CO2气提法尿素工艺技术的改进

黑龙江化工总厂日产８７０ｔ尿素装置采用荷兰斯塔米卡邦公司的ＣＯ２气提法生产工艺,由该公司提供工艺软件包,由中国五环化学工程公司承担基础工程设计,国内配套生产关键设备,仪表国外采购,生产过程采用ＤＣＳ控制。本装置在工艺路线、设备结构、原始开车技术方面与８０年代引进的１４套ＣＯ２气提法尿素装置有一定区别,尤其在原始开车技术、合成塔塔板上有较大改进。本文就该装置的工艺技术改进作简单介绍。１　工艺技术改进１１　用常温精脱硫催化剂脱除ＣＯ２气体中硫化物进尿素区ＣＯ２原料气最大气量１６０００ｍ３／ｈ,原料…     

气体膜分离技术在我厂合成氨生产中的应用

一、气体膜分离技术简介 气体膜分离技术是利用气体对气膜渗透能力的差异来分离气体的一种技术工程。气膜分离过程是:气体从气流主体扩散到气膜表面,被气膜选择吸附,借薄膜两端的总压差给气体的渗透提供推动力,使气体渗透过气膜并从气膜的另一侧面脱附进入渗透气的主气流中。 气膜分离技术自1979年在美国工业化以来,由气体分离膜组成的渗透器可设计成多种适合于气体分离的形式,如板式膜、管式膜、中空纤维膜等。目前,已从分离回收合成氨厂驰放气中的氢,发展到从甲醇尾气中     

半透膜气体精制法

<正> ENSTAR Engineering Co采用DE SEP半透膜分离法脱除天然气、炼厂气等轻质烃类蒸汽中的硫化氢及二氧化碳。过程采用纤维素半透膜。气体经分离后,残留气体和透过气体组分可以达到规定的产品标准。高压原料气首先在过滤分离器中除去液体和固体杂质后,在加压下进入半透膜分离器。在膜分离器中,透过性强的硫化氢和二     

二氧化碳驱油返回气提质利用方案比选

为了更好地利用井口返回气中的二氧化碳和烃类,针对某油田二氧化碳驱油返回气的气源特征,结合油井装置现场实际情况,对二氧化碳和烃的分离及提质利用进行了研究,提出了2种二氧化碳驱油返回气的提质利用方案,对比了工艺脱水效果及膜分离效果,分析了应重点解决的问题。结果表明,直接对返回气进行压缩、预冷、干燥、脱水后再进行膜分离脱碳是较经济可行的方案,利用级间抽出气体的位能和减压冷量不足以弥补气体循环带来的压缩功耗。     

膜分离技术在回收炼厂气中氢气的应用

介绍了膜分离技术在中石化上海高桥分公司回收炼厂气中氢气的应用。重点介绍了气体膜分离的原理,工艺流程以及标定情况。针对生产运行中出现的问题做了分析,并提出处理措施。通过对生产过程的优化调整,提高了炼厂氢气资源的利用效率和经济效益。     

基于称量法制备标准气体配气装置的研制与应用

介绍了称量法制备标准气体的原理、方法和制备过程中需要考虑的因素,并在此基础上研制了一种基于称量法制备标准气体的配气装置。用气相色谱仪对用该新型装置配制的标准气体进行压力均匀性和稳定性考察,其定值及不确定度均符合要求,该装置能提高配气效率达30%以上。     

合成氨装置ATR/KRES水碳比优化控制系统

使用天然气作原料的合成氨装置气体转化系统,蒸气与原料气的投用比例,通过仪表控制系统经过精确计算,实现复杂控制,达到优化节能的目的。     

NHD脱碳气中CO2含量超标的解决措施

晋煤天源化工有限公司(以下简称天源公司)脱碳装置采用NHD脱碳工艺,该装置运行5年以来十分稳定,但近期也暴露出脱碳气中CO2含量超标等问题。1工艺流程1.1工艺气流程来自变换气脱硫装置的变脱气首先进入气体换热器,与净化气以及CO2产品气换热,再经原料气分离器进入脱碳塔,气体由下而上与塔顶喷     

浅谈上吹加氮制气节能降耗

0 前言 合成氨半水煤气生产过程中，上吹加氮工艺已经应用多年，但是由于炉径的扩大及气化强度的增加，原煤气管道、阀门、设备等不能及时改造，使原来的上吹加氮装置与其当前的生产不能完全适应。恒立化工公司原上吹加氮装置已拆除多年，近年来不断对造气系统进行改造，原料煤消耗不断下降，根据优化气体质量、降低原料煤耗的设想，正在进行改进和安装该加氮装置。使用结果表明，采用该装置对完善调节手段及合理控制，充分利用装置节能降耗，提高运行具有重要的意义。现就该装置对系统稳定，降低煤耗的体会进行分析，供大家参考。     

逆流等温-绝热烯烃饱和技术在制氢原料精制中的应用

介绍逆流等温-绝热加氢工艺流程在高烯烃含量的炼厂气用作制氢装置原料时,有效控制原料烯烃饱和过程中加氢反应器催化剂床层的温度的原理以及该工艺在中石油辽河石化焦化富气制氢中的使用情况,结果表明,该工艺解决了烯烃加氢饱和过程中的放热取出问题,实现了焦化富气用作制氢原料,拓宽了制氢原料来源.     

Understanding the performance of membrane for direct air capture of CO2

Direct air capture (DAC) of CO₂ is becoming increasingly important for reducing greenhouse gas concentrations in the atmosphere. However, the cost and energy requirements associated with DAC make it less economically feasible than carbon capture from flue gases. While various methods like solid sorbents and gas–liquid absorption have been explored for DAC, membrane processes have only recently been investigated. The objective of this study is to examine the separation performance of a membrane unit for capturing CO₂ from ambient air. The performance of a membrane depends on several factors, including the composition of the feed gas, pressure ratio, material selectivity, and membrane area. The single-stage separation process with the co-current flow and constant permeability flux model is evaluated using a commercial module integrated with a process simulator to separate a binary mixture of carbon dioxide and nitrogen to assess the sensitivity of selectivity on purity and recovery of CO₂ in permeate, and power requirement. Additionally, three levels of CO₂ reduction from the feed stream to the retentate stream (25%, 50%, and 75%) are studied. A trade-off between purity and recovery factor is observed, and achieving high purity in permeate requires high concentration in the retentate.     

生物甲烷膜分离提纯系统的设计与优化

以厌氧发酵生物气为原料生产压缩天然气是大规模利用生物质资源的重要途径。首先,在过程模拟软件UniSim Design中基于有限元方法建立了中空纤维膜的离散数值计算模型,适合于模拟渗透切割比非常高的生物甲烷膜分离过程。以单级聚酰亚胺膜分离系统为例研究了关键操作条件--膜的进料压力对处理能力、甲烷收率及压缩天然气生产单耗的影响。目前的评估体系下,提高进料压力有利于提高处理能力和甲烷回收率,而压缩天然气生产单耗在2.70 MPa时最低,为0.46 kW·h·m^-3压缩天然气。通过分析渗透气的甲烷浓度变化趋势,开发了一级二段气体膜分离系统,兼具流程简单、设备投资低、甲烷收率高、产值高的优点。以处理1000 m³·h^-1生物气为例,甲烷收率达95.0%,压缩天然气产量500 m³·h^-1。对应地,装置总投资为3.8×10⁶ CNY,年运行费用及设备折旧为1.5×10⁶ CNY,年经济效益（毛利）超过2.50×10⁶ CNY。     

Membrane/cryogenic hybrid scheme for argon production from air

A novel membrane/cryogenic hybrid scheme is presented wherein crude argon from a cryogenic air separation unit is fed to an oxygen selective membrane unit to remove a substantial portion of the oxygen. The oxygen enriched permeate from the membrane unit is returned to the crude argon distillation column of the cryogenic air separation process. The non-permeate stream is enriched in argon and can be further purified in a catalytic unit to produce an oxygen-free argon stream. The proposed process makes use of the synergy between the two separation units whereby, the cryogenic unit offers high recovery and the membrane provides purification leading to improved argon recoveries at higher argon concentrations. Calculations show that this process, in conjunction with an oxygen removal catalytic process, provides an economical alternative for the production of pure argon as compared to the conventional process using just a cryogenic unit and a catalytic unit to remove oxygen.     

Separation of Phenol from Aqueous Streams by a Composite Hollow Fiber Based Pervaporation Process Using Polydimethyl siloxane (PDMS)/Polyether-Block-Amide (PEBA) as Two-Layer Membranes

Abstract

In order to simultaneously achieve both high permselectivity and permeability (flux) for the recovery of aromatic compounds such as phenol from aqueous streams, a composite organophilic hollow fiber based pervaporation process using PDMS/PEBA as two-layer membranes has been developed. The process employed a hydrophobic microporous polypropylene hollow fiber, having thin layers of silicones (PDMS) and PEBA polymers coating on the inside diameter. The composite membrane module is used to investigate the pervaporation behavior of phenol in water in a separate study; and that of a mixture of phenol, methanol, and formaldehyde in an aqueous stream (a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process) in another study. The fluxes of phenol and water increase relatively linearly with increasing concentration especially at low feed concentration, and exhibit a near plateau with further increase in concentration. As a result, the phenol/water separation factor decreases as the feed concentration increases. Significant improvement in phenol/water separation factor and phenol flux is achieved for this two-layer (PDMS/PEBA) membranes as compared to that achieved using only PDMS membrane. The phenol and water fluxes and the separation factor are highly sensitive to permeate pressure as all decrease sharply with increase in permeate pressure. For this membrane, an increase in temperature increases the separation factor, and also permeation fluxes of phenol and water. An increase in feed-solution velocity does not have a significant effect on phenol and water fluxes, and also on the separation factor at least within the range of the feed-solution velocity considered. In the study of pervaporation behavior of a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process, phenol permeation shows a much higher flux and a higher increase in flux with increase in concentration is also exhibited as compared to that exhibited by methanol permeation. This thus indicates that the membrane is more permeable to phenol than to methanol and formaldehyde.     

Cyclic Operation of Forced Flow Electrokinetic Separation for Simultaneous Separation and Concentration of Charged Molecules

Abstract

A new cyclic operation of membrane separation in the presence of an electric field is developed. The microporous membrane/filter acts as a barrier between two adjacent solutions (i.e., the solution in the membrane cell and in the permeate). An electric field is applied across the membrane to induce electromigration of charged molecules whose molecular weights are much smaller than the molecular weight cutoff of the membrane used. The charged molecules move freely through pores of the membrane without hindrance. In the presence of an electric field, the concentration of charged molecules in the permeate stream is determined by the electromigration velocity and the permeation flow rate through the membrane. The permeation rate is controlled by the applied pressure drop, and the electro-migration velocity can be controlled by the electric field strength applied. By applying a high electric field and a low pressure drop, the concentration in the permeate stream can be increased, thus resulting in enrichment of the charged molecules in the permeate. By applying an electric field such that the electromigration is in the opposite direction to the permeation flow, the permeate is depleted of the charged molecules. A continuously supplied feed stream to the membrane cell can be processed into a concentrated solution and a depleted solution by alternating the polarity of an electric field. This paper presents the experimental results of a cyclic operation for the simultaneous separation/recovery and concentration of acetate, phenylalanine, glycine, and aspartic acid.     

Modelling of multicomponent gas separation with asymmetric hollow fibre membranes—methane enrichment from biogas

A mathematical model for the dynamic performance of gas separation with high flux, asymmetric hollow fibre membranes was developed considering the permeate pressure build‐up inside the fibre bore and cross flow pattern with respect to the membrane skin. The solution technique provides reliable examination of pressure and concentration profiles along the permeator length (both residue/permeate streams) with minimal effort. The proposed simulation model and scheme were validated with experimental data of gas separation from literature. The model and solution technique were applied to investigate dynamic performance of several membrane module configurations for methane recovery from biogas (landfill gas or digester gas), considering biogas as a mixture of CO₂, N₂ and CH₄. Recycle ratio plays a crucial role, and optimum recycle ratio vital for the retentate recycle to permeate and permeate recycle to feed operation was found. From the concept of two recycle operations, complexities involved in the design and operation of continuous membrane column were simplified. Membrane permselectivity required for a targeted separation to produce pipeline quality natural gas by methane‐selective or nitrogen‐selective membranes was calculated. © 2012 Canadian Society for Chemical Engineering     

Experimental validation of hybrid distillation‐vapor permeation process for energy efficient ethanol–water separation

BACKGROUND: The energy demand of distillation‐based systems for ethanol recovery and dehydration can be significant, particularly for dilute solutions. An alternative separation process integrating vapor stripping with a vapor compression step and a vapor permeation membrane separation step, termed membrane assisted vapor stripping (MAVS), has been proposed. The hydrophilic membrane separates the ethanol–water vapor into water‐rich permeate and ethanol‐enriched retentate vapor streams from which latent and sensible heat can be recovered. The objective of this work was to demonstrate experimentally the performance of a MAVS system and to compare the observed performance with chemical process simulation results using a 5 wt% ethanol aqueous feed stream as the benchmark. RESULTS: Performance of the steam stripping column alone was consistent with chemical process simulations of a stripping tower with six stages of vapor liquid equilibria (VLE). The overhead vapor from the stripper contained about 40 wt% ethanol and required 6.0 MJ of fuel‐equivalent energy per kg of ethanol recovered in the concentrate. Introduction of the vapor compressor and membrane separation unit and recovery of heat from both membrane permeate and retentate streams resulted in a retentate ethanol concentrate containing ca 80 wt% ethanol, but requiring only 2.2 MJ fuel kg^?1 ethanol, significantly less than steam stripping alone. CONCLUSION: Performance of the experimental unit with a 5 wt% ethanol feed liquid corroborated chemical process simulation predictions for the energy requirement of the MAVS system, demonstrating a 63% reduction in the fuel‐equivalent energy requirement for MAVS compared with conventional steam stripping or distillation. Published 2009 by John Wiley & Sons, Ltd.     

Steady State Permeate Flux Estimation in Cross-Flow Ultrafiltration of Protein Solution

In the membrane separation process, the cross-flow configuration in which the fluid flows parallel to the membrane is widely utilized. Due to the shear stress exerted by the tangential feed flow, the accumulation of the retained species in the membrane is reduced, and the nearly steady state operation can be attained. The determination of steady state permeate flux is significant in the design and optimization problem. Several mechanisms of transport phenomena have been proposed to estimate the steady state permeate flux such as concentration polarization and Brownian diffusion, shear-induced diffusion, inertial lift, and surface transport. Another approach is using dimensional analysis to give the correlation equation with the operating condition instead of a deep focus on mechanism. In this study, we apply the model proposed in our previous study to predict the steady state permeate flux from the experimental data. After that, a new method using dimensional analysis is also developed to predict the steady state permeate flux from the operating conditions such as the trans-membrane pressure, the feed flow rate, and the feed volume fraction in a wide range. The correlation equation provides a good estimation of the experimental results.     

Improving membrane performance for nitrogen production from air

Using a portion of the product N₂ to purge the permeate side of a membrane module in order to reduce the membrane area for the separation of air for nitrogen production is considered. A simulation program was developed and used to compare a purge system to a conventional non-purge permeator. Both the selectivity of the membrane and the feed/permeate pressure ratio were found to affect the ability of the purge stream to reduce the membrane area. The purge stream reduces the recovery of nitrogen, which results in a minimum in the membrane area per unit of product flow.     

Pervaporation of flavors with hydrophobic membrane

Using a pervaporation process, a surface-modified hydrophobic membrane was used for recovery of esters which are volatile organic flavor compounds; ethyl acetate (EA), propyl acetate (PA), and butyl acetate (BA). A surface-modified tube-type membrane was used to evaluate the effects of the feed concentration (0.15–0.60 wt%) and feed temperature (30–50 °C) on the separation of EA, PA, and BA from dilute aqueous solutions. The permeation flux increased with the increasing feed ester concentration and operating temperature. EA, PA, and BA in the permeate were concentrated up to 9.13–32.26, 11.44–34.95, and 14.96–36.37 wt%, respectively. The enrichment factors for the 0.15–0.60 wt% feed solution of EA and BA were in the range of 48.5-62.8 and 97.7-101.5, respectively. Phase separation occurred in the permeate stream because the ester concentration in the permeate was above the saturation limit. This meant that selectivity of the membrane was high enough for the recovery of esters from dilute aqueous solution, even though the enrichment factor of the membrane was lower than that of non-porous PDMS membrane. The fluxes of EA, PA, and BA at 0.60 wt% (6,000 ppm) feed concentration and 40 °C were 254, 296, and 318 g/m².hr, which are much higher than those obtained with polymer membranes. In the case of non-porous PDMS at feed concentrations of 90-4,800 ppm and at 45 °C, it was reported that the permeate flux of EA was 1.1–5.8 g/m^2.h. Compared to non-porous PDMS, the surface-modified membrane investigated in this study showed a much higher flux and enough selectivity of esters.