天然气水合物生成焓的实验研究

This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kPa(1000psi). The measurements were made in a multi-cell differential scanning calorimeter using modified high pressure cells. The enthalpy of water and the enthalpy of dissociation of the gas hydrate were determined from the calorimeter response during slow temperature scanning at constant pressure. The amount of gas released from the dissociation of hydrate was determined from the pumped volume of the high pressure pump. The occupation ratio (mole ratio) of the water to gas and the enthalpy of hydrate formation are subject to uncertainty of 1.5%.The results show that the enthalpy of hydrate formation and the occupation ratio are essentially independent of pressure.     

环戊烷/水乳化液水合法捕获烟道气中CO_2(英文)

Capture of CO2 by hydrate is one of the attractive technologies for reducing greenhouse effect.The primary challenges are the large energy consumption,low hydrate formation rate and separation efficiency.This work presents a new method for capture of CO2 from simulated flue gasCO2(16.60%,by mole) /N2 binary mixture by formation of cyclopentane(CP) hydrates at initial temperature of 8.1°C with the feed pressures from 2.49 to 3.95 MPa.The effect of cyclopentane and cyclopentane/water emulsion on the hydrate formation rate and CO2 separation efficiency was studied in a 1000 ml stirred reactor.The results showed the hydrate formation rate could be increased remarkably with cyclopentane/water emulsion.CO2 could be enriched to 43.97%(by mole) and 35.29%(by mole) from simulated flue gas with cyclopentane and cyclopentane/water(O/W) emulsion,respectively,by one stage hydrate separation under low feed pressure.CO2 separation factor with cyclopentane was 6.18,higher than that with cyclopentane/water emulsion(4.01) ,in the range of the feed pressure.The results demonstrated that cyclopentane/water emulsion is a good additive for efficient hydrate capture of CO2.     

Metastable state of gas hydrate during decomposition: A novel phenomenon

Natural gas hydrates are solid compounds with cage-like structures formed by gas and water. An intriguing phenomenon that gas hydrates can dissociate at a low rate below the ice freezing point has been viewed as the metastability of hydrate. The mechanisms of hydrate metastability have been widely studied, and many mechanisms were proposed involving the self-preservation effect, supercooled water-gas-hydrate metastable equilibrium, and supersaturated liquid–gas-hydrate system etc. The metastable state of hydrate could be of crucial significance in the kinetics of hydrate formation and decomposition, heat and mass transfer during gas production processes, and the application of hydrate-based technique involving desalination, energy storage and transportation, and gas separation and sequestration. Few researches have systematically considered this phenomenon, and its mechanism remains unclear.In this work, various mechanisms and hypothesis explaining the metastable state of gas hydrates were introduced and discussed. Further studies are still required to reveal the intrinsic nature of this metastable state of gas hydrate,and this work could give some implications on the existing theory and current status of relevant efforts.     

甲烷水合物在纯水和抑制剂体系中的生成动力学

Kinetic data of methane hydrate formation in the presence of pure water,brines with single salt and mixed salts,and aqueous solutions of ethylene glycol(EG) and salt EG were measured.A new kinetic model of hydrate formation for the methane water systems was developed based on a four-step formation mechanism and reaction kinetic approach.The proposed kinetic model predicts the kinetic behavior of methane hydrate formation in pure water with good accuracy.The feasibility of extending the kenetic model of salt(s) and EG containing systems was explored.     

EXPERIMENTAL INVESTIGATION ON GAS HYDRATE FORMATION IN PRESENCE OF ADDITIVE COMPONENTS

Additives were used to increase gas hydrate formation rate and storage capacity. Experimental tests of methane hydrate formation were carried out in surfactant water solutions in a high-pressure cell. Sodium dodecyl sulfate (SDS) and alkyl polysaccharide glycoside (APG) were used to increase hydrate formation. The effect of SDS on hydrate formation is more pronounced compared APG. Cyclopentane (CP) also improves hydrate formation rates while it cannot increase methane gas storage capacity.     

水合物法分离H2+CH4体系的模拟计算

This paper presents two novel conceptions in multi-stage hydrate separation technology for H2 CH4 system, i.e. the multi-stage equilibria adsorption and the reaction adsorption. It is assumed that there already exists clathrate structure before the hydration reaction, and the hydration reaction is taken as gaseous adsorption in the crystal structure of hydrate. During the simulation of multi-stage equilibria adsorption, gases and water interact on every equilibrium stage till establishing full equilibria, wherein the gases that just entered one stage are in equilibrium with the liquid phase of the previous stage, and the water that just entered one stage is in equilibrium with the gas phase of the previous stage as well. A kinetic model of hydrate growth for methane is introduced into the reaction adsorption so that this simulation is closer to the reality. As hydrogen doesn‘t react with water to form hydrate, the amount of hydrogen adsorption is calculated according to the proportion of methane and hydrogen adsorbed in the small cavities. Simultaneously, the plate column is employed as an example, where the gas-hydrate phase loads and hydrogen mole fraction are calculated by the multi-stage equilibria adsorption and reaction adsorption methods, and the results calculated by the two said methods are compared.     

利用吸收-水合耦合法从氨弛放气中回收氢气的研究(英文)

In this work, the absorption-hydration hybrid method was used to recover (hydrogen + nitrogen) from (hydrogen + nitrogen + methane + argon) tail gas mixtures of synthetic ammonia plant through hydrate forma-tion/dissociation. A high-pressure reactor with magnetic stirrer was used to study the separation efficiency. The in-fluences of the concentration of anti-agglomerant, temperature, pressure, initial gas-liquid volume ratio, and oil-water volume ratio on the separation efficiency were systematically investigated in the presence of tetrahydro-furan (THF). Anti-agglomerant was used to disperse hydrate particles into the condensate phase for water-in-oil emulsion system. Since nitrogen is the material for ammonia production, the objective production in our separation process is (hydrogen + nitrogen). Our experimental results show that by adopting appropriate operating conditions, high concentration of (hydrogen + nitrogen) can be obtained using the proposed technology based on forming hydrate.     

A型分子筛对甲烷水合物生成的影响

The porous medium has an important effect on hydrate formation. In this paper, the formation process and the gas storage capacity of the methane hydrate were investigated with A-type zeolite and Sodium Dodecyl Sulfate (SDS) existing in the system. The results show that A-type zeolite can influence methane hydrate formation. At the temperature of 273.5 K and pressure of 8.3 MPa, the distilled water with A-type zeolite can form methane hydrate with gaseous methane in 12 hours. The formation process of the system with A-type zeolite was quite steady and the amount of A-type zeolite can influence the gas storage capacity significantly. The adding of A-type zeolite with 0.067 g•(g water)－1 into 2×10－3 g•g－1 SDS-water solution can increase the gas storage capacity, and the maxi-mum increase rate was 31%. Simultaneously the promotion effect on hydrate formation of 3A-type zeolite is much more obvious than that of 5A-type zeolite when the water adding amounts are 0.033 g•g－1 and 0.067 g•g－1 at the experimental conditions.     

吸附分离CH4/N2可行性研究

The separation between methane and nitrogen is an inevitable and important task in the C1 chemical technology and the utilization of methane from coalbed, yet it is considered to be one of the tough tasks in the field of separation. Pressure swing adsorption is a preferable technology if an adsorbent that allowing a large coefficient of separation for the CH4/N2 system is available. The separation coefficients between CH4 and N2 were obtained on analyzing the breakthrough curves measured experimentally with nine adsorbents. A technique of measuring the temperature-pulse was incorporated in the experiments, and the reliability of the result was improved.Superactivated carbon with large surface area and plenty of micropores was shown to have the largest separation coefficient and to be promising for the commercial utilization.     

气相温度脉动对碳黑生成反应的影响(英文)

The effects of gas temperature fluctuations on soot formation and oxidation reactions are investigated numerically in a reacting flow. The instantaneous variations of soot mass fraction with time are obtained under the time-averaged gas temperature of 1500-1700 K. The simulation results show that the gas temperature fluctuation has obvious influence on the instantaneous processes of soot formation and oxidation. Within the present range of gas temperature, the gas temperature fluctuation results in generally lower soot mass fraction comparing to that without gas temperature fluctuation. The increase in the fluctuation amplitude of gas temperature leads to decrease in time-averaged soot mass fraction and increase in time-averaged soot particle number density.     

水合物法分离低浓度煤层气中的甲烷

向模拟煤层气(13.11vol% CH4+86.89vol% N2)中添加5.8mol%四氢呋喃(THF)?0.03mol%十二烷基硫酸钠(SDS)促进剂溶液分离提纯煤层气,考察了压力、温度、反应时间对气体消耗量、反应速率、分解气中甲烷浓度、甲烷回收率和甲烷分离因子的影响,采用色谱分析法分别测定了CH4在剩余气相和分解气相中的浓度。结果表明,压力增加,CH4回收率增大,CH4分离因子增大,CH4分离效果越好;温度是影响甲烷分离因子的关键因素,温度降低,氮气和甲烷竞争进入水合物晶体中,导致水合物相中甲烷浓度降低;温度升高有利于提高水合物对甲烷的选择性。甲烷回收效率最高可达98.65%,分离因子最大为14.83。随反应时间增加,分解气中CH4浓度升高。     

煤层气水合物定容生成实验研究

为了有效利用与回收直接排放的大量抽放瓦斯,提出了利用水合物技术处理与储运的新方法,根据气体成分确立了水合物生成的温度与压力条件,通过对气体进行初始压力为9.5 MPa的定容法实验,研究了含表面活性剂下水合物生成过程中温度-压力与CH4转化率的变化规律。实验结果表明,水合反应的进行应保持一定的反应驱动力,根据不同温度下反应驱动力进而确定最佳反应条件,同时反应过程中CH4能被有效提取,但要进行高效生产,应进行多级水合分离技术以提高产率。     

Research progress in hydrate-based technologies and processes in China: A review

Natural gas hydrate (NGH) is considered as an alternative energy resource in the future as it is proven to contain about 2 times carbon resources of those contained in the fossil energy on Earth. Gas hydrate technology is a new technology which can be extensively used in methane production from NGH, gas separation and purification, gas transportation, sea-water desalination, pipeline safety and phase change energy storage, etc. Since the 1980s, the gas hydrate technology has become a research hotspot worldwide because of its relatively economic and environmental friendly characteristics. China is a big energy consuming country with coal as a dominant energy. With the development of the society, energy shortage and environmental pollution are becoming great obstacles to the progress of the country. Therefore, in order to ensure the sustainable development of the society, it is of great significance to develop and utilize NGH and vigorously develop the gas hydrate technology. In this paper, the research advances in hydrate-based processes in China are comprehensively reviewed from different aspects, mainly including gas separation and purification, hydrate formation inhibition, sea-water desalination and methane exploitation from NGH by CH₄-CO₂ replacement. We are trying to show the relevant research in China, and at the same time, summarize the characteristics of the research and put forward the corresponding problems in a technical way.     

低浓度煤层气吸附浓缩技术研究与发展

我国是一个多煤少气贫油的国家,煤层气储量约30万亿立方米,由于缺乏先进实用的低浓度煤层气甲烷分离浓缩技术,当前抽采煤层气利用率仅为50%左右。因此,对低浓度煤层气甲烷富集浓缩过程开展研究,可在开发能源的同时减少温室气体的排放,具有重大的应用价值和战略意义。简要介绍了我国煤层气资源开发利用情况,综述了近年来低浓度煤层气吸附浓缩技术研究进展,包括新型吸附材料及先进吸附工艺。对于低浓度煤层气中CH₄/N₂分离,目前文献报道吸附材料的吸附容量及分离系数仍然处于较低水平;受吸附材料的分离性能较差影响,传统变压吸附工艺对低浓度煤层气中CH₄浓缩效果并不理想。最后指出,高吸附容量、高选择性吸附材料及多种方法结合的新型吸附工艺是未来低浓度煤层气吸附浓缩技术的发展方向。     

基于水合物的混空煤层气分离技术

混合气体的水合物法分离是一项具有广阔应用前景的新技术。在对气体水合物理论、应用技术进行概述的基础上,针对抽采煤层气混掺空气的现状,提出一种新工艺:将原料气引入反应器中,控制温度和压力,在特定条件下生成甲烷水合物,排出非水合气体—空气,实现煤层气的净化提浓。生成的甲烷水合物,或气化后经管道输送,或装罐储存。水合物的快速合成是分离技术的关键。     

Improving the gas recovery and separation efficiency of a hydrate-based gas separation

Efficient gas recovery and separation in a hydrate-based system was investigated for a model gaseous mixture of R22 and nitrogen. The formed hydrate settled in the recovery vessel; excess water was recycled and the hydrate was subsequently decomposed by releasing pressure from the vessel. The gas uptake rate of R22 gas from the vapor phase and the gas recovery rate from the hydrate were determined from hydrate formation and decomposition, respectively. The gas recovery rate of R22 gas gradually increased with time. On the contrary, the nitrogen gas recovery rate was a maximum in the initial stage of hydrate decomposition. A high separation factor (S.F.) was achieved by first separating the N₂-rich gas generated during initial hydrate decomposition. An efficient hydrate-based gas separation and recovery process is proposed.     

水合物法提纯沼气技术研究进展

沼气是一种重要的可再生能源,对沼气进行充分高值利用对于缓解我国能源需求和环境压力具有重要意义。沼气在高值利用前必须进行脱碳提纯处理,本文介绍了一种可用于沼气提纯的新技术--水合物分离技术。介绍了水合物分离技术的基本理论,调研总结了水合物法提纯沼气和可用于沼气体系（CH₄/CO₂）的水合物分离技术研究进展,包括相平衡研究、热力学促进剂、动力学促进剂、机械强化、外场强化、添加多孔介质/纳米流体等和采用油/水乳液促进技术,并对各种水合物分离促进技术进行了分析：相平衡研究为水合物法提纯沼气提供了理论基础;合理地选用热力学和动力学促进剂能够有效改善气体水合物相平衡条件,促进水合物生成,增加储气效果和提高分离效率;机械强化及外场作用通过强化水合反应过程的传质传热效果促进水合物生成;添加多孔介质和纳米流体等能够增大气液接触面积,对水合过程发挥促进作用;采用油/水乳液不但能够强化气液接触,而且微乳状态下的水合物具有很好的流动性,具有良好工业应用前景。最后对水合物法提纯沼气技术进行了展望,水合物提纯沼气研究虽处在起步阶段,但随着研究的不断深入,该技术凭借操作条件温和,对原料气要求低,并且具有操作简单灵活、安全性高、环保无污染等优点,必将在我国沼气产业发展过程中发挥作用。     

TBAB和CP双添加剂水合物法分离烟气中的CO2

在四正丁基溴化铵（TBAB）和环戊烷（CP）双添加剂体系下进行了一级水合物法分离烟气中CO2的研究。对比了纯体系和双添加剂体系对水合物生成过程及分离效果的影响。获得了合适的操作条件（温度276.15 K,压力2.0～3.3 MPa）、初始液气比（0.78）、添加剂浓度（CP体积分数为0.6%）。在合适条件下,双添加剂体系相比纯TBAB体系水合过程的载气量达至1.5～2.0倍,剩余气相中CO2摩尔分数由17%降至7%,去除率由40%～50%上升到60%～70%。实验表明,双添加剂体系在水合物法CO2分离技术的分离效果及节能方面存在潜力,为工业化水合物法净化烟气提供了参考和标准。     

用低质煤层气(CMM)制氨的探讨

本文叙述了一种利用低质矿井区煤层气(CMM)[甲烷含量30%(φ)左右]制氨合成气的工艺及有关工艺条件的影响。低质煤层气通过自热转化制气,经变换,变压吸附脱氮,脱碳,制得氢氮体积分数之比为3的氨合成气。对于含30%(φ)甲烷的煤层气,脱氮成本112元/吨氨,由于低质煤层气价格较低,以折纯甲烷0.60元/Nm3计,脱氮后相当于纯甲烷价格为0.714元/Nm3,故具有较好的经济效益、环境效益和社会效益。氨可进一步加工为硝酸、或硝酸铵、或磷酸铵等,则可获得更大的经济效益。     

水合物法平衡级分离CO2/N2流程模拟分析

化石燃料燃烧排放烟气中CO₂的量占CO₂总排放量的75%,为了缓解CO₂导致的全球温室效应,需将CO₂/N₂中的CO₂分离出来。水合物法分离是一种高效、低能耗的CO₂/N₂分离技术。本文研究了水合物法平衡级分离CO₂/N₂过程中,进料CO₂体积分数、反应条件与反应特性三者间的关系,利用CPA-SRK方程+Chen-Guo模型对其进行平衡级分离流程模拟分析。经计算发现,进料干基CO₂体积分数对水合物法分离CO₂/N₂工艺的反应压力、平衡级级数均有较大影响。随着体积分数的增加,反应压力呈减小趋势,减小幅度随体积分数增加而减小,当进料CO₂体积分数小于20%时,压力下降较快,当体积分数大于50%时,压力降低幅度变小。温度为277K时,CO₂体积分数小于10%时,需四个水合物平衡级分离才能得到满足要求的气样;当体积分数为10%~20%时,需三个水合物平衡级分离;体积分数大于30%时为两个水合物平衡级分离。温度对水合分离的反应压力有较大影响,但对所需平衡级分离级数的影响并不大。随着温度的升高,水合反应压力呈增加趋势,增加幅度随进料干基CO₂体积分数的增加而降低。针对所研究气样,在不同温度下,均需三个水合物平衡级分离才能达到工艺要求。