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

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4420
Author(s):  
Michalina Kurkus-Gruszecka ◽  
Piotr Krawczyk ◽  
Janusz Lewandowski
Keyword(s):  
Flue Gas ◽  
Catalytic Reduction ◽  
Gas Temperature ◽  
Gas Streams ◽  
Different Temperatures ◽  
Flap Design ◽  
Lower Load ◽  
Higher Temperature ◽  
High Level ◽  
Exhaust Gas Temperature

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.

scholarly journals Hybrid technology of reduction of nitrogen oxides (NOx) in exhaust gases; Part 2 – Numerical model of pilot scale regenerative rotary air heater (RAH) retrofited with selective catalyst reduction (SCR) modules

2019 ◽  
Vol 82 ◽  
pp. 01016 ◽  
Author(s):  
Andrzej Kwiczala ◽  
Robert Wejkowski
Keyword(s):  
Numerical Model ◽  
Flue Gas ◽  
Catalytic Reduction ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Gas Temperature ◽  
Air Heater ◽  
Exhaust Gas Temperature ◽  
Heat Exchange Efficiency ◽  
Flue Gas Denitrification

This article exhibits the results of the analysis performed to verify the effectiveness of the hybrid flue gas denitrification system (herein referred to as HDS) which involved the retrofitting for selective catalytic reduction (SCR) material into a regenerative rotary air heater (RAH). A numerical model corresponding to the actual pilot scale RAH operating conditions was developed. The ultimate intent of the numerical model is to provide a platform where the technology can be implemented on full scale air preheaters. The numerical analysis performed on the pilot scale HDS installation showed a 3% decrease in heat exchange efficiency in the exchanger. This decrease was significantly minimized by the use of blades adjusting the distribution of flue gases entering the RAH. This means that the exhaust gas temperature at the exchanger outlet increased by 4°C, which corresponds to an average of 0.3% increase in the boiler outlet loss. It was also recognized that the air temperature was reduced by 8°C, which does not translate into significant changes in boiler performance parameters. other boiler operating parameters in a noticeable way during operation.

scholarly journals The Causes Analysis of the Air Preheater and Performance Blocking Evaluation of the Measures on the SCR De-NOx Unit

2019 ◽  
Vol 118 ◽  
pp. 03056
Author(s):  
Su Pan ◽  
Pengfeng Yu ◽  
Linbo Liu ◽  
Jing Han ◽  
Xiao Shen
Keyword(s):  
Flue Gas ◽  
Differential Pressure ◽  
Control Measures ◽  
Gas Temperature ◽  
Air Preheater ◽  
Environment Temperature ◽  
Ammonium Bisulfate ◽  
And Performance ◽  
Exhaust Gas Temperature ◽  
Ammonia Injection

In order to solve the problem of abnormal rise of the differential pressure of the revolving air preheater on 300MW unit, we analysed the causes of abnormal rise of the differential pressure of the air preheater and evaluated performances of control measures, through historical data mining and on-site inspection of the unit. The results show that, with the gradual decrease of environment temperature with the decrease of the exhaust gas temperature, the ashes in flue gas are bound by acid liquid produced by condensation of flue gas, and the adhesion areas of the ammonium bisulfate produced in the denitration process are enlarged. However the original set ash blowing pressure can no longer satisfy the requirements of the air preheater, giving rise to the differential pressure of the air preheater on both sides to rise. The reason of the higher differential pressure of the unilateral air preheater is that the large ammonia injection amount, leading to the increases of ammonia escape of the denitrification system. So the side of the air on preheater ammonium bisulfate type blockage is more serious. After the Measures of Adjusting distribution coefficient of ammonia supply valve on both sides, increasing the dust blowing frequency and pressure of the air preheater, the differential pressure of air preheater on both sides are close to the consistent. The decrease amplitude of the differential pressure of the air preheater on 280MW is about 300-500Pa.

Energy-Saving Analysis of 215MW Cogeneration Boiler Adding Low Temperature Economizer

2013 ◽  
Vol 448-453 ◽  
pp. 2777-2780 ◽  
Author(s):  
Yan Feng Liu ◽  
Shi Ping Li ◽  
Xiang Hong Li
Keyword(s):  
Low Temperature ◽  
Flue Gas ◽  
Waste Heat ◽  
Natural Circulation ◽  
Peak Load ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Bag Filter ◽  
Actual Operation ◽  
Exhaust Gas Temperature

A 215MW cogeneration B&W670/13.7-M type high-pressure natural circulation boilers, the exhaust gas temperature is set as 143 °C, while in the actual operation, the average exhaust gas temperature is 155 °C, and when the unit is running at full capacity in summer the highest exhaust gas temperature is 169.6 °C. In order to satisfy the normal operating temperature of bag filter in summer peak load, and recover low temperature waste heat of fule gas, low temperature economizer is added to the thermal system. Therefore, low-temperature economizers are respectively added in four flues which are between the outlet of the air preheater and the entrance of the bag filter, this will achieve the purpose of reducing flue gas temperature by transferring heat between condensate and flue gas, ensuring the units safe operating and improving the overall operating performance of the boiler.

scholarly journals The Experimental and Simulation Study of Selective Catalytic Reduction System in a Single Cylinder Diesel Engine Using NH3as a Reducing Agent

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Manoj Kumar Athrashalil Phaily ◽  
Sreekumar Jayachandra Sreekala ◽  
Padmanabha Mohanan
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Mass Flow ◽  
Catalytic Reduction ◽  
Pt Catalyst ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Single Cylinder ◽  
Induction Rate ◽  
Exhaust Gas Temperature

Selective catalytic reduction (SCR) technology has been widely used in automotive applications in order to meet the stringent limits on emission standards. The maximum NOxconversion efficiency of an SCR depends on temperature and mass flow rate of an exhaust gas. In order to assess the suitability of Cordierite/Pt catalyst for low temperature application, an experimental work is carried out using single cylinder diesel engine for different load conditions by varying ammonia induction rate from 0.2 kg/hr to 0.8 kg/hr. The simulation is carried out using AVL FIRE for the validation of experimental results. From the study, it has been found that for 0.6 kg/hr ammonia induction rate the maximum conversion is achieved, whereas, for 0.8 kg/hr, conversion is reduced due to desorption of ammonia. Also it has been found that, at 75% of load, for all mass flow rates of ammonia the conversion was drastically reduced due to higher exhaust gas temperature and higher emission of unburnt hydrocarbons. More than 55% of NOxconversion was achieved using Cordierite/Pt catalyst at a temperature of 320°C.

Effect of Cordierite-Modified on SCR Commercial Catalyst

2014 ◽  
Vol 960-961 ◽  
pp. 176-181
Author(s):  
Wen Chang Xi ◽  
Qing Cai Liu ◽  
De Liang Niu ◽  
Jian Yang ◽  
Qiang Yang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Flue Gas ◽  
Catalytic Reduction ◽  
Rutile Phase ◽  
Gas Analyzer ◽  
Commercial Catalyst ◽  
Mixing Method ◽  
Higher Temperature ◽  
Solid Liquid ◽  
Flue Gas Denitrification

The V2O5-WO3/TiO2honeycomb catalysts with cordierite modified were prepared by solid-liquid mixing method. Its thermal stability, crystal structure, abrasion resistance and activity were studied by XRD, abrasion equipment and simulated flue gas analyzer,respectively. The results indicated that V2O5-WO3/Cordierite-TiO2honeycomb catalyst possessed a better thermal stability, mechanical property and activity at the higher temperature comparing to commercial catalyst. There was no rutile phase present after the catalysts were calcined at 700°C, and the vanadia and tungsten trioxide phases could be apparently visible on TiO2. Key word:V2O5-WO3/ TiO2; Cordierite; flue gas denitrification; NOx; selective catalytic reduction (SCR)

Effect of CO2/O2 on Catalytic Reduction of NO by Iron

2012 ◽  
Vol 616-618 ◽  
pp. 1849-1852 ◽  
Author(s):  
A Long Su ◽  
Ya Xin Su ◽  
Hao Cheng
Keyword(s):  
Flue Gas ◽  
No Reduction ◽  
Catalytic Reduction ◽  
X Ray Diffraction ◽  
Sudden Drop ◽  
Reduction Of No ◽  
X Ray ◽  
Reduction Efficiency ◽  
Different Temperatures ◽  
Temperature Programmed

This paper presents the results of the reaction between metallic iron mesh rolls and NO in the presence of CO2/O2 at different temperatures. All experiments were carried out in a ceramic tube controlled by the temperature programmed electrical furnace. About 99% NO reduction was achieved when temperature was above 700°C in the absence of CO2/O2. Results showed that CO2 in the flue gas had little effect on the NO reduction. NO reduction efficiencies were observed to exceed 95% for all CO2 concentrations at above 700°C. The addition of O2, however, caused a sudden drop by about 76% in NO reduction efficiency. Scanning electron microscope (SEM) results showed that the oxidation of iron in O2 atmosphere led to a more continuous and impervious oxide layer than that in CO2 atmosphere. Results using X-ray diffraction (XRD) to detect the iron samples after reactions revealed that FeO, Fe3O4, Fe and Fe2O3 were formed in CO2 atmosphere, but Fe3O4 and Fe2O3 were formed when O2 was added.

Compound Control Strategy Based on Active Disturbance Rejection for Selected Catalytic Reduction systems

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Jinbiao Ning ◽  
Fengjun Yan
Keyword(s):  
Control Strategy ◽  
Disturbance Rejection ◽  
Catalytic Reduction ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Model Uncertainties ◽  
Compound Control ◽  
Active Disturbance Rejection ◽  
Exhaust Gas Temperature ◽  
Scr System

Urea-based selected catalytic reduction (SCR) systems are effective ways in diesel engine after-treatment systems to meet increasingly stringent emission regulations. To achieve high NOx reduction efficiency and low NH3 slip, the control of the SCR system becomes more challenging, especially in transient operating conditions with model uncertainties. To effectively address this issue, this paper proposed a compound control strategy with a switching mechanism between an active disturbance rejection (ADR) controller and a zero-input controller. The ADR controller estimates and rejects the total (internal and external) disturbances from the SCR system when the exhaust gas temperature is high and its variation is small. The zero-input controller is used to lower ammonia surface coverage ratio to avoid high ammonia slip when exhaust gas temperature suddenly rises. The proposed control strategy is validated through a high-fidelity GT-Power simulation for a light-duty diesel engine over steady states and federal test procedure (FTP-75) test cycle. Its effectiveness is demonstrated especially in rapidly transient conditions with model uncertainties.

scholarly journals Experimental Study on Operation Regulation of a Coupled High–Low Energy Flue Gas Waste Heat Recovery System Based on Exhaust Gas Temperature Control

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 706 ◽  
Author(s):  
Jiayou Liu ◽  
Fengzhong Sun
Keyword(s):  
Flue Gas ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Gas Flow ◽  
Waste Heat ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Waste Heat Recovery System ◽  
Recovery System ◽  
Exhaust Gas Temperature

Controlling the exhaust gas temperature (EGT) of coal–fired boilers at a reasonable value is beneficial to ensuring unit efficiency and preventing acid corrosion and fouling of tail heating surfaces in power plants. To obtain the operation regulation of coupled high–low energy flue gas waste heat recovery system (CWHRS) under a given EGT, experimental equipment was designed and built. Experiments were carried out to maintain the exhaust gas temperature under different flue gas flow, flue gas temperature and air temperature conditions. As the flue gas flows, the flue gas temperatures and air temperatures increased, and the bypass flue gas flow proportions or the water flows of the additional economizer were increased to maintain the EGT at about 85 °C. An improved low temperature economizer (LTE) and front located air heater (FAH) system were put forward. As the flow of the crossover pipe increased, the EGT and the inlet water temperature of the LTE increased. As the flow of the circulating loop increased, the EGT and the inlet water temperature of the LTE decreased. Operation regulations of LTE–FAH system under four cases were given. The operation regulations of CWHRS and LTE–FAH system can provide references for power plant operation.

Model Predictive Control of Integrated Hybrid Electric Powertrains Coupled With Aftertreatment Systems

2014 ◽  
Author(s):  
Junfeng Zhao ◽  
Junmin Wang
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Fuel Economy ◽  
Catalytic Reduction ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
System Temperature ◽  
Hybrid Electric ◽  
Exhaust Gas Temperature ◽  
Aftertreatment Systems

For hybrid electric vehicles (HEVs), especially for diesel-electric hybrid vehicles, the low exhaust gas temperature induced by the hybridization and fuel economy optimization will bring significant impact on the performance of the exhaust gas aftertreatment systems, and may consequently lead to violation of the tailpipe emission constraints. To investigate the influence of diesel powertrain hybridization on the aftertreatment system and tailpipe emissions, an integrated HEV model is established by incorporating the thermodynamics models of the aftertreatment systems. This comprehensive model is able to predict engine-out nitrogen oxides (NOx) concentration, exhaust gas temperature, and to describe the temperature dynamics in the aftertreatment systems. A static map of selective catalytic reduction (SCR) system temperature-dependent de-NOx efficiency is utilized, so that the tailpipe NOx can be predicted. To investigate the tradeoff between fuel consumption and emissions for diesel HEV with aftertreatment systems, a preliminary study is carried out on optimally balancing both aspects via a model predictive control scheme. This controller is designed with an explicit consideration of HEV tailpipe NOx emission constraint. The simulation results show that the HEV tailpipe NOx emissions can be regulated by slightly sacrificing the fuel economy.

Numerical Simulation Research on the Heating Process of Air by Waste Heat

2014 ◽  
Vol 694 ◽  
pp. 260-265
Author(s):  
Zi Fang Wang ◽  
Jian Li Liu ◽  
Lian Sheng Liu ◽  
Ye Bin Yin ◽  
Jin Xiang Wu ◽  
...  
Keyword(s):  
Flue Gas ◽  
Waste Heat ◽  
Heating Process ◽  
Exchange Effect ◽  
Simulation Research ◽  
Tube Heat Exchanger ◽  
Dry Air ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Reasonable Use

Flue gas of boiler is a kind of great potential waste heat resource. Relatively high temperature of exhaust has caused a vast waste of energy and serious environmental thermal pollutions. To make a full and reasonable use of the heat resource, a simplified single-tube heat exchanger is introduced in this paper. Dry air and wet air with different temperatures transfer heat with flue gas in the same model. And the results show that heat near the inner wall exchanges more violently than any other space in the heater. For dry air, the higher temperature of the air enters into the heater, the lower heat transfer effect of the heater. Heat exchange effect of the wet air with 0.03 mole fraction of water is more higher than that of dry air in this model.

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