, the two discs being in partial overlap. The covering of these discs thus constitutes a shear.

The material to be cleaned is introduced above the shafts in reverse rotation, so that the material is entrained between the shafts and is cut by the shears formed by the discs.

 The material (21) thus shredded has a particle size less than 200 mm. It is placed on a belt conveyor (6) which feeds the rotary drum (1). This belt conveyor (6) also receives the cleaning product (22) which is stored in a hopper (4), known per se, via another belt conveyor (9). The mixture thus formed on the conveyor belt (6) is poured into the Archimedes screw (14) which feeds the rotary drum (1), which transfers, by its rotation, the mixture inside the drum (1) .

 After the treatment already described above, the mixture is transferred to the screen (3), which separates the mixture into a fine part and a coarse part.

In a preferred embodiment, the screen mesh size is approximately 15 to 25 mm.

 The fine part, consisting essentially of the cleaning product (22), is freed of the metallic elements, then evacuated according to its state, either towards the hopper (4) for a new cycle if this fine part is not saturated with residues, or , if not, to storage to constitute a solid substitute fuel.

 The coarse part is then evacuated to a sorting bench (5) known per se and constitutes the recovered material which will be used as raw material.

Claims (12)

 1. Method for cleaning material to be cleaned (21) soiled by residues, characterized in that the material to be cleaned (21) is brought by stirring into contact with a solid cleaning product (22) and struck by blunt objects ( 20).  2. Method according to claim 1, characterized in that the solid cleaning product (22) is absorbent.  3. Method according to claim 2, characterized in that the absorbent solid cleaning product (22) is sawdust.  4. Method according to claim 1, characterized in that the solid cleaning product (22) is an abrasive such as sand.  5. Method according to claim 1, characterized in that the mixing of a mixture of the material to be cleaned (21) and the cleaning product (22) is carried out in a rotary drum (1), in that the loading at the interior of this drum (1) is carried out at one end of the drum by supply (14) and transport (6) means into which the material to be cleaned (21) and the solid cleaning product are separately discharged (22), and in that the mixture is discharged through the other end (12) of the drum (1).  6. Method according to claim 5, characterized in that the blunt objects are bars (20) which extend substantially over the length of the drum (1).  7. Method according to claim 1, characterized in that the blunt objects are balls.  8. Method according to claim 3, characterized in that the mixture of material to be cleaned (21) and sawdust (22) is screened in material valued for the part of large particle size on the one hand, and in solid fuel for the fine part on the other hand.  9. Recovered material, characterized in that it is obtained by the process of claim 8.  10. Solid fuel, characterized in that it is obtained by the process of claim 8.  11. Installation for processing contaminated material according to the method of claim 1, characterized in that it comprises a crusher (2), a rotary drum (1), a screen (3), a storage hopper (4), a sorting bench (5), means of transport (6) of material from the crusher (2) to the rotary drum (1), from the rotary drum (1) to the screen (3), from the screen (3) to the storage hopper (4), from the storage hopper (4) to the rotary drum (1) and from the screen to the sorting bench (5).  12. Installation according to claim 9, characterized in that the loading inside this drum (1) is carried out at one of the ends of the drum by supply means (14) and transport (6) in which are separately poured the material to be cleaned (21) and the solid cleaning product (22), in that the mixture is discharged through the other end (12) of the drum (1), and in that the drum contains blunt objects (20).