Maximum Allowable Pressure Research Articles

Deriving guidelines for the design of plate evaporators in heat pumps using zeotropic mixtures

This paper presents a derivation of design guidelines for plate heat exchangers used for evaporation of zeotropic mixtures in heat pumps. A mapping of combined heat exchanger and cycle calculations for different combinations of geometrical parameters and working fluids allowed estimating the trade-off between heat transfer area and pressure drops on the thermodynamic and economic performance indicators of the cycle. Compressor running costs constituted the largest cost share, and increased due to a steep decrease of the heat pump coefficient of performance at high refrigerant pressure drops. It was found that the pressure drop limit leading to infeasible designs was dependent on the working fluid, thereby making it impossible to define a guideline based on maximum allowable pressure drops. It was found that economically feasible designs could be obtained by correlating the vapour Reynolds number and the Bond number at the evaporator inlet as ReV−0.42Bd0.26≈0.040. The use of the proposed guideline was illustrated for the mixture Propane/Iso-Pentane (0.5/0.5), leading to evaporator designs with net present values deviating maximum −4.4% from the best value found in the mapping. The presented methodology can be applied in different scenarios to develop similar guidelines, thereby decreasing the cost of combined cycle and component optimizations.

Integration of commercial CO2 capture plant with primary reformer stack of ammonia plant

The safety of primary reformers is essential to safe operation of large-scale petrochemical processes, especially when carbon dioxide is going to be recovered from an ammonia plant. In this study, a preliminary assessment is made to model an industrial stack as the stack gases are introduced into CO2 capture plant, during ammonia production. A CFD model was first developed in the absence of a commercial carbon dioxide recovery (CDR) unit to validate the model against industrial data under normal operation. At full capacity of the ammonia plan, the results provided by the CFD model match the measurement results well within about 3.87% margin of relative error. The calibrated model was then applied in combination with post-combustion, as part of the process, to verify the process safety constraints in reformer furnace. The effect of starting up and shutting down of CDR plant was explored in the event of emergency operation. From an operational view, in the event of startup or unplanned failure of the CO2 capture plant, the pressure fluctuations do not exceed the maximum allowable pressure of the firebox. Upon reaching the required operating conditions, both subsystems can be integrated operationally to continue production safely.

The potential for avoiding hydrogen release from cryogenic pressure vessels after vacuum insulation failure

This paper presents an analysis of vacuum insulation failure in an automotive cryogenic pressure vessel (also known as cryo-compressed vessel) storing hydrogen. Vacuum insulation failure increases heat transfer into cryogenic vessels by about a factor of 100, potentially leading to rapid pressurization and venting of the cryogen to avoid exceeding maximum allowable working pressure (MAWP). Hydrogen release to the environment may be dangerous, especially if the vehicle is located in a closed space (e.g. a garage or tunnel) at the moment of insulation failure. We therefore consider utilization of the hydrogen in the vehicle fuel cell and dissipation of the electricity by operating vehicle accessories or electric resistances as an alternative to releasing hydrogen to the environment. We consider two strategies: initiating hydrogen extraction immediately after vacuum insulation failure or waiting until maximum operating pressure is reached before extraction. The results indicate that cryogenic pressure vessels have thermodynamic advantages that enable slowing down hydrogen release to moderate levels that can be consumed in the fuel cell and dissipated in vehicle accessories supplemented by electric resistances, even in the worst case when the insulation fails at the moment when the vessel stores hydrogen near its maximum density (70 g/L at 300 bar). The two proposed strategies are therefore feasible, and the best alternative can be chosen based on economic and/or implementation constraints.

Optimal design of microtube recuperators for an indirect supercritical carbon dioxide recompression closed Brayton cycle

This paper presents a baseline design and optimization approach developed in Aspen Custom Modeler (ACM) for microtube shell-and-tube exchangers (MSTEs) used for high- and low-temperature recuperation in a 10 MWe indirect supercritical carbon dioxide (sCO2) recompression closed Brayton cycle (RCBC). The MSTE-type recuperators are designed using one-dimensional models with thermal-hydraulic correlations appropriate for sCO2 and properties models that capture considerable nonlinear changes in CO2 properties near the critical and pseudo-critical points. Using the successive quadratic programming (SQP) algorithm in ACM, optimal recuperator designs are obtained for either custom or industry-standard microtubes considering constraints based on current advanced manufacturing techniques. The three decision variables are the number of tubes, tube pitch-to-diameter ratio, and tube diameter. Five different objective functions based on different key design measures are considered: minimization of total heat transfer area, heat exchanger volume, metal weight, thermal residence time, and maximization of compactness. Sensitivities studies indicate the constraint on the maximum number of tubes per shell does affect the number of parallel heat exchanger trains but not the tube selection, total number of tubes, tube length and other key design measures in the final optimal design when considering industry-standard tubes. In this study, the optimally designed high- and low-temperature recuperators have 47,000 3/32 in. tubes and 63,000 1/16 in. tubes, respectively. In addition, sensitivities to the design temperature approach and maximum allowable pressure drop are studied, since these specifications significantly impact the optimal design of the recuperators as well as the thermal efficiency and the economic performance of the entire sCO2 Brayton cycle.

Finding a criterion for the pressure loss of energy recovery exchangers in HVAC systems from thermodynamic and economic points of view

Heat recovery devices can help ventilation systems conserve energy; However, they cause a pressure drop in the system, and hence the system incurs an electricity consumption. In the present paper, the maximum allowable pressure drop of the recovery units is achieved from thermodynamic and economic points of view. The novelty of the research is that, unlike the existing criterion which does not differ for different cities, the introduced criteria can be calculated for each city with individual weather, economic, power plants, and energy conditions. Although the methods presented to calculate the criteria consider a broad range of effective parameters, there is no need to use complex energy simulation methods. Moreover, for each city, four types of criteria are introduced, which allows the city authorities to choose the best ones according to their city conditions, and then calculate the chosen criteria by the data of the city. In order to gain the criteria, modified enthalpy-hours and bin method variables are introduced to calculate sensible and latent energy consumption due to ventilation. The criteria are numerically calculated for Kerman city in Iran, and the results show that the recovery type and the chosen viewpoint has a considerable effect on the allowable pressure drop. The sensitivity of the results to different variables is analyzed in the end.

Optimal design of the first stage of the plate-fin heat exchanger for the EAST cryogenic system

The size of the heat exchanger is an important factor determining the dimensions of the cold box in helium cryogenic systems. In this paper, a counter-flow multi-stream plate-fin heat exchanger is optimized by means of a spatial interpolation method coupled with a hybrid genetic algorithm. Compared with empirical correlations, this spatial interpolation algorithm based on a kriging model can be adopted to more precisely predict the Colburn heat transfer factors and Fanning friction factors of offset-strip fins. Moreover, strict computational fluid dynamics simulations can be carried out to predict the heat transfer and friction performance in the absence of reliable experimental data. Within the constraints of heat exchange requirements, maximum allowable pressure drop, existing manufacturing techniques and structural strength, a mathematical model of an optimized design with discrete and continuous variables based on a hybrid genetic algorithm is established in order to minimize the volume. The results show that for the first-stage heat exchanger in the EAST refrigerator, the structural size could be decreased from the original 2.200 × 0.600 × 0.627 (m3) to the optimized 1.854 × 0.420 × 0.340 (m3), with a large reduction in volume. The current work demonstrates that the proposed method could be a useful tool to achieve optimization in an actual engineering project during the practical design process.

Estimation of the maximum allowable drilling mud pressure for a horizontal directional drilling borehole in fractured rock mass

The drilling mud loss risk is a major problem for horizontal directional drilling (HDD) projects when it was drilling in fractured rock stratum. The existing theoretical calculation methods for the maximum allowable drilling mud pressure in HDD borehole are particularly designed for soils, so they are not suitable when rocks are encountered. The maximum allowable drilling mud pressure was analyzed in this study for a fracture zone of a maxi-HDD project crossing Yangtze River. The geotechnical investigation disclosed multiple layers of soils and rocks: the upper part two sand layers and the lower part one sandstone layer. The fracture zone in the sandstone layer was investigated by digital panoramic borehole camera technique, so that the detailed fracture orientations and locations can be identified. The maximum drilling mud pressure for the upper part two sand layers was calculated using Delft equation. At the same time, the evolution of drilling mud pressure in the fracture zone was studied using numerical modeling method. Combing with the calculation results of both Delft equation and numerical modeling, the maximum allowable mud pressure at the fracture zone of the HDD borehole was obtained. The numerical modeling found that the persistent fracture system in the fracture rock mass has very low resistance to the drilling mud pressure propagation, so a low drilling mud pressure needs to be used when it was drilling/reaming in the fracture zone. The effects of fracture aperture, the drilling mud viscosity, and fracture roughness on the mud pressure evolution were also analyzed.

Laboratory measurements of slippage and inertial factors in carbonate porous media: A case study

Two important issues for accurate modeling of gas reservoir performance are the gas slippage and the inertia flow within porous media. Depending on the flow condition, these factors can make the gas permeability differ from the true (liquid) permeability. Nevertheless, since the gas flow tests are cheaper and less time consuming than the liquid flow tests, a reservoir engineer may choose to estimate the true (liquid) absolute permeability from the results of a single gas permeability test utilizing a valid empirical correlation. Although many such correlations exist in the literature, most of them have been developed for unconsolidated porous media or sandstone core samples. Therefore, using them for a specific formation will result in erroneous predictions.This paper is presented in three parts. In the first part, an empirical equation is developed to estimate the gas slippage factor using the results of laboratory measurements on 49 samples of Iranian carbonate reservoirs of Kangan and Dalan. In the second part, a correlation is developed to estimate the inertia factor for the samples. In the last part of the paper, an equation is derived to estimate maximum allowable pressure drop per length to maintain the laminar (Darcy) flow regime in the samples.The developed models in the first and the second parts of the current paper match the experimental data more accurately than the popular existing correlations. The derived equation in the last part is applicable in proper design of gas flow tests, where a laminar flow must be maintained in porous media.

Applications of high-resolution recycling liquid chromatography: From small to large molecules

A twin-column recycling separation process (TCRSP) is assembled and used to generate higher speed and/or higher resolution levels than those of the usual non-recycling process at the same back pressure. It enables the users to solve very challenging separation problems caused by too small selectivity factors and/or too low column efficiencies. The relative gain in speed-resolution performance increases with increasing the number of cycles in the TCRSP, decreasing the maximum allowable pressure imposed by the LC system, decreasing the column permeability, and with reducing the separation speed. TCRSP is then particularly attractive for conventional LC systems (5000psi maximum) and columns packed with sub-2μm to 3.5μm particles. The performance of the real TCRSP was compared to that of the ideal TCRSP for which the retention factor is strictly pressure-independent. A broad range of separation problems encountered in conventional non-recycling chromatography can be easily solved by using a TCRSP assembly based on two 15cm long columns. Under adsorption conditions, the TCRSP enables the full baseline separation of polycyclic aromatic hydrocarbon (PAH) isomers (benzo[a]anthracene and chrysene) on a 3.5μm XSelect-HSS T3 phase, the complete or improved resolution of racemic mixtures (4-phenylbutanol and bromacil) using the same 2.5μm cellulose-1 chiral stationary phase, and the full resolution of isotopic compounds (benzene/1,3,5-benzene-d3/benzene-d6) on a 2.7μm Cortecs-C18 phase. Under non-adsorption conditions or in size-exclusion chromatography (SEC), the fractionation of a polystyrene standard mixture (molecular weights of 35, 66, 130, 277, 552, 1210, and 2500kDa) was completed after only 8 cycles on a 1.7μm BEH 200Åphase. Similarly, a mixture of intact proteins with molecular weights of 16.7, 66.4, 150, 660, and 1320kDa was fully resolved on a 2.5μm BEH 450Åphase after only 6 cycles. Finally, TCRSP enables the complete separation of a few high-molecular-weight species (monoclonal antibody aggregates, small relative abundance of 1 for 250) from the intact monomeric monoclonal antibody (Vectibix).

Fitness for service assessment of a pressure vessel subjected to fire damage in a refinery unit

Abstract The fire-damaged pressure vessel reactor, evaluated in this study, was a cylindrical vessel with design conditions of 460 psig (3.17 MPa) at 413 °C. The fitness for service (FFS) of the fire-damaged pressure vessel was assessed according to API 579-1/ASME FFS-1. First, the maximum temperature during the fire accident was determined based on deterioration of outer protective layer. Then, the possible damage was examined by hardness test, in-situ field metallography and metallographic replicas. Grain growth and spheroidized pearlite were observed in the base metal at the inner surface of the vessel. Outer surface of the vessel showed ferritic microstructure with smaller grain size as compared to the inner surface. Decarburizing and carbide formation were also visible at the outer surface. The lower hardness of the base metal at both sides of the vessel was compared to the standard value and related to the microstructure evolution during high temperature/fire exposure condition. The results of the FFS evaluation indicated that the vessel is not suitable for the current design conditions, and therefore a new maximum allowable working pressure was determined.

Analytical Approach for Modeling of Multi Well CO2 Injection

Disposal of carbon dioxide (CO2) into underground geological formations is considered a viable strategy for the mitigation of global warming. It aims to reduce greenhouse gases emitted from point sources such as power plants. In order to select and evaluate a potential storage formation, many reservoir properties such as porosity, permeability, lateral and vertical extents, and a variety of residual fluid properties are considered. Injection design, which includes the placement of injectors and their flow rates, should be chosen to optimize injection capacity. One of the most important considerations to be addressed during design stage of sequestration is evaluation of pressure behaviour inside the reservoir during and after injection as the sequestered CO2 increases the pressure within the formation. In order to maintain the integrity of the reservoir the pressure needs to be maintained below the fracture pressure, typically at least 10% below. Thus evaluation of reservoir pressure is essential to ensure the reservoir remains under the maximum allowable pressure while sequestering the maximum amount of CO2 for long term storage in the reservoir. The optimal injection rates within a multi well injection site occur when the bottom-hole pressure at each injection site is at the maximum allowable pressure. In this study we present an analytical approach for modeling the pressure evolution during multi well CO2 injection into saline aquifers and using the model modify the injection rates to optimize injection capacity within a formation. We show that this optimization procedure significantly increases the capacity of formation as opposed to using the same injection rate at each wellbore.

Preliminary Understanding of CO2 Sequestration and Enhanced Methane Recovery in Raniganj Coalfield of India by Reservoir Simulation

India has a vast reserve of coal (∼ 7% of the world's total proved reserve) and is the third largest producer in the world. Almost 70% of the country's electrical power comes from the coal-fired thermal power plants. A few coalbed methane (CBM) projects have also commenced operations in the central and eastern parts of the country. However, CO2 sequestration especially in geological formations is still at conceptual stage in India. Raniganj coalfield, located in the eastern states of West Bengal of Jharkhand is a repository of large reserves of high-volatile bituminous coals, where both mining and CBM operations are present. A number of coal-based thermal power plants are also located in the area, making this one of the most suitable areas for starting a carbon capture and storage (CCS) pilot project.CCS in unmineable coal seams arguably has the advantage of commercial success through potential release of additional methane when injected CO2 adsorbs into the coal seams, the process known as enhanced coalbed methane (ECBM) recovery. However, a significant concern lies in the loss of injectivity due to reduction in permeability by coal matrix swelling with CO2 adsorption although this effect can be partially be offset with ‘huff and puff’ scheme of cyclic CO2 injection followed by extraction of the released methane.The paper discusses the results of a numerical simulation study carried out with GEM compositional reservoir simulator to evaluate the effects of uncertainties in various reservoir parameters on the overall volume of CO2 storage and additional methane recovery before planning a pilot project in the Raniganj coalfield. A 3-m thick seam at 600 m depth was considered for fluid flow simulation study. While some information on the reservoir setting was obtained through literature and personal communication with the CBM operators, the rest of the information was derived through laboratory studies. The reservoir parameters considered for the study are injection pressure, adsorption capacity, permeability, cleat porosity, sorption time, and initial gas saturation. A 160-acre drainage area with 5-spot vertical well pattern was considered with one central injector and four producers on four corners of the study area.The maximum allowable injection pressure was estimated to be ∼ 850 psi (5856kPa) at the reservoir setting. The injection pressure was varied from 300 psi (2067kPa) to 850 psi (5856kPa) in the simulation and 600 psi (4134kPa) was found to be the optimum injection pressure. A number of adsorption isotherms on coals of Raniganj coalfield were established in the laboratory. The variations in the adsorption parameters observed through the isotherms were considered as uncertainty in the storage capacities. Significant variations were observed due to the variation in adsorption isotherms both for CO2 storage and additional methane recovery. Fracture permeability was varied from 3 md to 40 md, which is the range of permeability observed in the coalfield. The results of simulation indicate a strong influence of permeability on the CO2 storage and ECBM recovery. In the absence of specific information on sorption time, it was theoretically varied from a very fast-desorbing coal (sorption time of 1 day) to an extremely slow-desorbing coal (sorption time 200 days). Since rate of desorption from the coal matrix and fracture permeability are rate-control parameters, for each sorption time a low and a high permeability situation were considered. Fluid flow simulation study shows that variation in sorption time has no significant effect for a low permeability situation while some marginal effect in high permeability situation. Cleat porosity was varied from 0.5% to 1.5%. Within this range of porosities, enhanced methane recovery varied from 70% to 85% relative to the primary recovery but the volume of stored CO2 did not vary significantly. Lastly, the initial gas saturation was varied from 70% to almost 100% and both the CO2 sequestered volume and additional methane recovery were found to increase substantially.

Ideal versus real automated twin column recycling chromatography process

The full baseline separation of two compounds (selectivity factors α<1.03) is either impractical (too long analysis times) or even impossible when using a single column of any length given the pressure limitations of current LC instruments. The maximum efficiency is that of an infinitely long column operated at infinitely small flow rates. It is determined by the maximum allowable system pressure, the column permeability (particle size), the viscosity of the eluent, and the intensity of the effective diffusivity of the analytes along the column.Alternatively, the twin-column recycling separation process (TCRSP) can overcome the efficiency limit of the single-column approach. In the TCRSP, the sample mixture may be transferred from one to a second (twin) column until its band has spread over one column length. Basic theory of chromatography is used to confirm that the speed-resolution performance of the TCRSP is intrinsically superior to that of the single-column process. This advantage is illustrated in this work by developing an automated TCRSP for the challenging separation of two polycyclic aromatic hydrocarbon (PAH) isomers (benzo[a]anthracene and chrysene) in the reversed-phase retention mode at pressure smaller than 5000psi. The columns used are the 3.0mm×150mm column packed with 3.5μm XBridge BEH-C18 material (α=1.010) and the 3.0mm or 4.6mm×150mm columns packed with the same 3.5μm XSelect HSST3 material (α=1.025). The isocratic mobile phase is an acetonitrile–water mixture (80/20, v/v). Remarkably, significant differences are observed between the predicted retention times and efficiencies of the ideal TCRSP (given by the number of cycles multiplied by the retention time and efficiency of one column) and those of the real TCRSP. The fundamental explanation lies in the pressure-dependent retention of these PAHs or in the change of their partial molar volume as they are transferred from the mobile to the stationary phase. A revisited retention and efficiency model is then built to predict the actual performance of real TCRSPs. The experimental and calculated resolution data are found in very good agreement for a change, Δvm=−10cm3/mol, of the partial molar volume of the two PAH isomers upon transfer from the acetonitrile–water eluent mixture to the silica-C18 stationary phase.

Determination of the fracture pressure from CO2 injection time-series datasets

Successful operation of CO2 storage projects requires careful management of injection pressure to ensure that the integrity of the cap rock and other containment units is not compromised by mechanical failure. Injection of CO2 will lead to some increase in the pore pressure of the target storage formation and the project design will include some expected range of acceptable pressure variations required to achieve sufficient injectivity and to avoid loss of formation integrity. Accurate determination of the formation fracture pressures is a key factor controlling the maximum allowable injection pressure during operations. In this study we review the three main approaches for determining fracture pressure: (a) theoretical methods, (b) use of formation well-test data and (c) analysis of injection data during injection. While theoretical methods are valuable for early planning of projects, predictions based on formation well-test data are generally used immediately prior to and during injection operations. Using example site data, we show how careful analysis of wellhead pressure and rate data during injection operations may be used to optimize the injection plan using the actual in situ conditions in the rock formation around the injection well and for the specific properties of the injection fluid. Using injection pressure time-series datasets over an extended period of time allows improved accuracy in the estimation of the fracture pressure limits and an appreciation of their variation over a larger volume of the formation than can be estimated from well tests.

Treatment on oil/water gel deposition behavior in non-heating gathering and transporting process with polymer flooding wells

Against a background of crude oil shortage and low-carbon economy, optimization and simplification of oil–gas gathering and transporting play an indispensable role in efficient development of oilfield. Profit from the high efficient utilization of the produced liquid self-energy, single-pipe non-heating gathering and transporting process has been recognized in polymer flooding wells of Daqing oilfield (China). However, it is also facing the challenges of deposition, partial blockage, high wellhead pressure, production fluctuation and environment management. A field investigation of the application for the non-heating process and the variation of polymer flooding wellhead pressure were recently carried out. The flow patterns of the oil, water and gas mixture in single-pipe process were identified, and the locations where the gel deposition was most likely to occur were estimated. Deposition inhibitions and removal processes were practiced, and the operation parameters under different working conditions were optimized. The results indicated that single-pipe non-heating process could reduce 20% of the investment and 30% of the running cost and could also make the wellhead pressure of some wells exceed the maximum allowable operating pressure of oil gathering pipelines. There appears to be a proportional relationship among water content, flow rate, residual polymer concentration and gel deposition behavior in a certain range of gathering radius. The gel deposition rate of the produced liquid with polymer concentration of higher than 600 mg/L and the water content of 90.5% reached 0.1154 mm/h in the coldest climate under the normal flow rate of 85 t/d, and the theoretical pigging period was <10 days. Gelation nucleation which was related to emulsification was induced by the transition and coexistence of separated flow and dispersed flow in non-heating gathering pipelines. The main deposition located on the beginning of pipelines, manifold, valve and elbow, and wellhead pressure of 350 psi was created in the test period of 20 days. Although using chemical inhibition method could still obtain a drag reduction rate of more than 25% under crude oil gelation temperature, the fact of the centralization disability of wellhead dosing facilities and the potential threat of chemical inhibitors to the environment could not be ignored. The noticeable energy consumption and potential risks of pipeline restarting may be encountered using facilities improvement and sphere pigging operation in gel deposition behavior treatment. A relation schema which could be used to predict deposition rate and extract thermal flush period according to the actual working condition was established. The successful application of the non-heating gathering and transporting process combated the traditional view that heat tracing is essential for maintaining the surface process in extremely cold area. Furthermore, the results contributed to the existing literature in establishing subsurface and surface parts integration idea for a green field development and accelerate further application of non-heating gathering and transporting process.

Water-Isolating Capacity of an Inclined Coal Seam Floor Based on the Theory of Water-Resistant Key Strata

A model of an inclined coal seam floor with linearly increasing water pressure was developed based on theories of ground pressure and key strata. The stability metrics of the water-resistant key strata in the inclined coal seam was deduced using Mohr–Coulomb yield criterion. Five principle factors were selected: the distance that the workface had advanced, the tilted length of workface, the thickness and pitch of the water- resistant key strata, and the elasticity modulus. A sensitivity analysis was then conducted using an orthogonal design. The thickness of the water-resistant key strata was the most important factor, with a 44.8% ranking, followed by the distance that the workface had advanced at 34.4%. The influence of the elasticity modulus, pitch, and tilted length of the workface, were 9.3, 5.8, and 5.7%, respectively. The maximum water pressure possibly tolerated by the inclined aquiclude were found to rise with the increasing load of the caved overburden, and decrease with the increasing workface initial or periodic weighting distance, workface length, and pitch of the water-resistant key strata. A parabolic relationship exists between the maximum allowable water pressure and thickness of the key aquiclude. Water-resistant key strata located in the lower part of the confining layer offers better protection from floor water inrush. These findings provide an important theoretical basis to determine the potential of water inrush from an inclined coal seam when mining above confined aquifers.

Новый способ определения максимально допустимой депрессии на пласт

Новый способ определения максимально допустимой депрессии на пласт

A methodology for designing maximum allowable wellhead pressure for CO2 injection: application to the Shenhua CCS demonstration project, China

AbstractMaximum allowable wellhead pressure is an effective indicator for both site safety control and government regulation of CO2 geological storage projects. In many carbon capture and storage (CCS) projects, the injection rate may also be set as an obligatory objective. For such a problem of multi‐objective design, no systematic design methodology has been opened in the publicly available literature. Although a numerical simulator can be employed to obtain the wellhead pressure through a series of trial processes of calculations, this will usually need more model parameters and a large number of computations, especially when there are more reservoirs. In this study, an extensible methodological framework for designing a maximum allowable wellhead pressure for CO2 injection was developed. The methodology is based on a thermal‐hydraulic coupling model of wellbore and reservoir flows suitable for arbitrary number of reservoirs. The new methodology can automatically accommodate multiple design objectives, such as site stability and total injection rate. As a result of explicit solutions employed, the methodology has the advantage of less computation and high speed. Using this method, we recommended a maximum allowable wellhead pressure of 13.0 MPa for the Shenhua CCS demonstration project in China, which has been accepted by the expert committee of the project. The large amount of verification data and four‐year successful injections in the project have proved the effectiveness of the new method. © 2016 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

High-performance strategy of a simulated moving bed chromatography by simultaneous control of product and feed streams under maximum allowable pressure drop

In this study, a novel operating strategy was developed to improve the separation performance of simulated moving bed (SMB) chromatography by the simultaneous control of product outlet streams and feed inlet stream (SimCon). The SimCon operation can achieve a high separation performance without exceeding the maximum allowable pressure drop in an SMB system. The SimCon operation consisted of three steps within a single switching period: the initial, middle, and last steps. The extract port and feed-inlet port were closed at the initial step, but the raffinate port was closed at the last step. Therefore, in the SimCon strategy, we introduce two additional operating variables in a switching period, namely the middle time and middle length. In the SimCon operation, the middle step is a key factor to achieving a good separation performance because concentration profiles can be well controlled by two new middle-step variables. The SimCon operation showed outstanding results compared with those of the corresponding conventional SMB and other stream-control strategies in terms of purity, recovery, productivity, and eluent consumption. Because the SimCon operation can be operated with smaller flow and pressure fluctuations than other flow-rate-control strategies and improves the column efficiency, it is expected that the strategy can be practically adapted to real SMB processes with a good separation performance.

Estimation of Maximum Annular Pressure during HDD in Noncohesive Soils

AbstractThis study investigated the effectiveness of estimating the maximum allowable annular pressure during horizontal directional drilling (HDD) in noncohesive soils by using two theoretical cavity-expansion solutions (small strain and large strain); several laboratory and field tests were used for verification. The results indicated that the measurements were overestimated when using the plastic radius equal to two-thirds of the overburden depth and underestimated when using the hoop strain equal to 2%. Although the calculated limit pressures based on the two cavity-expansion solutions were higher than the measured failure pressures, a high correlation (R2 = 0.96) existed between the measurements and the calculations based on the large-strain cavity-expansion solution. This correlation may be used to estimate the maximum allowable annular pressure during HDD in noncohesive soils, provided that further validation is conducted with more field data for deep depths rather than shallow depths.