燃煤电站富氧燃烧及二氧化碳捕集技术研究现状及发展

本文对富氧燃烧和二氧化碳捕集技术的节能机理及其带来的社会效益进行了较为详尽的阐述,介绍了富氧燃烧及二氧化碳捕集技术的发展历程及现状,指出富氧燃烧及二氧化碳捕集技术在节能及环保方面将有广阔的前景。     

碳捕集与封存技术步骤

CCS技术可以分为捕集、运输以及封存三个步骤,商业化的二氧化碳捕集已运营了一段时间,已发展得较为成熟,而二氧化碳封存技术还在进行大规模的实验。二氧化碳的捕集方式主要有:燃烧前捕集、富氧燃烧和燃烧后捕集。     

燃煤电站锅炉富氧燃烧技术研究进展综述

富氧燃烧技术是未来实现燃煤电站锅炉CO2捕集和存储可能采取的技术路线之一,但是煤粉在普通空气和CO2气氛条件下的燃烧及传热传质特性有很大的区别,因此有必要对煤粉富氧燃烧技术进行深入的研究。通过总结富氧燃烧技术的最新研究进展,并与传统燃煤电站锅炉空气燃烧技术进行比较,从传热特性、煤的反应性以及污染物排放特性3个方面介绍了富氧燃烧的特点,为将来工业应用做好技术储备。     

碳捕集与封存

正碳捕集与封存(简称CCS)是指将大型发电厂所产生的二氧化碳(CO2)收集起来,并用各种方法储存以避免其排放到大气中的一种技术。这种技术被认为是未来大规模减少温室气体排放、减缓全球变暖最经济、可行的方法。CCS技术可以分为捕集、运输以及封存三个步骤,商业化的二氧化碳捕集已经运营了一段时间,技术已发展得较为成熟,而二氧化碳封存技术各国还在进行大规模的实验。二氧化碳的捕集方式主要有三种:燃烧前捕集、富氧燃烧和燃烧后捕集。燃烧前捕集主要运用于IGCC(整体煤气化联     

碳捕集与封存技术的现状与未来

全球气候变暖问题已经越来越严重,碳捕集与封存（CCS）技术被看作是最具发展前景的解决方案之一,随着研究的不断深入,CCS技术成本将进一步降低。碳捕集工艺按操作时间可分为燃烧前捕集、富氧燃烧捕集和燃烧后捕集,其中最有发展前景的是富氧燃烧捕集。CO2-EOR技术虽然不是直接针对性地封存二氧化碳,但其不仅可以解决二氧化碳的封存问题,还能提高油田采收率,近年来得到广泛应用。我国在CCS技术的研究上进行了大量工作,CCS技术已被列入＂973计划＂和＂863计划＂,北京高碑店热电厂二氧化碳捕集示范工程受到国内外的关注。虽然CCS技术取得了长足的进步,但仍面临着很多问题,如二氧化碳泄漏问题、技术难点、建设和运行成本高昂等。CCS技术项目投资较大,如果没有政府在立法和税收机制上的激励与优惠措施,很难真正进入商业化应用阶段。好在种种迹象表明,随着全球气候问题的加剧,各国政府越来越重视CCS技术的研发和利用。     

高压O2/CO2气氛下煤焦理论计算研究

研究表明在6MPa压力,富氧浓度为30%的条件下的增压富氧燃烧的经济性可以达到最佳。在此气氛下用一个简单的燃烧模型对碳球燃烧的情况进行理论计算,与空气气氛下的燃烧情况作对比,得到增压富氧燃烧在煤粉的燃烧时间和对烟气捕集回收二氧化碳上的优越性。从而为增压富氧燃烧的进一步发展提供理论基础。     

CO2捕集系统的能耗分析

通过对气体压缩机能耗的计算方法的论述,分析在捕集压缩CO2过程中的各种能量损失,并计算富氧燃烧烟气中各种杂质对烟气捕集能耗的影响.计算表明,在富氧燃烧烟气含有的各种杂质中,N2对烟气捕集的影响最大;随着SO2质量分数的增加,烟气的单位质量压缩功反而降低.     

富氧燃烧技术研究现状及发展

当前锅炉富氧燃烧技术正在逐步发展,其应用的规模和范围正在不断扩大,讨论了富氧燃烧技术的背景及意义,阐述了富氧燃烧技术的理论基础,详细介绍了国内外膜法制氧技术和富氧燃烧技术的发展历程及现状,最后对富氧燃烧技术的未来进行了展望,指出富氧燃烧技术在节能及环保方面将有广阔的前景.     

富氧燃烧锅炉烟气CO2捕集中回收NO的研究

在富氧燃烧锅炉烟气CO2捕集的基础上,提出了一种利用CO2捕集时加压降温的特殊工艺流程资源化回收NO的新方法.分析了富氧燃烧锅炉烟气CO2的捕集流程,证明高压低温的工况条件十分有利于NO加速氧化为NO2及NO2液相吸收转化为稀硝酸产品.基于化学反应动力学基本原理与实验数据,对吸收过程发生的化学反应进行分析与计算,结果表明:在压力为3 MPa、温度为30℃时,NO的氧化转化率可达90%,反应时间仅需8.06 s,水吸收不构成控制环节,无需其他化学药剂.按300MW富氧燃煤锅炉的烟气量及NO和O2的质量浓度范围计算,富氧燃烧发电机组在捕集高浓度CO2的同时,每小时可回收浓度为20%的稀硝酸1974 kg,折合纯质硝酸395kg,一天能产生约4.7万元的产值.     

典型富氧燃烧锅炉风烟系统稳态过程分析

以典型富氧燃烧锅炉风烟燃烧稳态模型为基础,对35MW富氧燃烧系统稳态运行工况下的风烟燃烧过程数据进行仿真,并对系统运行中涉及的配风、注氧、漏风控制和CO_2捕集工艺优化等主要问题进行详细分析,提出了改进运行特性和工艺参数的调节手段.结果表明:系统漏风率限制在3.6%以下时,干循环烟气理论上可获得80%以上的CO_2体积分数;高效的烟气水分脱除有利于系统运行和循环烟气中CO_2的捕集;不同的供氧配风方式将会造成燃烧优化、系统安全和控制调节的性能差异.     

Oxygen efficiency with regard to carbon capture

Carbon capture is often discussed in the literature with the sole focus on power processes, despite the fact that carbon dioxide emissions from other sources are just as relevant for the impact on the atmosphere. Furthermore, some carbon capture methods are relatively inefficient when applied to power production processes. Carbon capture should preferably be performed where the cost is as low as possible, i.e. not necessarily from power production processes. As an example, carbon capture using combustion with pure oxygen is far more energy efficient if it is used together with lime kilns or cement kilns than together with power production processes. A new concept termed “oxygen efficiency” is introduced in this paper. It describes the amount of carbon dioxide that can potentially be captured per unit of oxygen. As such, the oxygen efficiency quantifies the value of a certain unit of oxygen for carbon capture reasons. The base concept is that the energy penalty for the production of one part of oxygen is the same no matter where it is produced; hence, if this unit of oxygen can be used to capture more carbon dioxide, it is more efficient. Typically, the oxygen efficiency would be five times greater for carbon capture when utilising pure oxygen together with cement kilns rather than together with methane-fired power plants. Furthermore, the concept of oxygen efficiency illustrates the importance of considering how carbon capture methods can be utilised in the most efficient way, in addition to evaluating which carbon capture method is the most suitable for a particular technology.     

Oxyfuel concept development

Abstract

The reduction of greenhouse gas emissions and replacement of fossil fuels by renewable energy sources are important national and international targets. Oxyfuel (oxygen combustion technology) is one of the most promising technologies enabling carbon capture and storage from flue gases. The aim of oxyfuel concept development is to study different oxygen production technologies, combustion processes, CO₂ capture methods and integrate those to optimised concept. The goal is to create technical readiness for demonstration of oxygen combustion by using state of the art knowledge, experiments, modelling and simulation. Demonstration plan for oxygen combustion for an existing power plant(s) in Finland will be prepared. Main results will be an evaluation of oxygen combustion business potential for implementation in existing and new power plants, and improvement of competitiveness of Finnish companies in energy sector by developing CO₂ free power production technologies.

Before oxygen combustion can be demonstrated in full scale, small scale testing and model development must be done. Material exposure conditions in oxygen combustion will differ from any present day environment. Current high temperature steel grades have not been developed or tested for such aggressive conditions. VTT (Technical Research Centre of Finland) has in Jyväskylä unique small scale combustors applicable for oxygen combustion research.     

Oxy-fuel combustion technology for coal-fired power generation

The awareness of the increase in greenhouse gas emissions has resulted in the development of new technologies with lower emissions and technologies that can accommodate capture and sequestration of carbon dioxide. For existing coal-fired combustion plants there are two main options for CO₂ capture: removal of nitrogen from flue gases or removal of nitrogen from air before combustion to obtain a gas stream ready for geo-sequestration. In oxy-fuel combustion, fuel is combusted in pure oxygen rather than air. This technology recycles flue gas back into the furnace to control temperature and makeup the volume of the missing N₂ to ensure there is sufficient gas to maintain the temperature and heat flux profiles in the boiler. A further advantage of the technology revealed in pilot-scale tests is substantially reduced NO_x emissions. For coal-fired combustion, the technology was suggested in the eighties, however, recent developments have led to a renewed interest in the technology. This paper provides a comprehensive review of research that has been undertaken, gives the status of the technology development and assessments providing comparisons with other power generation options, and suggests research needs.     

浅析二氧化碳捕获技术应用于炼厂的可行性

温室气体减排已成为炼厂面临的严峻挑战。CO2捕获是具有大规模减排潜力的技术方案,炼厂可在继续使用廉价化石燃料的同时降低排放。目前许多炼厂已在评估从烟道气中捕获CO2的技术,探索经济可行的捕获方案,这些方案主要包括燃烧后捕获、燃烧前捕获和富氧燃烧捕获等。其中,燃烧后捕获技术相对成熟,可对大多数现有装置进行改造,仅需增加简单的后处理设备,缺点是能耗大,CO2浓度较低,难捕获,从胺溶液中释放的CO2达不到碳封存所需的压力;燃烧前捕获方案的优点是CO2浓度较高,压力高,易于回收,降低了压缩成本及负荷,缺点是这种方法主要适用于新装置,因为炼厂现有的气化装置较少,建设投资成本高且需要大量的辅助系统;富氧燃烧捕获方案的优点是烟道气中的CO2浓度非常高,分离容易;缺点是空气分离设备投资很高,冷却的循环烟道气必须保持一定温度。对3种方案评价表明,在CO2总量和浓度最高的排放源进行捕获成本最低,例如当气体中CO2浓度从12%下降到4%时,捕获成本将上升25%以上;燃烧前捕获和富氧燃烧捕获比燃烧后捕获可节约35%~40%的成本。     

Oxy‐fuel combustion technology: current status,applications, and trends

The increased level of emissions of carbon dioxide into the atmosphere due to burning of fossil fuels represents one of the main barriers toward the reduction of greenhouse gases and the control of global warming. In the last decades, the use of renewable and clean sources of energies such as solar and wind energies has been increased extensively. However, due to the tremendously increasing world energy demand, fossil fuels would continue in use for decades which necessitates the integration of carbon capture technologies (CCTs) in power plants. These technologies include oxycombustion, pre‐combustion, and post‐combustion carbon capture. Oxycombustion technology is one of the most promising carbon capture technologies as it can be applied with slight modifications to existing power plants or to new power plants. In this technology, fuel is burned using an oxidizer mixture of pure oxygen plus recycled exhaust gases (consists mainly of CO₂). The oxycombustion process results in highly CO₂‐concentrated exhaust gases, which facilitates the capture process of CO₂ after H₂O condensation. The captured CO₂ can be used for industrial applications or can be sequestrated. The current work reviews the current status of oxycombustion technology and its applications in existing conventional combustion systems (including gas turbines and boilers) and novel oxygen transport reactors (OTRs). The review starts with an introduction to the available CCTs with emphasis on their different applications and limitations of use, followed by a review on oxycombustion applications in different combustion systems utilizing gaseous, liquid, and coal fuels. The current status and technology readiness level of oxycombustion technology is discussed. The novel application of oxycombustion technology in OTRs is analyzed in some details. The analyses of OTRs include oxygen permeation technique, fabrication of oxygen transport membranes (OTMs), calculation of oxygen permeation flux, and coupling between oxygen separation and oxycombustion of fuel within the same unit called OTR. The oxycombustion process inside OTR is analyzed considering coal and gaseous fuels. The future trends of oxycombustion technology are itemized and discussed in details in the present study including: (i) ITMs for syngas production; (ii) combustion utilizing liquid fuels in OTRs; (iii) oxy‐combustion integrated power plants and (iv) third generation technologies for CO₂ capture. Techno‐economic analysis of oxycombustion integrated systems is also discussed trying to assess the future prospects of this technology. Copyright © 2017 John Wiley & Sons, Ltd.     

Effects of hydrogen fraction in co-injection gas on combustion characteristics of the raceway in low carbon emission blast furnace

Co-injection of coal and hydrogen-rich gas with oxygen blast at tuyere is a promising technology for low carbon emission blast furnace ironmaking, which favors the development of hydrogen-based reduction and affordable carbon capture. Effects of hydrogen fraction in the co-injection gas on the combustion characteristics in raceway are numerically studied. Results show that increase of hydrogen fraction in the co-injection gas accelerates the preferential combustion of the injected gas, which promotes the preheating and pyrolysis of pulverized coal. This compensates the oxygen-grabbing effect and improves the burnout of coal from 83.2% to 86.8% with the hydrogen fraction in co-injection gas increase from 20 vol% to 80 vol%. With the CO/H₂ molar ratios in the co-injection gas of 8:2, 6:4, 4:6 and 2:8, the outlet CO/H₂ molar ratios are 54:46, 42:52, 32:68 and 24:76 respectively. Combustion, gasification and water-gas shift reactions play conjoint roles in the redistribution of reducing gas species.     

低NO_X燃烧技术对填充球蓄热室传热性能的影响

通过数值计算 ,研究了低 NOX燃烧技术 ,包括低氧燃烧和烟气再循环 ,对填充球蓄热室传热性能的影响。结果表明 ,低NOX燃烧技术应用到蓄热燃烧系统上合适与否 ,与燃料的热值水平有关。当燃用低热值燃料时 ,采用低氧燃烧技术是保证高热回收率和低 NOX排放量的有效途径     

Post combustion CO2 capture by carbon fibre monolithic adsorbents

As generation of carbon dioxide (CO₂) greenhouse gas is inherent in the combustion of fossil fuels, effective capture of CO₂ from industrial and commercial operations is viewed as an important strategy which has the potential to achieve a significant reduction in atmospheric CO₂ levels. At present, there are three basic capture methods, i.e. post combustion capture, pre-combustion capture and oxy-fuel combustion. In pre-combustion, the fossil fuel is reacted with air or oxygen and is partially oxidized to form CO and H₂. Then it is reacted with steam to produce a mixture of CO₂ and more H₂. The H₂ can be used as fuel and the carbon dioxide is removed before combustion takes place. Oxy-combustion is when oxygen is used for combustion instead of air, which results in a flue gas that consists mainly of pure CO₂ and is potentially suitable for storage. In post combustion capture, CO₂ is captured from the flue gas obtained after the combustion of fossil fuel. The post combustion capture (PCC) method eliminates the need for substantial modifications to existing combustion processes and facilities; hence, it provides a means for near-term CO₂ capture for new and existing stationary fossil fuel-fired power plants.This paper briefly reviews CO₂ capture methods, classifies existing and emerging post combustion CO₂ capture technologies and compares their features. The paper goes on to investigate relevant studies on carbon fibre composite adsorbents for CO₂ capture, and discusses fabrication parameters of the adsorbents and their CO₂ adsorption performance in detail. The paper then addresses possible future system configurations of this process for commercial applications.Finally, while there are many inherent attractive features of flow-through channelled carbon fibre monolithic adsorbents with very high CO₂ adsorption capabilities, further work is required for them to be fully evaluated for their potential for large scale CO₂ capture from fossil fuel-fired power stations.     

高温低氧燃烧条件下氮氧化物的生成特性

高温低氧燃烧原理是高温空气燃烧技术赖以发展的基础，使得高温燃烧条件下的氮氧化物的生成与排放受到大大抑制。为了掌握这种非常规燃烧现象及污染物生成的基本规律，采用扩散燃烧模型、热力NO生成模拟与湍流N－S方程，数值研究了燃烧空间中空气氧浓度对燃烧特性和氮氧化物排放浓度的影响，再现了高温与低氧两种条件相结合，形成的稳定的低氮氧化物排放的燃烧特性。计算结果与实验数据吻合，为发展高温空气燃烧技术提供了理论基础。