Thermodynamic and Numerical Analysis of Tangentially Fired Boiler for Increasing Efficiency and Reducing Environmental Pollution

Navid Abdollahi,Ramin Haghighi-Khoshkhoo

doi:10.3311/ppme.11416

Abstract

The evaluation of heat transfer and fluid mechanics mechanisms to increase the thermal efficiency and combustion quality in heavy industries, such as power plants, are important and significant issues in the field of engineering sciences, which can lead to significant advances. In this regard, the present paper has been developed with thermodynamic and numerical simulations of the MONTAZER GHAEM Power Plant boiler to study the increase in efficiency and reduce environmental pollution. Also in this research, the results of practical tests have been used to verify the simulations. The thermodynamic simulation results show that the required fuel consumption of the burners in current operating conditions is not 9.1 kg/s, but it is 8.1 kg/s. The low efficiency of the set, which leads to the injection of more than the required amount of fuel to the boiler, cause the non-corresponding power generation for injected fuel, which results in the reduction of the plant thermal efficiency from 36.4% to 33.9%. The results of computational fluid dynamics show that the lightness of natural gas combustion products and, the no-flow accumulation in the lower parts of the furnace, reduce the produced steam, which results in power loss at the exit. Numerical results also show that the highest rate of NOX production occurs near the burners due to the high flame temperature and high oxygen mass fraction and consequently, the non-uniform distribution of heat in the furnace.

Highlights

1 Introduction Tangentially fired boilers are mainly used in the power generation industry due to the proper flame distribution and uniform heat flux
McKenty et al [1] developed a model for a dual fuel tangentially fired boiler using computational fluid dynamics and evaluated the flow behavior and NOX production in the furnace
By the Reynolds time averaging method, mass and momentum equations converted to Reynolds averaged Navier–Stokes equations (RANS) as follows: Fig. 1 Simulated cycle of unit 4 of MONTAZER GHAEM Power Plant in THERMOFLEX

Summary

Introduction

Fired boilers are mainly used in the power generation industry due to the proper flame distribution and uniform heat flux These boilers are characterized by the shape of the furnace and the location of fuel and air entrances. Tang et al [6] developed a numerical model for simulating flow and combustion indices in a 200 MW tangentially fired boilers They investigated wall steam tubes overheating problem and the effect of fuel input percentage on the furnace wall temperature. In the case of the commissioning of a power plant with natural gas, it is observed that the output power of each boiler unit is reduced from nominal 156.25 MW to 130 MW, and if the fuel flow rate increases to more than the nominal value, the generated power increases by up to 140 MW Under these circumstances, with the maximum tilt angle (-30°), superheater tubes overheat and disappear.

Momentum equation

Energy equations The energy equation is represented as follows

Results and discussions

Conclusion