scholarly journals Investigation of Ash Deposition Dynamic Process in an Industrial Biomass CFB Boiler Burning High-Alkali and Low-Chlorine Fuel

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1092
Author(s):  
Hengli Zhang ◽  
Chunjiang Yu ◽  
Zhongyang Luo ◽  
Yu’an Li
Keyword(s):  
Gas Flow ◽  
Circulating Fluidized Bed ◽  
Deposition Process ◽  
Biomass Combustion ◽  
Ash Deposition ◽  
Biomass Ash ◽  
Cfb Boiler ◽  
Third Stage ◽  
Ash Deposit ◽  
High Alkali

The circulating fluidized bed (CFB) boiler is a mainstream technology of biomass combustion generation in China. The high flue gas flow rate and relatively low combustion temperature of CFB make the deposition process different from that of a grate furnace. The dynamic deposition process of biomass ash needs further research, especially in industrial CFB boilers. In this study, a temperature-controlled ash deposit probe was used to sample the deposits in a 12 MW CFB boiler. Through the analysis of multiple deposit samples with different deposition times, the changes in micromorphology and chemical composition of the deposits in each deposition stage can be observed more distinctively. The initial deposits mainly consist of particles smaller than 2 μm, caused by thermophoretic deposition. The second stage is the condensation of alkali metal. Different from the condensation of KCl reported by most previous literatures, KOH is found in deposits in place of KCl. Then, it reacts with SO2, O2 and H2O to form K2SO4. In the third stage, the higher outer layer temperature of deposits reduces the condensation rate of KOH significantly. Meanwhile, the rougher surface of deposits allowed more calcium salts in fly ash to deposit through inertial impact. Thus, the elemental composition of deposits surface shows an overall trend of K decreasing and Ca increasing.

scholarly journals Investigation of ash deposition dynamic process in an industrial biomass CFB boiler burning high alkali and chlorine fuel

RSC Advances ◽  
2020 ◽  
Vol 10 (36) ◽  
pp. 21420-21426
Author(s):  
Hengli Zhang ◽  
Chunjiang Yu ◽  
Zhongyang Luo
Keyword(s):  
Dynamic Process ◽  
Deposition Process ◽  
Ash Deposition ◽  
Cfb Boiler ◽  
High Alkali

Analysis of multiple deposits with different deposition times, piecing together the whole deposition process in 50 MW biomass CFB boiler.

scholarly journals Ash deposition behavior of a high-alkali coal in circulating fluidized bed combustion at different bed temperatures and the effect of kaolin

RSC Advances ◽  
2018 ◽  
Vol 8 (59) ◽  
pp. 33817-33827 ◽  
Author(s):  
Yanquan Liu ◽  
Leming Cheng ◽  
Jieqiang Ji ◽  
Qinhui Wang ◽  
Mengxiang Fang
Keyword(s):  
Fluidized Bed ◽  
Combustion Temperature ◽  
Circulating Fluidized Bed ◽  
Ash Deposition ◽  
Fluidized Bed Combustion ◽  
Deposition Behavior ◽  
Zhundong Coal ◽  
High Alkali ◽  
Circulating Fluidized Bed Combustion

This work reports the influence of combustion temperature on the ash deposition of Zhundong coal in a CFB, and evaluates the effect of kaolin.

Pilot-scale combustion studies with kraft lignin in a powder burner and a CFB boiler

TAPPI Journal ◽  
2010 ◽  
Vol 9 (6) ◽  
pp. 24-30 ◽  
Author(s):  
NIKLAS BERGLIN ◽  
PER TOMANI ◽  
HASSAN SALMAN ◽  
SOLVIE HERSTAD SVÄRD ◽  
LARS-ERIK ÅMAND
Keyword(s):  
Circulating Fluidized Bed ◽  
Black Liquor ◽  
Chloride Content ◽  
Pilot Scale ◽  
High Energy ◽  
Kraft Lignin ◽  
High Energy Density ◽  
Alkali Chloride ◽  
Cfb Boiler ◽  
Solid Biofuel

Processes have been developed to produce a solid biofuel with high energy density and low ash content from kraft lignin precipitated from black liquor. Pilot-scale tests of the lignin biofuel were carried out with a 150 kW powder burner and a 12 MW circulating fluidized bed (CFB) boiler. Lignin powder could be fired in a powder burner with good combustion performance after some trimming of the air flows to reduce swirl. Lignin dried to 10% moisture content was easy to feed smoothly and had less bridging tendencies in the feeding system than did wood/bark powder. In the CFB boiler, lignin was easily handled and cofired together with bark. Although the filter cake was broken into smaller pieces and fines, the combustion was not disturbed. When cofiring lignin with bark, the sulfur emission increased compared with bark firing only, but most of the sulfur was captured by calcium in the bark ash. Conventional sulfur capture also occurred with addition of limestone to the bed. The sulfur content in the lignin had a significantly positive effect on reducing the alkali chloride content in the deposits, thus reducing the high temperature corrosion risk.

scholarly journals Investigation on influences of loose gas on gas-solid flows in a circulating fluidized bed (CFB) reactor using full-loop numerical simulation

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Pengju Huo ◽  
Xiaohong Li ◽  
Yang Liu ◽  
Haiying Qi
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Gas Flow ◽  
Circulating Fluidized Bed ◽  
Separation Efficiency ◽  
Circulation Rate ◽  
Solid Mass ◽  
Gas Flow Rate ◽  
Gas Leakage ◽  
Mass Circulation

AbstractThe influences of loose gas on gas-solid flows in a large-scale circulating fluidized bed (CFB) gasification reactor were investigated using full-loop numerical simulation. The two-fluid model was coupled with the QC-energy minimization in multi-scale theory (EMMS) gas-solid drag model to simulate the fluidization in the CFB reactor. Effects of the loose gas flow rate, Q, on the solid mass circulation rate and the cyclone separation efficiency were analyzed. The study found different effects depending on Q: First, the particles in the loop seal and the standpipe tended to become more densely packed with decreasing loose gas flow rate, leading to the reduction in the overall circulation rate. The minimum Q that can affect the solid mass circulation rate is about 2.5% of the fluidized gas flow rate. Second, the sealing gas capability of the particles is enhanced as the loose gas flow rate decreases, which reduces the gas leakage into the cyclones and improves their separation efficiency. The best loose gas flow rates are equal to 2.5% of the fluidized gas flow rate at the various supply positions. In addition, the cyclone separation efficiency is correlated with the gas leakage to predict the separation efficiency during industrial operation.

Performance evaluation of a supercritical circulating fluidized bed boiler for power generation under flexible operation

2021 ◽  
pp. 095765092199396
Author(s):  
Matteo Bruzzone ◽  
Silvia Ravelli
Keyword(s):  
Power Generation ◽  
Fluidized Bed ◽  
High Performance ◽  
Circulating Fluidized Bed ◽  
Thermal Power ◽  
Rankine Cycle ◽  
Hard Coal ◽  
Cfb Boiler ◽  
Power Cycles ◽  
Commercial Code

It is well known that the Łagisza power plant in Poland is the world’s first supercritical circulating fluidized bed (CFB) boiler, whose commercial operation started on June 2009. It has attracted a great deal of interest and operational data are publicly available, therefore it has been chosen as the object of the present study aimed at assessing load and fuel flexibility of supercritical CFB plants. First, the thermal cycle was modelled, by means of the commercial code Thermoflex®, at nominal and part load conditions for validation purposes. After having verified the validity of the applied modelling and simulation tool, the advantage of having supercritical steam combined with CFB boiler over subcritical steam and pulverized coal (PC) boiler, respectively, was quantified in terms of electric efficiency. As a next step, the designed fuel, i.e. locally mined hard coal, was replaced with biomass: 100% biomass firing was taken into account in the case of subcritical CFB boiler whereas the maximum share of biomass with coal was set at 50% with supercritical CFB boiler, consistently with the guidelines provided by the world leading manufacturers of CFB units. A broad range of biomass types was tested to conceive mixtures of fuel capable of preserving quite high performance, despite the energy consumption in pretreatment. However, the overall efficiency penalty, due to biomass co-firing, was found to potentially undermine the benefit of supercritical steam conditions compared to conventional subcritical power cycles. Indeed, the use of low-quality biomass in thermal power generation based on steam Rankine cycle may frustrate efforts to push the steam cycle boundaries.

Experimental and Numerical Analysis of the Powder Flow in a Multi-Channel Coaxial Nozzle of a Direct Metal Deposition System

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Piyush Pant ◽  
Dipankar Chatterjee ◽  
Sudip Kumar Samanta ◽  
Aditya Kumar Lohar
Keyword(s):  
Gas Flow ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Deposition Process ◽  
Metal Deposition ◽  
Direct Metal Deposition ◽  
Powder Flow ◽  
Coaxial Nozzle ◽  
Proposed Model ◽  
Blown Powder

Abstract The work explores the powder transport process, using numerical simulation to address the dynamics of the powder flow in an in-house built multi-channel coaxial nozzle of a direct metal deposition (DMD) system. The fluid turbulence is handled by the standard k–ɛ and k–ω turbulence models, and the results are compared in order to predict their suitability. An image-based technique using CMOS camera is adopted to determine the powder flow characteristics. The model is validated with the in-house experimental results and verified available results in the literature. The findings of this work confirms the application of the k–ω model for powder gas flow investigations in blown powder additive manufacturing (AM) processes due to its better predictive capability. The proposed model will assist in simulating the direct metal deposition process.

scholarly journals Feasibility Study of Using Carbide Slag as In-Bed Desulfurizer in Circulating Fluidized Bed Boiler

2019 ◽  
Vol 9 (21) ◽  
pp. 4517 ◽  
Author(s):  
Zhong Huang ◽  
Jimiao Long ◽  
Lei Deng ◽  
Defu Che
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Separation Efficiency ◽  
Molar Fraction ◽  
So2 Emissions ◽  
Cfb Boiler ◽  
Carbide Slag ◽  
Desulfurization Efficiency ◽  
Sintering Resistance ◽  
Pilot Tests

Carbide slag is a waste residue during the production of acetylene. Due to its high content of Ca(OH)2, carbide slag becomes a potential alternative to limestone as the in-bed desulfurizer of circulating fluidized bed (CFB) boilers. In this study, the calcination and sulfation characteristics of carbide slag were investigated by three different facilities, thermogravimetric analyzer (TGA), 1 MWth pilot CFB boiler, and 690 t·h−1 CFB boiler. Pore structures and sulfation behaviors of carbide slag and limestone were investigated for the sake of comparison. The results showed that carbide slag has a lower calcination temperature than limestone. Its calcined product has a better pore structure and desulfurization activity. The carbide slag exhibited a higher desulfurization efficiency than the limestone in the pilot tests. The SO2 emission concentration showed a downward trend with the increase of molar fraction of carbide slag in the desulfurizer. Meanwhile, carbide slag had a better sintering-resistance property, which makes it possible to effectively reduce SO2 emissions even at high combustion temperatures (>910 °C). While the field test results were similar to that of the pilot tests, the desulfurization efficiency of carbide slag with the same Ca/S mole ratio was higher than that of limestone. The fine size of carbide slag particles and the lower separation efficiency of the cyclone on the 690 t·h−1 boiler left the carbide slag with insufficient residence time in the furnace. Therefore, it is necessary to ensure a high separation efficiency of the cyclone if the carbide slag is used as an alternative desulfurizer in furnace.

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