Method and equipment for the treatment of water contaminated by thermal oil and collection of said oil

Abstract

The invention relates to a method for the treatment of water contaminated by thermal oil and collection of said oil (for example, a eutectic mixture of biphenyl and diphenyl oxide), formed by a cooling phase (2) for cooling (to a temperature between the freezing point of the thermal oil and that of water) the mixture (1) of water and thermal oil, followed by the collection (3) of the part (4) of frozen thermal oil (precipitated or in suspension) by means of mechanical filtering. The remainder of contaminated water is treated in absorption filters and in activated carbon adsorption filters. The equipment required to implement this method comprises a cooling unit, a unit for the separation of phases by means of mechanical filtering for the collection (3) of the frozen thermal oil part (4), a unit (6) of absorption filters and a unit (7) of adsorption filters (activated carbon unit).

Claims

1. A method for the treatment of water contaminated by thermal oil and collection of said oil, of the type used in solar thermal equipment and with a freezing temperature of the thermal oil above 0 C., of a mixture (1) of thermal oil and water, characterised in that it comprises the stages of: a) Cooling (2) of the mixture (1) below the freezing temperature of the oil; b) Collection (3) of the part (4) of thermal oil precipitated or in suspension in the contaminated water (5); c) Treatment of the contaminated water (5).

2. The method, according to claim 1, characterised in that the treatment of the contaminated water (5) is carried out by means of the following stages: a) Absorption filtering of the contaminated water (5); b) Adsorption filtering, using active carbon, of the contaminated water from the absorption filter (6).

3. The method, according to claim 1, characterised in that the collection of the thermal oil part (4) comprises mechanical filtering.

4. The method, according to claim 3, characterised in that the mechanical filtering comprises a series of metal filters graded in descending order, down to a mesh size of 25 m.

5. The method, according to claim 1, characterised in that cooling is performed down to a temperature of between 0 C. and 12 C.

6. The method, according to claim 5, characterised in that cooling is performed down to a temperature of between 0 C. and 5 C.

7. The method, according to claim 6, characterised in that cooling is performed down to a temperature of between 3 C. and 4 C.

8. The method, according to claim 1, characterized in that the thermal oil is a eutectic mixture of biphenyl and diphenyl oxide.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) For the purpose of making the invention more readily understandable, FIG. 1 has been included, which shows the method for treating water contaminated by thermal oil and collection thereof.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(2) What follows is a brief description of an embodiment of the invention, by way of illustration and not limitation, using the attached FIGURE as a reference.

(3) In order to collect the thermal oil and treat the water, the water treatment and oil collection process has a first phase common to both objectives, which is cooling (2).

(4) The mixture (1) of contaminated water and thermal oil is cooled to a temperature lower than the freezing point of thermal oil. In this manner, the non-soluble part of the thermal oil solidifies in water. On solidifying, it precipitates at the bottom of the enclosure where cooling takes place (2), whereupon this part (4) of the thermal oil can be collected (3), which is greater in economic terms than the part that remains in the contaminated water (5). Additionally, the treatment of the water becomes cheaper upon having removed part of the thermal oil.

(5) The remainder of the thermal oil in the water remains dissolved or in the form of traces. Thanks to the cooling (2), it favours the formation of crystals of the dissolved fraction of water, which will optimise the subsequent treatment method.

(6) Cooling (2) can take place in multiple ways.

(7) In order for the contaminated water (5) to flow out of the cooling chamber with the remainder of the dissolved thermal oil, metal filters graded in descending order, down to a mesh size of 25 m, will be disposed. These filters will aid the collection (3) of the solidified thermal oil.

(8) The method is aided by pumps, so that the water circulates under pressure and can penetrate all the filters, with the ensuing pressure drop.

(9) The temperature up to which the oil and water mixture (1) must be cooled depends on the degree of effectiveness to be achieved in the treatment process. Reducing it to below its freezing point will allow collection thereof.

(10) In the case of the eutectic mixture of biphenyl and diphenyl oxide, the freezing temperature is 12 C., below which the thermal oil can be collected. Better results are obtained below 5 C., but guaranteeing the non-freezing of the water. An optimum working temperature for this thermal oil would be 3 C. to 4 C.

(11) Upon completing the cooling phase, the frozen thermal oil can be removed by means of the aforementioned mechanical filtering process, for the subsequent reuse thereof. In this manner, the collection objective of most (4) of the thermal oil discharged into the water will have been achieved. The contaminated water will continue to a treatment phase such as that described below.

(12) In order to proceed to treat the contaminated water (5), the method continues with its flow through oil absorption filters (6). The absorption filters (6) can be radial (such as those marketed under the brand OilBlock (produced by Twin Filter B.V., The Netherlands)), to absorb the thermal oil, which is aided by the water temperature, which has caused the thermal oil to crystallise. In this manner, it is not difficult to obtain filtering performances of approximately 99%.

(13) In turn, the result, after precipitation by cold and filtering by absorption, has a very homogeneous pollutant concentration, practically independent from the initial amount of thermal oil, thereby optimising the following phase, passage through the adsorption filters comprised in an active carbon unit (7).

(14) In the active carbon unit (7) the odours and colours of the water, and the possible remainder of contamination of the water, are removed by means of adsorption. As in the previous phase, the performance of the active carbon increases upon coming into contact with the cold water.

(15) Due to the homogenisation of the concentration of the contamination on flowing out during the absorption filtering phase, stable retention times can be established in the active carbon unit, the last phase not being subject to concentration fluctuations. Likewise, it will allow better planning for the replacement or regeneration of the active carbon once it is saturated.

(16) Upon flowing out during the absorption filter phase, the concentration of the thermal oil in the water is very small, due to which the adsorption filters and residence times therein to obtain values below the environmental standards can be designed. The product can already be considered treated water (8).

(17) Therefore, the equipment required to carry out this method will comprise a cooling unit, phase separation unit (mechanical filtering) for collecting (3) the part (4) of thermal oil precipitated or in suspension in the contaminated water (5), an absorption filter unit (6) and an adsorption filter unit (active carbon unit (7)).