Method for correcting and controlling impacts of water content in fuel on loads of boiler

Abstract

Water content in a biomass fuel is a greatest impact factor with most frequent change of fuel properties, largest range of fluctuations and greatest impacts on loads of a boiler, the invention discloses a method for correcting and controlling the impacts of the water content in the biomass fuel on the loads of the boiler, a curve is firstly calibrated according to the change of low heat value of the fuel along with the water content, then the water content in the fuel is obtained by calculation according to air supply volume, feeding quantity and air induction volume obtained by actual measurement, and heat which can be provided by the fuel put into a furnace chamber is further obtained according to the calibrated curve. The heat is taken as a feedback value of a controller, the heat needed by the boiler under the operation loads is taken as a set value of the controller, the correction coefficient of the water content in the fuel is obtained by the PID operation, and the rotational speed of a feeding machine is corrected. The method eliminates the fluctuations of the loads of the boiler along with the water content of the fuel, ensures the safe and stable operation of the boiler and improves the operation efficiency of the boiler by realizing the real-time and accurate control of the amount of the biomass fuel.

Description

technical field [0001] The invention belongs to the field of thermal control, and in particular relates to a method for correcting and controlling the influence of moisture content of biomass fuel on boiler load. Background technique [0002] 1. Unstable properties of biomass fuel [0003] The composition of biomass fuel components is similar to that of coal, including moisture, ash, volatile matter and fixed carbon. The industrial analysis and calorific value of several common biomass fuels are shown in Table 1 below. The moisture content of the biomass fuel in Table 1 is not high, but this is a dried design fuel sample, and the moisture content of the fuel actually used by the power plant is not so ideal. [0004] Table 1 Biomass fuel industrial analysis (%) and calorific value (kJ / kg) [0005] type moisture Ash Volatile matter fixed carbon high calorific value straw 4.97 13.86 65.11 16.06 16329 rice husk 4.70 15.8 69.30 10.20 1467...

AI Technical Summary

Problems solved by technology

Changes in moisture cause fluctuations in the calorific value of the fuel, which in turn leads to instability of the heat input into the furnace, which is not conducive to the automatic control of the boiler feed, and is likely to cause fluctuations in the boiler load

[0010] 2. Influence of moisture change of biomass fuel on boiler control

[0013] When the moisture content of the biomass fuel is quite different from the designed fuel, it is easy to cause fluctuations in the heat into the furnace and unstable combustion.

When the moisture in the biomass fuel increases, the calorific value of the fuel decreases, and the control system still calculates the feed amount according to the design fuel, which will result in a decrease in the heat input into the furnace, which will inevitably lead to insufficient actual output of the boiler.

If you wait until the steam volume of the boiler decreases before adjusting the air supply volume or increasing the feed volume after the oxygen volume in the tail flue rises, this process will take a relatively long time due to the large inertia hysteresis of the boiler system, resulting in large fluctuations in the boiler load , reducing boiler operating efficiency

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