GB/T 16157-1996Determination of particulates and sampling methods of gaseous pollutants emitted from exhaust gas of stationary source (English PDF)

4.2.2 Sampling holes

4.2.2.1 Sampling hole shall be made at selected measurement position. The inner diameter of sampling hole shall not be less than 80 mm, the length of sampling tube shall not be longer than 50 mm. When it is not used, it shall be covered by plate, tube plug or tube cap (Fig.1, Fig.2, and Fig.3). When it is only used for sampling gaseous pollutants, its inner diameter shall not be less than 40 mm.

4.2.3 Sampling platform The sampling platform is setup for sampling by the measurement personnel, it shall have sufficient working area for safety and easy operation by the working personnel. The platform shall not be less than

1.5 m2 in area, and it shall be installed with

1.1 m high guardrails. The distance between the sampling hole and the platform surface shall be approximately

5.1.1 Measurement positions and points According to

4.2.1 and 4.2.4.In normal case, the measurement may be made at a point close to the center of flue duct.

5.1.3 Determination steps

5.2 Determination of moisture content in exhaust gas The moisture content in exhaust gas shall be measured with one of the methods such as the condensation method, dry-wet bulb method or weight method, depending on different measurement objects.

5.2.1 Sampling positions and measurement points According to

4.2.1 and 4.2.4.The samples shall be taken at a measurement point close to the center of the flue duct.

5.2.2 Condensation method

5.2.2.1 Principle Draw a certain volume of exhaust gas from the flue duct and let it pass the condenser. Calculate the moisture content in exhaust gas by the amount of the condensate plus that of the vapor contained in the saturated gas exhausted from the condenser.

5.2.3 Dry-wet bulb method

5.2.3.1 Principle Make the gas flow through the dry-wet bulb thermometer at a certain speed. Calculate the moisture content in the exhaust gas based on the reading of the dry-wet bulb thermometer and the pressure of exhaust gas at the measurement point.

5.2.4 Weight method

5.2.4.1 Principle Draw a certain volume of exhaust gas from the flue duct, let it pass through the moisture absorption tube loaded with moisture absorbent. As the moisture in exhaust gas is absorbed by the moisture absorbent, the increased weight of the moisture absorption tube is deemed as the amount of moisture contained in the exhaust gas of known volume.

5.2.4.2 Sampling devices and instruments Refer to Fig. 12 for the devices used for measuring the moisture content in exhaust gas with weight method.

5.3.2 Albright gas analyzer method

5.3.2.1 Principle Absorb the various components in exhaust gas one by one with different absorption liquids. Based on the change in exhaust gas volume before and after the absorption, calculate the volume percent of each component in exhaust gas.

5.3.2.2 Sampling devices and instruments

5.4 Determination of exhaust gas pressure The pressure of exhaust gas generally refers its static pressure Ps. Refer to

7.5.2 for the instruments and methods for determination of the static pressure of exhaust gas.

6.2 Calculation of molecular weight of exhaust gas

6.2.1 Calculation of molecular weight of exhaust gas As the volume percent Xi and the molecular weight Mi of each gas component are known, the molecular weight of exhaust gas shall be calculated by formula (7).

6.2.2 Calculation of molecular weight of dry exhaust gas The molecular weight of dry exhaust gas Msd shall be calculated by formula (8).

6.2.3 Calculation of molecular weight of wet exhaust gas The molecular weight of wet exhaust gas Ms shall be calculated by formula (9).

7.4 Preparation

7.4.1 Adjust the micrometer gauge to horizontal position.

7.4.2 Check the liquid column of the micrometer gauge for air bubbles.

7.4.3 Check the micrometer gauge for gas leakage. Blow gas into (or suck from) the inlet at the positive pressure end (or negative pressure end) of the micrometer gauge, quickly block the said inlet. If the liquid column of the micrometer gauge remains unchanged in position, it means that the said path has no leakage.

8.2 Summary of the determination methods

8.2.1 Principle of isokinetic sampling method for particulates Insert the flue dust sampling tube into the flue duct through the sampling hole, with the sampling mouth set on the measurement point and directly facing the gas flow. According to the sampling principle of particulate isokinetic, that is - the suction speed of sampling mouth shall equal to the air speed at measurement point (with relative error within 10 %), suck certain amount of dusted gas.

8.2.2 Moving sampling Perform continuous sampling through the determined sampling points with a filter cartridge, with equal sampling duration at each point. Determine the mean concentration in the sampling cross section.

8.2.3 Fixed sampling Take one sample at each measurement point. Determine the mean concentration in the sampling cross section, and find out the status of concentration variations of particulates in the cross section of the flue duct.

8.2.4 Intermittent sampling For emission sources with periodic variations, take samples by sections depending on changes in operating conditions and the duration; then determine the time weighted mean concentration.

8.3 Common sampling tube method (predicted flow speed method)

8.3.1 Principle Before sampling, measure parameters such as temperature, pressure, moisture content and gas flow speed of the exhaust gas at each sampling point, and calculate the required sampling flow for each sampling point under isokinetic sampling conditions with the said parameters combined with the selected sampling mouth diameter. Then take samples at each measurement point with the said flow.

8.3.3 Sampling devices and instruments Refer to Fig. 19 for the sampling device with common sampling tube. It is composed of the common type sampling tube, particulate trap, condenser, dryer, flow metering, control device and sucking pump. If the exhaust gas contains such corrosive gas as sulfur dioxide, a purifier for corrosive gas shall also be attached at the outlet of the sampling tube (e.g. hydrogen peroxide solution washing bottle, etc.).

8.3.3.1 Sampling tube. There are two kinds of sampling tubes, i.e., glass fiber cartridge sampling tube and corundum cartridge sampling tube.

8.3.3.7 Balance. Its sensitivity shall be

0.1 mg.

8.3.3.8 Stopwatch.

8.6 Static pressure balance type isokinetic sampling tube method

8.6.1 Principle Static pressure balance type isokinetic sampling tube method is to utilize the special sampling mouth at the inlet of the sampling tube, there are seams of measuring static pressure on the inner-outer walls of the mouth, to adjust the sampling flow to make the static pressures at the inner and outer seams are equal each other, so as to realize isokinetic sampling condition. This method, which is simple and easy for operation, applies to measurement of emission sources with low dust concentration. However, the application of this method is limited, under the condition of high dust concentration and high dust particle adhesiveness. It is neither applicable for measurement of reverse flue gas speed and flow, so as to replace the measurement of speed and flow.

9.1 Sampling positions and sampling points

9.1.1 Sampling positions.

4.2.1 shall be conformed to in principle.

9.1.2 Sampling points. Since in normal cases the gaseous pollutants are evenly mixed in the sampling section, a point near to the center of flue duct may be selected as the sampling point.

9.2 Sampling method There are chemical method and instrument direct measurement method depending on different methods of measurement and analysis.

9.3.1.3 Dimensions Taking into account the sampling flow, mechanical strength and easiness of cleaning, the inner diameter of sampling tube shall be greater than 6 mm and the length, sufficient for the tube to be inserted to the required sampling point, and shall normally be not less than 800mm.

9.3.1.4 Insulation and heating In order to prevent moisture in the sampled gas from condensation in the sampling tube, and avoid errors caused by dissolution of the measured pollutants in water, the sampling tube shall be heated. Refer to Table 4 for the heating temperatures for several kinds of pollutants. Electrical heating or steam heating may be adopted. When using electrical heating, low voltage power sources with good dielectric property shall be used for the purpose of safety. Asbestos or slag wool may be chosen as the insulation material. Sampling tube materials applicable for various pollutants are listed in Table 5.