Effective biomass integration into existing combustion plant

Fossil fuels such as coal still dominate in current energy production plants. However, due to their large carbon footprint caused by combustion, rising prices and the unclear an increased interest in renewable and alternative fuels is observable. By 2020, renewable energy should account for 20% of the EU’s final energy consumption in order to reduce the negative impacts of the utilization of fossil fuels. Biomass-based fuels contribute to this effort.The optimization approach introduced in this article supports sustainable and financially feasible biomass integration into the existing large energy producing system with combined heat and power (CHP) production. The objective is to identify optimal conditions (optimal amount of burned fuels with respect to energy demands and energy flows through key components) with regard to maximum annual financial profit.The general mathematical model of a CHP plant utilizing more types of fuels is introduced and an optimization problem is formulated. The approach application is demonstrated on a case study involving existing CHP plant co-firing coal and biomass. The optimization problem is implemented and solved in GAMS (General Algebraic Modeling System). A sensitivity analysis of crucial parameters is performed and the results are presented and discussed.     

我国建设生物质热电联产项目主要问题研究

本文概要介绍了我国生物质直接燃烧发电项目、以民用供热为主燃煤中小热电联产项目的发展现状和存在问题,分析了我国建设生物质热电联产项目的主要障碍,并提出解决问题的政策建议。     

Potential of biomass‐fired combined heat and power plants considering the spatial distribution of biomass supply and heat demand

Combined heat and power (CHP) plants fired by forest wood can significantly contribute to attaining the target of increasing the share of renewable energy production. However, the spatial distribution of biomass supply and of heat demand limits the potentials of CHP production. This article assesses CHP potentials using a mixed integer programming model that optimizes locations of bioenergy plants. Investment costs of district heating infrastructure are modeled as a function of heat demand densities, which can differ substantially. Gasification of biomass in a combined cycle process is assumed as production technology. Some model parameters have a broad range according to a literature review. Monte‐Carlo simulations have therefore been performed to account for model parameter uncertainty in our analysis. The model is applied to assess CHP potentials in Austria. Optimal locations of plants are clustered around big cities in the east of the country. At current power prices, biomass‐based CHP production allows producing around 3% of the total energy demand in Austria. Yet, the heat utilization decreases when CHP production increases due to limited heat demand that is suitable for district heating. Production potentials are most sensitive to biomass costs and power prices. Copyright © 2009 John Wiley & Sons, Ltd.     

System analysis for effective use of palm oil waste as energy resources

Biomass refers to renewable energy sources and comes from biological materials such as trees, plants, manure as well as municipal solid wastes. Effective utilization of biomass as an energy resource requires the use of an optimization model to take into account biomass availability, transportation distances, and the scales and locations of power facilities within a region. In this study, we develop a new analytical tool that integrates cost, energy savings, greenhouse gas considerations, scenario analysis, and a Geographic Information System (GIS) to provide a comprehensive analysis of alternative systems for optimizing biomass energy production. The goal is to find a system that optimizes the use of biomass waste by analyzing the cost, net avoided CO₂ emission, and net energy savings with the objective of profit maximization. In this paper, we describe an application of the modeling tool described above to one of the fastest growing agriculture industries in Asia, the palm oil industry, for the case of Malaysia. Five scenarios utilizing palm oil waste as energy resources are discussed. The scenario of installing of new Combined Heat and Power (CHP) plants in the region yielded a number of benefits in terms of net energy savings, net avoided CO₂ emission, and profits. The results also demonstrate the benefits of utilizing excess heat for biomass pre-treatment. The choice of a suitable CHP plant scale, management strategies for biomass seasonal availability, and market price of biomass are also important factors for effective use of the biomass in a region.     

基于有机朗肯循环的生物质能热电联产技术的研究

阐述了中国生物质能开发和利用的前景,总结比较了国内外不同的生物质能热电联产技术,提出并介绍了基于有机朗肯循环(ORC)的生物质能热电联产技术。最后,讨论了ORC在回收余热、废热和冷能等方面的应用。     

Conditions for aggregation of CHP plants in the UK electricity market and exploration of plant size

Combined heat and power (CHP) plants with thermal stores may be suitable for sustainable energy production and the accommodation of fluctuating renewable energy sources. At the moment, in the UK, only a few CHP plants have thermal stores. Previous research has shown that thermal stores can improve the economics of CHP plants in the UK under the current market conditions. However, currently, it is only beneficial for CHP plants to sell their electricity to a third party, a Licensed Electricity Supplier, rather than to sell it directly to the power exchange market at prices which are much higher. If CHP plants aggregate, direct access to the power exchange market can become economically viable hence there is the possibility that thermal stores could further improve the economics of CHP plants under an aggregated electricity dispatch. This work firstly explains the conditions under which such plants could aggregate and act as a large power plant in the UK market, and secondly explores the most economic-size of gas engine and thermal store, in the case of aggregation, using energyPRO software and Excel spreadsheets. The work suggests that direct access to the power exchange market can improve the economics of the CHP plants. The highest Net Present Value (NPV), without heat dissipation, for a CHP plant exporting its electricity to the grid for a community heating load of 20 GW h, is more than £5 m, and is obtained for a 6 MW engine with a 28.2 MW h (900 m³) thermal store. The research suggests that such high electricity prices could make even larger plants more profitable than that; however, this can happen only if some of the produced heat is dissipated.     

MINLP optimisation model for increased power production in small-scale CHP plants

In this work we present a mixed integer nonlinear programming (MINLP) model for increasing the power production in small-scale (1–20 MW_e) CHP plants based on a steam Rankine process and using biomass fuels. Changes that could increase the power production in these plants are, for instance, a steam reheater, a feed water preheater, a two-stage district heat exchanger, and a fuel dryer. In the model we also consider the integration of a gas turbine and a gas engine into the CHP process by using the oxygen remains of the turbine or engine exhaust gases as preheated combustion air in the biomass boiler. The developed MINLP model was tested with four existing small-scale CHP plants. The results showed that there are profitable possibilities to increase the electrical efficiencies and power-to-heat ratios of these plants with the addition of a two-stage district heating exchanger, a feed water preheater, a steam reheater, and a fuel dryer. Furthermore, the integration of a gas engine increased the efficiencies significantly. Overall, the MINLP model gave good results for the example cases, but the model could be still improved by developing its mathematical formulation to a more convex model and by adding the operational changes in the district heating network to the model with multiperiod modeling. The current model gives new possibilities to the design planning and optimisation of the small-scale CHP plants, and it also provides a good basis for the future design modeling of the CHP plants and their optimal integration to the district heating network.     

Co-firing—A strategy for bioenergy in Poland?

Biomass provides the largest reduction of carbon dioxide (CO₂) emission when it replaces coal, which is the dominating fuel in heat and electricity production in Poland. One means of replacing coal with biomass is to co-fire biofuels in an existing coal-fired boiler. This paper presents an analysis of the strengths and weaknesses of co-firing biofuels in Poland with respect to technical, environmental, economical and strategic considerations. This analysis shows that co-firing is technically and economically the most realistic option for using biofuels in the large pulverized fuel (PF) boilers in Poland. However, from an environmental perspective, co-firing of biofuels in large combined heat and power (CHP) plants and power plants provides only a small reduction in sulphur dioxide (SO₂) emission per unit biofuel, since these plants usually apply some form of desulphurization technology. In order to maximize the SO₂ emission reduction, biofuels should be used in district heating plants. However, co-fired combustion plants can handle disruptions in biofuel supply and are insensitive to moderate changes in fuel prices, which makes them suitable utilizers of biofuels from perennial energy crops. Co-firing could therefore play an important role in stimulating perennial crop production.     

An above-ground biomass production model for a common reed (Phragmites communis Trin.) stand

A model is presented describing above-ground biomass production for a monospecific community of common reed (Phragmites communis Trin.), a perennial which is characteristically found in wetlands. The approach used follows the classic method applied to crop plants, namely the determination of stand phenology, and the establishment of the relationships governing leaf area production, light energy absorption by the leaves, and conversion efficiency of absorbed energy into biomass. The model also needed to take into account remobilisation of reserves accumulated in the rhizomes, which ultimately form a significant proportion of accumulated above-ground biomass. The final model was tested over two consecutive years, and produced promising results with regard to both the levels of production attained and the kinetics of the processes involved. The model can be used to determine production potential under given climatic conditions in its current form, and could even be applied to plant canopies with analogous biological characteristics, although scope remains for additional refinements.     

Energy efficiency analysis and impact evaluation of the application of thermoelectric power cycle to today’s CHP systems

High efficiency thermoelectric generators (TEG) can recover waste heat from both industrial and private sectors. Thus, the development and deployment of TEG may represent one of the main drives for technological change and fuel substitution. This paper will present an analysis of system efficiency related to the integration of TEG into thermal energy systems, especially Combined Heat and Power production (CHP). Representative implementations of installing TEG in CHP plants to utilize waste heat, wherein electricity can be generated in situ as a by-product, will be described to show advantageous configurations for combustion systems. The feasible deployment of TEG in various CHP plants will be examined in terms of heat source temperature range, influences on CHP power specification and thermal environment, as well as potential benefits. The overall conversion efficiency improvements and economic benefits, together with the environmental impact of this deployment, will then be estimated. By using the Danish thermal energy system as a paradigm, this paper will consider the TEG application to district heating systems and power plants through the EnergyPLAN model, which has been created to design suitable energy strategies for the integration of electricity production into the overall energy system.     

生物质与煤混燃燃烧特性研究进展

基于能源与环境的双重压力,以及生物质与煤单独燃用存在的问题,生物质与煤混燃已成为一种发展趋势,但其利用方面还面临着许多困难。因此,研究混合燃料燃烧过程中的燃烧特性及污染物规律,对于生物质与煤混燃技术的利用具有重要的意义。本文重点介绍了近年来国内外在生物质与煤混燃燃烧特性,及污染物排放的方面研究现状,并提出了研究过程中存在的问题,以期为后续的研究工作提供有价值的参考。     

Exploring the potential of reed as a bioenergy crop in the Netherlands

Second-generation biofuels that produce biomass for combustion or ethanol production do not yet appear to be a viable alternative to agriculture as they are low-value products. This may change, however, when energy prices increase and their production is combined with the provision of other services. The current analysis explores the potential for the production of an often overlooked biomass feedstock that can be combined with water and nature management objectives: reed. This crop has the additional advantage that it can be grown under conditions that are unfavourable to most other crops. An economics-based land-use modelling approach is applied to simulate the local competition between reed and grassland used for dairy farming under four different future scenarios in the Netherlands. Based on a location-specific assessment of potential costs and benefits of these crops under scenario-based conditions this analysis shows that the cultivation of reed for bioenergy, in combination with providing additional land-use functions, while not viable option under current economic and political conditions, may become competitive within the next twenty years if any of the following developments occur: energy prices increase substantially; water tables rise in the low-lying western parts of the country due to climate change; a policy is implemented that increases bioenergy prices; or a policy is implemented that stimulates water buffering and the preservation of peat soils.     

Analysis of energy-conversion processes in gas–steam power-plants integrated with coal gasification

The paper presents the complex energy analysis of technological systems of gas–steam power plants integrated with coal gasification. The bases of the performed energy analyses are the elaborate mathematical models describing the behaviour of main elements of the gas-steam power plants integrated with coal gasification, such as the gas generator, raw-gas cooler with the gas desulphurisation system, compressor, combustion chamber, gas turbine, heat-recovery steam-generator and steam-turbine cycle. The influence of coal-gasification technology, coal type, gasifying medium, fuel-desulphurisation technology and gas-turbine design on the efficiency of electric-energy generation were taken into account.     

燃煤链条锅炉改燃生物质颗粒燃料的方案研究

生物质颗粒燃料取代常规煤燃料对节约常规能源、优化我国能源结构、减轻环境污染具有积极的意义。生物质颗粒燃料与常规煤燃料的特性有较大的区别。当将燃煤锅炉改造为燃生物质颗粒燃料锅炉时应采取相应的改造措施。以本公司锅炉为实例对燃煤链条锅炉的炉膛和燃烧系统进行了改造,通过对炉拱、炉排、风室、卫燃带、上料系统、燃烧控制系统进行改造实现了锅炉与生物质颗粒燃料燃烧的良好匹配。能效和环保测试结果表明,锅炉改燃生物质颗粒燃料后热效率提高,污染物排放符合标准要求。     

12MW生物质直燃发电的热电联产系统节能经济性分析

以山东阳信市某企业生物质直燃发电的热电联产系统为研究对象,以其热、电负荷计算为基础,进行了主要设备的选型匹配。同时从标准煤耗量、年均总热效率和成本节约三个方面对系统进行节能经济性分析,指出了热电厂梯级利用能量的意义。分析结果表明：实施热电联产后系统年均总热效率达到60.9%,较中小型纯凝机组的提高约25.9%;在企业年生产总量不变的条件下,年节约标准煤约35352t,极大地节约了生产成本,具有可观的经济效益。     

利用低温碳化技术生产清洁固体燃料

介绍了一种利用低温碳化技术开发出的低成本、高效率的劣质固体燃料(结合生物能、褐煤、煤、原煤)预处理技术。这种预处理过程在燃烧之前的小规模的还原性气氛中除去有害的气体污染物(如氮、硫、氯、汞)，从而提高燃料效率。它主要应用在小于50MW的小型电厂和热电联产机组，以及小于300MW的中型电厂。     

Coal cleaning: a viable strategy for reduced carbon emissions and improved environment in China?

China is a dominant energy consumer in global context and current energy forecasts emphasise that China's future energy consumption also will rely heavily on coal. The coal use is the major source of the greenhouse gas CO₂ and particles causing serious health damage. This paper looks into the question if coal washing might work as low cost strategy for both CO₂ and particle emission reductions. Coal washing removes dirt and rock from raw coal, resulting in a coal product with higher thermal energy and less air pollutants. Coal cleaning capacity has so far not been developed in line with the market potential. In this paper an emerging market for cleaned coal is studied within a CGE model for China. The macro approach catches the repercussions of coal cleaning through increased energy efficiency, lower coal transportation costs and crowding out effect of investments in coal washing plants. Coal cleaning stimulates economic growth and reduces particle emissions, but total energy use, coal use and CO₂ emissions increase through a rebound effect supported by the vast reserve of underemployed labourers. A carbon tax on fossil fuel combustion has a limited effect on total emissions. The reason is a coal leakage to tax exempted processing industries.     

Biomass-Based Combined Heat and Power Systems

This study aims to identify and evaluate the biomass utilization options and evaluate the sustainable biomass production for combined heat and power (CHP) in Turkey. The total biomass energy potential of Turkey is about 32 Mtoe. The amount of usable biomass potential of Turkey is approximately 17 Mtoe. Among the biomass energy sources, fuel wood seems to be one of the most interesting because its share of the total energy production of Turkey is high at 21%. The use of biofuels for CHP on a large scale is focused mainly on forest industry sites, where considerable quantities of biomass are available. Biomass available for energy can be converted to different types of final energy (e.g., electricity, heat), of these, the production of electricity appears to be particularly important. While CHP provides several environmental benefits by making use of waste heat and waste products, air pollution is a concern any time fossil fuels or biomass are burned.     

Conversion of straw and similar agricultural wastes

Mainly the economic aspects prevent a far more extensive use of biomass, including straw as a fuel in energy supply.

During the latest years several straw fired plants have been put in operation, especially in Denmark, and they have demonstrated that both district heating and combined heat and power (CHP) production based on straw are technically possible.

However, experience has shown that a very precise research and development effort is necessary before the straw fired plants are competitive to traditional plants fired with fossil fuels, as to operational safety and economy.

The R & D activities ought first and foremost to aim at: 1) Reduction of costs connected to all processes from harvest to energy production, 2) wider know-how of the firing and combustion technical characteristics of straw, and 3) environmental conditions, including emissions and ash depositing problems.     

The feasibility of co-firing biomass for electricity in Missouri

Bioenergy is one of the most significant energy resources with potential to serve as a partial replacement for fossil. As an agricultural state, Missouri has great potential to use biomass for energy production. In 2008, Missouri adopted a renewable portfolio standard (RPS) yet about 80% of its power supply still comes from coal. This paper describes a feasibility study of co-firing biomass in existing coal-powered plants in Missouri. Specifically, this study developed a linear programming model and simulated six scenarios to assess the economic feasibility and greenhouse gas impacts of co-firing biomass in existing qualified coal power plants in Missouri.The results of this study indicate that although co-firing can reduce the emissions of GHG and environmental pollutants, it is still not an economically feasible option for power generation without additional economic or policy incentives or regulations which could take environmental costs into account. Based on these results, strategies and policies to promote the utilization of biomass and to increase its competitiveness with fossil fuels are identified and discussed.