Development and application of the design principle of fluidization state specification in CFB coal combustion

Cai, Runxia; Zhang, Hai; Zhang, Man; Yang, Hairui; Lyu, Junfu; Yue, Guangxi

doi:10.1016/j.fuproc.2018.02.009

Cited by 81 publications

(20 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A framework for identifying parameters associated with hydrodynamics has been presented by Xu and Gao [11]. The effects that different operating conditions have on the hydrodynamics can be found in the work presented by Wang et al [12], where efforts on identifying the fluidization state in CFBs have been presented by Cai et al [13]. The different types of modeling approaches presented above highlight the achievements when considering the combustion of coal, where such methods can be applied to the combustion of biomass and waste.…”

Section: Modelingmentioning

confidence: 99%

Waste Fuel Combustion: Dynamic Modeling and Control

2018

View full text Add to dashboard Cite

The focus of this study is to present the adherent transients that accompany the combustion of waste derived fuels. This is accomplished, in large, by developing a dynamic model of the process, which can then be used for control purposes. Traditional control measures typically applied in the heat and power industry, i.e., PI (proportional-integral) controllers, might not be robust enough to handle the the accompanied transients associated with new fuels. Therefore, model predictive control is introduced as a means to achieve better combustion stability under transient conditions. The transient behavior of refuse derived fuel is addressed by developing a dynamic modeling library. Within the library, there are two models. The first is for assessing the performance of the heat exchangers to provide operational assistance for maintenance scheduling. The second model is of a circulating fluidized bed block, which includes combustion and steam (thermal) networks. The library has been validated using data from a 160 MW industrial installation located in Västerås, Sweden. The model can predict, with satisfactory accuracy, the boiler bed and riser temperatures, live steam temperature, and boiler load. This has been achieved by using process sensors for the feed-in streams. Based on this model three different control schemes are presented: a PI control scheme, model predictive control with feedforward, and model predictive control without feedforward. The model predictive control with feedforward has proven to give the best performance as it can maintain stable temperature profiles throughout the process when a measured disturbance is initiated. Furthermore, the implemented control incorporates the introduction of a soft-sensor for measuring the minimum fluidization velocity to maintain a consistent level of fluidization in the boiler for deterring bed material agglomeration.

show abstract

Section: Modelingmentioning

confidence: 99%

Waste Fuel Combustion: Dynamic Modeling and Control

2018

View full text Add to dashboard Cite

show abstract

“…The effect of fluidization state optimization on combustion efficiency and pollutant emission in the CFB boiler has also been studied [8,9]. The fluidization state specification (FSS) design principle [10] can be used for saving energy consumption, improving combustion efficiency, and achieving ultra-low NO x and SO 2 emission [11][12][13]. Change in the bed pressure drop and size distribution of feeding coal particles directly influences the solids concentration profile and, therefore, affect the heat transfer and reaction.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Fluidization State of a Circulating Fluidized Bed Boiler for Economical Operation

2020

Self Cite

View full text Add to dashboard Cite

To reduce the auxiliary power consumption and improve the reliability of large-scale circulating fluidized bed (CFB) boilers, we developed energy-saving CFB combustion technology based on the fluidization state re-specification. A calculation model of coal comminution energy consumption was used to analyze the change in comminution energy consumption, and a 1D CFB combustion model was modified to predict the operation parameters under the fluidization state optimization conditions. With a CFB boiler of 480 t/h, the effect of fluidization state optimization on the economical operation was analyzed using the above two models. We found that combustion efficiency presents a nonmonotonic trend with the change in the bed pressure drop and feeding coal size. There are an optimal bed pressure drop and a corresponding feeding coal size distribution, under which the net coal consumption is the lowest. Low bed pressure drop operation achieved by reducing the coal particle size is not beneficial to SO2 and NOx emission control, and the pollutant control cost increases. The effect of fluidization state optimization on the gross cost of power supply can be calculated, and the optimal bed pressure drop can be obtained.

show abstract

“…Limestone is widely used for SO 2 capture in circulating fluidized bed (CFB) boilers for its low price and availability [1,2]. Under air combustion conditions, limestone involves first calcination to the porous CaO, and then the reaction with sulfur containing gas to CaSO 4 [3].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, it was considered that the optimum sorbent particle size should be close to the circulating ash for a longer residence time and a relatively higher reaction rate. Nevertheless, recent industrial practices have found that fine and even ultrafine (<10 μm) limestones can realize a high SO 2 capture efficiency with a low Ca/S molar ratio [2,18], so it is meaningful to investigate the optimum sorbent particle size under different conditions. Among all the influencing factors for the particle size optimization, the reactivity at low SO 2 concentrations is most significant.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Limestone Particle Size on the Sulfation Reactivity at Low SO2 Concentrations Using a LC-TGA

Cai

Huang

et al. 2019

Materials

Self Cite

View full text Add to dashboard Cite

Limestone particle size has a crucial influence on SO2 capture efficiency, however there are few studies on the sulfation reactivity, which covers a broad range of particle sizes at low SO2 concentrations. In this paper, a large-capacity thermogravimetric analyzer (LC-TGA) was developed to obtain the sulfur removal reaction rate under a wide range of particle sizes (3 μm–600 μm) and SO2 concentrations (250 ppm–2000 ppm), and then compared with the results of a traditional fixed bed reactor and a commercial TGA. The experimental results showed that the LC-TGA can well eliminate the external mass transfer and obtain a better measurement performance. Both the final conversion and the reaction rate reduced with the decreasing of SO2 concentration, but ultrafine limestone particles still showed the good sulfation reactivity even at 250 ppm SO2. An empirical sulfation model was established based on the experimental results, which can well predict the sulfation process of different limestone particle sizes at low SO2 concentrations. The model parameters have a strong negative correlation against the particle size, and the fit of the reaction order of SO2 was found to be about 0.6. The model form is very simple to incorporate it into available fluidized bed combustion models to predict SO2 emission.

show abstract

Development and application of the design principle of fluidization state specification in CFB coal combustion

Cited by 81 publications

References 66 publications

Waste Fuel Combustion: Dynamic Modeling and Control

Waste Fuel Combustion: Dynamic Modeling and Control

Optimization of Fluidization State of a Circulating Fluidized Bed Boiler for Economical Operation

Effects of the Limestone Particle Size on the Sulfation Reactivity at Low SO2 Concentrations Using a LC-TGA

Contact Info

Product

Resources

About