DE2452863A1 - DEVICE FOR THE AUTOMATIC CONTROL OF ALKALINITY IN EVAPORATION SYSTEMS - Google Patents

Description

1 BERLIN 33 8MUNCHEN80

ÄTJXÄE, Dr. RUSCHKE & PARTNER. ^ T

ouf ^A R ⁿ u ^w sch ^D _k ^! e ^pWng · PATENTANWÄLTE ^Han · ^Ε ·

Teiefon: 030/1 »« »BERLIN -MÖNCHEN ^Telephone:

Telegram address: Telegram address:

Quadrature Berlin Qudadrrtur monks TELEX: 18378 «TELEX: 522767

N 713

Naloo Chemical Company, Oak Brook, Illinois, USA

Device for the automatic control of the alkalinity in evaporation systems

The invention relates to a device for automatic control the alkalinity in evaporation systems. In particular, the invention relates to an automatic control device or regulation of the value of the alkalinity of the recirculated water from open cyclic evaporation systems.

»As is well known, in these systems the water is normal- · wisely treated with chemical additives to the heat exchange surfaces to protect against corrosion, scale formation, slime deposits and the like.

In the past, most of the chemical Actions of the recycled water in open cyclic evaporation systems involve the use of an acid, usually Sulfuric acid to regulate the pH of the returned water and thus prevent the formation of calcium salt stone. The! Eeohniken used included the hourly injection. an amount of acid in the system based on the flow rate of the build-up water with reference to the alkalinity

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of this water under reaction with methyl orange (hereinafter referred to as alkalinity M), the concentration ratio of the build-up water and the previously determined alkalinity II for the returned water was calculated. The alkalinity 'M for the "returned water is calculated" and fixed for each individual cooling system, usually to the value whichever corresponds to the beginning of low corrosive activity in the system.

This activity is neutralized by injecting one or more corrosion inhibiting substances into the system.

In most of the acid and corrosion inhibitor-treated cooling systems, the desired value of the alkalinity E of the recycled water has been fixed in the range of 30-100 ppm (as CaCO ^). In industrial practice, the injection of acid necessary to maintain this alkalinity M of the water of the system * ¹ is adjusted as close as possible to the desired value based on the pH values found in the returned water - this is possible if the values of the alkalinity M are kept within this interval of 30-100 ppm, there being a real relationship between the values of the alkalinity M and the pH values in the water of the cooling system.

The relationship is shown in the following Table 1 (Examples 1 and 2).

Table 1

Water analysis of a cooling system at different concentrations the alkalinity M

Example 1 - cooling water system A alkalinity H, ppm ale CaGO,

Total hardness, ppm as GaCO, OalQium hardness, ppm as CaCO, Sulphates, ppm as SO ^ chlorides, ppm as Eq

30th 60 6.8 7.2 970 950 635 620 610 590 470 460

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45 70 7.0 7.4 430 450 300 330 490 460 • 75 85

Example 2 cooling water system B

Alkalinity M, ppm as CaGO,

Total hardness, ppm as CaCO., Calcium hardness, ppm as CaCO, Sulfates, ppm as SO.

Chlorides, ppm as Cl

In particular, the above table illustrates the fact that j • that in the cooling systems with a return of the cooling water, j if the viferte of the alkalinity M are kept below 100 ppm I

the pH of the if / water of the system should be remarkable Measures changes, including for variations in alkalinity M from 20-30 ppm. This between the fourth of the pH and the alkalinity M existing relationship is largely with this guy! of cooling systems for the regulation of the alkalinity M by means of the; pH control and vice versa have been exploited. This is evidenced by the widespread use of devices for Measurement and regulation or control of the pH and to regulate the supply of acid in cooling systems of the type in question.

A new method of treating recycled water in evaporative cooling tower systems has recently become economical Success found and is largely applied. This System, called alkaline treatment, requires the use of scale inhibitors, which prevent the deposition of Able to prevent calcium salts on the surfaces of heat exchanger walls. The addition of the scale inhibitor to the returned water also allows the cooling system to operate under conditions where "scale formation" is possible, i.e. at higher values of the alkalinity E and values of the pH and of calcium ions that are higher than the limit saturation values of the Calcium carbonates lie. When this treatment is used, the corrosion of the metal parts of the device is depleted Plant down to a minimum, because both a thin protective layer of calcium carbonate and all of the carbon steel are formed these parts are made passive with respect to the pH induced in the cooling system.

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u ± e l ^ -forw functions relating to these alkaline treatment systems are shown in Table II below (Examples 3 and 4).

Table II

Example 3 - .cooling water system Q Alkalinity M, ppm as OaCO,

Total hardness, ppm as CaCO., OaIorum hardness, ppm as OaCO, Sulfates, ppm as SO.

Chlorides, ppm as Cl

Example 4 - Cooling Water System D Alkalinity M, ppm. as CaCO. *

Total hardness, ppm as CaCO., Calcium hardness, ppm as CaCO, Sulphates, ppm as SO, chlorides, ppm as Cl

190 300 ö, 4 8.6 1100 1030 860 830 6? 0 480 900 " 850 250 l? 0 8th,? 8.0 480 510 350 350 120 260 170 185

As can be seen, Table II shows the characteristics of the recirculated water from two cooling systems with evaporation towers which have been subjected to the "alkaline treatment". In general, the alkalinity M of the returned water is in the range 100-400 ppm (as CaCO. *) In ^{this I 1 ^ II.} The "best value of this alkalinity within the limits of this interval varies for each system treated, depending on the nature and type of the build-up water and the operating conditions."

Once the optimal value of the alkalinity M for a well-defined It is important to keep this alkalinity as close as possible and at all times with this system Worth holding.

In practice, if the value of the alkalinity M is substantially lowered, a problem of corrosion arises; if

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aiiWill such a state continue beyond a "warning value" is left is the control and regulation of the scale formation difficult.

So far, one of the main problems faced by the experts has been the correct automatic regulation of the alkalinity M of the returned tank by injection of acids, because the values of the alkalinity M within the range of the for the "alkaline treatment" The relationship between Al Minity H and the pH of the returned water shows that a change in Al ^{! r} ai.initat M can correspond to a slight change in pH.

Examples ¹ ^ and 4 of Table II show a typical situation in a cooling tower system where the alkaline treatment is applied. For example, it can be found that a change in alkalinity M of 110 ppm corresponds to a change in pH which is only zero , 2 units.

It is now clearly recognizable what the disadvantage is associated with such an alkaline treatment, namely the noticeable difficulty of regulating the alicalinity M by adjusting the pH of the system of the returned water. In practice, the systems commonly used to measure pH in cooling tower systems can determine the pH of the recirculated water within an interval of £ 0.2 units of the predetermined value and variations in alkalinity M- far greater than those for a satisfactory embodiment dea "alkaline ■ program", tolerable, often correspond to this fluctuation.

The main object of the invention is therefore to design a device for automatic regulation and control of the alkalinity of the returned water in open evaporation systems, if

> 100 ppm (as GaGO,) are present; this device should

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can eliminate the named special risks or disadvantages that occur with a small and large increase in alkalinity above the "V / am values", which we ^ the insufficient sensitivity of pH meters, as they are conventionally used, cannot be determined and controlled.

Advantage of the erf in manure contemporary device is the possi bility that they "indicate also be used in babble, where the to be maintained alkalinity M niedri & does. (30-100 rrm as CaCO ^)» wherein the alkaline treatment nor satisfactory "/ iron can be used (for example in the case of acids with high concentrations of O

In practice, the performance according to the invention allows the determination the instantaneous value of the alkalinity M of the system in regular intervals and at any time for a predetermined one Time period; when the “vert of this alkalinity exceeds the "Warn" -v '/ ert, a pump in Okm ^' is occupied for the purpose of supplying the acid, for example sulfuric acid, and the Operation for the entire duration of the period specified in advance upright - held.

Special subject matter of the invention is therefore a device for automatic regulation, the alkalinity of the returned water from evaporation systems, which in combination contains: means equipped with a stirrer for collecting a predetermined volume of the hater of the system, which in a Sampling line used with continuous water flow are; Means for opening and closing these collecting means at programmed regular time intervals determined by timers regulated by solenoid valve means; Dosing and charging means for titrating to a specific acid value in these collecting means; associated with these drugs Means for measuring the pH of the water in the system to be analyzed; Means for recording the measured pH values, which means after the titration with this acid is finished

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is, dnT-ch. Energy supply can be turned off to υΗ-v / erte! tonnes, which are greater than the change in the color pH-value of a Na ^ hweispstems with a predetermined energizing period, this means during the energizing period with a Motor connected, which ^{actuates a P 1} impulse for the supply of acid to the ϊ ^ ββθγ of the system "; as well as, va rnmittel, which are connected to these meseune-smittel can sound an alarm, in case of failure read lower, d: e lower than a predetermined one

jji e "jilT finding will now be made with specific reference to the Drawings described, v / orin

j? 'iff. 1 is a graphical plot of the pH scale on the ADscissa ⁱ ; ee; en the A "i tcalation on the ordinate for a particular Tjx) of water;

Ji'ig. 2 shows, in jjiagraph form, a device according to this invention represents for the elimination of generality; -

Fig. 3 is a gray-black plot showing the M alkalinity (on the ordinate) for the starting water and the tfasser des System, plotted against time (on the axis), for shows a cooling tower where an apparatus according to this invention has been used.

In i'ie :. . 1 is the value of the alkalinity M (on the ordinate) p; ez ^eri clen ^ H-vV'ert (abscissa) for a "certain type of water. This graph represents a theoretical example can be well applied to corresponding actual examples. In this graph, one can see the general trend that the alkalinity increases with increasing pH.

As mentioned above, the main problem was the automatic ones Regulation of the alkalinity M in the fact that one does not correctly was able to record the pH of the returned water. Pig. I shows the relationship that exists between pH and alkalinity M as ppm GaüO. ^ exists when the values of the alkalinity M an-

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increase, there is a similar increase in pH, but the increase in the value of the alkalinity M is much more pronounced.

In jiig, 2 a device for regulating the alkaline level M for evaporation systems is shown. Such a device contains a titration beaker 10 which is equipped with a stirrer 12 and with a lower inlet 14 and with an upper outlet 16. The outlet 16 can be in communication with the passersystem or can be drained into a sewer. The c'Rsser of the system to be analyzed is connected to α tau ^ iinla.ß 14. The flow of water to the inlet is regulated at predetermined intervals by a solenoid valve 18, which in turn is regulated by a programming unit 20. When the inlet 14 is closed, the liquid level in the cup 10 is determined by the position of the outlet 16, whereby a well-defined Volume of the liquid to be titrated is determined. A vial 22 with a plastic capillary tube 24 is filled with the titration acid contained in the reservoir 26 during the period in which a three-way solenoid valve 28, which is controlled by a timer unit 30, is closed. The acid in the vial 22 is disposed of in the analyzer 10 when the valve 28 is opened by means of the timer unit 30. A pH meter 32, with a measuring electrode 34 immersed in the liquid in the cup 10, is connected via a relay 36 to a pump unit 38 for charging the system with acid. The pump unit 38 is connected to a reservoir 40 of the acid and to a water system 42. The pH meter 32 is also connected to a warning device 46 ^{via a relay 44, which is controlled by the programming unit 20, 1} gives an alarm when the pH of the water gets too low, for example lower than 7 *

The timer 30 regulates the emptying of the vial 22 at regular intervals programmed intervals, more precisely, a few seconds after the cup 10 has been filled, the

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Contents of Ph j oils 2 ^ in aas Volvo>"isn contained in the cup 10 E drained ¹ IUanickelt and constant gerünrt by the Hübrer 12 wax a short period of time following moves a ln 'exanaeip;!.? E on the nil wJpter 32, which is connected to the measuring electrode 34 immersed in the liquid in the beaker, away from the minimum value which is marked on the scale of the pH meter. If -after the titration the pH is higher as the minimum value (pH 4.5. the IVr change point of the methyl orange), the itelais 36 is energized and remains energized for a predetermined period of a Z3rk: lus, for example 1 hour, whereby the operation of the acid in the -, The pump 38 entering the water system is regulated to a slow speed, about 1.5 to 2 times the flow speed, as is necessary to neutralize the alkalinity carried along by the build-up water into the water system. Various types of pH meters can be used. V Preferably, an optically detecting means is used to detect the change in color in the beaker 10 during the titration.

If, on the contrary, the pH is lower than this minimum (4.5) after the titration, the heat 36 is not energized and there is no supply of acid from the pump for the following hour. After the end of the titration period the inlet 14 of the cup 10 is reopened under the control of the solenoid valve 18 and the water from the Sj ⁷ stem 48 flows freely through the cup.

as above during the state of the free flow of , ifl <3ser through the cup 10 the index of the pH meter 32 one ! Pliess equilibrium state reached and below the maximum value, For example, if it is set to 7, it becomes a warning signal from device 46 connected to pH meter 32. - ...

IUs it should be noted that the evaporation systems usually one bigger. Have a dwell time of more than several hours; therefore, the device proposed above can operate at a frequency of 1 hour

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or even shorter than these times not the <?; e wish continuity of the Kontro! ! operating within the usual G-enfluip-iceitsgrem-.en, which appear to be acceptable to an industrial scale, influence.

The corresponding volumes of the cup of the vial depend of course on the limit of the AlVglinitat, which in the System is to be observed, as well as of the concentration of the titanic acid.

For example, if the alkalinity limit is 200 v, vm. the volume of the cup is 300 cm '. To neutralize the alkalinity, a consumption of 60 mg H ₀ SO is required.

3 necessary üs is necessary to play For a 30 cm -Phiöle with N / 25 acid or 15 C M'-vial with 12.5 Ή acid zn use.

Although it is obvious that large volumes of the cup and the vial increase the titration accuracy, it is also true that these large volumes have a larger one Acid consumption and accordingly a more frequent wax filling of the die Require xte reservoirs containing titanium ionic solution.

In the one with! Pig. 3 one can see three curves: Curve A represents the alkalinity M of the Build-up water, curve B the alkalinity H of the water in the water system and curve C (a straight line) the yeast limit value for the regulation of the alkalinity M. This granhik refers to a cooling tower whose characteristics as the following are:

Speed of the returned water 4500 g ρ m Flow velocity of the build-up water 130 g ρ m

Concentration ratio 1.5-3.0

Alkalinity M of the build-up water 200-325 ppm

(as OaCO-)

The invention is based on particular special embodiments

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- χι -

been special; it goes without saying, however, that Changes or modifications can be made without from the xtgjoinen of the present industrially advantageous to deviate.

Claims

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Claims (7)

Claims ilj Device for the automatic regulation and control of the alkalinity in the return water of evaporation systems, characterized by (a) Means provided with a kettle for collecting a "certain." Volume of the water of the system, which is in a continuously flowing test conduit. of the water; · (b) Means for opening and closing these collection means (a) at programmed regular intervals that run through Timers controlled by solenoid valve means; (c) Dosing and jßeschickmittel ζτμϊι titration on one average the predetermined acid value in these collections (a); (d) Means connected to these spin-melting means (a) for. Measure the pH of the water in the system to be analyzed; (e) Means for recording the measured pH values, which means after titration with this acid can be energized to greater pH values than in accordance with the change in the color pH value of a measuring system with a predetermined energization period, these means during the energization period are connected to a motor, which starts a pump for charging the \ ip.a ders of the system with acid and (f) remote means connected to these measuring means (d), which 5CI9819 / 10 52 sound an alarm if it occurs deeper nji-rferte that are lower than a predetermined minimum walked. 2. Device according to Anfmruoh 1, thereby that sneezing flow system iviethylor ^ ane with a pH banding of 4.5 accordingly. **>. Device according to claim 1 or 2, characterized in that this collecting means (a) contain a beaker (10) which is equipped with a stirrer (12) and on one side towards the bottom an inlet (14) for the water System, which is connected to the circuit for this I / Tsser outlet, which is regulated by a solenoid valve energized by means (b), and is provided in its upper part with an outlet (16) on the other side, which is in the beaker (10) at such a level that the titration volume is defined when the jüinlaß (14) is closed. 4. Device according to one of claims 1 to 3, dadurcn ffesigns that these means (c) for dosing d'er a vial (22) of a measured volume and with a plastic capillary tube connected to a reservoir (26) for the titration acid through a line, which is regulated by a So, lenoid valve (28), which is energized by a timer system (20, 30). 5. Device according to one of claims 1 to 4, characterized characterized in that the desired alkalinity M for, / water of the system within the interval of 30 to 100 ppm is set. 6. Device according to one of claims 1 to 4, characterized characterized in that the alkalinity desired for the water of the system is greater than 100 ppm. 7. Vorricntung according to one of claims 1 to 6, characterized in that the frequency of the titration cycle of the water of the system Less than the residence time in the evaporation * system is. I / r.Ro / La 509819/1052 BATH ORIGINAL