rbr flue gas differential pressure, flow rate and total emission description

The main source of air pollution is the exhaust gas discharged from industrial pollution sources, of which the flue gas is extremely harmful. Therefore, flue gas (referred to as flue gas) testing is one of the main contents of atmospheric pollution source monitoring. Measuring the flue gas flow rate and pollution concentration is of great significance for evaluating the environmental impact of flue gas emissions and testing the effectiveness of boiler installations.

(1) Selection of sampling position

It is very important to correctly select the sampling position and determine the number of sampling points for the samples that are representative of the collected data and meet the measurement requirements. The sampling position should be a pipe section with stable airflow. In principle, the distance between the elbow and the shape of the cross-section should be avoided at least 1.5 times the diameter of the flue, and the air flow velocity in the flue should be above 1 m / s. The location of the sampling hole and sampling point depends on the size of the flue and the shape of the cross section. The arrangement of sampling points of flues of different shapes is explained below.

1. Round flue

The distribution of sampling points is shown in Figure 1 (a). The section of the flue is divided into an appropriate number of concentric rings of equal area. Each sampling point is on the center line of equal area. The number of divided equal area rings is determined by the diameter of the flue.

2. Rectangular flue

The flue section is divided into rectangular blocks of equal area, and the center of each block is the sampling point. See Figure 1 (b). The number of blocks of equal area for rectangular flues of different areas is shown in Table 1.

Table 1 Block and measurement points of rectangular flue

3. Arched flue

According to the layout principle of sampling points of circular flue and rectangular flue respectively, see Figure 1 (c).

(2) Determination of flue gas state parameters

The flue gas state parameters include pressure, temperature, relative humidity and density.

1. Pressure

The instrument for measuring the pressure of flue gas is an S-type bi-tube, which is suitable for flue ducts with large dust concentration. The Pitot tube is composed of two stainless steel tubes, and the measuring end is made into two mutually parallel openings in opposite directions. As shown in Figure 2, the Pitot tube is connected to the tilt pressure gauge with a rubber tube during the measurement. The full pressure is measured; the other is against the airflow and the static pressure is measured; the difference between the two is the dynamic pressure. Due to the influence of suction on the opening facing away from the airflow, the resulting static pressure has a certain error from the actual value, so it must be corrected in advance. The method is to compare with the standard wind speed tube in the air flow with an air flow speed of 2 ~ 60m / s. The ratio of the speed value measured by the S-type Pitot tube and the standard wind speed tube is called the correction factor of the Pitot tube. When the flow velocity is in the range of 5-30m / s, the correction coefficient value is 0.84. The dynamic pressure value measured by the tilt pressure gauge is calculated as follows:

p = L? K? d (1)

In the formula: L-inclined tube pressure gauge reading;

K-Correction coefficient, indicate 0.2, 0.3, 0.4, 0.6, 0.8 on the inclined tube pressure gauge;

d-Relative density of alcohol, d = 0.81.