循环床燃烧、脱硫及灰渣利用

前言循环床锅炉由于燃烧效率高、低污染排放和燃料适应性强,自1975年西德鲁奇公司(Lurgi)首次推出以来,作为一种新的燃烧方式受到了普遍关注,在一些主要发达国家中都得到了迅速发展,不少大公司都先后推出了自己型式的产品,如:鲁奇公司。

法国循环床燃烧技术的新进展

简述了法国电力公司、法国锅炉公司新近发展的循环床燃烧技术的使用现状及脱硫效果。

SO_2 emission characteristics from co-firing of petroleum coke and coal in circulating fluidized bed

Combustion and sulfur retention experiments of mixed fuel of petroleum cokeand coal were conducted on a pilot-scale circulating fluidized bed (CFB) combustor with the thermalinput of 0. 6 MW. The effects of several parameters, such as the primary air percentage, excess aircoefficient, bed temperature, Ca/S molar ratio and mass ratio of petroleum coke to coal on SO_2emission were verified. Experimental results show that when the ratio of petroleum coke to coal inthe mixed fuel increases, the SO_2emission increases. The maximum SO_2 emission appears when purecoke burns. The SO_2 concentration in flue gas reduces with the increase in the primary airpercentage, excess air coefficient and Ca/S molar ratio for all kinds of fuel mixtures. Therangebetween 830 t and 850 t is the optimal temperature for sulfur retention during co-firing ofpetroleum coke and coal with the mass ratio R of 1 and 3 in CFB.

I MWth Test Facilities for Circulating Fluidized Bed Combustion

This paper presents the technical parameters and features of 1 MWth test facilities for circulating fluidized bed combustion (CFBC) at Thermal Power Research Institute (TPRI) of State Power Corporation (SP), introduces the test items that can be proceeded and trial combustion projects completed. The development status of CFBC technologies abroad and the level of China in this field are also introduced in the paper.

Adsorption properties of CFBC ash-cement pastes as compared with PCC fly ash-cement pastes

Circulating fluidized bed combustion （CFBC） ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash-cement pastes were studied, and ordinary pulverized coal combustion （PCC） fly ash-cement pastes were used as control. The water-adsorption and superplasticizer （SP）-adsorption properties of the pastes were evaluated by water demand and UV-visible absorption spectroscopy respectively. The results show that CFBC ash-cement system has greater compressive strength as compared with PCC fly ash-cement system at a given curing age, although the water demand of the former is significantly higher than that of the latter. CFBC ash-cement pastes possess higher adsorption ability of aliphatic SP than PCC fly ash-cement pastes and the adsorption amount increases with an increase in ash replacement ratio. CFBC ash- cement pastes exhibit lower workability with higher slump loss. It is concluded that CFBC ash can be potentially used as supplementary cementitious material in concrete production, but the mix design of CFBC ash concrete needs to be appropriately adjusted. It is suggested that CFBC ash is used for the production of the concrete needing low flowability.

A novel suspension-floating-circulating fluidized combustion technology for coal slurry

A novel suspension-floating-circulating fluidized combustion technology is proposed for burning coal slurry fuel in traditional circulating ftuidized bed boilers （CFBB）. This technology can solve some existing problems in large- capacity CFBB burning coal slurry. The principles of the suspension-floating-circulating fluidized combustion technology were introduced in detail in this paper. A 130 t/h CFBB was retrofitted based on the technology, and the retrofitted system mainly includes a long-distance transport sub-system, a bed-material conveying sub-system with a wind-seal device invented by the authors, a superheater thermoregulation device using a novel temperature regulator, a return loop flu- idization facility, and a pneumatic ash conveying sub-system with sealed pump. The achieved performance of the retro- fitted CFBB shows that the thermal efficiency is 89.83 %, the combustion efficiency is 96.24 %, and the blending proportion of slurry is 94 %.

Strength and thermal behavior of low weight foam geopolymer using circulating fluidized bed combustion fly ash

A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agent and different Si O2/Al2O3 molar ratios of 3.1, 3.4, and 3.8. The mechanical, thermo-physical properties and microstructure of the foam geopolymers before and after exposure to elevated temperature of 800, 1000, and 1200 ℃ were investigated. The specimen with Si O2/Al2O3 molar ratio of 3.8 exhibits the highest compressive strength, better microstructure and dimension stability before and after firing. Carnegeite, nepheline, and zeolite crystalline phases appearing after exposure may contribute to the good post-exposure strength. Low weight foam geopolymer using CFA can increase strength and maintain higher stability as high as 1000 ℃.

Conversion of Fuel-N to N2O and NOx during Coal Combustion in Combustors of Different Scale

With focus on investigating the effect of combustor scale on the conversion of fuel-N to NOx and N20, experiments are carried out in three combustors, including single coal particle combustion test rig, laboratory scale circulating fluidized-bed boiler （CFB） and full scale CFB in this work. For single coal particle combustion, the majority of f-uel-N （65%-82%） is released as NOx, while only a little （less than 8%） fuel-N yields N20. But in labora- tory scale CFB, the conversion of fuel-N to N20 is increases, but the conversion of fuel-N to NOx is quite less than that of single coal particle combustion. This is because much char in CFB can promote the NOx reduction by in- creasing N20 formation. In full scale CFB, both of the conversion of fuel-N to NOx and the conversion of fuel-N to N20 are smaller than laboratory scale CFB.

A Revised CFB Wall-to-suspension Heat Transfer Model

Based on the Cluster Renewal Model of the particle motion in a CFB riser, a revised heat transfer model is developed, which introduces the latest research results of the hydrodynamics of the suspension flow in CFB. This model divides the heat transfer into two parts, which are due to the transient heat conduction by the covered clusters and the convection between the uncovered wall and the dispersed phase. Radiation at high temperature is regarded as being additive. The fraction of the covered wall by clusters is revised by a new formula, which is a function of the operating condition and the particle properties. The radiation between the dispersed phase and the uncovered wall includes not only the direct radiation to the uncovered wall, but also the radiation to the clusters and then reflected to the uncovered wall. Calculation was carried out for the CFB heat transfer model. The results were compared with the published typical experimental data of other researchers and showed a good agreement between them.

循环流化床锅炉在河南省的应用及存在问题的探讨

循环流化床（CFB）燃烧技术是新一代高效低污染燃烧技术。河南省在建和立项的410t/h以上的CFB锅炉已10台。本文针对CFB锅炉运行中存在的问题如磨损、结焦、飞灰含碳量高等从设计环节入手进行了分析，并提出完善化措施，以期对CFB锅炉的运行提供一定的指导作用。

The Simulation of Influence of Different Coals on the Circulating Fluidized Bed Boiler's Combustion Performance

The combustion performance of the boiler largely depends on the coal type. Lots of experimental research shows that different fuels have different combustion characteristics. It is obvious that fuel will change the whole operating performance of Circulating Fluidized Bed Combustion (CFBC). We know even in a pilot-scale running boiler, the measurement of some parameters is difficult and costly. Therefore, we developed the way of simulation to evaluate the combustion performance of Chinese coals in CFB. The simulation results show that, different coals will result in different coal particle diameter and comminution depending on their mineral component and the change will affect the distribution of ash in CFBC system. In a word, the computational results are in accordance with experimental results qualitatively but there are some differences quantitatively.

Research and Development on PFBC-CC in China and Jiawang Pilot Plant Project

Pressurized Fluidized Bed Combustion(PFBC) is recognized as an advanced coal-fired technology which can improve efficiency in combined cycle scheme and reduce environmental pollution. Progressive status on PFBC-CC in China is presented in this paper. Test results on a 1 MWt bench scale experimental PFBC facility is reviewed briefly. Based on retrofitting of an old steam power plant located at Jiawang,a project to construct a PFBC-CC pilot plant is under way. Designed capacity of the pilot plant is about 15 MWe, 3 MWe from gas cycle and 12 MWe from steam cycle. The system configuration, main design parameters, estimated technical performance as well as construction schedule of the pilot plant are described. The bright future for PFBC-CC in China is also indicated.

Experimental Study on Combustion Characteristics and NOX Emissions of Pulverized Anthracite Preheated by Circulating Fluidized Bed

A 30 kW bench-scale rig of pulverized anthracite combustion preheated by a circulating fluidized bed （CFB） was developed. The CFB riser has a diameter of 90 mm and a height of 1,500 mm. The down-fired combustion chamber （DFCC） has a diameter of 260 mm and a height of 3,000 mm. Combustion experiments were carded out using pulverized anthracite with 6.74% volatile content. This low volatile coal is difficult to ignite and burn out. Therefore, it requires longer burnout time and higher combustion temperature, which results in larger NOx emis- sions. In the current study, important factors that influence the combustion characteristics and NOx emissions were investigated such as excess air ratio, air ratio in the reducing zone, and fuel residence time in the reducing zone. Pulverized anthracite can be quickly preheated up to 800~C in CFB when the primary air is 24% of theo- retical air for combustion, and the temperature profile is uniform in DFCC. The combustion efficiency is 94.2%, which is competitive with other anthracite combustion technologies. When the excess air ratio ranges from 1.26 to 1.67, the coal-N conversion ratio is less than 32% and the NOx emission concentration is less than 371 mg/m^3 （@6% O2）. When the air ratio in the reducing zone is 0.12, the NOx concentration is 221 mg/m^3 （@6% O2）, and the coal-N conversion ratio is 21%, which is much lower than that of other boilers.