Optimal greenhouse gas emissions in NGCC plants integrating life cycle assessment

The optimal design of an energy-intensive process involves a compromise between costs and greenhouse gas emissions, complicated by the interaction between optimal process emissions and supply chain emissions. We propose a method that combines generic abatement cost estimates and the results of existing (LCA) life cycle assessment studies, so that supply chain emissions are properly handled during optimization. This method is illustrated for a (NGCC) natural gas combined cycle power plant model with the following design and procurement options: procurement of natural gas from low-emissions producers, fuel substitution with (SNG) synthetic natural gas from wood, and variable-rate CO₂ capture and sequestration from both the NGCC and SNG plants. Using multi-objective optimization, we show two Pareto-optimal sets with and without the proposed LCA method. The latter can then be shown to misestimate CO₂ abatement costs by a few percent, penalizing alternate fuels and energy-efficient process configurations and leading to sub-optimal design decisions with potential net losses of the order of $1/MWh. Thus, the proposed LCA method can enhance the economic analysis of emissions abatement technologies and emissions legislation in general.     

带回热微型燃气轮机系统动态过程分析

分析了微型燃气轮机的动态数学模型,利用解析方法,求解了带回热单轴燃气轮机动态方程,对定转速和变转速两种情况下微型燃气轮机负荷变化和甩负荷的动态过程进行了仿真,提出了机组变工况动态性能优化和控制优化的途径。该研究能够为实际机组的运行和系统性能参数的合理匹配提供理论指导。     

扩散波模型在城市坡面汇流中的应用

为分析一维扩散波水动力方程在模拟城市地表降雨径流过程中的可行性,针对典型概化城市流域,采用一维扩散波水动力方程的数值解法模拟了一短历时强降雨事件,并对比SWMM模型模拟结果与扩散波模型模拟结果。结果表明,扩散波模型可以较好地体现降雨作用下地表径流过程的动力特点,但无法适用于过缓的地表坡度,解释了两者连续性方程的差异对模拟结果的影响,最后分析了扩散波模型下边界条件的确定方法。研究成果可为城市坡面汇流模拟提供参考。     

船用分轴燃气轮机动态过程的实时混合仿真

本文通过把发动机动态系统分解为与时间直接相关和无关的两个子系统的分析方法,探讨了实现发动机动态过程实时仿真的途径,提出了一个船用分轴燃气轮机动态过程实时仿真的方法,该方法可用于大扰动下发动机动态过程的实时仿真。用该方法在Dornier 960仿真机上作了某船用分轴燃气轮机加减速过程的实时仿真。所得的仿真结果实时记录曲线与相应的数字仿真结果完全一致。     

An MILP model for the reformation of natural gas pipeline networks with hydrogen injection

A mixed integer linear programming (MILP) model is proposed for the reformation of natural gas pipelines. The model is based on the topology of existing pipelines, the load and pressure at each node and the design factors of the region and minimizes the annual substitution depreciation cost of pipelines, the annual construction depreciation cost of compressor stations and the operating cost of existing compressor stations. Considering the nonlinear pressure drop equations, the model is linearized by a piecewise method and solved by the Gurobi optimizer. Two cases of natural gas pipeline networks with hydrogen injection are presented. Several adjustments are applied to the original natural gas pipeline network to ensure that our design scheme can satisfy the safety and economic requirements of gas transportation. Thus, this work is likely to serve as a decision-support tool for the reformation of pipeline networks with hydrogen injection.     

The role of biomass in US industrial interfuel substitution

The role of biomass in US industrial interfuel substitution in the industrial sector has typically been analyzed using data for the four traditional fuels of coal, oil, electricity and natural gas. However, the use of biomass as an industrial fuel in the US has grown, and now exceeds that of coal. Using data from 1960 to 2011, interfuel substitution in the US industrial sector is modeled with a dynamic linear logit model which includes biomass alongside the other four traditional fuels. Adding biomass to the model reduces somewhat the estimated own-price and cross-price elasticities for the other four fuels, while revealing that biomass and natural gas are substitute fuels. This implies that previous studies excluding biomass may have overestimated the potential for interfuel substitution, giving policy makers an inaccurate impression of the ability of carbon taxes or other environmental regulation to reduce greenhouse gas (GHG) emissions.     

大型锅炉长期动态特性研究中的烟气计算模型

为了简便、准确、快速地解决大空量锅炉汽轮机组长期动态特性研究中的烟气放热计算问题,本文针对现有仿真用烟气放热模型的主要不足,由大容量锅炉热力计算的杜卜斯基－卜劳赫公式推导出新的仿真与动态特性分析用炉膛烟气放热模型;并通过简要的分析、简化和推导,得出了动态过程中各种锅炉换热面烟气出口温度和放热量计算方法,这些烟气计算模型能够较为准确、简单地反映动态过程中高温烟气在大容量锅炉的炉膛和各烟道换热面的烟温及放热量的变化规律,应用十分方便。最后将本文的烟气计算模型应用于某600MW超临界机组的动态特性仿真,仿真结果合理、正确。     

船用燃气轮机动态安全性分析方法研究

针对船用燃气轮机动态安全性分析的困难，本文采用动态贝叶斯网络方法对动态故障树进行改进，建立用于动态安全性分析的动态贝叶斯网络模型。方法克服了动态故障树的缺点和不足，更加适合于燃气轮机动态安全性分析。实例分析表明了方法的正确性和优势。     

Enhancement of methanol production in a novel fluidized-bed hydrogen-permselective membrane reactor in the presence of catalyst deactivation

In this study, a dynamic model for a novel bubbling fluidized-bed membrane dual-type methanol reactor has been developed in the presence of long-term catalyst deactivation. The proposed model has been used to compare the performance of a novel fluidized-bed membrane dual-type methanol reactor (FMDMR) with membrane dual-type methanol reactor (MDMR) and conventional dual-type methanol reactor (CDMR). In this new concept, the feed synthesis gas is preheated in the tubes of the gas-cooled reactor and flowing in a counter-current mode with reacting gas mixture in the shell side. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas into the reaction side through the membrane. The outlet synthesis gas from this reactor is fed to tubes of the water-cooled packed-bed reactor and the chemical reaction is initiated by the catalyst. The methanol-containing gas leaving this reactor is directed into the shell of the gas-cooled reactor and the reactions are completed in this fluidized-bed side. This reactor configuration solves some observed drawbacks of new conventional dual-type methanol reactor such as pressure drop, internal mass transfer limitations, radial gradient of concentration and temperature in gas-cooled reactor. The proposed dynamic model has been validated against measured daily process data of a methanol plant recorded for a period of four years and a good agreement has been achieved. The simulation results show there is a favorable profile of temperature and activity along the fluidized-bed membrane dual-type reactor relative to membrane and conventional dual-type reactor systems. Therefore, the performance of methanol reactor system improves when membrane assisted fluidized-bed concept is used for conventional dual-type reactor system.     

喷水塔饱和器的动态建模与仿真

讨论了建立喷水塔饱和器的一维动态模型的方法。该方法将饱和器沿高度方向分解为若干段,每个段用气体和水滴模块表示。通过建立显式仿真模型,可以得到饱和器在稳定状态下和动态过程中参数的变化规律。根据模型稳定状态的数据。沿气体的主要流动方向,压力变化基本呈线性关系,而其它参数的变化为非线性。模型动态仿真结果表明,饱和器中气体压力和水之间的相互作用属于快过程,表现出与换热器不同的特点。     

Defrosting method adopting dual hot gas bypass for an air-to-air heat pump

A novel dual hot gas bypass defrosting (DHBD) method is developed to remove frost from the outside heat exchanger (HEX) of an air-to-air heat pump. The proposed method adopts two bypass lines of hot gas from the compressor: one is connected to the inlet of the outdoor HEX, and the other is connected to the outlet of the exchanger. We compare the dynamic performance and defrosting time of the conventional reverse cycle defrosting (RCD), hot gas bypass cycle defrosting (HGBD), and DHBD methods using a medium air-to-air 16 kW heat pump. The salient feature of the DHBD method is its ability to prevent a sharp decrease in the compressor outlet temperature at the melting frost stage after the HGBD process begins. Due to the additional bypass, the DHBD method sustained a higher compressor outlet pressure and reduced the defrosting time by 36% compared to the HGBD method. Compared to RCD, the defrosting time was comparable (126%); however, the amenity characteristics of the DHBD method were superior than those of the RCD method. The proposed DHBD method can overcome the main disadvantages of the RCD and HGBD methods, and showed excellent performance for an air-to-air heat pump in a defrosting operation.     

New approach to gas network modeling in unit commitment

Expansion of gas fired units installation in power network results in more interdependency between gas and electric infrastructures. Thus new research has paid attention to the impact of gas network in power system studies. One such issue is the impact of gas network in a unit commitment problem. Many linear and nonlinear models are proposed to demonstrate this impact. However, the dynamics of these two infrastructures are different. In contrary to an electric network, the dynamic of a gas network lasts over a long period. In large scale networks, the impact of gas volume variations may remain for some hours or even for a whole day. Earlier research considered a gas network static model by which its dynamic behavior was not observed. In this paper, the quasi dynamic model is proposed for a gas network by which gas velocity and distances between gas areas may be considered. This model is assessed for a unit commitment problem on a test network and its capabilities are appreciated.     

基于SIMULNK的单轴重型燃气轮机建模与仿真研究

通过面向对象的模块化建模方法,在MATLAB／SIMULINK软件中建立了燃气轮机部件模块库,并进行了燃气轮机系统变工况仿真研究。为了提高仿真精度,本文采用变比热容的计算方法,并考虑气体组分的变化对整个系统模型的影响,建立了一种考虑容积惯性和转动惯性的、非线性的单轴重型燃气轮机实时动态仿真模型。仿真结果表明,该模型设计合理、结构清晰,可应用于重型燃气轮机控制系统的研制和测试,并具有很好的通用性和扩展性。     

基于改进牛顿法的燃-燃联合动力装置建模方法研究

燃-燃联合动力装置(COGAG)以其功率密度大、机动性好等优势,在船舶动力领域展现了很好的发展前景。对燃-燃联合动力装置的部件进行了模块化建模,为提高模型的计算效率和收敛性,对传统的牛顿拉普森（Newton Rapson）迭代法进行改进,建立了COGAG稳态模型。利用四阶龙格库塔法建立动态模型,在python仿真环境下对建模方法进行了仿真验证。仿真结果表明：提出的基于改进牛顿法的燃-燃联合动力装置的建模方法可以实现系统的稳态和动态运行过程,提高了模型稳态计算的收敛速度,为联合动力装置的响应特性研究和控制器的设计提供了模型基础。     

某型燃气轮机发电机组大负荷突卸时动态特性仿真与试验研究

为系统研究某型20 MW级三轴燃气轮机发电机组动态特性,在热力学循环分析的基础上,建立燃气轮机发电机组的动态特性数学模型,基于MATLAB/SIMULINK仿真平台建立其动态仿真模型,针对未来舰船常用的大负荷突卸(12 MW突卸至2 MW)时的动态过程进行了仿真,对其动态仿真和试验进行了对比分析。结果表明:仿真与试验具有较好的吻合性;针对大负荷突卸过程中存在的积分饱和问题,提出采用具有抗积分饱和的控制方法,可有效降低机组稳定时间,提高机组的动态响应,为后续机组控制方法调整提供有力的技术支撑。     

Prioritizing the alternatives of the natural gas grid conversion to hydrogen using a hybrid interval rough based Dombi MARCOS model

The aim of this study is to disclose an integrated multi-criteria decision making model as an instrument able to be used for hydrogen gas grid development via natural gas network conversion by considering four main criteria and sixteen sub-criteria. The proposed model consists of two stages using interval rough based Dombi MARCOS (Measurement Alternatives and Ranking according to the COmpromise Solution) method. In the first stage, the interval rough Bonferroni logarithmic methodology of additive weights is applied for determining the weight coefficients. In the second stage, the improved interval rough MARCOS method is used to rank the alternatives. A case study for hydrogen gas grid development in Romania set out the applicability and effectiveness of the proposed model. The proposed model is analysed from various points of view so that it can be used effectively in reality not only theoretically. This study analyzes four technical alternatives for hydrogen gas grid development. The results show that the conversion for mixtures natural gas with hydrogen a transporting a mix of gases is the best alternative among the four alternatives, for the next period and in the specific context described by this study. The current technical-economic criteria are rather a constraint when discussing gas infrastructures. For choosing a sustainable solution, a major role comes for decision makers, along with the desire to pay fairly from the consumer.     

An MILP model for optimization of byproduct gases in the integrated iron and steel plant

In iron and steel industry, byproduct gases are important energy. Therefore it is significant to optimize byproduct gas distribution to achieve total cost reduction. In this paper, a dynamic mixed integer linear programming (MILP) model for multi-period optimization of byproduct gases is used to optimize byproduct gas distribution. Compared with the previous optimization model, the proposed model simultaneously optimizes the distribution of byproduct gases in byproduct gas system, cogeneration system and iron- and steel-making system. Case study shows that the proposed model finds the optimal solution in terms of total cost reduction.     

Improving air quality in large cities by substituting natural gas for coal in China: changing idea and incentive policy implications

Natural gas has long been used in China mainly as chemical raw material. With the increasing emphasis on urban air pollution prevention, the issue of natural gas substitution to coal has been raised in many large Chinese cities. This paper reviews the environmental–economic–technical rationality of dashing-for-gas in urban area, especially for civil use such as cooking and heating in China. Taking Beijing and Chongqing as study cases, a cost–benefit analysis of natural gas substitution is done and the ongoing economic and system barriers to natural gas penetration are analyzed. Indications of natural gas penetration incentive policy making are given finally.     

超临界锅炉风烟系统的流体网络动态数学模型

介绍了2种流体网络建模方法--节点压力法和网络法,并通过实例比较了2种方法的静态计算结果和动态响应过程,结果表明:网络法模型计算精度高,收敛速度快,可以快速响应压力的变化.在详细分析超临界锅炉风烟系统的基础上,建立了系统流动阻力的数学模型,采用模块化的建模思想编制了风烟系统的仿真算法,并在仿真平台Simpanel上对其静态和动态特性进行了仿真研究.通过分析表明:所建立的风烟系统仿真模型具有良好的静态精度和动态响应特性,能够满足仿真实时性的要求.