1、 DEUTSCHE NORMJune 2004DIN 51726 ICS 75.160.10 Supersedes DIN 51726:1984-03 Testing of solid fuels Determination of the carbonate carbon dioxide content Prfung fester Brennstoffe Bestimmung des Gehaltes an Carbonat-Kohlenstoffdioxid Document comprises 9 pagesTranslation by DIN-Sprachendienst. In cas
2、e of doubt, the German-language original should be consulted as the authoritative text. No part of this translation may be reproduced without prior permission of DIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, has the exclusive right of sale for German Stan
3、dards (DIN-Normen). English price group 7 www.din.de www.beuth.de !,kTT“09.06 9724949DIN 51726:2004-06 2 Foreword This standard has been prepared by Technical Committee NMP 581/FABERG Prfung fester Brennstoffe of the Normenausschuss Materialprfung (Materials Testing Standards Committee) in collabora
4、tion with the Normenausschuss Bergbau (Mining Standards Committee). This standard specifies a method of separately determining the carbonate carbon dioxide content of solid fuels, whereas the elemental analysis specified in DIN 51721 yields only the total content of organically and inorganically bou
5、nd carbon. To determine the proportion of organically bound carbon, the carbonate carbon content is subtracted from the total carbon content. Amendments This standard differs from DIN 51726:1984-03 as follows: a) Gas washing bottles have been used instead of bulb tubes to absorb the carbon dioxide l
6、iberated. b) The test report has been included. c) The standard has been editorially revised and updated. Previous editions DIN 51726: 1955-05, 1984-03 1 Scope This standard specifies a method of determining the carbonate carbon dioxide content of hard coal, coke and brown coal (lignite). 2 Normativ
7、e references This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of
8、any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies (including amendments). DIN 1333, Presentation of numerical data DIN 12242-1, Conical ground joints on laboratory
9、glassware Dimensions and tolerances DIN 12481, Woulff bottles with bottom outlet for laboratory use DIN 12596, Drechsel gas washing bottles for laboratory use DIN 12700-5, Automatic zero burettes with reservoir (Pellet burettes) (superseded by DIN EN ISO 385) DIN 51701-2, Sampling of solid fuels Pro
10、cedure DIN 51701-3, Sampling of solid fuels Sample preparation DIN 51721, Determining the carbon and hydrogen content of solid fuels by the Rachmacher-Hoverath method DIN 51726:2004-06 3 DIN EN ISO 4259, Petroleum products Determination and application of precision data in relation to methods of tes
11、t (ISO 4259:1992 + Corr 1:1993) 3 Designation Designation of the method of determining the carbonate carbon dioxide content (C) of solid fuels: Method DIN 51726 C 4 Principle The carbon dioxide liberated by treating the fuel sample with hydrochloric acid is absorbed in solution and determined by tit
12、rating with hydrochloric acid. 5 Sampling and sample preparation As in DIN 51701-2 and DIN 51701-3. 6 Method 6.1 Apparatus In addition to standard laboratory equipment, the following shall be used. Decomposition flask (e.g. round bottom flask, of nominal capacity 250 ml, having a DIN 12242 NS 29/32
13、ground glass joint and fitted with a condenser and head-piece) (see figure 1). Absorption tower (see figure 1). Gas washing bottle without frit (e.g. shape A bottle as in DIN 12596). Gas washing bottles with frit of pore size 1 (e.g. bottles as in DIN 12596). Three neck flask (Woulff bottle) (e.g. t
14、hree neck flask as in DIN 12481). Suction pump. Class AS burette, of nominal capacity 50 ml, with 0,05 ml scale intervals (e.g. Pellet burette as in DIN 12700-5). One-mark bulb pipette, of nominal capacity 30 ml. Electrical heating jacket. DIN 51726:2004-06 4 Key 1 Gas washing bottle for acidified w
15、ater 2 CO2washing bottle with frit (pore size 1) for Ba(OH2) absorption solution 3 Safety washing bottle with frit (pore size 1) for absorption solution, for indicating complete precipitation Figure 1 Test set-up for volumetric determination of carbonate carbon dioxide content 6.2 Reagents Only anal
16、ytical grade reagents shall be used and the water used shall be distilled water or water deionized by ion exchange. Unless otherwise stated, solutions shall be prepared with distilled or deionized water. The following reagents shall be used. Decomposing acid, prepared by dissolving 10 g of mercury(I
17、I) chloride and 2 g of a wetting agent in about 485 ml of hydrochloric acid (density 1,16 g/ml) and making up to one litre. The mercury(II) chloride and wetting agent serve to bind hydrogen sulfide and to achieve complete wetting of the fuel sample. Absorption solution, prepared by dissolving 20 g o
18、f BaCl2 2 H2O and 4,5 g of NaOH in one litre of CO2-free water and filtering. Store this solution with carbon dioxide excluded. Before use, check that its titre is 0,1 mol/l by titrating with 0,1 mol/l hydrochloric acid using phenolphthalein as an indicator. 0,1 mol/l hydrochloric acid. CO2-free wat
19、er, prepared e.g. by decoction. Indicator, prepared by dissolving 0,1 g of phenolphthalein in 100 ml of 60 % ethanol. Sodium hydroxide on support. Acidified water for washing bottle 1, containing about 10 ml of concentrated sulfuric acid per 2,5 l of water. DIN 51726:2004-06 5 6.3 Preparation Assemb
20、le the apparatus shown in figure 1, ensuring that all the connections are airtight to prevent any air containing carbon dioxide from being sucked in. Before it enters the decomposition flask, purify the flushing air by passing it through an absorption tower filled with sodium hydroxide on a support.
21、 Fill the first washing bottle after the decomposition flask with water acidified with a few drops of sulfuric acid to remove any entrained hydrochloric acid vapours. NOTE It is advisable to perform the following steps prior to analysis at the start of every day. 1) Flush the empty assembled equipme
22、nt for about ten minutes (see subclause 6.4). 2) Pour 30 ml of absorption solution into each of the washbottles 2 and 3. 3) Perform at least two determinations of the effective titre. The effective titre is affected by the strength of the solutions, human errors (in reading the burette, pipetting, d
23、etermining the change in colour) and the equipment blank value (i.e. due to CO2-containing ambient air taken in every time the equipment is opened). 6.4 Procedure Weigh, to an accuracy of 0,2 mg, about 1 g of the air-dried analytical sample prepared as in DIN 51701-3 and having a particle size of le
24、ss than 0,2 mm into the decomposition flask. Connect the flask to the apparatus as shown in figure 1 and suck purified air through the equipment at a flowrate of about 150 ml/min using the suction pump. After the equipment (see note to subclause 6.3) has been flushed clear of air containing carbon d
25、ioxide, shut off the suction stream and pipette 30 ml of the absorption solution into gas washing bottle 3 and then the same amount into gas washing bottle 2. NOTE This order is preferred since the content of gas washing bottle 3 is not evaluated and this procedure prepares the pipette for the test
26、solution. After closing the washing bottles, switch the suction stream on again and suck about 50 ml of the decomposing acid out of the head-piece into the decomposition flask. Bring the contents of the flask to the boil and, after boiling for about ten minutes, suck purified air (free of carbon dio
27、xide) through for a further ten to fifteen minutes to transfer the liberated carbon dioxide quantitatively to the washing bottles. Only evaluate washing bottle 2, which is the actual reaction vessel. If a precipitate appears in the third washing bottle (amounts of absorption solution insufficient),
28、repeat the analysis with a smaller initial sample mass. After switching off the suction stream, open washing bottle 2. Wash the frit insert with CO2-free water and combine this water with the absorption solution. Add a few drops of indicator solution and titrate with 0,1 mol/l hydrochloric acid unti
29、l the solution is colourless. After every analysis, clean gas washing bottle 2 with dilute hydrochloric acid so that the frit always remains equally permeable, and then wash thoroughly with water. 6.5 Evaluation Calculate the carbonate carbon dioxide content of the fuel, w(CO2), as a percentage by m
30、ass (g/100 g) of the analytical sample using equation (1): ()( )mVVw1002002,0CO21moist2= (1) Calculate from this the content of inorganically bound carbon, w(Ca), as a percentage by mass using equation (2): DIN 51726:2004-06 6 w(Ca moist) = w(CO2 moist) 0,272 9 (2) Obtain the results for anhydrous f
31、uel by conversion using equations (3) and (4): ()( )AMww=100100COCOmoist2anh2(3) ()( )AMCwCw=100100moistaanha(4where, in equations (1) to (4), w(CO2) is the carbonate carbon dioxide content of the fuel, as a percentage by mass; w(Ca) is the inorganically bound carbon content of the fuel, as a percen
32、tage by mass; V1is the volume of 0,1 mol/l absorption solution taken, in ml; V2is the volume of 0,1 mol/l hydrochloric acid used, in ml; m is the initial mass of fuel with the moisture content at analysis (moist), in g; AM is the moisture content of the fuel, as a percentage; 0,002 2 is a conversion
33、 factor (1 ml of 0,1 mol/l absorption solution is equivalent to 0,002 2 g of carbon dioxide); 0,272 9 is a conversion factor (1 g of carbon dioxide contains 0,272 9 g of carbon). 7 Expression of results Refer to this standard and report the carbonate carbon dioxide content of the anhydrous fuel, w(C
34、O2 anh) as a percentage by mass to the nearest 0,01 %, taking DIN 1333 into account when rounding to the last significant place. 8 Precision (Cf. DIN EN ISO 4259) Repeatability limit (same operator, same equipment) If two results are obtained under repeatability conditions, both results shall be con
35、sidered as acceptable and in conformity with this standard if they differ by no more than 0,04 % absolute for a carbon dioxide content of 1 % or less or by no more than 4,0 % from the mean for a carbon dioxide content exceeding 1 %. Reproducibility limit (different operators, different equipment) If
36、 two separate laboratories each obtain a result under reproducibility conditions, both results shall be considered acceptable and in conformity with this standard if their means differ by no more than 0,08 % DIN 51726:2004-06 7 absolute for a carbon dioxide content of 1 % or less or by no more than
37、8,0 % from the mean for a carbon dioxide content exceeding 1 % (see Annex A). NOTE When comparing results, greater differences may be expected if the samples examined originate from the same bulk sample but have been obtained by division in a state other than analytically fine and the subsequent sam
38、ple preparation has been performed separately, or if the samples have been obtained by separately sampling the same batch. 9 Test report The test report shall include the following details as a minimum: a) Designation as specified in this standard (i.e. Method DIN 51726 C). b) Complete characterizat
39、ion of sample. c) The result expressed as specified in clause 7. d) Any unusual observations during the determination. DIN 51726:2004-06 8 Annex A (informative) Explanatory notes This standard is not in conformity with ISO 925. The latter specifies absorbing the liberated carbon dioxide on soda asbe
40、stos. At low levels of carbon dioxide, the mass absorbed is small compared with the mass of the absorption vessels, with the result that the precision is lower than that of the volumetric method described in this standard. DIN 51726:2004-06 9 Bibliography ISO 925:1997, Solid mineral fuels Determination of carbonate carbon content Gravimetric method Lange, W. and Winzen, W. Die Bestimmung des Carbonat-Kohlendioxidgehaltes fester Brennstoffe (Determining the carbonate carbon dioxide content of solid fuels), Glckauf, 1954: 90, 743744.
