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.

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 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.

scholarly journals Experiment Comparison between Engineering Acid Dew Point and Thermodynamic Acid Dew Point

2018 ◽  
Vol 38 ◽  
pp. 04008 ◽  
Author(s):  
Jinghui Song ◽  
Hui Yuan ◽  
Jianhua Deng
Keyword(s):  
Flue Gas ◽  
Pipe Wall ◽  
Waste Heat ◽  
Coupling Effect ◽  
Dew Point ◽  
Air Preheater ◽  
Heat Utilization ◽  
Actual Operation ◽  
Waste Heat Utilization ◽  
Coal Type

in order to realize the accurate prediction of acid dew point, a set of measurement system of acid dew point for the flue gas flue gas in the tail of the boiler was designed and built, And measured at the outlet of an air preheater of a power plant of 1 000 MW, The results show that: Under the same conditions, with the test temperature decreases, Nu of heat transfer tubes, fouling and corrosion of pipe wall and corrosion pieces gradually deepened. Then, the measured acid dew point is compared with the acid dew point obtained by using the existing empirical formula under the same coal type. The dew point of engineering acid is usually about 40 ℃ lower than the dew point of thermodynamic acid because of the coupling effect of fouling on the acid liquid, which can better reflect the actual operation of flue gas in engineering and has certain theoretical guidance for the design and operation of deep waste heat utilization system significance.

Tangxian Jidong Cement Co., Ltd. SNCR DeNOx Engineering Practice

2013 ◽  
Vol 726-731 ◽  
pp. 2342-2346 ◽  
Author(s):  
Shao Hua Ling ◽  
Chang Yong Jing ◽  
Jing Ma ◽  
Li Juan Zhang
Keyword(s):  
Flue Gas ◽  
Reducing Agent ◽  
Engineering Practice ◽  
System Configuration ◽  
Process Characteristics ◽  
Detailed Explanation ◽  
Actual Operating ◽  
Ammonia Slip ◽  
Flue Gas Denitrification

Tang xian in Hebei Jidong Cement Co., Ltd. flue gas denitrification treatment works, the project uses ammonia as a reducing agent SNCR DeNOx technology. A detailed explanation of the the SNCR process characteristics and system configuration, The analysis for actual operating results of the engineering. The results show: After treatment NOx concentration is less than 200 mg/Nm3, Denitrification efficiency reach 72.82%, Ammonia slip less than 0.9mg/Nm3, Engineering put into operation, About a year reduces emission NOx 1430 tons.

Improving the Boiler Efficiency by Optimizing the Combustion Air

2015 ◽  
Vol 787 ◽  
pp. 238-242 ◽  
Author(s):  
R. Pachaiyappan ◽  
J. Dasa Prakash
Keyword(s):  
Heat Transfer ◽  
Water Temperature ◽  
Steam Generator ◽  
Air Temperature ◽  
Flue Gas ◽  
Maximum Heat ◽  
Air Preheater ◽  
Hot Air ◽  
Boiler Efficiency ◽  
Efficient Combustion

Air pre-heater and economizer are heat transfer surfaces in which air temperature and water temperature are raised by transferring heat from other media such as flue gas. Hot air is necessary for rapid combustion in the furnace and also for drying coal in milling plants. So an essential boiler accessory which serves this purpose is air pre-heater. The air pre-heater is not essential for operation of steam generator, but they are used where a study of cost indicates that money can be saved or efficient combustion can be obtained by their use. The decision for its adoption can be made when the financial advantages is weighed against the capital cost of heater. The efficiency of the boiler increases with the increase in the temperature of the combustion air used in the furnace. This is achieved by the increased temperature of the flue gas in the air preheater and economizer zone. This paper deals with the different ways to obtain the maximum heat from the flue gas travelling through the air preheater and the economizer zone to improve the boiler efficiency.

scholarly journals Combined NOx and NH3 Slip Reduction in a Stoker Boiler Equipped with the Hybrid SNCR + SCR System FJBS+

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8599
Author(s):  
Robert Wejkowski ◽  
Sylwester Kalisz ◽  
Przemysław Garbacz ◽  
Izabella Maj
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Full Range ◽  
Nox Reduction ◽  
Main Idea ◽  
Cost Effective ◽  
Combustion Products ◽  
Ammonia Removal ◽  
Ammonia Content ◽  
Ammonia Slip

The application of secondary NOx control methods in medium to low-capacity furnaces is a relatively new topic on the energy market and thus requires further research. In this paper, the results of full-scale research of SNCR and hybrid SNCR + SCR methods applied into a 29 MWth solid fuel fired stoker boiler is presented. The tests were performed for a full range of boiler loads, from 33% (12 MWth) to 103% (30 MWth) of nominal load. A novel SNCR + SCR hybrid process was demonstrated based on an enhanced in-furnace SNCR installation coupled with TiO2-WO3-V2O5 catalyst, which provides extra NOx reduction and works as an excess NH3 “catcher” as well. The performance of a brand-new catalyst was evaluated in comparison to a recovered one. The emission of NOx was reduced below 180 mg NOx/Nm3 at 6% O2, with ammonia slip in flue gas below 10 mg/Nm3. Special attention was paid to the analysis of ammonia slip in combustion products: flue gas and fly ash. An innovative and cost-effective method of ammonia removal from fly ash was presented and tested. The main idea of this method is fly ash recirculation onto the grate. As a result, ammonia content in fly ash was reduced to a level below 6.1 mg/kg.

scholarly journals Application and performance evaluation of desulfurization wastewater spray drying technology

2020 ◽  
Vol 143 ◽  
pp. 02029
Author(s):  
Zhang Shanshan ◽  
Wang Renlei ◽  
Tang Guorui ◽  
Dai YU
Keyword(s):  
Spray Drying ◽  
Flue Gas ◽  
Unit Load ◽  
Air Preheater ◽  
Mass Fractions ◽  
Denitrification Reactor ◽  
And Performance ◽  
Drying Technology ◽  
Gas Volume ◽  
Desulfurization Wastewater

In order to realize zero discharge of desulfurization wastewater, spray drying technology of desulfurization wastewater was used in 2x330MW unit of a power plant. Its principle was to use a rotary atomizer for atomization,and a part of hot flue gas was drawn from the SCR denitrification reactor and air preheater into the drying tower, the heat was used to evaporate the desulfurization wastewater in a spray drying tower. The salt in the waste water was mixed with the dust, which was collected and removed by the electric dust remover. Then the water vapor was mixed with the flue gas and finally enters the desulfurization tower.The field test was carried out under the condition that the unit load was 100% and the amount of desulfurization wastewater treated was 5.1m3/h.The results showed that the hot smoke gas volume of drying tower was about 64896m3/h, The smoke temperature at the inlet and outlet of the drying tower were 335℃ and 205℃ respectively,the moisture content of drying products was only 0.05%. The content of HCl in the flue gas at the inlet and outlet of the drying tower were 55mg/L and 195mg/L respectively, the mass fractions of Cl removal and Cl volatilization in desulfurization wastewater were 87.7% and 12.3% respectively. The increase of Cl content in the dried products had little effect on the utilization of fly ash.

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