INTEGRATED REFRIGERATION AND PRESSURE-CONTROLLED PURIFICATION METHOD FOR OBTAINING HIGH-PURITY DINITROGEN TETHROXIDE (NTO) FROM AQUEOUS NOX GAS MIXTURE
Patent Information
- Application Number
- TR202615452
- Authority / Receiving Office
- TR · TR
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-09-09
- Publication Date
- 2026-09-21
Smart Images
Figure 00000024_0000
Abstract
Description
1 TARIFF HIGH PURITY DINITROGEN TETHROXIDE FROM AQUEOUS NOX GAS MIXTURE. INTEGRATED COOLING AND PRESSURE FOR ACHIEVING (NTO) CONTROLLED PURIFICATION METHOD 5 Technical Field to Which the Invention Relates The invention involves obtaining high-purity dinitrogen tetroxide (NTO) from an aqueous NOx gas mixture. an integrated cooling and pressure-controlled purification method for this purpose and this It relates to the system in which the method is applied. 10 State of the Art Dinitrogen tetroxide (N2O4) belongs to the nitrogen oxides group, along with nitrogen dioxide (NO2). an important chemical that exists in equilibrium and is particularly known for its oxidizing properties. It is a compound. This substance, which can exhibit NO2 / N2O4 equilibrium depending on room temperature, is 15 Especially in chemical and industrial applications requiring strong oxidizing agents. It is used for various purposes, particularly as an oxidizing component in rocket propulsion systems. as a reactive agent in nitration and other chemical synthesis processes, also as an intermediate chemical or processing agent in some specific industrial processes. is being evaluated. Therefore, dinitrogen tetroxide, both due to its high reactivity and its 20 a compound that attracts attention due to its strategic importance in technical applications It carries. In current technology, dinitrogen tetroxide (NTO) production generally involves the production of nitrogen oxides, especially Based on the dimerization of nitrogen dioxide (NO2) under temperature and pressure conditions 25 It is based on. In this context, known methods mostly rely on previously obtained data. or a gas mixture containing NO2 obtained from a different source is used, The gas mixture in question is subjected to cooling and / or pressurization processes to produce 2NO2. ⇌ The N2O4 balance is shifted in favor of the product. In current systems, this forms the basis of the process. Generally, the gas is cooled, condensed, compressed if necessary, and the resulting 30 This is formed by the collection of N2O4 in the liquid phase. However, known solutions... A significant portion of them are designed for dry or low-moisture gas streams, to eliminate the negative effects of water in the inlet gas on the process It does not include an integrated and multi-stage drying infrastructure. Furthermore, the existing 2 In these methods, dimerization efficiency can mostly be improved simply by lowering the temperature. efforts are being made to increase it, while the pressure parameter is optimized to a sufficient level under all conditions. It appears that this is not the case. In addition, many systems are designed according to fixed operating conditions. Because it is designed to adapt to different gas compositions, flow rates and operating conditions. In this respect, it shows limited process flexibility. Also, in the current technology, equipment 5 In most cases, the sizing is based on experimental assumptions or classical engineering. It is based on approaches that support simulation-based holistic process integration in every aspect. It appears that time could not be provided. Traditional NTO production methods produce NO2. While outlining the basic principle based on the dimerization of moist NOx gases direct processing, minimizing NO2 loss, high efficiency and very high 10 Obtaining a product of high purity using a modular and energy-efficient system at laboratory / pilot scale. It has various technical limitations in terms of installation. Traditional dinitrogen tetroxide (NTO) production methods typically involve dry and pure NO2 gas. It operates with [this]. However, in practice, NOx gas, especially that obtained from nitric acid production, is 15 The mixtures contain a certain amount of water vapor, inert gases, and varying ratios of NO / NO2. Current systems appear to have various technical shortcomings as a result. The water present in the NOx mixture can cause undesirable side reactions within the reactor. It is known that this opens the door and reduces process efficiency, and this problem exists in traditional systems. where an effective drying infrastructure to address this issue is not available or the drying process is not process 20 It appears that this requires implementation through additional external systems. Furthermore, the existing Systems are mostly based on a single pressure or a single temperature operating point. Because it is designed this way, process flexibility is not sufficiently provided and different operations When operated under these conditions, productivity decreases significantly. In addition, Temperature control is generally achieved through stationary coolers, and this situation is 25 by increasing both cooling costs and total energy consumption This leads to inefficiency in numerous industrial systems. On the other hand, Instead of a simulation-based design approach, an experimental trial-and-error method it was established, therefore it has sufficient process modeling and optimization infrastructure. This is because the equipment is either too large or too small in capacity. 30 It appears to create a risk. Furthermore, the purity of the product obtained after synthesis... There are also significant limitations in this regard, and many systems reported in the literature... The product purity remains at 96–98% and it can be considered rocket-grade. It appears that a purity level of 99.5% or higher has not been achieved. In addition, 3 Most systems that can operate successfully on an industrial scale are developed in laboratories. or cannot be operated with the same accuracy and stability on a pilot scale, especially equipment volume, installation cost and control system requirements in this downsizing process It is considered to impose significant limitations. As stated in patent application number US3070425A, in the known state of the art In this method, water in the gas mixture is removed only by condensation, The final product still contains up to 7% moisture. This reduces product quality and This can cause the reaction to proceed in reverse. The process generally involves compression, This was achieved using condensation and columnar systems. The conversion of NO2 to N2O4 is 10 The yield is unclear. The resulting product is raw N2O4, and it is similar to re-rectification. Purification is achieved using additional columns. The system is quite complex. NOₓs are purified with HNO₃. When reacted, undesirable N₂O₅ may be formed. This substance is extremely reactive and It is explosive. Additionally, operating at high temperatures increases equipment corrosion. There is no reaction or system simulation. Each process step is in a separate column, 15 This is done in a costly and energy-intensive way. In the known state of the art, moisture is described in patent document number RU2547752C2. It is indirectly eliminated by condensation and washing with nitric acid; however, moisture The measurement has not been verified by analytical instruments. The document in question is primarily based on NOₓ-20. It describes the N₂O₄ conversion through a chemical process chain; however, monitoring and control are not necessary. Its systematics are weak. The azeotropic mixture is used intentionally (for example, There is a system for the production of superazeotropic nitric acid. However, this mixture does not guarantee product purity. It reduces, increases process complexity. NO₂ forms an azeotrope with water vapor. As a result, complex reactions develop that reduce product purity. The system processes this mixture in 25 It uses advanced multi-stage columns for parsing. The limitations and inadequacies of current technological solutions in dinitrogen tetroxide production. Most of their processes are designed for dry or low-moisture gas streams. Because of this, moist NOx gases cannot be processed directly and reliably, 30 Water in the inlet gas can cause undesirable side reactions in the reactor environment, This leads to a decrease in conversion efficiency and a reduction in product purity, currently an efficient and process-integrated multi-stage drying infrastructure in the systems 4 The absence of NO₂ or the need for additional off-process systems in the drying process Although temperature is given weight in the conversion of N₂ to O₄, pressure is also a factor. The effect of the parameter on dimerization equilibrium is not sufficiently optimized Failure to do so, therefore, increases NO₂ loss and limits product yield, the current situation Most processes are dependent on a single temperature and / or a single pressure point, constant 5 Because it is designed with business logic in mind, different gas compositions, flow rates and operating conditions are possible. lack of process flexibility to adapt to the conditions, temperature Cooling control is generally carried out with stationary coolers. Rising costs and total energy consumption necessitate energy recovery and Due to insufficient use of cyclical feedback solutions, process 10 Decreased efficiency in equipment design and sizing in many systems. It is not based on simulation-supported holistic process integration and rather unnecessarily large because it was determined through an experimental trial-and-error approach. The emergence of inadequate or bottleneck-creating equipment selections is discussed in the literature. The product purity remains at 96–98% in most cases, especially for rocket-grade 15. Failure to achieve the required purity level of 99.5% or higher for industrial use. systems that can operate at scale can be replicated at laboratory or pilot scale with the same accuracy, stability, and inability to reduce feasibility, equipment volume, installation cost and control The fact that these systems pose a significant limitation in this downsizing, as well as being modular and compact, The limited number of portable and deployable system designs in real field conditions. 20 For reasons such as these, it has become necessary to make improvements in this area. Brief Description and Objectives of the Invention The invention involves obtaining high-purity dinitrogen tetroxide (NTO) from an aqueous NOx gas mixture. integrated cooling and pressure-controlled purification method for this and these 25 It relates to the system in which the method is applied. One aim of the invention is to produce high-performance gas mixtures containing NOx and especially moisture. an efficient, controlled and feasible method for producing dinitrogen tetroxide (N₂O₄) of high purity. The invention involves developing a method to first condense the water in the gas mixture by means of 30 condensation. transitioning to liquid phase, then removing it with drying units and afterwards by feeding the dried gas into a dimerization reactor under temperature and pressure conditions An efficient, controlled, and feasible method is provided. Another purpose of the invention is to address the inability to work with humid gas in existing systems. The aim is to prevent the resulting decrease in yield and side reactions. The invention involves the controlled condensation of water in the inlet gas in heat exchangers and the remaining water. Efficiency reduction due to moisture retention by zeolite-based drying columns. This prevents and avoids the occurrence of side reactions. 5 Another aim of the invention is to increase the conversion efficiency of NO₂ to N₂O₄ and It is the shifting of the dimerization equilibrium towards product formation. In the invention, the gas controlled pressurization, cooling to a low temperature, and in the reactor By controlling both temperature and pressure, the conversion efficiency of NO₂ to N₂O₄ is 10. The dimerization rate is increased, and the dimerization equilibrium is shifted towards product formation. Another aim of the invention is to increase product purity beyond the levels of current technology. dinitrogen tetroxide (N₂O₄) is extracted to provide a level suitable for rocket-grade use. The goal is to develop a production method. This involves multi-stage concentration, drying, 15 integrated pressurization and low-temperature dimerization steps As a result of its application, N₂O₄ with a purity of over 99.5% is obtained instead. It has been brought. Explanation of Figures 20 Figure 1. Process flow diagram of the NTO production process: a) pressure and temperature gauges, b) flow meter, c) circulator, d) reactor, e) compressor, f) control valve, g) manual valve, h) check valve, i) heat exchanger and collection vessel Detailed Description of the Invention 25 The invention involves obtaining high-purity dinitrogen tetroxide (NTO) from an aqueous NOx gas mixture. It relates to an integrated cooling and pressure-controlled purification method for this purpose. The abbreviation NTO refers to dinitrogen tetroxide (N2O4). 6 In the process described in the invention, moisture removal is carried out in the first stage, and then the gas... The water vapor in this phase is primarily processed through temperature-controlled condensation. is maintained. Then, the reaction equilibrium is optimized by varying the pressure. The conversion of NO₂ to N₂O₄ has been achieved. Throughout the process, the water was completely removed. 5 for removal, including zeolite desiccants, molecular sieves, and Nafion membranes. Selective adsorbent systems were used. Thanks to this method, 99.5% purity was achieved. By producing N₂O₄, it is a suitable oxidizer for the aerospace and defense industries. Quality has been ensured. The invention describes the production of high-purity dinitrogen tetroxide (NTO) from an aqueous NOx gas mixture. An integrated cooling and pressure-controlled purification method for this purpose; i. Purification of an aqueous NOx gas mixture containing moisture via an inlet line. the intake gas is taken into the system and regulated by at least one pressure regulating element. by reducing the pressure of the stream, the gas stream purification system inlet 15 adjusting to the conditions, ii. The water within the inlet line must undergo at least one pre-concentration stage, the temperature of the water by means of at least one heat exchanger and collection vessel (i) partially transitioning to the liquid phase by lowering its condensation point, 20 iii. The water that is passed to the liquid phase must have at least one separation volume, tank, reservoir or phase separator. Physical removal of NOx-containing gas from the gas stream via an intermediary element, iv. Before the reaction, the gas stream may contain water which can reduce the dimerization efficiency. to remove its contents, remaining in the gas phase after pre-condensation The moisture is passed through at least one drying unit, and the gas stream is water by mass. reducing the content to below 0.01%, v. the dried gas stream through at least one pressure increasing compressor (e) 30 The pressure level must be brought to 3-6 bar for the reaction. 7 vi. After increasing the pressure, the gas stream, whose temperature has risen, undergoes at least a second heating cycle. dimerization reaction via exchanger or cooling stage Cooling to a temperature between -10 °C and 0 °C where the procedure will be carried out, vii. conveying the gas stream to a reactor (d) and the temperature in the reactor being between –10 °C and 0 5 Nitrogen is controlled simultaneously in the °C range and the pressure range of 3-6 bar. Dimerization reaction of components containing dioxide yields over 90%. conversion of dinitrogen to tetrooxide at the conversion rate, viii. Gas phase and liquid phase components of the stream obtained at the end of the reaction 10 by separating it in terms of its components, dinitrogen tetroxide with a purity of over 99.5% is obtained. (NTO) acquisition, ix. The product containing dinitrogen tetroxide must have at least one outlet line, collection volume, and separation point. recovery via unit or storage unit, 15 It includes the steps involved in the process. In a preferred application of the invention, dried gas in process step (v). The current is at least 5 bar pressure for the reaction via a pressure boosting compressor (e) 20 It is brought to this level. Increasing pressure in process step (vi) in a preferred application of the invention The gas stream, whose temperature has subsequently risen, must pass through at least a second heat exchanger or cooling system. The dimerization reaction will be carried out via the step at -7 °C 25 It is being cooled. The method described in the invention involves temperature, pressure, flow, and method throughout each stage of the process. parameters, pressure and temperature gauges (a), flow meter (b) at least one measurement and is monitored by a control element. 30 In one application of the invention, the drying unit consists of zeolite-based drying columns and molecular It includes at least one of the following drying elements: screens or Nafion membrane-based drying elements. 8 In one application of the invention, in process step (vii), inside reactor (d) The temperature is -6 °C and the pressure is 5 bar. The invention describes an integrated system for obtaining high-purity dinitrogen tetroxide (NTO). Cooling and pressure-controlled purification system; 5 — pressure and temperature gauges (a), flow meter (b), valves and control elements Simultaneous control of temperature and pressure parameters through this means It was determined that the dimerization equilibrium (Kc) was in the direction of dinitrogen tetroxide formation. components containing nitrogen dioxide are shifted and NO₂ loss is minimized. reactor (d) where the reaction takes place, 10 —the dried gas stream to the 3-6 bar pressure level required for the reaction at least one pressure boosting compressor (e) that enables its delivery, — ensuring continuous circulation of the heat transfer fluid within heat exchangers circulator (c), —by lowering the temperature of the inlet gas below the condensation point of water, the gas stream 15 at least one temperature that causes the water inside to condense and collect. heat exchanger and collection vessel (I), —a phase separator that physically separates water that has turned into liquid from the gas phase. — By retaining the moisture remaining in the gas stream exiting the phase separator, the gas stream becomes water by mass. At least one drying unit that reduces the content to below 0.01%, 20 ⎯ obtained by separating the stream at the outlet of reactor (d) into gas and liquid phases. at least one source from which dinitrogen tetroxide with a purity of over 99.5% was recovered. outlet line and collection-storage unit, It includes. In one application of the invention, the system in question reduces the condensable moisture in the inlet gas to 25. first heat located before compressor (e) inlet for the purpose of removal The heat exchanger recirculates the high-temperature gas coming from the compressor (e). positioned at the compressor (e) outlet in order to reduce the reaction temperature It includes a second heat exchanger. In one application of the invention, the aforementioned heat The changers are made of AISI 316L stainless steel with a wall thickness of 5 mm and are 30 It has a cross-flow, double-tube serpentine (shell & coil) structure. 9 In one application of the invention, the aforementioned reactor (d) operates at a working pressure of 5 bar. It is operational, capable of withstanding a design pressure of 10 bar, and features a cooled jacket structure. It also has an internal spiral tube system and a total heat transfer area of 2 m2. It includes this feature. This allows it to increase the pressure without further lowering the temperature. The advantage of utilizing the dimerization reaction with the same yield or a pressure of 5 by keeping the gas temperature low, similar dimerization efficiency can be achieved. It has advantages. In one application of the invention, the drying unit consists of zeolite-based drying columns and molecular It includes at least one of the following drying elements: screens or Nafion membrane-based drying elements. In one application of the invention, the compressor (e) increases the gas outlet pressure to 5 bar. It is an oil-free type industrial gas compressor capable of increasing power output. In one application of the invention, the heat exchangers are made of stainless steel (AISI 316L). It is a manufactured product and includes a cross-flow tube. In one application of the invention, the control elements mentioned are the adjustment valve (f) manual. valve (g) and check valve (h). 15 The invention describes the production of high-purity dinitrogen tetroxide (NTO) from aqueous NOx gas mixtures. A method for its production has been developed. The traditional methods found in the literature... Unlike other methods, in this process, moisture removal is the first step. This is being carried out by processing water vapor in the gas phase, primarily under temperature control. It was held in place by condensation. Then, reaction equilibrium was reached by pressure change. 20 The conversion of NO₂ to N₂O₄ was achieved by optimizing the process. Throughout the process, the water... zeolite desiccants, molecular sieves and / or Nafion for complete removal Selective adsorbent systems such as membranes were used. The entire process was carried out using Aspen Plus. The process is based on temperature, pressure, and flow rate values modeled in a simulation environment. equipment (heat exchanger, condenser, drying column, reactor, collection tank) 25 It has been optimized. Thanks to this method, N₂O₄ production with a purity of over 99.5% is achieved. This process has resulted in an oxidizing agent of suitable quality for the aerospace and defense industries. The invention describes an integrated drying and dimerization system for the production of N₂O₄ from moist gas. It is being developed. The systems used in current technology mostly use dry NO₂ gas and 30 It is currently being studied, and the system efficiency and obtained results are being improved in gas mixtures with high moisture content. The product purity is seen to be significantly reduced. In contrast, the system described in the invention, The water present in NOx mixture gases is first cooled by controlled condensation. removal, followed by zeolite-based dryers and / or Nafion membranes. by enabling additional drying through dryers It is structured in such a way that the gas phase drying process is sequential, continuous, and highly efficient. It is being produced with a purity of over 99.5% N₂O₄ 5, even in humid environments. production becomes possible. In the present invention, thermodynamics based on aspen plus and Equipment integration has been achieved. The equipment is integrated into existing process applications. It is usually sized according to fixed operating conditions, therefore the system It is known that its flexibility and efficiency remain limited. However, in the system that is the subject of the invention... Modeling was performed using Aspen Plus software, and the process temperature, pressure, and 10 Dynamic equipment optimization taking flow rates into account. This is being implemented. Thanks to this approach, it can operate under different input conditions. A flexible, adaptable and energy-efficient system is obtained. In the invention Maximum dimerization efficiency is achieved through pressure-controlled equilibrium shifting. In current systems, the conversion of NO₂ to N₂O₄ mostly takes only 15 minutes. This is achieved by lowering the temperature, but pressure control is achieved through dimerization. Its impact on the balance is not being optimized sufficiently. In the system described in the invention, the temperature and pressure parameters are equal within the reactor. It is monitored periodically and the dimerization equilibrium (Kc) reaches a maximum conversion of 20°C. It is adjusted according to the yield. In this way, NO₂ loss is minimized and product yield is increased. However, this is being increased. Existing systems used on an industrial scale are mostly large. These are structures requiring bulky and fixed installations, for laboratory and / or pilot scale. Their adaptability to applications remains limited. The system described in the invention, however, is modular. Designed to be compact and portable, especially for pilot-scale use 25 It is optimized for this purpose. Thanks to this structure, the system can be used both in laboratory environments and It is becoming applicable in small-scale production facilities. In the current technology... In a significant portion of these systems, gaseous waste components are released into the atmosphere. or cannot be effectively recovered within the process. In the system that is the subject of the invention The N₂O₄ obtained after condensation is recycled back into the system. recharging is ensured, and heat recovery is also provided with the help of a heat exchanger. Energy losses are reduced through this mechanism. Thus, both raw material loss and energy loss are minimized. both the energy consumption is reduced and the overall energy efficiency of the process is increased. In the current technique... Product purity is observed to remain at levels of 96–98% in most cases. 11 In contrast, the proposed system achieves 99.5% purification thanks to its multi-stage purification approach. The production of N₂O₄ with high purity is ensured. The system developed as the subject of this invention provides multiple technical solutions simultaneously. Introduction The water contained within the gas was first converted to the liquid phase in condensing heat exchangers, 5 then completely retained by means of zeolite-based drying columns, thus It is possible to directly process and directly use moist NOx gases. It has been brought into the system by pressurizing the gas in a controlled manner from 1 bar to 5 bar. extracted and simultaneously cooled to -8°C before being directed to the reactor, this In this way, the N₂O₄ dimerization efficiency has been increased above the values reported in the literature. 10 Additionally, the load, input-output of each piece of equipment can be determined using Aspen Plus simulation. parameters and gas conversion rates have been determined, thus enabling equipment design and Process integration was carried out with the support of simulations, and excessive investment was avoided. The risk of bottlenecks or process bottlenecks has been eliminated. On the other hand, Controlled cooling was achieved in the heat exchangers with Dowtherm-Q based circulation, 15 The reactor temperature was kept constant, and consequently, the system's energy consumption was reduced. Energy efficiency has been ensured. However, the gas content needs to be optimized. As a result, the conversion of NO₂ to N₂O₄ was achieved at over 90%, and the reactor The purity of the product obtained at the output is increased to over 99.5%, making it suitable for rocket-grade use. A suitable high-purity product has been obtained. In addition, the system includes a heat exchanger, dryer, 20 manufactured and assembled in a real environment, including the reactor and control equipment. It has been developed and verified through experimental studies; it is portable, modular, and laboratory-grade. This has resulted in a feasible structure suitable for pilot-scale use. Figure 1 illustrates the flowchart for the NTO production process simulation. This 25 The figure shows a device developed to produce high-purity N₂O₄ from a gas mixture containing NOx. the modeled version of the integrated process in the Aspen Plus simulation environment This shows that condensation is achieved by optimizing the pressure and temperature of the inlet gas. The drying, pressurization, and low-temperature dimerization stages are as follows: This has been demonstrated. The simulation outputs of the system show that the equipment dimensions are 30. This has formed the basis for its creation and the determination of process parameters. This figure, Obtaining high-purity dinitrogen tetroxide (N₂O₄) from a gas mixture containing NOx. Simulation flow of the process developed for this purpose, modeled in the Aspen Plus environment. It shows the diagram. According to the simulation output, the system is designed as follows: 12 Each piece of equipment was manufactured domestically, the system was assembled, and synthesis was carried out. Studies have confirmed that the system operates successfully. The system has a pressure reducer. valves (RV), temperature gauges (TI), pressure gauges (PI), manual valves (HV), Instrumentation elements such as control valves (CV) and flow indicators (FI) are included. It also includes the following basic components: reactor, heat exchangers, compressor, and drying unit. The equipment, their physical layouts, and control strategies are all integrated within this system. The designs are based on a design pressure of 10 bar and a test pressure of 15 bar. This was done. The process parameters obtained from the Aspen Plus simulation results... According to the specifications, heat exchangers are made of stainless steel (AISI 316L) material, cross-flow tube type. It has been specifically designed to be like this and manufactured by a local producer. 10 The reactor is a cooled jacketed structure capable of withstanding a working pressure of 5 bar. It has an internal spiral tube system and will provide a total heat transfer area of 2 m2. It is designed in such a way that it increases the pressure without further lowering the temperature. The advantage of utilizing the dimerization reaction with the same yield or the pressure By keeping the gas temperature low, similar dimerization efficiency can be obtained. 15 It has an advantage. The compressor can increase the gas outlet pressure up to 5 bar. It was selected as an oil-free type industrial gas compressor. Zeolite-filled drying columns. It will be optimized to perform water adsorption and achieve the 0% humidity target. All process elements are made with pipes in the DN08–DN25 range and valves (HV, CV). and integrated using indicators (TI, PI, FI). System setup 20 After completion, NOx obtained from the dilute nitric acid production process The mixture was passed through the system and the process was operated. Throughout the process, the gas The components were analyzed using an FTIR device, and at the system's input and output points... Temperature and pressure data have been monitored to be compatible with Aspen Plus simulation. This was observed as follows: A NO₂ → N₂O₄ conversion rate of over 90% was observed at the reactor outlet. It was obtained. The product collected in the liquid phase at the outlet was analyzed using spectroscopic and mass analyses. It has been examined and confirmed to be N₂O₄. System performance throughout the process, Parameters such as conversion efficiency, energy balance, and product purity were evaluated, and Both the system modeling and the physical installation were found to be successful. During the gas inlet stage, the pressure of the NOx gas mixture from the dilute nitric acid process. It is reduced and made suitable for system inlet. Water concentration and separation. During this stage, most of the water in the gas is removed using a heat exchanger and tank. It is converted to the liquid phase. During the gas drying stage, via drying columns 13 The moisture content in the gas is reduced to near 0%. Pressurization and cooling. During this stage, the gas, which is raised to 5 bar with the help of a compressor, reacts in the heat exchanger. It is cooled down to a certain temperature. During the reaction phase, the reactor is at a low temperature. N₂O₄ synthesis is carried out under high pressure. Product output stage. N₂O₄ is collected by separating it into gaseous and liquid phases. 5 In this invention, the removal of water in the gas phase is carried out in two consecutive stages. First, most of the water vapor is captured through temperature-controlled condensation, Then, the moisture is effectively removed using membrane dryers. This sequence... The drying approach produces a product with a purity of over 99.5%, even in humid NOx gas environments. this makes it possible to achieve the desired results and reduces moisture-related efficiency issues encountered in known techniques. It eliminates their shortcomings and reaction imbalances. Furthermore, the invention... Simultaneous control of reactor temperature and pressure to convert NO₂ to N₂O₄. The dimerization equilibrium (Kc) governed by the process is maintained at an optimum level throughout the process. This helps to minimize NO₂ losses and increase product yield. 15 The invention produces a very high purity NOx gas directly from NOx gas in a moisture-free environment. Sequential system that provides high-efficiency N₂O₄ production by minimizing NO₂ loss (99.5%). The drying process involves both temperature and pressure-controlled dimerization. a technique that provides optimization and process flexibility compared to existing techniques It provides an advantage. 20 In the method described in the invention, the water that condenses after the temperature is lowered is physically treated. is removed, and then the remaining moisture content, which is less than 0.1% by mass, is treated with zeolite-based It is removed by 99% by passing it through an adsorption unit. This means the product... It directly increases its stability and reduces the possibility of moisture-induced decomposition or degradation to zero. It brings them closer. The method described in the invention involves a spiral tube designed based on kinetic data. A jacketed reactor was used. The reaction was carried out at -6 °C and 5 bar conditions. This is carried out by controlling the reaction conditions of the process and ensuring safety. increased and scalable capabilities enabled, transitioning to industrial scale This has made things easier. Thus, process safety is increased, quality control is ensured, and industrial 30 Scaling up production becomes easier. The resulting N₂O₄ is concentrated and high purity is obtained. This has eliminated the need for additional rectification, making the process much more compact, faster, and more efficient. It has been evaluated as economical. Reaction conditions are controlled (cold and pressure). (below), N₂O₅ formation was prevented. All equipment used is AISI 316L. 14 Made of stainless steel, hazards are minimized. The entire process is Aspen Plus. It has been simulated. Parameters have been optimized, set up at the laboratory scale, and This has been confirmed by actual experimental data. Water in the gaseous phase is first condensed. Subsequently, the purity of the product was increased to 99% N₂O₄ using adsorbent material. Thus, the product... Storage life has been increased and the risk of product degradation has been reduced. Gas 5 in the method. Purification, transformation, and concentration processes are carried out modularly with 3 main units. This has been achieved. Thus, space saving, ease of maintenance and low investment costs are ensured. N₂O₅ was obtained because the reaction is carried out at a low temperature in this method. The formation of this problem has been prevented. Thus, a long-lasting, safe and low-risk system has been created. It has been established. The product obtained in the invention has high 10, especially FTIR and UV-Vis. Product purity and moisture content were quantitatively verified through process verification using sensitive analytical instruments. This has been measured with data. In the invention, during the production of N₂O₄, from the gas phase containing NO₂ – H₂O The risk of azeotrope formation during the transition to the liquid phase has been minimized. This is temperature-controlled. The process is carried out through cooling and drying processes. The system creates an azeotrope-forming humid environment. NO₂ vapors are first detected by FTIR, then condensation and UV-Vis analysis are performed on 15 It separates. This system is also suitable for the reuse or treatment of by-products. In this invention, process gas is monitored inline using FTIR. Final product analysis is performed using UV-Vis-NIR. The amount of water and NO₂ content are verified from the spectrum. The subject of the invention is 20 In this method, water vapor is identified early in the process using FTIR-based analysis and is specific. It is removed through cooling-condensation-moisture retention steps. Thus, the product A significant increase in purity is observed, and the process requires less energy and equipment. manageable conditions are ensured, azeotropic disruptive chemicals or extra columns. The need for it is eliminated. In this invention, a high 25% efficiency is achieved in the production of dinitrogen tetroxide (N₂O₄). Simultaneously achieving multifaceted goals such as purity, low moisture content, and heat recovery. a method that works with an integrated process system optimized to meet the requirements The method has been developed. In particular, energy recovery is achieved by using two heat exchangers. This ensures water retention, and the amount of water in the product is minimized with the moisture-retaining system. is being done. 30 The invention specifically focuses on a moisture-retaining column and a low-pressure system aimed at improving product quality. High temperature condensation systems are used in aerospace or other fields requiring high purity. It enables the production of N₂O₄ that meets the specifications required for use. Furthermore, measures the heat recovered at each stage of the process and quantifies the efficiency rates. The organization, which presents itself in this way, supports both environmental and economic sustainability. Thanks to this holistic structure, the invention is not just a production method, but also It acquires the characteristics of an optimized process design. The invention involves the efficient removal of moisture from the gas at low temperatures. Producing N₂O₄ with high efficiency under high temperature and pressure, heat recovery. with process integration and a modular, validated system. The aim is to ensure its establishment. In this context, the conversion of NO₂ to N₂O₄ is being investigated. Considering the problem of water availability reducing efficiency in the conversion process, gas 10 a multi-stage drying approach to remove moisture from within This process has been implemented. Using a heat exchanger, water separation up to 94% has been achieved. The remaining moisture was then completely removed by zeolite-based drying systems. 0.13 The water content, specified in kg / hour, becomes 0.002 kg / hour after zeolite drying. It has been reduced to this level, which corresponds to approximately 99% water removal. 15 The moisture content of the inlet gas was measured using an FTIR device at a temperature of 33 °C and a pressure of 2.2 bar. The experiment was conducted with approximately 5% H₂O content, and the moisture content in the output product was UV-Vis- Measurements using an NIR device showed values below 0 ppm. Furthermore, the literature generally indicates values between 5–10 bar. Despite operating under pressure and with multi-stage reactor systems, the product Faced with the problem of not being able to achieve the desired level of purity, only 5 bar pressure 20 A compact system has been designed that operates at a temperature of -6 °C. In this system... A conversion rate of over 90% was achieved at the reactor outlet, and 8% pure liquid phase was obtained. N₂O₄ has been detected. In addition, as a result of kinetic modeling studies... The optimum rate constant (k) value was calculated as 4.99 L / mol·s, and this value corresponds to the Borrell It has been determined that it is compatible with (1985). On the other hand, in traditional systems, the heat exchanger 25 Considering the problem of inefficient layout and temperature control, heat recovery The acquisition and process integration have been achieved. In this context, after the compressor... The rising temperature is reduced to -7 °C via a heat exchanger. Actual operation. Considering that the temperature is around 30–35 °C under these conditions When this is the case, according to the energy balances made through the heat exchanger, the heat return is 30. The recovery rate was calculated to be 79.6%. Furthermore, it involves a high-cost, multi-stage process. Faced with the inadequacy of column-free solutions, Aspen simulation was used to design... The system, including all its equipment, has been manufactured and put into operation. In this context, the system... The related 3D drawing, P&ID diagram, field setup and trial studies have been completed. 16 and the developed system is modular, feasible and experimentally validated It has been shown to have a structure. The method addresses the problem of removing water from a gas mixture. First, the temperature is reduced to approximately -5 °C via a heat exchanger, thereby increasing the condensation effect. The increased and remaining water is adsorbed with zeolite tanks with almost 100% adsorption. It has been determined that high efficiency can be achieved in the conversion of NO₂ to N₂O₄. In the simulation, the gas stream, which reaches a temperature of 195 °C after the compressor, is in the second stage. cooled to -7 °C with a heat exchanger, then to -6 °C and 5 °C inside the reactor. Under bar pressure conditions, 90% of gaseous NO₂ is converted to N₂O₄. The reaction was carried out. Furthermore, the rate constant in kinetic modeling was k = 4.99 L / mol·s. It has been calculated as follows: Precise separation of liquids and gases is possible. The condensed liquid was separated using tanks, and the moisture content before and after zeolite application was determined. The samples were analyzed both at the inlet using an FTIR device and at the outlet using a UV-Vis-NIR device. The purpose of the invention is to determine the amount of moisture present in the inlet gas in the method described. A Gasmet FTIR Gas Analyzer was used. The average volumetric water content in the inlet gas was determined. The amount was determined to be 4.93% H₂O. At the reactor outlet, especially S16 / S17 the amount of dissolved and relative moisture in the product that passes into the liquid phase in the lines An Agilent Cary 5000 UV-Vis-NIR Spectrophotometer was used for this purpose. 20 This device analyzes light transmittance in the visible and near-infrared regions to determine H₂O. It measures the relative absorption pattern of molecules, particularly in the liquid phase. This allows for the determination of the water concentration in the past product. Concentrated N₂O₄ liquid was used as a sample in the measurements. The measurement range was... The frequency range was selected as 400–2500 nm, with characteristic peaks for water at approximately 1400 nm and 1900 nm. The spectral signal was analyzed in the nm region. According to the results obtained, the spectral signal is relative to the reference It contains less than 0.01% moisture compared to pure N₂O₄, in other words, only trace amounts. It has been determined that it contains a certain level of moisture. Accordingly, the moisture level in the output product is... Technically, it is below 0.01%, meaning it is at the trace-level moisture level. It has been verified. The method described in the invention uses two heat exchangers. 30 The first of these is a heat exchanger that removes condensable moisture from the inlet gas. It is used for this purpose, and the second heat exchanger (heat exchanger) receives high heat from the compressor. The task is to reduce the temperature of the gas to its reaction temperature. Both heat exchangers are cross-flow, double-tube shell & coil type. 17 It is designed with temperature control provided by Dowtherm-Q circulation and a heat exchanger. The material chosen is AISI 316L stainless steel with a wall thickness of 5 mm. However, the success of the method depends solely on the use of at least two heat exchangers. No. The main success is removing moisture from the gas before the reaction and targeting using suitable heat exchanger systems to cool it to temperature 5 This is due to the fact that the method in question absolutely requires the use of two heat exchangers. It is not mandatory. Depending on the application, the reactor in the final stage can be both It can perform both condensation and cooling functions. In three heat exchanger systems... Intercooling can be performed more precisely. The optimum pressure value determined for the reactor is 5 bar, and this value allows for the further stages of the reaction. It has been determined that the pressure at which it reaches its maximum in the direction of N₂O₄ formation is as follows. Due to the exothermic nature of the reaction and the decrease in gas volume, The increase in pressure increases the conversion rate. The intended operating range for the system is 3– The pressure is 6 bar. Accordingly, at pressures below 3 bar, the conversion rate decreases and NO₂ 15 Recycling is increasing. At pressures above 6 bar, the equipment load... Despite the increase, the contribution to transformation remains limited. Therefore, the most appropriate technique The optimum pressure value was determined as 5 bar. The optimum temperature for the reactor. The temperature is -6 °C, indicating that the reaction proceeds in the forward direction, i.e., towards the formation of N₂O₄. A lower temperature was preferred. By lowering the temperature, the reaction equilibrium N₂O₄ 20 It is being shifted in that direction. The intended operating range for the system is –10 °C to 0 °C. It is between -10 °C, although the maximum conversion rate can be achieved at that temperature. Risk and process control difficulties may arise. At temperatures close to 0 °C. The conversion rate drops to 75–80%. At -6°C, it is above 90%. Transformation, ideal system balance and safe equipment operation all in one. 25 This is ensured. Accordingly, in the method described in the invention, the pressure inside the reactor is maintained. preferably around 5 bar, but applicable in the 3-6 bar range, and the temperature value is... Ideally, it operates at -6 °C, but can be operated between -10 °C and 0 °C. This temperature and pressure... conditions to achieve the conversion of NO₂ to N₂O₄ with maximum efficiency It has been optimized. The main units used in the concentration and separation stages are 30. It is a condenser and a phase separator. The condenser reduces the temperature of the inlet gas to condense. By lowering the water level below the condensation point, the phase separator enables the water to become denser, while the phase separator removes the liquid. It physically separates the water that has passed into the gas phase from the water vapor phase in the inlet gas. The ratio was analyzed by FTIR spectroscopy, and the percentage of water remaining in the output gas was determined using UV-Vis spectroscopy. 18 The moisture content of the product exiting the system was determined by measurement using an NIR spectrophotometer. The condenser cools the inlet gas to an average temperature of -5 °C. This temperature, Since it is below the condensation point of water vapor, most of the moisture is in the liquid phase. It passes through and is then physically removed from the medium by a phase separator. With this method, 92–95% of the water vapor is converted into liquid form and removed from the system. It is separated. This rate depends on the initial water content of the gas and the flow rate. It may vary by ±2. Accordingly, the cooling and cooling applied within the scope of the invention. With the separation system, 92% to 95% of the water in the gas phase is condensed into the liquid phase. It is passed through and physically separated from the system. This high-percentage water The removal process shifts the reaction equilibrium in favor of N₂O₄ and increases product purity by 10 It increases. Another technical reason for setting the lower limit for reactor temperature at –10 °C is... The freezing point of dinitrogen tetroxide is approximately –11.2 °C. This value... At temperatures below this level, the product solidifies, and the product 15 Blockages occur in the lines. Therefore, the operating temperature and dimerization the balance is shifted as much as possible in favor of the product, but the risk of solidification is maintained. It is kept in the range of -10 °C to 0 °C, preferably -6 °C, where it is not present. The liquid phase that condenses in the pre-condensation stage is the reaction of nitrogen dioxide with water. Since the resulting product is a dilute nitric acid solution, the aforementioned 20 The freezing point of the solution is significantly lower compared to pure water. This allows for preliminary... The condensation stage is possible even at temperatures below the freezing point of pure water. It can be operated without icing occurring and contains 92% to 100% water in the gas phase. 95% can be removed in a single step. During the pressure increase phase, the gas temperature theoretically reaches 195 °C for a short period. to prevent the thermal decomposition of nitrogen dioxide due to reaching its level The current at the compressor (e) outlet is directed directly to the second heat exchanger and The gas's residence time at high temperatures has been kept to a minimum. An alternative approach... In practice, the pressure increase process is carried out in two stages with intercooling, and 30 The compressor outlet temperature is kept below 120 °C. Nitrogen monoxide (NO) present in the inlet gas reacts with oxygen present in the gas stream. Oxidation to nitrogen dioxide (NO₂), increasing pressure after the pressure increase stage 19 and this speed increases with decreasing temperature. This allows free nitrogen to be released into the reactor stream. no monoxide remains, resulting from the combination of nitrogen monoxide and nitrogen dioxide. Formation of nitrous oxide (N₂O₃) and associated discoloration and loss of purity. is being prevented. The completion of the oxidation in question requires 99% in the liquid phase. It plays a decisive role in achieving purity. 5 at the reactor outlet. a non-condensable gas containing some nitrogen dioxide / dinitrogen tetroxide The nitrogen dioxide phase is fed back to the system inlet, thus reducing nitrogen dioxide loss and increasing total recovery. The success rate is being increased.
Claims
REQUESTS 1. Obtaining high-purity dinitrogen tetroxide (NTO) from an aqueous NOx gas mixture. integrated cooling and pressure-controlled purification method for and its feature is; 5 i. Purification of an aqueous NOx gas mixture containing moisture via an inlet line. by being incorporated into the system and through at least one pressure regulating element Purifying the gas stream by reducing the pressure of the inlet gas stream. Adjusting the system's input conditions, 10 ii. The water within the inlet line must undergo at least one pre-concentration. at least one heat exchanger and collection vessel (i) in the stage by lowering the temperature below the condensation point of water by partially converting it to the liquid phase, 15 iii. The water that is passed to the liquid phase must have at least one separation volume, tank, reservoir or phase physically separating the NOx-containing gas stream through a separating element removal, iv. Before the reaction, the gas stream can reduce the dimerization efficiency. To remove water content, the gas is pre-condensed. The moisture remaining in the phase is passed through at least one drying unit and then gasified. reducing the water content of the stream by mass to below 0.01%, v. At least one pressure increasing compressor for the dried gas stream (e) Bringing the pressure to a level of 3-6 bar for the reaction via vi. After increasing the pressure, the gas stream whose temperature has increased must have at least one Dimerization via a second heat exchanger or cooling stage 30 the temperature range of -10 °C to 0 °C at which the reaction will take place cooling, 21 vii. The gas stream is directed to a reactor (d) and the temperature in the reactor is -10 Simultaneously monitored at temperatures between °C and 0 °C, and pressure between 3-6 bar. by dimerization reaction of nitrogen dioxide-containing components Conversion of dinitrogen to tetrooxide at a conversion rate of over 90%, viii. Gas phase and liquid phase components of the stream obtained at the end of the reaction. by separating it in terms of its components, dinitrogen with a purity of over 99.5%. Obtaining tetroxide (NTO), ix. At least one outlet line, collection volume, of the product containing dinitrogen tetroxide, 10 recovery via separation unit or storage unit, It includes the steps of the process.
2. It is a method according to claim 1 and its characteristic is; 15 dried in process step (v). 5 for reaction through at least one pressure increasing compressor (e) of gas stream. The pressure is brought to a certain level.
3. It is a method according to claim 1 and its characteristic is; pressure in process step (vi). After the increase, the gas stream, whose temperature has risen, must have at least a second heat exchanger. or through a cooling step, the dimerization reaction 20 The process involves cooling it to -7 °C.
4. It is a method according to claim 1 and its feature is; mentioned in step (iv). the previous drying unit, zeolite-based drying columns, molecular sieves or It must contain at least one of the Nafion membrane-based drying elements.
5. A method according to claim 1, characterized by; (i) temperature at each stage of the method, 25 pressure and flow parameters pressure and temperature gauges (a), flow gauge (b) It is monitored with at least one measurement and control element.
6. It is a method according to claim 1 and its characteristic is that reactor (d) in process step (vii) The temperature inside is -6 °C and the pressure is 5 bar.
7. Obtaining high-purity dinitrogen tetroxide (NTO) from an aqueous NOx gas mixture. 30 It is an integrated cooling and pressure-controlled purification system for this purpose. feature; 22 — pressure and temperature gauges (a), flow meter (b), valves and control elements Simultaneous control of temperature and pressure parameters through this means It was determined that the dimerization equilibrium (Kc) was in the direction of dinitrogen tetroxide formation. where the nitrogen dioxide is shifted and NO₂ loss is minimized. Reactor (d) where the reaction of the components takes place, 5 —the dried gas stream to the 3-6 bar pressure level required for the reaction at least one pressure boosting compressor (e) that enables its delivery, ⎯ continuous circulation of heat transfer fluid within heat exchangers circulator (c) providing —by lowering the temperature of the inlet gas below the condensation point of water, the gas stream is 10 at least one temperature that causes the water inside to condense and collect. heat exchanger and collection vessel (I), —a phase separator that physically separates water that has turned into liquid from the gas phase. — By retaining the moisture remaining in the gas stream exiting the phase separator, the gas stream is reduced in mass. At least one drying unit that reduces the water content to below 0.01%, 15 ⎯ by separating the stream at the outlet of reactor (d) into gas and liquid phases dinitrogen tetroxide with a purity of over 99.5% was recovered. at least one outlet line and a collection-storage unit, It includes.
8. A system according to claim 7, whose characteristic is that the system has 20 in the inlet gas. from the compressor (e) inlet for the purpose of removing condensable moisture first, the heat exchanger positioned first, from the compressor. in order to reduce the high-temperature gas back to its reaction temperature It includes a second heat exchanger located at the compressor outlet.
9. A system according to claim 7 or 8, characterized by; heat exchanger material with 5 mm thick 25 mm. It is made of AISI 316L stainless steel with a thickness of and cross It has a flow-through, double-pipe serpentine structure.
10. A system according to claim 7, whose characteristic is that the reactor (d) operates at a working pressure of 5 bar. It is operational, capable of withstanding a design pressure of 10 bar, and features a cooled jacket. It has a total heat transfer area of 2 m2. 30 11. A system according to claim 7, characterized by its drying unit being a zeolite-based dryer. columns, molecular sieves or nafion membrane-based drying It must contain at least one of its elements. 23 12. A system according to claim 7, whose characteristic is that the compressor (e) has a gas outlet pressure of 5 It is an oil-free type industrial gas compressor that can raise the pressure up to bar.
13. A system according to claim 7, whose characteristic is; control elements adjustment valve (f) It has a manual valve (g) and a check valve (h). 10 20 30