General topics on the use of glycerol as coolant

Transcription

1 General topics on the use of glycerol as coolant Milan - 19 th October 2012 Manuela Toscanini eni refining & marketing Centro Ricerche San Donato Milanese

2 Summary Introduction The role of the coolant Physical-chemical characteristics Technological characteristics Coolants composition and main categories of products A brief history on coolants MEG,MPG and glycerol Specifications Conclusions 2

3 Introduction The coolants are universally used The main fields of application are: Automotive Marine Energy production and industrial cooling 3

4 The role of the coolant Heat transfer Main characteristics The ability to cool the engine very rapidly, improve heat exchange and maintain this property for the whole cycle life of the fluid Corrosion protection The ability to provide protection against corrosion of all metals present in the cooling circuit Cavitation protection The ability to delay the manifestation of cavitation Freezing protection The ability to remain fluid at any different external temperature condition Compatibility Compatibility with all the components of the cooling circuit Characteristics retention The ability to maintain the physical-chemical characteristics (ph, alkalinity reserve, foaming) during the service life 4

5 The role of the coolant Operational constraints Wide range of temperatures Hardness of the dilution water Variety of metals with which they come in contact (cast iron, solder, steel, copper, brass, aluminum) Cavitation can occur due to the type of the cooling circuit, the fluid flow, Presence of electrochemical reactions 5

6 Physical-chemical characteristics Appearance / colour Density Water content Boiling point Freezing point ph Alcalinity reserve Foam tendency Compatibility with hard waters 6

7 Physical-chemical characteristics Appearance / colour The product should be clear without any precipitate. The color may be different depending on the manufacturer. Different colours are used to distinguish thproducts from a maunfaturer to another. The most common colors are: green, blue, orange, pink, red,... Density It depends on the type of glycol used. The density is a very important measure that gives informations about the dilution of a coolant during its service life. 7

8 Physical-chemical characteristics Water content It must be 5% maximum. The presence of water is the result of chemical reactions that occur during the coolant preaparation, as for example, the neutralization of organic acids with a base (typically NaOH) to give salts. The water content influences both the freezing point and the boiling point. 8

9 Physical-chemical characteristics Boiling point It must be in the range C for a concentrate coolant. It depend on the water content. Specifications require a minimum value for 50:50 mixtures. An pressure increase in the system from 1 to 2 bar causes an increase of the boiling point of about 10 C. Freezing point It s the temperature at which the first crystals ice appear. It depends on the concentration of the coolant in water. The specifications require a minimum value for 50:50 mixtures. 9

10 Physical-chemical characteristics Freezing Point of water/glycol solutions Source : MEGlobal- Ethylene Glycol Product guide 10

11 Physical-chemical characteristics Boiling point at different pressures of watyer/glycol solutions Source : MEGlobal- Ethylene Glycol Product guide 11

12 Physical-chemical characteristics Specific heats of water/glycol solutions at different temperatures Source : MEGlobal- Ethylene Glycol Product guide 12

13 Physical-chemical characteristics Thermal conductivity of water/glycol solution at different temperatures Source : MEGlobal- Ethylene Glycol Product guide 13

14 Physical-chemical characteristics ph It s a key parameter. The corrosion inhibitors work better in the range of the ph from 7 to 9. Alluminum corrosion can occur at ph 9.5. Under ph 7 the corrosion risk is for cast iron, steel, copper and brass. Normally as a reference the ph of a solution at 33% or 50% of fluid in water is taken. Alcalinity reserve During the service life, the ph tends to decrease due to the formation of acid products such as glycolates.for this reason are used substances able to stabilize the ph. The alkalinity reserve represents the amount of 0.1 N hydrochloric acid required to titrate up to ph ml of a sample of coolant. Generally it is desirable that the alkalinity reserve has a high value 14

15 Physical-chemical characteristics Foam tendency The foaming fluids that can cause damage to the circuit Antifoams can help avoid the problem Compatibility with hard waters The coolants "ready to use" are diluted with demineralized water. The concentrates coolants are generally diluted with water by the user. The drinking water usually have a certain hardness due to the presence of calcium carbonate and magnesium. If the coolant is not compatible with the dilution water a precipitate can form and, in the worst cases, it can lead to the block of the system or to the breakage of the water pump. 15

16 Technological characteristics Glassware corrosion (ASTM D 1384) It evaluates the ability of a fluid to protect the metals present in the circuit. Test conditions: fluid at 33% in synthetic water (sodium sulfate, sodium chloride, sodium bicarbonate) Duration: 336 hours Temperature: 88 C Air flow: 100ml/min Simulated service (ASTM D 2570) It evaluates the ability of a fluid to protect the metals present in the circuit. Test conditions: fluid at 44% in synthetic water (sodium sulfate, sodium chloride, sodium bicarbonate) Duration: 1064 hours Temperature: 88 C Air flow: 100ml/min 16

17 Technological characteristics Cavitation of alluminum pump (ASTM D 2809) It evaluates the ability of the fluid to protect alluminum components of the circuit. Test conditions: fluid/synthetic water 1: 5 Duration: 100 hours Temperature: 113 C - Pressure: 103-kPa (15 psig) Synthetic water: sodium sulfate, sodium chloride, sodium bicarbonate Alluminum corrosion (ASTM D 4340) It evaluates the ability of a fluid to prevent corrosion of the cylinder heads made of aluminum alloy. Test conditions: fluid at 44% in synthetic water Duration: 168 hours Temperature: 135 C - Pressure: 193-kPa (28 psig) Synthetic water: sodium chloride Compatibility tests with rubbers They are required by the manufacturers. In Italy, CUNA NC , provide for the execution of the NC NC with test compounds UNI

18 Coolants composition and main categories of products Coolants categories Traditional based on Inorganic Additive Technology (IAT) Organic Acid Technology for LONG LIFE coolants (OAT) Hybrid Technology based on Traditional and OAT Technology (HOAT) 18

19 Coolants composition and main categories of products COOLANT COMPOSITION ready to use WATER GLYCOL or GLYCOL+GLYCEROL ADDITIVES ANTIFOAM AGENTS ADDITIVES for traditional and hybride products Na tetraborate, Na phosphate, Na nitrite, Na silicate, Benzotriazole and Na molybdate for metal protection (aluminum, steel, cast iron, copper and brass) Na benzoate for alkaline reserve ADDITIVES for new technology and hybride products Na sebacate Na azelate Na 2-ethyl esanoate 19

20 A brief history on coolants If we consider the heat transfer coefficient, the cost, the availability and the ecological aspect the best cooling fluid is water. But water has some limits: it can be used only in a narrow range of temperatures (0 C-100 C), it causes metals corrosion, produces deposits and fouling inside the circuits. In the 1930s the ethylene glycol (MEG) is introduced because, besides having an excellent behavior in cold conditions, it significantly raises the boiling point of water. From a toxicological point of view ethylene glycol is harmful if swallowed and products containig it must be labeled. Exhaust coolants must be collected for disposal. 20

21 A brief history on coolants Later the propylene glycol (MPG) was introduced because from a toxicological point of view is not harmful and the products are not labeled. But, as its cost is higher than that of ethylene glycol, nowadays the ethylene glycol remains the most widely used for coolants formulation. 21

22 MEG, MPG and Glycerol Glycerol was used as a heat transfer agent in coolant formulations as early as It was replaced by MEG in the 1930s due to cost considerations. Increases in the production of biodiesel since 2004 have produced a surplus in glycerol in the global market which has represented the possibility of a more cost-effective return of glycerol in coolants. Typically the purity grade of glycerol for coolant formulations is 99,5%. Nowdays many coolants manufturers use glycerol in their products. 22

23 MEG, MPG and GLYCEROL MEG Harmful-Lebeled OH HO MPG Non toxic to the environment OH OH HO GLYCEROL Non toxic to the environment OH OH 23

24 MEG, MPG and Glycerol In Italy, CUNA (Commissione Tecnica di Unificazione nell Autoveicolo), in 2007 established a Working Group in order to: evaluate the impact of glycerol in coolants formulations issue a new specification that takes into account the introduction of glycerol Several laboratory tests have been carried out in order to assess the possibility to introduce glycerol without affecting coolants physical-chemical and technological characteristics. The WG demonstrated that the introduction of glycerol up to 20% (by weight) has no negative impact on coolants performances. 24

25 MEG, MPG and GLYCEROL Mixtures of glycols and glicerol - Diluition: 50% vol. in water Mixtures composition, %w Ethylene glycol Proplylene glycol GLYCEROL Characteristics Method Experimental data Density at 15 C, g/cm 3 ASTM D ,07 1,039 1,146 1,089 1,059 Boiling point, C ASTM D Hard water compatibility NC clear clear clear clear clear Viscosity at 90 C, cst ASTM D 445 0,580 0,660 0,810 0,71 0,980 Viscosity at 0 C, cst ASTM D 445 4,500 10,50 17,00 5,700 20,60 Viscosity at -10 C, cst ASTM D 445 7,500 32,70 35,00 10,20 40,80 Freezing point, C ASTM D

26 MEG, MPG and GLYCEROL Ethylene glycol:glycerol 85:15 85:15 85:15 Traditional additives package X Glassware corrosion test (ASTM D 1384) Products composition, %w New technology additives package X Hybrid technology X Weight loss, mg/specimen Experimental data Specific values copper 0,7 0,9 0,8 10 max solder 9,6 0,9 0,9 30 max brass 0,6 0,6 0,6 10 max steel 0, max cast iron 1, max aluminum 0,1 2, max 26

27 Specifications In ITALY there are 2 standards issued by CUNA. NC (January 2012) MEG and/or MEG + GLYCEROL NC (December 1997) MPG These standards define the characteristics of a coolant soluble in water, based either on MEG and/or MEG + glycerol (20% maximum) and MPG with the addition of appropriate corrosion inhibitors, to be employed in the Cooling circuits of internal combustion engines. 27

28 Specifications Regulatory authorities The reference specifications are: ASTM (American Society for Testing and Materials) D Glycol base engine Coolant for Automobile and Light-Duty Service This specification covers the requirements for ethylene glycol or propylene glycol base engine coolants. Coolant type: ethylene glycol base concentrate, propylene glycol base concentrate, ethylene glycol base containing glycerin; ethylene glycol predilute (50%vol.), propylene glycol predilute (50%vol.),ethylene glycol containing glycerin predilute (50%vol.). This specification doesn t introduce a maximum % of glyceryn but it asserts that EG base coolant concentrates may contain glyceryn as long as physical, chemical and performance requirements of this specificationcan be meet. D Low Silicate Ethylene Glycol Base Engine Coolant for Heavy Duty Engines Requiring a Pre-Charge of Supplemental Coolant additive (SCA) New specifications after the introduction of glycerol: D Engine coolant grade glycerin D Glycerin engine coolant for automotive and light duty Service BRITISH STANDARD BS Specification for corrosion inhibiting, engine coolant concentrate ("antifreeze") JIS (Japanese Industrial Standard) K This Standard specifies the antifreeze coolants mainly composed of ethylene glycol, which are employed for prevention of freezing of cooling liquid used in a liquid-cooled internal combustion engine and for corrosion prevention of the cooling system. AFNOR NF R15-601(1991) Road vehicles. Cooling fluids. General specifications and requirements. 28

29 Conclusions The required characteristics for a coolant are: excellent heat exchange capacity protection against corrosion / cavitation ability to operate in conditions of extreme temperatures The introduction of glycerol doesn t influence coolants physical-chemical and technological characteristics. Nowadays a growing number of manufacturers use glycerol in coolants formulation. 29

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