ITBG20120024A1 - PLANT FOR THE TREATMENT OF WATERS DERIVING FROM THE BETONIERE WASHING - Google Patents

Description

The present invention relates to a plant for treating water deriving from washing concrete mixers.

More specifically, it refers to a plant for the total recovery of waste deriving from the process of washing concrete residues from and concrete mixers, with the introduction of recycled waste into the production cycle.

It is particularly aimed at sites with medium-high production, equipped with about 10 truck mixers. In these sites, normally each concrete mixer on return has a concentration of concrete residues that varies from 0.5 to 0.2 cubic meters per mixer. Over the course of the day, considering 10 truck mixers, approximately 4000 kg of residues with grain size up to a few millimeters are produced, with the use of approximately 2,000 liters of water for washing each cement mixer.

Basically, each truck mixer discharges the washing liquid into a receiving tank which is associated with an inclined and rotating auger in the tank that directly separates about 50% of the heavy materials contained in the poured liquid. Only about 2000kg of the 4000kg of solid material unloaded from the concrete mixers are then recovered.

The remaining liquid part, which has a high quantity of particles with different granulometry in suspension, is conveyed into special tanks prepared with agitators and pumps. These pumps take the water mixed with particles and re-introduce it into the production cycle (to load a new concrete mixer for example).

This last part of loading is carried out without effective control of the percentages of solid present in the water returned to the cycle.

Furthermore, the solids present in the water are different throughout the day.

Moreover, with the current waste processing systems it is necessary to carry out about 2 washes / day of the pumps; each wash takes about 2000 liters, for a total of 4000L. Each of these washing cycles 'moves' about 0.5 MC of concrete (therefore about 4000kg of concrete considering the presence of 2 pumps). In essence, about 24,000 liters of water are used in a day and 8000 kg of residues are produced, of which only about 4000 kg are actually separated.

It is therefore evident that the current cycles are poorly performing, use large quantities of disposable water and recover only a small part of the solid material present in the concrete mixers.

Furthermore, it should be noted that the water recycled with the current systems is re-introduced into the concrete mixers at the new load.

Therefore, when the water is withdrawn from the storage and recycling tanks, the values read by the meters do not faithfully reflect the real quantity of water introduced into the concrete mixer since the percentage of solids present in the flow is unknown or in any case highly variable also depending on the various times of the day and the load specifications of the concrete mixers.

The purpose of the present invention is to provide a plant for treating the liquids deriving from the washing of concrete mixers which is improved and better performing than those of the known art.

In particular, an object of the present invention is to provide a plant which is capable of accumulating large percentages of treated water free from suspended particles, which can therefore be used and dosed with precision.

A further object of the present invention is that of separating a greater quantity of solids than in the known art, so as to be able to control the dosage and re-introduction into the cycle in a precise manner.

These and other purposes are achieved by realizing a plant for the treatment of water deriving from the washing of concrete mixers, made according to the technical teachings of the attached claims.

Further characteristics and advantages of the invention will become evident from the description of a preferred but not exclusive embodiment of the plant, illustrated by way of example and therefore not limitative in the attached drawings, in which:

Figure 1 is a simplified schematic view of the plant according to the present invention, applied to already existing treatment areas;

Figure 2 is a schematic view of the plant of the present invention in an embodiment different from that of Figure 1; And

figure 3 is a variant of the system of figure 2.

With reference to the aforementioned figures, a plant for the treatment of water deriving from the washing of concrete mixers 2 is shown, indicated as a whole with the reference number 1.

It comprises a separator 3, suitably arranged on a masonry support structure 4. The separator 3 is equipped with a first tank 5 for receiving the washing liquid from the mixer 2. Basically, the mixer 2 returning from the construction site is loaded with washing liquid (it will be explained later how) and after waiting for a time required for washing, this liquid is slowly emptied into the receiving tank 5.

As can be seen from the drawing, the tank 5 is shaped like a hopper and at the base has a means of mechanical separation of the coarser (and therefore heavy) residues present in the washing liquid.

The mechanical separation means in this case comprises an auger 7 mounted inside a casing 6 arranged with a diagonal axis diagonally.

The rotation of the auger is operated by means of a suitable motor 8. The coarse material that immediately falls on the bottom of the tank 5 is lifted by the auger 7 and discharged in correspondence with an accumulation area of recovered solid material 9.

The tank 5 has an opening (weir) from which the water without very heavy particles but in which a large quantity of particles with a diameter of less than 0.6 mm are suspended, is conveyed by gravity, through a line 10, to a transition tank 11, coupled to a suitable loading pump 12.

The transition tank is an intermediate passage and has the sole purpose of not allowing pump 12 to draw directly from tank 5. In fact, the vortices created by the suction of the pump would convey a large quantity of suspended particles into the flow of water at its delivery. , even of large dimensions, which could instead be separated from the separator.

If present, instead of the intermediate tank, also a wastewater recovery tank from the yard, like the one shown in the figure, and indicated with reference 13, can be used with the same function.

The intermediate tank, in the configuration illustrated in figure 1, has a sixth valve V6 which controls the overflow and directly discharges any excess liquid into the waste water recovery tank 13.

It is used in case there is an overflow situation on a settling tank 14, which we will discuss later.

The loading pump 12 has a delivery connected to a feeding line 15 of the decantation tank 15.

In essence, the line 10, the supply line 15, the intermediate tank 12 and the loading pump 12 are means suitable for placing the first tank in a fluid passage connection with the inlet of the settling tank 14.

The settling tank 14 has a first accumulation area of treated liquid 14A substantially free of suspended particles. It preferably has a cylindrical shape with a constant circular, square or rectangular section.

Advantageously, it is made of structural steel with galvanized walls for corrosion protection.

Below the first zone there is a second zone 14C for the accumulation of sludge formed by sedimented particles.

This area is made for example of stainless steel, and is suitably shaped (as shown in the figure) to allow the conveyance of the sludge accumulated by decantation towards a drain 16.

The adjustable tank seals are specially designed to maintain airtightness and the supports for the external shafts are not in contact with the sludge.

The first and second zones are interconnected by an intermediate zone 14B shaped like a hopper.

In the intermediate zone and in the second zone, first and second stirring means are respectively provided.

The first agitator means 18 substantially comprises an impeller 1BA mounted on a vertical shaft 18B and rotated by a suitable motor-reducer 18C. The first agitator 18 is fixed to a walkway 19, which is accessed via a marine-like staircase (not shown).

The second agitator 20, arranged in the second zone 14C, is formed by a pair of horizontal mixing shafts 21 to which suitably sized blades 21 are applied, and inclined in the opposite direction to the motors 23 for driving the shafts.

Advantageously, the shafts are easily accessible through access doors for their extraction and through lateral inspection doors.

Basically, suitably timed and rotated when necessary, the stirring means prevent the particles / sludge present in the second zone and in the intermediate zone from settling and agglomerating together.

Obviously, the vertical agitator is sized to move the water heavily loaded with particles, and the system with opposing propellers from the horizontal mixer does not allow the sludge to agglomerate on the bottom.

To complete the description of the decantation tank, it is noted that the first zone provides an outlet 22 for treated liquid (ie substantially devoid of solid particles), suitably intercepted by first valve means VI.

The outlet 22 is interconnected with an accumulation tank 23 of purified liquid. In the example of figure 1 this accumulation tank is underground, but we will see later that it can assume different configurations and positions and can, for example, be configured as a tank.

The second zone also provides a discharge 16 for the sludge, and this discharge is intercepted by second valve means V2.

As can be seen from the drawing, the sludge discharge 16 is connected to the suction of a first pump PI whose delivery is connected to a loading line 30. The loading line 30 has a branch 32 intercepted by a suitable valve means V9 , which directs the fluid present in it to the dosage of a concrete production plant D. The loading line 30 continues downstream of the branch 32 towards the concrete mixer, through a valve V7.

There is also a second pump P2 with a suction that draws into the accumulation tank 23 and also connected to the loading line 30.

As can be seen from the drawing on the load line 30 there is a mass flow meter M, for example of the Coriolis effect type.

Continuing in the description of the plant, it is easy to note that upstream of the mass flow meter M there are provided means 24 for adjusting the flow rate of said sludge and of said treated liquid drawn from said accumulation tank.

In particular, these means for regulating the flow rate comprise a mixing joint 25 which provides a first and a second inlet coupled respectively to the second valve means V2 present on the sludge discharge 16 and to third valve means V3 present on a delivery line from the second pump P2 which draws from the accumulation tank 23.

A first and a second outlet of said mixing means are coupled respectively:

- to the load line 30 (via a fourth valve means V4), e

- to the first pump PI (via a fifth valve means V5).

The proper adjustment of the V2-V5 valves and calibrated of the pumps allows to have at the loading line 30:

- only sludge (mainly intended for dosing the concrete production plant)

- purified water only (intended for loading the concrete mixer or for dosing the concrete production plant)

- a desired mix of sludge and purified water (mainly intended for dosing the concrete production plant).

With respect to the known technique, this provides the undoubted advantage of completely eliminating solid residues, reusing them in known percentages for the new production cycles, and of having high percentages of clarified water to be reused also in the tank trucks / truck mixers.

The plant according to the present invention is advantageously equipped with a recycling line 31, intercepted by a suitable solenoid valve V8, able to divert said loading line 30 inside said receiving tank 5. Obviously for the operation of the line 31 it is necessary to provide an additional solenoid valve V7 downstream (concrete mixer side) of the branch between the loading line 30 and the recycling line 31.

At the end of the description of the plant, it is noted that the tank 13 for the recovery of the waste water from the yard, has a third pump P3 in it, with a delivery connected to the said loading line 30 of the concrete mixer.

The main purpose of this pump P3 is to recycle the liquid present in the tank 13 inside the discharge tank 5 (valves V4, V5 and V7 V9 closed, valve V8 open), to allow the treatment of waste water and discharge from part of the plant. This liquid, before being sent to tank 5, can be conveyed through an oil separator.

The operation of the plant is essentially the following.

A concrete mixer discharges the contents of washing liquid into tank 5, and the liquid is pre-treated by the separator which eliminates the largest and heaviest particles, accumulating them at the exit of the auger.

The weir liquid from the tank 5, however loaded with suspended particles, overflows into the tank 11 from which it is pumped into the settling tank 14. If the settling tank is too full it is conveyed to the waste water tank 13 awaiting treatment.

Once the settling tank 14 is reached, the liquid is left immobile and physical separation occurs by decanting the solid materials (particles). This operation takes at least 2 hours.

The first area of the settling tank 14 is then automatically emptied by opening the valve VI.

The tank 14 provides, in correspondence with the level at which the outlet 22 is located, a level sensor which automatically closes the valve VI when the level drops too low.

At this point, only liquid full of residues and particles (about 8MC) remains in the tank.

Through the management of a PLC installed in a panel on board the machine, the process of maintaining the sludge in suspension is started, to avoid its agglomeration.

The system of solenoid valves described, controlled by the PLC and interfaced with the mass meter M, by acting on the valves V2 and V3 (V4 is closed and V5 Open) allows the control of the quantity of sludge to be sent to the loading line 30, in depending on the percentage to be obtained.

The transport of the mixed material takes place through the vortex-type pump P1.

Through the regulation with PLC and the control with the flow meter M it is possible to obtain a very low margin of error on the set mixture (about 0.1% error).

The need to clean the pipes to prevent them from encrusting or depositing residues is managed by the PLC, which, acting on the V2-V5 valves and on the PI and P2 pumps, automatically provides for washing. For example, the washing of the pipes and pumps is carried out by reusing the liquid in the tank 23. In the past it was instead necessary to purge the storage tanks and dispose of the waste.

Obviously when necessary, the loading procedure of the concrete mixer is started through the loading line 30.

Basically, the plant described above provides countless advantages including:

- no cost for the disposal, even in solid form, of the by-product;

considerable reduction of maintenance costs for components used for disposal in process waters see pumps, impellers, valves, agitators and pipes;

- reduction of costs in the supply of water from the distribution network;

cost reduction in the supply of fine aggregates;

- maintenance of the structures currently present on site;

downgrading of the current waste to a by-product originating from a production process;

identification and preventive definition before the introduction, in the new production process, of the percentages of liquid and solid belonging without being subjected to further treatments; water supply greater than the current one with potential accumulation also of the first rain water;

better conditions of the working environment through the concentration in airtight containers / tanks of waste and turbid waters;

dosages of waste in predetermined percentages without precluding the quality of the concrete desired at any time of the production day;

- disposal of the by-product reinserting it in the new production cycle;

- margin of error of 0.1% for me. on the percentage balance between solids and liquids;

deduction of solids from the mix design with an integration to the current dosing systems by adding water in the correct percentage in order to satisfy, in some cases by improving, the requirements of the product.

Advantageously, the system described allows compliance with the following standards:

- soil protection rules;

- rules for the protection of water from pollution and management of water resources;

- rules on waste management

- rules on the protection of compensation against environmental damage;

- compliance with the emission limits of water discharges from industrial processes;

- compliance with the prohibition of direct discharge of rainwater into groundwater;

Starting from the inventive concept of the plant described above, it is possible to develop various alternative embodiments, two of which are represented in figures 2 and 3- In them parts similar to those already described in the previous embodiment are indicated with the same numerical references , and therefore will no longer be described.

The systems in figures 2 and 3 can be envisaged in new installations, where there are no already underground tanks.

The only differences found with the previous solution are, as regards Figure 2, the presence of an accumulation tank 23 of purified liquid arranged above ground. A further pump 50 is then provided to introduce the fluid thereto. There is also no waste water recovery tank in the square.

As regards Figure 3, on the other hand, with respect to the plant of Figure 2, the agitators of the second zone with double auger are replaced by a second impeller 18D mounted coaxially to the first 18A and rotated by the same shaft 18B.

Obviously, in all raised systems according to the innovative concept of the present invention, it will be possible to provide or not pumps to transfer liquids from one tank to another, depending on the level at which these tanks are positioned.

Claims (13)

CLAIMS 1. Plant for the treatment of water deriving from the washing of concrete mixers comprising a separator equipped with a first tank for receiving the waste liquid from washing a concrete mixer, said receiving tank being coupled to first mechanical separation means of the coarse residues contained in the discharge liquid, and an accumulation tank for a treated liquid, characterized in that a weir of said first tank is placed in a fluid passage connection with an inlet of a settling tank, the settling tank having at least a first area of accumulation of treated liquid substantially free of suspended particles, a second zone of accumulation of sludge formed by sedimented particles and an intermediate zone shaped like a hopper able to interconnect the first and second zone, said intermediate zone and said second zone presenting respectively first and second agitator means able to prevent the particles present in said areas d agglomerate, said first zone providing an outlet of treated liquid, intercepted by first valve means, interconnected with said accumulation tank of purified liquid, said second zone providing a discharge of sludge, intercepted by second valve means. 2. Plant according to claim 1 in which the sludge discharge is connected to the suction of a first pump whose delivery is connected to a loading line, said loading line providing a supply branch of a production plant of concrete. 3. Plant according to one or more of the preceding claims in which there is a second pump with a suction which draws into the treated liquid accumulation tank and a delivery connected to the loading line. 4. Plant according to claim 2 and / or 3 in which on said loading line there is a mass flow meter, preferably of the coriolis effect type. 5. Plant according to the preceding claim in which upstream of the mass flow meter means are provided for adjusting the flow rate of said sedimented particles and of said treated liquid drawn from said accumulation tank. 6. Plant according to the preceding claim, wherein said means for regulating the flow rate comprise a mixing joint which provides a first and a second inlet coupled respectively to the second valve means present on the sludge discharge and to third valve means present on a delivery line from the pump that draws from the accumulation tank, and a first and a second outlet coupled respectively by a fourth valve means to the loading line of the concrete mixer, and by a fifth valve means to the first pump. 7. Plant according to one or more of the preceding claims in which there is a recycling line able to divert said loading line inside said receiving tank. 8. Plant according to one or more of the preceding claims in which the fluid passage connection between said weir and the settling tank comprises a transition tank coupled to a loading pump. 9. Plant according to one or more of the preceding claims in which there is provided a recovery tank for the waste water from the yard, and a suction pump in said recovery tank and with delivery connected to said loading line. 10. Plant according to the preceding claim in which a drain of the transition tank flows into said recovery tank to cope with any overloads of the settling tank. 11. Plant according to claim 1 wherein said first mechanical separation means comprise an auger one end of which is immersed in the tank. 12. Plant according to claim 1, wherein said first stirring means comprise a first vertical axis impeller driven by a suitable motor. 13. Plant according to one or more of the preceding claims in which said second agitator means provide a second impeller mounted coaxially to the first impeller, or in which said second agitator means provide a pair of substantially horizontal parallel axis augers with opposite blades.