Lige Tong

Contribution from Urban Heating to China's 2020 Goal of Emission Reduction

To reduce inhalable particle and SO(x) pollution from coal-based urban central heating (UCH), China has been vigorously developing natural gas-based UCH for years. The CO(2) emissions of UCH, having an average annual growth rate of 10.3%, accounted for 4.4% of Chinas total CO(2) emissions in 2009. This paper analyzes the feasibility of replacing UCH with heat pump heating (HPH) in Chinas climatic suitable regions and evaluates the corresponding potential for energy saving and emission reduction. Current strategy of replacing coal-based UCH with natural gas-based UCH is expected to decrease CO(2) emissions by 63.5%. However, the CO(2) emissions of HPH are 55.4% less than those of natural gas-based UCH. Replacing coal-based UCH with HPH is capable of decreasing CO(2) emissions by 83.7% and consequently decreases the CO(2) emissions per unit of gross domestic product (GDP) by 4.2% by 2020 compared with 2005 level. This contributes about 10.5% to Chinas 2020 CO(2) emission reduction target. For controlling environmental pollution and protecting ecological environment better, China should adjust its strategy for CO(2) emission reduction by shifting its attention from replacing coal-based UCH with natural gas-based UCH to popularizing HPH in climatic suitable regions.

Liquid Air Energy Storage

Abstract Liquid air energy storage refers to a technology that uses liquefied air or nitrogen as a storage medium. The chapter first introduces the concept and development history of the technology and then follows it up with thermodynamic analyses. Applications of the technology are then discussed through integration under different scenarios particularly with gas turbine-based peaking plants, nuclear power plants, solar thermal power generation, and liquefied natural gas regasification. Finally, comparisons are made between liquid air energy storage technology and a number of other energy storage technologies both technically and economically.

Field synergy characteristics in condensation heat transfer with non-condensable gas over a horizontal tube

Field synergy characteristics in condensation heat transfer with non-condensable gas (NCG) over a horizontal tube were numerically simulated. Consequently, synergy angles between velocity and pressure or temperature gradient fields, gas film layer thickness, and induced velocity and shear stress on gas–liquid interface were obtained. Results show that synergy angles between velocity and temperature gradient fields are within 73.2°–88.7° and ascend slightly with the increment in mainstream velocity and that the synergy is poor. However, the synergy angle between velocity and pressure gradient fields decreases intensively with the increase in mainstream velocity at θ ≤ 30°, thereby improving the pressure loss. As NCG mass fraction increases, the gas film layer thickness enlarges and the induced velocity and shear stress on gas–liquid interface decreases. The synergy angles between velocity and temperature gradient fields increase, and the synergy angles between velocity and pressure gradient fields change a...

Exergy analysis of air separation unit products

Air separation unit (ASU) is the largest energy consume plant, about 15%-20% consumption of overall energy in steel industry. Therefore, improving the operating efficiency of ASU is an effective way to achieve energy saving and emission reduction. The detail exergy calculation is presented in this study and the product exergy analysis of an actual 40000 Nm3/h ASU in Tangshan Tangsteel gases Co., Ltd. is evaluated using the developed exergy calculation program. The results show that: the molar exergy contained in oxygen is the largest among all gaseous products, liquid argon contains the largest molar exergy among all liquid products, and liquid products get larger exergy value than the gaseous. In a same environmental condition with a same air feed mass flow, the process would be more efficient by improving liquid production in the rated load operation of the expander.

Influence of Rotation on BN Separation in Binary Particle System

Granular particles systems under vertical vibration exhibit Brazilian Nut separation (BN), Reversed BN (RBN) separation or transitional phases at different vibrating conditions. In the present work, we investigate the influence of rotation on the BN separation of a binary granular particle system by changing rotational speed. 13X molecular sieve particles with diameter 6.00 mm and 0.60 mm are used. Vibration frequency f is 30 Hz and dimensionless acceleration Γ is 1.52 or 1.75, in which the particle system mainly exhibits BN separation tendency. Rotational speed ω varies from 0 to 150rpm, while the upper surface of the particle system maintains flat. We took the pictures of the particles distribution and measured the particles mass layer by layer to obtain the 3-D distribution of the particles. The results show that rotation enhances the BN separation tendency at slow rotational speed. The BN separation becomes strongest when ω is approximately 50rpm, then the BN separation tendency reduces as ω continues...

Size separation of binary mixture under vibration

By considering as a thermodynamic system, a minimum energy principle is established, in which the granular system changes its size distribution to make itself to be at the lowest energy state as soon as possible on the precondition that it dissipates all of the energy supplied from the vibrating bottom. A model is presented based on this principle to clarify why and how binary mixture separates under vibration. The small particles tend to sink in order to lower the kinetic energy of system, while the heavy particles sink in order to lower the potential energy. The mixture separates finally based on the competition between the two effects. The results of our model qualitatively agree with the previous researches.

Study on Nitridation of Silicon Added With Amorphous Silicon Nitride

The direct nitridation process of silicon added with amorphous silicon nitride powder at atmospheric pressure was investigated and the product was analyzed by XRD and SEM. Based on the relationship between the conversion ratio of silicon and the reaction time at different temperatures, a physical and mathematical model was derived to describe the nitridation process of silicon particles. The results showed that the conversion ratio of silicon increased rapidly at the early stage of reaction. And the reaction would be accelerated by reducing the size of silicon particle and increasing the pressure of N2 . At the range of experimental temperature, the conversion ratio of silicon increases with improving temperature.© 2011 ASME

Research and Development of Operation Simulation System for Cryogenic Air Separation Unit

In this paper an integrated operating simulation system (OSS) for a cryogenic air separation unit (ASU) is developed, which can be used for operators’ training, accident and malfunction analysis and prediction of operating result. Based on the method of modularization an ASU’s components are divided by their physical function. The OSS code includes two parts: the key simulation part which is developed in FORTRAN 5.0 and generally runs in background, and control simulating part which is primary running program and developed in iFix software. The communication between the key simulation part and control part is implemented by boundary module program. The OSS can realize the following operation simulation functions: normal state operation, startup operation and compressor, expander and other machines operations. The OSS has been tested for a 20000Nm3/hr ASU in Jinan Iron and Steel Corporation and 720000Nm3/hr ASU in Bao-Shan Steel Group Corporation in China. The simulating results of the OSS agree with the simulated counterpart.

A Distributed Model for Air-to-Refrigerant Fin-and-Tube Evaporators With Special Emphasis on Two-Phase Zone

A general and simple model for simulating the steady behavior of air-to-refrigerant fin-and-tube evaporators, which accounts for detailed flow state inside the tubes, is introduced. To account for the heat transfer between air and the working fluid, the evaporator is divided into a number of control volumes. Space dependent partial differential equations group is obtained from the mass, energy and momentum balances for each one. The corresponding discretized governing equations are solved afterwards. Empirical correlations are also required to estimate the void fraction, the internal and external heat transfer coefficients, as well as the pressure drops. According to the phase of refrigerating fluid, the evaporator can be divided into two distinct zones on the refrigerant-side: the vapor zone and the two-phase zone, while special emphasis is performed on the treatment of the two-phase zone. The distribution of flow pattern has been evaluated with the aim of improving the calculation accuracy. The model prediction is validated against experimental data for an evaporator using R22 as the working fluid, which shows a reasonable level of agreement: the cooling capacity is predicted within the error band of 3%. The developed model will have wide applications in operational optimization, performance assessment and pipeline design.© 2010 ASME

A Criteria for Size Separation Using Maximum Entropy Production

In order to study analytically the nature of the size separation in granular mixture, we present the maximum entropy production principle based on kinetic temperature of granular mixture. For simplicity we apply this principle to size separation of a sphere binary mixture in vibrated bed, and we find a new thermodynamic mechanism of size separation phenomenon. With the irreversible processes such as elastic collisions and frictions, the kinetic energy is dissipated rapidly in system, which induces the entropy production. By the fact that the entropy production rate always has the absolute maximum at the stable state of granular mixture, we find the crossover from “Brazil Nut Effect” to its reverse by changing particles size and density, and our result is about satisfied with Schnautz’s experiment.Copyright