US3188289A - Inhibiting boiler deposits - Google Patents

Description

June 8, 1965 Filed Dec. 28, 1961 H. L. KAHLER ETAL INHIBITING BOILER DEBOSITS 4 Sheets-Sheet 1 ATTORNEYS.

June 8, 1965 KAHLER ETAL 3,188,289

INHIBITING BOILER DEPOSITS Filed D60. 28, 1961 4 Sheets-Sheet 3 SODIUM LIGNO SU LFONATE *6 C MC- SODIUM LIGNO SULFONATE DEPOSIT, Gms/Ft HIGH HEAT TRANSFER 0 I so I ga e I05 ORGANIC PPM flarzyLema )zfir ATTORNEYJ',

June 8, 1 H. 1.. KAHLER ETAL 3,188,289

INHIBITING BOILER DEPOSITS 4 Sheets-Sheet 4 Filed Dec. 28. 1961 zofiifiwmzw lo E 3 w; 3 N 3 m6 000 02 mmtwzfiz. CE: :9: 0 8

ATTORN EYS United States Patent 3,183,289 nuuerrmn DEWQSETS Harry Lewis Kahler, Feasterville, and Ray T. Zea-by,

The present invention relates to processes and compositions for preventing or reducing the deposits which otherwise will form in steam generating systems such as steam boilers, evaporators, economizers, and the like.

The invention more particularly relates to the reduction or prevention of deposits in steam generating systems by introducing additives into the feed water which supplies the steam generating system, or directly into the steam generating device itself. The invention is particularly concerned with the introduction of the sodium salt of carboxymethylcellulose either alone or with other materials.

In the drawings, FIGURE 1 is a diagrammatic illustration of a testing boiler used in the experiments according to the invention.

FIGURES 2, 3 and 4 are curves plotting deposit in grams per square foot as an ordinate, against organic additive in parts per million as the abscissa in FIGURES 2 and 3 and against degree of substitution as the abscissa in FIGURE 4.

It is well known in the art that organic materials such as tannins, lignins and starches will prevent or reduce boiler deposits and modify the condition of boiler sludges so that they can be more conveniently eliminated by blowdown.

We have discovered that the sodium salt of carboxymethylcellulose has remarkable properties in reducing or preventing boiler deposits on heat transfer surfaces and conditioning boiler sludges for proper removal from the boiler by blowdown.

The sodium salt of carboxymethylcellulose is derived from cellulose by solubilizing the cellulose to obtain a structure symbolized by ROCH COONa, where R represents the cellulose structure. Each anhydroglucose unit (C H O in the cellulose structure contains three active hydroXyl groups to which carboxymethyl groups can be attached. It is the sodium salts of carboxymethyl groups which make the cellulose gum water soluble. The material is described in Hercules Cellulose Gum (1956), Form 835.

Carboxymethylcellulose is usually used as a sodium salt, although other Water soluble salts may be used, of which the potassium salt, the ammonium salt, and the calcium salt are typical. The sodium salt of carboxymethylcellulose is for convenience abbreviated in the tables as CMC, a Hercules registered trademark.

We have also discovered that the sodium salt of carboxymethylcellulose when combined with an organic material of the class consisting of tannin, lignin, sult'onated lignin and thiolignin acts cooperatively to further reduce or prevent boiler deposits and to improve the conditioning of the sludge, having an additive effect when the sodium salt of carboxymethylcellulose and the organic material are used together.

We have also discovered that the power of the sodium salt of carboxymethylcellulose to prevent boiler deposits is a function of the degree of substitution. The degree of substitution may be defined as the number of available hydroxyl groups per anhydroglucose group which have combined with carboxymethyl groups. In cellulose each anhydroglucose group has three hydroxyl groups which can be replaced, so that the theoretical maximum substitution is 3, and theoretically the substitution can vary Patented lune 8, 1965 from O to 3. Practically, however, the substitution varies between 0.2 and 3.0 and preferably varies between 0.4 and 2.0. For high heat transfer, a substitution of about 0.7 is most eifective in reducing or preventing boiler deposits; V

We have also discovered that the power of the sodium salt of carboxymethylcellulose to preventor reduce boiler deposits is a function of the length of the polymer chain,

which is the number (x) of anhydroglucose units 'in the molecule when the formula is written (C H 0 Polymer length has a very powerful effect on viscosity on the sodium salt of carboxymethylcellulose, the smaller chain lengths giving lower viscosity and the longer chain lengths giving higher viscosity, the viscosity varying between the limits of 15 to 40,000 centipoises for a 2% by weight solution of the water soluble salt in water.

We have determined that the sodium salt of carboxymethylcellulose is stable at high temperatures, and high pressures and on high heat transfer surfaces of steam generating systems.

The slowly swelling and viscous sodium salt of carboxymethylcellulose can be fed into steam generating systems either as paste or in solid powder form.

The sodium salt of carboxymethylcellulose and the combination of the sodium salt of carboxymethylcellulose and organic materials such as the tannins perform well with boiler antifoams of the character well known in the art such as the polyamides which are condensates of amines and acids of varying length and configuration. A simple example of this type is ethylene diamine acylated by 4 moles of a fatty acid having a carbon chain length above 10, such as oleic acid.

Another type of antifoam in general use today is the ether type made by treating glycols at superatmospheric pressures. The general resulting compounds can be expressed by H(OC H OH.

A third type is a modification of the second type but distinct from it. This type, well known in the art, results from interacting step-wise mixtures of ethylene glycols with propylene glycols to give a series of products represented by (HO(C H (C H (C H I-I.

The sodium salt of carboxymethylcellulose and the combinations thereof with organic material such as tannins, lignins, and the like, have been specifically applied to reduce or eliminate the boiler deposits caused by phosphates, hydroxy phosphates, hydroxides, and silicates which would otherwise cause incrustation of the character commonly encountered in boilers due to raw water or feed water.

The researches were carried out in two experimental boilers. The testing for boiler dispersing power and deposit prevention, stability of organic materials and the quality of the steam was carried out in two boilers of the character diagrammatically illustrated in FIGURE 1. One of these two boilers had been used in tests of this character for 12 years and the other for 9 years and the test results have been found to coordinate well with plant operation.

The boiler 20 has a high heat transfer surface 21 and a low heat transfer surface 22 due to electric heaters. Blowdown is accomplished through a blowdown line 23. The high heat transfer surface 21 transfers 180,000 B.t.u. per square foot per hour, and the low heat transfer surface 22 transfers 28,000 Btu. per square foot per hour. In the later parts of the specification and the tables when high and low heat transfer surfaces are referred to, this is what is meant.

The heaters supply the heat to run the boiler at 300 p.s.i. and 420 F. unless otherwise indicated, and they also provide the heat transfer surfaces on which the boiler dis persive power is evaluated. The boiler has a steam leg 24.

The compartment to the left connected both through the steam and the boiler water phases is a water level control for controlling the water level in the boiler. Each experiment was run two days unless otherwise stated.

At the end of each experiment the electrical heaters 21 It will be evident from Table 1 that there are differences in the power of the sodium salt of canboxy methylcellulose depending on this degree of substitution, the 7 series being the most powerful and giving a reduction on total and 22 were removed and the deposits thereon were eX- deposit of the-order of 70 to 80%. amined critically. Similar results are obtained for other water soluble The boiler operates on a synthetic feed water as later salts of carboxymethylcell-ulose. described by which boiler encrustants and organic treat- 'It should the noted, however, th t i 11 f the grades of ments are introduced into the boiler as needed. A conthe sodium salt of .carboxymethylcellulose had the power tinuous blowdown system operates the boiler at 15 cycles to reduce or eliminate :boiler deposits and all had sludge of concentration. The sight glass 25 above the water line conditioning properties as indicated by the turbidity of is used for the detection of foaming of the boiler water. A th bl wdown of the boiler water. Whereas in expericontimwus recording Sodium spectrophotometer ments without the sodium salt of 'carboxyme'thylcellulose Shown) is St/d On each experiment to record y Steam there was very low turbidity, the sodium salt of eanboxycontamination above normal. methylcellulose increased the turbidity 'from 2 to 11 told.

Feed and treatmen W t r ar Obtained from a tank 25 The increase in turbidity is important as it means that through a feed Watfil' P p 7 to the boiler. the sludges are properly conditioned and dispersed so that SODIUM SALT OF CARBOXYMETHYLCELLULOSE they can be effectively el minated by boiler blowdown.

FOR REDUCING BOILER DEPOSITS AND CON The illlbldlty 0f the b01181 b'lOWdO VE/H 111 111658 expen- DITIONING BOILER SLUDGES ments seems to the somewhat proportional to the boiler power of the sodium salt of carboxymethylcel'lulose in Table 1 shows a first series of experiments in which relation Preventing deposits the sodlum Salt of carboxymetllylcellflose was used The concentration of the water soluble sodium salt of forms at P 10 Parts P carboxymethylcellulose in the water of the steam generatand Compared with test 1'unS W1thutLthe Sodium Salt ing equipment should be mtaintained at a level up to 100 of carboxymethylcellulose. It W111 be noted1 that in every ppm the concentration being effective at an Timex The case Where the sodmm .Salt of carboxymethycenulfsa s question of what concentration is effective depends upon Presentthe tota1dep1tWaS much 1653 ii l an the scaling load, and on some scaling loads 3 ppm. low heat transfer surfaces and the borer tur ldity ran or 5 ffac i much higher.

It will be noted that the effect of the sodium salt of COMBINATION OF THE SODIUM SALT OF carboxymethylcellulose is almost as impressive on the CARBOXYMETHYLOELLULOSE AND ORGANIC high heat transfer surface as on the low heat transfer TREATMENT SUCH AS TANNIN surface.

The numbers following the CMC indicate the degree of In eXPenmentS Water Soluble 4 Salts of carsubstitution of the sodium salt of carboxymethylcellulose bPxymethylceuulosea was found that the as later explained, and the letters following these num- F Salts ofcflnboxymthylwllulose gave add1t{ve Power bets have the following meaning: in total deposit reduction and sludge dispersion when used with other organic materials such as tannin, lignin, 4O sulfonated ligriin and thiolignin. Experiments on this g g subject are reported in Tables 2 and 3. mm VKSCOSIPY Table 2 shows that a small amount of the sodium salt cry Ylscoslty of carboxymethylcellulose used with a modified treatment Y as described in the footnote gave additional reduction in 1g vlscimty. deposit compared with the modified tannin treatment SM0re readily dissolved A5 alone Table 1 Table 2 BOILER EXPERIMENTS WITH CMC BOILER EXPERIMENTS, CMC+ORGANIC Total Deposit, Boiler Water, Total Deposit, Girls/it. ppm. 50 Gms/itfi Turbidity Exp. N 0. Treatment in Boiler Exp. Treatment in ppm. in p.p.m.

Water, p.p.m. Low High Tur- No. Low High SiOz Heat Heat bidity CMC Heat; Heat Trans- Transas Trans- Transicr fer 810; for fer No organic 1.20 5.20 9 No CMC- O 8 11 0 }30 Modified Tannins 1 0. 48 1. 16 76 10 one 4M 1. 04 a. 9 25 10 7.5 CMC 7HS22.5 Modified 0.15 0.48 160 10 CMC 7AT 0. 23 0.27 119 10 Tannins. 10 CMC 7LT o. 31 0. ss 94 1o 67 7.5 CM O TBS-22.5 Chestnut 0.18 0. 49 04 6O Tannin.

V 1 Modified Tannins as a combination of Quebraclio, Chestnut, Wattle w CMC 33 42 so 10 ii pg g i sftgwvc tannins secured as an extract from the leather tanning Conditions: No. 3 Boiler, 300 psi, 15 cycles of concentration, 3 day H testing. with a feed water of S p.p.m. Ca, 3 ppm. Mg (as CaC0 and (1:) sulhcient alkalinity, sultite and silica fed to give boiler water balances of 600 p.p.m. P alkalinity, 700 p.p.rn. M alkalinity (both as 02100:) and residuals of 20 to each of phosphate. sulllte and silica. in CMC 9H 0.41 1.0 81 1o The turbidity obtained from the combination treatment CMC 12H& M 72 51 10 was over twice as great as that obtained from the modi- 7 fied tannin alone :and this indicates that the sludge condi- 1 All 7 grades in these experiments.

Conditions: Experimental Boiler No. 2, 300 p.s.i., 15 cycles of concentration using a feed water 01'18 p.p.m.-Ca, 9 p.p.m. Mg (both as CaCO3) with sutficient alkalinity, phosphate, sulfitc and silica to provide a boiler water having 405 ppm. suspended solids, 400 ppm. P alkalinity (as CflCOs) and residuals of sullitc, phosphate and silica each in the 25 to 80 p.p.m. zone. 2 days test.

tioning :was also better.

Run 67 shows that the same 30 p.p.m. level of treatment using the sodium salt of car boxymethylcellulose plus chestnut tannin was also good in 'lowering total deposit but gave less turbidity than the combination of the #3 sodium salt of carboxymethylcel-lulose with the modified tannins. It will be noted that the modified tannins when used with the sodium salt of carboxymethylcellulose gave an 88% decrease in deposit on the low heat transfer area and gave a 90% decrease in deposit on the high heat transfer area. The turbidity increase was 18 fold over the result when no organic additive was used and the tunbidity was double as compared to the test when modified tannins alone were vused.

Table 3 and FIGURES 2 and 3 show the results from feeding sodium lignosulfonate in various concentrations as compared with sodium carboxymethyl'cellulose and a combination of sodium carboxymethylcellulose and sodium lignosulfonate. 'It will be noted that the combination lowers the total deposit as compared with sodium lignosulfonate alone. The'turbidity obtained, however, was only comparable with that of sodium lignosulfonate alone. The curves for sodium carboxymethylcellulose in IGURES 2 and 3 show how powerful this treatment is even at very low concentrations.

Table 3 BOILER EXPERIMENTS, CMC-l-ORGANIO Total Deposit, Gms/ft.

Av. Tur- Exp. Boiler Water Treatment, ppm. bidity as No. Low High ppm. SiOi Heat Heat Trans- Transfer fer }No organic 2. 4 7. 2 10 Sodium Liguo Sulfonate 2. 6 5. 7 10 30 Sodium Ligno Sulfonatc 0.7 1. 4 38 96 Sodium Ligno Sullonate 0.15 0.17 93 5 CMC 7H5 0.52 1.51 56 10 CMO 7HS 0. 30 0. 29 133 30 OMC 7H8 0. 09 l]. 08 266 }5 CMC 7HS-25 Sodium Ligno 0. 51 0.78 35 Sulfonate.

Conditions: No. 2 Boiler, 300 p.s.i., 2 day experiments with a. feed water of 18 p.p.m. Ca and 9 p.p.rn. Mg (both as CaOOa) and with sufiicicnt added inorganics to give boiler balances at cycles of concentration of 400 p.p.m. P alkalinity, 500 ppm. M alkalinity and -80 p.p.rn. each of phosphate, sulfitc and silica.

EFFECT OF DEGREE OF SUBSTITUTION ON THE POWER OF THE SODTUM SALT OF CARBOXY- METHYLCELLULOSE Using the same boiler as shown in FIGURE 1, and i boiler conditions of 15 cycles of concentration, 400 ppm. P alkalinity, and residuals of sulfite, silica and phosphate each in the zone of to 80 p.p.rn., FIGURE 4 shows the effect of the degree of substitution on the total deposit from 10 ppm. of sodium carboxyrnethylcellulose in the boiler water. It will be evident that the best results for high heat transfer, that is, the lowest deposit, were obtained when the degree of substitution was 0.7. The results obtained when the degree of substitution was 0.9 were reasonably close, with double the deposit, while the results obtained with substitutions of 0.4, 1.2 and 2.0 were considerably inferior.

With the low heat transfer unit, the degree of substitution was far less important as a factor, and sodium carboxymethylcelluloses with degrees of substitution of 0.7, 0.9, 1.2 and 2.0 gave values in the same range and sodium carboxymethylcellulose with a degree of substitution of 0.4 gave results which were reasonably close. These experiments on degrees of substitution were conducted for various polymer lengths from small to large, that is, from 500 to 2000 anhydroglucose units, and with viscosities in 1% water solutionsvarying from 100 to 20,000 centipoises, as it is not possible at this time to obtain products with constant polymer lengths in the various substitution experiments. The practice in num- EFFECT OF LENGTH OF POLYMER ON THE EF- PECTTVENESS OF THE SODIUM SALT OF CAR- BOXYMETHYLCELLULOSE The same boiler conditions which were used to determine tle efiect of substitution were also used in this study. The tests were carried out with a constant subsitution or" 0.7. Results are presented in Table 4. At a feed of 5 ppm, the polymer length as evidenced by viscosity seems to be directly related to effectiveness in low heat transfer, the lowest deposit being obtained with lower polymer lengths and increased deposits being obtained with longer polymer lengths. At high heat transfer, the effect of polymer length is more powerful at intermediate polymer lengths and less powerful at the extremities.

With a feed of 10 ppm. in the boiler water, polyme length had no apparent eliect on deposit formation, all polymer lengths giving satisfactory deposit reduction to about the same degree. It is understood that Type 7L has 500 to 1000 cellulose units, Type 7M has 1000 to 1500 cellulose units, and Type 7H has 1500 to 2000 cellulose units. Type 7A is believed to have a polymerization of the same order as Type 7L. The same degree of polymerization can be obtained in Series 4, Series 9 and Series 12. The size of these cellulose units indicates that in most cases there are extremely large polymers with extremely high molecular weights.

T able 4 EFFECT OF POLYMER LENGTH AT SUBSTITUTION 0.7

Deposit, GmJft. 0M0, Viscosity, Exp. No. ppm. Log of Trade in Sol. 25 C Viscosity Low High Designation Boiler Heat Heat Water Trans- Transfer fer 14 1. 146 0. 3t 3. 07 CMC 7AP 36 1. 556 0. 48 1. 25 CMO 7LP 450 2. 653 1.13 1. 33 0M0 7MP 40, 000 4. 602 1.99 3.14 OMC-7HP 14 1.146 0.32 0. 33 CMC 7A1 36 1. 556 0. 35 0. 32 OMC 7LP 450 2. 653 0.33 0. 42 0M0 7MP 40, 000 4. 602 0.28 0.21 CMC 7HP Conditions: Experimental Boiler No. 2, 300 p.s.i., 15 cycles of concentration, with a feed water of 18 ppm. Ca, 9 p.p.m. Mg (both as CaCOs) and sufiicient alkalinity, phosphate, silica and sulfite to give boiler water balances of 400 ppm. P alkalinity (as OaC O and residuals of phosphate, silica and sullite each in the 20-90 ppm. zone.

EFFECTS OF HEAT TRANSFER, TEMPERATURE AND PRESSURE ON EFFECTIVENESS OF THE SODIUM SALT oF CARBOXYMETHYLCELLU- LOSE No difiiculties have been encountered in employing water soluble salts of carboxymethylcellulose in the form of viscous solutions with or without other organic materials. The sodium salt of carboxymethylcellulose can be preswelled in water with constant'stirring to provide a viscous clear product which can then be treated with other inorganic chemicals and wtih organic chemicals such as tannin, lignin, sulfonated lignin or thiolignin. The products can be diluted at the time of use in the plants and offer very satisfactory feed solutions for introducing the materials into the boiler system. The additives will be suitably Water soluble phosphates such as sodium tripolyphosphate, sodium hexametaphosphate, disodium hy drogen phosphate, monosodium dihydrogen phosphate and similar water soluble poly and ortho phosphates; water soluble hydroxides such as sodium hydroxide and potassium hydroxide; water soluble silicates, such as Metso anhydrous silicate (Na SiO and other simple water soluble metasilicates and orthosilicates; water soluble carbonates such as sodium carbonate, sodium bicarbonate; and water soluble sulfites such a sodium sulfite and sodium acid sulfite which act as oxygen scavengers so that the boiler operates in an oxygen-free system or very close to it. Other oxygen scavengers such as hydrazine can also be employed. The organic material such as tannins, lignins, sulfonated lignins and thiolignins are also additives. The antifoams as mentioned herein are also suitable additives.

Powdered products containing powdered sodium carboxymethylcellulose or sodium carboxymethylcellulose in powdered form with other powdered organic material as mentioned above are not as easy to handle in plant preparation of feed solutions as are the pastes, but they can be used satisfactorily if desired.

EFFECTIVENESS OF THE SODIUM SALT OF CAR- BOXYMETHYLCELLULOSE AND THE SODIUM SALT OF CARBOXYMETHYLCELLULOSE PLUS OTHER ORGANIC MATERIALS ON BOILER WA- TER FOAMING AND STEAM PURITY 'ble sodium salt of carboxymethylcellulose in the effective concentration zone and with other organic materials such as lignin, tannin, sulfonated lignin and thiolignin gave excellent quality of steam.

The limit of other organics such as tannins and lignins may be as high as 500 ppm. under extraordinary circumstances, and most desirably 200 ppm. for moderate loads, there being an effective concentration present in the boiler at all times, which for example on a light load might be ppm.

EFFECT OF THE SODIUM SALT OF CARBOXY- METHYLCELLULOSE PLUS OTHER ORGANIC MATERIALS ON REDUCING DEPOSITS OF CAL- CIUM PHOSPHATE, MAGNESIUM HYDROXIDE AND MAGNESIUM SILICATES In boilers which are operated with suflicient water soluble phosphates such as any one of the sodium orthophosphates, orthophosphoric acid,,or any one of the sodium molecularly dehydrated phosphates or any of the corresponding phosphates of potassium (and sufiicient alkalinity to insure precipitation), calcium is usually precipitated as tricalcium phosphate. Under special conditions of alkalinity, the precipitate may be one of the apatites xCa (PO .yCa(OH) where x and vary depending on conditions. Under these same conditions, magnesium is precipitated as the hydroxide and as one of the silicates such as serpentine (3MgO.2SiO .2i-I O). If the feed water contains small amounts of iron, alumi- $3 num, copper, etc., many other compounds may be formed but these are likely to be in trace amounts. Boiler water sludges and deposits predominately contain tricalcium phosphates with the possibility of some calcium hydroxy phosphate, and magnesium as the hydroxides and silicates.

Without going into all of the complexities of boiler water chemistry, reference is made to Table 5 which shows the behavior of sodium carboxymethylcellulose and sodium carboxymethylcellulose with organic materials in reducing the boiler precipitates or sludges which otherwise would adhere :on heat transfer surfaces, as well as conditioning the sludges so that they are Welldispersed for blowdown from the boiler. It there is shown that '10 ppm. of sodium carboxymethylcellulose in the Type 7HSP form reduced tricalcium phosphate expressed in terms of calcium by on the low heat transfer surface and on the high heat transfer surface. This same treatment reduced the mag esium by 82% on the low heat transfer surface and 77% on the high heat transfer surface. A similar advantageous reduction was obtained in the calcium and magnesium deposits on the low and high heat transfer surfaces by the combination treatment of the sodium salt of carboxymethylcellulose and sodium lignosulfonate.

Table 6 shows that under different testing conditions a combination of sodium carboxymethylcellulose and modified tannin treatment reduced the calcium and magnesium deposit on both high and low heat transfer surfaces.

1 Occurred as Caa(P0i)2 predominately.

2 Occurred as a combination of Mg(OH): and 3MgO.2SiO predominately.

Conditions: Boiler 2, 300 psi, 15 cycles of concentration low heat transfer heater of 28,000 B.t.u. per ft. per hr., high heat transfer of 180,000 B.t.u. per ft. per hr., 2 day tests. Feed water had 18 ppm. Ca and 9 p.p.m. Mg (both as CaCOs), and suthcient alkalinity, sulfitc, phosphate and silica to give boiler water balances of 400 p.p.m. P alkalinity and 30-80 ppm. residual each of S03, P04 and lSiOz.

Table 6 Low Heat High Heat Transfer, Transfer, Exp Boiler Water treatment, Guns/it). Gms/it.

No. ppm.

Ca Mg Ca Mg 71 No Organic 0. 44 0. 11 2.11 0. 26 60 7.5 CMC 7HSP-22.5 Modi- 0.05 0. 02 0.12 0.08

fied Tannin gccurret as gamggah pridomiiately. V

ccurre as g i an 3M .2Si0 rcdominatel see p nniti n i; gable 2. g 2 p y on i ions: 0 oiler, 300 p.s.i., 15 cycles, 3 da testin low heat transfer scaling heater 28,000 B.t.u. per it? per hr., high h at transfer scaling heater 180,000 B.t.u. per it. per hr. with a feed water containing 8 ppm Ca, 3 p.p.m. lvig (both as Capos) and a sufficient alkalinity, sulfite, phosphate and silica to g ve boiler water balances of 600 ppm. P alkalinity and 30-90 p.p.m. residuals each of phosphate, silica and sulfite.

All of these experiments used excess phosphate and acceptable alkalinity levels to keep the pH above 10.5 and preferably in the range from 11.0 to 11.5 but the invention is not limited thereto. They produce carbonates and sulfates in which the carbonates and sulfates are in trace amounts only as the carbonates and sulfates are too soluble to precipitate, and the precipitates being predominantly phosphates, hydroxides and silicates.

The other water soluble salts of carboxymethylcellulose behave the same as the sodium salt.

In view of our invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of our invention without copying the process and composition shown, and we, therefore, claim all such insofar as they fall within the reasonable spirit and scope of our claims.

Having thus described ouriuvention what we claim as new and desire to secure by Letters Patent is:

1. A process of reducing phosphate, hydroxide and silicate deposits in steam generating equipment having Water containing alkalinity, phosphate, silicate, an oxygen scavenger and antifoam, which comprises introducing into the water of the steam generating equipment between and 100 ppm. of a sodium salt of carboxymethylcellulose having a substitution of carboxymethyl groups within the range from 0.7 to 0.9, inclusive, having a polymer length of between 500 and 2000 anhydroglucose units and having a viscosity in a 2% water solution of between and 40,000 centipoises.

2. A process of claim 1, which comprises introducing a sodium salt of carboxymethylcellulose having a substitution of carboxymethyl groups of 0.7.

3. A process of claim 1, which comprises introducing the sodium salt of carboxymethylcellulose as a powder, in combination with (1) a material of the class consisting of a water soluble phosphate, a water soluble hydroxide, a water soluble carbonate, a water soluble sulfite, and a water soluble silicate, (2) an antifoam, and (3) an organic material of the class consisting of tannin, lignin, sulfonated lignin and thiolignin, said powder facilitating the feeding of the sodium salt of carboxymethylcellulose.

4. A process of reducing phosphate, hydroxide and silicate deposits in steam generating equipment having water containing alkalinity, phosphate, silicate, an oxygen scavenger and antifoam, which comprises introducing into the water of the steam generating equipment between 5 and 100 p.p.m. of a sodium salt of carboxymethylcellulose having a substitution of carboxymethyl groups within the range from 0.7 to 0.9, inclusive, having a polymer length of between 500 and 2000 anhydroglucose units and having a viscosity in a 2% water solution of between 15 and 40,000 centipoises and also introducing into the steam generating equipment an organic material 10 of the class consisting of tannin, lignin, sulfonated lignin and thiolignin, and maintaining a concentration of said organic material in the steam generating equipment which is effective at all times and up to 500 ppm.

5. A process water in a steam generating equipment containing from 5 to 100 ppm. of a sodium salt of carboxymethylcellulose, said carboxymethylcellulose having a substitution of carboxymethyl groups within the range from 0.7 to 0.9, inclusive, having a polymer length of between 500 and 2000 anhydroglucose'units and having a viscosity in 2% water solution between 15 and 40,000 centipoises, and said process water also containing alkalinity, phosphate, silicate, an oxygen scavenger and antifoam.

6. A process water in a steam generating equipment containing from 5 to 100 p.p.m. of a sodium salt of carboxymethylcellulose, said carboxymethylcellulose having a substitution of carboxymethyl groups within the range from 0.7 to 0.9, inclusive, having a polymer length of between 500 and 2000 anhydroglucose units and having a viscosity in 2% water solution between 15 and 40,000 centipoises, and said process water also containing an efiective amount and up to 500 p.p.m. of an organic material of a class consisting of tannin, lignin, sulfonated lignin and thiolignin, and the said process water also containing alkalinity, phosphate, silicate, an oxygen scavenger an antifoam.

References Cited by the Examiner UNITED STATES PATENTS 2,727,867 12/55 Denman et a1. 2,783,200 2/57 Crum et a1. 210-56 X OTHER REFERENCES Nieuwenhuis: Improvement of the Dirt suspending Power of CMC, I. Polymer Sci., 12, 237-52 (1954).

Betz: Handbook of Industrial Water Conditioning, Betz Laboratories, Inc., Phila. 24, Pa., 5th ed., 1957, pp. -99, -112.

Sodium Carboxymethylcellulose, a publication of the Hercules Powder Co., Wilmington, Del, 1944, 4 pp.

Hercules Cellulose Gum (CMC), pub. of Hercules Powder Co., 1951, 20 pp.

Hercules Cellulose Gum (CMC), pub. of Hercules Powder Co., 1949, 11 pp.

MORRIS 0. WOLK, Primary Examiner.

Claims (1)

1. A PROCESS OF REDUCING PHOSPHATE, HYDROXIDE AND SILICATE DEPOSITS IN STEAM GENERATING EQUIPMENT HAVING WATER CONTAINING ALKALINITY, PHOSPHATE, SILICATE, AN OXYGEN SCAVENGER AND ANTIFOAM, WHICH COMPRISES INTRODUCING INTO THE WATER OF THE STEAM GENERATING EQUIPMENT BETWEEN 5 AND 100 P.P.M. OF A SODIUM SALT OF CARBOXYMETHYLCELLULOSE HAVING A STUSTITUTION OF CARBOXYMETHYL GROUPS WITHIN THE RANGE FROM 0.7 TO 0.9, INCLUSIVE, HAVING A POLYMER

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