PSA-H_2装置分子筛粉化原因分析及解决措施

分析变压吸附制氢装置运行过程中分子筛粉化的原因,提出解决措施与改进建议。     

PSA变压吸附分子筛粉倾原因分析

我公司甲醇车间采用合成氨弛放气中的氢气作原料。 1 987年甲醇装置投产时制氢采用的是西南院 PSA所的四塔一均 PSA工艺 ,两套处理量为 3 0 0 0 m3 /h。 1 993年根据实际生产的需要 ,由西南化工研究院变压吸附研究所设计改造成了处理量为 70 0 0 m3 /h的八塔三均工艺 (也可切换成A、 B两个处理量为 3 5 0 0 m3 /h的四塔二均单系列操作 )。同时八个吸附塔内的吸附剂也由青岛的球状 5 分子筛全部更换成上海环球联碳 (UOP)分子筛公司的条状分子筛。但是 PSA在 1 993年 1 1月改造完仅仅投运了一个多月分子筛就出现大量粉化现象 ,我们随即…     

合成氨装置低温液氮洗瓶颈原因分析及解决措施

介绍了液氮洗工艺流程,叙述了液氮洗装置存在的问题,分析了液氮洗装置存在问题的原因和解决措施。结果表明,通过操作优化、塔体垂直度校正以及氮洗塔塔板盘检查检修后,装置日产量从原来的442t增加到508.71t,效果显著。     

PSA变压吸附制氢吸附剂分子筛粉化原因分析

介绍了变压吸附制氢工艺特点和分子筛粉化后的主要现象,并对引起分子筛粉化的5个因素进行了分析和讨论。     

精炼气中微量不饱和烃对微量CO,CO2控制监测影响的探讨

本文叙述了合成氨厂精炼气中微量不饱和烃的存在,会导致铜洗微量CO分析虚高。试验用加有NaCl和NaBr的饱和溴水吸收液,成功地除去了原料气中的不饱和烃,从而消除了微量CO虚高的现象。     

我厂合成氨铜洗再生系统存在问题的分析及改造

我厂合成氨车间铜洗再生系统于1994年8月5日因全厂设备大修转入年度停车,整个系统于9月16日开车时开不起来,严重影响全厂的正常开车生产。主要表现为再生塔液位满,降不下来,再生熟化器压力高达24.5kPa,残余二氧化碳升高微量难以合格,最严重时,熟化器液位抽空,Cu~(2+)急剧下降,根本不能坚持生产,所以切气停车。     

铜液变稀的原因及处理措施

我厂自１９９２年联醇投产以来,出现了几次铜液变稀、贮桶盛满,其中一次总铜由２．０ｍｏｌ／Ｌ降到１．２６ｍｏｌ／Ｌ,严重影响了精炼操作,给氨系统生产带来困难。经探讨,我们找到了铜液变稀的原因,采取了相应措施,对铜液提浓也摸索出一些方法,供同行参考。１铜...     

PSA-H2装置分子筛粉化原因分析及解决措施

我公司甲醇装置是利用100kt合成氨铜洗气中的CO、CO2和300kt合成氨弛放气中的H2作原料气来生产的,氢提纯采用的是变压吸附工艺。为了满足油脂化工所需高纯度氢气的要求,进一步提高弛放气中氢的回收率,1993年底对原有的变压吸附装置进行了节能技术改造,即由原来的二套四塔一均工艺改为目前的八塔三均工艺。改造后投运不久,就发现分子筛粉化现象严重,后经分析及处理,解决了分子筛粉化问题。1　粉化情况变压吸附装置改造投用后,仅运行了20多天,就发现部分吸附塔的仪表导压管有被分子筛粉尘堵塞的现象。起初仪表工均一一取下进行疏通,随着装置…     

K_2CO_3活化制备淀粉基碳分子筛

以可溶性淀粉为碳源、三嵌段共聚物F127为模板剂和K_2CO_3为活化剂,采用一步合成法制备系列淀粉基碳分子筛。通过扫描电子显微镜和N_2吸附-脱附分析淀粉基碳分子筛孔隙形貌和孔结构,采用热重-TG和傅里叶红外光谱表征原料和样品的物质结构官能团。结果表明,K_2CO_3浓度、F127添加比例、反应时间和反应温度影响淀粉基碳分子筛的孔隙结构。在炭化温度800℃、K_2CO_3浓度为0.50 mol·L~(-1)、F127与淀粉质量比=1∶3、反应温度50℃和反应时间12 h条件下制备的淀粉基碳分子筛,孔径集中于0.63 nm,比表面积为1 069.290 4 m~2·g~(-1),单点孔容0.667 901 cm~3·g~(-1)。     

Separation of CO2/CH4 through carbon molecular sieve membranes derived from P84 polyimide

The separation of CO₂/CH₄ separation is industrially important especially for natural gas processing. In the past decades, polymeric membranes separation technology has been widely adopted for CO₂/CH₄ separation. However, polymeric membranes are suffering from plasticization by condensable CO₂ molecules. Thus, carbon molecular sieve membranes (CMSMs) with excellent separation performance and stability appear to be a promising candidate for CO₂/CH₄ separation. A commercially available polyimide, P84 has been chosen as a precursor in preparing carbon membranes for this study. P84 displays a very high selectivity among the polyimides. The carbonization process was carried out at 550–800 °C under vacuum environment. WAXD and density measurements were performed to characterize the morphology of carbon membranes. The permeation properties of single and equimolar binary gas mixture through carbon membranes were measured and analyzed. The highest selectivity was attained by carbon membranes pyrolyzed at 800 °C, where the pyrolysis temperatures significantly affected the permeation properties of carbon membranes. A comparison of permeation properties among carbon membranes derived from four commercially available polyimides showed that the P84 carbon membranes exhibited the highest separation efficiency for CO₂/CH₄ separation. The pure gas measurement underestimated the separation efficiency of carbon membranes, due to the restricted diffusion of non-adsorbable gas by adsorbable component in binary mixture.     

Effect of SiO2/Al2O3 ratio on the conversion of methanol to olefins over molecular sieve catalysts

A series of SAPO-34 molecular sieves with different SiO₂/Al₂O₃ ratios have been synthesized for the methanol-to-olefin (MTO) reaction. Their physico-chemical properties are characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and N₂ adsorption-desorption. The results are compared with those of the commercial HZSM-5, which show that the crystallinity and particle diameter of SAPO-34 as well as HZSM-5 increase with SiO₂/Al₂O₃ ratio. The variation of BET surface area of SAPO-34 is different from that of HZSM-5 and the sample with SiO₂/Al₂O₃ ratio of 0.4 exhibits the highest BET surface area. FT-IR spectra indicate that HZSM-5 has both Br?nsted and Lewis acid sites and Br?nsted acid sites are stronger, whereas SAPO-34 samples are dominated only by Lewis acid sites. When the SiO₂/Al₂O₃ ratio increases, propylene and butylenes become the predominant product of the MTO reaction over HZSM-5. In contrast, the main products of this reaction catalyzed by SAPO-34 are ethylene and propylene. According to the product distribution, the reaction mechanism over HZSM-5 catalysts is proposed.     

Surface sol–gel modification of mesoporous silica molecular sieve SBA-15 with TiO2 in supercritical CO2

Mesoporous silica molecular sieve SBA-15 has been grafted with monolayer and doublelayer of titanium dioxide via surface sol–gel process in supercritical carbon dioxide (SC CO₂). The materials were characterized by nitrogen adsorption, X-ray photoelectron, X-ray diffraction (XRD), and Raman spectroscopy. The results suggest that the incorporated titanium dioxide is present mainly as anatase phase. The pore diameter decreases with the modification cycle number, and the titanium dioxide exists as a 5 Å thick film chemically anchored on the mesopores of SBA-15.     

CuBr2修饰MgB2粉体及其超导性研究

通过研磨、超声的方法制备了MgB2超细粉体,并用CuBr2对该MgB2粉体进行表面修饰。研究发现,经过CuBr2修饰的MgB2,其超导转变温度Tc高于未修饰的MgB2粉体。可能原因是Cu2＋与B-离子配位后,增强了MgB2的电声耦合强度,并提高了MgB2的空穴载流子浓度。     

CO2 separation by carbon molecular sieve monoliths prepared from nitrated coal tar pitch

The objective of the present work is to develop a simple procedure, which avoids the need of a binder, to obtain activated carbon monoliths from a waste precursor (coal tar pitch) suitable for CO₂ capture and/or separation. The main task of this process consists of a nitration process of the coal tar pitch. This nitration step over the coal tar pitch is characterised by different techniques, such as infrared spectroscopy and thermogravimetric analysis. The nitration treatment produces the oxidation of the pitch molecules, leading to hydrogen consumption and generating oxygenated and nitrogenated surface complexes. As a consequence of this oxidation, nitrated coal tar pitch is an infusible material, which allows the carbonization of monolithic pieces avoiding their fusion. Decomposition of these surface complexes during the carbonization of monoliths generates narrow microporosity, which is suitable for CO₂ capture from gas streams at room temperature. The molecular sieving properties of these materials are studied by CH₄ and CO₂ adsorption kinetics.     

Synthesis of single-phase Ti3SiC2 powder

In this study, free 2Ti/2Si/3TiC powder mixture was heated at high temperatures in vacuum, in order to reveal the possibility for the synthesis of high Ti₃SiC₂ content powder. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the evaluation of phase identities and the morphology of the powder after different treatments. Results showed that almost single phase Ti₃SiC₂ powder (99.3 wt.%) can be synthesized by heat treatment with free 2Ti/2Si/3TiC powders in vacuum at 1210°C for about 3 h. The nucleation and growth of Ti₃SiC₂ within TiC particles was observed. The typical appearance of the formed Ti₃SiC₂ is equiaxed with particle size of 2–4 μm. Effects of temperature and heating time on the morphology and the particle sizes of the synthesized Ti₃SiC₂ powders are not obvious.     

New acrylic monolithic carbon molecular sieves for O2/N2 and CO2/CH4 separations

The modification of activated carbon fibres prepared from a commercial textile acrylic fibre into materials with monolithic shape using phenolic resin as binder was studied. The molecular sieving properties for the gas separations CO₂/CH₄ and O₂/N₂ were evaluated from the gas uptake volume and selectivity at 100 s contact time taken from the kinetic adsorption curves of the individual gases. The pseudo-first order rate constant was also determined by the application of the LDF model. The samples produced show high CO₂ and O₂ rates of adsorption, in the range 3-35 × 10⁻³ s⁻¹, and in most cases null or very low adsorption of CH₄ and N₂ which make them very promising samples to use in PSA systems, or similar. Although the selectivity was very high, the adsorption capacity was low in certain cases. However, the gas uptake in two samples reached 23 cm³ g⁻¹ for CO₂ and 5 cm³ g⁻¹ for O₂, which can be considered very good. The materials were heat-treated using a microwave furnace, which is a novel and more economic method, when compared with conventional furnaces, to improve the molecular sieves properties.     

Preparation and characterization of Ti3SiC2 powder

Pressureless sintering in vacuum was applied to synthesize Ti₃SiC₂ from elemental powders of Ti, Si and C. Based on the phase compositions and purities of the products obtained by X-ray diffraction, the elemental powders composition and sintering condition were optimized. It was found that the sample sintered at 1450 °C for 240 min from a mixture of 3Ti/1.75Si/2C (molar ratio) contained Ti₃SiC₂ with the volume fraction as high as 93%. It was proposed that loss of Si through gaseous vaporization and contamination of C might be the main obstacles against obtaining high-purity material by this way.