CA1208421A - Process for reducing drag in flowing aqueous media - Google Patents

Abstract

Abstract of the disclosure:

A process for reducing the drag of aqueous media in turbulent or pulsating flow, by adding to the aqueous medium a compound of the formula R1-K?A?
in which K denotes a group of the formula or , R2 denotes C1-C3-alkyl, preferably methyl, A denotes an anion of the following formulae Hal denotes fluorine, chlorine, bromine or iodine, R3 denotes C7-C10-alkyl or C7-C10-alkenyl and if A =
thiocyanate, R1 denotes C16-C26-alkyl or C16-C26-alkenyl, if A = p-toluenesulfonate, R1 denotes C12-C26-alkyl or C12-C26-alkenyl, and if A has one of the remanning meanings R1 denotes C16-alkyl or C16-alkenyl.

Description

~2089~2~

It ;s a generally known fact that flu;ds ;n turbu-lent flow experience drag at the walls conta;ning them.
It is also known that this drag can be reduced by ad~ing small amounts of certain substances. Substances wh;ch have th;s effect are referred to as dra~~reducing agen-ts.
A drag-reducing agent is a substance which, added ;n a small amount to a liqu;d in turbulent or pulsating flow, enables this liquid - under otherwise identical condi-tions ~ to flow fasterr Drag-reduciny agents have the effect that a given pump can deliver more l;quid through a g;ven pipe.
In many cases this fact alone represents a tech~
.
n;cal benefit, for example when a p;pe is used to full capac;ty in normal operation and peak demand would have to be delivered at certain t;mes. Since a given pump per-~ormance can deliver more liquid when drag-reduc;ng agents are used, the associated saving in energy will also, in many cases~ produce a techn;cal benef;t. F;nally, ;f there is no wish to increase the flow rate, th~ use of drag-reducing agents makes it possible to reduce pressure loss or to use pipes which have a smaller cross-section.
Both possibilities are measures wh;ch can improve the econom;cs o~ operating a pipe.
Drag-reduc;ng agents d;sclosed for water or aqueous solut;ons are not onLy high molecular ~eiyht compounds, such flS polyethylene oxide or polyacrylamide,. but also solut;ons of some surfactants. Additions of high molecu-12~18~2~

- 3 ~
lar we;ght compounds have, however, onLy a lim;ted prac-t;cal use as drag-reduc;ng agents, since, ;n regions of high sheer and stress~ such as~ for example~ ;n pumps or~
to a minor extent, in the turbulent boundary layer adja-cent to the walls of a pipe, they are mechanically degra-ded and suffer an ;rreversible loss ;n the;r effectiveness as dra~-reducing agents. High molecular weight add;t;ves are therefore unsu;table for closed water circulation sys-tems, where the same aqueous solut;on is constantly pumped round a system of p;pes, s;nce the ;rreversible mechan;cal degradat;on necessitates cont;nual replen;shment w;th effect;ve high molecular we;ght substance.
As is knownf add;t;ons of surfactants ~o vater do not suffer from the disadvantage of irreversible mechani-cal degradat;on ~U~S. Patent 3,g61,639~ It ;s true thathere too there ;s some mechan;cal degradat;on ;n regions of very h;gh sheer and stress~ such as, for example, in pumps, but ;t ;s completely revers;ble as soon as the solution has passed through these reg;ons. For ;nstance, Sav;ns has descr;bed the drag-reduc;ng effect of an aqueous solution of Na oleate on addition of KCl + KOH or NaCl+NaOH
(Rheol. Acta 6, 323 (1967D. Asslanov et al~ (Izv. Akad. Nank.
SSSR, Mekh. Zh;dk. Gaza 1,36-43 t1980~ stud;ed inter alia, aqueous solutions of Na laurate, myristate, palmitate and steara~e a~ pH 11 for drag-reducing purposes.
Chang et al. (U.S. Patent 3,961,639) describe the drag-reducing effect of aqueous solutions of some nonionic surfactants containing foreign electrolyte, at tempera-tures near the cloud po;nt.

. . - , ~ , : . ~

120~34;~ 1 ~ 4 --Sign;ficant disadvantages of the surfactant solu~
tions ment;oned are the;r relat;vely h;gh use concentra-t;ons, of at least 0.25% by weight, the formation of in-soluble soaps with Ca2+ and other cations, the forma~
tion of two phases ~Ihich separate on prolonyed standing and can lead to blockages, the need to add corros;on-promoting foreign electrolytes, and a very narrow tempera-ture range~ of a few degree Centigrade over which the drag-releasing effect occurs. Aqueous solutions of some cat;on surfactants, such as, for example, cetylpyr;dinium brom;de (Inzh. F;zh. Zh. 38, No. 6, 1031-1037 ~1980)) or cetyl trimethylammonium brom;de (Nature 21~~ 585-586 (1967)), each ;n a 1:1 molar mixture with ~ -naphthol, are free of these disadvantages~ but they have the crucial d;sadvan-tage, in addition to ~he fact that ~ -naphthol is spar-;ngly waterosoluble, that such m;xtures lose the;r effec-tiveness as drag-reducing agents with;n a few days, as a result of chemical degradation (U.S. Patent 3,~61,6~9, Conference Proceed;ng: Intern. Conference on Dra~ Reduc tion, ~.-6th September 1974, Rolla Missour;, U.S~A.).
We have now found, surprisingly, that, unl;ke any ex;sting surfactant disclosed for use as a drag reducing agent, the compounds listed below are effective drag-reducing agents ~Jhen used ;n the pure state ;n aqueous solutions even in very low concentrat;ons and without any add;tive whatsoever.
The invention accordingly relates to a process for reduc;ng the drag of aqueous med;a ;n turbulent or pulsatiny flow~ wh;ch compr;ses add;ng to the aqueous .

~ 0~342~
~ 5 --medium a compound of the formula R 1 -K~A~3 ;n which K denotes a group of the formula ~N ~ or - N(R2)3, , R2 denotes C1-C3-alkyl, preferabLymethyl, A denotes an an;on of the follow;ng formulae COO ~
COO ~

O~ , al , R3-CQ0~ , SCN~ , CH ~ -S03~

Hal denotes fluor;ne, chlorine~ bro~ine or ;od;ne, R3 deno~es C7-C10-alkyl or C7-C10-alkenyl and ;f A ~ thio-cyanate~ R1 denotes C1~-C26-alkyl or C16 C26 alkenyl~
;f A = p~toluenesulfonate, R1 denotes C12-C2~-alkyl or C12-C26-alkenyl, and if A has one of the rema;n;ng meanings R1 denotes C1~alkyl or C16-alkenyl.
The surfactant salts of the follow;ng cat;ons and an;ons are part;cularly preferred:

. ~
fC16~33NtCH3)~ ~ or ~ 16H33 COO~ ~~~, COO~
w.ith the an;on ~ or ~0~ Hal = Cl., Br,~

or xH2x~ 1 C fo-r 7~ x lO

~ ~nH2n~lN(CH3) ~ ~ H2n+1 N ~ ~

a) with the ar-ion 3 ~ S0'3~ for 12 - n ~ 26 . b) with the anion SCN~ for 16 ~ n - 26 ~25)~342~L

The salts mentioned are suitable for reducing the drag of aqueous media. They are added in concentrations of 0.01 to 2, preferably 0~06 to 0.6% by weight, but each salt has a d;fferent lower cr;t;cal concentrat;on l;m;t for adequate effectiveness as a drag-reducing agent. The drag-reducing effect also depends on the temperature.
Depending on the salt used, an adequate drag-reducing effect is found ~lithin the temperature range from 0C to 100C and above 100C. The lower temperature l;mit for use as a drag-reducing agent is for all surfactants the solubility temperature. However, if the surfactant is ;n solut;on, the operat;ng temperature can be below the solub;l;ty temperature by S - 30~C for some hours to weeks.

.
For n-hexadecyltrimethylammonium sal;cylate (CTA-Sal), adequate drag-reducing act;v;ty is obta;ned ~ith concentrations of 0.01 to 2% by wei~ht~ preferably 0.05 to Q.SX by we;ght, w;th;n the temperature range from ~5 to 70C~ At the same concentrat;ons as the sal;cylates~
the halogenobenzoates have a drag-reducing activ;ty within the temperature range from 35 to 65C. For pyridinium compounds the preferred temperature range is about 8 to 12 lower than that of trirnethylammonium salts. For the purposes of the invention, halogenobenzoates are the fluorine, chlorine, bromine and iodine derivatives, and they are preferably chlorobenzoic and bromobenzoic acid.
The surfactant salts of the formula shown above have been extens;vely described ;n the literature~ for example, in Journal of Coloid and Interface Science Vol. 75, Page 575.

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For n alkyltr;methylammon;um thiocyanates (CnTA-SCN) the ~ollow;ng ranges for max;mum drag-reduc;ng act;-v;ty were found: n-hexadecyltrimethylammon;um th;ocyanate within the range from 0.02 to 2% by weight, preferably from 0.06 to 0.6X by weight~ w;thin the temperature range from 45 to 65C; and n~octadecyltr;methylammonium th;o~
cyanate with;n the range from 0.04 to 2% by we;ght, pre-- ferably from 0.09 to 0.9X by we;ght, within the tempera-ture range from 55 to 75C, preferably from 60 to 70C
The gener~l rule is that the temperature range with;n wh;ch there is adequate drag-reduc;ng act;vity ;s sh;fted by about 10 15C to h;gher temperatures w;th every add;tional C2-H4 group. In the case of pyr;d;nium compounds, the preferred temperature range is about 5 15 15C lower than, and the requ;red concentrations 1.5 to tw;ce as much as, that of trimethylammonium compounds of the same cha;n-l;nk.
For n-alkyltrimethylammon;um p-toluenesulfonates the follow;ng ranges of max;mum drag-reduc;ng activity were found:
n - 12 : 0.1 to 4% by weight, preferably 0~3 to 2X by ~ ei~ht, for 0 - 15C.
n ~ 14 : 0.05 to 2~ by weight, for 5 to 30C.
n = 16 : 0.05 to 2% by weight, for 15 to 45Cn n = 18 : 0.05 to 2% by weight for 30 to 60C.
There is a very general rule that every additional C2H4 group causes a shift in maximum drag-reducing act;v;ty by 10 ~ 15C to higher temperatures. The - corresponding pyridinium compounds have drag-reducing ..-` ~L2V~342~

activity at concentrations which are higher by a factor of 1.5 to 2 and at temperatures wh;ch are lower by 5 to Both the toluenesulfonates and the thiocyanates have drag-reducing activity even at temperatures above 100C when combined w;th n-alkyltrimethylammonium com-pounds having cha;ns wh;ch are at least 20 to 22 carbon atoms long.
For the group of compounds which have the s~ructure 10 ~C16H33NtcH3)3] ~CxH2x~1COO]~, the limits for - ~aximum drag-reducing activity are as follows:
x = 7 : 0.08 to 2X by weight, preferably 0.2 to 1% by weight f rom 20 to 45C
x = 8 :0.05 to 2% by weight, preferably 0.1 to lX by ~eigh~ f rom 20 to 60C
x = 9 : 0.05 to 2% by ~le;ght, preferably 0.1 to 1X by ~e;ght from 20 to 70C
x = t~: ~.OS to 2X by weight, preferabLy 0.1 to 1X by weight f rom 40 to 100C preferably 50 to 90C
In the case of the analogous pyrid;nium compounds, the maximum l;mits in respect of the concentrations in-crease by a factor of 1.5 to 2 and decrease in respect of the temperature ran~e by 5 - 15C.
We also found that increasing the pH of the aqueous solution to pH values above 9, in particular to pH 10-11, by adding NaOH or other bases, or by adding Na~C03 or other saLts which raise the pH value, signi-ficantly improves drag-reducing activity at the same sur-- factant concentration. A reduction in the pH value by ~zas4~l means of HCl or other strong acids to pH values not greater than 4.5 also leads to an improvement ;n drag-reduc;ng act;vity.
The drag~reducing effect can also be strengthened by adding other foreign electrolytes. Examples of such suitable foreign electrolytes are weak acidsr such as acetic acid or form;c acid, and salts which are formed from the following ions: alkali metal, alkaline earth metal, transit;on metal, ammonium or aluminum cations, hal;des, CLO3~, ClO~ BrO3~, JO3~, S032~, S2O3-~, S042~,

2 8 2 ' 3 ~ pO4 , CO3 ~, CH3COO~, C2O

The amount of these foreign electrolytes uh;ch can be added to strengthen the effect ;s lim;ted at the upper end by the concentration at which there is a salting-out effect for the surfactant. There ;s no concentration lim;t at the lower end.
The effects of the fore;gn electrolytes also de-pends on the valency of the ;ons, the effect shifting to-ward lower concentrations according to the following series: 1-1-valent electrolyte ~2-1~valent electrolyte ~1-2-valen~ electrolyte ~ 2-2-valent electrolyte c~3-2-valent electrolyte C2-3-valent electrolyte. The improve-ment in dra~-reducing activity is particularly marked on add;tion of a salt ~Jhich simultaneously raises the pH
value to pH~ ~.9. For example, the addit;on of Na2C03 - is particularly favorable w;thin the concentrat;on range - ~2~38~

0.1 x C ~ C ~ 10 x C ;f C ;s the molar concentration of the surfactant used.
Instead of add;n~ salts, ;t is also possib~e to proceed by~ for example, using a cety(trimethylammon;um halide or cetylpyridinium halide in a molar ratio of 1:1 together ~I;th an alkal; metal salt of sal;cyl;c acid or a halogenobenzo;c ac;d as drag-reduc;ng agent~ The effect obtained is then equal to the effect obta;ned with cetyl-ammonium ben-~oates in the presence of alkal; metal halides~
The max;mum drag-reducing activ;ty also depends on the time s;nce the preparat;on of the aqueous solut;ons of the cetylammon;um or cetylpyr;d;nium benzoates. Al-though the surfactant solut;ons have a drag-reduc;ng ac-tiv;ty immed;ately `after the solut;ons have been made up, this activ;ty can change markedly in the course of a ~eek.
The t;me requ;red to obtain max;mum act;v;ty can easily ~e determ;ned for a part;cular case by s;mple exper;ments.
In most cases, max;mum act;v;ty is reached at the end of one week~ After th;s time there ;s no further change or ;mprovemel-t ;n the act;vity.
The surfactants ment;oned were mostly texcept;on:
Examples 12 and 13) tested for their drag-reducin~ acti-v;ty ;n a customary manner by measur;ng on the particular aqueous surfactant solution the pressure drop ~ P over the len~th L on flow through a tube of cross-section d for various veloc;ties of flow u. These values can be used to calculate the dimensionless quant;t;es, the drag coef~
f;cient ~ and Reynolds nu~ber Re:

: . . .. : ., :,, ~2~842~

.

` 2 d ~ P
~ u' L

Re= u d . ~

where ~ denotes the density and ~r denotes the kinemat;c viscosity. It ;s customary to ;nsert for p and r the correspond;ng values of the pure solvent, namely of water.
The ~ and Re values thus obtained For the surfactant so~ut;ons s~ud;ed were compared ;n the customary log-log plot aga;nst Re with the correspond;ng values for pure ~ater g;ven by 1/~?_ ~ 2 log Re ~ ~ 0,~ .

10 Drag-reduct;on, or effect;veness as drag-reduc;ng agent ~DR)~ per~ains when ~ HzO ~ ~DR ~ ~ and the s;7e of the drag reduct;on, ;n percent~ is g;ven by:

= X drag reduction = ~ x 100 }1~0 As can be seen from F;gure 1, the sa;d surfactant 15 solutions act as drag-reduc;ng agents ;n such a way that the percentage drag reduct;on increases with ;ncreas;ng Reynolds number~ but that beyond a certain Reynolds number, Rema~ with max;mum percentage drag reduct;on~ it decrea~
ses very rap;dly. A surfactant solution's drag-reducing 20 activ;ty will be character;zed below by the magnitude of Remax; a surfactant solution with Re~ax = 20~000 accor--; d;ngly ;s more effect;ve as a dra~ reduc1ng agent than a , ~0~

surfactant solution with Remax = 10,000. The assoc;a-ted ~ -value is desi~nated d max The studies of the surfactant solutions only gave reproduceable results ~hen the aqueous solutions of the surfactant salts had each been stored for about one week before the measurements at the measurement temperatures. It is true that the solu-t;ons showed drag-reduc;ng activ;ty even immed;ately after having been made up but the drag-reducing act;vity can show a marked change within the course of one week.
The surfactants thus pretreated were subjected to a large number of tests. For instance, extended tests over several days demonstrated, as can be seen from Exam-ples 11 and 13, that the drag-reducing activ;ty of the sur~actants listed is not subject to mechanical or chemi-ca~ degradation. We also found that the drag-reduc;ng activ;ty of the surfactants mentioned increases with ;ncreas;ng concentrat;on; however, the v;scos;ty of the solut;ons also ;ncreased, so that the percentage drag reduct;on becomes poorer at relatively low Reynolds numbers ~cf~ F;gure 1~. However, we also observed that the thermal stabil;ty of the surfactant solut;ons ment;oned, ;.e. the;r drag-reducing act;vity at high temperatures, increases with increasing concentration ~cf. Examples 1 and 2).
The thermaL stability ;s not only determ;ned by the con-centration but also by the surfactants themselves; forinstancep the tests showed that the temperature range over which there ;s drag reducing activity is generally slightly lower ~8 ~ 12C) in pyr;d;nium compounds than ;n tr;-.
- methylam~onium compounds.

~ZV~2~

The stud;es carried out show that the surfactant salts mentioned are useFul as drag-reducing agents wherever water is pumped through p;pes, but in particular where water is constantly pumped ;n a cycle through a p;pe net-work, as, for example, ;n cool;ng cycles, s;nce th;s par-t;cular application of necessity requires the drag-reducing agent to have substantial long-term stability, which is what the said surfactant salts have~ The surfactant salts can be metered into the water flowing through the p;pes not only ;n the form of a concentrated surfactant solut;on tl 10% by wei0ht) but can also be added as pure crystal-line surfactant salts. Ow;ng to the effic;ent mixing effect, the most su;table place for meter;ng ;nto the pipe network ;s shortly before a pump.
Example 1 Hexadecyltr;methylammon;um sal;cylate (abbrev;ated below to CTA-Sal) was made up ;nto concentrat;ons, in dem;neralized water, of 130, 150, 200, 300, 500, 750, 1000, 1500 and 2000 ppm by we;ght by we;~h;ng 0.13, 0~15, 0.2, 0.3~ 0.5, 0.75, 1.0, 1.5 and 29 of CTA-Sal ;nto 1000g of dem;neralized water. The salt was dissolved by stirring at room temperature, and the solutions were briefly heated to about ~0C, cooled down to 2ZC and stored without stirr;ng at th;s temperature for 1 week.
2~ They were then tested for drag reduct;on ;n a tur-bulence rheometer (Polymer Letters ~,851 (1971)~ by ~orc;ng 1.5 l;ters of liquid w;th a p;ston through the measuring p;pe as in a hypodermic needle. The p;ston is acclerated dur;ng the measurement, so that an ent;re flow curve .. ~ . -~20t34Z~

as sho~n ;n F;gure 1 is recorded ;n one measurement. The diameter of the measuring pipe is 3 mm, the length over which ~ P is measured is 300 mm, and the inlet section is 120n mm long.
S The same CTA-Sal concentrat;on ser;es was measured in this apparatus at 22C and 52C after the solution had also previously been stored at 52C for one week.
Figure 1 shows the flow curves for CTA-Sal at l50, 750 and 1500 ppm. Tables 1 and 2 summarize the re-sults of all measurements for 22C and 52~C in the form of Remax and ~max Example 2 Solut;ons of hexadecylpyr;d;n;um sal;cylate in uater were prepared at the concentrat;ons of 200, 250, 300 SOO and 1000 ppm, and ~ere ;nvest;gated ;n the turbulence rheometer at 2SC and 40C for drag reduction in the manner described ;n Example 1. As can be seen from Table 30 there is a marked drag-reduc;ng effect at 25C from 300 ppm and at 40QC from 500 ppm.
~ e~
Ident;cal solut;ons conta;n;ng a CTA-Sal concen-trat;on of 750 ppm were made up as in Example 1~ adjusted to pH 3.2, pH 4~2r pR ~.95, pH 7.~, pH 10 and pH 10.9 w;th HCl for pH C 7 and NaOH for pH ~ 7, and measured at 22C ;n the turbulence rheometer.
HaOH and HCl were added before the solutions were heated up to 9nc, and the pH valuès were measured immediately before the measurement in the turbulence rheometer. As the results ;n Table 4 show, the adjustment of the pH

~;~0~342~
~ 5 -value to pH ~ 4.2 and pH ~ 10 g;ves a marked improve-ment in dra~-reducing activity compared with an equal strength solution of pure CTA~Sal, as the comparison with Example 1 shows.
E mpLe 4 Various amounts of NaCl were made up .ogether with CTA-Sal as described in Example 1 to aqueous solutions whose CTA-Sal concentrat;on (in mole/liter~ was in every case 750 ppm t1~78 x 10 3 mole/liter) and NaCl concen-tration as follo~s:
1 x 10 4, 5 x 10 4, 1 x 10 3, 1.8 x 10 3, 5 x 10 3, 0.01~ 0.05, 0.1, 0.35, 0~7 and 1Ø
The results of the investigation of drag reduction at 22C in the turbulence rheometer are summar;zed in Table 5. As can be seen from Table 5, addit;on o~ NaCl in up to a S0-fold molar excess improves CTA-Sal's drag-reducin~ activity.
Example S
By means of the method descr;bed in Examples 1 and 4, aqueous solutions were made up to conta;n ;n each case 750 ppm (1.78 x 10 3 mole/l;ter) of CTA-Sal and the following Na2C03 concentrat;on (in mole/liter):
1 x 10 ~, 2 x 10 4, 1.78 x 10 3, 6 x 10 3, 0.02 and 0.1.
The results of the investigat;on of drag reduction 2S in the turbulence rheometer at 22C are summarized in Table 6. Even the addition of only 2 x 1~ 4 mole of Na2C03 per liter combined w;th an increase in the pH of the solution to pH 10 g;ves a marked improvement ;n drag-reducing activity compared with a pure 1.78 x 10 3 molar ~ 8~

CTA-Sal solution ;n water, Example 6 By means of the method described ;n Examples 1 and 4, aqueous solutions were made up to contain ;n each case 75Q ppm ~1.78 x 10 3 mole/l;~er) of CTA-Sal and the following CaCl2 concentration (in mole/liter):
1 x 10-4, 3 x 10-4, 1 x 10-3, 1.78 x 10 3, 4 x 10 3, 0.01, 0.1 and 0.5.
The results of the investigation of drag reduction in the turbulence rheometer at 22~C are summar;zed ;n Table 7. There is a marked improvement ;n drag-reduc;ng act;vity compared w;th a pure 1.78 x 10 3 molar CTA-Sal solut;on ;n water at CaCl2 concentrations within the range from 3 x 10^4 to 0.1 mole/liter.
Example 7 By means of the method descr;bed in Examples 1 and 4, aqueous solut;ons were made up to contain in each case 750 ppm (1.78 x 10 3 mole/liter) of CTA-Sal and the followin~ Na2S04 concentrat;on tin mole/lit2r):
1 x 10-4, 2 x 10-4, 3 x 10-4, 1 x 10-3, 1.7~ x 10~3, 4 x 10 3, 0~01 and 0.1.
The results of the ;nvestigation of drag reduct;on ;n the turbulence rheometer at 22C are summarized ;n Table 8. There ;s a marked ;mprovement in drag reducing activity compared with a pure 1n78 x 10 3 molar CTA-Sal soiution in water at Na2S04 concentrations within the range from 1 x 10 4 to 0.1 mole/liter.
Example 8 .
By means of the method described in Examples 1 and ~Z~84~Z~
- 17 ~

4, aqueous solutions were made up to contain in each case 750 ppm (1.78 x 10 3 mole/liter) of CTA-Sal and the fol-Low;ng MgHpO4 concentration ~in mole/l;ter~.
8 x 1~-5, 1 x 10-4~ 2 x 10-4, 6 x 10 4, l x 10 3, and 1.78 x 10 3~
A precipitate forms at M~HpO~ concentrations from x 10-3 mole/l;ter. The results of the ;nvest;gation of dra0 reduction in the turbulence rheometer at 22C
are summar;zed in Tab(e 9~ There ;s a marked improvement ;n drag-reducing activity compared with a pure 1.78 x 10 3 molar CTA-Sal solution in water at MsHpO~ concentrat;ons with;n the range from 8 x 10 5 to 1.8 x 10 3 mole/L;ter.
Example 9 By means of the method descr;bed ;n Examples 1 and 4, aqueous solutions were made up to contain in each case 750 ppm (1.78 x 10 3 mol-e/liter) of CTA-Sal and the following Fe2(S04)3 concentration S;n mole/L;ter):
5 x 10-5, 1 x 10-4, 2 x 13-4, 3 x 10-4.
A prec;p;tate forms and drag~reducing activity de-creases for an FE2(S0~)3 concentrat;on from 3 x 10 4mole/L;terO The results of the invest;gat;on of drag reduction in the turbulence rheometer at 22C are sum-mar;zed in Table 10. There ;s a marked improvement in drag-reducing activity Gompared with a pure 1.78 x 10 3 ZS molar CTA-Sal solution in water at Fe2(S04)3 concentra-tions w;th;n the range from 5 x 10 5 to 3 x 10 4 mole/
liter.
Example 1D
By means of the method described in Examples 1 ~ r .

~20~

and 4, aqueous solutions of hexadecyltrimethylammonium m-chlorobenzoate were made up in concentrations o~ 2000 ppm and 5000 ppm by weighing out equimolar amounts of the salts hexadecyltrimethylammonium brom;de and sodium p~chloro-S benzoate. The finished solutions also conta;ned the cor-responding molar amount of NaBr. The results of the in-vestigation of drag reduction in the turbulence rheometer are summar;zed ;n Table 11.
Fxample 11 For an extended test, an aqueous solution was pre-pared of hexadecyltrimethylammonium salicylate to have a total content of 700 ppm from a 1:1 molar m;xture of hexa-decyltrimethylammonium brom;de (CTA-Br) and sod;um sali-cylate (Na-Sal) by we;gh;ng 92.~g of CTA-Br and 40.6g of Na-Sal into 190 kg of water. The substances were dissol-ved by stirring the coLd mixtures, and the solutions were then conditioned at 60C for 5 hours and then stored at 23 for 6 days.
Drag-reducing act;v;ty ~as invest;gated ;n a flow ~0 apparatus (cf. for example, Ind. Eng. Chem~ Proc. Des;gn Developm. 6,309 ~1967)) in wh;ch the solution is pumped in a cycle through pipes. After an appropriately long ;nlet section, the pressure drop is measured over a section which is 1 m long and has a cross-section of 1.4 cm. The pump used was an adjustable screw pump from Netzsch, namely the 2NE 80 model~
The said solution of CTA-Sal and NaBr was subjected at room temperature in th;s flow apparatus to the follow-ing Measurements, which were carr;ed out in succession

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~ 19 -without a break in between 1) a flow curve measurement at 23C 1 hour after the solut;on has been poured ;nto the apparatus;
2) an extended test over 7 days at a flow velocity of 3.1 m~s, which corresponds to a Reynolds num-ber of Re ~ 53,000;
3) a flow curve measurement ;mmediately on comple-tion of the extended test;

4) an extended test over 16 hours at a Reynolds num-ber of Re ~Remax, i.e. at a flow velocity of

5.5 m/s, wh;rh corresponds to Re = 90,noo;
5) a flow eurve measurement immed;ately on comple-t;on of the extended test; and

6~ a flow curve measurement after 3 days at rest.
Table 12 summar;zes the results of the measure-~ents 1-6.
Example 12.
By means of the method described in Example 11, an aqueous CTA~Sal solution was prepared from CTA-Br and Na-Sal to have a total CTA-Sal and NaBr content of 10,000 ppm ~ 1% by weight, and invest;gated in a disk apparatus at 23C, 60C, 70C and 8UCA In the said disk apparatus, a disk which has a diameter of 20 cm revolves in the solution under test. Disk and solution are inside 25 a thermostated casing which has an internal diameter of 22cm, and the gap between ~he bottom plate and the top plate amounts to 1~1 cm~ The tor~ue, M, of the disk is measured as a ~unction of the number of revolutions per minute, U.

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The two measured quant;ties can be used to calcu-late the following dimensions as variables:
M
= drag coefficient = _ _ 2 5 1/2 ~ C~ R

Re = Reynolds number ~
M is the torque,L"I denotes the angular veloci~, t~e other sylr~ls have the meamng as give3l oll page 11, The log-log plot of ~i~
a~ainst P~ then gives flaw curves as sh~ in Figur2 2 which can be ccan-pared wit~ the flow curves for pipe flaw. ~he flaw curves for ~rdter in the turb~lent regic~ is given ;~ 0 0995 by .ReO, 2 and is shown in Figure 2 as the solid straight l;ne. The drag reduct;on, ~ , ;s calculated as for pipe flow. Figure 2 shows the flo~ curves for the said CTA-Sal solut;on for the turbulent region at 23C, 60C, 70C and 80C.
As the figure shows, there is marked drag reduction ~ithin the range 23C - 70C, and there is a small residual effect even at 80C.
Example 13 8y means of the method described in Examples 1 and 4, an aqueous solution contaîning 750 ppm of CTA-Sal tl~78 x 1~ 3 mole~liter) and 1.78 x 10 3 mole of Na2C03 per liter was made up, and subjected to an 11 day test in the disk apparatus after the flo~ curve had been measured as described in Example 1~.
The flo~ curve gave a max;mum drag reduction of ~ max = 36X at Remax ~ 1.09 x 10~ Nh;ch corresponds to a number of revolutions of the disk per minu~e of U =

1D18 r.p.m~ The extended test ~as then carried out at 3~20~34;~

Re = 1.Q2 x 10b, which corresponds to 913 r.p.m. Table 13 conta;ns the values for the drag reduct;on ~ after each day.
Examp(e 14 By means of the method descr;bed in Example 1, solut;ons of hexadecyltrimethylammon;um thiocyanate (CTA-SCN) were prepared with concentrations of 200, SOO, 750, 1000 and 2000 ppm, and measured at 45 and 55C in the tur-bulence rheometer. Table 14 summarizes the results.
Example 15 By means of the method descr;bed ;n Examples 1, 3 and 4, aqueous solutions were made up to contain 750 ppm in each case t2.19 x 10 3 mole/liter) of CTA-SCN and the follow;ng NazCO3 concentrations (in mole/liter):
~ x 10 4, 2 x 10 4, 1 x 1C 3, 1.78 x 10 3 and 4 x 10-3.
In a second test, solut;ons which each contained 750 ppm of CTA-SCN were adjusted with NaOH to a pH 10.8 and w;th HCl to a pH 2.7.
Table 15 summar;zes the results of the ;nvestiga-tion of drag reduction in the turbulence rheometer at45C.
Examp~e 16 By means of the method descr;bed in Example 4, solutions were made up o-f hexadecylpyridin;um th;ocyanate ~5 conta;ning concentrations of 500 and 1000 ppm, and measured at 45C in the turbulence rheometer. Both solutions had a drag-reducing effect, namely at 500 ppm with Remax =
4400 by ~max = 53% and at 1000 ppm with Remax = 64CO
by ~max = 54X.

2(~34i~

.

Example 17 By means of the method described ;n Example 10, aqueous solut;ons were made up to conta;n var;ous concen-trations of n-aLkyltrimethylammonium thiocyanate ~CnTA-SCN) by wei~hing out equimolar amounts of the saltsn-alkyltrimethylammonium chloride and sodium thiocyanate.
The f;n;shed solutions thus also conta;ned the correspon-ding molar amounts of NaCl. The results of the invest;-gat;on of drag reduction in the turbulence rheometer are summar;zed in Table 16.
Example 18 By means of the method descr;bed in Examples 10 and 17~ aqueous solutions were made up of n-alkyltr;methyl-ammonium p-toluenesulfonate ~CnTA-PTS) by weighing out equimolar amounts of the salts CnTA Cl and sodium p-toluenesulfonate. The results of the investigat;on of drag reduction ;n the turbulence rheometer are summar;zed in Table 17.
E_ ple 19 By means of the method descr;bed ;n Examples 10 and 17, aqueous solutions were made up of hexadecyltr;methyl-ammon;um n-alkylcarboxylate (CTA-CxH2x+1COO) by weigh-;ng out equimolar amounts of the salts CTA Cl and CxH~x~1Coo.
The results of the investigation of drag reduction in the turbulence rheometer are summarized in Table 18.

2~

Table 1 CTA-Sal ~max T ~C~ Concentration ~ppm~ Remax (% drag reduction) 22 130 5300 + 500 56 + 3 22 150 5400 ~ 500 57 + 3 22 200 5200 + 500 5~ + 3 22 300 4700 + 500 ~6 + 2 22 S00 5400 + 500 52 + 3 22 750 6700 + 700 53 + 3 22 1000 10500 + 100064 + 3 22 1500 12300 + 120064 + 3 22 2000 14400 ~ 140065 + 3 Table 2 CTA - Sal ~max T LC~ Concentration [ppm~ Remax (~ drag reduction) . . .

" 150 200 ~ no effect " 300 _ " 50O 5100 + 500 59 + 3 " 750 8400 + 800 65 + 3 " 1000 10300 ~ 100066 + 4 " 1500 16600 + 160069 + 4 2000 18600 + 180068 + 4 84~

Table 3 C e t y l p y r i d i n i u m s a l i c y ~ a t e Tt C~Concentration ~ppm~ Remax ~max~

300 4500 + 500 54 ~ 3 500 5800 + 600 55 + 3 1000 7600 + 800 57 ~ 3 500 4200 + 400 54 + 3 1000 6500 + 70063 t 3 Table 4 . .
.~,easurement Te~erature 22C; CTA-Sa~ concentrat;on: 750 ppm rP p ml, p H m a x m a x [

.
750 3.2 10900 + 1100 65 + 3 750 4. 2 9200 ~ 900 64 + 3 750 4.95 6600 + 700 ` 53 ~ 3 750 7. ~ 6400 + 600 59 + 3 750 ` 10 8100 ~ 800 61 + 3 75Q 1 n . 9 14600 + 1400 69 + 3 3L2~ Z~

Table 7 r leasurement Te~pera ture 22&; C T A - S a l c o n c e n t r a t; o n : 750 p p m CaC l2 concent rat i on mo l e / l i t e r ppm ma x x 10 4 11 10800 + 1100 64 + 3 3 x 10 4 34 11800 + 1200 65 + 3 x 10 3 111 16200 + 1600 68 + 3 1.78 x 10 3 200 16700 + 1600 69 ~ 3 4 x 10 3 440 15300 + 1500 68 + 3 1 x 10 1110 16400 + 1600 68 ~ 3 x 10 111100 10600 + 1100 62 ~ 3 Table 8 .
reasurement Terperature æ c; CTA-Sal concentration: 750 ppm Na2S04 concentration mole/liter ppm max oc max [%~
x 10 4 14 16000 + 1600 67 _ 3 2 x 10 4 29 17800 ~ 1800 70 + 3 3 x 10 4 43 16900 _ 1700 70 + 3 x 10 3 140 18300 _ 1800 69 _ 3 1.78 x 10 250 18000 ~ 1800 69 + 3 4 x 10 3 570 18700 + 1900 69 3 x 10 1420 17300` + 1700 68 + 3 1 x 10 114200 13900 + 1400 60 ~ 3 .

~2~)8~2~

TabLe 5 Measurement Ten~erature 22&; C T A - S a l c o n c e n t r a t i o n : 750 p p m NaCl concentration mole/l;terppm Remax ~max C%~
x 10 4 6 6000 600 55 + 3 5 x 10 429. 5 10200 + 1000 66 _ 3 x 10 358 . 5 11600 _ 1200 66 + 3 1.78 x 10 3100 13600 + 1400 68 _ 3 5 x 10 3290 16000 160068 3 x 10 2590 15900 + 160067 + 3 5 x 10 22900 14600 + 150067 _ 3 O .10 5800 13800 + 140067 + 3 0.35 20500 ~ Smal l residual drag-reducing 0.70 40900 effect of 10 -20X w-ithin the 1.00 585Q0 Reynolds number range from 4000 - 15000.

Table 6 NleasureTent Ten,perature ~2C; C T A - S a l c o n c e n t r a t i o n : 750 p p m Na2C03 concent rat i on mole/liter ppm pH Re . ~max [~
__ __ m a x 1 x 10 4 10.6 7.67100 _ 700 57 + 3 2 x 10 4 21.2 10.014300 + 1400 68 + 3 1.78 x 10 3189 10.616600 + 1700 68 + 3 6 x 10 3 636 11.0 15900 + 1600 66 + 3 2 x 10 2 2120 11.2 16500 + 1600 60 + 3 *)1 x 10 110600 11.1 13400 _ 1300 65 + 3 *)Solution already contains small amounts of precipitate.

~013~2~1 Table 9 Measurenænt Te~erature 22C; C r A - S a l c o n c e n t r a t i o n : 750 p p mMgHP04 concen t rat i on mole/liter ppm R max ~ max [%~
8 x 10 5 14 14400 + 1400 68 + 3 x '10 417.5 14300 + 1400 66 ~ 3 2 x 10 4 35 15500 ~ 1600 68 ~ 3 3 x 10 4 52 16800 + 1700 68 + 3 6 x 10 4105 17200 + 1700 69 + 3 x 10 3175 16500 + 1600 69 + 3 *)1.78 x 10 33?0 16300 + 1600 68 + 3 *) The solution showed marked turbidity.

Table 10 I~leasurement T~Tperature 22 C; C T A - S a l c o n c e n t r a t i o n : 750 p p m FE2(S04)3 concentration mole/liter ppm pH Remax CmâxL%~

5 x 10 5 20 4.513500 + 1400 68 ~ 3 x 10 4 40 4.117700 + 1800 68 + 3 2 x 10 4 80 3.915900 + 1600 68 ~ 3 *~ 3 x 10 4 120 3.717400 ~ 1700 66 ~ 3 *) Small amount of precipitate present in the solwtion.

- 28 ~
Table 11 T~C~ Surfactant Con- Remax max t centrat;on [ppm~
-5000 31700 _ 3200 70 + 4 200U 15800 + 1600 68 + 3 Table 12 Measure- Remax C3cmax C%~ ~
ment 50000 + 2500 77 + 4 2 *) 53000 + 25no 61to 75 + 4 3 48000 + 2500 ~76 ~ ~t 4 *) 90000 no effect **) S 47000 + 2500 76 ~ 4 6 49000 + 2500 76 + 4 *) Re numbers for the extended test.
**) Since this extended test ~as carr;ed out at Re>Re , there was no drag reduction.
max Table 13 Measurement Temperature 22C; CTA-Sal - - 1.78 mole/liter + Na2C3 - 1.78 mole/liter Time(Days) Re a~ maxt7~3 0 1.02 x 106 33 + 2 1.02 x 106 32. _ 2 2 1.02 x 106 32 + 2 3 1.02 x 106 32 + 2 4 1.02 x 10~ 35 * 2 1.02 x 1o6 35 + 2 6 1.02 x 105 36 ~ 2

7 1.02 x 106 33 + 2

8 '1.02 x 106 - 33 + 2 11 1.02 x 106 32 + 2 .

~L2~

Table ?4 CTA-SCN
T~ C~ Concentration [ppm~ Remax Cmax ~%.¦
. . _ _ . . . _ . . _ _ .
200 4100 + 400 57 + 5 500 8500 + 900 57 + S
750 9300 + 900 57 + 5 1000 -12100 + 1200 60 + 6 2000 18800 + 1900 65 + 6 750 6300 51 + 5 1000 9900 67 + 6 2000 20400 68 + 6 Table 15 . . .

Measurement Temperature 45C; CTA-SCN concentration: 750 ppm Na2C03 con pH Re cC
centration max max moleJliter . _ _ . . _ _ . _ .
1 x 10 4 7~5 8700 + 90D 55 ~ 5 2 x 10 ~ 10.0 10700 ~ 1400 58 + 5 1 x 10 3 10.3 14600 + 2500 67 + 3 1~78 x 10 31 n . 6 9100 + 900 66 + 3 4 x 10 10.8 - -. _ _ _ _ . _A
Addition of HCl 2.7 10000 + 1000 63 + 3 Addltion of NaOH 10.814400 + 1400 67 + 3 12~18~

Table 16 CnTA-SCN + NaCL

CnTA T[C~ tion ~ppm~ max Cmax ~%~

C18T~ 60 5005400 + 500 31 _ 3 C18TA 60 8006300 + 600 46 + 4 CZO/Z2TA 90 3006500 + 700 61 + 6 C20t22TA 90 30011100 _ 1000 64 + 6 , CnTA represents ~CnH2n+1N(cH3)3~+

Table 17 `~ -_ CnTA-PTS + NaCl CnTA T[C~ Concentra- max GCmaxt ]

C16TA 22 5000 25800 + 2600 65 * 6 C16TA 40 4000 3300 + 400 35 + 3 C18TA 40 1000 3600 _ 400 41 + 4 Z0/22 60 1000 5000 + 500 28 + 3 C1~TA 4Q 3000 6800 + 700 28 + 3 ~ TA represents ~CnH2n+1N(CH~)3~

1~0~ 2~

Table 1~

CTA ~xH2x+1C + NaCl Cx~l2x~1C T~C~ Concentra- max ~max . .
C7H15C00- 45 50003700 + 400 36 + 3 8 17 22 500040200 + 400073 + 7 8H17C 60 30003500 ~ 300 41 + 4 8 17 60 50004700 + 500 35 + 3 C9H19C00- 22 20ao22900 ~ 230070 + 7 10HZ1 C0O 40 200027100 ~ 240045 + 4

Claims (4)

Claims:

1. A process for reducing the drag of aqueous media in turbulent or pulsating flow, which comprises adding to the aqueous medium a compound of the formula R1-K?A?
in which K denotes a group of the formula or ,R2 denotes C1-C3-alkyl, preferably methyl, A denotes an anion of the following formulae Hal denotes fluorine, chlorine, bromine or iodine, R3 denotes C7-C10-alkyl or C7-C10-alkenyl and if A =

thiocyanate, R1 denotes C16-C26-alkyl or C16-C26-alkenyl, if A = p-toluenesulfonate, R1 denotes C12-C26-alkyl or C12-C26-alkenyl, and if A has one of the remaining meanings R1 denotes C16-alkyl or C16-alkenyl.

2. The process as claimed in claim 1, wherein the com-pounds are added in an amount of 0.01 to 2% by weight.

3. The process as claimed in claim 1, wherein, in addition, the solution is adjusted to a pH value of up to 4.5 or above 9 by adding acids or bases respec-tively.

4. The process as claimed in claim 1, wherein alkali metal, alkaline earth metal, transition metal, ammonium or aluminum salts are also added.