FR2791972A1 - PROCESS FOR REGULATING THE TREATMENT AND CONDITIONING OF FEED WATER FOR BOILERS, HOT CIRCUITS OR STEAM GENERATORS - Google Patents

Abstract

The invention concerns a method for regulating the treatment and conditioning of feed water of boilers or steam generators and any type of heating system. The invention is characterised in that it consists in measuring a characteristic parameter of the content of dissolved oxygen in the system, then in converting the measurement of said parameter using a computational algorithm into a value representing the amount of oxygen, then on the basis of the chemical equation for determining the amount of agents reducing or inhibiting the amount of oxygen, in measuring out and injecting the inhibiting agent(s) into the system.

Description

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  The present invention relates to a process for regulating the treatment and conditioning of boiler feed water, hot circuits, as well as steam generator water, and circuits working at low, medium and high pressure, etc. It is well known that natural waters are unsuitable especially for the supply of boilers

  working at low, medium and high pressure.

  Oxygen and carbon dioxide are responsible for serious corrosion phenomena in the circuit

  supply, boiler and steam network.

  Mineral salts and organic matter will, under the effect of temperature and concentration, precipitate in the form of scale and sludge which impede good heat exchange, which reduce yields, increase fuel consumption and create overheating. which may cause the explosion and / or the

destruction of materials.

  The risk of corrosion is further accelerated by the pH reached in the boiler, when it is too high or too low. The carbon dioxide from the decomposition of bicarbonates and carbonates dissolves in condensed water as soon as the temperature drops below 900C. This dissolution corresponds to the formation of carbonic acid which is responsible for corrosions and

  pits in condensate networks.

  The protection of boilers and circuits therefore requires the incorporation in steaming water and in generator water of a corrosion inhibiting agent such as a simple or combined oxygen reducer (mineral or organic) or associated with one or other agents (phosphating, basifying, dispersing or other ...) in order to create

protective conditions.

  These additives make it possible to carry out a complete treatment which ensures the reduction of oxygen, the maintenance of the pH, the maintenance of the mineral salts (in a dispersed nonadherent form, easy to evacuate by one or more

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  purges), protection of metal surfaces as well as

  neutralization of carbon dioxide.

  The known methods for dosing the amount of additives to be incorporated into water are mainly of two types: - a first method consists of injecting additives into the cold make-up water using a pump doser, this dosage being a function of the flow rate; a second method also consists in injecting additives into the drinking water of the steam generator, as a function of an evaluation of the average temperature of the water in the circuit, resulting from a

  knowledge of back-ups and condensate returns.

  However, these types of processes lead to: - inertia problems; - problems of heterogeneity; - problems related to the fluctuation of the

  temperature at the level of the food cover.

  The main drawbacks of the known methods of the prior art reside in the fact that they are empirical, that they do not take reality into account: steam generators being rarely used, in steady state around a set range determined, due to night or day stops, end of

  week, use of various processes, etc ...

  The injection of the inhibitor product is therefore done by taking a safety margin necessary to maintain the quantities of excess inhibitor and generally this margin is calculated for the most unfavorable case (lowest temperature of the installation or circuit) , these excess injections lead on the one hand undoubtedly to overconsumption and additional costs in products and on the other hand to a deterioration of the environment and an additional cost of energy linked to the need to increase the purges of

devolution.

  The present invention therefore aims to overcome these drawbacks by proposing a method for regulating the treatment and conditioning of feed water.

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  of boilers and boiler water which applies to all operating conditions of the installation (temperature, operating, flow variations, etc.). To this end, the process for regulating the treatment and conditioning of the feed water of a boiler and of the boiler water is characterized in that it consists in measuring a characteristic parameter of the oxygen content. dissolved in the supply circuit, then to convert the measurement of this parameter using a calculation algorithm into a value representative of the quantity of oxygen, then according to the chemical equation allowing the quantity to be determined agent ensuring the reduction or inhibition of the quantity of oxygen, to carry out the metering and injection of

the inhibiting agent in the circuit.

  Other features and advantages of this

  invention will emerge from the description given below, in

  reference to the accompanying drawings which illustrate an embodiment thereof devoid of any limiting character. In the figures: - Figure 1 is an abacus giving for various temperature values the quantity of oxygen dissolved at a given pressure; (according to another operating mode, not shown in the figures, the method will also integrate

the concept of circuit pressure).

  - Figure 2 is a diagram of an installation that can

  be equipped with the regulation method which is the subject of the invention.

  According to a preferred mode of an installation allowing the implementation of the process which is the subject of the invention, this consists in providing for a measurement of a physicochemical parameter, at any place on the circuit of the installation, located in particular at the level of the steam generator supply line or at any other point deemed suitable to give a significant value of the physico-chemical state of the water

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  boiler food. This measure may consist

  for example in a temperature measurement.

  Depending on this measurement of the physical-

  chosen chemical, and in particular in our case of temperature measurement, we can determine the concentration or

  the solubility of dissolved oxygen in the medium.

  This determination of the quantity of oxygen dissolved in the medium can be obtained by means of an abacus (for example cf. FIG. 1) which provides for different values

  of temperatures, the concentration of dissolved oxygen.

  Other charts take into account other parameters such as

the pressure parameter, etc ...

  Of course, the values of these charts can be tabulated or worked out following a mathematical calculation resulting from the equation of curves obtained experimentally. Then, a dosage of the corrosion inhibitor product (essentially an oxygen reducer) to be injected into the circuit is developed as a function of the stoichiometry of the chemical reaction, taking into account the

  actual concentration of dissolved oxygen in the medium.

  This determination of the precise need for a corrosion inhibitor can be effectively carried out using a regulator which integrates within its circuits the various values of the parameters necessary for this determination (measurement of temperature, pressure, calculation of the concentration...). Controlling the dosage of the inhibitor product is carried out in particular as a function of the temperature of the water circulating in the circuit

  the steam generator.

  The injection of the inhibitor product can be carried out at any point in the food circuit or at any other point deemed capable of giving a significant value for the physicochemical state of the food water of the

boiler or circuit.

  Reference may be made to FIG. 2 which represents the diagram of a typical installation which may include the process.

  the subject of the invention.

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  The reference 1 represents the food cover into which the make-up water circuit 2 opens, as well as the water from the condensate returns 3. The water from the food cover 1 is introduced into a steam generator 4 by the via a food pump 5 arranged on the food water circuit 6. From this steam production enclosure 4, is connected a steam starting circuit 7. This steam can be lost 8 or recovered 9

  after use depending on the process.

  This recovered steam (in the form of condensates) is conveyed to the food cover 1 by

  via a condensate return circuit 3.

  The measurement of the physico-chemical parameter can be carried out on any point of the circuit located between 1 and 4, in particular at the level of the aspiration or the

  delivery of the food pump 5.

  In another case, the measurement of the physico-chemical parameter can be the result of several measurements carried out at various places in the circuit (for example, at the top and at the return, in different tarpaulins

intermediaries, etc.).

  The process which is the subject of the invention offers multiple advantages because it applies to all the operating conditions of the installation (variations in temperature, operation, flow rate, etc.). In addition, the injection is carried out strictly according to the precise application requirements of the selected inhibitor product (s), which necessarily leads to savings, in the pre-treatment, treatment, fuel consumption, while contributing to environmental protection by reducing the volume

purges.

  At the same time, this process will allow the user to comply with the physico-chemical water / steam instructions as a function of those requested by the manufacturer, including in particular the pH, TA, TAC, SiO2 values, excess of phosphates, excess of reducing agent, excess dispersant,

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  total salinity, Si02 / TAC ratio, as well as optimize

operating conditions.

  Thus, for example in the case of a boiler supplying a hospital laundry room: - at the end of the week, shutdown of the installation, therefore no injection of inhibitor product; - on Monday, start of the installation, maximum injection, then gradual depending on the temperature, until the steady state is obtained; - from Tuesday to Friday, injection of the product depending on night and day fluctuations; - Friday, increase in injection to compensate for the weekend stop, taking into account the decrease

  significant temperature during the weekend.

  It remains to be understood that the present invention is not limited to the exemplary embodiments described and shown above, but that it encompasses all variants thereof.

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Claims (4)

  1 - Process for regulating the treatment and conditioning of the water supplying boilers or steam generators as well as any hot circuit, characterized in that it consists in measuring a characteristic parameter of the dissolved oxygen content in the circuit, then to convert the measurement of this parameter using a calculation algorithm into a value representative of the quantity of oxygen, then according to the chemical equation making it possible to determine the quantity of agents ensuring reduction or inhibition of the amount of oxygen, to perform the dosage and injection of   or inhibitory agents in the circuit.   2 - Method according to claim 1, characterized in that the measurement of the characteristic parameter of the dissolved oxygen content in the circuit consists in particular of a temperature measurement.   3 - Method according to one of claims 1 or 2,   characterized in that the injection of the inhibitor product (s) is carried out at any point deemed suitable for giving a significant value of the physico-chemical state   food water from the boiler or circuit.   4 - Method according to any one of claims   previous, characterized in that the measurement of the characteristic parameter of the dissolved oxygen content in the circuit is developed following the result of several measurements carried out at various places in the circuit