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When do you need to measure HBr?
- Permit conditions. The environmental permit sets the emission limit value for HBr and how often it is to be checked. The ordinances and the BAT conclusions have no limit value of their own for HBr.
- Waste with brominated flame retardants, such as electronic waste and plastics: with good combustion the flame retardants decompose and form mainly HBr.
- Bromine for mercury capture: at waste incineration plants, bromide can be added to the waste or injected into the furnace to oxidise mercury. The bromine ends up in the flue gas.
- Chemical industry: the bromination of organic compounds gives HBr as a by-product, and the emission is regulated in the permit.
- Performance tests and troubleshooting: guarantee values for the flue gas cleaning, checks of the scrubber or the sorbent dosing when bromine-containing waste is received.
How the sampling train is built
The measuring principle is wet chemical absorption, and the equipment is the same as for HCl. The sample gas is drawn through a heated probe with a filter, which stops the particles, and then bubbles through two absorption bottles in a cooling bath, where the hydrogen bromide dissolves as bromide ions. An empty knock-out bottle catches splashes and a drying tower with silica gel dries the gas. After the valve, pump and flow meter, a dry gas meter with a thermometer measures the sample gas volume.
- 1. Probe with filter holder, heated
- 2. Absorption bottles with absorption solution, in a cooling bath
- 3. Knock-out bottle
- 4. Drying tower
- 5. Valve
- 6. Sampling pump
- 7. Flow meter
- 8. Gas meter
- 9. Thermometer at the gas meter
The absorption solution is deionised water, as in EN 1911. When HBr is sampled together with HF, 0.1 M sodium hydroxide is used instead, which binds chlorides, bromides and fluorides in the same solution. Everything the sample gas meets before the bottles is made of borosilicate glass, titanium or PTFE, not stainless steel, and the probe and filter are kept at least 20 °C above the dew point of the flue gas.
How is an HBr measurement done?
Measurement plan
The measurement site must meet EN 15259. In homogeneous flue gas one measurement point is enough; otherwise the sample is taken at several. Sampling time, flow and the amount of solution are chosen according to the concentration expected, so that the sample gives at least ten times the detection limit of the analysis.
Field blank and leak test
Before each measurement series, and at least once a day, a field blank is taken: the same handling as a sample, but without drawing flue gas through the equipment. Before each sub-sample the train is tested for leaks; the leak rate may be at most 2 % of the sample gas flow.
Sampling
The probe and filter are heated, and the sample gas is drawn through the bottles at normally 4–10 l/min for at least 30 minutes per sub-sample. The filter temperature and the flow are checked during the sample.
Rinsing
After each sub-sample, the unheated tube between the filter and the first bottle is rinsed into the bottle. The solution and the rinse liquid are collected in a labelled plastic sample bottle.
Analysis
An accredited laboratory determines the bromide content of the sample and the field blank, for example by ion chromatography according to EN ISO 10304-1, which determines bromide, chloride and fluoride in the same sample.
Calculation and report
The amount of bromide is converted to HBr and divided by the volume of dry sample gas at standard conditions. The result is reported in mg/Nm3 (dry gas at 0 °C and 101.3 kPa) at the plant's reference oxygen content, with its measurement uncertainty.
The requirements in EN 1911, applied to HBr
EN 1911 is written for chlorides and was field-tested at waste incineration plants. Our method list gives HBr as EN 1911 in modified form, and the same quality requirements apply.
| Requirement | Value |
|---|---|
| Measuring range | Validated for chlorides: 1–5,000 mg/m3, expressed as HCl |
| Materials before the bottles | Borosilicate glass, titanium or PTFE (not stainless steel) |
| Filtration temperature | At least 20 °C above the dew point of the flue gas |
| Filter | Retains more than 99.5 % of particles of 0.3 µm |
| Absorption | At least two bottles in series, at most 5 % of the halide in the last one |
| Leak rate | At most 2 % of the sample gas flow |
| Field blank | Below 10 % of the emission limit value, otherwise the measurement is invalid |
| Measurement uncertainty | Expanded uncertainty below 30 % at the daily emission limit value for HCl; for HBr the uncertainty is given in the report |
What does the method measure: HBr or bromides?
EN 1911 determines everything that is volatile at the filter temperature and gives chloride ions in the absorption solution. Applied to bromine, the method determines gaseous bromides in the same way, expressed as HBr. Particles of bromide salts must stay on the heated filter.
The BAT conclusions name EN 1911 for gaseous chlorides but no standard for bromides. Our method list therefore gives EN 1911 in modified form, and with that description HBr is listed in Swedac's register of our accreditation.
If the flue gas contains droplets, for example after a wet scrubber, the standard requires isokinetic sampling at several measurement points. According to our method the same applies when halides and ammonia are present in the gas at the same time. 1 ppm HBr corresponds to 3.61 mg/Nm3, more than twice as much as for HCl.
Where does HBr come from?
HBr forms when the fuel or the waste contains bromine. In waste, the bromine comes among other things from brominated flame retardants in electronics and plastics. A study for the Nordic Council of Ministers of the incineration of such waste found that the flame retardants decompose with good combustion and mostly form HBr. The BAT conclusions for waste incineration require measurement of brominated dioxins when waste with brominated flame retardants is burned.
Bromine is also added on purpose. At waste incineration plants, bromide can be added to the waste or injected into the furnace; at high temperature elemental bromine forms, which oxidises mercury to the water-soluble compound HgBr2 (BAT 31 d). The BAT conclusions for large combustion plants describe the same technique with brominated additives to the fuel.
In the chemical industry HBr is a by-product when organic compounds are brominated. The BAT conclusions for waste gases in the chemical sector do not mention HBr, so a condition for HBr is a matter for the permit.
Which emission limit values apply to HBr?
There is no general emission limit value for HBr in the Swedish ordinances. The Swedish Ordinance on Waste Incineration (SFS 2013:253) limits hydrogen chloride and hydrogen fluoride but does not mention hydrogen bromide, and the word is also absent from the ordinances on large and medium combustion plants (SFS 2013:252 and SFS 2018:471). The BAT conclusions for waste incineration, large combustion plants and the chemical industry have no BAT-associated emission levels (BAT-AELs) for HBr either.
An emission limit value for HBr is therefore set in the permit. For comparison, the limit value for HCl at waste incineration plants is 10 mg/Nm3 as a daily average at 11 % O2.
What does an HBr measurement cost?
The price depends on the number of stacks or ducts and operating conditions, the number of sub-samples and the sampling time, and on the laboratory analysis of each sample and field blank. When HBr is measured together with HCl, HF or dust at the same measurement site, the price per parameter is lower: the probe, filter and travel are shared. Isokinetic sampling, difficult access and a long journey add to the cost. Request a quote and we will reply within two working days. Approximate prices for the most common measurements are in the price guide.
How often must HBr be measured?
As often as the permit says. The ordinances and the BAT conclusions set no measurement frequency for HBr. At waste incineration plants HBr can be sampled on the same occasion as the annual check of HCl and HF, with the same probe and filter.
Frequently asked questions about HBr measurement
Is the HBr measurement accredited?
Yes. Sampling according to EN 1911 in modified form is within METLAB's Swedac accreditation, with hydrogen bromide as a line of its own in Swedac's register. The analysis is done by an accredited laboratory, and the report gives the result with its measurement uncertainty.
Is it the same equipment as for HCl?
Which emission limit value applies to HBr?
None in general. Neither the Swedish Ordinance on Waste Incineration (SFS 2013:253) nor the BAT conclusions have a value for hydrogen bromide, so the limit value is set in the permit. For comparison, HCl has 10 mg/Nm3 as a daily average at waste incineration plants.
How long does an HBr measurement take?
Each sub-sample takes at least 30 minutes, and the BAT conclusions use the average of three consecutive sub-samples. Low concentrations need a longer sampling time or a larger sample volume: the method list's detection limit of 0.0009 mg/Nm3 applies at normal sampling time.
What is required of the measurement site?
Sampling ports, a safe working platform and electricity for the probe heating and the pump, according to EN 15259. After a wet scrubber, where the sample is taken isokinetically at several points, the measurement site must be the same as for dust measurement.
Do you measure hydrogen cyanide too?
Yes. Hydrogen cyanide (HCN) is sampled with the same equipment, but with sodium hydroxide in the bottles and according to Energiforsk's Emissionsmäthandbok (the Swedish emission measurement handbook): see HCN measurement.