1、 Reference number ISO 20905:2004(E) ISO 2004INTERNATIONAL STANDARD ISO 20905 First edition 2004-07-15 Coal preparation Determination of dust/moisture relationship for coal Prparation du charbon Dtermination de la relation particules/humidit du charbon ISO 20905:2004(E) PDF disclaimer This PDF file m
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6、yright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2004 All rights reservedISO 20905:2004(E) ISO 2004 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normativ
7、e references. 1 3 Terms and definitions. 1 4 Safety 1 5 Apparatus and equipment 2 6 Reagent 2 7 Sample Initial 2 8 Sample preparation Initial 3 8.1 Initial total moisture 3 8.2 Moisture adjustment. 3 9 Sample preparation Reagent. 4 10 Dust determination. 5 10.1 Environment and equipment checks 5 10.
8、2 Dust testing. 5 11 Calculation. 6 12 Report. 6 13 Precision 6 Annex A (informative) Worked example. 7 Annex B (informative) Worksheet example 11 ISO 20905:2004(E) iv ISO 2004 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national
9、standards bodies (ISO member bodies). The work of preparing International Standards is normally 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
10、 organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules g
11、iven in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at leas
12、t 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 20905 was prepared by Technical Committee ISO/TC 27,
13、Solid mineral fuels, Subcommittee SC 1, Coal preparation: Terminology and performance. ISO 20905:2004(E) ISO 2004 All rights reserved vIntroduction The development of the dust/moisture curve provides an indication of the likely response of different coal types to drying or water addition during mini
14、ng and handling processes. The dust/moisture curve provides a good basis for comparing the response of different coal types. Understanding the dust/moisture characteristics of a coal will allow minimized water addition to the product for dust suppression. This will in turn assist in water conservati
15、on at mines and other handling facilities, as well as minimizing the total moisture of the product. This International Standard describes a reliable measurement of dustiness of coal and extends to cover the relationship between dust and total moisture utilizing the Rio Tinto Dust Tumbler Test. This
16、test provides a quantitative measure of the dustiness of a coal that can be used to predict operational dust problems, and is also suitable for the assessment of dust suppression chemicals. The Rio Tinto Dust Tumbler Test was developed using rotating equipment in a controlled temperature and humidit
17、y environment, and uses a stream of air to remove particles which become airborne during the tumbling process. It is a batch test in which dust particles ( 150 m particles) are collected in a pre-weighed filter bag and weighed. From this mass, a dust number, calculated as the mass yield of dust mult
18、iplied by 100 000, is determined for the test total moisture. Only 1 kg of sample is required for each dust test, but eight sample lots are required to develop the dust/moisture curve for a particular coal, i.e. approximately 10 kg is required for each coal type. This dust test can be repeated with
19、subsamples at different coal total moisture levels to develop a dust/moisture curve. The slope of the curve provides information on how sensitive the dustiness is to changes in total moisture and a dust number of 10 has been used to provide a comparison between coals. The test has been successfully
20、used for several years on many coals and other bulk materials. The results have been correlated with the operating practice. The method has been applied to the evaluation of dust- control products, and the determination of dust-elimination total moisture requirements for coal-handling systems. INTER
21、NATIONAL STANDARD ISO 20905:2004(E) ISO 2004 All rights reserved 1Coal preparation Determination of dust/moisture relationship for coal 1 Scope This International Standard sets out a laboratory procedure for the dust testing of higher rank coals. The procedure defines a means of evaluating the dust/
22、moisture relationship characteristic of a coal and a dust extinction moisture (DEM). NOTE In this standard, an experimental dust number of 10 has been used in the example given in Annex A. 2 Normative references The following referenced documents are indispensable for the application of this documen
23、t. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 589, Hard coal Determination of total moisture ISO 1953, Hard coal Size analysis by sieving ISO 7886-1, Sterile hypodermic syringes f
24、or single use Part 1: Syringes for manual use 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 dust particles of 150 m or less diameter entrained in an air stream 3.2 dust extinction moisture DEM total moisture at which a dust number of 10 is
25、attained on the dust/moisture curve NOTE DEM is a useful point for comparing different coals and the effectiveness of reagents. 4 Safety The following safety precautions shall be observed. a) To prevent nitrogen build-up within the laboratory, the exhaust tube of the minimum-free-space oven shall re
26、main clear of obstruction. b) Safety glasses shall be worn at all times. ISO 20905:2004(E) 2 ISO 2004 All rights reservedc) The exhaust tube of the minimum-head-space oven shall remain free of obstruction to prevent nitrogen build-up within the laboratory. d) A dust mask shall be worn when handling
27、coal. e) Cloth or leather gloves shall be worn when using ovens. f) The hazards associated with a reagent shall be determined prior to use. Instructions on all relevant Material Safety Data Sheets (MSDS) shall be followed. 5 Apparatus and equipment The following apparatus and equipment is required.
28、5.1 Humidity- and temperature-controlled laboratory, with relative humidity of 63 2 % and temperature of 20 2 C. 5.2 Dust-test apparatus, having a rotating drum of 30 cm diameter and 30 cm effective length, as shown in Figure 1. The required drum speed is 29 r/min, and the desired airflow through th
29、e drum is 175 L/min. 5.3 Double filter bags, single use only. 5.4 Electronic thermohydrograph. 5.5 Tachometer. 5.6 Laminar flow differential-pressure manometer. 5.7 Stopwatch. 5.8 Capped bottles, of capacity 250 mL, wide mouth, polypropylene. 5.9 Top loading balance, having a minimum capacity of 1 g
30、 and readable to the nearest 0,01 g. 5.10 Laboratory trays. 5.11 Minimum-free-space drying oven. 6 Reagent Tap water is used in solution and sample preparation. 7 Sample Initial Before testing, remove the particles greater than 6,3 mm. Do not crush and replace this removed fraction as the samples pa
31、rticle size distribution will be altered. Prepare sufficient sample to provide 1,2 kg for each dust determination over the desired range of total moisture or reagent concentrations as well as 1,2 kg for sample characterization. Approximately 8 subsamples, at a range of total moisture, are required t
32、o develop a dust/moisture relationship. Once the sample has been screened, it shall be representatively split down to approximately 1,2 kg portions which are then heat-sealed in plastic bags and labelled. One of the 1,2 kg portions is used to determine the samples total moisture content (initial tot
33、al moisture), particle size distribution as specified in ISO 1953, and other relevant characteristics. The experimental details relating to these properties shall be recorded and retained. ISO 20905:2004(E) ISO 2004 All rights reserved 3Dimensions in millimetres Key 1 rubber seal 7 blower 2 rotating
34、 drum 8 muffler 3 drive unit, 30 r/min 9 valve 4 sealed compartment with hinged lid for bag access 10 flowmeter, 170 L/min 5 25 mm flexible hose 11 lifters 7 mm wide, 6 mm high 6 vacuum bag 12 intake Figure 1 Dust-test apparatus 8 Sample preparation Initial 8.1 Initial total moisture Determine the i
35、nitial total moisture (M 1 ) of the sample using a subsample of the extra 1,2 kg lot, as specified in ISO 589. 8.2 Moisture adjustment Samples are moisture adjusted to a range of total moisture contents at approximately 1 % moisture intervals. Adjust the total moisture of each of the 1,2 kg subsampl
36、es to the required level for dust testing via the following processes. ISO 20905:2004(E) 4 ISO 2004 All rights reserveda) For samples requiring total moisture levels greater than the initial total moisture, M 1 , water is added to the samples. Weigh the sample and calculate the mass of water require
37、d to achieve the required total moisture level using the equation below. Add the required mass of water via a spray bottle to the subsample in the plastic bag on an electronic balance. Reseal the bag and shake the bag to assist with water distribution. Leave the sample in the temperature- and humidi
38、ty-controlled room (5.1) for 24 h to equilibrate. Calculate the water addition, W a , required from the following equation: a21 Wmm = where 2 21 1 100 100 M mm M = where M 1 is the initial total moisture (as measured in 8.1), expressed as a percentage; M 2 is the required total moisture, expressed a
39、s a percentage; m 1 is the sample mass (at M 1 ), in grams; m 2is the sample mass (at M 2 ), in grams; W ais the water addition (or removal) required. b) For samples requiring total moisture levels less than the initial total moisture, M 1 , water is removed by low-temperature drying. It is importan
40、t that the material be evenly dried. Weigh the sample and calculate the mass of water loss required to achieve the required total moisture level, using the above equations. Place the sample in a tray in the controlled-environment laboratory and allow the sample to dry to the required mass. The tray
41、should be weighed periodically until the required mass of water is removed. Return the sample to the plastic bag, seal and leave to equilibrate for 24 h prior to dust testing. If the required mass loss cannot be achieved at the laboratory conditions, the sample may be dried to the required moisture
42、level in a 40 C oven, and then equilibrated in a sealed bag in the laboratory for 24 h. 9 Sample preparation Reagent Reagents can be added in addition to, or instead of, water. If the reagent is an aqueous solution, the coal sample is moisture adjusted such that the addition of reagent will increase
43、 the total moisture content to the target. Reagent doses are normally based on parts per million per mass of dry coal. The adjusting procedure should be as follows: a) Prepare the reagent according to the manufacturers instructions. b) Adjust the sample mass to just below total moisture required, us
44、ing one of the methods described in 8.2, allowing for any water addition associated with the reagent dosing. c) Scoop and brush coal into a mixer bowl and place in a mixer. d) Weigh the final moisture addition (reagent solution), into a clean syringe in accordance with ISO 7886-1. e) Run the mixer a
45、t low speed and start the stopwatch (5.7). Dribble the final moisture and reagent onto the coal over a period of 1 min, moving the syringe around while adding. f) After 2 min, stop the mixer. ISO 20905:2004(E) ISO 2004 All rights reserved 5g) Brush coal off the mixer blade and into the centre of the
46、 mixer bowl. h) Mix for a further 3 min. i) Scoop and brush the coal sample into a new labelled plastic bag, then heat-seal it. j) To allow the prepared sample to equilibrate, leave it in the heat-sealed bag for 24 h. The sample is then ready to dust test. 10 Dust determination 10.1 Environment and
47、equipment checks The following checks shall be undertaken: a) Ensure that the laboratory atmosphere is within the specified conditions by using the thermohydrograph (5.4). b) Ensure that the dust-test apparatus (5.2) is clean by blowing any residual particles from the piping and drum with compressed
48、 air. c) With an unused filter bag (5.3) in place, ensure that the correct quantity of air is passing through the drum. (The desired air flow is 175 L/min. This is approximately equivalent to 3,5 m/s or 12,6 km/h.) d) Ensure that the drum rotation speed is correct, using the tachometer (5.5) and adj
49、usting the motor position if necessary. The required drum speed is 29 r/min. WARNING Care must be taken when using compressed air for cleaning purposes. 10.2 Dust testing Complete the following for each moisture-adjusted 1,2 kg sample: a) Select a clean filter bag (5.3) that has been equilibrating at laboratory conditions for at least 24 h; label, record the mass on a worksheet to the nearest 0,01 g and place it in the dust-test apparatus (5.2). NOTE An example of a worksheet is given in Annex B. b)
