BS/EN 14582-2016 pdf download.Characterization of waste Halogen and sulfur content Oxygen combustion in closed systems and determination methods.
NOTE 2 The ascorbic acid and large amount of nitrate may interfere with early eluting halogens (fluoride, chloride and bromide) if detected by ion chromatography.
The determination of recoveries of halogen and sulfur from control mixtures mentioned in Table 1 is presented in Annex C. in order to show the possible use and combination between absorption solutions and different analytical methods.
10.3 Preparation of the bomb
The bomb is prepared according to the manufacturer’s instructions and the free ends of the firing wire (9.3) attached to the electric terminals of the ignition circuit (9.4). If using an absorption solution inside the bomb, add 10 ml of the chosen absorption solution (see 10.2), wetting the sides of the bomb (9.1).
The sample cup should not be in contact with the absorption solution. Depending on the bomb design and/or the expected concentration range of the analytes of interest, it may be necessary to adapt the amount of the absorption solution or trap the combustion gases in an external absorption flask (see
9.5).
10.4 Combustion
0.05 g to I g of sample, depending on its calorific value, the amount of element present and on the determination method, is weighed (to the nearest 0.1 mg) into the sample cup (9.2). Samples that burn with difficulty (e.g. mineral samples or samples with high water content). may require the addition of a combustion enhancer (7.1.9). Liquid samples may be weighed in a capsule (7.1.11). To avoid swirling up of the sample when filling the bomb with oxygen, powdery samples may be covered with inert material (e.g. aluminium oxide (7.1.10)) or soaked with combustion enhancer (7.1.9), depending of their calorific value. Powdery samples with low density and that burn very readily may be pressed into a pellet before combustion, to avoid material to be flung out of the crucible.
Depending on the type of the bomb, the total sample mass plus enhancer should not exceed 1 g to 1.5 g to avoid dangerous high pressure and possible rupturing the bomb.
NOTE 1 The combined energy from sample and enhancer is not important to recover halogens and sulfur from the sample compounds. Hence it may be necessary to optimize the enhancer/sample amount ratio.
Place the sample cup in position and arrange the firing wire (9.3) so that it will be just in contact with the sample but not touching the sample cup (9.2).
NOTE 2 Some operators use nylon thread or cotton wick and ioop it around the wire so that its ends immerse directly In the liquid sample or are In contact with the solid sample.
Assemble the bomb and tighten the cover securely. Admit oxygen (7.1.8) carefully (to avoid blowing the sample from the cup) to a pressure below the safety pressure specified by the manufacturer.
In case nitrates produced during the oxidation of the nitrogen of the air contained in the bomb interfere during the analytical determination, this ambient air should be eliminated by vacuum depletion or by flushing the bomb with oxygen.
Connect the terminals to the open electrical circuit. Close the circuit to ignite the sample. After the combustion is complete, let the bomb cool to ambient temperature, e.g. in a water bath.
10.5 Collection of the halides and sulphate
When relatively high levels of halogens and sulfur (e.g. over 20 g/kg) are expected, and/or when there is no absorption solution inside the bomb, connect the exit of the bomb to an absorption flask (9.5) filled with 20 ml of the same absorption solution used in 10.3 and release the pressure at a slow, uniform rate so that only small bubbles are observed in the absorption tube.
When relatively low levels of halogens and sulfur are expected, less volume could be used inside the bomb and the combustion gas shall be also collected in an external absorption solution (the same as used in 10.3); less volume (e.g. 10 ml) could be used in the collection flask in order to limit the dilution effect on halides and sulphate.
If high levels of halogen and sulfur are expected, it is highly recommended to measure a blank value between the samples.
NOTE 1 The volume of the absorption solution depends on the type and volume of the absorption flask.
Open the bomb and examine the content:
— If traces of sooty deposits are found, discard the determination and repeat again with combustion enhancer and/or with a smaller test portion;
— If pink vapours are seen, discard the determination and repeat using precautions to trap all the iodine (e.g. smaller test portion, addition of ascorbic acid).
Rinse the interior of the bomb, terminals, inner surface of the bomb cover and the sample cup thoroughly with solution from the absorption flask or 20 ml of the same absorption solution used for the preparation of the bomb in 10.3.
NOTE 2 Some calorimetric bombs are connected to a demineralized water supply, which enables automatic rinsing of the bomb interior before opening. In this case, the rinsing water is pushed by weak overpressure out of the bomb and combined with the absorption solution.BS/EN 14582-2016 pdf download.