Propylene Recovery Research Articles

Polymer-grade propylene production through temperature swing adsorption: Molecular simulation and techno-economic analysis

Producing polymer-grade propylene from the propylene-rich mixtures can be quite challenging since the most commonly employed technology, distillation, requires high-energy input and is expensive. Therefore, identifying less-costly, efficient, and environmentally friendly methods, such as the use of the adsorptive process, is highly desirable. In this regard, six pure silica zeolites (AFV, AST, AVL, IFR, LEV, and SWY) as propane selective adsorbents are investigated for the separation of 10 mol.% propane and 90 mol.% propylene mixture. Molecular simulation Monte Carlo (MC) is used to calculate framework structure parameters such as pore volume, surface area, and framework density of pure silica zeolites. Also, adsorption isotherms, propane selectivity, and working capacity are presented using MC calculations. The Langmuir-Freundlich isotherm model is utilized to calculate isotherm parameters. A system model is implemented in Aspen Adsorption software (version 11) and breakthrough curves are achieved. The Temperature Swing Adsorption (TSA) cycle is simulated and key performance parameters such as propylene purity, recovery, and productivity for all six silica zeolites are calculated. Finally, economic analysis of the TSA process is performed using the Aspen Capital Cost Estimator (version 11) and Aspen Process Economic Analyzer (version 11) and compared with the cost of the conventional distillation process. Results showed that the capital cost and operating cost of temperature swing adsorption are 42.3 % and 91.37 % less than those of distillation, respectively.

Scalable Synthesis of Robust MOF for Challenging Ethylene Purification and Propylene Recovery with Record Productivity.

Ethylene (C2H4) purification and propylene (C3H6) recovery are highly relevant in polymer synthesis, yet developing physisorbents for these industrial separation faces the challenges of merging easy scalability, economic feasibility, high moisture stability with great separation efficiency. Herein, we reported a robust and scalable MOF (MAC-4) for simultaneous recovery of C3H6 and C2H4. Through creating nonpolar pores decorated by accessible N/O sites, MAC-4 displays top-tier uptakes and selectivities for C2H6 and C3H6 over C2H4 at ambient conditions. Molecular modelling combined with infrared spectroscopy revealed that C2H6 and C3H6 molecules were trapped in the framework with stronger contacts relative to C2H4. Breakthrough experiments demonstrated exceptional separation performance for binary C2H6/C2H4 and C3H6/C2H4 as well as ternary C3H6/C2H6/C2H4 mixtures, simultaneously affording record productivities of 27.4 and 36.2 L kg-1 for high-purity C2H4 (≥99.9 %) and C3H6 (≥99.5 %). MAC-4 was facilely prepared at deckgram-scale under reflux condition within 3 hours, making it as a smart MOF to address challenging gas separations.

Scalable Synthesis of Robust MOF for Challenging Ethylene Purification and Propylene Recovery with Record Productivity

AbstractEthylene (C2H4) purification and propylene (C3H6) recovery are highly relevant in polymer synthesis, yet developing physisorbents for these industrial separation faces the challenges of merging easy scalability, economic feasibility, high moisture stability with great separation efficiency. Herein, we reported a robust and scalable MOF (MAC‐4) for simultaneous recovery of C3H6 and C2H4. Through creating nonpolar pores decorated by accessible N/O sites, MAC‐4 displays top‐tier uptakes and selectivities for C2H6 and C3H6 over C2H4 at ambient conditions. Molecular modelling combined with infrared spectroscopy revealed that C2H6 and C3H6 molecules were trapped in the framework with stronger contacts relative to C2H4. Breakthrough experiments demonstrated exceptional separation performance for binary C2H6/C2H4 and C3H6/C2H4 as well as ternary C3H6/C2H6/C2H4 mixtures, simultaneously affording record productivities of 27.4 and 36.2 L kg−1 for high‐purity C2H4 (≥99.9 %) and C3H6 (≥99.5 %). MAC‐4 was facilely prepared at deckgram‐scale under reflux condition within 3 hours, making it as a smart MOF to address challenging gas separations.

Improvement of model predictive control on a depropaniser: an industrial case study

In this work, improvements to a model predictive controller in an industrial facility is presented. A depropaniser column used to separate propane and propylene from heavier components was experiencing sporadic process instabilities which was impacting product purities. A soft sensor to measure C4 hydrocarbons was inaccurately predicting the actual composition, which caused the controller to behave erratically. A simple linear regression implementation improved the accuracy of the soft sensor significantly, which allowed further optimisation of the controller. Large benefits in process stability and propylene recovery were observed.

Quasi-Discrete Pore Engineering via Ligand Racemization in Metal-Organic Frameworks for Thermodynamic-Kinetic Synergistic Separation of Propylene and Propane.

The adsorptive separation of propylene and propane offers an energy-efficient alternative to the conventional cryogenic distillation technology. However, developing porous adsorbents with both high equilibrium and kinetic selectivity remains extremely challenging due to the similar size and physical properties of these gases. Herein, this work reports a ligand racemization strategy to construct quasi-discrete pores in MOFs for a synergistically enhanced thermodynamic and kinetic separation performance. The use of enantiopure l-malic acid versus racemic dl-malic acid as ligands afforded isoreticular Ni-based MOFs with contrasting one-dimensional channels (l-mal-MOF) and quasi-discrete cavities connected by small windows (dl-mal-MOF). The periodic pore constrictions in dl-mal-MOF significantly increased the differentiation in diffusion rates and binding energies between propylene and propane. dl-mal-MOF exhibited an exceptional propylene uptake of 1.82 mmol/g at 0.05 bar and 298 K along with an ultrahigh equilibrium-kinetic combined selectivity of 62.6. DFT calculations and MD simulations provided insights into the synergistic mechanism of preferential propylene adsorption and diffusion. Breakthrough column experiments demonstrated the excellent separation and high-purity recovery of propylene over propane on dl-mal-MOF. The robust stability and facile regeneration highlight its potential for propylene purification applications.

Permylene™ membrane technology: An efficient approach to separate propylene from propane

Permylene™ demonstration system (PDS), a membrane-based pilot unit for olefin/paraffin separation, is designed and fabricated by Imtex Membranes Corp. (Imtex). The PDS, equipped with pilot-scale Permylene™ elements, is capable of treating up to 3 kg/h of olefin/paraffin mixture. The PDS unit is installed in Imtex's testing lab in Mississauga, Ontario, Canada. Various plant-collected and lab-blended olefin/paraffin mixtures involving ethylene/ethane (C2), propylene/propane (C3), and butene/butane (C4) have been assessed on the unit. This paper is focused on the application of PDS for C3 separation, and a series of remarkable performances that have been achieved by the Permylene™ membrane and PDS unit. Propylene purity of over 98.5 vol% in the permeate/product stream has been reached over a wide range of propylene recovery rates, which could offer significant flexibility to meet various industrial operation conditions. Furthermore, the PDS unit demonstrates its stability and efficiency with 1200 hrs of continuous C3 permeation. Finally, a case study of recovering 90 % of propylene from 15,000 kg/h of C3 is performed to estimate energy consumption in commercial applications. The energy consumption of the Permylene™ process is calculated and compared with that of the distillation process. The result indicates that the energy consumption in PDS is extremely low, equal to only 8 % of that required in distillation. The study undeniably validates Permylene™'s remarkable capability for C3 separation, highlighting its potential as a viable and energy-efficient alternative to traditional distillation.

Process Simulation and Integration of Natural Gas Condensate Recovery Using Ethane–Propane Refrigerant Mixture

Separating heavy components from natural gas not only enhances safety, improves pipeline transportation, ensures product quality, and addresses environmental considerations, but it also exerts an influence on global energy trends. Therefore, separating heavy components is necessary and can result in beneficial goods. This article presents a comprehensive study on the process simulation and optimization of the recovery of natural gas condensate via the combined refrigeration of a mixture of ethane and propane as a refrigerant. The optimization objectives include maximizing the recovery of ethane and propane, minimizing energy consumption, and achieving desired product quality targets. A sensitivity analysis was performed to assess the impact of key parameters on process performance. Using Aspen HYSYS software, the influence of the cooler outlet stream temperature and expander outlet stream pressure on the shaft power and profit of a dry gas compressor was analyzed based on the operating conditions of the case plant, which has a processing capacity of 2988 kmol/h. The profitability of the plant is at a maximum when the cooler’s outlet stream temperature is −61 °C and the expander’s outlet stream pressure is 2500 kPa. After optimization, the refrigeration cycle system can reduce the plant’s energy consumption by 1516.4 kW. An optimized process design can lead to enhanced recovery efficiency, reduced energy consumption, and improved profitability in the natural gas industry.

An Inclusive Review on the Assessment of Different Techniques for Natural Gas Liquid Recovery

AbstractA comprehensive review is presented on the natural gas liquid (NGL) recovery process with emphasis on process description, energy requirements, NGL production, operating cost, and propane recovery. The industry standard single‐stage (ISS), recycle split vapor (RSV), cold residue reflux (CRR), and gas subcooled process (GSP) technologies focus on the improvement in the rectifying section of the demethanizer column, while the enhanced NGL recovery process (IPSI) focuses on the stripping section of the column. The fluor process consists of an absorber, a scrub column, and heavy hydrocarbon (HHC) separator, which form the integrated process of liquification and NGL separation. For rich feed, the economic performance, payback, and total annualized cost (TAC) of the IPSI process were lower than the other processes. For lean feed, the results of the scrub column scheme demonstrate the finest economic performance.

Energy, economic and environment assessment of membrane-cryogenic hybrid recovery propane process — Process simulation and life cycle assessment

Prevention and control of volatile organic compounds (VOCs) is one of the principal directions of air pollution control. Propane is not only a typical gas of VOCs but also a high value product. In this work, membrane-cryogenic hybrid processes to recover propane from nitrogen were studied by process simulation. Meanwhile, life cycle assessment methods were also used to assess the environmental impact of the entire life cycle process. Performance evaluation of the hybrid process was quantified in three aspects: energy, economic, and environment. The evaluation results indicated that it has more environmental and economic benefits to recover propane from 1.0 to 5.0% C3H8/N2. The energy consumption and recovery cost could decrease significantly. The lowest propane recovery costs are 984 USD/ton (1.0% C3H8/N2) and 234 USD/ton (5.0% C3H8/N2), respectively. At the same time, the environmental impact (excepted water resources consumption) generated by the hybrid process is substantially lower than by the cryogenic process. Pollutants output of hybrid processes is less than one-third of the cryogenic process. Climate change (GWP) can reduce from 2.37 × 104 kg CO2 eq to 4.54 × 103 kg CO2 eq to recover 1 ton propane from 1.0% C3H8/N2. Compared to propane processes produced from natural gas or liquefied petroleum gas, the environmental impacts caused by the hybrid processes are not much more than. In general, the membrane-cryogenic hybrid process is a green and economical technology to recover propane.

Reducing energy costs during solvent regeneration at the tar deasphalting unit

For propane tar deasphalting units, a rather high energy intensity of the technological process is characteristic. In order to reduce it, an assessment was made of the possibility of reducing the steam consumption during the regeneration of propane from asphalt solution. The study was carried out using a Honeywell UniSim Design modeling system, in which a model of a propane tar deasphalting unit was formed. The Peng-Robinson method was used as a mathematical package for calculating the thermodynamic properties of the components of the fractions. The component composition of the feedstock is represented by oil fractions with boiling points from 405 to 616 °C. When carrying out a computational experiment, the following values of technological parameters were used: the tar consumption was 38.9 t / h, the ratio (propane: raw material) was (6.4: 1), the yield of deasphalted oil was about 30 wt%. The performed analysis of a typical scheme for the regeneration of propane from asphalt solution showed that in the process stream supplied to the feed of the stripping column K-6, there is already a sufficiently large amount of a vapor phase consisting practically of propane and traces of oil fractions. To efficiently use the energy of the flow without attracting additional energy costs, it is advisable to separate the gas and liquid phases before they enter the column K-6, that is, to include an additional separator in the technological scheme before it. The performed computational experiment showed that in the proposed version of the technological scheme, the steam consumption required for the release of propane decreases by 17.5%, which, accordingly, for the subsequent devices of the scheme, reduces the amount of water discharged into the sewage system. Optimization of technological modes of the stripping column K-6 provides a clear separation of propane, in the flow of which the content of bitumen fractions is 0.03 mol%, which makes it possible in industrial conditions to return the flow of propane to the feed of the extraction column. The proposed technological solution for propane recovery can be used in the processes of one- and two-stage tar deasphalting.

Optimization of membrane-cryogenic hybrid propane recovery process: From molecular to process simulation

Efficient volatile organic compounds (VOCs) recovery could not only prevent air pollution, but also achieve potential economic benefits. However, the traditional VOCs recovery technology faces the challenges of high energy consumption and low recovery rate. In this work, membrane materials and the membrane-cryogenic hybrid process for propane recovery was designed and optimized by using molecular and process simulation, respectively. In detail, 152 kinds of MOFs/PDMS and MOFs/PTMSP mixed matrix membranes were predicted through molecular simulation. PCN-48/PDMS and ZIF-12/PTMSP mixed matrix membranes (MMM) with high selectivity up to 56.6 and 31.9 and permeability up to 7.1 × 103 and 7.0 × 104 Barrer were obtained. The process simulation results indicated that optimized two-stage membrane-cryogenic (Mem-Cry-Mem) hybrid process could reduce operating expenditure from 1.28–2.24$/kg to 0.41–0.54$/kg and increase condensation temperature from −131∼ −110 °C to −105∼ −72 °C. Furthermore, the optimized Mem-Cry-Mem hybrid process could get high purity (>99% mol/mol) propane with energy consumption reduced by 48.5–73.8%. The hybrid process based on MMM presented significant techno-economic potential in the field of VOCs recovery.

Separation of natural gas liquids and water from gas condensate

Unlike dry gas reservoirs, condensate gas reservoirs contain a considerable amount of natural gas liquids which should be extracted to maximize energy usage. This paper uses Bryan ProMax to set up the processing units for the recovery of natural gas liquids and removal of water. The parameters for the simulation were a gas composition which assumes a sweet gas content. The outcome of the simulation includes reduction of water content below 7 lbm/MMscf, recovery of methane and recovery of propane and isobutane only. The glycol dehydration unit minimized water impurity, while cooling with Joule–Thomson valve and heat exchangers help in methane recovery and separation from natural gas liquids. The results show that natural gas liquid recovery which depends on gas composition can be recovered by controlling the conditions of several units, namely heat exchangers, flash vessels, cold separators, fractionators, stabilizers with their reboilers and condensers.

Techno-economics and sensitivity analysis of hybrid process combining carbon molecular sieve membrane and distillation column for propylene/propane separation

The conceptual designs of a carbon molecular sieve (CMS) membrane and a distillation process with heat pump integration were used to evaluate propylene/propane separation system economics. A CMS membrane prepared on a porous alumina hollow fiber was employed to establish the conceptual design of the integrated system. The technologies were evaluated in terms of capital and operating costs and compared to a conventional C3-splitter to elicit the one that minimizes total costs. Different configurations are suggested to satisfy the design specifications of 99.6 wt% product purity and 99% propylene recovery rate. When the heat pump with membrane system was applied in condition of stage cut 0.5, pressure ratio 3, propylene/propane selectivity 28, and propylene permeance 20 GPU, the capital and operating costs decreased by 2.3% and 68.7% compared to distillation only process, respectively. The cost saving variation of the hybrid system was confirmed with membrane specifications such as selectivity and permeance. The simulation results indicated that the heat pump with membrane process is advantageous in terms of both energy and economic savings. A correlation contour between membrane permeance/selectivity and cost saving was developed for the hybrid systems. The findings provide a helpful guide to more economically separate gas mixtures.

Improving the Energy Efficiency for Propane Recovery from Natural Gas using Pinch Technology: A Case Study

Process integration (PI) techniques is an efficient approach to increase the profitability due to reduction in energy, water and raw materials consumption, reduction in greenhouse gas (GHG) emissions, and in waste generation. The PI method, pinch technology is certainly the most widely used in industrial processes. When planning a new plant or revamping an existing plant it is very important to understand and select the right process to minimize capital and operating costs. This research was directed to investigate the reduction of energy consumption in propane recovery units that process natural gas produced from wells existing in the Egyptian western desert fields. The first step was process simulation of the existing gas processing plant using AspenHysys8.3 steady state process simulation program. Next, pinch technology has been adopted in order to achieve minimum hot and cold utilities and save capital cost of the process. Target utilities were calculated using pinch analysis in the Aspen energy analyzer program. Modifications in heat exchanger network could result in savings of 8.3% in hot utility, 6.5% in cold utility of the existing plant and of 46.7% in capital cost for a grass root plant.

CFD Modeling of Methanol to Light Olefins in a Sodalite Membrane Reactor using SAPO-34 Catalyst with In Situ Steam Removal.

In this work, the performance of a sodalite membrane reactor (MR) in the conversion of methanol to olefins (MTO process) was evaluated for ethylene and propylene production with in situ steam removal using 3-dimensional CFD (computational fluid dynamic) technique. Numerical simulation was performed using the commercial CFD package COMSOL Multiphysics 5.3. The finite element method was used to solve the governing equations in the 3- dimensional CFD model for the present work. In the sodalite MR model, a commercial SAPO-34 catalyst in the reaction zone was considered. The influence of key operation parameters, including pressure and temperature on methanol conversion, water recovery, and yields of ethylene, propylene, and water was studied to evaluate the performance of sodalite MR. The local information of component concentration for methanol, ethylene, propylene, and water was obtained by the proposed CFD model. Literature data were applied to validate model results, and a good agreement was attained between the experimental data and predicted results using CFD model. Permeation flux through the sodalite membrane was increased by an increase of reaction temperature, which led to the enhancement of water stream recovered in the permeate side. The CFD modeling results showed that the sodalite MR in the MTO process had higher performance in methanol conversion compared to the fixed-bed reactor (methanol conversion of 97% and 89% at 733 K for sodalite MR and fixed-bed reactor, respectively).

ZIF-8 tubular membrane for propylene purification: Effect of surface curvature and zinc salts on separation performance

A continuous and defect-free ZIF-8 membrane was successfully grown on a positive surface curvature of a porous tubular alumina support that was prepared from zinc nitrate precursor solution at 120 °C for 4 h of synthesis time. The membrane produced the highest propylene permeation of 198 × 10−10 mol⋅m−2⋅s−1⋅Pa−1 and moderate separation factor of 48. Despite its modest level of separation factor, the membrane was able to enrich propylene from 50 vol%. to 98 vol% from a binary feed mixture containing equal flowrate of propylene and propane. The high purity however came with low propylene recovery of merely 5% because there was a trade-off between the separation factor and permeance as a result of an inversed relationship between the two.

Flow synthesis of polycrystalline ZIF-8 membranes on polyvinylidene fluoride hollow fibers for recovery of hydrogen and propylene

It is highly desirable to prepare defect-free ZIF-8 membranes on commercially attractive scalable polymer hollow fibers, especially on the bore side of the fibers, yet quite challenging. Herein, we report a facile synthesis of well-intergrown ZIF-8 membranes on polyvinylidene fluoride (PVDF) microfiltration hollow fibers by a secondary growth method. Surface modification using a strong base promoted high heterogeneous nucleation, resulting in densely packed ZIF-8 seed layers on the hollow fibers. The seed crystals were secondarily grown under a continuous flow of growth solution to form ZIF-8 membranes with thickness of ˜1.2μm. The prepared ZIF-8 membranes achieved high gas permeances, reaching values of 16,344×10−10 mol m-2 s-1Pa-1 for H2 and 197×10−10 mol m-2 s-1Pa-1 for C3H6. The selectivities for H2/CH4, H2/C3H6, H2/C3H8 and C3H6/C3H8 gas pairs were found to be 12, 57, 160 and 15, respectively. We anticipate that the method could potentially be applied to transform commercial PVDF ultrafiltration/microfiltration hollow fibers commonly used for water separation into high quality ZIF-8 membranes for H2 purification and C3H6/C3H8 separation.

Insights into recovery of multi-component shale gas by CO2 injection: A molecular perspective

Understanding the mechanism behind shale gas recovery is of great importance for achieving optimum shale gas productivity. In this work, we use Grand Canonical Monte Carlo (GCMC) simulations to investigate the adsorption and recovery mechanisms of ternary hydrocarbon mixtures comprising methane, ethane and propane in kerogen nanopores. For the adsorption of hydrocarbon mixtures in kerogen slit pores, density distributions of each component are analyzed and the results indicate that densities of methane and ethane in the first adsorption layer increase as pressure increases, while an opposite trend is observed for propane. A stronger confinement effect is observed on the heavier hydrocarbon components, increasing the difficulty of recovery. For the recovery of the multi-component shale gas, we propose a reference recovery route with pressure drawdown and CO2 injection combined and the recovery efficiency is compared to the condition with only pressure drawdown applied. Significant enhancement in recovery ratio for all three components is observed with the CO2 injection and a better performance is shown on heavier components and smaller pores. An increase of 60% and 40% in propane recovery ratio is achieved in the 2-nm and 4-nm kerogen slit pores, respectively. Recovery mechanisms of pressure drawdown and CO2 injection are investigated in detail. The pressure drawdown method recovers methane from the first adsorption layer and middle of slit pore simultaneously, while extracting ethane and propane mainly from the middle of slit pore; the recovery due to CO2 injection mainly takes place in the adsorption layers. Pressure drawdown tends to extract the lighter components and CO2 injection is efficient in the recovery of heavier hydrocarbons. As pore width increases, the recovery ratio of pressure drawdown increases, while that of CO2 injection decreases. Besides, the CO2 sequestration ratio is higher in smaller kerogen slit pores.

Energy efficiency of membrane vs hybrid membrane/cryogenic processes for propane recovery from nitrogen purging vents: A simulation study

When pure propane contained in pipelines or storage tankers has to be flushed out by nitrogen fluxes for maintenance purpose, propane recovery is obviously of interest both for environmental issue and for propane valorization. A low temperature condensation is generally used for that purpose and is attractive because it allows to recover propane under liquid state. However, the energy required is very important to reach a high recovery separation target. An alternate approach can be the combination of a nitrogen or propane permselective membrane with a conventional condensation step to improve the global efficiency of the separation process. The present work has been intended to investigate this approach and evaluate to which extent a hybrid process can bring an added value. This study shows first a map of membrane separation performance of propane over nitrogen from data of the open literature. Interestingly it shows that either N2-selective or conversely, propane-selective membranes can be used and also that propane–selective membrane will require higher area for atmospheric down-stream pressures (1 bar) compared to down-streams kept at lower pressures (0.1 bar). The selection of the most nitrogen and propane selective membrane is used in order to simulate hybrid processes where separations performances (purity of the propane condensed versus energy required) are compared to the baseline cryogenic standalone process. For low propane contents in the feed mixture (xin,C3H8 = 0.5 and 5% mol/mol), it is shown that the use of a propane selective membrane module with a vacuum system seems to be the most energy efficient process while reaching a high purity (>98%). Based on rigorous process simulations, other hybrid processes cases were performed considering SSZ-13 zeolite membranes and the different separation performances are discussed. It is shown that a membrane/cryogenic process can indeed be less energy demanding to recover propane from N2-vents. However, according to the recovery target the choice of the membrane type can vary from an organic to a zeolite membrane.

Separation of the propane propylene mixture with high recovery by a dual PSA process

Propylene is a very important raw material in the petrochemical industry. A key step in its production is propane/propylene separation, where energy consumption and the degree of propylene recovery achieved have a strong impact on the economy of the process. A Dual PSA process has been designed for the separation of a 50:50 molar propane/propylene mixture using zeolite 13X as adsorbent. Kinetic and equilibrium adsorption parameters reported in the literature (Da Silva, F.A., Rodrigues A.E., 2001. AIChE J. 47, 341–57) have been used. The process can produce polymer-grade propylene (purity > 99.5%) with recovery higher than 99.5%, which is above the recovery achieved in other PSA processes studied in the literature for an equimolar propane/propylene mixture. Energy consumption is 38% lower than required by conventional distillation.