System and procedure for adsorption by direct evaporation of leached effluents from an urban solid waste landfill (Machine-translation by Google Translate, not legally binding)

ES 2 551 802 A1

DESCRIPTION

System and procedure for adsorption by direct evaporation of leachate effluents from a solid urban waste landfill.

Scope and prior art

The present invention refers to a system for adsorption by direct evaporation of leachates and to a procedure carried out by means of said system and has application in the elimination of leachates accumulated in ponds or dumping tanks resulting from a solid organic waste (MSW) landfill. . However, the invention is not limited to this use and can be advantageously used in any basin or tank where the need to evaporate liquid arises, such as for example mining basins, and liquid effluents from industrial or agricultural processes.

In the MSW landfills, the problem is the elimination of the leachates generated and that are generally accumulated for their treatment and disposal in ponds or open-air tanks.

In a known technique, the leachates accumulated in the dumping basin are sprayed again on the landfill by means of an irrigation network to promote natural evaporation, but this technique has the disadvantage of a high rate of return of the leachates since part of the The garbage percolates again, returning to the dumping basin. Furthermore, this technique has limitations relative to the climatology of the landfill site and it only results in effective evaporation in the dry season.

From document ES 2265888 a method and apparatus for concentration of waste water by accelerated evaporation is known. According to this procedure and corresponding installation, an evaporation gas is circulated through a cellular panel sprayed with leachate, the panel of which is mounted in a closed enclosure, whereby a forced circulation of said evaporation gas is carried out in said enclosure, between intake means placed on the spray side of said leachate and gas outlet means, and it being envisaged that the intake means have means for supplying heat energy from the combustion of a biogas produced by the fermentation of waste, and also the temperature of said evaporation gas is regulated between 25 ° and 45 ° C.

For the execution of this procedure, a complex installation is provided with a panel system, means for spraying the leachate, as well as means for cooling the evaporation gases to working temperature, which is exhaustive in equipment and maintenance costs.

Accordingly, there is still a technical need to provide a system for the elimination of leachates by evaporation that is easy to implement and that can be used "in situ", that is, in the waste pond itself associated with a MSW landfill, and with the possibility of using biogas that is generated in the landfill itself.

Object of the invention

Starting from the previously described state of the art, the object of the invention is to develop a system of the type indicated in the beginning that is easy to implement and maintain, said system being capable of being applied in situ, that is, in a receiving pond. leachate from the landfill.

The invention starts from the idea that to achieve adsorption by evaporation of the leachate contained in the pouring basin, it is enough to carry out a circulation inside an evaporation chamber floating in a floating manner in the basin and filled with leachates.

ES 2 551 802 A1 of combustion gases from a burner, for example biogas submerged in the evaporation chamber, so that the combustion gases pass through the leachate to evaporate in the form of small bubbles that in addition to supplying the Latent heat of evaporation of water effectively imparts agitation of the liquid that promotes evaporation. Thanks to the large exchange surface between the dry combustion gases and the leachate, generated by the small bubbles, a high adsorption of the liquid by the combustion gas is guaranteed.

This objective is achieved through the characteristics indicated in claim 1. Other advantages and objectives are achieved through the characteristics indicated in the dependent claims of said claim 1.

A system is provided which according to the invention comprises:

- at least one evaporation chamber with a bottom portion and a gas outlet above the bottom portion, said evaporation chamber being adapted to be partially immersed in said pouring basin filled with the leachate to be evaporated;

- at least one fuel gas burner with a combustion chamber adapted to lie submerged within the evaporation chamber and a combustion gas outlet of said burner being arranged in the vicinity of the bottom portion of said evaporation chamber;

- at least one fuel gas blower and at least one combustion air blower that feed the at least one burner through a corresponding fuel gas network and a corresponding air network; Y

- A mesh of floats coupled to the, at least one, evaporation chamber in order to provide it with sufficient buoyancy so that, at least, the upper gas outlet portion is above the level of the sheet of leached into the dump basin.

According to an additional characteristic of the invention and in order to guarantee the maintenance of a constant filling level of the evaporation chamber, it is advantageous to provide at least one ballast tank coupled to the upper part of the, at least one , evaporation chamber, which has a filling conduit that is introduced into said evaporation chamber.

According to an additional characteristic of the invention and to guarantee a safe start of combustion, the fuel gas network has at least one pilot flame branch (60) connected to the at least one burner.

According to another additional characteristic of the invention and in order to create additional agitation of the leachate to evaporate, the combustion air network has at least one bubble branch coupled to a bubble ring arranged in the bottom portion of the, at the minus one, combustion chamber.

According to another additional characteristic of the invention, an additional advantage results when the fuel gas fed to the at least one fuel gas blower is thermally conditioned through a cooling device.

It is also advantageous in accordance with a further characteristic of the invention, to provide the evaporation chamber in the form of a reservoir with a generally cylindrical arrangement and inside which, near its bottom portion, at least one first support is provided for holding the, at least one burner, as well as a second ring-shaped support to support the bubbling ring and the upper outlet for the evaporation gases being configured as a chimney. In addition, to favor the process of

ES 2 551 802 A1 evaporation of the leachate a fan is provided operatively coupled to the upper outlet of the evaporation chamber.

According to another additional characteristic of the invention, the second ring-shaped support is arranged with a variable geometric configuration and inclination to regulate the entry of leachate and to allow the evacuation of condensates and to determine a suitable passage to favor the liquid rising through the ballast pipe of the ballast tank of each chamber. Here, alternatively, the regulation of the leachate inlet to the evaporation chamber can be carried out by means of a cover operatively associated with said second ring-shaped support.

In addition, according to yet another additional characteristic of the invention, to facilitate a secure mounting of the fuel gas and combustion air blowers, a grounded bed is provided in the vicinity of the pouring basin.

According to another additional characteristic of the invention and in order to provide adequate stability within the pouring basin, the at least one evaporation chamber is anchored to a third support that is fixed or supported by legs or cables at the bottom. of happiness the dumping basin.

In accordance with yet another additional characteristic of the invention to provide a reliable system, a redundant and scalable configuration consisting of a plurality of chambers with their respective burners is advantageous, a configuration consisting of at least three combustion chambers being especially preferred. , with respective burners inside each chamber; two blowers to feed fuel gas, through a gas network, to the respective burners and to the respective pilot flame branch of said burners; and two blowers to feed combustion air, through an air network, to the respective burners and to the respective bubbling branches.

Another additional objective of the invention consists of a process for adsorption by direct evaporation of leachate effluents from a solid urban waste landfill to be carried out in a leachate dumping basin, associated with the waste landfill with a system according to claims 1 to 12.

This objective is achieved through the characteristics indicated in claim 13. Other characteristics and advantages of the method are achieved by the characteristics of the dependent claims of said method claim 13.

According to the invention, said process comprises steps of:

- Provide within the leachate discharge basin at least one evaporation chamber with a bottom portion and a gas outlet above the bottom portion, inside which at least one burner is arranged having a combustion chamber and a combustion gas outlet located next to said bottom portion, said evaporation chamber being provided with adequate buoyancy to remain partially immersed in the leachate contained in the pouring basin so that, at least, its gas outlet is located above the level of the leachate sheet, keeping the level of the leachate essentially constant. fill level of the leachate inside the evaporation chamber;

- feeding the at least one burner with fuel gas and combustion air by means of the fuel gas and combustion air blowers through the respective fuel gas and combustion air networks;

- start the combustion of the fuel gas mixture in the, at least one, burner, to provide combustion gases by means of their combustion gas output to form

ES 2 551 802 A1 flue gas bubbles circulating through the leachate to evaporate contained in the evaporation chamber from its bottom portion;

- maintain the combustion of the gas-air mixture by means of the at least one burner, to heat the leachate to evaporate to its evaporation temperature, with extraction of the combustion gases that carry the evaporated leachate through the gas outlet of the evaporation chamber.

According to a further characteristic of the method according to the invention, an advantage results that allows the desired combustion conditions to be achieved when the stage of supplying the at least one burner with the mixture of fuel gas and combustion air comprises a stage of regulation of the mixture. Furthermore, a thermodynamically efficient evaporation process results when said combustion gas-air mixture is regulated to obtain stoichiometric combustion mass-energy equilibrium conditions.

In addition, according to another additional characteristic of the invention, the combustion is carried out with excess air, allowing lower working temperatures in the range of 70 ° -90 ° C. Here the lower evaporation due to lower working temperatures is compensated by the higher volume of air contributed to combustion.

In order to favor the evaporative process, it is advantageous in accordance with another additional characteristic of the invention to generate additional agitation within the evaporation chamber, by means of a stage of supplying air from its bottom portion (20).

Also according to another additional characteristic of the invention, an effective evaporative process results when the heating of the leachate contained in the, at least one, evaporation chamber is carried out gradually, generating evaporation itself from a temperature of 50 ° C. with an optimum evaporation for a temperature of 80 ° C until reaching a thermodynamic equilibrium at most at a temperature of 93 ° C for stoichiometric combustion conditions.

In addition, according to another additional characteristic of the method according to the invention, it is advantageous in the combustion initiation stage, to close the leachate intake, sealing the intake orifice of the second ring-shaped support by means of the cover and then in the evaporation stage regulate the leachate inlet by means of the greater or lesser opening, for example by sealing the intake orifice with the help of its cover.

According to yet another additional characteristic of the invention, it is a particularly advantageous process from the point of view of costs and use of resources that is respectful with the environment, when biogas is used for combustion.

As mentioned above, the use of the system and process according to the invention is not limited to the evaporation of leachates and it should be understood that said system and process are applicable to the evaporation of various aqueous suspensions.

Brief description of the drawings

Other characteristics and advantages of the invention will appear more clearly from the description that follows made with the aid of the attached drawings, referring to a non-limiting exemplary embodiment and in which:

Figure 1 shows a partially sectioned view of a system for adsorption by evaporation of leachates according to the invention, installed in a leachate dumping basin of a municipal solid waste landfill.

ES 2 551 802 A1

Figure 2 illustrates a plan view of the installation according to figure 1.

Figure 3 shows a detail of the fuel gas and combustion air circuits of the installation of Figure 2.

Figure 4 schematically illustrates a plan view of the installation showing the mesh of floats.

Figures 5A to 5D show respective views in elevation, plan and cross sections according to lines II and II-II, of a preferred configuration of the evaporation chamber of the system of Figures 1 and 2.

Figure 6 shows a graph of the TS curves of the water / water vapor, to explain the evaporation process of the system according to the invention.

Detailed description of a preferred embodiment

As shown in the figures, the system according to the invention, indicated in general by reference (1), is installed inside an effluent leachate dumping basin (BVL) associated with a municipal solid waste landfill not shown, with the purpose of carrying out an evaporative adsorption of the leachates contained in said spill basin.

As can be seen in Figures 1 and 2, the system (1) consists of three evaporation chambers, although it should be clarified that according to the invention a greater or lesser number of them or even just one may be arranged inside each one of which are mounted gas fuel burners (3), two or more, which are fed with the fuel gas / combustion air mixture by means of respective fuel gas (4) and combustion air (5) blowers through respective fuel gas (6) and combustion air (7) networks.

As represented in greater detail in figure 1, each evaporation chamber has a bottom portion (20) and a gas outlet (21) and is installed floating inside the leachate discharge basin (BVL) so that when said dumping basin is full, at least its gas outlet (21) is located above the level of the leachate sheet (CLL), this with the help of a network of floats (8) as will be described further below in greater detail.

In Figures 1 and 2, it is observed that each of the burners (3) installed inside each evaporation chamber (2), has a combustion chamber (30) adapted to lie submerged in the leachate and an outlet of combustion gases (31) arranged in the vicinity of the bottom portion (20) of said evaporation chamber (2).

Still referring to Figures 1 and 2, fuel gas blowers (4, 4) and combustion air blowers (5, 5) mounted on a support bench 10 serve to feed the respective burner (3) with the mixture. of fuel gas and combustion air supplied through a respective fuel gas network (6) and a respective air network (7).

With reference to Figure 1 and additionally to Figure 4, it can be seen that a mesh of floats (8) coupled to the evaporation chambers (2) provide sufficient buoyancy so that, at least, the upper portion of the respective outlet of gases (21) are above the level of the leachate sheet (CLL) contained in the discharge basin. Additionally, and as shown in figure 1, at least one third support (11) anchored to the at least one evaporation chamber (2) is provided that by means of legs or cables (110) is fixed or supported on the bottom of the leachate basin (BVL) to maintain neutral buoyancy.

ES 2 551 802 A1

As can be seen especially clearly from Figures 2 and 3, the respective fuel gas network (6) has a respective pilot flame branch (60) connected to each respective burner (3); while the combustion air network (7) has a respective bubbling branch (70) which, as shown more clearly in figure 1, is coupled to a bubbling ring (700) arranged in the bottom portion (20) of the combustion chamber (2) in order to create additional turbulence in said chamber that favors the evaporative process.

In Figures 2 and 3, it is observed that the fuel gas blowers (4, 4) can be fed with fuel gas directly or alternatively through a cooling device (9) to reduce the temperature of the fuel gas and condense the excess. of water in said fuel gas.

It should be mentioned that the pneumatic circuit shown in figure 3 incorporates a plurality of fuel gas (VG) and air (VA) valves to establish the appropriate connections during the operation of the system and that they are not explained in greater detail as they result from handling. obvious to technicians.

As can be seen in greater detail in Figures 5A to 5D, the evaporation chamber (2) is provided in the form of a generally cylindrical tank and is internally equipped with first supports (22) located near its bottom portion (2 ) intended to hold the respective burner (3); additionally, it can be seen that a second ring-shaped support (23) to support the bubble ring (700) is provided in its bottom portion (20). Furthermore, the upper outlet (21) for the evaporation gases is configured as a chimney and has associated, as shown in figure 2, a fan (210) to favor the extraction of the combustion gases and the evaporated leachate.

As shown in Figures 1 and 5C, the second ring-shaped support (23) configures in the bottom portion (20) an intake opening (230) for entry of the leachate contained in the discharge basin (BVL) to through windows or holes (24) provided in the lower part of the evaporation chamber (2). This inlet orifice (230) is designed to be closed to a greater or lesser extent and thus regulate the leachate admission into the evaporation chamber either through a variable geometry and inclination or by means of a cover (231) with a linkage of actuation (232) accessible from the upper part of the evaporation chamber, or even closing said intake port; in particular, for example to close at the start of combustion and to open more or less after the evaporation of the leachate has started as will be explained in detail later.

Still making special reference to Figures 1 and 5C, it is observed that in the upper part of the evaporation chamber there is a ballast tank (25) which is connected to the interior of the evaporation chamber (2) through a duct (250), so that the filling level of said intake chamber can be kept constant. Additionally, the upper part of the lateral surface of the evaporation chamber (2), may be made openings (not shown) through which the leachate to be treated can flow freely and which also allow to contribute to the maintenance of a constant filling level. .

With the help of a system as described above, it is possible to execute a procedure for adsorption by direct evaporation of leachate effluents from a municipal solid waste landfill according to the following steps:

- Inside the leachate dumping basin (BVL), at least one evaporation chamber (2) is provided with a bottom portion (20) and a gas outlet (21) above the bottom portion in which Inside there is at least one burner (3) having a

ES 2 551 802 A1 combustion chamber (30) and a combustion gas outlet (31) located next to said bottom portion (20), said evaporation chamber (2) being provided with adequate buoyancy to remain partially immersed in the leachate contained in the dumping basin so that, at least, its gas outlet (21) is located above the level of the leachate sheet (CLV), keeping the leachate level in the evaporation chamber essentially constant ;

- The, at least one, burner (3) is fed with fuel gas and combustion air by means of the blowers (4, 5) of fuel gas and combustion air through the respective networks (6, 7) of fuel gas and air oxidizer;

- A combustion of the fuel gas mixture is started in the at least one burner (3), producing combustion gases that bubble through the leachate to evaporate contained in the evaporation chamber from its bottom portion (20) by means of the combustion gas outlet (31) from the burner (3);

- The combustion of the gas-air mixture is maintained by means of the burners (3), to heat the leachate to evaporate to its evaporation temperature, extracting the combustion gases carrying the evaporated leachate through the gas outlet (21 ) from the evaporation chamber.

Additionally, the stage of feeding the burners (3) with the mixture of fuel gas and combustion air comprises a stage of regulation of the mixture to achieve desired combustion conditions, being able to be adjusted, for example, to obtain stoichiometric combustion conditions or with excess oxidizer to regulate the temperature of the evaporation process.

It should be mentioned that in the combustion initiation stage, it may be advisable to close the leachate intake, closing the intake hole (230) of the second ring-shaped support by means of the cover (231) and later in the stage of evaporation regulate the leachate inlet through the greater or lesser opening, for example by sealing the intake orifice (230) with the help of its cover (231).

From the start of combustion, a step of supplying air into the evaporation chamber from its bottom portion (20) may be additionally provided, which produces additional turbulence in the leachate contained in said chamber, which as mentioned above contributes to the evaporative process and to the regulation of the thermodynamic equilibrium temperature that favors the evaporation of different fluids.

In this procedure, the heating of the leachate is carried out gradually, generating evaporation itself from a temperature of 50 ° C with an optimum evaporation for a temperature of 80 ° C until reaching a thermodynamic equilibrium at most at a temperature 93 ° C for stoichiometric combustion conditions. However, combustion can be carried out with excess combustion air, to operate at maximum temperatures in a lower range of 70 ° -90 ° C, so that the higher combustion air flow compensates the lower evaporation due to lower temperatures. of work, as they could be required by the composition of the diverse aqueous mixtures to evaporate.

Other details and technical considerations on the system and procedure for adsorption of leachates according to the invention will be described below, which may be defined by those skilled in the art through the corresponding tests and measurements.

Thus, for example, the biogas or fuel is delivered to the supply network (6) under the following conditions: 55% methane; 45% CO₂; relative humidity: 100% maximum of 89 grams of water per m³; 40 ° C temperature; mean hourly volume 500 Nm³ ± 10%

ES 2 551 802 A1

PCI 5,500 kcal / m³. It should be mentioned that a lower concentration operation is possible but this leads to a loss of performance.

However, it should still be mentioned that the system is capable of operating with any liquid or gaseous fuel, although biogas presents, for cost reasons, an advantage for certain applications.

As indicated above, optionally it is possible to supply the dehydrated fuel gas by means of a "chiller" and by means of the cooler (9) of the system according to the invention, reduce its temperature to approximately 10 ° C, condensing the excess water.

To achieve the operating conditions in the burner, the fuel pressure is raised to approximately 200 mbar, for its subsequent conditioning and dosage in the burner gas train. In the same way, the combustion air is sucked and compressed to supply the required amount of air, which in stoichiometric conditions is 5.58 Nm.³ of air per m³ biogas.

Prior to the metering of the fuel and ignition of the mixture with combustion air, an operation is carried out to empty the combustion chamber by means of pressurized air.

On the other hand, since the combustion chamber (30) of the burner operates totally submerged in the leachate to be heated, it must be made of special materials to withstand the chemical attack of the leachate and the combustion.

Even though a biogas is mentioned here as the main fuel used, any suitable fuel could be used to feed the at least one burner (3) which should only be equipped with the appropriate combustion nozzles, for example so that it can additionally work with gas. natural gas, propane gas or other fuels.

As indicated above, the combustion gases pass through the leachate to be heated in the form of small bubbles and, in addition to rapid and efficient heating, they produce agitation of the leachate, contributing to its homogeneity and avoiding fouling and achieving high energy efficiency.

As explained above, the evaporation process involves, so to speak, two phases, a first heating phase in which the temperature of the leachate volume confined in the respective evaporation chamber (2) is raised to exceed 50 ° C during this operation. the thermal utilization of the combustion gases is 100% since there is no wall between the fluids in contact, the size of the flue gas bubbles being small enough to achieve rapid heat transfer. Continued heating above 50 ° C, evaporation itself begins, and an optimal result is obtained at temperatures above 80 ° C, in this phase the heat of combustion supplies the latent heat of evaporation of the water, and with a large exchange surface between the “dry” gases resulting from combustion and leachate, so that the water is adsorbed by the emerging combustion gas through the gas outlet (21) of the respective evaporation chamber, containing approximately 1 kg of water per m³ smoke and the same water temperature.

The high turbulence created, the wide contact surface, and the absence of intermediate elements, maximize the use of energy and the combustion gases are used as a vehicle for transporting the adsorbed water; Furthermore, as a submerged combustion is carried out, it is not necessary to consider losses with the environment since the combustion gases carry out a direct exchange with the fluid, and the losses contribute to the preheating of the leachate.

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From the thermodynamic point of view, equilibrium will be reached for stoichiometric combustion conditions at 93 ° C, which is when all the heat supplied by the combustion process is converted into latent heat of vaporization.

As can be seen from the TS (Temperature-Entropy) curves of the water / water vapor of figure 6, the suitability of the system and of the process according to the invention are based on the realization of the phase change of the water at constant temperature , in such a way that it is not a boiling itself, but the combustion gas bubbles adsorb the water, loading themselves with moisture and therefore temperatures above 93 ° C are not reached at any time, so the occurrence of high temperature chemical reactions such as might occur with leachate in a furnace should not be feared.

Since the rising capacity of the smoke and water vapor mixture at that temperature is not very high, a forced draft can be carried out by associating an axial fan (210) with the gas outlet (21) of the respective chamber. evaporation (2) and thus favor the dilution of the vapor in the ambient air, before cooling and secondary condensation take place. Said axial fan makes it possible to change the pressure conditions on the surface of the gas outlet (21) to improve the evaporation performance.

Among the advantages of the leachate evaporation-adsorption process and system described above, the following can be mentioned:

Small size, most of the bulky elements of the installation are made to float on the surface of the water. The system can be adapted to any pond or leachate tank where there is a minimum depth.

The necessary civil work is minimal.

Evaporation performance is very high and will not depend on ambient conditions or air dryness for operation.

The maintenance of the system is very simple, and the most specialized part refers to the burners, which is limited to ensuring the cleaning of the UV sensor, flame detector and maintenance of the ignition electrodes. The remaining equipment in the system, such as blowers, fans, and valves, are low-maintenance.

The start-up and stop times are short and thanks to the redundant configuration, with at least three evaporation chambers and duplicate burners, the operating reliability of the system according to the invention turns out to be very high.

Furthermore, the system according to the invention is easily automatable and the evaporative adsorption process offers great flexibility, since the process and the rate of evaporation can be regulated.

A limitation of the system is given because submerged combustion is effective from a depth of 50 centimeters, otherwise it is not possible to make use of all the heat energy.

It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is therefore understood that this invention is not limited to the particular embodiment described, but is intended to cover modifications within the scope of the present invention as defined in the present description and following claims.