ES2686827B2 - LOW TEMPERATURE EVAPORATION CLEANING SYSTEM WITH CONDENSATION HEAT RECOVERY - Google Patents

Description

DESCRIPTION

LOW TEMPERATURE EVAPORATION CLEANING SYSTEM WITH CONDENSATION HEAT RECOVERY

SCOPE OF THE INVENTION

The invention falls within the technical sector of the purification of liquids from agro-industrial processes. More specifically, it focuses on the field of purification by evaporation at low pressure and temperature with heat recovery from condensation.

BACKGROUND OF THE INVENTION

The purification of effluents generated by industrial processes, particularly those of agri-food processing, is a matter of great technological interest because it conditions the activity as a consequence of the need to have large rafts for its accumulation.

At present there is no economically viable technology that allows reducing the contaminant levels of the liquids generated up to those legally permissible for public discharge. Chemical procedures eliminate solid particles and part of the pollutant load but the COD (chemical oxygen demand) and conductivity remain at much higher values than allowable. As for physical methods, they are based on the separation of water and other substances. On the one hand, in those of natural evaporation the results obtained are only satisfactory in very favorable atmospheric conditions, while the procedures based on distillation have as main drawback the energy expenditure necessary for the evaporation of the water present in the effluent .

The distillation of water present in the effluent is therefore considered an optimal solution provided that the net energy supply is drastically reduced. To achieve this purpose, two objectives are set, the first one to carry out low temperature distillation, which would allow the use of residual heat from industrial processes and / or solar energy. On the other hand, the partial recovery of the latent heat of vaporization that is provided to the effluent once the distillate condenses. In this way most of the energy provided is reincorporated into the process.

DESCRIPTION OF THE INVENTION

The invention of a system for the purification of effluents by evaporation at low temperature with heat recovery of condensation is presented. Evaporation at low temperature requires low pressure in the evaporation-condensation chamber, composed of the upper part of the pipes (1) and (17), the expansion vessel (19), the condenser (16) and one. The upper part of the pipes (1) and (17) is considered to be the portion above the 10.32 m level above the free level in the containers (10) and (18). To obtain the low pressure conditions described above, a low energy requirement vacuum generator has been designed.

Vacuum generator:

The vacuum generator is composed of two vessels, the first open to the atmosphere full of water (2) and the second (3) located at a height not less than 10.32 meters above the free water level in the previous one (2 ), both connected by a vertical pipe (4). The raised tank (3) is filled with water by means of the pump (5) keeping the aeration valve (6) open and the valves (9) and (7) that connects it with the expander tank (19) closed. Once full, the aeration (6) and filling (8) valves are closed, and the discharge valve (9) is opened. This results in the emptying of the pipe (4) and the generation of low pressure conditions inside the pipe and the raised container (3), when the valve (7) connecting to the expander (19) opens the pressure in It decreases. The process is repeated as many times as necessary until the steam pressure corresponding to the effluent temperature is reached in the expander (19), which will have risen through the pipes (1) and (17) to reach a height that balances the pressure in the feed containers of raw water (10) and purified water (18). In the operating phase, when an increase in the pressure in the evaporation-condensation chamber is detected, the low pressure regeneration process will automatically start.

Evaporation chamber condensation:

It is a sealed chamber, which will operate at low pressure and with two separate compartments in which the surfaces of the liquid-water vapor interface are located. In the upper part of the pipe (1) is the evaporation zone of the effluent. And in the upper part of the pipe (17) is the water vapor condensation zone.

Since the evaporation process can be in the form of a "flash", or bubbles can be produced that drag effluent in liquid form, to avoid said effluent passage to the condenser (16) an expansion tank (19) with deflector sheets (15) arranged so as to hinder the passage of liquid and not that of steam.

Calorific system:

For the correct operation of the invention it will be necessary to provide the heat of evaporation in the pipe (1) while evacuating the heat of condensation in the condenser (16). In order to make the calorific contribution, a hot water accumulator (11) is provided, equipped with an electric heater (12) powered by a photovoltaic solar system (20). The circulating pump (14) generates a flow of hot water through a jacket that wraps the pipe (1) that houses the effluent. The heat necessary for evaporation is transferred through the wall of this pipe.

The water vapor occupies a pipe in the form of a coil or condenser (16) immersed in a container (13) through which the effluent contained in the raw water feed container (10) is circulated, thus the steam of water condenses and yields the heat of condensation to the effluent by preheating it. The condensed water falls through the pipe (17) to the reservoir (18) that accumulates the purified water.

The recovery of heat of condensation to re-enter it in the heating of the effluent will allow the process to be almost autonomous from the energy point of view, being necessary to contribute to the system only the heat ceded to the environment as losses. This recovery is carried out by means of the pump (21) that raises cold effluent to the container (13), where the coil (16) is immersed, returning the heated effluent to the tank 10 through the pipe (22)

DESCRIPTION OF THE DRAWINGS

To complement the description of this invention and facilitate the compression thereof, a set of figures is attached where, for illustrative and non-limiting purposes, the following are represented:

Figure 1. Scheme of system principle.

Figure 2. Cross-sectional view of the expansion tank (19) provided with baffle plates (15).

PREFERRED EMBODIMENT OF THE INVENTION

The present invention relates to an effluent purification system by evaporation at low temperature with recovery of condensation heat. Figure 1 shows an overview of the system, which is composed of a raw or effluent water tank (10) on which a stainless steel pipe (1) of at least 10.32 meters in height is placed, ending in a expander vessel (19) equipped with baffles (15) with the purpose of preventing liquid entrainment towards the condenser (16). To achieve a low temperature evaporation the pressure needs to be lowered, these conditions are achieved with an atmospheric vacuum generator consisting of a water tank (2), a column at least 10.32 meters high (4), a tank raised (3) and a filling pump (5). Successive filling and emptying processes obtain the desired pressure in the evaporation-condensation chamber. When the vapor pressure is reached, to keep the evaporation process active it is necessary to provide heat, for this purpose a larger diameter pipe is used on which the effluent contains, thus configuring a jacket through which hot water will circulate in a closed circuit. The heating of the water is carried out in an accumulator tank (11) in which an electrical resistor (12) is fed by a set of photovoltaic panels (20). An electric pump (14) circulates the hot water through the jacket so that heat is transferred through the wall of the pipe containing the effluent. Once the process is started by which the water contained in the effluent evaporates, it passes in the form of steam to a coil-shaped pipe (16) immersed in the effluent liquid contained in a container (13). In this way, the water vapor contained in the coil condenses and yields the heat of condensation to the effluent that is taken to the raw or effluent water tank (10) with a temperature higher than that of the inlet. The condensed steam accumulates in the purified water pipe (17), placed on the purified water tank (18).

Claims (1)

1. Effluent purification system at low temperature, in which evaporation and condensation is carried out in an atmospheric vacuum chamber, maintained by the weight of liquid columns, characterized by the incorporation of an expansion tank (19) equipped with deflector blades (15) preventing the entrainment of liquid effluent from the pipe (1) to the condenser (16).