废水超临界水热气化过程建模及优化

以橄榄油厂废水为对象,在超临界水条件下,建立了橄榄油废水水热气化过程最小二乘支持向量机模型,依据实验数据对所建模型做了计算验证。结果表明,模型预测值与实验值最大相对误差绝对值为7.82%,平均值为3.5%左右,该模型可较好地模拟橄榄油厂废水在超临界水中的水热气化过程。在模型的基础上,设计拟合了水热气化过程多目标优化函数,寻优得到最优解集。优化结果表明,气化气有效组分CH4,H2含量及废水总有机碳(TOC)转化率都与实验最大值接近。

热气化生物质制氢催化剂及热力学分析研究

在反应过程中加入催化剂可在更温和的水热条件下实现生物质高效气化制氢。在众多催化剂中,Ni系催化剂因其廉价并在反应中表现出较高的活性等优点而被认为是很有发展前景的制氢催化剂。该课题组针对Ni/Al_2O_3酸性位易于积碳引起催化剂失活的弱点,通过金属助剂的辅助作用对Al_2O_3为载体的负载Ni催化剂进行改性。选用Cu、Co、Sn、Ce和碱性Mg,通过共浸渍、分步浸渍和共沉淀等方法制备双金属Ni-M或者复合氧化物载体催化剂。结果表明,金属助剂Ce的引入有效提高了Ni系催化剂的催化产氢活性,催化剂的抗积碳性能亦得到有效改进,表明金属Ce是非常合适的金属助剂。MgAl_2O_4使催化剂水热稳定性得到改善,碱性Mg助剂可以有效抑制Ni-Al催化剂的表面结晶碳的形成。较低的热处理温度,或者分步浸渍制备Ni-Mg-Al催化剂能获取更多有效的活性位。碱性Mg助剂可以改善Ni-Al催化剂的催化活性及水热稳定性。对于溶胶-凝胶法制备的Rutile TiO_2负载Ni催化剂,降低催化剂热处理温度可以获取分散性更高的Ni晶粒,从而提供较多的活性位,以促进生物质在水热条件下C-C键的断裂,水汽转化反应和甲烷化反应,从而提高生物质转化率。通过利用Aspen Plus软件根据Gibbs自由能最小化原理采用PR状态方程,以MHV2混合规则建立热力学模型来模拟水热条件下气化生物质及其模型化合物产氢的过程,对水热气化生物质及模型化合物进行了理论分析,计算出在一定温度和压力条件下达到平衡时系统的产气量,提供了催化气化生物质的方向和限度的数据。

Growth of Cu/SSZ-13 on SiC for selective catalytic reduction of NO with NH_3

Silicon carbide(SiC)was used as a support for SSZ‐13zeolite in an attempt to improve the high‐temperature stability and activity of Cu/SSZ‐13in the selective catalytic reduction(SCR)of NO with NH3.SSZ‐13was grown via a hydrothermal method using the silicon and silica contained in SiC as the source of silicon,which led to the formation of a chemically bonded SSZ‐13layer on SiC.Characterization using X‐ray diffraction,scanning electron microscopy,and N2adsorption‐desorption isotherms revealed that the alkali content strongly affected the purity of zeolite and the crystallization time affected the coverage and crystallinity of the zeolite layer.Upon ion exchange,the resulting Cu/SSZ‐13@SiC catalyst exhibited enhanced activity in NH3‐SCR in the high‐temperature region compared with the unsupported Cu/SSZ‐13.Thus,the application temperature was extended with the use of SiC as the support.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

CAS FGOALS-f3-H and CAS FGOALS-f3-L outputs for the high-resolution model intercomparison project simulation of CMIP6

The High Resolution Model Intercomparison Project(HighResMIP)is a unique model intercomparison project in phase 6 of the Coupled Model Intercomparison Project(CMIP6),which is focused on the impact of horizontal resolutions.The outputs of the high-and low-resolution versions of CAS FGOALS-f3-H and CAS FGOALS-f3-L for the experiments of the HighResMIP simulations in CMIP6 are described in this paper.The models and their configurations,experimental settings,and postprocessing methods are all introduced.CAS FGOALS-f3-H,with a 0.25°horizontal resolution,and CAS FGOALS-f3-L,with a 1°horizontal resolution,were forced by the standard external conditions,and two coordinated sets of simulations were conducted for 1950–2014 and 2015–50 with the Experiment IDs of‘highresSST-present’and‘highresSST-future’,respectively.The model outputs contain multiple time scales including the required hourly mean,three-hourly mean,six-hourly transient,daily mean,and monthly mean datasets.It is reported that the 0.25°CAS FGOALS-f3-H successfully simulates some of the key challenges in climate modeling,including the average lifetime of tropical cyclones,particularly in the western parts of the northern Pacific Ocean,and the diurnal cycle of hourly precipitation.These datasets will contribute to the benchmarking of current models for CMIP,and studies of the impacts of horizontal resolutions on climate modeling issues.

Enhanced-hydrogen gas production through underground gasification of lignite

Underground coal gasification is one of the clean technologies of in-situ coal utilization.Hydrogen production from underground gasification of lignite was investigated in this study based on simulation experiments.Pyrolysis of lignite, gasification activity, oxygen-steam gasification and the effect of groundwater influx were studied.As well, the advantages of lignite for stable underground gasification were analyzed.The results indicate that lignite has a high activity for gasification.Coal pyrolysis is an important source of hydrogen emission.Under special heating conditions, hydrogen is released from coal seams at temperatures above 350 °C and reaches its maximum value between 725 and 825 °C.Gas with a hydrogen concentration of 40% to 50% can be continuously obtained by oxygen-steam injection at an optimum ratio of steam to oxygen, while lignite properties will ensure stable gasification.Groundwater influx can be utilized for hydrogen preparation under certain geological conditions through pressure control.Therefore, enhanced-hydrogen gas production through underground gasification of lignite has experimentally been proved.

Optimal design of heat exchanger header for coal gasification in supercritical water through CFD simulations

Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.

Full-Scale Measurement and Numerical Analysis of Liquefied Petroleum Gas Water Heaters with Ventilation Factors in Balcony

This study carried out full-scale gas water heater combustion experiments and adopted FDS （fire dynamics simulator） to simulate three scenarios--different balcony environments when using water heater, such as airtight balcony, indoor door with openings and force ventilation to compare with full-scale combustion experiments. According to FDS simulation results, 02, CO and CO2 simulation concentration value correspond with full-scale experimental results. When the indoor O2 concentration was lower than 15%, which causes incomplete combustion, the CO concentration would rise rapidly and even reached above 1,500 ppm, causing death in short time. In addition, when the force ventilation model supplied the water heater with enough air to bum, the indoor CO concentration will keep low and harmless to humans. The study also adopted diverse variables, such as the opening area of window, outdoor wind speed and water heater types, to analyze deeply user＇s safety regarding gas water heater. In a result, while balcony area is larger than 14 mE, the volume of water heater is below 16 L （33.1 kW）, and the indoor window, connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is larger than 0.2 mE, this can ensure the personal security of the indoor space.

Simulation of Gas-Fired Triple-Effect LiBr/Water Absorption Cooling System with Exhaust Heat Recovery Generator

An exhaust heat recovery generator is proposed to be integrated with conventional gas-fired triple-effect LiBr/water absorption cooling cycles to improve system energy efficiency. As a case study, simulation of the novel cycle based on promising parallel flow with cooling capacity of 1 150 kW is carried out under various heat recovery generator vapor production ratios ranging from 0 to 3.5%. The life cycle saving economic analysis, for which the annual gas conservation is estimated with Bin method, is employed to prove the worthiness of extra expenditure. Results show that the optimum gas saving revenue is obtained at 2.8% heat recovery generator vapor production ratio with 42 kW exhaust heat recovered, and the system energy efficiency is improved from 1.78 to 1.83. The initial investment of exchanger can be paid back within 7 years and 9 000 CNY of gas saving revenue will be achieved over the 15-year life cycle of the machine. This technology can be easily implemented and present desirable economic effects, which is feasible to the development of triple-effect absorption cycles.

Impacts of Climate Change and Human Activities on Water Suitability in the Upper and Middle Reaches of the Tao'er River Area

Due to the impact of climate change and human activities, the upper and middle reaches of the Tao＇er River have become an ecologically sensitive area in Northeast China. It is important to evaluate the contributions of climate change and human activities to water suitability in the Tao＇er River area. From the perspective of water and heat balance, the water suitability index （Cr） was used to analyze the water suitability of the upper and middle reaches of the river. The nonparametric Mann-Kendall, moving t-test and cumulative anomaly methods were used to detect abrupt changes in Taonan station runoff from 1961 to 2012. Three inflexion years were detected. Thus, the entire time period was divided into four periods： 1961-1974, 1975-1983, 1984-1998, and 1999-2012. In order to estimate the impacts of climate change and human activities on runoff, the slope change ratio of cumulative quan- tity （SCRCQ） was adopted. Finally, the contribution of climate change and human activity to Cr was transformed from the contribution of climate change and human activity to runoff by the sensitivity coefficient method and SCIRCQ method. The results showed that the water suitability index （cr） had a decreasing trend 1961-2012. Fac- tors influencing cr, such as net radiation and runoff, also exhibited a decreasing trend, while precipitation exhibited an increasing trend over the past 52 years. The trends of Cr, net radiation and runoff were obvious, which passed the Mann-kendall test of significance at a=0.05. Human activities were the main factors that affected runoff, al- though the degree of impact was different at different times. During the past 52 years, the biggest contributor to the change in Cr was precipitation.