Analysis of biomass co-firing systems in Taiwan power markets using linear complementarity models

Biomass co-firing systems in power plants generate electric power by the simultaneous combustion of biomass and fossil fuels. The co-firing process reduces investment costs by converting biomass energy into electricity in existing conventional power plants. Biomass co-firing significantly reduces carbon dioxide and sulfur dioxide emissions in power generation. To meet the increase in biomass demand, this paper has considered systematic energy crop production, which is expected to increase in the near future. Our aim is to analyze biomass co-firing systems in the Taiwanese electricity market. In this paper, we study two emerging biomass feedstocks: switchgrass and Miscanthus. We focus on the impact of energy crop co-firing on carbon dioxide and sulfur dioxide emissions for electricity generation. A Nash–Cournot competition model, which simulates potential biomass co-firing scenarios, is formulated for power markets. A case study conducted in the Taiwanese electricity market showed that biomass co-firing lowers total electricity demand and sale. Miscanthus is more economical than switchgrass in terms of the production cost and the land required to generate biopower for the same levels of biomass co-firing.     

生物质与煤混烧技术的应用

生物质是一种可在再生、低污染的清洁能源，在能源系统中占有重要地位。本文综述了世界上生物质与煤混烧的应用状况，包括直接利用和气化利用，总结了目前生物质与煤混烧中存在的问题，并根据我国的实际情况，提出了在我国发展生物质混烧技术的建议。     

From biomass to electricity through integrated gasification/SOFC system-optimization and energy balance

In this paper the integrated process of biomass gasification and a solid oxide fuel cell (SOFC) was studied in terms of thermodynamics. The study is based on an ongoing project intending to develop an innovative sustainable technology with high efficiency. According to some assumptions, the energy balance revealed that the process can be auto-thermal. Furthermore, and due to the utilization of the hydrogen content of steam utilized in the reforming stage, the overall efficiencies to electrical power could reach very high levels.     

Technoeconomic assessment of beetle kill biomass co-firing in existing coal fired power plants in the Western United States

Widespread mortality of forests in the western United States due to a bark beetle epidemic provides a source of biomass for power generation. This study assessed availability and economics of co-firing beetle kill biomass with coal in power plants in the western U.S. Since biomass may be considered carbon neutral under careful management, co-combustion of biomass with coal provides power plants a way to meet emission reduction requirements, such as those in the EPA Clean Power Plan (CPP). Cost has been a barrier to co-firing, but the economics are altered by emission reduction requirements, such as CPP guidelines. The present study assessed beetle kill biomass availability in national forests in Wyoming and Colorado through Geographic Information System (GIS) analysis of U.S. Forest Service (USFS) data. Power plants near beetle kill mortality were identified as candidates for co-firing. An economic assessment of costs to implement co-firing was conducted. Co-firing reduces the need for the USFS to manage beetle kill trees when they are harvested for energy use, and these mitigated treatment costs were considered as an effective subsidy of co-firing. The results of this analysis include beetle kill availability, costs, and annual CO₂ emissions reductions that can be met by co-firing.     

我国生物质与煤混烧发电的可行性分析

通过对生物质发电政策法规、混烧发电优势、原料保障的分析,对生物质混烧发电技术方案进行讨论,并结合一些实例,分析得出生物质混烧发电适合我国国情,应大力发展.     

Integrated design and evaluation of biomass energy system taking into consideration demand side characteristics

In this paper, a linear programming model has been developed for the design and evaluation of biomass energy system, while taking into consideration demand side characteristics. The objective function to be minimized is the total annual cost of the energy system for a given customer equipped with a biomass combined cooling, heating and power (CCHP) plant, as well as a backup boiler fueled by city gas. The results obtained from the implementation of the model demonstrate the optimal system capacities that customers could employ given their electrical and thermal demands. As an illustrative example, an investigation addresses the optimal biomass CCHP system for a residential area located in Kitakyushu Science and Research Park, Japan. In addition, sensitivity analyses have been elaborated in order to show how the optimal solutions would vary due to changes of some key parameters including electricity and city gas tariffs, biogas price, electricity buy-back price, as well as carbon tax rate.     

A review on thermo-chemical characteristics of coal/biomass co-firing in industrial furnace

Biomass should be considered as one of the promising sources of energy for mitigating greenhouse gas (GHG) emissions. Co-firing biomass with coal has become a solution for meeting the power crisis as well as to reduce the pollutant emissions. The biomass fuels typically found from woody to grassy and solid recovered fuels depending on its origin and properties. It is suggested that co-firing coal with biomass has a substantial effect on SO_x and NO_x emission level. The ashing process, fly ash quality depends on the conversion technology, capture technology and the properties of the biomass. In order to control the furnace efficiency and production, burnout, optimum injection of biomass sharing with specific information of particle ignition properties are also important. A number of small/laboratory scale and industrial scale experiments have been conducted by different researchers. Different experimental studies performed are reviewed, grouped and summarized based on the fuel processing technology, burnout performance, emission level, environmental aspect, ash information and deposit characteristics, effect of co-firing ratios and adoption of oxy-fuel co-firing. Overall, this paper will highlight existing technologies and emerging trends in co-firing of different types of biomass which will be helpful for future investigations.     

Evaluation of feasibility of pelletized wood co-firing with high ash Indian coals

To reduce anthropogenic CO₂ emissions from power plants, biomass is an immediate alternative fuel which has similar properties as coal. In this regard, the present study discusses about pelletized wood (PW) co-firing with high ash Indian coal by conducting co-milling and co-firing trials in a 1000 kg/hr of pilot scale test facility. Indian coals are typically high ash content and low calorific value fuels, therefore, its interaction with coal during combustion and ash deposition have studied in detail. Based on co-milling trails of PW and coal, it was observed that as PW proportion in coal increases, the quantity of particles of size below 50 μm and as well above 500 μm were increased. From co-firing studies, it was observed that higher volatile content in PW helping in stabilizing flames while co-firing. At lower proportions, up to 10% weight PW co-firing with coal, the flame temperature and heat flux values are very close to base test of 100% coal firing. However, beyond 10% by weight of PW co-firing with coal, the flame temperature and heat flux values were increased significantly from 100% coal tests. This is because of higher calorific value of PW than coal. The CO emission was decreased with increase in PW proportion in coal but at 30% of PW in coal, CO emission was increased suddenly. However, NO and SO₂ concentrations were decreased up to 8% and 16% respectively with increase in PW proportion in coal due to lower fuel nitrogen and sulphur content in PW than coal. Analytical analysis of slagging indices suggest that the slagging potential for PW co-firing with coal is increasing as the PW proportion in coal increases.     

An exploratory game-theoretic analysis of biomass electricity generation supply chain

This study proposes a game-theoretic approach to model and analyze the process of utilizing biomass for power generation considering three players: distributor, facility developer, and participating farmer. We characterize the Nash equilibrium of the sequential game and discuss its features. A special attention is devoted to the analysis of the impact of incentives and initial target on the equilibrium, in which the biomass is part of electricity production.     

Influence of coal co-firing on the particulate matter formation during pulverized biomass combustion

Biomass is regarded as CO₂-neutral, while the high contents of potassium and chlorine in biomass induce severe particulate matter emission, ash deposition, and corrosion in combustion facilities. Co-firing biomass with coal in pulverized-combustion (PC) furnaces is able to solve these problems, as well as achieve a much higher generating efficiency than grate furnaces. In this work, the particulate matter (PM) emission from biomass co-firing with coal was studied in an entrained flow reactor at a temperature of 1623 K simulating PC furnace condition. PMs were sampled through a 13-stage impactor, and their morphology and elemental composition were characterized by scanning electron microscopy and electron dispersive X-ray spectroscopy. SO₂ emissions were measured to interpret the possibility of potassium sulfation during co-firing. Results show that PMs from the separated combustion of both biomass and coal present a bimodal particle size distribution (PSD). The concentration and size of fine-mode submicron particles (PM_1.0) from biomass combustion are much higher than those from coal combustion because of the high potassium content in biomass. For the co-firing cases, with the coal ratio increasing from 0% to 50%, the PM_1.0 yield is reduced by more than half and the PM_1.0 size becomes smaller, in contrast, the concentration of coarse-mode particles with the size of 1.0–10 μm (PM_1.0-10) increases. The measured PM_1.0 yields of co-firing are lower than the theoretically weight-averaged ones, which proves that during the biomass and coal co-firing in PC furnaces, the vaporized potassium from biomass can be efficiently captured by these silicon-aluminate oxides in coal ash. In the studied range of coal co-firing ratio (≤50 wt.%), the chlorides and sulfates of alkali metals from biomass burning are the dominating components in PM_1.0, and a certain amount of silicon is observed in PM_0.1-1. The analysis of chemical composition in PM_1.0, together with that of SO₂ emission, indicates a marginal sulfation of alkali metal chloride occurring at high temperatures in PC furnaces.     

Co-firing biomass with coal for electricity generation—An assessment of the potential in EU27

The European Union aims to increase bioenergy use. Co-firing biomass with coal represents an attractive near-term option for electricity generation from renewable energy sources (RES-E). This study assesses the near-term technical potential for biomass co-firing with coal in the existing coal-fired power plant infrastructure in the EU27 Member States. The total technical potential for RES-E from biomass co-firing amounts to approximately 50–90 TWh/yr, which requires a biomass supply of approximately 500–900 PJ/yr. The estimated co-firing potential in EU27 amounts to 20–35% of the estimated gap between current RES-E production and the RES-E target for 2010. However, for some member states the national co-firing potential is large enough to fill the national gap. The national biomass supply potential is considerably larger than the estimated biomass demand for co-firing for all member states. About 45% of the estimated biomass demand for co-firing comes from plants located close to the sea or near main navigable rivers and indicates the possibility for biomass import by sea transport. Thus, biomass co-firing has the potential to contribute substantially to the RES-E development in EU27.     

Wood-fuel biomass from the Madeira River: A sustainable option for electricity production in the Amazon region

The universal provision of electricity remains far from achieved in the Brazilian Amazon, given the geographical obstacles, the dispersion of its inhabitants, the indistinctness of appropriate technologies, and the economic obstacles. Governmental action was taken in 2003 with the creation of the Light for All Program (PLpT), with the goal of bringing electricity to all rural consumers by 2010. In addition, the National Electric Power Agency, ANEEL (Agência Nacional de Energia Elétrica), which is responsible in Brazil for the electrical sector regulation, has issued a determination of compulsory access to electricity by 2015. This study describes research conducted on the Madeira River, in the Brazilian Amazon, where the electric needs of the communities and small towns along the river can be satisfied through the gasification system, using as a renewable feedstock the wood-fuel biomass deposited on the riverbed, derived from natural processes, which the Ministry of Transport is already legally obligated to remove in order to provide safe navigation along the river. The study concludes by comparing the competitiveness of this system to diesel thermoelectric plants, along with its advantages in reducing the emission of greenhouse gases. Our results should help future studies in others areas with similar phenomena.     

Can the environmental benefits of biomass support agriculture?—The case of cereals for electricity and bioethanol production in Northern Spain

Recent policy documents, such as the EC Communication on an Energy Policy for Europe (January 2007) make emphasis on the opportunities that energy applications can offer certain agricultural commodities, especially in the framework of a progressive dismantling of the Common Agricultural Policy. This paper analyses whether this can be true for wheat and barley farmers, using the real example of a straw-based power plant in Northern Spain and a theoretical factory for bioethanol production fed with cereal grain. The outcomes of such an exercise, in which their relative environmental benefits vis-à-vis fossil fuel alternatives are worked out with the aid of a simplified life-cycle approach, show that the characteristics of the electricity and biomass markets, the baseline scenario and the fuel prices are crucial for the future of the sector.     

Goal programming model for sustainable electricity production from biomass

In this paper, we present a goal programming model for block level energy planning in order to make a block self‐sufficient in electricity consumption, which includes the commercial energy consumption goal, the goal of generating electricity from biomass and food production goals with linear constraints on the available sources such as human power, animal power, tractor power, land area and on the requirement of the block such as cooking energy, lighting energy and energy for other operations, such as fodder for animal population. We try to achieve these goals through proper allocation of land for different crops. After reformulating the developed goal programming model into a linear programming format, we use the HYPER LINDO software package to solve it in a Pentium‐based IBM‐PC compatible computer system. The developed model is solved for a typical Indian block, namely Nilakkottai Block in Tamil Nadu, India. The model solution shows that the goal of generating electricity from biomass is achieved, the commercial energy consumption goal and pulses requirement goal are under‐achieved and the sugar requirement goal is over‐achieved. Furthermore, the cereal, vegetable and oilseed production goals are achieved. Copyright © 2000 John Wiley & Sons, Ltd.     

Numerical modeling of the gasification based biomass co-firing in a 600 MW pulverized coal boiler

Gasification based biomass co-firing was an attractive technology for biomass utilization. Compared to directly co-firing of biomass and coal, it might: (1) avoid feeding biomass into boiler, (2) reduce boiler fouling and corrosion problem, and (3) avoid altering ash characteristics. In this paper, CFD modeling of product gas (from biomass gasification) and coal co-firing in a 600 MW tangential PC boiler was carried out. The results showed that NO_x emission was reduced about 50–70% when the product gas was injected through the lowest layer burner. The fouling problem can be reduced with furnace temperature decreasing for co-firing case. The convection heat transfer area should be increased or the co-firing ratio of product gas should be decreased to keep boiler rated capacity.     

Acceptance of biomass plants – Results of a longitudinal study in the bioenergy-region Altmark

The present contribution addresses the results of a longitudinal study in a ‘bioenergy-region’ concerning the public acceptance of biomass plants and the corresponding influencing factors. Using a standardized questionnaire, 423 persons were polled between 2009 and 2011 on three points of measurement in four places in the bioenergy-region Altmark. One main result of the study is that the reported public acceptance remains constantly high over time; nevertheless it became evident that the respective influencing factors differ in their strength, whereas the perceived regional benefit shows a strong connection to the reported public acceptance of biomass plants at each point of measurement. Concluding the research results, the acceptance of biomass plants doesn't seem to be a fixed construct, but has to be seen in context of the respective experiences with plants on a local level over time.In addition to the local population, key actors of the regional biomass sector were also interviewed (N = 26). The analyses show significant differences in the perception and evaluation of the current informational level between the population and the key actors. Furthermore, the key actors estimated the utilisation of biomass even more positively and expected a greater ‘signal function’ of the bioenergy-region-project compared to the population.     

Design of biomass processing network for biofuel production using an MILP model

This paper presents a general optimization model that enables the selection of fuel conversion technologies, capacities, biomass locations, and the logistics of transportation from the locations of forestry resources to the conversion sites and then to the final markets. A mixed integer linear programming (MILP) model has been formulated and implemented in a commercial software package (GAMS) using databases built in Excel. The MILP represents decisions regarding (1) the optimal number, locations, and sizes of various types of processing plants, (2) the amounts of biomass, intermediate products, and final products to be transported between the selected locations over a selected period, and maximizes the objective function of overall profit. The model has been tested based on an industry-representative data set that contains information on the existing wood resources, final product market locations and demands, and candidate locations and sizes for different types of processing plants, as well as the costs associated with the various processing units and transportation of materials, covering the Southeastern region of the United States. The model is applied to design both a distributed, and a more centralized, conversion system. The overall profits, values, cost, and supply network designs of both systems are analyzed using the optimization model. In particular, we investigate: 1) which parameters have major effect on the overall economics, and 2) the benefits of going to more distributed types of processing networks, in terms of the overall economics and the robustness to demand variations.     

Gasification and power generation characteristics of woody biomass utilizing a downdraft gasifier

Energy utilization from biomass resources has started to attract public attention as a method to reduce CO₂ emissions. In this study, the characteristics of syngas production from biomass gasification were investigated in a downdraft gasifier that was combined with a small gas engine system for power generation. Syngas temperatures from the gasifier were maintained at a level of 700-1000 °C. When the air ratio for gasification was 0.3-0.35, the low heating value of syngas was 1100-1200 kcal Nm⁻³ and the cold gas efficiency 69-72%. Tar concentration in raw syngas was around 3.9-4.4 g Nm⁻³. Syngas combustion in the gas engine after purification showed that HC concentration was below 200 ppm, and NOx concentration was below 40 ppm in the exhaust gas.     

Linear mixed-integer models for biomass supply chains with transport,storage and processing

This paper presents a linear mixed-integer modeling approach for basic components in a biomass supply chain including supply, processing, storage and demand of different types of biomass. The main focus in the biomass models lies on the representation of the relationship between moisture and energy content in a discretized framework and on handling of long-term processes like storage with passive drying effects in the optimization. The biomass models are formulated consistently with current models for gas, electricity and heat infrastructures in the optimization model ‘eTransport’, which is designed for planning of energy systems with multiple energy carriers. To keep track of the varying moisture content in the models and its impact on other biomass properties, the current node structure in eTransport has been expanded with a special set of biomass nodes. The Node, Supply, Dryer and Storage models are presented in detail as examples of the approach. A sample case study is included to illustrate the functionality implemented in the models.     

Decentralized generation of electricity from biomass with proton exchange membrane fuel cell

Biomass can be applied as the primary source for the production of hydrogen in the future. The biomass is converted in an atmospheric fluidized bed gasification process using steam as the gasifying agent. The producer gas needs further cleaning and processing before the hydrogen can be converted in a fuel cell; it is assumed that the gas cleaning processes are able to meet the requirements for a PEM-FC. The compressed hydrogen is supplied to a hydrogen grid and can be used in small-scale decentralized CHP units. In this study it is assumed that the CHP units are based on low temperature PEM fuel cells. For the evaluation of alternative technologies the whole chain of centralized hydrogen production from biomass up to and including decentralized electricity production in PEM fuel cells is considered.Two models for the production of hydrogen from biomass and three models for the combined production of electricity and heat with PEM fuel cells are built using the computer program Cycle-Tempo. Two different levels of hydrogen purity are considered in this evaluation: 60% and 99.99% pure hydrogen. The purity of the hydrogen affects both the efficiencies of the hydrogen production as well as the PEM-FC systems. The electrical exergy efficiency of the PEM-FC system without additional heat production is calculated to be 27.66% in the case of 60% hydrogen and 29.06% in the case of 99.99% pure hydrogen. The electrical exergy efficiencies of the whole conversion chain appear to be 21.68% and 18.74%, respectively. The high losses during purification of the hydrogen gas result in a higher efficiency for the case with low purity hydrogen. The removal of the last impurities strongly increases the overall exergy losses of the conversion chain.