HJ 691-2014Ambient air. Sampling technical guideline of semi-volatile organic compounds (SVOCs) (English PDF)

4.1 Sampling head of construction and technical requirements

4.1.1 Large flow, high flow and medium flow sampling head and the technical requirements

Large flow, high flow or the flow sampling head consists of sampling cutter, membranes and membrane support portion, filling the adsorbent Sampling tube, sampling tube frame composition and silicone rubber seals, see Figure 1. Material sampling head should be made of stainless steel or Teflon, etc.

Or organic material does not occur with the measured pollutant chemical reaction is not adsorbed. Monitoring purposes should be based on the relevant standards to select cut Cutter, performance parameters indicators should meet the requirements of HJ 93. For sampling, cutting vessel traffic and large flow cut Point should be used 100L/min and 225L/min, using a sampling tube filled with adsorbent by an inner diameter of 60mm, length of 125mm borosilicate Glass, support for the adsorbent pore diameter 1.2mm (16 mesh) stainless steel screen. Commonly used adsorbent density 0.022g/cm3 Polyurethane foam (referred PUF), macroporous resin or a combination of two adsorbents. For large volume sampling, the sampling tube Dimensions shall comply with the relevant standards. Membrane filters using fine glass or quartz fiber filters having a diameter of 102mm. Filters for when 0.3µm standard particle holdout efficiency of not less than 99%, the air flow velocity of 0.45m/s, single membrane resistance is not greater than 3.5kPa.

1 large flow, high flow and medium flow sampling head structure diagram

4.1.2 Low flow sampling tube

Low-flow sampling tube filled according to the way of the adsorbent can be divided into three types, FIG. 2A is a single-fill mode, FIG. 2B is a three-fill Charge mode, wherein, a sorbent and sorbent b may be the same or different. 2C is around two fill mode. sampling Usually the pipe length 10cm, inner diameter of 20mm borosilicate glass. In establishing sampling method, select the fill in the form adsorbent Mainly it depends on the nature and properties of adsorbent test compound, no matter what form filling options, which should reach the sampling efficiency from 65% to 125%.

C Figure a- front-end sampling tube; rear end b- sampling tube; 1- wool; 2- tip adsorbent;

3- backend adsorbent; 4 - glass fiber filters.

Figure 2 a schematic view of low flow sampling tube

Technical Requirements 4.2 sampler

4.2.1 General technical requirements

SVOCs for large flow sampling, large or medium-volume sampler flow performance shall meet HJ 93, HJ/T 194 and HJ/T 374 requirements. Sampler shall have a cumulative sample size can be automatically converted cumulative sample size standard conditions according to temperature, pressure Feature, you should have automatic timing, power and start again function automatically compensates for changes in traffic due to the resistance and voltage fluctuations caused by the change.

In the case of containing membranes and adsorbents for large volume sampling, the load flow should reach 250 L/min, work Flow point of 225 L/min; the flow rate for sampling, the load flow should reach 125L/min, flow operating point an amount of 100L/min; for large volume sampling, the load flow should reach 900L/min, the operating point of the flow can be achieved

800 L/min. When the sampling resistance of 3.0 ~ 13.0 kPa, the AC power supply voltage variation within 220V ± 10% range, sampler workers the relative change in the operating point traffic within ± 5% of.

For low-flow sampling, sampler performance shall meet HJ/T 194 and HJ 375 requirements, use or mass flow meter Orifice flowmeter, to ensure the accuracy of the flow.

4.2.2 Sampler performance requirements

4.2.2.1 Large flow, high flow or medium-volume sampler performance requirements

Sampler flow indication error <= ± 5%, the relative standard deviation of flow <=2%. Cumulative standard volumetric indication error <= ± 5%, count when the error <= ± 0.1%, the time resolution <=1s. Error shows atmospheric temperature measurement <= ± 2 °C, atmospheric pressure measurement error <= ± 1kPa.

4.2.2.2 Small volume sampler performance requirements

Sampler flow indication error <= ± 5%, the relative standard deviation of flow <=2%. Timing error <= ± 0.1%, the time resolution <=1s.

4.3 Sample Flow Calibration

4.3.1 Standard flow meter and accumulated flow accuracy requirement

Conducting ambient air sampling should be regularly using standard flow meter and accumulated flow sampler of mining flow and total standard conditions Sample volume calibration, standard flow meter and cumulative flow meter measuring range and accuracy requirements are as follows.

(1) Large-volume sampler flow meter standard flow meter and a total range of its range should be at least 0.5 ~ 1.1 m3/min, error <= ± 2%.

(2) large volume sampler standard flow meter and its accumulated flow measurement range should be at least 180 ~ 260 L/min, error <= ± 2%.

(3) The volume sampler standard flow meter and its cumulative flow meter measuring range <= ± at least 60 ~ 125L/min, error 2%.

(4) Low-volume sampler of its meter standard measurement range should be at least 0.1 ~ 5L/min, error <= ± 1%.

4.3.2 Large flow, high flow or the flow volume sampler calibration

Sampling should be conducted regularly single-point and multi-point calibration of flow and cumulative flow calibration standard volumetric calibration. Single-point calibration is only for workers for flow calibration point, the general requirements should be carried out before and after each sampling. Multi-point calibration based on work flow as the center point of a certain stream be within range of the calibration amount in order to ensure the accuracy of the flow sampler, multi-point calibration according to the work required at least once a year. Cumulative standard conditions Volume instrument calibration requires continuous operation (30 ± 5) min, at least every six months or after the sampler maintenance calibration.

Single-point calibration method 4.3.2.1 large flow, high flow or the flow sampler Large flow, high flow or the flow volume sampler calibration device is connected with the sampler shown in Figure 3. Sampler calibration must be Plus sample test module, the sampling head structure sample test module and the actual sampling procedure used, the same membranes and adsorbents.

3 large flow, high flow or medium-volume sampler and flow calibration device connection diagram Sampling should refer to the operation of the instrument using the instructions. The following recommended method is to use a digital orifice flowmeter as standard Sampler flow meter calibration, the calibration method is as follows.

(1) to be calibrated in the gas inlet of the sampler mounted on a sample test module. Figure 3 shows, the meter is connected to a standard Sampling, inspection and calibration to ensure that the system does not leak.

(2) keep the sampler power is off, turn on the standard power meter, the operation proceeds to the flow calibration status.

(3) Turn the power sampler, preheat (5 ~ 10) min. The sampler flow set point work flow, start sampler Sampling into the normal state.

(4) Records sampler flow value vQ, standard cubic meter measuring the flow rate of the average SQ.

(5) according to formula (1) Calculation of the sampler flow indication error.

100% vs

Q QQ

-delta = ×

Where. Qdelta - sampler flow indication error;

vQ - sampler flow set point, L/min;

sQ - a standard flow meter mean of three measurements, L/min.

(6) flow sampling error of indication shall comply with the requirements of section 4.2.2, or should be repaired.

4.3.2.2 Cumulative meter calibration

The cumulative manner meter Figure 3 and the test sample inlet connection, to ensure no leakage. Sampler set work flow, Start sampling, the sampling runs (30 ± 5) min. It was recorded before the cumulative flow meter temperature gauge, pressure gauge before cumulative conditions Standard volumetric size, ambient atmospheric pressure and sample records, according to Equation (2) to calculate the cumulative standard volumetric flow meter, according to the formula (3) Calculate the cumulative standard volumetric indication error, showing error should meet the requirements of 4.2.2.

() 273

101.325

aV B PV

Where. 1T - Cumulative meter before the meter temperature, K;

1P - before the cumulative flow meter gauge pressure, kPa;

aB - ambient atmospheric pressure, kPa;

V - Cumulative meter actual volume, L;

2V - Cumulative standard volumetric flowmeter, L.

100% V VV

-delta = × (3)

Where. Vdelta - Cumulative standard volumetric indication error,%;

1V - standard volumetric sampler record, L.

Multi-point calibration method 4.3.2.3 large flow, high flow or the flow sampler for the flow sampler, at least in 80,100,120L/min three-point calibration. For high-volume sampler, it should be at least 200,225,250L/min three-point calibration. For large flow sampler, if the operating point flow 800L/min, it should be at least 700,800,900L/min three-point calibration. Indication error sampling points flow shall meet the requirements of 4.2.2, Otherwise, the sampler should be repaired or corrected.

4.3.3 Low volume sampler calibration of flow

Low-volume sampler calibration using soap film flow meter, sampler with soap film flow meter connection method shown in Figure 4. Its calibration Method.

Connection diagram Figure 4 Low-volume sampler with soap film flow meter After the sample is energized, setting the operating point of the sample flow rate, sampling run 5min after recording sampler and flow values mq Soap film flow meter indication sq, was repeated 3 times. According to the formula (4) shows the calculation error of the low-volume sampler traffic. Collection Sampler flow indication error should meet the requirements of 4.2.2.

100% ms

q qq

-delta = × (4)

Where. qdelta - sampler flow indication error;

mq - flow value sampler, L/min;

sq - soap film flow meter average of three measurements, L/min.

Selection and sampling efficiency of the extraction medium 5 rating

5.1 Principles of sampling media selection

In establishing ambient air sampling SVOCs choose sampling media should take into account the stability of the sampling medium itself, the collection efficiency of the target compound, the target compound on the stability of the extraction medium, the extraction medium to carry the desorption efficiency and convenience and so on. Select the sampling medium depends on the analysis of the physical and chemical properties. In general, as far as possible to select the sampling media Select sampling less resistance, high adsorption efficiency of the target compound, by air humidity interference small media. Establishing SVOCs mining when the sampling method, sampling medium itself shall be given the stability of the target compound extraction medium static retention efficiency, desorption efficiency, Experimental data and evaluation results of sampling efficiency or dynamic retention efficiency.

5.1.1 Evaluation of the extraction medium itself Stability

Sampling medium itself is to evaluate the stability of the extraction medium during storage prior to use will have some impact on whether the goal of the test compound Given substance or affect sampling efficiency.

In the development of ambient air monitoring and analysis methods SVOCs should be given sampling medium requires that the target compound of blank value.

5.1.2 Evaluation of the target compound on the stability of the extraction medium

When you select the sampling media, it requires to be analyzed is the target compound in the extraction medium should be stable for at least seven days, the evaluation target compound on the method of extraction medium stability as follows.

The three levels of the target compound is added to the extraction medium stored at room temperature for 7 days, and then added to the sample media analysis Concentration within the day and save the target compound concentrations for 7 days, the recovery target compounds should be measured error. otherwise, Description target compound in the extraction medium has changed. In this case, we should try to change the storage conditions or select a different sample media.

5.1.3 Desorption efficiency target compound

Select the sampling medium in the sampling process requires the extraction medium of target compounds produced only physical adsorption, while the chemical can not occur reaction. Therefore, the sampling should target compound can be extracted from all the sampling media. The method of measurement, the use of microinjection is the amount of the target compound added directly to the extraction medium (usually adsorbent) within about 1cm, after one hour in a dark place, Samples extracted by the extraction method, and the calculation of the amount of extraction liquid added quantity ratio of the target compound.

Due to the dynamic desorption of target compounds include preserving performance efficiency of the extraction medium, therefore, should be greater than or equal desorption efficiency movable State retention efficiency. Under normal circumstances, the desorption efficiency of the sample should be 90% to 110%.

5.2 Sampling efficiency and dynamic efficiency evaluation and retention requirements

When using a new adsorbent sampling or when the type of adsorbent and the amount of head sizes sampling and sample flow, sampling time and other conditions occur when significant changes, particularly the sampling time over 24 hours, it should be pre-reserved for sampling efficiency or dynamic efficiency evaluation.

5.2.1 Large flow, high flow and medium flow sampling

5.2.1.1 Determination of sampling efficiency

In a space of two simultaneously placed air samplers. Wherein the sampling head on a sampler filters dropwise uniform quantitative Was added a solution of the title compound in the standard, the standard amount in ambient air at least 3 times the concentration of the target compound, but no more or more than 10 times the concentration after spiking near the middle point of the calibration curve. Another sampler standard solution without direct acquisition environment air. If the target compound is a multi-component material is used to determine the sampling efficiency of the compound must contain the most volatile components.

Two samples collected simultaneously equal volume of air. Preparation of a solvent solution of the compound objective criteria should be used in a vola...