A balance-based study of the combustion in blast furnace cowpers
Tiala, Janne (2021)
Tiala, Janne
2021
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2021120258628
https://urn.fi/URN:NBN:fi-fe2021120258628
Tiivistelmä
This thesis focuses on modelling and simulation of different firing conditions in cowpers that are a part of a steelmaking process. The cowpers are regenerative heat exchangers that preheat the blast air into the blast furnace. The model is fitted to match process data with the nonlinear least-squares method. Mass- and energy balances are produced and compared to actual process data to ensure that the model predicts the process conditions appropriately. Flue gas measurements are used for the comparison. The challenge in the thesis was to find the different firing conditions for the individual cowpers due to the joint flue gas channel and measurements in the common chimney.
The aim is to reach more efficient firing conditions in cowpers by optimizing the firing conditions. The model developed in this work considers input variables such as fuel and combustion air flow rate and their composition. The model calculates the flame temperature in the cowper based on the input variables, and different flame temperatures can be obtained by adjusting these values. Past data was used to fit the model since the process experiences continuous changes. The results of the analysis
yield a better understanding of the combustion process.
Simulations of different firing conditions were undertaken, and a theoretical model for “optimal” flame temperatures in the cowpers was developed. A test period was conducted based on the model, where excess air in the process was decreased. The results showed that the model overpredicted the flame temperature, and the measured dome temperature, against which the model is fitted, did not show a significant temperature increase. This mismatch should be solved before other tests could be conducted. The mismatch is expected to result from a sum of several unmeasured variables and variables that were seldom measured, which were assumed to be constant between the measurements in the model. The most significant variable was the composition of a fuel gas, which was found to be frequently changing. This indicated that more frequent measurements should be conducted on process variables to obtain a better view of the actual circumstances in the process.
The aim is to reach more efficient firing conditions in cowpers by optimizing the firing conditions. The model developed in this work considers input variables such as fuel and combustion air flow rate and their composition. The model calculates the flame temperature in the cowper based on the input variables, and different flame temperatures can be obtained by adjusting these values. Past data was used to fit the model since the process experiences continuous changes. The results of the analysis
yield a better understanding of the combustion process.
Simulations of different firing conditions were undertaken, and a theoretical model for “optimal” flame temperatures in the cowpers was developed. A test period was conducted based on the model, where excess air in the process was decreased. The results showed that the model overpredicted the flame temperature, and the measured dome temperature, against which the model is fitted, did not show a significant temperature increase. This mismatch should be solved before other tests could be conducted. The mismatch is expected to result from a sum of several unmeasured variables and variables that were seldom measured, which were assumed to be constant between the measurements in the model. The most significant variable was the composition of a fuel gas, which was found to be frequently changing. This indicated that more frequent measurements should be conducted on process variables to obtain a better view of the actual circumstances in the process.