WO2004069957A1

WO2004069957A1 - Formate and/or acetate and/or propionate based heat transfer fluid

Info

Publication number: WO2004069957A1
Application number: PCT/FI2004/000053
Authority: WO
Inventors: Timo Nissinen; Jari Kukkonen
Original assignee: Kemira Oyj
Priority date: 2003-02-04
Filing date: 2004-02-03
Publication date: 2004-08-19
Also published as: FI116900B; FI20030167A0; FI20030167A

Abstract

The invention concerns a heat transfer fluid composition containing alkali salt of formic acid and/or acetic acid and/or propionic acid, and a polyelectrolyte to prevent leakage of the heat transfer fluid.

Description

Formate and/or acetate and/or propionate based heat transfer fluid

Technical field

The present invention relates to improvements in frost resistant, aqueous heat transfer fluids containing alkali salt of formic acid and/or acetic acid and/or propionic acid. The fluids can be used for cooling or heating especially in applications in which it is important to prevent leakages.

Background of the invention

Aqueous fluids containing alkali salt of formic acid and/or acetic acid and or propionic acid have been used as heat transfer fluids. E.g. FI-B-101547 describes such a heat transfer fluid containing potassium formate. Such fluids are also commercially available (e.g. FreeziumTM, Kemira Chemicals Oy, Finland)

A major problem in the use of aqueous heating/cooling fluids containing alkali salt of formic acid and/or acetic acid and/or propionic acid is their tendency to leak.

The purpose of the present invention is to provide a leak protected heat transfer fluid of the above mentioned type.

Disclosure of the invention

Now a heat transfer fluid composition in accordance with claim 1 has been invented. The fluid contains alkali salt of formic acid and or acetic acid and/or propionic acid, and a polyelectrolyte.

Surprisingly it has been found that the polyelectrolyte reduces the wetting power and thus decreases the leakage tendency. Good leak protection is achieved already by a small amount of polyelectrolyte.

The polyelectrolyte also prevents the formation of scales. Thus it allows the user to maintain the heat transfer fluid's efficiency. The surface adsorption of the polyelectrolyte on the growth sites of scale forming crystallites and crystal growth inhibition and distortion hereby is the most plausible explanation of the mechanism for scale inhibition. Thus, in accordance with the invention, excellent leakage protection is achieved, but the fluid still exhibits an effective heat transfer between a metal surface and the fluid.

The use of the polyelectrolyte provides also other advantages. Namely, the polyelectrolyte also prevents corrosion and acts as a lubricant. Corrosion typically starts beneath scales and deposits inside tubes. When the polyelectrolyte prevents the formation of scales and salts, it also inhibits corrosion. The polyelectrolyte also acts as a lubricant and reduces wearing of e.g. pump gearings by forming just a few molecular layer thick layers on the metal surfaces.

The polyelectrolyte may be, e.g., a polymer or copolymer of acrylic acid, such as sodium polyacrylate or a copolymer of sodium acrylate and acrylamide, polymaleic acid or its derivative, polymetacrylic acid or its derivative, acaria, agar, alginate, carrageenan, gum tragacanth, xanthan gum, collagen, carboxypolymethylene, or glyceryl monostearate. Also mixtures of polyelectrolytes can, of course, be used.

The content of the alkali salt should preferably be 5 to 70 weight-%, calculated on the total weight of the fluid. The amount of the polyelectrolyte may be, e.g., 1 to 1000 ppm, preferably 5 to 100 ppm.

Especially polyacrylates or copolymers thereof can be used as the polyelectrolyte.

Optionally suitable additives, such as corrosion inhibitors and /or pH buffering agents, may be used in connection with this heat transfer fluid.

Examples

Leakage tests

The leakage tendency of potassium formate based heat transfer fluids was tested.FreeziumTM (Kemira Chemicals) fluid, and FennopolTM A 392 (Kemira Chemicals) polyacrylate were used in the tests. Freezium fluid contains potassium formate. Fennopol A 392 polyacrylate contains copolymer of sodium acrylate and acrylamide.

Either Freezium -15oC, Freezium -15°C +10 ppm of Fennopol A 392 or tap water were filled into a leakage test apparatus. The test apparatus consisted of six Swageloc joint parts and three pieces of tubes that were connected to each others so that exactly determined joints were formed. Only the end joint at the bottom of the test apparatus was tightened totally leak proof. All materials were of AISI 316 stainless steel. First, tap water was filled into the test apparatus. No leakage was observed during four days test period. Then Freezium -15°C was put into the test apparatus. After about two days testing time, leakage was observed at the upper parts of first and second joints. Then Freezium -15°C was poured out of the test apparatus and Freezium -15°C containing 10 ppm of Fennopol A 392 was put into. Surprisingly, no leakage was found after four days test period. Then the test solution was poured out and the test apparatus was also cleaned with warm tap water. After this, Freezium -15°C containing no additive was put into. Leakage was again observed at the upper parts of first and second joints after about two days testing time. Freezium -15°C was again poured out and Freezium -15°C containing 10 ppm of Fennopol A 392 was put into. Even after ten days testing time there was no leakage.

Obviously the amount of 10 ppm of polyacrylate can be used in the final solution so that the solution will not readily penetrate or seep through small leaks and so that the same will not tend to spread over solid surfaces such as pumps, valves and nozzles.

The same very thin polyacrylate layer also prevents salt formation nearby the leaks. Specially galvanised steel and zinc are very vulnerable to corrosion beneath such formate salt precipitates.

Viscosity measurements

When the leakage of a heat transfer fluid is prevented, the viscosity of the fluid should not substantially be increased. Namely, the more viscous is the heat transfer fluid, the worse is the heat transfer. In Table 1 it is shown the effect of 10 ppm ppm of Fennopol A 392 on the viscosity of Freezium -15°C and Freezium -60°C.

Table 1. The effect of 10 ppm of Fennopol A 392 on the viscosity of Freezium -15°C and Freezium -60°C

In Table 2 it is shown the effect of 20 to 50 ppm of Fennopol A 392 on the viscosity of Freezium -15°C and Freezium -40°C.

On the basis of the tests it is obvious that the viscosity of Freezium fluid is not substantially increased due to the addition of polyacrylate so that the fluid still poses its main advantage, i.e. low viscosity.

Table 2. The effect of 20, 30, and 50 ppm of Fennopol A 392 on the viscosity of Freezium -15°C and Freezium -60°C.

Test solution 22°C Change -10°C Change cSt in % cSt in %

Freezium -15°C 1.15 - 2.74 -

Freezium -15°C + 20 ppm Fennopol A 392 1.15 0.0 2.86 4.4

Freezium -15°C + 30 ppm Fennopol A 392 1.17 1.7 3.00 9.5

Freezium -15°C + 50 ppm Fennopol A 392 1.46 27.0 3.59 31.0

Freezium -40°C 1.60 - 3.73 -

Freezium -40°C + 20 ppm Fennopol A 392 1.69 5.6 3.77 1.1

Freezium -40°C + 30 ppm Fennopol A 392 1.79 11.9 3.90 4.6

Freezium -40°C + 50 ppm Fennopol A 392 1.77 10.6 3.95 5.9

Claims

1. Heat transfer fluid composition containing alkali salt of formic acid and/or acetic acid and/or propionic acid, characterized in that it also contains a polyelectrolyte to prevent leakage of the heat transfer fluid.

2. The composition according to claim 1, characterized in that the polyelectrolyte is a polymer or copolymer of acrylic acid, such as sodium polyacrylate or a copolymer of sodium acrylate and acrylamide, polymaleic acid or its derivative, polymetacrylic acid or its dericvative, acaria, agar, alginate, carrageenan, gum tragacanth, xanthan gum, collagen, carboxypolymethylene, or glyceryl monostearate, or a mixture thereof.

3. The composition according to claim 2, characterized in that the polyelectrolyte is a polymer or copolymer of acrylic acid.

4. The composition according to claim 3, characterized in that the polyelectrolyte is a copolymer of acrylate and acrylamide.

5. The composition according to any preceeding claim, characterized in that the concentration of the polyelectrolyte is 1 to 1000 ppm, preferably 5 to 100 ppm, of the weight of the composition.

6. The composition according to any preceeding claim, characterized in that it contains alkali salt of formic acid.

7. The composition according to claim 6, characterized in that it contains potassium salt of formic acid.

8. The composition according to any preceeding claim, characterized in that the concentration of the alkali salts of formic acid and/or acetic acid and/or propionic acid is 5 to 70 w-% of the weight of the composition.

9. The composition according to any preceeding claim, characterized in that the composition additionally contains corrosion inhibitors and/or pH buffering agents.