1、 STD-IS0 8858-1-ENGL 1770 I 4851903 0878733 078 INTERNATIONAL STANDARD IS0 8858-1 :1990 TECHNICAL CORRIGENDUM 1 Published 2001 -04-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MDKCIYHAPOflHAR OPrA”3Al collecting agent: A reagent added to a pulp to bring about adhesion between solid parti- cles
2、and air bubbles. 3.2 flotation concentrate: The clean product recov- ered in froth flotation. 3.3 conditioning: The preparatory stage in the flotation process in which the reagents are brought into intimate contact with the solids of the pulp. 3.4 frother; frothing agent: A reagent used to con- trol
3、 the size and stability of the air bubbles in the flotation process. 3.5 froth flotation: A process for cleaning fine coal in which the coal, with the aid of a reagent or rea- gents, becomes attached to air bubbles in a liquid medium and floats as a froth. 3.6 pulp: A mixture of solid particles and
4、water. 1 IS0 BB58 PT*I 90 IS0 8858-1:1990(E) 3.7 flotation tailings: The reject from froth flotation cells. 4 Principle Mixing of a coal sample with water to form a sus- pension in the flotation cell. Addition of collector and frother and introduction of air. Separate recovery of the concentrate and
5、 tailings and determination of the yield and ash of each. NOTE 1 the flotation characteristics of the coal. The use of chemical additives or heat can affect 5 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equ va lent purity. 5.1 C
6、ollector, n-Dodecane. 5.2 Frother, Methyl so-butyl carbinol (MIBC), (4-MethyIpentan-2-01), 0,14 YO (V/V) aqueous sol- ution. 6 Apparatus The apparatus shall be a mechanical impeller type flotation machine (see figure 1) with the following specifications. 6.1 Flotation cell, manufactured from stainle
7、ss steel. Figure 2 shows the dimensions of the flotation cell. The capacity of the cell with the deflector block and impeller in place is approximately 3,5 litres. It has been shown that the results obtained from laboratory froth flotation tests are very dependent on the procedure used to remove the
8、 concentrate from the surface of the pulp. For this reason, a de- flector block manufactured from plastics material (see figure3) is used to guide the concentrate to a rectangular area in front of the impeller housing. The concentrate can then be removed by means of a scraper (see figure4) which is
9、designed to cover the full width of the cell to a constant depth. In order to establish the volume of pulp which can be contained in the flotation cell, the deflector block is fitted into the cell and water is added to the flotation cell to about 20 mm to 30 mm below the required pulp level. The imp
10、eller is started (air valve off) and additional water is added to the required mark (see 8.4). The impeller is stopped, the deflector block removed, and the volume of water in the flotation cell is measured. 2 Li851903 0095878 7 6.2 Impeller assembly, of stainless steel and capa- ble of rotation at
11、frequencies up to 1500 rev/min (equivalent to a speed of 5,7 m/s at the periphery). The dimensions of the impeller and diffuser are shown in figures 5 and 6. The lower face of the impeller shall be positioned no more than 5 mm from the base of the cell. NOTE 2 Impellers constructed of other material
12、s may be used, provided that it can be shown that the charac- teristics of flotation for the cell are similar to those ob- tained when a stainless steel impeller is used. To achieve this, different impeller rotational frequencies may be used if necessary. 6.3 Constant level control, maintaining the
13、level of the pulp in the cell during the flotation test. 6.4 Scraper, of the design shown in figure4. Its clearance at the sides of the cell shall be minimal and should not exceed 2 mm. The scraper shall be of such dimensions that it clears the pulp level (as defined in 8.4) by not more than 2 mm. 6
14、.5 Calibrated micro-syringe, for the addition of the collector (5.1). 6.6 Pipette, of capacity 25 ml, complying with IS0 648, for the addition of the frother solution (5.2). 6.7 Timlng device, accurate to 1 s and capable of being zeroed and started as required. 6.8 Test sieves, complying with IS0 56
15、5, for the particle size analysis of the feed. 7 Sampling The history and method of preparation of samples can affect considerably the flotation characteristics of the coal. The origin of the sample should be re- corded and care should be taken to ensure that samples for comparison purposes are prep
16、ared in a similar manner. Since repeat tests are required together with sub-sampling for particle size and moisture determination, great care should be taken in mixing and subdivision of the original sample. Where applicable, all sampling and subdivision of samples should be carried out in accordanc
17、e with the procedures specified in IC0 1988. The quantity of gross sample required is at least five times the quantity required for a single flotation test. The latter quantity can be determined by reference to 8.3. Where the sample for flotation testing is obtained in pulp (or slurry) form, it will
18、 be necessary to separate the solids from the water before the procedures laid down in this part of IS0 8858 can be applied. Dewa- tering shall be by natural settlement followed by IS0 8858 PT*3 70 W 4853703 0095879 7 IS0 8858-1 :I 990(E) decantation and filtration. No chemicals or heat shall be use
19、d in the dewatering process as they may af- fect the surface properties of the materials and change their flotation characteristics. The results of the flotation test are influenced by the particle size and a complete particle size analysis of the coal, carried out according to IS0 1953, should be r
20、eported (see annex A), A sub-sample should also be retained for the determination of ash and other parameters as required (see 9.2). 8 Flotation conditions 8.1 Operating temperature The operating temperature shall be 25 “C & 10 “C. 8.2 Water Water complying with clause 5 shall be used. 8.3 Solids co
21、ntent The solids content of the sample to be tested shall be 100 g of solids (on a dry basis) per litre of pulp. For example, when the effective cell volume is 3,5 litres the sample mass is 350 g of dry solids plus any associated moisture as previously determined, see 9.1. 8.4 Pulp level The pulp le
22、vel shall be 20 mm f 2 mm below the overflow lip of the cell when the impeller is rotating at 1500 rev/min and the air is off. 8.5 Collector The quantity of collector (5.1) added shall be equiv- alent to 1 ml/kg of dry solids. For example, for a cell volume of 3,5 litres, a volume of 0,35 ml of coll
23、ector will be required. 8.6 Frother The quantity of frother (5.2) to be added shall be 0,l ml of MIBC per kilogram of dry solids. For ex- ample, for a cell volume of 3,5 litres, a volume of 25 ml of the solution (5.2) will be required. 8.7 Air flow rate The air flow rate shall be 4 Ilmin f 0,4 I/min
24、. It is recommended that this flow rate be controlled by the use of a needle valve and measured by means of a flowmeter, and that a separate on/off valve be provided. 9 Procedure 9.1 From a representative sub-sample, determine the moisture content and ash percentage of the coal sample (clause 7) by
25、the procedures specified in IS0 331 and IS0 1171 respectively. Calculate the mass of coal required for the flotation test from the measured cell volume (6.1) and the specified solids content of the sample to be tested (8.3). 9.2 From the coal sample (clause 7), take repre- sentative sub-samples of a
26、ppropriate mass for par- ticle size analysis (and determination of other parameters as required), and for the individual flotation tests. NOTE 3 External factors such as exposure of a coal sample to heat or prolonged exposure to atmosphere can severely affect the flotation characteristics of coal. I
27、n or- der to asses the reliability and repeatability of flotation tests, at least one repeat test should be carried out on any one coal sample. 9.3 Gradually transfer a flotation test sub-sample into the cell containhg 1 O00 ml of water, with the impeller rotating at 1 O00 revlmin and the air inlet
28、closed. Mix for 2 min, slowly add more water and increase the rotational frequency until the required level and a frequency of 1500 rev/min are reached. Agitate for a further 2 min. NOTE 4 The purpose of this procedure is to ensure thorough wetting of the sample. Variations in nominated conditions a
29、re permissible. 9.4 Add the collector (5,1), beneath the surface of the pulp by means of a calibrated micro-syringe (6.5) and start the timing device. Condition for 1 min, then add the frother solution (5.2) beneath the sur- face of the pulp using a pipette (6.6). Open the air valve affer an additio
30、nal 10 c of conditioning. Open the tap connecting the cell to the constant level control as concentrate is removed. NOTE 5 A significant amount of floated coal may adhere to the sides of the cell above the water level. Since this coal has been floated it should be washed back into the concentrate so
31、 that it may be removed from the cell by the scraper. A minimal amount of water should be used. 9.5 Every 25 s move the scraper through the con- centrate and collect a froth increment. The recessed edge of the scraper shall rest on the top edge of the cell and the movement of the scraper should be gradual, to ensure that pulp is not collected with the froth. 9.6 Collect the total froth produced over a period of 3 min frothing time. 3
