PROCESS FOR CONTROLLING AND REGULATING THE INJECTION OF CO2 IN ORDER TO TREAT AN EFFLUENT

Abstract

A process for treatment of an effluent, which comprises an injection (3) into the effluent, of CO.sub.2 or of a mixture comprising CO.sub.2, comprising: a. a measurement of the pH (6) of the effluent is carried out upstream of the point of injection of the CO.sub.2 or of the mixture in the process; b. a curve of dose of CO.sub.2 to be injected as a function of the pH of a medium for a predetermined volume in litres or in cubic metres was determined beforehand, and this curve is entered into a regulator or automaton (4) capable of controlling the operation of the process; c. the presence of a flow of effluent to be treated is detected, and the dose of CO.sub.2 or of mixture, determined by said curve and multiplied by the flow rate of effluent to be treated, is injected.

Claims

1. A process for treatment of an effluent, which comprises an injection (3), into the effluent, of CO.sub.2 or of a mixture comprising CO.sub.2, comprising the steps of: a) carrying out a measurement (6) of the pH of the effluent upstream of the point of injection of the CO.sub.2 or of the mixture; b) determining a curve of dose of CO.sub.2 to be injected as a function of the pH of a medium for a predetermined volume in litres or in cubic metres beforehand; c) detecting a flow of the effluent to be treated, and injecting the dose of CO.sub.2 or of the mixture, wherein a value of a flow rate of the effluent existing at the inlet of the process is available; d) reading on said curve, the dose of CO.sub.2 corresponding to the measured pH, wherein a calculation is made of a flow rate of CO.sub.2 to be injected as a function of an incoming effluent flow rate; e) injecting said flow rate of CO.sub.2 or of the mixture into the effluent; and f) regulating the injected flow rate of CO.sub.2 at a setpoint value determined in step d).

2. The process of claim 1, further comprising entering the determined curve into a regulator or automaton (4) capable of controlling the operation of the process.

3. The process of claim 2, wherein the curve is determined by calculations.

4. The process of claim 2, wherein the curve is determined from experimental tests.

5. The process of claim 1, wherein the detecting step c) includes setting a pump going.

6. The process of claim 1, wherein the detecting step c) includes detecting a flow by a flowmeter.

7. The process of claim 1, wherein the dose of CO.sub.2 or of the mixture is determined by said curve and multiplied by the flow rate of the effluent to be treated.

8. The process of claim 1, wherein the ratio of the flow rate of CO.sub.2 and the incoming effluent flow rate corresponding to said dose.

9. A system for treatment of an effluent; carrying out an injection (3), into the effluent, of CO.sub.2 or of a mixture comprising CO.sub.2, comprising: i) a pH measurement means (6) configured and adapted to measure the pH of the effluent, which is located upstream of the point of injection of the CO.sub.2 or of the mixture in the system; ii) a pump or a flowmeter, configured and adapted to detect the arrival of a flow of the effluent to be treated; iii) a device configured and adapted to measure the flow rate of the effluent to be treated existing at the inlet of the system; and iv) a regulator or automaton (4) configured and adapted to be capable of controlling the treatment, as a function of its analysis of a curve of dose of CO.sub.2 to be injected as a function of the pH of a medium for a predetermined volume in litres or in cubic metres, the automaton configured and adapted to be capable of carrying out the following actions of: reading, on said curve, the dose of CO.sub.2 corresponding to the measured pH.sub.; and calculating the flow rate of CO.sub.2 to be injected as a function of the incoming effluent flow rate; ordering the injection of said flow rate of CO.sub.2 or of the mixture into the effluent; and regulating the injected flow rate at a setpoint value determined during said calculation.

10. The system of claim 9; wherein the curve is obtained by calculations.

11. The system of claim 9, wherein the curve is obtained from experimental tests.

12. The system of claim 9; wherein the ratio of the flow rate of CO.sub.2 and the incoming effluent flow rate corresponding to said dose.

13. The process of claim 9, wherein the dose of CO.sub.2 or of the mixture is determined by said curve and multiplied by the flow rate of the effluent to be treated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0046] FIG. 1 illustrates an installation employing a standard solution according to the prior art.

[0047] FIG. 2 for its part illustrates an installation which makes it possible to implement the present invention.

LIST OF ELEMENT NUMBERS

[0048] The following elements are recognized in the figures: [0049] 1: entry pit [0050] 2: pump [0051] 3: injection of CO.sub.2 (in the pipeline 7) [0052] 4: automaton [0053] 5: outlet basin (optional) [0054] 6: a pH measurement carried out in the outlet basin [0055] 7: pump outlet pipeline [0056] 8: neutralized effluent outlet

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0057] The following implementational example should be considered: It is concerned with neutralizing an effluent which arrives in the entry pit 1, with a working volume of 2 m.sup.3.

[0058] The flow rate of incoming effluent is in the vicinity of 30 m.sup.3/h and the flow rate of the pump 2, which makes it possible to empty the entry pit, is in the vicinity of 80 h.

[0059] In short, when the pit contains 2 m.sup.3 of effluent, the pump is set going and empties the pit. At the flow rate of the pump, the emptying takes place in a little more than 2.5 minutes.

[0060] Due to the flow rate of effluent which arrives on the pit, this emptying sequence takes place approximately 15 times per hour.

[0061] The pipeline 7 at the pump outlet makes it possible to deliver the effluent at approximately 150 m from the entry pit into an open-air inspection hole of approximately 1 m.sup.3.

[0062] The pipeline is buried over virtually the whole of its course. It has a diameter of 120 mm in order to observe the optimum hydraulic conditions for mixing with a view to neutralizing the effluent. Due to its diameter and its length, the volume of effluent contained in this pipeline between the outlet of the pump and the outlet basin is of the order of 1.7 m.sup.3.

[0063] Over a “standard” neutralization, the acid injected, in this instance CO.sub.2, is regulated from the pH measurement located at the pipeline end (6), in this instance in the outlet basin. By definition, this basin is at a pH close to neutrality since it corresponds to the final discharged product. During start-up of the emptying pump, it is necessary for a more or less large part to arrive in this basin in order for the pH to increase and for the order for injection to be given to the regulator 4. Consequently, before the CO.sub.2 is injected into and mixed in the effluent, a large part of the volume of effluent from the pipeline will be poured into the outlet basin without being treated and thus into the natural environment or into the drainage system, due to the small size of the outlet basin.

[0064] In this example, as the volume contained in the pipeline is close to 1.7 m.sup.3, and the hourly frequency of start-up of the pump close to 15 times per hour, between ⅔ and ¾ of the effluent will not be correctly treated with a neutralization regulated in a standard manner in-line.

[0065] In order to overcome this problem, the injection of CO.sub.2 might be forestalled but then, as the injection is no longer directly proportional to the requirement, the risk exists of overacidification or of overconsumption.

[0066] Of course, it is also possible, in order to solve the problem, to produce a large-sized outlet basin, in order “to dampen” the frequent start-ups of the pump, but this cannot always be carried out due to problems of spatial requirements and/or of cost.

[0067] In FIG. 2, an unvarying incoming effluent flow rate is assumed. Consequently, it is not necessary to include a flowmeter in the installation.

[0068] The same operating conditions should then be considered here as above, that is to say: [0069] A flow rate of effluent to be neutralized of approximately 30 m.sup.3/h. [0070] An entry pit with a working volume of 2 m.sup.3, and thus, when there are 2 m.sup.3 of effluent in the pit, the emptying pump is set going. [0071] The pump has a fixed flow rate of 80 m.sup.3/h; consequently, it will be started up approximately 15 times per hour in our example. [0072] A buried pipeline with a diameter of 120 mm, i.e. a residual effluent volume in this pipeline of the order of 1.7 m.sup.3. [0073] A discharge basin before the discharge into the natural environment or into the drainage system with a working volume of approximately 1 m.sup.3.

[0074] In accordance with the present invention, the method of regulation proposed operates in the following way: [0075] The pH of the effluent is measured upstream of the injection of CO.sub.2 into the pipeline (in this instance, the pH is measured in the entry pit and the acid to be injected is CO.sub.2) [0076] A curve corresponding to the dose of CO.sub.2 to be injected for a volume of effluent (1 litre, 1 m.sup.3) was predefined and entered in the regulator/automaton (predefined, for example, by tests carried out upstream) [0077] At start-up of the pump, an optional rate valve opens to make possible the injection of the CO.sub.2; the amount injected corresponds to the preestablished dose multiplied by the effluent flow rate (measured flow rate, or flow rate of the pump), the opening being determined by the automaton/regulator. [0078] At shutdown of the pump or in the absence of an incoming flow of the effluent, the injection of CO.sub.2 is interrupted by closure of a valve or by any other shutdown means.

[0079] With this method of regulation, all of the effluent contained in the pipeline is neutralized from the start-up of the emptying pump and the discharges are always in accordance without modification of the installation (no need to enlarge the outlet basin, for example).

[0080] The present invention then relates to a method for the treatment of an effluent, which comprises the injection, into the effluent, of CO.sub.2 or of a gas mixture comprising CO.sub.2, being characterized by the implementation of the following measures:

[0081] a) a measurement of the pH of the effluent is carried out upstream of the point of injection of the CO.sub.2 or of the mixture, in the process;

[0082] b) a curve of dose of CO.sub.2 to be injected as a function of the pH of a medium for a predetermined volume in litres or in cubic metres was determined beforehand, a curve determined, for example, by calculations or from experimental tests, and this curve is entered into a regulator or automaton capable of controlling the operation of the process;

[0083] c) the presence (the arrival) of a flow of effluent to be treated is detected, for example by setting a pump going or also by the detection of a flow using a flowmeter;

[0084] d) the value of the flow rate of effluent existing at the inlet of the process is available;

[0085] e) the dose of CO.sub.2 corresponding to the measured pH is read on said curve, and a calculation is made of the flow rate of CO.sub.2 to be injected as a function of the incoming water/effluent flow rate, the ratio of flow rates corresponding to said dose;

[0086] f) said flow rate of CO.sub.2 or of mixture is injected into the effluent;

[0087] g) the injected flow rate is regulated at the setpoint value determined in stage e).

[0088] The present invention also relates to an installation for the treatment of an effluent, carrying out the injection, into the effluent, of CO.sub.2 or of a mixture comprising CO.sub.2, comprising:

[0089] i) a means for measurement of the pH of the effluent, which means is located upstream of the point of injection of the CO.sub.2 or of the mixture in the installation;

[0090] ii) a means of detection of the arrival of a flow of effluent to be treated, for example a pump or also a flowmeter;

[0091] iii) a means for measurement of the flow rate of effluent to be treated existing at the inlet of the process;

[0092] iv) a regulator or automaton capable of controlling the treatment, as a function of its analysis of a curve of dose of CO.sub.2 to be injected as a function of the pH of a medium for a predetermined volume in litres or in cubic metres, a curve obtained, for example, by calculations or from experimental tests, the automaton being capable of carrying out the following actions: [0093] of reading, on said curve, the dose of CO.sub.2 corresponding to the measured pH, and of calculating the flow rate of CO.sub.2 to be injected as a function of the incoming effluent flow rate, the ratio of flow rates corresponding to said dose; [0094] of ordering the injection of said flow rate of CO.sub.2 or of mixture into the effluent; [0095] of regulating the injected flow rate at the setpoint value determined during said calculation.

[0096] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0097] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0098] “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined here n as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of” or “consisting of” and remain within the expressly defined scope of “comprising”.

[0099] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0100] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0101] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0102] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

[0103] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.

[0104] While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.