Absorber Section Research Articles

Study Finds Compact Carbon-Capture Modules Feasible on Offshore Production Facilities

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 34825, “Implementation of Compact Carbon-Capture Modules on Offshore Hydrocarbon Production Facilities,” by Jaime H. Tan and Rizal A. Hassan, Technip Energies, and Umberto Cornelis, KANFA, et al. The paper has not been peer reviewed. Copyright 2024 Offshore Technology Conference. _ Carbon capture and storage has been implemented onshore successfully by different industries, including utilities and waste treatment, to capture CO2 from flue gases after the combustion of fossil fuels. Duplicating this success for offshore hydrocarbon processing facilities can be challenging because of deck-space constraints and marine environmental conditions. The complete paper describes the development of a compact carbon-capture module design for post-combustion carbon capture and its potential implementation on typical offshore hydrocarbon production facilities. Solvent Absorption Technology for Post-Combustion Carbon Capture The process technology at the core of the compact carbon-capture module is based on a solvent-absorption technique and a proprietary amine-based solvent. First, feed gas is quenched and saturated in a circulated water prescrubber. The gas contacts the lean amine solution in a countercurrent mass-transfer packed absorption column, and CO2 is absorbed while the treated gas exits to the atmosphere. Midway through the column, partially loaded amine is removed from the tower, cooled, and reintroduced over a layer of mass-transfer packing. CO2-rich amine from the absorption column is pumped through a lean-rich amine heat exchanger and then to the regeneration column. The rising, low-pressure saturated steam in the column regenerates the lean amine solution. CO2 is recovered as a pure, water-saturated product. Lean amine is pumped from the stripper reboiler to the absorption column for reuse in capturing CO2. Finally, the CO2 is directed to byproduct-management systems. The pure CO2 streams produced from the system may be sequestrated or used for applications such as enhanced oil recovery. Design of Offshore Carbon-Capture Modules For offshore applications, the carbon-capture modules must be more compact and lighter compared with carbon-capture systems developed for onshore applications. The absorber column is the critical component of the carbon-capture module because of its weight, footprint, and height. To reduce the overall height of the absorber for offshore application, an innovative configuration has been adopted: The bottom section of the absorber is placed on top of the prescrubber/direct contact cooler (DCC), and the top section of the absorber and the wash-water section comprise the second column. With this arrangement, the maximum height of the columns is limited to approximately 25 m. Because the lower absorber section is placed on top of the prescrubber/DCC, the in-between chimney tray is designed to be totally leakage-free to avoid losses of amines into the DCC water loop. A patent-pending compact absorber column design has been developed. The column wall construction will be a part of the overall module support structure, with cantilevered platforms for supporting carbon-capture equipment. The equipment for compression, injection, and treatment of CO2 is placed on a separate submodule. This module design benefits from footprint and weight savings of potentially more than 20% compared with typical cylindrical absorber column designs.

Effect of spring-wire turbulators with different shapes on heat transfer improvement of solar air heaters; A numerical simulation

This study evaluates the heat transfer and performance characteristics of a solar air heater (SAH) equipped with spring-wire turbulators using a 3D verified CFD simulation process. Five different shapes of spring-wire (as shown in the graphical abstract) are investigated and compared to a flat SAH (without turbulator). The effects of helical diameter, pitch, and wire diameter on the performance of the system are comprehensively analyzed for all five mentioned geometries. The results reveal that the turbulator significantly enhances the thermal efficiency of the SAH within the absorber section. Rectangular cross section shape shows higher enhanced Nu number compared to the other cross section shapes. However, considering both heat transfer and pressure drop, the circular turbulator exhibits the optimal performance. Larger helical diameter, helical pitch and wire diameter, augments, decreases and increases the value of Nu/Nus respectively. Generally, higher increased Nu number also shows higher pumping power as well and that is why thermohydraulic performance parameter (THPP) is considered as well. Larger helical diameter, and helical pitch decreases and increases thermohydraulic performance respectively. For instance, the circular turbulator's THPP rises by approximately 17.5% as the pitch increases from 50 mm to 250 mm. However, the impact of wire diameter on THPP does not show a unified curve trend and depends on the shape of the turbulator. This study is remarkably useful for optimizing the performance of SAHs with turbulators, paving the way for enhanced device efficiency.

Enhancing the performance of open geothermal tunnelwater systems by heat absorbers

The symbiotic use of underground infrastructure among the improvement of transport routes and the generation of geothermal power, is increasingly gaining momentum. Geothermal systems can be divided into open and closed systems, which differ from each other by the circumstance that closed systems have a closed circuit and open systems do not. For the application of geothermally closed tunnel systems, elegant solutions have been developed, while geothermally open tunnel systems are still dictated by the characteristics of the water entering the tunnel. In order to address this issue, concepts for tunnels under design as well as existing tunnels, were developed. The concepts allow the temperature of the inflowing water to be risen, and thereby increasing the geothermal power. The presented approach is based on the channeling of cold tunnel water inflows through absorber sections in areas of high overburden to supply them with additional energy before diverting them back into the drainage system. In order to obtain indications on the effectiveness as well as on the sensitivity of the components and influencing parameters, numerical models were created and subsequently compared, since no empirical data are available. The results show that it is possible to enhance the geothermal performance, but with decreasing efficiency over time.

High-energy picosecond pulses with a single spatial mode from a passively mode-locked, broad-area semiconductor laser

We present a mode-locked semiconductor laser oscillator that emits few picosecond pulses (5-8ps at a repetition rate of 379MHz and wavelength of 1064nm) with record peak power (112W) and pulse energy (0.5nJ) directly out of the oscillator (with no amplifier). To achieve this high power performance we employ a high-current broad-area, spatially multi-mode diode amplifier (0.3×5mm), placed in an external cavity that enforces oscillation in a single spatial mode. Consequently, the brightness of the beam is near-ideal (M2 = 1.3). Mode locking is achieved by dividing the large diode chip (edge emitter) into two sections with independent electrical control: one large section for gain and another small section for a saturable absorber. Precise tuning of the reverse voltage on the absorber section allows to tune the saturation level and recovery time of the absorber, providing a convenient knob to optimize the mode-locking performance for various cavity conditions.

Spiking information processing in a single photonic spiking neuron chip with double integrated electronic dendrites

Dendrites, branches of neurons that transmit signals between synapses and soma, play a vital role in spiking information processing, such as nonlinear integration of excitatory and inhibitory stimuli. However, the investigation of nonlinear integration of dendrites in photonic neurons and the fabrication of photonic neurons including dendritic nonlinear integration in photonic spiking neural networks (SNNs) remain open problems. Here, we fabricate and integrate two dendrites and one soma in a single Fabry–Perot laser with an embedded saturable absorber (FP-SA) neuron to achieve nonlinear integration of excitatory and inhibitory stimuli. Note that the two intrinsic electrodes of the gain section and saturable absorber (SA) section in the FP-SA neuron are defined as two dendrites for two ports of stimuli reception, with one electronic dendrite receiving excitatory stimulus and the other receiving inhibitory stimulus. The stimuli received by two electronic dendrites are integrated nonlinearly in a single FP-SA neuron, which generates spikes for photonic SNNs. The properties of frequency encoding and spatiotemporal encoding are investigated experimentally in a single FP-SA neuron with two electronic dendrites. For SNNs equipped with FP-SA neurons, the range of weights between presynaptic neurons and postsynaptic neurons is varied from negative to positive values by biasing the gain and SA sections of FP-SA neurons. Compared with SNN with all-positive weights realized by only biasing the gain section of photonic neurons, the recognition accuracy of Iris flower data is improved numerically in SNN consisting of FP-SA neurons. The results show great potential for multi-functional integrated photonic SNN chips.

Anesthesia and the Classics: Essays on Avatars of Professional Values

Anesthesia and the Classics: Essays on Avatars of Professional Values

Measurements and Modeling of a Monolithically Integrated Self-Spiking Two-Section Laser in InP

The self-spiking behavior of an integrated saturable absorber and gain section laser fabricated in an InP technology platform is analyzed. The gain, absorber and intensity dynamics are first inspected using the normalized Yamada model. This model shows excitable behavior as well as the relative refractory period, both of which are also present in biological neurons. Measurements of a two-section laser show irregular spike generation on the millisecond timescale, with a saturable absorber voltage controlled spike density. From our simulations, and from the quasi-random character and millisecond timescale at which these pulses occur, we conclude the laser is triggered by noise, an important characteristic in the operation of biological neurons. Simulations of the laser around the excitability threshold using a newly proposed model with an optical noise term show qualitatively similar self-spiking behavior as measured.

Numerical analysis of the effectiveness of a unique roughened surface solar air heater

ABSTRACT The main goal of this study is to enhance the functionality of the solar air heater by adding unique roughened surfaces to the absorber section that disrupt the sluggish sub-layer. The roughened surfaces are created so that the depth of roughened surface’s dimension is constant for all the cases; there will not be any pressure difference lost. Initially, a square roughened surface is considered for the primary plain tube solar air heater. Later, the remaining roughened surfaces are created by removing some triangular portions from the basic square rib surfaces. The primary intention of creating surfaces like this is that the sharp edges facing the upwind stream disturb the viscous sub-layer at a greater level than the squared rib roughened surfaces. Using a computational fluid dynamics tool, this research problem has been investigated numerically by computing formula that controls the fluid flow with the RNG k-ε turbulence model. The functionality of solar-powered air heaters has been examined at different Reynolds numbers by studying temperature, turbulence, and the Nusselt number. Based on the overall comparison of the numerical results for the different roughened surfaces, Case 4 offers superior heat transmission performance compared to the simple tube solar air heater, which has 43.7% more turbulence. In the investigated range, the roughened surface solar air heater had a high Nusselt number 3.15 times more than the plain tube solar heater with a comparable roughness value of 7.14 at a Reynolds number (Re) of 15,000. Case-4 solar-powered air heater with roughened surfaces reached a maximum temperature of 406.4 K

Thermal performance analysis of artificially roughened solar air heater under turbulent pulsating flow with various wave shapes

This paper presents a numerical investigation of the operation of a solar air heater (SAH) with cylindrical shape ribs under turbulent pulsating flow based on thermal and frictional considerations. Turbulence and thermal natures of flow physics are modeled by taking the relevant governing equations into the account using RNG k−ε turbulence model and transient state Reynolds-Averaged Navier-Stokes (RANS) equations. The pulsating flow is modeled with four different wave shapes including rectangular, sinusoidal, triangular, and sawtooth functions. The influence of various factors such as wave shape, Reynolds number (Re), frequency, and amplitude of pulsating flow on the thermal and hydraulic performance of SAH has been evaluated. Results indicated that the SAH with ribbed absorber section under pulsed flow has a larger Nu number compared to the air heater with smooth duct under steady flow. Moreover, the pulsating flow with a sawtooth velocity profile leads to the greatest value of the thermo-hydraulic performance parameter (THPP). The growth of pulsation frequency up to 200 enhances the heat transfer coefficient of the air heater while for frequencies larger than 200, the thermal performance declines. In addition, the increase in pulsation amplitude has a negative effect on the THPP. It was proved that the increment of the Re number enhances the THPP. Up to 53.3% improvement of THPP can be achieved by applying pulsed flow with sawtooth wave shape and ribbed absorber section compared to air heat with smooth duct under steady flow.

Modal gain characteristics of a two-section InGaAs/GaAs double quantum well passively mode-locked laser with asymmetric waveguide

Monolithic two-section InGaAs/GaAs double quantum well (DQW) passively mode-locked lasers (MLLs) with asymmetric waveguide, consisting of the layers of p-doped AlGaAs waveguide and no-doped InGaAsP waveguide, emitting at ~ 1.06 μm, with a fundamental repetition rate at ~ 19.56 GHz have been demonstrated. Modal gain characteristics, such as a gain bandwidth and a gain peak wavelength of the MLL, as a function of the saturable absorber (SA) bias voltage (Va) as well as the injection current of gain section (Ig), were investigated by the Hakki-Paoli method. With the increase of Va, the lasing wavelength and net modal gain peak of the MLL both exhibited red-shifts to longer wavelength significantly, while the modal gain bandwidth was narrowed. Both the net modal gain bandwidth and gain peak of the MLL followed a polynomial distribution versus the reverse bias at the absorber section. In addition, for the first time, it was found that Va had an obvious effect on the modal gain characteristics of the MLL.

Numerical simulation and analysis of dual base transistor laser

AbstractIn this work, characteristics of dual base transistor laser are numerically analyzed for the first time. Active base region of the transistor laser is split into two unequal regions composing of shorter and longer sections, which are biased separately. Static characteristics of transistor laser are evaluated using a rate equation model, which reveals switching action in output optical power for a longer section base current of 9.2 mA with unpumped shorter section. Hysteresis behavior in the optical output is observed for the longer section input current till 1.6 mA. Optical bistable characteristics are studied for various values of gain (longer) and absorber (shorter) section currents. Further slope efficiency is evaluated using P‐I characteristics, before the onset of bistability, for gain lever features under common emitter (CE) configuration. A maximum gain lever of 4.5 dB is observed with the longer section bias current of 1.3 mA.

Time- and temperature-dependence of the anticorrosion effect of sodium sulfide on Q235 steel for post-combustion CO2 capture system

As a heat stable salt, sodium sulfide remains thermally-unregenerable during the regeneration process for post-combustion capture. Therefore, it became important to undertake a full assessment of its potential presence in the system. The paper investigates the mechanism and influence of sodium sulfide on the corrosion behavior of Q235 steel in amine-based post-combustion CO2 capture technology with respect to exposure time and temperature. The inhibitive influence of sulfide in the system was first confirmed by electrochemical techniques, while gravimetry was used to evaluate the effect of time and temperature on the inhibitive actions. SEM/EDX and XPS were used to characterize the corrosion product films on the steel surface. The behavior of sulfide was largely dependent on its concentration as its inhibition ability decreased with increasing concentration, and this is credited to the presence of FeS corrosion film layer. Time-dependent corrosion studies of steel conducted at 50 °C for the solution with 0.05 M and 0.1 M sulfide showed that the inhibition efficiency decreased from 89.1% and 75.0% to 82.4% and 68.6%, respectively, after 7 and 14 days immersion. At 80 °C, the inhibition efficiency of 0.05 M sulfide decreased from 89.1% to 48.9% after 7 days immersion and 82.4% to 46.1% after 14 days immersion. Together with FeS layer, FeCO3, Fe2O3 were also confirmed on the steel surface by XPS measurement. The research provides practical information on the influence of sulfide in the absorber and rich-lean heat exchanger sections of a CO2 capture unit.

An integrated real-time optimization, control, and estimation scheme for post-combustion CO2 capture

This study presents a novel operational scheme for post-combustion CO2 capture (PCC) plants downstream from fuel-fired power plants. The approach is comprised of real-time optimization (RTO), nonlinear model predictive control (NMPC), and moving horizon estimation (MHE) layers. These layers are integrated to operate the system economically via a new economic function that accounts for the most significant economic aspects of PCC, including the carbon economy, energy, chemical, and utility costs. The proposed approach was employed on the case study of an MEA-based PCC absorber section, which uses a mechanistic process model to provide an accurate representation of the system. The NMPC layer is novel in its ability to enable flexible control of the plant by manipulating fresh material streams to impact CO2 capture and the MHE layer is the first to provide accurate system estimates to the controller with realistically accessible measurements. The proposed scheme was subjected to a cofiring scenario, whereby the switching between two fuels (i.e., biomass and coal) is reflected in the flue gas composition. In this scenario, a ∼19% steady-state cost improvement is observed with respect to the pre-disturbance cost. Moreover, the MHE was shown to cause an acceptable ∼0.5% of performance loss in the process economics through its effect on the NMPC. The scheme was also subjected to a ±20% diurnal variation in power plant load through steps in the flue gas flowrate and was found to provide consistent steady-state economic improvements (from ∼12% cost improvement to ∼17% loss abatement) for each of the disturbances observed. Furthermore, a price variation scenario highlighted the operational dependence of the system upon changes in economic incentives via the prices. When compared to a ‘no RTO’ case, the scheme was found to yield economic improvement ranging from ∼3% to ∼14% depending on the pricing. All scenarios in the case study displayed steady-state cost savings that exceeded the energy penalty imposed on the power plant by the PCC plant. This suggests the proposed scheme is an effective framework for the economic operation of a general class of PCC plants (i.e., with different solvents, process designs and control schemes, etc.) and can help enable the viability of PCC for the continued use of fuel-firing.

Toward robust and practical interband cascade laser frequency combs: A perspective

Multimode emission from a semiconductor laser can sometimes take the form of a low-noise frequency comb with equidistant separation between the modes. Two general types of “passive” comb operation have been explored experimentally: (1) the periodic short-pulse mode achieved by intracavity mode locking, usually obtained by incorporating a saturable absorber section into the cavity, and (2) the so-called frequency-modulated (FM) mode in which the output intensity can vary within wide bounds but does not completely turn off between pulses, and the instantaneous frequency is linearly chirped over a round trip. The FM mode sometimes manifests as a “sparse” harmonic state, with individual modes spaced by multiples of the cavity free spectral range. This Perspective reviews the current understanding of these modes, along with the conditions under which they may arise in practical devices. We then consider in detail the case of type-II mid-infrared interband cascade laser (ICL) frequency combs. Our simulations clarify the roles of carrier dynamics and group velocity dispersion and identify design modifications that may substantially improve the device performance. We find no fundamental roadblocks to the development of practical mode-locked ICL frequency combs that emit short pulses with broad spectral bandwidth for dual comb spectroscopy and other applications, alongside the FM combs that have already been demonstrated experimentally.

Megahertz scan rates enabled by optical sampling by repetition-rate tuning

We demonstrate, for the first time, optical sampling by repetition-rate tuning (OSBERT) at record megahertz scan rates. A low-cost, tunable and extremely compact 2-section passively mode-locked laser diode (MLLD) is used as the pulsed laser source, whose repetition rate can be modulated electronically through biasing of the saturable absorber section. The pulsed output is split into two arms comparable to an imbalanced Michelson interferometer, where one arm is significantly longer than the other (a passive delay line, or PDL). The resulting electronic detuning of the repetition rate gives rise to a temporal delay between pulse pairs at a detector; the basis for time-resolved spectroscopy. Through impedance-matching, we developed a new system whereby a sinusoidal electrical bias could be applied to the absorber section of the MLLD via a signal generator, whose frequency could be instantly increased from sub-hertz through to megahertz modulation frequencies, corresponding to a ground-breaking megahertz optical sampling scan rate, which was experimentally demonstrated by the real-time acquisition of a cross-correlation trace of two ultrashort optical pulses within just 1 microsecond of real time. This represents scan rates which are three orders of magnitude greater than the recorded demonstrations of OSBERT to date, and paves the way for highly competitive scan rates across the field of time-resolved spectroscopy and applications therein which range from pump probe spectroscopy to metrology.

S-band single longitudinal mode erbium-doped fiber laser with narrow linewidth based on passive multiple-subring resonator

A stable S-band single longitudinal mode (SLM) erbium-doped fiber laser (EDFL) with narrow linewidth based on passive multiple-subring resonator (PMSR) has been proposed and experimentally verified. The designed structure of PMSR can effectively expand the equivalent free spectral range and eliminate dense longitudinal modes. In addition, the dual-coupled fiber ring contained therein can form a narrow-band comb filter with good mode selection performance. Incorporating a section of saturable absorber can effectively suppress mode hopping and maintain stable SLM laser oscillation. The proposed S-band EDFL demonstrates that the linewidth is as narrow as 763.427 Hz. An optical signal-to-noise ratio of about 70 dB centered at 1499.770 nm and a wavelength stability of 0.04 nm have been obtained, respectively. This S-band EDFL is promising for the future S-band applications.

Excitability in an all-fiber laser with a saturable absorber section

We report the first demonstration of excitability in an all-fiber laser. We present clear experimental evidence in this passively Q -switched device with gain and absorber sections for defining properties of excitability, including a threshold-based excitable response and a decreasing reaction delay between input pulse and excitatory response with increasing perturbation amplitude. Our experimental results are consistent with the homoclinic/saddle-loop mechanism that forms the basis of excitability as demonstrated by a study of the Yamada model; they pave the way toward novel and reliable all-fiber architectures for neuro-inspired photonic memory and computing applications.

Study on the Fast Extension Mechanism of Double-Cavity Shock Absorber with High-Pressure Piston

Double-cavity shock absorber with high-pressure piston is the core component of the nose landing gear of the carrier-based aircraft, and its fast-extension performance seriously affects the safety of the catapult-assisted takeoff. The design of a carrier-based aircraft in our country is carried out based on the traditional method of fast-extension dynamics, and it is found that the fast-extension capability is larger than designed. This paper analyzes the working principle of the high-pressure piston shock absorber and explains that the high-pressure air cavity pushes the piston rod to extend rapidly, which will cause the cavitation phenomenon in the main oil chamber. Thus, the cavitation in the main oil chamber makes the traditional modeling method of oil-liquid resistance force no longer applicable. Then, the axial force modeling method of shock absorber considering the cavitation effect is proposed. Based on the carrier-based aircraft, the dynamic response of the shock absorber in the process of fast extension is calculated and then it is compared with the calculation results of the traditional dynamic method. It is found that due to the cavitation effect caused by the forced fast extension section of the high-pressure air plug shock absorber, the fast extension work increases by 67.6%, thus, revealing the fast extension mechanism of the double-chamber shock absorber with high-pressure piston and successfully explaining the phenomenon of the fast extension ability exceeding the expectation of the shock absorber.

Long wavelength InAs/InAsSb superlattice barrier infrared detectors with p-type absorber quantum efficiency enhancement

We studied long and very long wavelength InAs/InAsSb superlattice barrier infrared detectors that contain p-type absorber layers in order to take advantage of the longer electron diffusion length for quantum efficiency (QE) enhancement. While they can achieve higher QE than devices that use only n-type absorbers, their dark current characteristics are affected by the presence of metallurgical and surface p–n junctions, and are best operated under lower biasing conditions where the tunneling dark currents are less pronounced. Rather than using a p-type absorber only, a barrier infrared detector structure with a combination of p- and n-type absorber sections can benefit from a shallower mesa etch that reduces fabrication demands and also decreases the p-type absorber exposed surface area. We compare four complementary barrier infrared detector structures that use an n-type absorber, a combination of p- and n-type absorbers, or a p-type absorber and briefly report results from a 13.3 μm cutoff focal plane array.

Fast optical sampling by electronic repetition-rate tuning using a single mode-locked laser diode.

This paper demonstrates optical sampling by electronic repetition-rate tuning (OSBERT): a single-laser optical sampling technique capable of fast scan rates and customisable scan ranges. The method has no moving parts and is based on the electronic modulation of the repetition rate of a passively mode-locked laser diode, simply by varying the reverse bias applied directly to the saturable absorber section of the laser. Varying the repetition rate in a system built as a highly imbalanced interferometer results in pairs of (pump, probe) pulses with successive increasing delay. The resulting scan range is proportional to the magnitude of the repetition rate modulation and is scaled by the chosen length of the imbalance. As a first proof of concept, we apply the method to distance measurement, where the displacement of a target across 13.0 mm was detected with ∼0.1 mm standard deviation from an equivalent free-space distance of 36 m and at a real-time scan rate of 1 kHz. The customizable scan range and competitive scan rate of the method paves the way for single ultrafast semiconductor laser diodes to be deployed as fast, low-cost, and compact optical sampling systems in metrology, biomedical microscopy, and sensing applications.