Воздействие высокой концентрации оксида азота на оксигенаторы аппаратов искусственного кровообращения (экспериментальное исследование)

The aim of the study. To study the effect of high nitric oxide concentrations on hollow polypropylene fibers of oxygenators.Materials and methods. The study was conducted in two stages. At the first stage, we evaluated the stability of oxygenator membrane made of hollow polypropylene fibers after six hours of exposure to air-oxygen mixture containing NO at 500 parts per million, or 500 pro pro mille (ppm) concentration, using mass spectrometry and infrared spectroscopy. At the second stage, an experiment with cardiopulmonary bypass (CPB) was conducted on 10 pigs. In the study group (n=5) animals sweep gas was supplied to the oxygenator as an air-oxygen mixture with NO at 100 ppm. In the control group animals (n=5) an air-oxygen mixture was used without NO. The CPB lasted for 4 hours, followed by observation for 12 hours. NO, NO2 (at the inlet and outlet of the oxygenator), and the dynamics of methemoglobin were evaluated. After weaning of animals from CPB, the oxygenators were tested for leakproofness, and scanning electron microscopy (SEM) was performed.Results. The oxygenator made of polypropylene hollow fibers retained its gas transfer parameters after six hours of exposure to air-oxygen mixture containing NO at 500 ppm. Based on IR-Fourier spectroscopy findings, NO did not affect structural integrity of polypropylene membranes. NO added to gas mixture at 100 ppm did not increase NO2 to toxic level of 2 ppm in 91% of control tests during 4 hours CPB in pigs; mean value was 1.58 ± 0.28 ppm. Methemoglobin concentration did not exceed the upper limit of permissible level (3%), and there were no statistically significant differences with the control group. All tested oxygenators have passed the leakproofness test. According to SEM findings, larger amounts of fibrin deposits were found in the control group oxygenators vs study group.Conclusion. There were no negative effects of NO at 500 ppm concentration on the oxygenator membrane made of hollow polypropylene fibers. NO at 100 ppm in a gas-mixture supplied to oxygenators did not lead to an exceedance of safe NO2 and methemoglobin concentrations in an animal model. Reduced fibrin deposits on hollow fibers of polypropylene oxygenator membranes were observed when with NO at a level of 100 ppm was added to a gas mixture.  Цель исследования. Изучить воздействие высоких концентраций оксида азота на полипропиленовые полые волокна оксигенаторов.Материалы и методы. Исследование провели в два этапа. На первом этапе с помощью масс-спектрометрии и инфракрасной спектроскопии выполнили оценку стабильности мембраны оксигенатора из полых волокон полипропилена после шестичасового воздействия воздушно-кислородной смеси, содержащей NO в концентрации 500 пропромилле, или 500 частей на миллион – parts per million (ppm). На втором этапе провели эксперимент на 10 свиньях с подключением аппарата искусственного кровообращения (ИК). Животным основной группы (n=5) в оксигенатор подавали воздушно-кислородную смесь, содержащую NO в концентрации 100 ppm. Животным контрольной группы (n=5) в оксигенатор подавали воздушно-кислородную смесь без NO. Процедура ИК длилась 4 часа, затем следовало наблюдение в течение 12 часов. Оценивали NO, NO2 (на входе и выходе из оксигенатора), динамику метгемоглобина. После отключения от ИК оксигенаторы тестировали на герметичность, а также выполняли сканирующую электронную микроскопию (СЭМ).Результаты. Оксигенатор из полипропиленовых полых волокон сохранял свои газотранспортные характеристики после шестичасового воздействия воздушно-кислородной смеси с добавлением NO в концентрации 500 ppm. По данным ИК-Фурье спектроскопии показали, что NO не влияет на структуру мембран из полипропилена. Добавление NO в дозировке 100 ppm во время 4 часов ИК у свиней не сопровождалось повышением концентрации NO2 до токсичного уровня 2 ppm в 91% измерений: среднее значение составило 1,58 ± 0,28 ppm. Концентрация метгемоглобина не превышала верхнего  предела  допустимых  значений  (3%),  не  обнаружили  каких-либо статистически значимых различий при сравнении с группой контроля. Все исследуемые оксигенаторы выдержали тестирование на герметичность. По результатам СЭМ оксигенаторы группы контроля характеризовались большим количеством отложений фибрина, чем оксигенаторы основной группы.Заключение. Негативного воздействия NO в концентрации 500 ppm на мембраны оксигенаторов из полых волокон полипропилена не обнаружили. Подача в оксигенатор NO в концентрации 100 ppm NO2 не приводила к превышению безопасного содержания NO2 и метгемоглобина в эксперименте на животных. Выявили снижение образования отложений фибрина на полых волокнах мембран оксигенаторов из полипропилена при подаче NO в концентрации 100 ppm

Membrane Cascade Type of «Continuous Membrane Column» for Power Plant Post-Combustion Carbon Dioxide Capture Part 1: Simulation of the Binary Gas Mixture Separation

The present paper deals with the complex study of CO2 capture from combined heat power plant flue gases using the efficient technological design of a membrane cascade type of «Continuous Membrane Column» for binary gas mixture separation. In contrast to well-known multi-step or multi-stage process designs, the cascade type of separation unit provides several advantages. Here, the separation process is implemented in it by creating two counter current flows. In one of them is depleted by the high-permeable component in a continuous mode, meanwhile the other one is enriched. Taking into account that the circulating flows rate overcomes the withdrawn one, there is a multiplicative increase in separation efficiency. A comprehensive study of CO2 capture using the membrane cascade type of «Continuous Membrane Column» includes the determination of the optimal membrane material characteristics, the sensitivity study of the process, and a feasibility evaluation. It was clearly demonstrated that the proposed process achieves efficient CO2 capture, which meets the modern requirements in terms of the CO2 content (≥95 mol.%), recovery rate (≥90%), and residual CO2 concentration (≤2 mol.%). Moreover, it was observed that it is possible to process CO2 with a purity of up to 99.8 mol.% at the same recovery rate. This enables the use of this specific process design in CO2 pretreatment operations for the production of high-purity carbon dioxide

Synthesis and Study of Gas Transport Properties of Polymers Based on Macroinitiators and 2,4-Toluene Diisocyanate

Nowadays, block copolymers hold great promise for the design of novel membranes to be applied for the membrane gas separation. In this regard, microporous block copolymers based on a macroinitiator with an anionic nature, such as potassium-substituted block copolymers of propylene oxide and ethylene oxide (PPEG) and 2,4-toluene diisocyanate (TDI), were obtained and investigated as effective gas separation membranes. The key element of the macromolecular structure that determines the supramolecular organization of the studied polymers is the coplanar blocks of polyisocyanates with an acetal nature (O-polyisocyanate). In the present research, the influence of the content of peripheral polyoxyethylene (POE) blocks in PPEG on the supramolecular structure processes and gas transport characteristics of the obtained polymers based on PPEG and TDI was investigated. According to the study of polymers if the POE block content is 15 wt %, the polyoxypropylene segments are located in the internal cavity of voids formed by O-polyisocyanate blocks. When the POE block content is 30 wt %, the flexible chain component forms its own microphase outside the segregation zone of the rigid O-polyisocyanate blocks. The permeability for polar molecules, such as ammonia or hydrogen sulfide, significantly exceeds the permeability values obtained for non-polar molecules He, N2 and CH4. A relatively high permeability is also observed for carbon dioxide. At the same time, the content of POE blocks has a small effect on the permeability for all studied gases. The diffusion coefficient increases with an increase in the POE block content in PPEG for all studied gases

An Efficient Technique for Ammonia Capture in the Haber–Bosch Process Loop—Membrane-Assisted Gas Absorption

The present study continues the development and enhancement of a highly efficient unique hybrid technique—membrane-assisted gas absorption in designing the separation unit, which provides the improvement in mass-transfer of a target component during the ammonia capture process from a process loop of the Haber–Bosch technological route. In order to minimize the absorbent volume to membrane area ratio, the special separation cell was designed based on a combination of two types of hollow fiber membranes, dense gas separation membrane and porous pervaporation membrane. The separation performance tests were implemented under two sets of conditions, sweeping the bore (permeate) side of a cell with helium and hydrogen-nitrogen mix. For both cases, the membrane-assisted gas absorption cell demonstrated high separation efficiency, and the ammonia concentration in the permeate was never lower than 81 mol%; meanwhile, under the hydrogen-nitrogen bore sweep conditions, the ammonia concentration in the permeate reached 97.5 mol% in a single-step process. Nevertheless, there is a product purity–recovery rate trade-off, which is a typical issue for separation processes

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S

The Cation Effect on the Free Volume and the Solubility of H₂S and CO₂ in Ionic Liquids Based on Bis(2-Ethylhexyl) Sulfosuccinate Anion

Herein, we report for the first time a study dedicated to acidic gases’ solubility in ionic liquids with sterically hindered bulky anion, namely bis(2-ethylhexyl) sulfosuccinate ([doc]), experimentally evaluated at low pressures. The effect of cation change (imidazolium, pyridinium, and pyrrolidinium) on the thermophysical properties and sorption capacities was also discussed. The densities and the activation energies of the tested ILs exhibited minor differences. Furthermore, the COSMO-RS model was used to predict the free volumes of ILs aiming to investigate its influence on gas solubilities. The conducted calculations have revealed an antibate correlation between the fractional free volume (FFV) and Henry’s law constant. In particular, the lowest FFV in 1-methylimidazolium [doc] corresponded to the minimal sorption and vice versa. In addition, it was shown that the presence of protic cation results in a significant reduction in CO2 and H2S solubilities. In general, the solubility measurement results of the synthesized ILs have shown their superiority compared to fluorinated ILs based on the physical absorption mechanism

Hydrate-based technique for natural gas processing: Experimental study of pressure-dropping and continuous modes

Gas hydrate crystallization is perspective and energy-efficient technology for gas mixtures processing, including natural gas. There were compared pressure-dropping and continuous gas hydrate crystallization methods for separation of gas mixture closed to natural gas. The studied mixture has been chosen similar to the natural gas composition: CH4 (75.68 mol.%) - С2H6 (7.41 mol.%) - C3H8 (4.53 mol.%) - н-C4H10 (2.47 mol.%) - CO2 (5.40 mol.%) - H2S (1.39 mol.%) - N2 (3.01 mol.%) - Xe (0.11 mol.%). Experiments were provided in the 4 L high pressure reactor, using water solution of SDS (0.20 wt.%). The experiment conditions were 280.15 K and pressure of 4.25 MPa. The components separation factors and recovery for two modes have been researched and compared for choosing more effective options. After comparing these characteristics, it was concluded that continuous process is more productive than pressure-dropping mode. At the stage cut (θ) of 0.9, the gas components total recovery (R) for the continuous mode have exceeded the total recovery for the pressure-dropping mode by 8.15 %, and at θ = 0.8, exceeded by 6.11 %. The recovery and separation factors have the highest values for H2S, C3H8, Xe in the continuous mode: 97.62 %, 94.90 %, 84.98 % and 8.7, 10.53, 6.36, respectively. Thus, the choosing of the more effective stage cut depends on the aim of the process: the highest purity or the largest recovery