高效燃用生物质颗粒蒸汽锅炉的研究与设计

介绍了生物质颗粒燃料的燃烧特性,针对燃用生物质颗粒燃料的蒸汽锅炉结构设计的要求,提出了增大锅炉炉膛结构,改善一二次进风的配比,采用二次进风热能回收和PLC自动控制等方面的改进措施。     

Optimization of boiler cold-end and integration with the steam cycle in supercritical units

In order to gain an extra increment of efficiency to compensate for capital costs, one of the main issues in the design of advanced supercritical power plants is the reduction of boiler exit gas temperature below typical values of conventional, subcritical units.     

CRS4-2: A numerical code for the calculation of the solar power collected in a central receiver system

The analysis of the solar power collected at the receiver in solar tower systems requires the use of efficient and accurate numerical codes. This paper presents a new Fortran computer program, CRS4-2 (an acronym for Crs4 Research Software for Central Receiver Solar System SimulationS), for the simulation of the optical performance of a central receiver solar plant. The implemented mathematical algorithm allows for the calculation of cosine, shading and blocking effects for heliostats arbitrarily arranged in the solar field. Special attention has been given to ensure the maximum flexibility concerning the number, dimension, shape, and position of the heliostats. In the present implementation, the solar field can be composed of both square and circular heliostats possibly mixed together, each one of them characterized by the size and height from the ground. The modular design of CRS4-2 allows the extension to heliostats of arbitrary shape with only minor modifications of the code. Shading and blocking effects are computed by a tessellation of the heliostats: therefore, the numerical accuracy depends only on the refinement of the tessellation. The application to actual systems has shown that the approach is stable and general.     

Highly efficient electricity generation from biomass by integration and hybridization with combined cycle gas turbine (CCGT) plants for natural gas

Integration/co-firing with existing fossil fuel plants could give near term highly efficient and low cost power production from biomass. This paper presents a techno-economical analysis on options for integrating biomass thermal conversion (optimized for local resources ∼50 MW_th) with existing CCGT (combined cycle gas turbine) power plants (800–1400 MW_th). Options include hybrid combined cycles (HCC), indirect gasification of biomass and simple cycle biomass steam plants which are simulated using the software Ebsilon Professional and Aspen Plus. Levelized cost of electricity (LCoE) is calculated with cost functions derived from power plant data. Results show that the integrated HCC configurations (fully-fired) show a significantly higher efficiency (40–41%, LHV (lower heating value)) than a stand-alone steam plant (35.5%); roughly half of the efficiency (2.4% points) is due to more efficient fuel drying. Because of higher investment costs, HCC options have cost advantages over stand-alone options at high biomass fuel prices (>25 EUR/MWh) or low discount rates (<5%). Gasification options show even higher efficiency (46–50%), and the lowest LCoE for the options studied for fuel costs exceeding 10 EUR/MWh. It can be concluded that clear efficiency improvements and possible cost reductions can be reached by integration of biomass with CCGT power plants compared to stand-alone plants.     

Potential of a direct contact adsorption heat pump system for generating steam from waste water

An adsorption heat pump with a direct contact system for steam generation has been developed and the feasibility of the proposed system was confirmed both theoretically and experimentally. The basic cycle for the system has been proposed to use zeolite–water working pairs in the p‐T‐x equilibrium curve. To generate steam above 150°C from low‐energy level water at 80°C, a direct contact adsorption heat pump prototype was constructed. The experimental results show that steam could be generated by the direct contact system and the relationship between the amount of water adsorbed and the change in temperature with time is discussed. This study is expected to serve as a foundation for developing continuous adsorption heat pump systems for steam generation. Copyright © 2011 John Wiley & Sons, Ltd.     

某660MW超临界锅炉抽高温再热蒸汽加热一次风系统改造效果分析

通过介绍某660MW超临界锅炉抽高温再热蒸汽加热一次风系统改造,解决锅炉制粉系统干燥出力不足,一次风率偏高,主蒸汽温度偏低,水冷壁局部壁温超温等问题,对比改造前后锅炉运行数据,为以后存在相同问题的锅炉改造提供一定的依据。     

Exergoeconomic analysis of a hybrid system based on steam biomass gasification products for hydrogen production

In this paper, a conceptual hybrid biomass gasification system is developed to produce hydrogen and is exergoeconomically analyzed. The system is based on steam biomass gasification with the lumped solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) subsystem as the core components. The gasifier gasifies sawdust in a steam medium and operates at a temperature range of 1023-1423 K and near atmospheric pressure. The analysis is conducted for a specific steam biomass ratio of 0.8 kmol-steam/kmol-biomass. The gasification process is assumed to be self-thermally standing. The pressurized SOFC and SOEC are of planar types and operate at 1000 K and 1.2 bar. The system can produce multi-outputs, such as hydrogen (with a production capacity range of 21.8-25.2 kgh⁻¹), power and heat. The internal hydrogen consumption in the lumped SOFC-SOEC subsystem increases from 8.1 to 8.6 kg/h. The SOFC performs an efficiency of 50.3% and utilizes the hydrogen produced from the steam that decomposes in the SOEC. The exergoeconomic analysis is performed to investigate and describe the exergetic and economic interactions between the system components through calculations of the unit exergy cost of the process streams. It obtains a set of cost balance equations belonging to an exergy flow with material streams to and from the components which constitute the system. Solving the developed cost balance equations provides the cost values of the exergy streams. For the gasification temperature range and the electricity cost of 0.1046 $/kWh considered, the unit exergy cost of hydrogen ranges from 0.258 to 0.211 $/kWh.     

Simulation of a new biomass integrated gasification combined cycle (BIGCC) power generation system using Aspen Plus: Performance analysis and energetic assessment

A new biomass integrated gasification combined cycle (BIGCC), which featured an innovative two-stage enriched air gasification system coupling a fluidized bed with a swirl-melting furnace, was proposed and built for clean and efficient biomass utilization. The performance of biomass gasification and power generation under various operating conditions was assessed using a comprehensive Aspen Plus model for system optimization. The model was validated by pilot-scale experimental data and gas turbine regulations, showing good agreement. Parameters including oxygen percentage of enriched air (OP), gasification temperature, excess air ratio and compressor pressure ratio were studied for BIGCC optimization. Results showed that increase OP could effectively improve syngas quality and two-stage gasification efficiency, enhancing the gas turbine inlet and outlet temperature. The maximum BIGCC fuel utilization efficiency could be obtained at OP of 40%. Increasing gasification temperature showed a negative effect on the two-stage gasification performance. For efficient BIGCC operation, the excess air ratio should be below 3.5 to maintain a designed gas turbine inlet temperature. Modest increase of compressor pressure ratio favored the power generation. Finally, the BIGCC energy analysis further proved the rationality of system design and sufficient utilization of biomass energy.     

Investigation of a multi-generation system using a hybrid steam biomass gasification for hydrogen, power and heat

In this paper, an integrated process of steam biomass gasification and a solid oxide fuel cell (SOFC) is investigated energetically to evaluate both electrical and energy efficiencies. This system is conceptualized as a combined system, based on steam biomass gasification and with a high temperature, pressurized SOFC. The SOFC system uses hydrogen obtained from steam sawdust gasification. Due to the utilization of the hydrogen content of steam in the reforming and shift reaction stages, the system efficiencies reach appreciable levels. This study essentially investigates the utilization of steam biomass gasification derived hydrogen that was produced from an earlier work in a system combines gasifier and SOFC to perform multi-duties (power and heat). A thermodynamic model is developed to explore a combination of steam biomass gasification, which produces 70–75 g of hydrogen/kg of biomass to fuel a planar SOFC, and generate both heat and power. Furthermore, processes are emerged in the system to increase the hydrogen yield by further processing the rest of gasification products: carbon monoxide, methane, char and tar. The conceptualized scheme combines SOFC operates at 1000 K and 1.2 bar and gasifier scheme based on steam biomass gasification which operates close to the atmospheric pressure, a temperature range of 1023–1423 K and a steam-biomass ratio of 0.8 kmol/kmol. A parametric study is also performed to evaluate the effect of various parameters such as hydrogen yield, air flow rate etc. on the system performance. The results show that SOFC with an efficiency of 50.3% operates in a good fit with the steam biomass gasification module with an efficiency, based on hydrogen yield, of 55.3%, and the overall system then works efficiently with an electric efficiency of ∼82%.     

Preliminary design and controlling strategies of a small-scale wood waste Rankine Cycle (RC) with a reciprocating steam engine (SE)

In this paper, a small-scale Rankine Cycle (RC) operating as a combined heat and power (CHP) unit and fed by wood waste is studied and the preliminary design and theoretical analysis of the main RC components are presented. A reciprocating single-stage expansion steam engine (SE) was chosen as the expander device: its main characteristics and operative performance are discussed in detail. Finally, the off-design performance is studied with different part-load controlling strategies.     

Effects of particle sizes on performances of the multi-zone steam generator using waste heat in a bio-oil steam reforming hydrogen production system

Hydrogen production by bio-oil steam reforming is an advanced production technology. It is a good method of coupling waste heat utilization with bio-oil steam reforming to produce hydrogen, which increases the cleaning ability of the bio-oil steam reforming system. A multi-zone steam generator using waste heat has been proposed, which can produce the heat source and steam source of the hydrogen system. The DEM model of the multi-zone steam generator was set up. The model has been used to investigate the effects of particle sizes (40 mm–80 mm). With increasing particle size, the flow index and the flow uniformity gradually decrease, the vertical velocity gradient increases in the area on both side with the zone steam generator, and the vertical velocity fluctuation amplitude gradually increases. So, the hydrogen production decreases from the particle size increasing.     

An experimental study on air gasification of biomass micron fuel (BMF) in a cyclone gasifier

Biomass micron fuel (BMF) produced from feedstock (energy crops, agricultural wastes, forestry residues and so on) through an efficient crushing process is a kind of powdery biomass fuel with particle size of less than 250 μm. Based on the properties of BMF, a cyclone gasifier concept has been considered in our laboratory for biomass gasification. The concept combines and integrates partial oxidation, fast pyrolysis, gasification, and tar cracking, as well as a shift reaction, with the purpose of producing a high quality of gas. In this paper, characteristics of BMF air gasification were studied in the gasifier. Without outer heat energy input, the whole process is supplied with energy produced by partial combustion of BMF in the gasifier using a hypostoichiometric amount of air. The effects of equivalence ratio (ER) and biomass particle size on gasification temperature, gas composition, gas yield, low-heating value (LHV), carbon conversion and gasification efficiency were studied. The results showed that higher ER led to higher gasification temperature and contributed to high H₂-content, but too high ER lowered fuel gas content and degraded fuel gas quality. A smaller particle was more favorable for higher gas yield, LHV, carbon conversion and gasification efficiency. And the BMF air gasification in the cyclone gasifier with the energy self-sufficiency is reliable.     

Energy and exergy analysis of a micro-compressed air energy storage and air cycle heating and cooling system

Energy storage systems are becoming more important for load leveling, especially for widespread use of intermittent renewable energy. Compressed air energy storage (CAES) is a promising method for energy storage, but large scale CAES is dependent on suitable underground geology. Micro-CAES with man-made air vessels is a more adaptable solution for distributed future power networks. In this paper, energy and exergy analyses of a micro-CAES system are performed, and, to improve the efficiency of the system, some innovative ideas are introduced. The results show that a micro-CAES system could be a very effective system for distributed power networks as a combination that provides energy storage, generation with various heat sources, and an air-cycle heating and cooling system, with a energy density feasible for distributed energy storage and a good efficiency due to the multipurpose system. Especially, quasi-isothermal compression and expansion concepts result in the best exergy efficiencies.     

Design study of configurations on system COP for a combined ORC (organic Rankine cycle) and VCC (vapor compression cycle)

The study introduced a novel thermally activated cooling concept - a combined cycle couples an ORC (organic Rankine cycle) and a VCC (vapor compression cycle). A brief comparison with other thermally activated cooling technologies was conducted. The cycle can use renewable energy sources such as solar, geothermal and waste heat, to generate cooling and power if needed. A systematic design study was conducted to investigate effects of various cycle configurations on overall cycle COP. With both subcooling and cooling recuperation in the vapor compression cycle, the overall cycle COP reaches 0.66 at extreme military conditions with outdoor temperature of 48.9 °C. A parametric trade-off study was conducted afterwards in terms of performance and weight, in order to find the most critical design parameters for the cycle configuration with both subcooling and cooling recuperation. Five most important design parameters were selected, including expander isentropic efficiency, condensing and evaporating temperatures, pump/boiling pressure and recuperator effectiveness. At the end, two additional cycle concepts with either potentially higher COP or practical advantages were proposed. It includes adding a secondary heat recuperator in the ORC side and using different working fluids in the power and cooling cycles, or so-called dual-fluid system.     

空气制冷循环特性及一种新型涡流制冷装置研究

通过与蒸汽压缩制冷循环的比较,论述了空气制冷循环的特性,特别是空气制冷循环对解决环保问题的优良特性以及适用温度范围宽广的特点。并且提出一种新型涡流管制冷装置系统。     

城市生活垃圾原位水蒸气气化制氢研究

在固定床反应器中对城市生活垃圾进行原位水蒸气气化制氢研究,考察了加热方式、反应温度以及含水率对城市生活垃圾原位水蒸气气化特性的影响。结果表明,快加热方式有利于提高燃气品质和降低焦油含量;随着反应温度的增加,气体产物含量增加,焦油含量和半焦含量下降,气体组分中H2和CO含量升高,碳转化率从30.49%增加到56.79%;当城市生活垃圾含水率为39.45%时,产气品质最高,气体成分中H2含量达到最高值25.8%,气体的低位热值达到17.02 MJ/m3;温度升高和蒸汽引入能改变半焦产物的表观形貌,并能提高半焦产物的BET以及灰分含量。     

Dehumidification effects in the superheated region (SPR) of a direct expansion (DX) air cooling coil

A DX air cooling coil may normally be assumed to have two regions in its refrigerant side, according to refrigerant status, a two-phase region (TPR) and a superheated region (SPR). Dry air side surface of the SPR in a DX air cooling coil has been normally assumed in lumped-parameter mathematical models previously developed without however being validated. Therefore, an experimental study has been carried out to examine such an assumption under different operating conditions. The experimental results suggested that the air side surface of the SPR in a DX air cooling coil was either fully or partially wet under all experimental conditions and assuming dry air side of the SPR could lead to an underestimated total amount of water vapor condensed on the entire DX coil surface. Therefore, it is recommended that the assumption of dry air side in a SPR be no longer used in future lumped-parameter models to be developed for improved modeling accuracy.     

Hydrogen-rich gas from catalytic steam gasification of municipal solid waste (MSW): Influence of steam to MSW ratios and weight hourly space velocity on gas production and composition

The present work deals with a study coupling experiments and modeling of catalytic steam gasification of municipal solid waste (MSW) for producing hydrogen-rich gas or syngas (H₂ + CO) with calcined dolomite as a catalyst in a bench-scale downstream fixed bed reactor. The influence of steam to MSW ratios (S/M) on gas production and composition was studied at 900 °C over the S/M range of 0.39–1.04, for weight hourly space velocity (WHSV) in the range of 1.22–1.51 h⁻¹. Over the ranges of experimental conditions examined, calcined dolomite revealed better catalytic performance at the presence of steam. H₂ and CO₂ contents increased with S/M increasing, while CO and CH₄ contents decreased sharply, the contents of CH₄, C₂H₄ and C₂H₆ were relatively small, and the influence of S/M was insignificant. The highest H₂ content of 53.22 mol %, the highest H₂ yield of 42.98 mol H₂/kg MSW, and the highest H₂ potential yield of 59.83 mol H₂/kg MSW were achieved at the highest S/M level of 1.04. Furthermore, there was a good agreement between the experimental gas composition and that corresponding to thermodynamic equilibrium data calculated using GasEq model. Consequently, a kinetic model was proposed for describing the variation of H₂ yield and carbon conversion efficiency with S/M during the catalytic steam gasification of MSW. The kinetic model revealed a good performance between experimental results and the kinetic model.     

Novel conceptual design of a supercritical pulverized coal boiler utilizing high temperature air combustion (HTAC) technology

Technical and ecological aspects of implementation of High Temperature Air Combustion to power station boilers fired with pulverized coal have been considered. Several boiler concepts have been examined in the context of the following three key points: existence of an intensive in-furnace recirculation, homogeneity of both the temperature and the chemical species fields, and uniformity of heat fluxes. CFD-based numerical simulations have been performed in order to determine the shape of the boiler and its dimensions, to optimize both the distance between burners and location of the burner block. It was concluded that HTAC technology could be a realizable, efficient and clean technology for pulverized coal fired boilers.