1、Designation: C831 98 (Reapproved 2017)1C831 18Standard Test Methods forResidual Carbon, Apparent Residual Carbon, and ApparentCarbon Yield in Coked Carbon-Containing Brick andShapes Shapes1This standard is issued under the fixed designation C831; the number immediately following the designation indi
2、cates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEFootnote 4 was removed editorially in November 2
3、017.1. Scope1.1 These test methods cover the determination of residual carbon content in carbon-bearing brick and shapes after a prescribedcoking treatment. They provide two procedures. The first procedure is based on the combustion of carbon and its measurement ascarbon dioxide. However, when using
4、 the first procedure for articles that contain silicon carbide or other carbides, no distinctionwill be made between carbon present in the form of a carbide and carbon present as elemental carbon. The second procedureprovides a method for calculating apparent residual carbon (on the basis of weight
5、loss after igniting the coked specimens),apparent carbonaceous material content, and apparent carbon yield. If the second procedure is used for brick or shapes that containmetallic additives or carbides, it must be recognized that there will be a weight gain associated with the oxidation of the meta
6、ls,or carbides, or both. Such a weight gain can change the results substantially, and this must be kept in mind when interpreting thedata.1.2 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for informationonly.1.3 This standard does not p
7、urport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.4 This international standa
8、rd was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Refere
9、nced Documents2.1 ASTM Standards:2D2906 Practice for Statements on Precision and Bias for Textiles (Withdrawn 2008)3E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves3. Significance and Use3.1 These test methods are designed for use with carbon-containing products. The residual carbon
10、 content of a cokedcarbon-containing brick or shape is an indication of how much carbon may be available, in service, to resist slag attack on, oroxidation loss of, that body. Apparent carbon yield gives an estimate of the relative efficiency of the total carbonaceous matter tobe retained as residua
11、l carbon.3.2 Residual carbon has a direct bearing on several properties of a pitch or resin containing refractory resin-containingrefractory, such as ignited porosity, density, strength, and thermal conductivity.3.3 These test methods are suitable for product development, manufacturing control, and
12、specification acceptance.1 These test methods are under the jurisdiction ofASTM Committee C08 on Refractories and are the direct responsibility of Subcommittee C08.04 on Chemical Behaviors.Current edition approved Nov. 1, 2017Feb. 1, 2018. Published November 2017February 2018. Originally approved in
13、 1976. Last previous edition approved in 2017 asC831 98 (2017).(2017)1. DOI: 10.1520/C0831-98R17E01.10.1520/C0831-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to
14、the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previou
15、s version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM Inter
16、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.4 These test methods are very sensitive to specimen size, coking rates, etc.; therefore, strict compliance with these testmethods is critical.3.5 Appreciable amounts of reducible components, such as Fe2O3
17、, will have a noticeable effect on the results. Thus, valuesobtained by these test methods will be different when brick removed from service is tested. This must be kept in mind whenattempting to use these test methods in an absolute sense.3.6 Oxidizable components such as metals and carbides can ha
18、ve a noticeable effect on the results. This must be kept in mindwhen using the second procedure, which is based on measuring weight loss after igniting the coked specimens.3.7 Testing of brick or shapes that contain magnesium metal presents special problems since this metal is highly volatile andsub
19、stantial amounts of the magnesium can be lost from the sample during the coking procedure. This must be kept in mind wheninterpreting the results of testing of brick that contains magnesium. In addition, magnesium can react readily with atmospherichumidity. This must be kept in mind when storing bri
20、ck that contains magnesium.4. Apparatus4.1 For Coking:4.1.1 Gas or Electric Furnace, with heating chamber capable of receiving the coking box shown in Fig. 1.NOTE 1Samples should not be subjected to thermal gradients greater than 40 F (22 C) during heatup. In electric furnaces with silicon carbidehe
21、ating elements, the length of the box should be parallel to these elements.4.1.2 Inner and Outer Box, stainless steel (or equivalent alloy), as shown in Figs. 1-3.FIG. 1 Outer Coking Box (Dimensions are in Inches)C831 1824.2 For CO2 Absorption:4.2.1 Laboratory Pulverizer, designed to provide a seale
22、d, dust-proof grinding chamber, and having a capacity of at least 50g of sample.4.2.2 Combustion-Tube Combustion Tube Furnace, capable of operating at 183 F1832 F (1000 C)4.2.3 CO2 Absorption Train, as described in Fig. 4.NOTE 2Commercial automatic and semi-automatic carbon determinators may replace
23、 the apparatus described in 4.2.2 and 4.2.3.4.3 The precision obtained with these instruments shall meet the requirements specified in Section 10.FIG. 2 Inner Coking BoxC831 1835. Preparation of Test Specimens5.1 This method assumes that the number of specimens tested will be a statistically valid s
24、ample of the entire lot of brick orshapes being evaluated. The exact number is usually arrived at by mutual agreement between parties concerned.5.2 Although sample brick from either the 412-in. (114-mm) or the 6-in. (152-mm) series may be tested, it is preferable to usethe larger size for the test.
25、Cut slices 1 6 132 in. (25 6 0.8 mm) in thickness perpendicular to the length at the mid-section of eachFIG. 3 Coking Box ArrangementFIG. 4 CO2 Absorption TrainC831 184sample brick or shape. As shown in Fig. 5, the nominal size of each slice shall be 1 by 3 by 6 in. (25 by 76 by 152 mm). The two1 by
26、 3-in. faces and the two 1 by 6-in. faces must be original surfaces.5.3 Test specimens may be cut wet or dry except for products capable of hydration, such as dolomite brick, which must be cutdry and stored in a dry container prior to coking.5.4 Specimens that are cut wet must be dried immediately w
27、ith a paper or cloth towel and flash dried. For pitch-impregnatedsamples, flash drying should be done at a sufficiently low temperature to avoid “weeping” of pitch from the pores of the brick.Drying can usually be done on a forced-air dryer at 220 F (105 C) by limiting exposure to 5 to 10 min. Repea
28、t if necessary. Thesedrying procedures are especially important for metal-containing brick because hydration of the metals can occur. Specimenscontaining a coating of pitch on uncut surfaces, as is typical of an impregnation process, must be scraped clean prior to drying.5.5 Weigh all specimens afte
29、r drying to constant weight (60.2 g), recording weight to the nearest 0.1 g. This weight is“as-received weight, A.” (This step may be omitted if residual carbon is to be determined by CO2 absorption, as indicated in 1.1.)6. Procedure for Coking6.1 Place the test specimens randomly into the inner box
30、, Fig. 2.NOTE 3Burned pitch-impregnated magnesite brick should not be coked with tempered, tar-bonded, or dolomite brick because of carbon pickup bythe impregnated samples and disruption of the bottom of tempered samples. Pitch-bonded, pitch-bonded tempered magnesite brick, and dolomite brickmay be
31、coked in the same box or coking run.NOTE 4The number of samples coked per run should be constant within a laboratory. Dummy uncoked samples consistent with Note 3 may be usedto fill any empty positions in the inner box.6.2 Place the inner box into the center of the outer box (Fig. 3), on the bottom
32、of which has first been placed a 12-in. (13-mm)slab of carbon, covered with a thin layer of dust-free metallurgical-grade coke breeze (No. 14 (1.40-mm) sieve size) (Note 5). Toensure that the coke breeze is free of moisture which could oxidize carbon during cooking,coking, dry the coke at 400 F (205
33、 C)for 24 h, and keep in a closed container at room temperature until needed.NOTE 5Detailed requirements for sieves are given in Specification E11.6.3 Place the thermocouple well into the center of the inner box and put the lid on the inner box. The thermocouple well mustbe long enough to extend abo
34、ve the cover of the outer box.6.4 Cover the inner box with metallurgical-grade coke breeze retained on a No. 14 sieve and place a loose-fitting lid over thecoke breeze (see Fig. 3). Pack the coke breeze between the edges of the lid and box.6.5 Place the coking box assembly (Fig. 3) into the furnace,
35、 and insert a calibrated thermocouple into the thermocouple well.6.6 Heat the furnace so that the thermocouple within the box registers 250 F (120 C) after the first hour, then heat the furnaceso that the box is heated at a rate of 400 6 20 F (220 6 11 C)h to 1800 6 20 F (980 6 11 C).6.7 Hold the te
36、mperature for 3 6 12 h, starting from the time 1780 F (970 C) is reached in the inner box.6.8 After completing the hold period, shut off the furnace and allow the coking box to cool naturally within the furnace.6.9 Remove the samples from the coking box after the box has cooled sufficiently to handl
37、e. After removing specimens fromthe inner box, clean by brushing carefully with a nylon or natural bristle brush to remove clinging particles. Then proceed to eitherof the two alternatives for analyzing the specimens.NOTE 6After each run, clean the muffle and the bottom carbon plate of any adhering
38、coke breeze.FIG. 5 Location of Test SpecimenC831 1856.10 Samples that contain dolomite or aluminum metal should be stored in a sealed container containing dessicant in the timeinterval between coking and measurement of carbon content. This is to prevent hydration of dolomite or aluminum carbide. The
39、aluminum carbide is formed by reaction between aluminum and carbon in the shape during the coking operation. Aluminumcarbide can react with a water source such as atmospheric humidity to form methane. Care should be taken since methane can bean explosion hazard.CO2 ABSORPTION (FIRST ALTERNATIVE PROC
40、EDURE)7. Preparation of Sample7.1 A sample consists of a single slice or multiple specimens of brick prepared as described in Sections 5 and 6.7.2 Crush the sample in a laboratory jaw crusher, or other impact-type crusher, to pass a No. 4 (4.75-mm) sieve (Note 5).Thoroughly mix the crushed sample an
41、d reduce to approximately 50 g by quartering or riffling.7.3 Place the sample in the laboratory pulverizer and grind to 100 % passing a No. 100 (150-m) sieve. This takesapproximately 90 to 100 s. Promptly transfer the ground sample to a suitable airtight container.NOTE 7Extreme care must be taken du
42、ring the entire sample preparation to avoid loss of carbon by segregation or dusting.About 60 % of the variancein this procedure is in this step.8. Procedure8.1 With the furnace at operating temperature, pass oxygen through the absorption train until the CO2 absorption bulb attainsconstant weight (u
43、sually 15 to 30 min).Adjust the oxygen pressure and flow rate to provide 120 to 150 bubbles per minute throughthe bubbling tower. Close the stopcock, remove the absorption bulb from the train, cool to room temperature, and weigh to thenearest 0.1 mg.8.2 Into a previously ignited combustion boat, wei
44、gh a 0.1 to 1.0 g 1.0-g sample to the nearest 0.1 mg. Return the weighed CO2absorption bulb to the train and open the stopcock. Then place the combustion boat with sample in the combustion tube andimmediately reseal the train. Adjust the flow of oxygen as before (8.1), heat the furnace to 1740 to 18
45、30 F (950 to 1000 C), andmaintain until the CO2 adsorption bulb attains constant weight (usually 45 to 60 min).8.3 Remove the absorption bulb from the train, close the stopcock, cool to room temperature, and reweigh. The increase inweight is the CO2 won from the sample by combustion of the carbon.9.
46、 Calculation and Report9.1 Calculate the percentage of residual carbon in the sample as follows:Residual carbon,%5wt of CO230.27293100wt of sample (1)9.2 Run the determinations in duplicate. Results shall not vary by more than 60.05 % stated in terms of the whole sample as100 %. If satisfactory chec
47、ks are not obtained, repeat the analysis in duplicate. Report at least two individual analyses per slice.10. Precision and Bias410.1 An interlaboratory study was conducted in 1970 using a nested experimental design wherein a composite of several sizesof magnesite grain and lampblack was mixed in acc
48、urately weighed proportions, divided into four samples, and sent to fourlaboratories for testing. Each laboratory split its sample into four specimens, ground them for analysis, and made two replicatedeterminations on each. The components of variance (Note 8) of the results given in terms of standar
49、d deviations were found tobe as follows:Carbon Content, %Grand mean 4.572Between laboratories (L) 0.0778Between laboratories (L) 0.0778Between samples (S 0.0987Between samples (S 0.0987Between replicates (R) 0.0161Between replicates (R) 0.0161NOTE 8A procedure for calculating precision is fully described in Practice D2906. There is no known means for determining the bias of these testmethods.10.2 On the basis of the components of variance in 10.1, we would expect two averages of an equal number of specimens testedby this te
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