Chemical looping combustion of coal in interconnected fluidized beds

Chemical looping combustion is the indirect combustion by use of oxygen carrier. It can be used for CO2 capture in power generating processes. In this paper, chemical looping combustion of coal in interconnected fluidized beds with inherent separation of CO2 is proposed. It consists of a high velocity fluidized bed as an air reactor in which oxygen carrier is oxidized, a cyclone, and a bubbling fluidized bed as a fuel reactor in which oxygen carrier is reduced by direct and indirect reactions with coal. The air reactor is connected to the fuel reactor through the cyclone. To raise the high carbon conversion efficiency and separate oxygen carrier particle from ash, coal slurry instead of coal particle is introduced into the bottom of the bubbling fluidized bed. Coal gasification and the reduction of oxygen carrier with the water gas take place simultaneously in the fuel reactor. The flue gas from the fuel reactor is CO2 and water. Almost pure CO2 could be obtained after the con- densation of water. The reduced oxygen carrier is then returned back to the air reactor, where it is oxidized with air. Thermodyanmics analysis indicates that NiO/Ni oxygen carrier is the optimal one for chemical looping combustion of coal. Simulation of the processes for chemical looping combustion of coal, including coal gasification and reduction of oxygen carrier, is carried out with Aspen Plus software. The effects of air reactor temperature, fuel reactor temperature, and ratio of water to coal on the composition of fuel gas, recirculation of oxygen carrier par- ticles, etc., are discussed. Some useful results are achieved. The suitable tem- perature of air reactor should be between 1050―1150℃and the optimal temperature of the fuel reactor be between 900―950℃.     

Combustion behavior and influence mechanism of CO on iron ore sintering with flue gas recirculation

The properties of circulating gas have a significant effect on sintering with flue gas recirculation, and the influence of CO in sintering process was investigated. The results show that the post-combustion of CO conducts in sinter zone when flue gas passes through the sintering bed, which releases much heat and reduces the consumption of solid fuel. The ratio of coke breeze can be reduced from 5% to 4.7% with 2% CO in circulating flue gas. In addition, with the increase of CO content in circulating flue gas, the combustion efficiency of fuel is improved, and the flame front is increased slightly while still matches with the heat transfer front. These are beneficial to increasing the maximum temperature and prolonging the high temperature duration, especially in the upper layer of sintering bed. As a consequence, the productivity, vertical sintering velocity and quality of sinter are improved.     

Slagging characteristics of molten coal ash on silicon-aluminum combustion liners of boiler

In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.     

Thermo economic evaluation of oxy fuel combustion cycle in Kazeroon power plant considering enhanced oil recovery revenues简

Oxy fuel combustion and conventional cycle （currently working cycle） in Kazeroon plant are modeled using commercial thermodynamic modeling software. Economic evaluation of the two models regarding the resources of transport and injection of carbon dioxide into oil fields at Gachsaran for enhanced oil recovery in the various oil price indices is conducted and indices net present value （NPV） and internal rate of return on investment （IRR） are calculated. The results of the two models reveal that gross efficiency of the oxy fuel cycle is more than reference cycle （62% compared to 49.03%）, but the net efficiency is less （41.85% compared to 47.92%） because of the high-energy consumption of the components, particularly air separation unit （ASU） in the oxy fuel cycle. In this model, pure carbon dioxide with pressure of 20~ 105 Pa and purity of 96.84% was captured. NOx emissions also decrease by 4289.7 tons per year due to separation of nitrogen in ASU. In this model, none of the components of oxy fuel cycle is a major engineering challenge. With increasing oil price, economic justification of oxy fuel combustion model increases. With the price of oil at $ 80 per barrel in mind and $ 31 per ton fines for emissions of carbon dioxide in the atmosphere, IRR is the same for both models.     

Fundamental study on iron ore sintering new process of flue gas recirculation together with using biochar as fuel

It is of great significance for cleaner production to substitute bio-energy for fossil fuels in iron ore sintering. However, with the replacement ratio increasing, the consistency of heat front and flame front is broken, and the thermal utilizing efficiency of fuel is reduced, which results in the decrease of yield and tumble index of sinter. Circulating flue gas to sintering bed as biochar replacing 40% coke, CO in flue gas can be reused so as to increase the thermal utilizing efficiency of fuels, and the consistency of two fronts is recovered for the circulating flue gas containing certain CO2, H2 O and lower O2, which contributes to increasing the maximum temperature, extending the high temperature duration time of sintering bed, and results in improving the output and quality of sinter. In the condition of circulating 40% flue gas, the sintering with biomass fuels is strengthened, and the sintering indexes with biomass fuel replacing 40% coke breeze are comparative to those of using coke breeze completely.     

Novel miniature pneumatic pressure regulator for hopping robots

A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An especial poppet is designed to minimize its size and to withstand high-pressure. The pressure regulator is designed for a hopping robot which is powered by a combustion system. The hopping robot has great moving capacities such as jumping over big obstacles,walls and ditches. The regulator helps the hopping robot to decrease size and weight,and to sustain high pressure of oxygen and fuel tank. It will maintain constant output pressure to obtain suitable proportion of oxygen and fuel in the combustion cylinder. Dynamic simulation of the miniature pneumatic pressure regulator is performed. Experiments on prototype of miniature pneumatic pressure regulator are also carried out to validate the performance and satisfied performance is obtained.     

Development of performance and combustion system of Atkinson cycle internal combustion engine

The application of hybrid vehicle is a practical technical solution to the energy shortage and the environmental pollution.The internal combustion engine(ICE)plays a key role in the development of the hybrid vehicle.Based on the requirements of the hybrid vehicle and the characteristic of Atkinson cycle,a set of designing methods for the Atkinson cycle gasoline engine is presented through the analysis of the optimized matching for the compression ratio,valve timing and the combustion chamber.The designing method has been verified by the bench test and the results show that the fuel consumption can be improved by12%–15%with the reduction of the low speed torque by 10%,and the low fuel consumption region in the fuel map extends significantly with the rated power almost keeping constant.It may be of great reference for the development of hybrid vehicle technology in China.     

Dynamic simulation on effect of flame arrangement on thermal process of regenerative reheating furnace

By analyzing the characteristics of combustion and billet heating process, a 3-D transient computer fluid dynamic simulation system based on commercial software CFX4.3 and some self-programmed codes were developed to simulate the thermal process in a continuous heating furnace using high temperature air combustion technology. The effects of different switching modes on injection entrancement of multi burners, combustion and billet heating process in furnace were analyzed numerically, and the computational results were compared with on-site measurement, which verified the practicability of this numerical simulation system. The results indicate that the flow pattern and distribution of temperature in regenerative reheating furnace with partial same-side-switching combustion mode are favorable to satisfy the high quality requirements of reheating, in which the terminal heating temperature of billets is more than 1 460 K and the temperature difference between two nodes is not more than 10 K. But since the surface average temperature of billets apart fi＇om heating zone is only about 1 350 K and continued heating is needed in soaking zone, the design and operation of current state are still needed to be optimized to improve the temperature schedule of billet heating. The distribution of velocity and temperature in regenerative reheating furnace with same-side-switching combustion mode cannot satisfy the even and fast heating process. The terminal heating temperature of billets is lower than that of the former case by 30 K. The distribution of flow and temperature can be improved by using cross-switching combustion mode, whose terminal temperature of billets is about 1 470 K with small temperature difference within 10 K.     

Two-stage numerical simulation for temperature profile in furnace of tangentially fired pulverized coal boiler

Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, multifield coupling simulation in typical work conditions was carried out off-line with the software CFX-4.3, and then the expression of temperature profile varying with operating parameter was obtained. According to real-time operating parameters, the temperature at arbitrary point of the furnace can be calculated by using this expression. Thus the temperature profile can be shown on-line and monitoring for combustion state in the furnace is realized. The simulation model was checked by the parameters measured in an operating boiler, DO130-9. 8/540. The maximum of relative error is less than 12% and the absolute error is less than 120℃, which shows that the proposed two-stage simulation method is reliable and able to satisfy the requirement of industrial application.     

Geometric effects of fuel regression rate in hybrid rocket motors

The geometric configuration of the solid fuel is a key parameter affecting the fuel regression rate in hybrid rocket motors. In this paper, a semi-empirical regression rate model is developed to investigate the geometric effect on the fuel regression rate by incorporating the hydraulic diameter into the classical model. The semi-empirical model indicates that the fuel regression rate decreases with increasing hydraulic diameter and is proportional to dh?0.2 when convective heat transfer is dominant. Then a numerical model considering turbulence, combustion, solid fuel pyrolysis, and a solid–gas coupling model is established to further investigate the geometric effect. Eight motors with different solid fuel grains are simulated, and four methods of scaling the regression rate between different solid fuel grains are compared. The results indicate that the solid fuel regression rates are approximate the same when the hydraulic diameters are equal. The numerical results verify the accuracy of the semi-empirical model.     

掺烧煤泥在300MW循环流化床锅炉中的应用

煤泥是煤在洗选加工后排出的洗煤废弃物,在循环流化床锅炉中掺烧煤泥可以实现变废为宝,实现节能环保,本文对临涣中利电厂300MW循环流化床锅炉的煤泥燃烧系统、方式进行了介绍,并分析了煤泥燃烧对循环流化床锅炉的影响。     

循环流化床锅炉燃烧系统参数关系特性分析

循环流化床锅炉机组普遍存在燃烧调整难、稳定性差等问题.为了寻求更为优越的CFB锅炉燃烧控制手段,通过对唐山市开滦东方电厂490 t·h-1CFB锅炉变工况的数据采集及处理,分析了变工况条件下给煤量、床温、一二次风配比和烟气含氧量等燃烧系统参数与机组负荷的关系,并引入组合参数单位负荷风量,降低了各参数耦合分析难度.研究表...     

油焦浆的流变特性研究

石油焦的燃料利用具有十分重要的意义,通过油焦浆流变特性的研究,对影响其流变特性的因素进行了分析,确定了油焦浆流体类型,为油焦浆的制备、输送和燃料提供了设计的依据。     

煤层气、煤矸石掺烧比对CFB炉内燃烧特性的影响

通过对某一炉膛内煤矸石和煤层气燃烧情况进行数值模拟,发现煤矸石和煤层气的掺烧比和一二次风比例对混烧特性有重要影响.分别改变掺烧比和一二次风的比例,得出这2种因素对混烧特性的综合影响:掺烧比主要影响炉膛密相区的温度分布,一二次风比例会影响炉膛内的整个流场.当煤矸石和煤层气的混合比例为8:2,一二次风比例为6:4的时候,综合得到的炉膛燃烧情况比较好.     

循环流化床锅炉的特点、现状及在我国的发展前景

指出了循环流化床燃烧锅炉具有NO排放低、脱硫效果好、能烧劣质煤且燃烧效率高、负荷调节能力强等优点,介绍了近年来在国内外的发展状况,并从我国的以煤为主要能源结构的状况和对环境保护越来越高的要求出发进行分析,指出循环流化床锅炉在我国具有广阔的发展前景。     

循环流化床锅炉中灰颗粒的演化特征

循环流化床(CFB)锅炉炉内的燃烧及传热与炉内床料的状态密切相关,而炉内床料主要是由燃煤含有的矿物组分经过燃烧、爆裂和磨耗过程形成的。对多家循环流化床电站锅炉选用煤种和不同部位的灰进行取样,使用可视化显微仪,获取了粒度分布和灰颗粒的微观形貌特征。根据循环流化床锅炉内灰颗粒的机械强度和耐磨性能的不同,将灰颗粒归为三类不同性质的灰,以此为基点,分别采用固定床燃烧后冷态振动筛分的方法和流化床实验台热态流化后筛分的方法,对比分析了灰颗粒在燃烧过程中的演化特征。结果表明:三类灰颗粒在不同的燃烧温度和时间的演化过程存在明显的不同。从而对循环流化床中的床料粒径分布的确定提供了理论依据。     

燃用生物质颗粒燃料锅炉的燃烧及排放特性

为得到燃用生物质颗粒燃料锅炉的燃烧和排放特性,建立了燃烧模拟实验台,进行了一次风量及二次风量不同配比、不同位置及不同料层厚度等参数对燃烧和排放性能影响的实验,为生物质颗粒燃料锅炉的设计提供了可靠的依据。样机测试和实际应用表明,此形式生物质锅炉高效节能、洁净燃烧、大气污染物排放量低,具有广阔的应用前景。     

330 MW CFB锅炉滚筒冷渣器流渣原因及应对措施分析

滚筒冷渣器广泛应用于循环流化床（CFB）锅炉机组上,其运行可靠性和热量回收性能是保障锅炉机组高效稳定运行的关键.从冷渣器的结构和锅炉机组运行的角度出发,详细分析了宁夏国华宁东电厂330MW CFB机组上滚筒冷渣器流渣的原因.针对滚筒冷渣器设计、返料腿和排渣口结构等方面提出了相应的优化方案,并在锅炉运行方式,入炉煤粒径控制及煤种掺烧等方面进一步提出了抑制冷渣器流渣的措施.     

小型 CFB 锅炉烟气脱硝改造两步法应用及探讨

由于循环流化床(CFB)锅炉特有的结构和燃烧方式,其氮氧化物排放低于其它炉型,有清洁炉型之称,但随着烟气污染物排放标准的进一步提高,其氮氧化物的排放已不能满足新的排放需要。选择性非催化还原法(SNCR)工艺+低氮燃烧(LNB)脱硝技术具有投资费用少、运行成本低、锅炉改造范围小等优势,而CFB锅炉具有烟气在炉内停留时间长、便于还原剂在炉内混合等特点,该脱硝改造两步法在小型循环流化床锅炉脱硝改造中被广泛应用。本文以75t/h循环流化床锅炉为模型,并采用环保性较高的尿素作为脱硝还原剂,通过低氮燃烧(LNB)+SNCR工艺两步法脱硝技术改造方式,进一步提高脱硝效率,并对锅炉进行针对性的改进以提高其出力,最终使烟气中NO_x排放达到新的国家标准要求。主要从实施背景、技术路线、疑难问题解决及改造后的效果分析、存在问题等进行分析探讨。     

循环流化床锅炉床温系统控制特性分析及参数优化

对循环流化床锅炉结构、工作过程及燃烧过程进行了分析,介绍了其燃烧过程的控制策略,特别分析了影响床温的主要因素,设计了床层温度控制器,给出了在该控制器下实际动态品质及参数优化结果,证明该控制器在现场的可行性。