Acid Gas Research Articles

Monitoring, modeling, and optimization of parameters affecting the recovery efficiency of acid gases from a sweetening unit

Amine processes are the advanced technology available today for the removal of carbon dioxide (CO2) and hydrogen sulfide (H2S) acid gases. Methyldiethanolamine (MDEA) is a well-known tertiary amine used selectively for the removal of carbon dioxide from natural gas. There are many parameters that can affect the efficiency of separating these acid gases from natural gas. In this paper, we have studied, modeled, and optimized different operating parameters of sour gas feed and MDEA solution which affect the CO2 recovery efficiency from an existing sweetening unit. These operating parameters are the sour gas feed temperature and pressure, volume ratio (%) of carbon dioxide in the feed gas, amine inlet temperature, and amine circulation rate. Actual data were collected from an industrial CO2 sweetening unit over one year. These data were used to study the effect of the studied operating parameters on the recovery efficiency of CO2 from the sweetening unit. All studied operating parameters were found to have an impact on the recovery efficiency of the removed gases. A response surface methodology approach was used in Design-Expert software version 13 to model the relationship between considered operating parameters and CO2 recovery efficiency. In addition, Design Expert numerical optimization has been used to maximize CO2 recovery efficiency. The results showed that the optimal range of sour gas feed temperature is 34.71 to 45.56 °C, sour gas feed pressure is 8.32 to 10.04 barg, the volume ratio (%) of carbon dioxide in the sour gas feed is 8.51 to 10.15, the temperature of the amine is 38.03 to 43.96 °C, and the amine circulation rate is 788.39 to 1122.35 m3/h. The presented work can be considered as a guideline for increasing the recovery efficiency of CO2 for both new and existing sweetening units.

Simultaneous catalytic removal of NO and chlorobenzene over Mn–Ce-Sm-Sn-Ox/P84 composite catalytic filter

The integration of surface filtration and catalytic decomposition functions in catalytic bags enables the synergistic removal of multiple pollutants (such as dust, nitrogen oxide, acid gases, and dioxins) in a single reactor, thus effectively reducing the cost and operational difficulties associated with flue gas treatment. In this study, Mn–Ce-Sm-Sn (MCSS) catalysts were prepared and loaded onto high-temperature resistant polyimide (P84) filter through ultrasonic impregnation to create composite catalytic filter. The results demonstrate that the NO conversion rates of the composite catalytic filter consistently achieve above 95 % within the temperature range of 160–260 °C, with a chlorobenzene T90 value of 230 °C. The ultrasonic impregnation method effectively loaded the catalyst onto the filter, ensuring high dispersion both on the surface and inside the filter. This increased exposure of catalyst active sites enhances the catalytic activity of the composite catalytic filter. Additionally, increasing the catalyst loading leads to a gradual decrease in permeability, an increase in pressure drops and the long residence time of the flue gas, thereby improving catalytic activity. Compared to ordinary impregnation methods, ultrasonic impregnation improves the bonding strength between the catalyst and filter, as well as the permeability of the composite catalytic filter under the same loading conditions. Overall, this study presents a novel approach to prepare composite catalytic filter for the simultaneous removal of NO and chlorobenzene at low temperatures.

Eleven‐Year Survey of the Magmatic‐Hydrothermal Fluids From Peteroa Volcano: Identifying Precursory Signals of the 2018–2019 Eruption

AbstractOver the past decade, we have conducted geochemical and isotopic monitoring of the fumarolic gases of the Peteroa volcano (Argentina‐Chile). Using the resulting data set, we constructed a conceptual model that describes the evolution of the magmatic‐hydrothermal system and identifies precursory geochemical signals of the last eruption. Our data set includes new chemical and isotopic analyses of fumarolic gas samples collected from 2016 to 2021, as well as previously published data from the 2010–2015 period. After an eruptive period in 2010–2011, the activity was characterized by low degassing rates and seismic activity. However, an increase in seismic activity and fumarolic gas emissions was observed from 2016 to 2018–2019 eruptive episode, leading to a major phreato‐magmatic eruption. Fumarole gases show different compositions during quiescent versus unrest/eruptive degassing related to the interaction of deep (magmatic) and shallow (hydrothermal) fluid contributions. During quiescent periods, fumaroles exhibited low SO2/H2S, HF/CO2, and HCl/CO2 ratios (<0.1), revealing a dominant hydrothermal contribution. In contrast, during pre‐and syn‐eruptive periods, fumaroles showed ratios up to 100 times higher indicative of an enhanced magmatic input. When compared to the evolution of the seismic activity, the increment of magmatic‐related strong acidic gases suggests repeated inputs of hot magmatic fluids, which are only partially dissolved into the hydrothermal system feeding the fumaroles. Interestingly, the 3He/4He and δ13C‐CO2 values remained relatively constant during the magmatic and hydrothermal degassing in 2016–2021, suggesting that the deep magmatic gas source did not significantly change throughout variations in Peteroa's activity.

Performance of Polyaniline Thin Film as a Functional Material of Acid Vapor Sensors

Polyaniline (PANI) is a conductive polymer that can be produced by the electrodeposition process. The purpose of this research is to evaluate the performance of PANI sensors on hydrochloric acid (HCl) and acetic acid (CH3COOH) vapor using a scan rate of 100 mV/s and ten cycles, a thin PANI layer was created on the surface of the ITO substrate. The PANI spectroscopic test results before and after CH3COOH vapor exposure revealed no differences and remained within the PANI functional group range. A four-point probe (FPP) test was performed to evaluate the sensing performance of the PANI thin film against analyte gas. The results of recovery time, response time, and sensitivity tended to increase as analyte concentration increased. The quickest CH3COOH sensing (1 ppm) has a reaction time of 29.7 seconds, a recovery time of 21.9 seconds, and a sensitivity of 5.11%. The greatest CH3COOH sensing (10 ppm) resulted in a reaction time of 50.3 seconds, a recovery time of 39.7 seconds, and a sensitivity of 13.64%. The reaction time for the lowest HCl sensing (1 ppm) was 42.6 s, the recovery time was 32.4 s, and the sensitivity was 7.82%. The greatest level of CH3COOH sensing (10 ppm) resulted in a response time of 60.6 s, a recovery time of 55.3 s, and a sensitivity of 16.31%. As a result, the PANI thin film is a functional material for acid gas sensors.

High-pressure solubility measurement and eNRTL thermodynamics modeling of carbon dioxide in aqueous solutions of 2-((2-aminoethyl) amino) ethanol + dimethyl sulfoxide at different conditions

We measured the solubility of carbon dioxide in the aqueous solution of 2-((2-aminoethyl) amino) ethanol (AEEA) as a chemical solvent plus dimethyl sulfoxide (DMSO) as a physical solvent. A quasi-static high-pressure equilibrium cell was used for the measurement of CO2 solubility in the AEEA + DMSO + H2O systems at the compositions of (10, 20, 70), (15, 15, 70), (20, 10, 70), (25, 5, 70) wt. %. We performed the experiments at temperatures of 318.15, 328.15, and 343.15 K and pressures up to 5000 kPa. Also, we compared the CO2 solubility in the aqueous mixture of 2-((2-aminoethyl) amino) ethanol (AEEA) + dimethyl sulfoxide (DMSO), 2-((2-aminoethyl) amino) ethanol (AEEA) + sulfolane, methyl diethanolamine (MDEA) + dimethyl sulfoxide (DMSO), and methyl diethanolamine (MDEA) + sulfolane. We used the Electrolyte-NRTL thermodynamic model to correlate the solubility of CO2 in the aqueous solutions of AEEA + DMSO and to predict the partial pressure of CO2 versus the acid gas loading. The present modeling provided an excellent representation of the experimental data over the whole temperature range for 121 experimental data, which resulted in an average absolute deviation of 12.96 %.

Absorption of HCl on sodium-based absorbents at medium and high temperatures: The effect of competing absorption of SO2 and H2O

The utilization of sodium bicarbonate (NaHCO3) as a solid reactant for the mitigation of acidic pollutants from industrial flue gas streams represents a straightforward and efficient process solution. The paper addresses the problem of medium- to high-temperature flue gas dechlorination by investigating the effects of base particle size, temperature, water vapour and different flue gas fractions on the removal of HCl from simulated flue gases by NaHCO3 in a fixed-bed reactor, and the effects of the presence of SO2 and H2O on the chlorination reactivity of NaHCO3 are also investigated by density functional theory (DFT) calculations. The adsorption results implied that 300 °C was the optimum temperature for HCl removal by NaHCO3 in a reaction system not affected by SO2 or H2O; The higher the HCl concentration, the greater the HCl capture, but when the concentration is too high, due to the dense product layer makes the HCl gas molecules to the internal diffusion is blocked, the dechlorination effect becomes poor. The smaller the particle size of NaHCO3, the better the removal of HCl. In the system containing SO2, theoretical calculations based on density functional theory show that the presence of SO2 affects the exchange of electrons between the Cl atoms in HCl and Na2CO3, and the bonding ability of the Na-Cl bond is weakened, thus weakening the dechlorination ability of Na2CO3; However, SO2 has little effect on HCl removal at the same concentration, due to the fact that HCl rapidly consumes the easily accessible surface of the absorber and SO2 must diffuse deeper into the particles for the reaction to occur, suggesting a preferred reaction between HCl and NaHCO3. After the addition of H2O, the adsorption energy of HCl on the surface of Na2CO3(200) was greater than the adsorption energy of SO2 on the surface of Na2CO3(200), and HCl was preferentially adsorbed on the surface of Na2CO3(200), which preferentially reacted with the absorber. These findings help to elucidate the principle of HCl absorption by NaHCO3 and the competition mechanism between HCl and SO2, and improve the theoretical knowledge of acid gas absorption by NaHCO3.

Lysinibacillus fusiformis: a novel fibrolytic native strain from the rumen microbiome that increases in vitro digestibility of central agricultural residues

ABSTRACT Increasing the digestibility of agricultural residues is one goal of sustainable livestock production, and the role of rumen microbiome-feed interaction is critical for efficient digestion. This study was aimed at isolating and evaluating in vitro the effect on dry-matter digestibility (IVDMD), relative feed values (RFV), volatile fatty acid (VFA) synthesis, pH changes, and gas production (GP) by the inclusion of native rumen strains in mixtures of corn, sorghum, and oat agricultural residues with ruminal fluid. The results show that an inoculum of 1 × 1010 colony-forming unit per millilitre (CFU/mL) of the aero-tolerant native rumen strain Lysinibacillus fusiformis increases the IVDMD, RFV, and VFA values of all mixtures. During agricultural residue fermentation, the pH was stable, and propionic acid was the primary fatty acid synthesized, indicating increased energy availability for efficient cattle growth performance while limiting molecular hydrogen (H2) synthesis for conversion to methane (CH4). These results suggest that L. fusiformis could be used as a direct-feed microbial to promote sustainable livestock production. To the best of our knowledge, this is the first report to link the fermentation of fibrous agricultural residues in ruminal fluid inoculated with a fibrolytic native strain and digestibility in favour of increasing the efficiency of livestock production.

Influence of metallurgical factors on the hydrogen induced cracking of carbon steel wires in H2S-containing environments

Flexible pipes armor wires used in offshore oil and gas fields can corrode if water and acid gases, such as H2S, build up in the annulus. Such an environment may provide the conditions for hydrogen-induced cracking (HIC) depending on the corrosive solution composition and the metallurgical characteristics of the armor wire, such as microstructure and microhardness. The critical zones of HIC incidence were investigated for tensile and pressure armor wires with carbon content of 0.7 and 0.3 wt% C, respectively. Results were obtained through immersion testing and hydrogen permeation measurements in near neutral substitute ocean water (solution A) and standard acid solution (solution B) at ambient temperature bubbled with a gas mixture (1 % H2S + 99 % N2). Scanning electron microscope (SEM) and computed tomography (CT) evidenced the microstructure and microhardness features associated to crack morphology and location. According to the results, the increase of carbon content in cold drawn steels promoted the accumulation of hydrogen mainly in regions of high microhardness, inducing a high density of cracks in a stepwise cracking (SWC) propagation. This indicates that the driving force for HIC was associated with metallurgical factors, such as microhardness, the presence of hydrogen trapping sites of high energy, dislocations and ferrite/cementite morphology and distribution, occurring even in the absence of non-metallic inclusions. Additionally, environmental conditions, such as the low pH found in solution B, increased the criticality of HIC. Both materials presented a crack sensitivity ratio (CSR) that grew over time in solution B, but no cracks were observed in the pressure armor wire tested in solution A. Hydrogen permeation curves were delayed for both tested armor wires in solution A due to its near neutral pH characteristic. Hydrogen diffusivity (Deff) of the tensile armor wire was lower than the pressure armor wire, indicating the presence of a higher density of hydrogen trapping sites in a harder and elongated pearlite.

Atmospheric Chemistry of NH2SO3H in Polluted Areas: An Unexpected Isomerization of NH2SO3H in Acid-Polluted Regions.

NH2SO3H is an effective nucleation agent for the formation of atmospheric aerosols and cloud particles. So, the ammonolysis of SO3 to form NH2SO3H without and with neutral (H2O) and basic (NH3) trace gases has been extensively investigated. However, the acidic trace gas X (X = H2SO4 and CH3SO3H)-assisted ammonolysis of SO3 is still up for debate. In this work, a comprehensive theoretical investigation of X-assisted ammonolysis of SO3 and its reverse reaction (the isomerization of NH2SO3H to form SO3-···NH3+) was carried out in the gas phase and at the air-water interface. The gas-phase results show that X-assisted isomerization of NH2SO3H to form SO3-···NH3+ is more energetically and kinetically favorable than its reverse reaction and the isomerization of NH2SO3H in the presence of H2O and NH3. Such unexpected findings revealed that gas-phase NH2SO3H is highly reactive in the presence of acidic trace gas in contrast to the high stability of NH2SO3H in neutral and basic conditions. At the air-water interface, the X-assisted isomerization reaction of NH2SO3H involves multiple water molecules. The loop structure of the reaction center (X···NH2SO3H···3H2O) promotes the transfer of protons in the water molecules to form the SO3-···NH3+ ion pair, which can then interact with several interfacial water molecules to form ammonium bisulfate. These interfacial reaction channels follow a stepwise mechanism and proceed at the picosecond time-scale. The findings of this study will contribute to a better understanding of the atmospheric behavior of NH2SO3H in polluted acidic trace gases.

Long-term monitoring of indoor, outdoor, and personal exposure to gaseous chemical compounds

Seasonal variations of chemical compounds in indoor air and outdoor air and personal exposure to these chemicals were continuously monitored for 6 years using four types of passive sampling devices: PSD-BPE/DNPH packed with 2,4-dinitrophenylhydrazine and trans-1,2-bis(2-pyridyl)ethylene coated silica for ozone and carbonyls; PSD-VOC packed with Carboxen 572 or Active Carbon Beads particles for volatile organic compounds; PSD-TEA packed with triethanolamine impregnated silica for acid gases; and PSD-TEA packed with phosphoric acid impregnated silica for basic gases. Many chemical compounds except for nitrogen dioxide, formic acid, and benzene showed seasonal variations with high concentrations in summer and low concentrations in winter. In particular, formaldehyde, nonanal, 2-ethyl-1-hexanol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and ammonia concentrations showed remarkable seasonal variation. For example, the concentration of formaldehyde in February and August was 5.9 and 40 μg/m3, respectively, a difference of about 7 times. Although there were large differences in the concentrations in each house, the fluctuation pattern was almost the same every year in each house. By contrast, nitrogen dioxide, formic acid, and benzene concentrations were low in summer and high in winter. These compounds were generated by kerosine and gas stoves in winter. Long-term continuous monitoring revealed that annual mean concentrations could be estimated using data from February and August. Personal exposure concentrations could be classified into four patterns: chemicals affected by the indoor environment such as formaldehyde, chemicals affected by the outdoor environment such as ozone, chemicals affected by the occupational environment such as hexane, and background level chemicals such as benzene (without kerosine and gas stoves). Indoor and outdoor measurements are means to investigate the “health” of each environment. Personal exposure measurement using PSD-samplers is suitable for assessing the health risk of chemical compounds to humans.

Perspectives of the offshore CCS development in the polish EEZ on a Baltic Sea: insights from ongoing preliminary research for pilot CO2 injection

The key to effectively combatting progressive climate change lies in promptly reducing greenhouse gas (GHG) emissions, particularly carbon dioxide (CO2), whose concentration continues to rise due to human activities. The European Union (EU) has established legally binding targets, including achieving climate neutrality by 2050, with an intermediate goal of reducing GHG emissions by 55 % by 2030 compared to 1990 levels. Poland, one of the major CO2 emitters in Europe, also possesses significant storage potential in terms of projected CO2 capacity within its sedimentary basins. Considering this, the implementation of Carbon Capture and Storage (CCS) technology could play a crucial role in Poland's efforts to decarbonize its economy. For several years, the Oil and Gas Institute – National Research Institute (INiG – PIB) has been at the forefront of domestic research activities concerning underground CO2 injection. The involvement dates back to 1996 by pioneering the development of a concept, design, and implementation of one of Europe's earliest industrial installations for reinjecting acid gas, consisting of approximately 80 % CO2 and 20 % H2S, into the reservoir water underlying a productive natural gas field. This facility in Borzęcin operated by PGNiG (now part of ORLEN GROUP), is a unique testing ground where the injection process has been running continuously for 27 years. The research conducted at INiG – PIB has played an important role in identifying appropriate geological structures in Poland with a total storage capacity of 10-15 Gt CO2. Around 90-93 % of the CO2 storage capacity is found in saline aquifers, with a significant portion of approximately 7-10 % identified within mature hydrocarbon fields.Despite recent progress in managing industrial CO2 emissions, the peace of CCS development falls short of meeting the objectives set by the Paris Agreement. The main hindrance lies in the absence of a suitable regulatory framework for CO2 transport and storage infrastructure. Recognizing this challenge, the national offshore operator, Lotos Petrobaltic (LPB), presented in 2021 a Green Paper on CCS development in Poland. This document outlines a set of recommendations for legislative alternations to facilitate the initiation of large-scale, commercial CCS projects within the country. Given the current national regulations and assumptions regarding low social barriers, the most expeditious approach to implementing a First-of-a-Kind (FOAK) large-scale CCS project in Poland seems to involve deploying depleted hydrocarbon reservoirs located at the Polish Exclusive Economic Zone (EEZ) within the Baltic Sea. The LPB, with research and scientific support from INiG – PIB, has launched a program aimed at conducting a preliminary assessment of CO2 injection in Middle Cambrian sandstones. The project is scheduled to begin with a pilot injection into the well-identified, depleted structure of the B3 oil reservoir. Subsequently, it may be expanded to include adjacent hydrocarbon reservoirs and could ultimately encompass the entire Cambrian aquifer.The Cambrian aquifer is characterized by complex tectonics, comprising several blocks separated by fault zones. These fault zones may act as barriers to the propagation of reservoir fluids, as demonstrated by the presence of hydrocarbon traps in the vicinity of some fault zones.The B3 oil field, covering an area of 36,2 km2, is an elongated SW-NE, asymmetric anticline, cut on the west side by an inverted fault zone. The reservoir interval, with an average depth of 1450 meters below sea level comprises of sandstones of the Paradoxides Paradoxissimus (Middle Cambrian Zone) horizon showing a monoclinal dip towards the south-east. The reservoir formation exhibits heterogeneity in both within the vertical profile and the horizontal direction, characterized by a wide range of petrophysical parameters values. According to preliminary assessments, the CO2 storage capacity of the B3 site is estimated to be around 7 Mt CO2. The expansion of CO2 storage to the remaining hydrocarbon fields and the overarching Cambrian aquifer megastructure could potentially increase the total storage capacity to more than 150 Mt. The envisioned CO2 sources include emitters from the chemical industry, where CO2 is a by-product of the fertilizer production process. During the project’s pilot phase, the predicted CO2 injection rate is expected to be between 25-50 kt CO2 per year. As the project transitions to the upscaled phase, the injection rate is projected to increase significantly, reaching approximately 2 Mt CO2 per year. The transportation of CO2 for full-scale injection is planned through multimodal means, considering potential synergies with the multimodal CO2 Terminal in Gdansk, which is being planned under the ECO2CEE project (formerly EU CCS Interconnector). A pipeline connection between the offshore storage area and the CO2 Terminal is under consideration.The main research problems addressed within the INiG – PIB and LPB joint initiative include determining the sequestration potential of the Cm2pp aquifer, assessing the feasibility of the CO2-EOR process, recognizing the effects of injected CO2/reservoir rock/caprock interactions on injectivity, geomechanical parameters, and sealing integrity, as well as investigating CO2-induced corrosion of steel components in the transport and injection plant.

Experimental tests and modeling of H2S-CO2-brine systems – a case study

A geochemical study aimed to determine the impact of CO2 and H2S, mixtures on the representative formation rocks from the Dębowiec Fm. and Paralic series of the Upper Silesian Coal Basin, and the adjacent Małopolska Block (Poland) was performed.In the way of experiments and hydrochemical modeling the following goals were achieved: determination of the impact of acid gases on the mineralogical composition and porosity, and the assessment of mineral trapping capacity of cap rocks.Dissolution of skeletal grains, as the dominant process (the most distinct in carbonates and chlorite) was determined by means of SEM analysis in all of the samples.The increase in porosity at the injection stage, depending on the mineralogy of samples was caused by the decomposition of calcite and siderite or ankerite (Dębowiec Fm.), daphnite, clinochlore, and siderite (Paralic series) and hematite, ankerite, dolomite (Małopolska Block).After 10 000 years of simulated storage, the total porosity decreased in the cap rocks by several percent points, mainly due to precipitation of saponite, muscovite, gibbsite, phlogopite and dawsonite, in favor of the rock insulating properties. Among the secondary minerals enabling the trapping of CO2 and S in simulated storage there were observed: dolomite and pyrite (Dębowiec Fm.), dolomite, calcite and pyrite (Paralic series) and siderite, anhydrite, pyrite (Małopolska Block).Maximum calculated mineral-trapping capacity, calculated based on the results of kinetic modeling, reached 43.4 kgCO2/m3 and 44.9 kgS/m3 for CO2+ H2S co-injection into the Dębowiec Fm. Miocene rock.

Analysis of clinical characteristics in proximal and distal reflux monitoring among patients with gastroesophageal reflux disease.

The purpose of this study was to examine the characteristics of proximal and distal gastroesophageal reflux in patients with gastroesophageal reflux disorder and analyze their clinical symptoms. A total of 67 patients with typical esophageal symptoms were selected for this study. All participants completed the reflux disease questionnaire and a questionnaire survey of extraesophageal symptoms. Diagnosis was made using a 24-h impedance-pH detection and proton pump inhibitor. The results showed that the proximal reflux group had a higher number of acid reflux episodes compared to the distal reflux group (P < 0.05). Similarly, the proximal reflux group also had a higher number of gas reflux episodes compared to the distal reflux group (P < 0.05). On the other hand, the distal reflux group had a higher number of mixed reflux episodes compared to the proximal reflux group (P < 0.05). These differences were statistically significant. This study revealed that acid reflux and gas reflux were more predominant in the proximal reflux group, while mixed reflux was more predominant in the distal reflux group.

Cryogenic CO2 capture from oxy-combustion flue gas by a hybrid distillation + physical absorption process

Hybrid flowsheets are defined, in the context of process intensification, as alternatives suitable for replacing energy-intensive separation methods through the combination of more than one unit operation. Given the undoubted importance of carbon capture, utilization, and storage (CCUS) in the next decades in the path to net-zero emissions and even negative emissions scenarios, this work focuses on CO2 capture from an oxy-combustion flue gas by means of a distillation-based hybrid process that avoids CO2 freeze-out, which is capable of delivering a liquid CO2-rich stream that can in principle be pumped to transport pressures with lower energy consumption in comparison to conventional post-combustion CO2 capture processes based on chemical absorption. A distillation-based process and a hybrid distillation + physical absorption process have been studied based on simulations in Aspen Hysys® V11 using the Peng-Robinson Equation of State and the “Acid Gas – Physical Solvents” thermodynamic property package. Firstly, a CO2 capture process based on cryogenic distillation has been proposed and a sensitivity analysis on the operating pressure and specified CO2 recovery has been performed in order to determine the most convenient configuration, balancing capital and operating costs. Then, a hybrid capture process has been proposed and analyzed, where cryogenic distillation is the bulk removal step and physical absorption into a mixture of homologues of the dimethylether of polyethylene glycol (DEPG) is the finishing step. Energy and economic analyses have shown that the hybrid process, delivering a CO2 product respecting the stringent purity requirement on the oxygen content for application for Enhanced Oil Recovery (EOR) and in the food industry is less energy intensive than the standalone cryogenic distillation, though it is characterized by higher capital costs.

Simulation Of Acidic Water Purification Process In Refinery Based On Determining Appropriate Operating Conditions

Acidic process water produced by refineries contains some hazardous pollutants such as (H2S and NH3). Acid water extraction units remove both compounds from the water. The removed contaminants are sent to a sulphur recovery unit to produce sulphur and avoid any acid emissions contrary to environmental regulations. Water pollution is a problem that concerns all people in the world. In view of the importance of preserving the environment and water resources, in this research, the simulation of the acid water treatment unit in the refinery was studied using the Aspen Hysys software based on determining the appropriate operating conditions. The NRTL electrolyte activity coefficient model was used to predict the system's thermodynamic behaviour. The simulation results showed that the suitable temperature for the feed entering the tower is about 38°C and the convenient distance for the trays in the disposal tower is 0.54 mm. Under these conditions, the concentration of hydrogen sulphide 0.1694 and 0.2418 of ammonia in the acid gas exiting the tower reaches its maximum at a molar flow rate of the mixture of about 39.86 kgmol/h, according to the economic considerations of the operating tower.

Halogenated polymers as a problematic component in the pyrolysis of waste plastics

The study deals with the complications associated with the pyrolysis of a polymer releasing highly corrosive compounds and other products that are difficult to be utilized in practice. Poly(vinyl chloride-vinyl acetate) was chosen as a sample material. This copolymer was subjected to slow pyrolysis up to a temperature of 650 °C, which was achieved with a temperature ramp of 10 °C min‒1. Thermal decomposition took place in a batch apparatus in nitrogen atmosphere. The evaluation of the experiments included a mass balance using an online recording of gas and condensate formation, which was followed by an analysis of the obtained products. The tests showed very small yields of condensates (pyrolysis tar) in the range of 3.0 – 5.5% compared to gas production reaching 71.1 – 72.1% of the raw material weight. Within the discussion, the problem with the production of non-flammable gas consisting mainly of HCl in the initial stages of pyrolysis was highlighted. Under the given conditions, the release of acid gases, in which HCl was gradually replaced by also non-flammable CO2, continued up to about 400 °C. Only gases collected from this temperature above and having a calorific value of 33.5 MJ m‒3 (20 °C / 101.32 kPa) can be considered energetically usable. Condensates mainly represented by a mixture of aromatic hydrocarbons, acetic acid and chlorobenzene were also evaluated as problematic for possible use. The possibilities of physical activation of solid pyrolysis residues by steam at temperatures of 850 and 900 °C were also tested. All experiments led to obtaining products with very small specific surface areas in the range of 1 – 6 m2 g–1. The process loss during activation reached 25 – 33% of the pyrolysis residue weight, depending on the applied temperature and contact time with steam. These values show that the reaction of the activation medium with the sample took place more or less only on the outer surface of the particles and did not lead to the development of an internal porous structure. The achieved results were compared with the identically processed samples of waste tires, which were evaluated as promising in tests carried out in the past. The contrast be-tween the two materials clearly spoke against the discussed copolymer. The results of the experiments can be interpreted, among other things, as a certain warning against attempts at industrial pyrolysis processing of this type of plastic.

Wet‐Oxidative Desulfurization as a Flexible and Greener Way for H2S Removal from Acid Gases

AbstractIn wet‐oxidative gas desulfurization processes, absorbed H2S is directly converted to sulfur by a redox catalyst dissolved in a circulating scrubbing solution. High flexibility is achieved through the availability of different catalyst classes. In this work, a process based on the Takahax process was investigated in a pilot plant under industrially relevant conditions with coke oven gas. A stable plant operation without sulfur precipitation was achieved by a suitable choice of the operating conditions. The solid‐free operating window was determined and a sulfur redissolution strategy developed.

Feasibility Assessment of Acid Gas Injection in an Iranian Offshore Aquifer

Acid gas injection operations function as the commercial equivalent of certain aspects within the realm of geological CO2 storage. Acid gas, composed of H2S and CO2, alongside minor quantities of hydrocarbon gases stemming from either petroleum production or processing, constitute the composition of acid gas. The primary aim of acid gas injection operations lies in the disposal of H2S. Nevertheless, substantial volumes of CO2 are concurrently injected due to the economic impracticality of segregating the two gases. This investigation delves into the comprehensive, step-by-step procedure that can be employed to determine the suitability of a field or formation for acid gas injection, utilizing all accessible data, including the literature and data from neighboring fields. This approach incorporates sensitivity analysis of various parameters to ascertain the feasibility of AGI while minimizing costs and time consumption. The focus of this study centers on evaluating the feasibility of Acid Gas Injection (AGI) in a saline aquifer offshore in Iran. The assessment encompasses the examination of reservoir properties, geomechanical aspects, caprock integrity, and gas plume dynamics. The Surmeh formation emerges as a promising candidate for AGI due to the presence of upper dolomite and lower carbonate within the rock formations. Geomechanical analysis reveals a pore pressure of 3800 psi and a fracture pressure of 6100 psi. Caprock integrity, particularly within the Hith formation, emerges as pivotal for both containment and long-term stability. Seismic mapping highlights variations in caprock thickness, influencing containment effectiveness. Capillary trapping emerges as a significant factor in short-term gas entrapment and plume distribution. Numerical simulations elucidate the impact of heterogeneous rock properties on capillary trapping and gas plume movement. The projection estimates approximately 2 TCF (Trillion Cubic Feet) of acid gas injection into the Surmeh formation. Based on the acid gas content and the gas in place at the source of injection, the recommended injection rate stands at 180 MMSCFD (million standard cubic feet per day). The formation’s inherent tightness limits injectivity, allowing for a maximum achievable rate of 7 MMSCFD with a permeability of 1 mD (millidarcy). However, a higher porosity (12%) and a permeability of 100 mD enable more efficient injection without fracturing the formation. To achieve this, it becomes imperative to implement two injection wells, each with a capacity of 90 MMSCFD.

Comparison of oxidation absorption and reduction absorption process for sulfur recovery tail gas treatment of natural gas treatment plants in China Part Ⅰ: Technical section

BackgroundChina's newest SO2 emission policy for the natural gas industry forced natural gas treatment plant to add sulfur recovery tail gas treatment unit. In this context, the oxidation absorption process has been applied for the first time in Sichuan Basin. However, the advantages and disadvantages of this process compared with the traditional reduction absorption process have not been reported. MethodsThe two processes were compared from the technical angle in this paper. The data of one plant in Sichuan Basin was selected as the simulation condition. Significant findingsThe calculation results showed good agreement with plants data. The solution circulation amount of oxidation absorption process were 19 and 18.52 m3/h, which were just 20 %∼25 % of that for reduction absorption process. Meanwhile the acid gas returned amount was only about 14 % of reduction absorption process. However, the main process gas flow was 1.5 times of reduction absorption process. Regarding the utility consumptions, the oxidation absorption process had more advantages in electricity consumption, but it was inferior in fuel gas and circulating water consumption.

Isotopic comparison of ammonium between two summertime field campaigns in 2013 and 2021 at a background site of North China

Ammonia (NH3) is the primary atmospheric alkaline gas, playing a crucial role in the atmospheric chemistry. Recently, non-agricultural emissions have been identified as the dominant sources of NH3 in urban areas. However, few studies have quantified the contributions of different sources to regional NH3. This study conducted two summertime field observations in 2013 and 2021 at a background site of North China to comprehensively explore the regional variations in concentration, nitrogen isotope composition (δ15N), and sources of ammonium (NH4+). The results indicate that NHx (NHx = NH3 + NH4+) concentration has increased in 2021, but the fNH4+ (NH4+/ NHx) has decreased significantly. The δ15N-NH4+ values show a significant increase, ranging from −4.7 ± 8.1 ‰ to +12.0 ± 2.4 ‰. The increase can be attributed to two primary factors: changes in fNH4+ resulting from the reduction of atmospheric acid gases and alterations in the sources of NH3. Bayesian simulation analysis reveals substantial variations in NH3 sources between 2013 and 2021 observations. Non-agricultural sources have significantly increased their contribution to NHx concentration, with vehicle exhaust and NH3 slip experiencing growth rates of 187 % and 104 %, respectively. Our results confirm the dominate contribution of non-agricultural sources to regional NH3 at the present stage and propose relevant mitigation strategies, which would provide essential insights for reducing NH3 emissions in North China.