Abstract
in order to realize the accurate prediction of acid dew point, a set of measurement system of acid dew point for the flue gas flue gas in the tail of the boiler was designed and built, And measured at the outlet of an air preheater of a power plant of 1 000 MW, The results show that: Under the same conditions, with the test temperature decreases, Nu of heat transfer tubes, fouling and corrosion of pipe wall and corrosion pieces gradually deepened. Then, the measured acid dew point is compared with the acid dew point obtained by using the existing empirical formula under the same coal type. The dew point of engineering acid is usually about 40 ℃ lower than the dew point of thermodynamic acid because of the coupling effect of fouling on the acid liquid, which can better reflect the actual operation of flue gas in engineering and has certain theoretical guidance for the design and operation of deep waste heat utilization system significance.
Highlights
With the continuous improvement of the national energy-saving and emission reduction targets, it is urgent to reduce the temperature of the boiler exhaust gas and improve the utilization of the tail flue gas waste heat [1]
[2] the boiler exhaust gas temperature can not be reduced, when the exhaust gas temperature is too low, the heat exchanger is operated under the acid dew point of the flue gas, the SO3 in the flue gas will form a H2SO4 droplet with the condensed water vapor, Low temperature corrosion and ash deposition on the surface will inevitably increase the flow resistance of the flue gas and decrease the heat transfer efficiency [3]
Domestic and foreign institutions for the study of low temperature corrosion and acid dew point can be divided into two categories: a class of empirical formula focusing on the acid dew point [4], such as China's power industry commonly used in the former Soviet Union Computational Standard Method "empirical estimation formula, which is based on experimental data of All-in-one Institute of Thermal Engineering in the 1950s
Summary
With the continuous improvement of the national energy-saving and emission reduction targets, it is urgent to reduce the temperature of the boiler exhaust gas and improve the utilization of the tail flue gas waste heat [1]. The acid dew point is the key index restricting whether coal-fired power plants can utilize the waste heat of the tail flue gas in depth. The acid dew point obtained by these two methods can prevent boiler tail replacement Surface is subject to the risk of low temperature corrosion, but its design reliability parameters are too high, can not truly reflect the dew point characteristics of coal-fired flue gas, that is, within a certain range of thermodynamic acid dew point containing acid ash particles did not show the film should Sediment characteristics, and has some limitations. 1-inner sleeve; 2-outer sleeve; 3-corrosive sheet; 4- aircooled coil; 5- temperature recorder; 6- control cabinet; 7- constant temperature water tank; 8- electric heating pipe; Figure 1 Engineering acid dew point measurement test system diagram. The corrosive sheet was taken out of the top of the smoking gun and placed on the numbered A4 paper, respectively, Test paper on the surface of the corrosion test piece of acid to observe the discoloration of the pH test paper and compared with the original pH paper, if the pH test paper no discoloration, the temperature point is not in the flue gas acid dew point range, polished corrosion sheet to the clean state, the test Section back into the flue, the other conditions remain unchanged, lower the wall temperature of the heat transfer tube, repeat the above steps until the end of the test, draw the heat transfer wall sediment weight and Nu with the outer wall temperature curve, and according to Nu number Interval and pH test paper color change, get the project acid dew point roughly change range
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