The Unburned Carbon Content Prediction In The Fly Ash And Optimal Operation Of Mixed Coal-fired Utility Boilers

The unburned carbon content in fly ash is the important factor that influences the boiler efficiency, and it is an important economic index of thermal power plant. To forecast the unburned carbon content in fly ash timely can not only guide the pulverized-coal combustion of boiler to reduce the coal consumption but also improve the safety and economy of power unit operation. So it is of great important and great value to study the prediction, formation cause and influence factors, the operating parameters'optimization and adjustment of the unburned carbon content in fly ash.At first, this paper summarize the harm of the high ash fly carbon and the importance of the forecast technique, at the same time introduce the status of this technique and the control method of the unburned carbon content in fly ash.Secondly, in this paper, the unburned carbon content in the fly ash of a 700MW utility tangentially firing coal burned boiler is experimental investigated, and taking advantage of the nonlinear dynamics characteristics and self-learning characteristics of artificial neural network, an artificial neural network model on un-burned property of the high capacity boiler is developed and verified. The absolute errors of the experimental value and the calculated value of the validation samples are 0.0307, 0.0062, 0.0463, the relative errors are 1.07%, 0.26%, 2.14%, shows that the model can accurately predict the carbon content of fly ash in various operating conditions from the boiler.By using a neural network to model the unburned carbon content in the fly ash from a high-capacity boiler, various factors on the impact of the unburned carbon in the fly ash were quantitative analyzed, and pointed out the influence trends, causes and control measures of the various factors on the unburned carbon content in the fly ash.Finally, combination the neural network model and genetic algorithm to optimize the condition 24, the unburned carbon content in fly ash reduces from 2.81% to 1.41% by adjusting the second throttle opening degree, burn throttle opening and the furnace outlet oxygen. And based on condition 24, optimized the conditions that with different grinding units burning Indonesian coal. The results show that the more grinding units burning Indonesian coal, the higher the unburned carbon content. If use one grinding unit Blending Indonesian coal, the use of C grinding better than D grinding.