1、 Thermal Conductivity Measurement Study of Refractory CastablesAPI PUBLICATION 935FIRST EDITION, SEPTEMBER 1999Thermal Conductivity Measurement Study of Refractory CastablesDownstream SegmentAPI PUBLICATION 935FIRST EDITION, SEPTEMBER 1999SPECIAL NOTESAPI publications necessarily address problems of
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15、f theDownstream Segment, American Petroleum Institute, 1220 L Street, N.W., Washington,D.C. 20005.iiiCONTENTSPage1 EXECUTIVE SUMMARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16、. . . . . . . . . . . . . . . . . . . . . . . . . 13 TEST METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1 Water Calorimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2
17、Calorimeter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3 Hot Wire C 1113-90. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.4 Comparative Thermal Conductivity Tester . . . . . . . .
18、 . . . . . . . . . . . . . . . . . . . . . . 33.5 Furnace Panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 MATERIALS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
19、SAMPLE PREPARATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 DATA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 CONCLUSIONS . . . . . . . . . . . . . . . . . . .
20、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.1 Different Procedures Yield Different Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.2 Ascending Thermal Conductivity Curves Differ from Descending Thermal Conductivity Curves . . . . . . . . . . . . . .
21、. . . . . . . . . . . . . . . . . . . . . . . . . . 58 RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5APPENDIX ATHERMO-GRAVIMETRIC ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . 7FiguresA-1 Thermo-Gravimetric Analysis (T
22、GA) Cement Bonded Castable . . . . . . . . . . . . . . 9A-2A Dense (135 140 lb/ft3) Erosion-Resistant Castable, Ascending Thermal Activity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-2B Dense (135 140 lb/ft3) Erosion-Resistant Castable, Descending Thermal C
23、onductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-3A Dense (165 lb/ft3) Extreme Erosion-Resistant Castable, Ascending Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A-3B Dense (165 lb/ft3) Extreme Erosion-Resist
24、ant Castable, Descending Thermal Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A-4A Fused Silica Castable, Ascending Thermal Conductivity . . . . . . . . . . . . . . . . . . . 15A-4B Fused Silica Castable, Descending Thermal Conductivity . . . . . . . . . .
25、. . . . . . . . 15A-5A Lightweight (55 60 lb/ft3) Insulating Castable, Ascending Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17A-5B Lightweight (55 60 lb/ft3) Insulating Castable, Descending Thermal Conductivity. . . . . . . . . . . . . . . . . . .
26、. . . . . . . . . . . . . . . . . . 17A-6A Medium Weight (70 85 lb/ft3) Insulating Castable, Ascending Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19A-6B Medium Weight (70 85 lb/ft3) Insulating Castable, Descending Thermal Conductivity. . . . . . .
27、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19A-7A Moderate Density (100 120 lb/ft3) Moderate Erosion-Resistant, Castable Ascending Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-7B Moderate Density (100 120 lb/ft3) Moderate Erosion-Resistant,Cas
28、table Descending Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21vCONTENTSPageTablesA-1 Thermal Conductivity Dense (135 140 lb/ft3) Erosion-Resistant CastableBtu in./hr ft2F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29、 . . . . . 10A-2 Thermal Conductivity Dense (165 lb/ft3) Extreme Erosion-Resistant CastableBtu in./hr ft2F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-3 Thermal Conductivity Fused Silica Castable Btu in./hr ft2F . . . . . . . . . . . .
30、. . . 14 A-4 Thermal Conductivity Lightweight (55 60 lb/ft3) CastableBtu in./hr ft2F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-5 Thermal Conductivity Medium Weight (70 85 lb/ft3) Insulating Castable . . . . 18A-6 Thermal Conductivity
31、Moderate Density/Erosion Resistant Castable (110 lb/ft3) Btu in./hr ft2F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201Thermal Conductivity Measurement Study of Refractory Castables1 Executive SummaryThermal conductivity is a physical property that providesgu
32、idance in designing refractory systems for equipment inwhich heat loss and/or thermal behavior are important. Theaccuracy of reporting and understanding thermal conductivityis vital to developing the most cost effective, efficient, andreliable equipment.The refractory industry uses various methods f
33、or measur-ing and reporting thermal conductivity that contribute to con-fusion in interpreting thermal conductivity data. The presenceof chemically combined moisture in unfired castable massescomplicates the measurement of thermal conductivity. Themoisture contributes to higher thermal conductivity
34、valuesuntil it is removed. Improper removal of the moisture duringinitial heat-up can also contribute to incorrect thermal con-ductivity data.Temperatures associated with refining of petroleum prod-ucts are considerably lower than other industries such as steel,foundries, aluminum, etc. At low opera
35、ting temperatures(1000F 1400F), removal of chemically combined waterfrom refractory castable linings is incomplete, and castableproducts do not achieve the optimum thermal characteristics.Removal of chemically combined water is a function of tem-perature. The majority of chemically combined waterapp
36、roximately 70%is removed between 500F and 850F,with the remainder dissociating up to 1250F. This is illus-trated in a Thermo-Gravimetric Analysis (TGA), shown inAppendix A. Historically, thermal conductivity of castableswas represented as a single value. More representative multi-point curves were l
37、ater introduced as heat loss became moreimportant but captured data while cooling a specimen fired towithin 100F of its use limit. Data collected during cooling ofspecimens is classified as descending data.Thermal conductivity measured during initial heating ofspecimens is defined as ascending data
38、and produces signifi-cantly different data than descending data. Ascending dataprovides a more accurate representation of a products ther-mal conductivity for low temperature application typical inmost hydrocarbon processing industry (HPI) applications.A study was initiated to compare the thermal co
39、nductivitydeveloped by different measurement techniques and assessthe relationship between ascending and descending data. Thestudy was designed to evaluate six products in six laborato-ries with five measurement techniques. The castable productswere chosen to represent a specific category, including
40、: light-weight, medium weight, moderate erosion resistant, dense,dense-extreme erosion resistant, and fused silica castables.The study was designed to show differences in measurementtechniques and ascending and descending data. There was noattempt to rank, classify, or assign accuracy to each of the
41、measurement techniques. The study concluded that the different thermal conductivityprocedures/apparatuses yield very different results. Thermalconductivity of lightweight and medium weight insulatingcastables varied by 100%, depending on the measuring tech-nique. As density increased, differences in
42、 thermal conductiv-ity values attributed to measuring technique decreased butwere still significant. Test results also indicate that differencesin ascending and descending thermal conductivity data, forthe castables studies, are considerable and worthy of designconsideration.It is recommended that u
43、sers and designers utilize ascend-ing thermal conductivity curves (data) in designing refractorylining systems, where heat transfer is a major considerationfor applications below 1500F. It is also recommended thatusers and designers evaluate thermal conductivity data andthe method of measuring the d
44、ata before using the data indesigns when heat transfer and skin temperatures are impor-tant to successful equipment operation.2 IntroductionThermal conductivity is defined as the amount of heattransferred through a unit area of a material in a unit time,through a unit thickness, with a unit of tempe
45、rature differencebetween the surfaces of the two opposite sides.Thermal conductivity of refractory castables is difficult tomeasure accurately due to the presence of moisture (chemi-cally combined water) in the matrix. When heated the firsttime, cementitious castables expel water (dehydration) fromt
46、he hydrated cement. The moisture is responsible for affectingthe identification of heat flowing through the refractory mass.Manufacturers of refractory products use various measure-ment techniques to develop thermal conductivity of refractorycastables. The following list identifies commonly used pro
47、ce-dures.a. Water CalorimeterASTM C-201 apparatus; C-417procedure.b. CalorimeterPilkington Method.c. Hot Wire MethodASTM C-1113.d. Comparative Thermal Conductivity MethodDynatech.e. Panel Test.Each procedure addresses unique concerns about measur-ing thermal conductivity of unfired castable refracto
48、ries. This study was initiated to compare differences in the fivetest methods at six laboratories. The scope of the study waslimited to one set of data for each of six products. Therefore,numeric relationships and direct evaluations between the var-ious methods were not desired nor achieved.2 API PU
49、BLICATION935The study concentrated on products with high to moderatecement contents. These products have distinct thermal con-ductivity curves during initial heating (ascending) and cool-ing (descending). Low and No Cement products were notevaluated and may or may not follow the same trends devel-oped for the cementitious products.Cement bonded castables develop physical propertiesthrough proper hydration of the cement. Upon heating, thehydrated cement dehydrates as the chemically bonded waterdissociates from the calcium aluminate cement. Use ofTh
