Differential pressure type self-reflux multipoint uniform flue gas sampling system

Abstract

The invention discloses a differential pressure type self-reflux multipoint uniform flue gas sampling system which comprises sampling probes, a mixing main pipe, a reflux pipe, a control unit, and a partition combination switch and a flow meter which are respectively connected with the control unit, the partition combination switch is arranged on the sampling probe and is controlled by the controlunit; a main pipe is arranged between the sampling probes and the upper end of the mixing main pipe; the flow meter is arranged in the middle of the main pipe, a plurality of sampling probes are uniformly arranged along the main pipe, the lower ends of the sampling probes are arranged in a flue at the front end of an air pre-heater, the reflux pipe is arranged between the lower end of the mixingmain pipe and the flue at the rear end of the air pre-heater, and the reflux pipe is communicated with the flue at the rear end of the air pre-heater; the flue gas in the flue can be uniformly taken out, so that accurate measurement of NOx in the flue gas is realized, and the working efficiency is improved.

Description

technical field [0001] The invention belongs to the field of flue gas sampling systems, in particular to a differential pressure self-reflux multi-point uniform flue gas sampling system. Background technique [0002] At present, under the new form, the NOx emission limit of "coal-fired power units reaching the emission level of gas turbines is environmentally friendly" is less than 50mg / m3, which puts forward higher requirements for the denitrification system to achieve energy conservation, environmental protection and safety. Large and medium-sized units in coal-fired power plants have the characteristics of large cross-sectional area of ​​SCR flue, high flue gas temperature, uneven distribution of flue gas flow field, and high smoke concentration, resulting in uneven distribution of NOx in the flue. At present, most CEMS measurement systems for NOX at the denitrification outlet are The traditional single-point sampling device is still used. Under actual operating condition...

AI Technical Summary

Problems solved by technology

Large and medium-sized units in coal-fired power plants have the characteristics of large cross-sectional area of ​​SCR flue, high flue gas temperature, uneven distribution of flue gas flow field, and high smoke concentration, resulting in uneven distribution of NOx in the flue. At present, most CEMS measurement systems for NOX at the denitrification outlet are The traditional single-point sampling device is still used. Under actual operating conditions, the measured value of single-point sampling will deviate from the actual value. The NOx at the denitrification outlet is not representative. Measuring points that are fully mixed and evenly) are inconsistent; lead to the uncontrollable amount of ammonia injection. When the amount of ammonia injection is insufficient, it will cause environmental protection to exceed the standard. Ammonium bisulfate plugging air preheater

[0003] Whether it is a single-point sampling point or a three-point sampling point, in a large cross-section uneven flow field, the measurement data are not representative and cannot truly reflect the actual pollutant concentration of the flue gas

Coal-fired power plant CEMS still adopts single-point sampling method, which is difficult to ensure the uniformity of flue gas sampling at the SCR outlet flue, and cannot accurately reflect the actual operation of the SCR flue gas denitrification device

In response to this deficiency, a multi-point combined sampling system is also used. There are several related multi-point sampling patents. However, power plants sometimes need to measure the NH3 and NOx concentrations in designated areas of the SCR flue section to guide AIG adjustments. Traditional multi-point sampling The system cannot meet the fixed-point measurement of NOx concentration in different areas, and cannot effectively guide precise ammonia injection

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