A Novel Design for Reduction of Ammonium Bisulfate Deposition in the Rotary Air Preheater

2018 ◽  
Author(s):  
Yufan Bu ◽  
Limin Wang ◽  
Xiaoyang Wei ◽  
Lei Deng ◽  
Defu Che
Keyword(s):  
Flue Gas ◽  
Gas Flow ◽  
Catalytic Reduction ◽  
Operating Cost ◽  
Reaction Chamber ◽  
Air Preheater ◽  
Accurate Temperature ◽  
Ammonium Bisulfate ◽  
Lower Temperature ◽  
Novel Design

Nitrogen oxide (NOx) emitted from boilers in coal-fired power plant may be reduced by 90 percent through the application of the selective catalytic reduction (SCR). However, the escaped ammonia from the SCR systems could react with sulfur oxides (SOx) in the flue gas to form ammonium bisulfate (ABS) in exhaust systems. The blockage and corrosion caused by ABS seriously impact the rotary air preheater (RAPH), which would not only increase operating cost on ash-blowing and cleaning but also lead to unplanned outage. To solve the problem, in this paper a novel preheater system is proposed. A single preheater is split into two sub-preheaters, between which the main flue gas flow is mixed with the recirculated flue gas from outlet of the lower-temperature preheater. After the mixing point, a reaction chamber and a precipitator are installed. A numerical finite difference method (FDM) is employed to model the RAPH and obtain the accurate temperature distribution of fluid and heat transfer elements. The initial formation temperatures of (NH4)2SO4 and ABS are 200 °C and 170 °C, respectively, according to the flue gas composition in this work. By calculation, this split design of the RAPH is believed to be effective in reducing deposition of ABS.

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.

scholarly journals Influence of ammonia on wet-limestone flue gas desulfurization process from coal-based power plant

2019 ◽  
Vol 116 ◽  
pp. 00101
Author(s):  
Tomasz Wypiór ◽  
Renata Krzyżyńska
Keyword(s):  
Particulate Matter ◽  
Flue Gas ◽  
Gas Flow ◽  
Catalytic Reduction ◽  
Flue Gases ◽  
Flue Gas Desulfurization ◽  
Flow Capacity ◽  
Desulfurization Process ◽  
Denitrification Process ◽  
Raw Wastewater

The paper presents data concerning the influence of ammonia on wet flue gas desulfurization (WFGD) absorber. Paper presents preliminary results of an industrial scale study on WFGD absorber, that collects flue gases from four boilers with total flue gas flow capacity of the WFGD equal to 1 500 000 Nm3/h. Each boiler is equipped with selective non-catalytic reduction (SNCR) with urea injection. It was shown, that ammonia present in the flue gas upstream the WFGD increases the pH of absorption slurry, impacting the desulphurization process. In addition, analysis of particulate matter upstream and downstream the absorber shows an increase of the concentration of ammonium species in the particulate matter about 14 times, as average. Moreover, a non-optimized denitrification process can cause a high NH4+ concentration in the absorption slurry (up to 768 mg/L) and raw wastewater (up to 891 mg/L).

scholarly journals Status and development for detection and control of ammonium bisulfate as a by-product of SCR denitrification

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kunling Jiao ◽  
Xiangyang Chen ◽  
Xuan Bie ◽  
Daokuan Liu ◽  
Mingjie Qiu ◽  
...  
Keyword(s):  
Flue Gas ◽  
Negative Impact ◽  
Dew Point ◽  
Detection Methods ◽  
Nox Removal ◽  
Air Preheater ◽  
Catalyst Life ◽  
Ammonium Bisulfate ◽  
The Impact ◽  
Ammonia Injection

AbstractWhen denitrification technology using NH3 or urea as the reducing agent is applied to remove NOx from the flue gas, ammonium bisulfate (ABS) by-product will also be generated in the flue gas. ABS has an impact on catalyst life span, denitrification efficiency etc., air preheater and its downstream thermal equipment also have a significant negative impact due to its plugging and corrosion. The requirement for NOx removal efficiency is improved by ultra-low emissions in China. However, wide-load denitrification makes the flue gas composition and temperature changing more complicated. Increasing ammonia injection can improve the NOx removal effect, but too much ammonia injection will lead to the formation of ABS and the increase of deposition risk, the contradiction between these two aspects is amplified by ultra-low emissions and wide-load denitrification in many plants. Coordinating NOx control and reducing the impact of ABS on equipment are issues that the industry needs to solve urgently. In recent years, extensive research on ABS had been carried out deeply, consequently, there has been a relatively in-deepth knowledge foundation for ABS formation, formation temperature, deposition temperature, dew point temperature, decomposition behavior, etc., but the existing researches are insufficient to support the problem of ABS under full load denitrification completely resolved. Therefore, some analysis and detection methods related to ABS are reviewed in this paper, and the impact of ABS on SCR, air preheater and other equipment and the existing research results on reducing the impact of ABS are summarized also. It is hoped that this review will provide a reference for the industry to solve the problems of ABS that hinder wide-load denitrification and affect ultra-low emissions.

Experimental Investigation of Ammonia and Sulfur Deposition Characteristics in Rotary Air Preheater

2021 ◽  
Author(s):  
Rongze Gao ◽  
Haojia Sun ◽  
Limin Wang ◽  
Yufan Bu ◽  
Chao Wang ◽  
...  
Keyword(s):  
Flue Gas ◽  
Deposition Temperature ◽  
Sulfur Trioxide ◽  
Catalytic Reduction ◽  
Molar Ratio ◽  
Gaseous Ammonia ◽  
Condensation Temperature ◽  
Ash Deposition ◽  
Air Preheater ◽  
Operational Temperature

Abstract With the application of selective catalytic reduction (SCR) technology, the operation of rotary air preheaters is faced with a challenge, the fouling problem caused by ammonium bisulfate (ABS). In previous studies, within the operational temperature range of the preheater, the gaseous ammonia and sulfur trioxide (or H2SO4) in the flue gas can react to form ABS and ammonium sulfate (AS). The initial condensation temperature of ABS might be over predicted due to the effect of the formation of AS, which has a higher initial formation temperature than ABS. In this study, the effects of the deposition temperature, ammonia-sulfur molar ratio and molar product of inlet flue gas on the deposition characteristics of inducing ash deposition compounds were experimentally studied to provide guidance to prevent fouling and corrosion of rotary air preheaters. The results show that the main path to generate ABS is the reaction between H2SO4 and NH3. With the increase in the deposition temperature, the contents of NH4+ and SO42− in the sediments decrease continuously, and the proportion of AS deposition increases. On the contrary, with temperature decreasing, more ABS is deposited. When the molar ratio of ammo-sulfur in the inlet flue gas increases, the proportion of AS in the sediments increases, and the deposition rate also gradually increases. When the ammo-sulfur product in the inlet flue gas increases, the concentrations of both NH4+ and SO42− in the sediments increased in a nearly consistent trend. The variations of the ratio and deposition rates of the two ions in the sediments were not obvious. The ratio of NH4+ and SO42− remains at about 1.2, and the sediment is mainly ABS.

Enhanced Selective Non-Catalytic Reduction (SNCR) for Refinery Applications: Pilot-Scale Test Data With a Hydrogen Promoter

2011 ◽  
Author(s):  
Larry Swanson ◽  
Wei Zhou ◽  
David Moyeda ◽  
Christopher Samuelson
Keyword(s):  
Flue Gas ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Pilot Scale ◽  
Gas Temperature ◽  
Wide Range ◽  
Lower Temperature Range ◽  
Scale Test ◽  
Lower Temperature ◽  
Pilot Scale Test

Selective non-catalytic reduction technology (SNCR) is an effective and economical method of reducing NOX emissions for a wide range of industrial combustion systems. It is widely known that the traditional SNCR temperature window is centered around 1,200 to 1,255 K [1]. However, for some applications, the flue gas temperatures in boilers, oxidizers, and heaters range from 950 to 1150 K. At these lower temperatures, injection of an amine reagent into flue gas no longer actively reduces NOX, but instead passes through the system and exits as ammonia slip. Earlier studies have shown that at lower temperatures, hydrogen and other promoters can be added to the system to shift the SNCR window to a lower temperature range, enhancing or promoting SNCR NOX reduction performance [2–5]. This extended abstract describes pilot-scale test results for an enhanced SNCR process (ESNCR) that uses hydrogen as the SNCR promoter. The impacts of flue gas temperature, hydrogen concentration, CO concentration, and SO2 concentration on ESNCR NOX reduction performance are presented.

scholarly journals Analysis of Main Influencing Factors of the Wastewater Evaporation in Flue Duct

2020 ◽  
Vol 143 ◽  
pp. 02025
Author(s):  
Haowei Pan ◽  
Liang Zhang ◽  
Wei Li ◽  
Ning Gao ◽  
Yin Liu
Keyword(s):  
Flue Gas ◽  
Gas Flow ◽  
Droplet Diameter ◽  
Operating Cost ◽  
Simulation Method ◽  
Inlet Temperature ◽  
Factors Affecting ◽  
Two Factors ◽  
High Pollution ◽  
Desulfurization Wastewater

Desulfurization wastewater has the characteristics of small discharge and high pollution, and must be strictly treated. To obtain the main factors affecting the evaporation characteristics of desulfurization wastewater in boiler flue, a 600MW unit of a coal-fired power plant in China was taken as an example. According to the theory of fluid mechanics and heat transfer, the numerical simulation method was used. The results show that the way the nozzle is installed on the upper wall of the flue inlet can enhance the evaporation effect of the desulfurization wastewater. It is also revealed that the influence of the flue gas flow rate on the droplet evaporation effect is relatively small. The smaller droplet diameter and the higher flue gas inlet temperature will obviously enhance the evaporation effect of the droplets in the flue. However these two factors will increase the operating cost and reduce the boiler thermal efficiency. Therefore, the values of the droplet diameter and the flue gas inlet temperature need to be further determined by technical and economic comparison.

Study on Formation, Deposition and Fouling Prediction of Ammonium Bisulfate (ABS) at Air Preheater in Utility Boiler

2020 ◽  
Author(s):  
Liping Pang ◽  
Qiyuan Liang ◽  
Liqiang Duan
Keyword(s):  
Flue Gas ◽  
Time Data ◽  
Concentration Data ◽  
Air Preheater ◽  
Iterative Computation ◽  
Ammonia Slip ◽  
Actual Operation ◽  
The Finite Difference Method ◽  
Ammonium Bisulfate ◽  
Physical And Mathematical Models

Abstract The ammonium bisulfate (ABS) widely exists at air preheater. The ABS may deposit and foul at the heating elements of air preheater because of the chemical reaction between SO3 at flue gas side and ammonia slip from SCR excess injection. The heat transfer equation between flue gas side and air side is constructed and simplified using physical and mathematical models accordingly. The finite difference method is applied to solve numerically by means of iterative computation. Based on the NH3 and SO3 concentration data from the real time data in the actual operation and the discrete calculation of the temperature field, the Radian number (Ra) is used to evaluate the possibility of ABS fouling and the developing trend of heating elements at the air preheater. A 1000MW ultra supercritical boiler is selected as example. The ABS deposit area is simulated under different working conditions 100%BMCR, 75% BMCR and 50% BMCR. The possible ABS deposition and fouling is analyzed for operators to evaluate the risk of cold-end and hot-end heating elements plate at air preheater. As the working load decreases lower than 50%BMCR, the deposition and fouling position could extend to the hot-end area of heating elements at air preheater.

scholarly journals Effect of Flue Gases’ Corrosive Components on the Degradation Process of Evaporator Tubes

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3860
Author(s):  
Mária Hagarová ◽  
Milan Vaško ◽  
Miroslav Pástor ◽  
Gabriela Baranová ◽  
Miloš Matvija
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Gas Flow ◽  
Degradation Process ◽  
Flue Gases ◽  
Saturated Steam ◽  
Mineral Salts ◽  
Related Factors ◽  
Local Overheating ◽  
Inner Surface

Corrosion of boiler tubes remains an operational and economic limitation in municipal waste power plants. The understanding of the nature, mechanism, and related factors can help reduce the degradation process caused by corrosion. The chlorine content in the fuel has a significant effect on the production of gaseous components (e.g., HCl) and condensed phases on the chloride base. This study aimed to analyze the effects of flue gases on the outer surface and saturated steam on the inner surface of the evaporator tube. The influence of gaseous chlorides and sulfates or their deposits on the course and intensity of corrosion was observed. The salt melts reacted with the steel surface facing the flue gas flow and increased the thickness of the oxide layer up to a maximum of 30 mm. On the surface not facing the flue gas flow, they disrupted the corrosive layer, reduced its adhesion, and exposed the metal surface. Beneath the massive deposits, a local overheating of the inner surface of the evaporator tubes occurred, which resulted in the release of the protective magnetite layer from the surface. Ash deposits reduce the boiler’s thermal efficiency because they act as a thermal resistor for heat transfer between the flue gases and the working medium in the pipes. The effect of insufficient feedwater treatment was evinced in the presence of mineral salts in the corrosion layer on the inner surface of the tube.

scholarly journals Dependence of the Flue Gas Flow on the Setting of the Separation Baffle in the Flue Gas Tract

2021 ◽  
Vol 11 (7) ◽  
pp. 2961
Author(s):  
Nikola Čajová Kantová ◽  
Alexander Čaja ◽  
Marek Patsch ◽  
Michal Holubčík ◽  
Peter Ďurčanský
Keyword(s):  
Particulate Matter ◽  
Flue Gas ◽  
Gas Flow ◽  
Negative Impact ◽  
Combustion Process ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Combustion Of Solid Fuels

With the combustion of solid fuels, emissions such as particulate matter are also formed, which have a negative impact on human health. Reducing their amount in the air can be achieved by optimizing the combustion process as well as the flue gas flow. This article aims to optimize the flue gas tract using separation baffles. This design can make it possible to capture particulate matter by using three baffles and prevent it from escaping into the air in the flue gas. The geometric parameters of the first baffle were changed twice more. The dependence of the flue gas flow on the baffles was first observed by computational fluid dynamics (CFD) simulations and subsequently verified by the particle imaging velocimetry (PIV) method. Based on the CFD results, the most effective is setting 1 with the same boundary conditions as those during experimental PIV measurements. Setting 2 can capture 1.8% less particles and setting 3 can capture 0.6% less particles than setting 1. Based on the stoichiometric calculations, it would be possible to capture up to 62.3% of the particles in setting 1. The velocities comparison obtained from CFD and PIV confirmed the supposed character of the turbulent flow with vortexes appearing in the flue gas tract, despite some inaccuracies.

scholarly journals Ultrafast carbothermal reduction of silica to silicon using a CO2 laser beam

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Seok-Ho Maeng ◽  
Hakju Lee ◽  
Min Soo Park ◽  
Suhyun Park ◽  
Jaeki Jeong ◽  
...  
Keyword(s):  
Carbon Black ◽  
Laser Beam ◽  
Carbothermal Reduction ◽  
Gas Flow ◽  
Crystalline Silicon ◽  
Reduction Process ◽  
Reaction Chamber ◽  
Raman Shift ◽  
Influence Of Process Parameters ◽  
Laser Beam Intensity

AbstractWe report the extraction of silicon via a carbothermal reduction process using a CO2 laser beam as a heat source. The surface of a mixture of silica and carbon black powder became brown after laser beam irradiation for a few tens of seconds, and clear peaks of crystalline silicon were observed by Raman shift measurements, confirming the successful carbothermal reduction of silica. The influence of process parameters, including the laser beam intensity, radiation time, nitrogen gas flow in a reaction chamber, and the molar ratios of silica/carbon black of the mixture, on the carbothermal reduction process is explained in detail.

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