ISO 540:2008 pdf free download.Hard coal and coke-Determination of ash fusibility.
Introduction
The method for determination of the fusibity temperatures of coal ash and coke ash describea in ISO 540 provides information about the fusion and melting behaviour of the composite inorganic constituents of the ash at high temperatures. The standard method is based on the TMSeger Con& method, which is well known in the ceramic industry, the use of which predates the year 1900. The conditions of the test, as well as basic studies on the influence of ash chemistry and of gas composition on ash fusibility temperatures (which have led to the standardization of the method), arose from the pioneering work of Fieldner, Hall and Field [J.
In the laboratory, the ash used for the test is a homogeneous mixture prepared from a representative sample of the coal or coke, and the determination is performed at a controlled rate of heating in either a reducing or an oxidizing atmosphere. In contrast, under industrial conditions, the complex processes of combustion and fusion involve heterogeneous mixtures of particles, heating rates (that can be several orders of magnitude greater than those used in the standard test) and variable gas composition.
During the first quarter of the 20th century, laboratory, pilot-scale and field studies were undertaken to establish that the ash fusibility test can provide a reasonable indication of the propensity of ash to form fused deposits (referred to as clinker”) in stoker and other fuel-bed type furnaces (Nicholls and Selvig [2]). Subsequently, the test has been used as a general indicator of the tendency for ash to fuse on heating and of ash slagging propensity in pulverized coal-fired furnaces.
I Scope
ISO 540 specifies a method 01 determinrng the characteristic lueion temperatures of ash from coal and coke.
NOTE Deaa4ors: fossil fuels, solid fuels. ash, ashes, teats, high temperature tests. delemilnabon, and fusibility.
2 Normative references
The following referenced documents are indispensable for the application of ISO 540. For dated references, only the edition cited applies, For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1171. So4d mWera fuels — Deter ,ratio,, of ash
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
deformation temperature
DT
temperature at which the fist signs of rounding, due to melting. of the tip or edges of the test piece occur
NOTE Shflnkage or tetoillon of the test piece, or rounding of cmcs and fins. are n criteria for deformebon and ehoi.il be igeored if the tØ and edges remain aiwp. However, for some solid mineral hate, the temperature at whirSi the teal piece alwe age bens can be of interest and should be reported as a feature noted dwing the determination.
3.2
sphere temperature
ST
In the case of pyramidal and truncated-cone test pieces, the temperature at which the height is equal to the width of the base, and in the case cit cubical or cyindflcal test pieces, the temperature at which the edges of the test pieces become completely round with the height remaining unchanged
3.3
hemisphere temperature
HT
temperature at which the test piece forms approxinately a hemisphere, ie. when the height becomes equal to
half the base diameter
3.4
flow temperature
FT
temperature at which the ash melt is spread out over the supporting tile In a layer, the height of which Is
one-thid of the height of the test piece at the hemisphere temperature
4 Principle
A test piece made from the ash is heated under standard conditions and continuously observed. The temperatures at which characteristic changes of shape occur are recorded. The diaracteflatic temperatures are defined In Clause 3. (See also Figures 2, 3 and 4.)
Although the determination le usually performed in a reducing atmosphere, additional information can somettmes be obtained by performing a further determination in an oxidizing atmosphere. In general, the reducing atmosphere in 7.1 gives the lowest characteristic temperatures
5 Reagents
5.1 O.xtrln, lOOgfl solution.
Dissolve log of dextrin in 100 ml of water.
5.2 Petroleum j.lly
5.3 Gold wire, of diameter 0.5 mm or larger, or gold plate, of thickness 0.5mm to 1.0 mm. with a purity ol
99.99 % and a melting point of 1 064 C,
5.4 Nickel wire, of diameter 0.5 mm or target, or nickel plate, of thickness 0.5mm to 1,0 mm, with a purity
0199,9% and a melting point of 1 455 °C.
5.5 Palladium wire, of diameter 0,5mm or larger, or palladium plate. of thickness 0,5mm to 1,0mm with apufltyof99,9%andameltingpoanlofl 554°C.
5.6 Carbon dioxide.
5.7 Hydrogen or carbon monoxide
6 Apparatus
6.1 Furnace, electrically heated, which satisfies the following conditions.
a) It shall be capable of reaching the rnaxwnum temperature at which the properties of the ash are determined (a temperature of 1 500 °C or more can be required),
NOTE Some furnace, can have a pracilcat upper operataig Ianaralure. e.g. I 480 Ot 1 540 C, due to the type of heating elements used in their manufacture.
b) It shall provide an adequate zone of uniform temperature In which to heat the test piece(s).
C) It shall provide means of heating the lest piece(s) at a uniform rate from 815°C upwards.
d) It shall b. capable of maintaining the required test atmosphere (see 7.1) around the test piece(s).
e) It shall provide a means of observing the change of shape of the test piece(s) during heating.
It is recommended to provide a facility for inseiling, between the end window of the furnace arid the optical viewing insthanent, a piece of cobalt-blue or wilier ass to protect the retina of the operator from radiation emitted at elevated temperatures.
6.2 Pyrometer, comprised of a platrumlpiallnum-rhodlum thermocouple.
The thermocouple l positioned so that the thermo-juriction Is on the longitudinal axis ri the centre of the zone of uniform temperature.
6.3 Mould, of brass, stainless steel, or other suitable material, for preparing the test piece. (See example in Figure 1.)
6.4 Support for the test piece. of such a material that the support does not either become distorted or react with or absorb the ash during the determiialion. Supports of srntered akimina or fme-textured mullite are generay satisfactory, but dIfficulties can arise with inc*vldual ashes, in which case a non-absorbent witerface such as platinum loll can be used between the origwral support and the test piece.
6.5 Flowmeters, two, for measuring the components of the reducing gases (see 7.1); it Ii not necessary to measure the flow rate when using an oxidizing gas.
If the flowmeter contains a liquid, this liquid shall be a non-volatile oil.
6.6 Agate mortar and p.stle
6.7 Test sieve, of aperture 0,075 mm (or less) and diemeter of approximately either 100 mm or 200 mm,
complete with lid and receiver.
6.8 Optical Instrument, which enables the profile of the test p.ece to be observed ttwoi4lout the
determination.
The relative dimensions of the profile can be conveniently assessed by using a graticule.
Additional use of photographic equipment such as a camera or video equipment is optional but recommended.
7 Test conditions
7.1 Test atmosphere
The reducsig atmosphere is obtained by introducing into the furnace one of the following mixtures 01 gases at a minimum linear rate of flow past the test piece of 400 rnm?min, calculated at ambient room temperature: the rate Is not critical, provided that it Is sufficient to prevent any leakage of ier Into the furnace:
a) 55 volume % to 85 volume % carbon monoxide WIth 35 volume % to 45 volume % carbon dioxide: or
b) 45 volume % to 55 volume % hydrogen with 45 volume % to 55 volume % carbon dioxide
NOTE I I? a mIxture 04 COICO2 Is used to produce the reducing atmosphere. ensure that the contents we totally ned in accordance with manufacturer’s awfruclions and that the temperature of the cytinder is niasitalned above the cntical temperature whidi CO can Iquely and separate.
NOTE 2 Ashes itch in Won oadde can react erth any oxygen present In the Iwnace. reauling In poor repestabibty and reproducibilIty of characsenetc temperatures.
An oxidizing atmosphere is obtained with aw or carbon dioxide: the rate of flow is not critical.
WARNING — When using the reducing atmospheres given above, the gases emergIng from the furnace contain a proportIon of carbon monoxide. It Is essential, therefore, to ensure that these gases are vented to the outsIde atmosphere, pr.f.rably by means of a hood or an efficient fan system. It hydrogen is used in the reducing atmosphere, great care shall be taken to prevent an explosion occurring, by purging the furnace with carbon dioxide both prior to the Introduction of the hydrogen and after the hydrogen supply is shut off.
7.2 Shape of test piece
The test piece shall have sharp edges to facilitate observation.
The mass of the test piece shal be such as to ensure equalization of the temperature within the test body. Hence, dimensions that are too large shall be avoided.
8 Calibration check
Check the pyrometer regularly under routine test conditions by observation of the melting point of gold (53) and, if possible, the melting poInt of palladium (5.5). Test the reducing atmosphere by observing the melting point or nickel (5.4).
If the observed melting points for gold or palladium differ by more than 10 ‘C from the melting points given In 5.3 and 5.5. readjust or recalibrate
NOTE I An alternative to the observations of the melting pouts of gold and palladium Is to check th pyromeisr using a thermoooi4le canalled by a recogoazed reference taboralony or ealti a calibraton that — Thceable beck to a standard reterence orator
If the observed melting point for nickel differs by more than 10 C from the melting point given m 5.4. it can be due to oxidation of nickel caused by an insurnciently reducing atmosphere. Examine the apparatus for leakages, control the flow rate and the quality of the gases, and recheck the melting point of nickeL
NOTE 2 The correct melting point of nickel Is not a guarantee that th coniposlton ci U* reducing abnospeiere e correct, as the fusey Is not IilLety to be aflected until the deviations are considerable,
9 Preparation of the test piece
Prepare the ash according to the method specified in ISO 1171. Ensure that the inaneralion is complete.
Grind the asl In an agate mortar (66) until the maximum particle size Is less than 0.075 mm. To maximize the number of particles in the peak of the pyramid, gnnding to less than 0.063 mm is recommended.
Moisten a sufficient quantity of the prepared ash with dernineralized waler or, II necessary. with an adhesive dextrin solution (5.1). and make the mixture into a paste. To faalitate the removal of the test piece, the mould (6.3) may first be coated with a thin layer of petroleum jelly (5.2).
F the mould uniformly and completely with the prepared paste of ash so that the edges and li of the specimen are sharp, Allow the test piece to visuaCy dry before attempting to remove It from the mould. If the ash paste dries too quickly, C is acceptable to moisten it slightly with additional water or sdution
After removal, mount the specimen onto its support (64), using a thin layer of paste of the prepared ash to effect aThesion. taking care not to damage the tip or edges. The specimen(s) should be examined with the optical Instrument (68) and those that do not have sharp edges and tips should be discarded
Allow the test piece to dry, and remove any organic matter by heating the lest piece slowty up to a temperature of about 815 ‘C. If preferred, this preliminary heating may be performed in the furnace (6.1) used for the test
10 Procedure
Transfer the test piece on its support (8.4) to the furnace (6.1), and adjust the composition and flow rate of the atmosphere, taking Into account the warning In 7.1. To minimize the risk of explosion when a reducing atmosphere is used, purge the furnace with carbon dioxide before admitting hydrogen.
The specenen shall be posItioned on the tile so that, when inserted Into the furnace, Its vertical face is parallel to the longitudinal axis of the inspection opening. Further, the speamen shall be placed as dose as possible to the end of the thermocouple sheath. Ensure that the thermocouple is in the ooi’rect position.
Raise the temperature of the furnace to a point below the expected deformation temperature, so that the temperature interval between the paint and the expected temperature exceeds 150 C.
If using a camera or video camera, focus on the specimen so that all parts of the specimen(s) are in sharp focus for the duration of the test Adjust the focus If required durtng the test
After a period of 10 mm, raise the temperature at a uniform rate within the range of 3 C/mln to 7 °Cemm; for small test pieces, a rate up tolD CImin is satisfactory. Commence observing or photographing the specimen and recording shapes 81 intervals of temperature change not greater than 20 C untll the maxmai temperature of the furnace is reached or the flow temperature of the specimen has been altained
Record the lemperatures at wtiich the charectenstic changes of shape ocour. If the charactwsbc shapes for the specimen lee between two successive frames using photographic or video techniques, the temperature should be recorded as the average temperature of the two consecutive frames. With some ashes, difficulties can be encountered owing to such effects as blistering, distortion, shrinkage, swelling. non-wetting of the support (caused by high surface tension) and bursting of internal gas bubbles. In such cases, it is desirable to record these phenomena and possibly repeat the experiment using a different type of support.
Where photographic equipment is used, a standard gnd shall be placed over the viewing saeen to assist in interpretation of characteristic shapes.
If a hydrogendcarbon dioxide atmosphere is used, turn off the hrogen and continue the flow of carbon dioxide for at least 30s, and then turn off the carbon dioxide flow.
Remove the specimen and tile fran, the furnace, allow cooling, and examine for evidence of chemical reaction between the ash and tile, which can cause difficulties in obtaining the characteristic shapes.
Process any film and examine the negatives or transparencies at magnification equivalent to a minimum of 10 tImes the original specimen height Where films are used, results shal be based on the examination of negatives or transparencies. not of prints.
11 PrecisIon of the method
11.1 Repeatability limit
The resuits of independent duplicate determinations, performed on the same day in the same laboratory by the same operator using the same apparatus on the same preparation of ash, shall not differ by more than the values given in Table 1
11.2 ReproducIbility limit
The means of the results of duplicate determinations, performed in each of two different latioratories an representative portions taken from the same sample after the last stage of preparation as specified In ISO 1171. shall not differ by more than the values given In Table 1.
12 Test report
The test report &iaII contain the following information:
a) identification of the sample tested;
b) reference of the method used;
c) deformation temperatwe, rounded to the nearest 10 C;
d) sphere temperature, rounded to the nearest 10 C:
e) hemisphere temperature, rounded to the nearest 10 C:
1) flow temperalise, rounded to the nearest 10 C:
9) type of atmosphere used (reducing or oxidizing).
13 Precision statement
Vahdabon data used In the International Stctard was determined by an Inter-laboratory study carried out In October 2004, Nineteen laboratories participated, analyzing three ash samples and eight coal samples.