Knee point-guided heterogeneous surrogate-assisted optimization for multi-objective coal gasification system

Modelling and energy analysis of an integrated coal gasification and pyrolysis system for synthetic natural gas

Thermodynamic analysis and optimization of coal supercritical water gasification system

Extremum Seeking Control of Carbon Monoxide Concentration in Underground Coal Gasification

Satellite constellation system design is a challenging and complicated multidisciplinary design optimization (MDO) problem involving a number of computation-intensive multidisciplinary analysis models. In this paper, the MDO problem of a constellation system consisting of small observation satellites is investigated to simultaneously achieve the preliminary design of constellation configuration and the satellite subsystems. The constellation is established based on Walker-? configuration considering the coverage performance. Coupled with the constellation configuration, several disciplines including payload, power, thermal control, and structure are taken into account for satellite subsystems design subject to various constraints (i.e., ground resolution, power usage, natural frequencies, etc.). Considering the mixed-integer and time-consuming behavior of satellite constellation system MDO problem, a novel sequential radial basis function (RBF) method using the support vector machine (SVM) for discrete-continuous mixed variables notated as SRBF-SVM-DC is proposed. In this method, a discrete-continuous variable sampling method is utilized to handle the discrete variables, i.e., the number of orbit planes and number of satellites, in the satellite constellation system MDO problem. RBF surrogates are constructed and gradually refined to represent the time-consuming simulations during optimization, which can efficiently lead the search to the optimum. Finally, the proposed SRBF-SVM-DC utilized to solve the satellite constellation system MDO problem is compared with a conventional integer coding based genetic algorithm (ICGA). The results show that SRBF-SVM-DC significantly decreases the system mass by about 28.63% subject to all the constraints, which greatly reduces the cost of the satellite constellation system. Moreover, the computational budget of SRBF-SVM-DC is saved by over 85% compared with ICGA, which demonstrates the effectiveness and practicality of the proposed surrogate assisted optimization approach for satellite constellation system design.

Pressurized pneumatic conveying plays an important role in large-scale coal gasification systems. Some of the underlying mechanisms affecting the conveying characteristics remain open issues. Phase diagrams can provide key information regarding flow characteristics by revealing the relationship between pressure drop and superficial gas velocity, which can be utilized for flow pattern identification, stability analysis, and system optimization, in an economic and feasible way. The present work experimentally investigated phase diagrams of pressurized pneumatic conveying on a pilot-scale setup, with three types of the most widely used pulverized coal in China selected as the conveyed materials. The effects of superficial gas velocity, solid-phase mass flow rate, pipeline layout, particle size, coal type, and moisture content were studied, respectively. The findings will contribute to a better understanding of the underlying mechanism of pressurized pneumatic conveying with pulverized coal, and to a better g...

A new system using combined coal gasification and combustion has been developed for clean and high efficient utilization of coal. Following are the processes. The coal is first partially gasified and the produced fuel gas is then used for industrial purpose or as a fuel for a gas turbine. The char residue from the gasifier is burned in a circulating fluidized bed combustor to generate steam for power generation. For having the experimental investigation, a 1MW pilot plant test facility has been erected. Experiments on coal partial gasification with air, and recycle gas have been made on the 1 MW pilot plant test facility. The results show that, with air as gasification agent, the system can produce 4–5MJ/Nm3 low heating value dry gas and fuel conversion efficiency attains 50–70% in the gasifier, and residue 20–40% converted in the combustor and total conversion efficiency in the system is over 90%. In the gasifier, the carbon conversion efficiency increases with the bed temperature and the air blown temperature. CaCO3 has an effective effect for sulfur removal in the gasifier. The sulfur removal efficiency attains 85% with Ca/S molar ratio 2.5. The system can produce 12–14MJ/Nm3 middle heating value day gas by using high temperature circulation solid as heat carrier and recycle gas or steam as gasification media, but the fuel conversion efficiency only attain 30–40% in the gasifier and most of fuel energy is converted in the combustor. CaCO3 has an obvious effect on tar cracking and H2S removal. The sulfur removal efficiency attains 80% with Ca/S molar ratio 2.5.

Advancements in micro-and nano-fabrication techniques are enabling the realization of high-performance metasurfaces which exploit the generalized Snell's law of refraction to achieve disruptive optical functionalities. Moreover, metasurfaces can be used in conjunction with conventional optical elements to achieve massive size, weight, and power (SWaP) reduction. However, no commercial tools exist which can efficiently model optical systems whose geometrical features span many orders-of-magnitude in spatial scale. Therefore, new forward solvers must be developed in order to make such multiscale problems tractable. Furthermore, optimization of multiscale optical systems is crucially-important in order to maximize system performance and minimize SWaP. While how one achieves a specific set of desired performances with conventional optical elements is generally well understood and thoroughly presented in design textbooks, it is not always clear how to design a nanoscale optical device to best achieve a desired set of performances. Therefore, a small subset of well-understood and/or canonical structures such as split-ring resonators are typically employed to achieve the targeted functionality. However, relaxing the device's topological constraints may lead to improved performance albeit at the expense of a larger solution space to explore. To mitigate this issue, we employ custom state-of-the art multi-objective and surrogate-assisted optimization algorithms to explore the solution space afforded by emerging manufacturing techniques in order to design metasurface topologies that achieve an arbitrary number of user-specified performance criteria.

Coal to SNG: Technical progress, modeling and system optimization through exergy analysis

Over the last 10 years, extensive research has been performed to evaluate the corrosion behavior of both metallic and refractory materials in multicomponent-gas and liquid-slag environments that are relevant to various coal gasification schemes. This paper examines the available information on metallic materials to give insight into the development of protective scales on alloy surfaces and causes of scale breakdown. Available long-term kinetic data on sound-metal loss are examined to evaluate the effects of alloy and gas chemistry on corrosion of materials in complex oxygen-sulfur atmospheres. In addition, the corrosion behavior of a variety of refractory materials after laboratory and pilot plant exposures is examined and wear mechanisms are discussed. From current knowledge of the process environments and of the behavior of metallic and refractory materials, a number of areas are identified for long-range research that can have significant impact on the design and performance of coal gasification plants.

Describes sophisticated electronic instrumentation and safety controls for coal gasification and liquefaction systems which are under development.

Distributed optical fiber temperature sensor (DTS) for underground coal gasification (UCG) system using is studied in this paper. By measuring temperature of reacting mine gasification process can be controlled. Calibration of DTS and experiment result are introduced. The results show that, DTS can play an important role in UCG systems.

Owing to analytical advances, submicron particles as small as 0.1 μm can be characterized for chemical composition, size, and shape using scanning electron microscopy (SEM). Once these characteristics are determined, the individual particles can be grouped into categories that provide size, shape, and chemical/mineral distributions of the fine particle fraction.An important application of submicron particle analysis is in solving ash-related problems in coal combustion and gasification systems. The Energy & Environmental Research Center (EERC) at the University of North Dakota is involved in an international consortium formed by the Electric Power Research Institute (EPRI), with U.S. Department of Energy Morgantown Energy Technology Center support, to study ash-related problems associated with the cleaning of hot gases in advanced energy systems. Before the gases are sent through a gas turbine to produce electricity, the particulates are removed with ceramic filters. Filters designed to trap the ash have a tendency to become plugged with ash, eventually causing operational problems. The focus of the project is to characterize the ashes from several filter systems to determine the mechanisms by which difficult-to-clean ash is formed and how it blinds hot-gas filters.

This report is an economic update of previous evaluations of various coal gasification and power generation systems. Capital and operating costs of all the systems have been escalated to mid-1978 dollars from their original mid-1976 basis. The processes studied included the Lurgi dry ash gasifier; the British Gas Corporation's Slagger; the Texaco entrained system; Combustion Engineering's two-stage entrained atmospheric pressure gasifier; Foster-Wheeler's two-stage entrained pressurized system; and the Tosco/HRI ToscoDyne process. For comparative purposes, a coal-fired steam electric generating station with stack gas desulfurization in subcritical and supercritical designs is also developed in this report. The plant sizes used in all of the screening studies are in the capacity range of 1000 MW to 1200 MW. These plants feed a constant coal rate equivalent to 10,000 tons/day of Illinois No. 6 coal. An annual average capacity factor of 70 percent is used to prepare a detailed analysis of operating costs for each study case. Operating costs are calculated for the first-year of operation and for an average cost during the 30-year plant life. The results of this study indicate that the installed plant costs have escalated by eleven to 19 percent from mid-1976 plant investment costs. Several more detailed results are given.

This article presents a non-stoichiometric equilibrium model based on the Gibbs free energy minimization method to analyze the effect of process parameters (temperature, pressure, equivalence ratio (ER), and steam/coal (S/C) ratio) on gasification of high-ash Indian coal and to find out optimum operating conditions for production of energy and chemicals. The model considers 16 elements distributed among 373 gas and 119 solid species. Effect of temperature is small when temperature is increased above ~ 1100 K. While increase in pressure brings operational benefits, effect of pressure on the gasification performance is very small. In general, with increase in ER, oxidative species start to dominate and, consequently, cold gas efficiency (CGE) decreases and carbon conversion (X) increases. CGE increases with increase in S/C ratio. The proposed methodology can be used for preliminary analysis and optimization of gasification system effectively in terms of cost and time.

An efficient and durable solid oxide fuel cell integrated with coal gasification system