Furnace Desulfurization Research Articles

Transformation of CFB boilers pollutant treatment strategies under China’s stricter requirements and the background of carbon neutrality (FBC24)

The 14th FYPP puts forward stricter requirements for pollutants control of CFB boilers, which are very difficult for the current flue gas treatment system to meet. Therefore, it is urgent to find a new way to control pollutants from CFB boilers. The most ideal way is to realize the low emissions of N2O/NOx/SO2 through flow pattern reconstruction, bed material catalysis and reaction, auxiliary desulfurization and denitration technology. The bed temperature can affect many aspects, such as combustion efficiency, desulfurization efficiency, NOx, N2O, etc. Therefore, an optimal operating range should be selected and kept stable. N2O and NOx come from fuel nitrogen and their emissions always show opposite trends. Compared with mature control techniques on NOx and SO2, N2O control technologies are less developed. Due to the coupling between NOx and N2O, it is recommended to remove N2O after co-combustion of bed material and fuel by catalytic method, and partially remove NOx and SO2 in the furnace on the premise of ensuring the combustion efficiency. The remaining NOx can be treated by creating a reductive atmosphere, flow pattern reconstruction or SNCR. SO2 can be treated with ultra-fine limestone or two-stage desulfurization process of desulfurization in furnace and CFB-FGD.

A Review on the Application of Circulating Fluidized Bed Fly Ash in Building Materials

Circulating fluidized bed (CFB)-based coal burning technology is a type of clean coal combustion technology. Owing to its characteristics of low temperature combustion and desulfurization in furnace, the CFB fly ash is quite different from ordinary fly ash. Based on the comprehensive understanding of physical and chemical characteristics of CFB fly ash, this review summarizes the research progress of the application of CFB fly ash in Portland cement, magnesium oxysulfate (MOS) cement, solid-waste–based cementitious material (SWCM), concrete, geopolymer, artificial aggregate, and other building materials. The study shows that CFB fly ash can improve the early physical and mechanical properties and reduce the drying shrinkage properties for cementitious materials. Its unique chemical composition endows it with good application performance in the MOS cement, geopolymer, and SWCM. However, unfavorable characteristics of CFB fly ash, such as loose and porous structure, self-hardening behavior, and expansibility greatly hinder its practical applications in building materials. Therefore, some measures, such as addition of rational water-reducing agent, ultrafine grinding, mixing of ordinary fly ash, controlling the dosage of CFB fly ash, and water-cement ratio, must be taken to improve the negative influence of CFB fly ash on the building materials, in order to expand its application range. This article summarizes the application and research status of CFB fly ash in building materials, aiming at further promoting the research studies on CFB fly ash resource utilization in building materials and improving the efficiency of CFB fly ash resource utilization.

Feasibility Study of Grinding Circulating Fluidized Bed Ash as Cement Admixture

With the widespread application of circulating fluidized bed (CFB) combustion technology, the popularity of CFB ash (CFBA) has increased dramatically and its production and large-scale utilization have become increasingly important. In the context of carbon neutrality peaking, using CFBA as a cement admixture as an effective method of resource utilization not only reduces the pressures caused by carbon emissions in the cement industry but also solves the environmental problems caused by CFBA depositing. However, the formation conditions of CFBA are worse than those of traditional pulverized coal boilers. CFB ash is the combustion product of coal at 850 °C–950 °C, and the characteristics of CFBA usually include a loose and porous structure with many amorphous substances. Furthermore, it has the disadvantages of large particle size, high water-demand ratio, and low activity index when it is directly used as a cement admixture. In this study, CFBA (including fly ash (CFBFA) and bottom ash (CFBBA)) produced by a CFB boiler without furnace desulfurization with limestone was used as a cement admixture material, and the effect of grinding on the fineness, water-demand ratio, and activity index of CFBA were studied. The experimental results showed that the grinding effect could significantly reduce the fineness and water-demand ratio of CFBA as a cement mixture and improve the activity index. With the increase in the grinding time, the water-demand ratio of CFBA first decreased and then increased. CFBBA ground for 10 min and CFBFA ground for 4 min can reduce the water-demand ratio of CFBA by up to 105% and increase the compressive strength of 28-day-old CFBA cement by 7.05%. The grinding process can ensure that CFBA meets the Chinese standards for a cement admixture and realize the resource utilization of CFBA.

Study on economic operating mode for combined desulfurization system of circulating fluidized bed unit

With the stricter emission regulation taking effect, most of circulating fluidized bed (CFB) power generation units operates with conventional desulfurization in CFB furnace and flue gas desulfurization (FGD) technology to meet the requirements of ultralow SO2 emission. Therefore, it is urgent to analyse operating cost of the combined desulfurization system and explore the low-cost operating mode for CFB units. In this paper, the operating cost model of combined desulfurization system was established, in which the influence of desulfurization in furnace on thermal efficiency of the CFB boiler was considered. Then, the operating cost of combined desulfurization system under different load conditions for a 300MW subcritical CFB unit was analysed, combined with measured data. The operating cost optimization result shows that, under different loads, when Ca/S is in the range of 0.4 to 0.5, the operating cost of combined desulfurization system reaches the minimum. In addition, as the unit load increases, the higher proportion of SO2 removal in FGD is required to achieve low-cost operating mode for CFB units.

Selection of ultra-low emission transformation scheme for 300MW CFB unit desulphurization system

Mature outside-desulfurization technology is supplied as an ultra-low emission transformation for meeting present emission standard.In order to explore a reasonable method to select the most economical transformation scheme of desulfurization system, a CFB boiler of 300MW class unit was taken as the research object. According to actual operation data and characteristics of different technical routes, a numerical model was set up, in which the cost caused by material consumption in desulfurization and denitrification and change of boiler efficiency was considered. The model was transformed into a single value function of ratio of calcium to sulfur in furnace. Through derivation, optimum proportion of joint desulfurization in and out furnace and comprehensive annual cost including initial investment, operation and maintenance of different schemes were obtained. The results show that for semi-dry desulphurization system outside furnace, the change of ratio of calcium to sulfur outside furnace has little influence on optimum ratio of desulphurization in furnace. When the ratio of calcium to sulfur outside furnace is 1.2∼2.0, optimum ratio of desulfurization in furnace is about 76%∼88%. According to this ratio, the ultra-low emission transformation scheme combining semi-dry desulphurization outside furnace and limestone injection in furnace is the most economical.

유동층보일러형 화력발전소의 석회석 활용 탈황기술 연구동향

Abstract This study investigated that status of domestic and international furnace desulfurization and desulfurization characteristics oflimestone for fluidized bed use depending on the technology for CFBC one of the CCPs. Limestone-based desulfurizing agentis one of the superior elements which are optimal at around 850-950 o C on high temperature desulfurization. And effectivenessof desulfurization process can be determined by the desulfurization experiment method such as diffusion reaction of the dia-phragm of the absorber surface, the size of the particles, the pores of the quantity, size and structure. And, desulfurization effi-ciency depending on geological and crystallographic properties and calcination process of limestone needs additional researchin the future.Key words : High temperature dry desulfurization, Circulating fluidized bed combustion (CFBC), Desulfurizating agent, Limestone, Calcium oxide · Received : July 17, 2015 · Revised : August 10, 2015 · Accepted : August 24, 2015Corresponding Author : Kae-Hong Cho (E-mail : khcho99@kilam.re.kr)Research Development office, Korea Institute of Limestone & Advanced Materials, Udoek-ri 63, Maepo-eup, Danyang-gun,Chungcheongbuk-do, 395-903 KoreaⓒThe Korean Institute of Resources Recycling. All rights reserved. This is an open-access article distributed under the termsof the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permitsunrestricted non-commercial use, distribution and reproduction in any medium, provided the original work is properly cited.

Analysis on the Oversize Blast Furnace Desulfurization and a Sulfide Capacity Prediction Model Based on Congregated Electron Phase

Through analyzed and regressed the actual productive desulfurization data from the oversize blast furnace (5500 m3) in north China, the relationship between the sulfur distribution parameters and the slag composition in actual production situation was investigated. As the slag and hot metal phases have their own balance sulfur content or sulfur partial pressure in gas phase, respectively, the non-equilibrium of sulfur among gas, slag, and metal phases leads to the transmission and distribution of sulfur. Combined with sulfur transmission reactions between gas, slag and metal phases, C/CO pairs equilibrium, and Wagner model, the measured sulfide capacity can be acquired using sulfur distribution ratio, sulfur activity coefficient, and oxygen activity in hot metal. Based on the theory of congregated electron phase, a new sulfide capacity prediction model (CEPM) has been developed, which has a good liner relationship with the measured sulfide capacity. Thus, using the burden structure for BF, the ironmaking slag composition can be obtained simply and can be used to reliably predict the ironmaking slag desulfurization ability a few hours later after charging under a certain temperature by CEPM.

The Optimization to Control System of Desulfurization in Furnace of 300MW CFB Boiler

This paper contraposes 300MW CFB boiler of Shanxi certain coal-fired power plant, then optimize the control system of desulfurization and remake limestone transmission system. Collect the signal to establish knowledge base for judging starting or stalling control of feeding machine through lots of experiments. Adopt feedback control strategy to adjust the speed of feeding machine. Achieve the purpose of automatically controling the starting or stalling of feeding machine and the speed of feeding machine finally.

Experimental Research on Hybrid Strategy and Desulfurization for White Mud and Coal Slurry

White mud is a kind of solid waste from the papermaking process, because of the high pH value and desulfurization material, it can be used as a desulfurization agent. Coal slury is the waste from the coal washing process and generally be used as fuel. This paper studies the hybrid method for white mud and coal slurry to be transported by pipeline, and the furnace desulfurization effect with the mixture. Rheological properties of coal slury and white mud was analyzed, and then based on the rheological data the coal slurry, white mud and water mixed strategy was obtained. By altering calcium sulfur ratio and operation parameters of boiler, fluidizing bed boiler desulphurization effect was tested with the mixture, the economic analysis was also performed through comparision of operational cost. The result shows that the proposed hybrid method is not only relatively simple, but also has the characteristics of good desulfurization effect, high desulfurization efficiency, and good economy. The study has important guiding meaning for desulphurization of coal slurry fluidized bed boiler.

Characteristics of Flue Gases and Ash in Oxygen-Blown Pulverized Coal Combustion

A new coal combustion technology for a large-scale power plant is required to be applicable to various kinds of coal. An oxygen-blown pulverized coal combustion experiment was investigated with a bench scale apparatus to understand such characteristics as the combustion efficiency, NOx concentration, conversion from fuel-N, the unburned fraction and composition of mineral matter in the collected ash. The experiment was conducted in a down-fired, cylindrical and vertical furnace. The primary oxygen is injected into the ejector to carry coal particles to the burner, and the swirled secondary one is fed through an annulus. The CO2 concentration in flue gas was much higher than that of air–coal combustion, and the value was eight out of ten. The results made a feasible condition for CO2 separation and sequestration. The NOx emission was ranged in concentrations from 1650 to 1800 ppm in the complete combustion region. The NOx concentration was much higher, however the NOx conversion ratio was about the same level as the case of air combustion. The decrease of low-boiling component such as Na, Mg, K and Ca was identified because the flame temperature of the oxygen-blown coal combustion was achieved about 3000 K. We suggested the vaporized calcium components in the fly ash have a potential of the furnace desulfurization and the effect of SOx attack to the heat exchanger was inhibited.