1、Reference number ISO 12988-1:2000(E) ISO 2000 INTERNATIONAL STANDARD ISO 12988-1 First edition 2000-05-01 Carbonaceous materials used in the production of aluminium Baked anodes Determination of the reactivity to carbon dioxide Part 1: Loss in mass method Produits carbons utiliss pour la production
2、de laluminium Anodes cuites Dtermination de la ractivit au dioxyde de carbone Partie 1: Mthode par perte de masseISO 12988-1:2000(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unl
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7、d in Switzerland ii ISO 2000 All rights reservedISO 12988-1:2000(E) ISO 2000 All rights reserved iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally
8、 carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the w
9、ork. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical
10、committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this part of ISO 12988 may be the subject of patent rights. I
11、SO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 12988-1 was prepared by Technical Committee ISO/TC 47, Chemistry, Subcommittee SC 7, Aluminium oxide, cryolite, aluminium fluoride, sodium fluoride, carbonaceous products for the aluminium indu
12、stry. ISO 12988 consists of the following parts, under the general title Carbonaceous materials used in the production of aluminium Baked anodes Determination of the reactivity to carbon dioxide: Part 1: Loss in mass method A thermogravimetric method will be the subject of a future part 2 to ISO 129
13、88.ISO 12988-1:2000(E) iv ISO 2000 All rights reserved Introduction Carbon reacts with carbon dioxide according to the following equation: CC O 2 C O 2 The loss of anode material from reaction with CO 2 under certain constant conditions, as well as the mass of the remaining specimen and of the dust
14、resulting from selective burning, are of importance in predicting the behaviour of the anodes in the electrolysis cell.INTERNATIONAL STANDARD ISO 12988-1:2000(E) ISO 2000 All rights reserved 1 Carbonaceous materials used in the production of aluminium Baked anodes Determination of the reactivity to
15、carbon dioxide Part 1: Loss in mass method 1 Scope This part of ISO 12988 specifies a loss in mass method for the determination of the reactivity of carbonaceous products to carbon dioxide. This method was developed especially for baked anodes used in the production of aluminium. 2 Normative referen
16、ces The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of ISO 12988. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this part
17、of ISO 12988 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid Internati
18、onal Standards. ISO 8007-2:1999, Carbonaceous materials used in the production of aluminium Sampling plans and sampling from individual units Part 2: Prebaked anodes. IEC 60584-2, Thermocouples Part 2: Tolerances. 3P r i n c i p l e A baked test cylinder is placed in a furnace purged with carbon dio
19、xide, CO 2 , at a temperature of 960 C for 7 h. The loss in mass is determined and the dust produced is measured using a tumbling-apparatus. The residual body of the test cylinder, called the unreacted residue, is weighed and all results calculated in mass percent. 4 Reagent 4.1 Carbon dioxide,(CO 2
20、 ) having a minimum purity of 99,5 % by volume and impurities of N 2 Ar 0,5 % by volume, H 2 O 150 mg/m 3 .ISO 12988-1:2000(E) 2 ISO 2000 All rights reserved 5 Apparatus A diagram showing a typical apparatus in accordance with specifications is shown in Figure 1. Normal ordinary apparatus and in par
21、ticular the following: 5.1 Muffle furnace, having the dimensions given in Figure 2 with a vertical, single-zone tube ensuring good, vertical temperature distribution and capable of heating to a maximum temperature of at least 1 000 C as well as maintaining the temperature at (960 2) C. 5.2 Sample ho
22、lder, made of heat-resistant steel to support the two test specimens in the centre of the furnace with a collection plate incorporated for catching dust falling from the specimens. An appropriate test arrangement is shown in Figure 3. 5.3 Temperature controller, consisting of a two-point temperature
23、 PID controller with a set value adjuster (adjustment error 0,5 %) and with a digital temperature display. 5.4 Gas-flow meter and pressure control, consisting of a gas-flow meter calibrated for CO 2 gas and a manometer. The CO 2 gas-flow meter (p = 0,1 MPa) having a full-scale flow rate of 250 l/h,
24、shall be accurate to 4 %. The gas pressure is adjusted using a valve to obtain the regular value, 0,2 MPa, which shall be controlled by a manometer. The full scale of the manometer shall be 0 MPa to 1 MPa. It shall be capable of introducing CO 2 into the muffle furnace and of keeping the gas-flow co
25、nstant by less than 3 % for the duration of the test. 5.5 Thermocouple, chromel-alumel, K-type, accurate to better than 0,75 % in accordance with IEC 60584-2, having a 2,8 mm diameter with a minimum length of 400 mm. The distance between the upper surface of the anode and the thermocouple shield sha
26、ll be (10 0,5) mm. 5.6 Alumina tube, covering the gas inlet tube (see Figure 1) at the bottom of the furnace and for preheating the gas. 5.7 Tumbling-apparatus, having the following components and assembled as shown in Figure 4. 5.7.1 Electric motor, 90 r/min, 220 V or 110 V, 50/60 Hz. 5.7.2 Two ste
27、el cylindrical chambers, with the following dimensions: internal diameter: 68 mm; internal height: 120 mm. 5.7.3 50 steel balls, per chamber (5.7.2), of approximately 6 mm diameter. 5.7.4 Sieve, of 4 mm aperture and pan.ISO 12988-1:2000(E) ISO 2000 All rights reserved 3 Key 1 Thermocouple 2 Test spe
28、cimen 3 Preheater with alumina tube Figure 1 Schema of apparatus assemblyISO 12988-1:2000(E) 4 ISO 2000 All rights reserved Dimensions in millimetres Figure 2 Dimensions of typical muffle furnaceISO 12988-1:2000(E) ISO 2000 All rights reserved 5 Dimensions in millimetres Figure 3 Example of an arran
29、gement for the determination of the reactivity of the anodes to CO 2ISO 12988-1:2000(E) 6 ISO 2000 All rights reserved Dimensions in millimetres Key 1 Chamber 2 Motor 3S i e v e Figure 4 Tumbling-apparatus for determining the amount of dust producedISO 12988-1:2000(E) ISO 2000 All rights reserved 7
30、6 Sampling When the test specimens (or cores) are to be extracted from a larger body, sampling shall be carried out in accordance with the procedure specified in ISO 8007-2. Alternatively, samples may be prepared in the laboratory by a bench-scale procedure. 7 Preparation of test specimens Prepare t
31、wo test specimens each with a core diameter of (50 1) mm and a length of (60 1) mm. Dry the specimens at (120 5) C for 12 h and cool to room temperature. 8 Procedure Determine the initial mass of each test specimen by weighing each one (cores) (m 0 ) to 0,1 g. Heat the muffle furnace (5.1) to (960 2
32、) C. Maintain the furnace at this temperature for at least 60 min to allow the temperature to stabilize, open the furnace, insert the test specimens and close the furnace. Start the gas flow of CO 2 and adjust the flow rate (see 5.4) through the alumina tube (5.6) to 200 l/h. Maintain the furnace at
33、 960 C and the gas flow at 200 l/h for 7 h. After 7 h, switch off the furnace and after an additional 2 h cooling, switch off the gas flow. Once the temperature of the furnace falls below 550 C, remove the residual body of the test specimen and the dust produced. Allow the residual body of the test
34、specimen (cores) and the dust to cool to room temperature and weigh them (m 1 ) to the nearest 0,1 g. Place each residual test specimen (core) in a separate chamber (5.7.2) of the tumbling- apparatus with 50 steel balls (5.7.3) and allow them to tumble for 20 min to remove any loose particles. Once
35、the tumbling has been completed, empty the chamber into the 4 mm sieve (5.7.4), remove the balls, then weigh the residual bodies of the test specimens (cores) to the nearest 0,1 g (m 2 ). 9 Expression of results Determine the reactivity-to-CO 2 parameters, w RC (residue, dust and loss), expressed as
36、 a percentage by mass, using the following formulae: Residue, w RCR : w RCR = m m 2 0 100 Dust, w RCD : w RCD = mm m 1 2 0 100 Loss, w RCL : w RCL = mm m 01 0 100 where m 0 is the initial mass, expressed in grams, of the test specimen (core); m 1 is the mass, expressed in grams, of the residual test
37、 specimen (core) and dust; m 2 is the mass, expressed in grams, of the residual test specimen (core) after tumbling. Report the result to 0,1 g.ISO 12988-1:2000(E) 8 ISO 2000 All rights reserved 10 Precision 10.1 Repeatability The repeatability of the test depends strongly on the homogeneity of the
38、tested cores and is therefore difficult to assess. 10.2 Reproducibility In 1993, samples were tested in over 20 laboratories which has allowed an estimate of the reproducibility, R,o ft h et e s t to be made (see Figure 5) as a function of the level of the reactivity-to-CO 2 . These reproducibility
39、figures can be used when the average of at least 30 cores is determined to characterize a given electrode population. 11 Test report The test report shall include the following information: a) an identification of the sample; b) the method used with reference to this part of ISO 12988, i.e. 12988-1:
40、1999; c) the method of sample preparation. d) the date of the test; e) the results and the method of expression used; f) any unusual features noted during the determination; g) any operation not included in this part of ISO 12988 or in the International Standard or in the International Standards to
41、which reference is made, or regarded as optional;ISO 12988-1:2000(E) ISO 2000 All rights reserved 9 a) Estimated reproducibility R RCR as a function of w RCR (reactivity-to-CO 2 parameter for residue) b) Estimated reproducibility R RCD as a function of w RCD (reactivity-to-CO 2 parameter for dust) c) Estimated reproducibility R RCL as a function of w RCL (reactivity-to-CO 2 parameter for loss) Figure 5 Estimated reproducibility, R RC , as a function of the reactivity-to-CO 2 parameter, w RCISO 12988-1:2000(E) ICS 71.100.10 Price based on 9 pages ISO 2000 All rights reserved
