Numerical Analysis on the Flue Gas Temperature Maintenance System of a Solid Fuel-Fired Boiler Operating at Minimum Loads

Michalina Kurkus-Gruszecka,Piotr Krawczyk,Janusz Lewandowski

doi:10.3390/en14154420

Abstract

Currently, energy policy is associated with the increase in the share of renewable sources in systemic energy production. Due to this trend, coal-fired power units must increase their work flexibility. Adapting a coal power plant to work with a lower load often causes the issue of maintaining the temperature before the selective catalytic reduction (SCR) installation at a sufficiently high level. This paper presents a CFD analysis of the mixing area of two flue gas streams before the SCR installation with various methods for mixing flue gas streams. The novelty of the work is mixing the flue gas streams of different temperatures using a flap shape developed by the authors. A series of numerical simulations were performed to develop the location and method of introducing the higher temperature gas, obtaining a uniform distribution of the exhaust gas temperature. The simulation scheme was applied to a series of geometrical modifications of the boundary conditions. The tested solution using only a single, straight flap in the flue gas duct allows the amplitude to be reduced from 298 K to 144 K. As a result of the research, a mixing flap design was developed to reduce the initial temperature amplitude of the flue gas streams from 298 K to 43 K.

Highlights

Due to the increasing number of renewable energy sources with a share in energy systems, research is being conducted on a large scale to increase conventional power plant flexibility [1]
Increasing the flexibility of coal-fired power plant operation by activities related to the regulation of the steam cycle are presented in [4]
In case of a significant power increase in the system due to the power produced by units with priority, e.g., renewables, the currently running conventional power plants reduce their operation [8]

Summary

Introduction

Due to the increasing number of renewable energy sources with a share in energy systems, research is being conducted on a large scale to increase conventional power plant flexibility [1]. Selective catalytic reduction (SCR) technology is the most frequently used for reducing nitrogen oxides in coal-fired power boilers, as indicated in [10,11] Such installations require operation in a specific flue gas temperature range [11], between 585 K and 670 K, depending on the catalyst type. A section of the flue gas duct leading from the main boiler building to the SCR installation, marked in Figure 1 as number 3, was extracted from the presented geometry. InInorodrderertotoadaedqeuqautaetleylynunmumereirciaclallylyrerpeprorodduuceceththeeefeffefcetcstsafaffefcetcitninggththeeexehxhauaustststsrteraemam mmixiixnign,ge, sepspeceicailalyllythtehebubuoyoaynacnycyfofrocrecse,st,htheecocommppuutattaitoinonalagl geoemometertyrywwasascoconnsisdidereerdedatataa scsaclaeleofof1:11:.1T. hTehebabsaiscicgegoemometertirciacladl dimimenesnisoinosnsofofththeeananalaylzyezdedchchanannnelesl escetcitoinonaraereshshoowwnn ininTTaabblele

Height of the analyzed channel section

Findings

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