جستجوی مقالات مرتبط با کلیدواژه « hydrogen sulfide » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

In this work, the Monte-Carlo molecular simulation was applied to study the adsorption of H2S and CO2 from natural gas onto silica chabazite zeolite. The isothermal adsorption curves of pure CH4, CO2, and H2S on zeolite were simulated in a pressure range of 0-200 kPa at the temperature of 298, 323 and 348 K. The heat of adsorption analysis indicated that the physical adsorption has occurred. The simulation results showed a good agreement with experimental data and the average relative error of simulated results in 298 K for those gases were reported as 18.31%, 6.6%, and 9.8%, respectively. The isotherm of dual and triple combinations of these gases has been studied in the composition range of 70-90% of CH4. Results indicate that the tendency of chabazite for adsorption of H2S is much more than two other gases, because of its high polarity. In addition, results report that the selectivity of CO2 and H2S on chabazite in dual and triple gas mixtures are almost 2 and 4, respectively.

One of the widely used methods to remove acid gas is surface adsorption using solid molecular sieves. The advantages of H2S adsorption with molecular sieves can be seen in reversibility of the process, chemical and thermal stability, no secondary product, and high selectivity of H2S in these adsorbents. Therefore, in this study, Aspen-Adsim software was used to investigate the effect of various parameters on adsorption of H2S on 4A molecular sieve adsorbent. The desired bed is considered vertical and one-dimensional. The results related to the breakthrough curves and saturation time showed that maximum amount of adsorption occurred in early times. As the adsorption time increases, the rate of H2S adsorption decreases. The results of investigating the effect of operating parameters showed that increasing the tower pressure from 90 to 104 bar reduces the output H2S content by 21 ppm. Also, reducing the feed temperature showed significant results on amount of H2S absorption and the reduction of the output H2S content, so that for every one degree of temperature reduction in the feed gas temperature, the dew point temperature of the output was reduced by 1.6°C. Due to high amount of absorbent and its heat capacity compared to the amount of H2S in the gas phase, a slight temperature increase occurs along the tower so that the difference between inlet and outlet temperatures does not exceed 1˚C. According to the breakthrough curve, it was also determined that after 7920 seconds, the entire bed of the tower is saturated with H2S molecules.

Measurement of sulfur compounds in the tail gas flow in the sulfur recovery unit is necessary in order to fine control the combustion furnace airflow and efficiency enhancement. In this research, required equations for calculation of air demand in feedforward and feedback control loops in the sulfur recovery unit of Ilam Gas Treating Plant are developed. First, the process was simulated. Then, using MLP neural network and nonlinear regression, K factor was determined for tail gas analyzer air demand calculation. Total required air is sent to the combustion furnace through two lines: trim and main, such that 92.5% of air is passed through the main line. Meanwhile, tail gas analyzer air demand is in the range of -5 to +5 % of the total required air. The presented equations in this research can be employed for other sulfur recovery units.

In this research, the adsorption potential of carbon dioxide and hydrogen sulfide storage in metal organic frameworks has been studied and modeled. Studying four different type of micro porous coordination polymer adsorbents metal organic frameworks including MOF-2 (Zn2 (BDC)2), MOF-74 (Zn2 (DHBDC)), IRMOF-1 (Zn4O (BDC)3) and MOF-177 (Zn4O (BTB)2) showed that the adsorbent have different structure caused different performance in gases adsorption. For adsorption isotherm modeling of these adsorbents used two parameters isotherm models. For calculation parameters of the models was used nonlinear regression technique. The results showed that the models have good agreements with experimental data. Hill model has high accuracy to compare with other models. The parameter values of D-R model for all adsorbents showed that the processes were physical adsorption and IRMOF-1 for H2S and MOF-74 and MOF-2 for CO2 adsorption were suitable.

Gas detector placement is one of the most important issues in the gas and oil industries since fast detection and subsequently fast control of the toxic and flammable gas releases could prevent major accidents or disasters. In this paper, dispersion of Hydrogen Sulfide at the one of the units of Sirri Gas Compression Facility of Iranian Offshore Oil Company has been simulated with computational fluid dynamics methods. In this simulation, different scenarios according to the different wind directions and speeds, leakage hole diameters, direction of leakages, operating fluid types and topology of the environment have been studied. Therefore, 4 wind directions, 6 wind speed steps, 11 sources of leakage or their directions, and 2 equivalent holes were considered, and the results were evaluated in 550 scenarios which each scenario has its own frequency of occurrence. The main range of gas dispersion discretized to 2391 points on the three parallel surface with 0.5 m intervals from ground surface. Probability of each scenario was calculated from meteorological data, and discharge probability data were gathered from references. Probability of presence of more than 10 ppm of toxic gas after 20 seconds in each scenario was computed. Finally, by summing up the probabilities of the all scenarios in every point, the optimized locations for placement of detectors was determined, and the results of these simulations were compared with the existing detectors placement. Finally, by considering the results, it is found out  that the current location of two detectors is not correct, and better locations can be selected.

A huge portion of natural gas reserves contains hydrogen sulfide in Iran. Therefore, the conversion of hydrogen sulfide to sulfur is important. In this paper, at first, titanium dioxide nanoparticles were synthesized with simple and inexpensive method of sol gel, and then nitrogen was doped on it, and their performance was investigated to direct hydrogen sulfide oxidation to elemental sulfur. The synthesized catalysts were characterized for the structure and morphology by XRD, FESEM, EDX, and BET analysis. Moreover, doping titanium dioxide nanoparticles with nitrogen has shown a better performance (more than 7% increases) for the removal of hydrogen sulfide than the undoped TiO2. The reason can be attributed to the synergistic effects of nitrogen and titanium dioxide nanoparticles, the increase of the specific surface area and the pore volume of N-TiO2, and also the existence of alkaline nitrogen groups in the titanium dioxide network.

In this study, the selective adsorption is considered by chemical absorption by caustic aqueous solution. This study is based on the simulation with the Aspen-Plus version 9. The rate-based model has been used to determine the separation efficiency for different operating conditions in the simulation. The NRTL electrolytic model is used to describe the non-ideal behavior in liquid phase, while the Soave-Redlich-Kwong equation of state is used for vapor phase. Simulation results show the high efficiency of caustic for the removal of hydrogen sulfide. The results show that the concentration of hydrogen sulfide in the outlet gas from the absorption tower is below 0.5 ppm. It is also discussed about the replacement of different packings and their effect on the reduction of caustic consumption. The results showed that at constant caustic flow rate and concentration, FLEXIMAX-metal 400 packing had better performance in absorbing hydrogen sulfide.

   Sulfide removal from sour water is essential, before reuse or release of sour water into the environment. Regarding the high costs of traditional methods, biological removal can be used as a reliable alternative. Biological sulfide removal from sour water was investigated in a batch reactor using Thiobacillus sp. as a dominant species of a mixed culture. A conceptual model was developed to describe the process of H2S removal from sour water in the batch reactor. The model considers H2S and O2 transfer between liquid and gas phases, biological oxidation of H2S to sulfate and elemental sulfur, and chemical oxidation of H2S to thiosulfate in the liquid phase. The governing equations were derived using the principles of mass conservation and biochemical reactions. Several batch runs were performed to obtain experimental data on the variation of sulfide, sulfate, thiosulfate, and oxygen concentrations in the system as a function of time, and an algorithm was devised to use the method of Particle Swarm Optimization together with the numerical solution of the model equations to estimate biokinetic parameters. Additional batch runs under different conditions were performed to verify the accuracy of the model. These results indicated reasonable accuracy of the model to predict the performance of a batch reactor for the removal of H2S from sour water. The novelty of this model is considering different pathways for sulfide oxidation which includes product selectivity.
Main The maxim specific oxygen uptake rate (SOUR=OUR/X) is one of the most important parameters in the evaluation of the biological activity of the microorganisms. The calculated value for this parameter was almost constant (16 mg DO g-1 VSS min-1) during all sulfide oxidation tests indicating that the maximum specific oxidation capacity of the biomass is independent of substrate and biomass concentration. Results exhibited bacteria prefer to partially oxidized sulfide to elemental sulfur, however this preference is a function of dissolved oxygen and substrate availability.

Absorption and separation of carbon dioxide and hydrogen sulfide from biogas by the metal organic framework MIL-47 have been investigated by using the Monte Carlo method. The simulation results have a good agreement with the available experimental data. At first, the adsorption isotherm of pure, binary and ternary blend of methane, carbon dioxide, and hydrogen sulfide gases were studied. The simulation results show that the gas adsorption increases by decreasing and increasing in the temperature and pressure, respectively, and the pure absorption of hydrogen sulfide gas in the MIL-47 is higher than the other gases. The selectivity of carbon dioxide and hydrous sulfide relative to methane gas calculates 0.2 and 2.9 at ambient temperature and pressure, respectively. Therefore, the metal organic framework MIL-47 is not suitable for the absorption and separation of carbon dioxide gas, but it is good able to separation of hydrogen sulfide from biogas.

In this paper, a two-dimensional mathematical model was presented for the removal of CO2 and H2S in a polypropylene hollow fiber membrane contactor in the presence of MEA. Modeling was performed in both axial and radial directions under the dry condition for countercurrent gas-liquid flow arrangement. To evaluate the model, the results of this modeling were compared with experimental data of removal of CO2 in the presence of water physical solvent and MEA chemical solvent. The results showed that the CO2 and H2S removal efficiency increased with the increase of the liquid flow rate, number of fibers, membrane length, and solvent concentration, but, decrease by increasing gas flow rate because of lower hold up time. It was also found that in low amine discharges, hydrogen sulfide is completely removed. Finally, the results showed that by increasing the wetting, the removal of these gases is reduced.

In the present investigation, the operation of an industrial tray column was evaluated in absorption of hydrogen sulfide by diethanolamine and the effects of processing factors on separation was discussed in detail. In the first step, the absorption process was simulated and the results were compared with the industrial data to validate the calculated method. The role of column pressure, amine concentration, amine inlet temperature and gas flow rate were evaluated on absorption. Although, the increase in column pressure causes to achieve the stream in which the hydrogen sulfide concentration is lower than 0.01 %, the outlet amine temperature increases, negligibly. The rise in amine inlet temperature couldn’t effectively change the operation but amine concentration should be controlled correctly to reach appropriate concentration.

One of issues preventing utilization of sodium hydroxide, as H2S absorbent in this oil/gas industries, is its recovery, because of an irreversible reaction between NaOH and H2S. In this work, ozone and natural zeolite (clinoptilolite) were used for oxidation of sulfide to sulphate ions and adsorption of sulfate ions from alkaline solution, respectively. A synthetic solution of sodium sulfide in sodium hydroxide was prepared. The effect of three operating variables at three levels including ozonation time, hydrogen peroxide dosage, and initial concentration of sodium sulfide was investigated on conversion of sulfide ion to sulfate ion. The design of experiments was performed utilizing response surface method (RSM) in Design Expert software to find optimum condition of oxidation process. Under optimum condition, i.e., ozonation time: 60 min, hydrogen peroxide dosage: 5 mL and sodium sulfide concentration: 0.03 M, a conversion 72.11% was achieved. In the next step of experimental runs and for the removal of produced sulfate ion in oxidation step, an adsorption process using natural zeolite and surface modified zeolite with barium chloride was applied. The highest adsorption efficiency of sulfate ion (91%) was achieved at the highest level of modified zeolite dosage (8 g zeolite/100 mL of solution). Total removal efficiency 65.7% was reported in whole process of oxidation-adsorption, whereas no significant changes in pH were observed. The present method could be a notable alternative to replace ethanol amines with NaOH solution in oil and gas industries.

Hydrogen sulfide (H2S), a by-product often produced in petrochemical processes, is well known as a dangerous and highly toxic gas to living organisms. The smell of H2S concentration of higher than 100 ppm can cause severe biological condition. Therefore, the detection of this gas is a crucial issue. In this work, nanocomposite porous films of polyurethane/silver (PU/Ag) and poly(vinylchloride)/silver (PVC/Ag) consisting of 7 wt% nanoparticles were fabricated by phase inversion method and studied its qualitative detection capacity for H2S. The results indicated that after exposure to 50 ppm H2S, black points appeared on the surface of the test films within 10 min. However, the color completely disappeared when the films were left in the air for 20 min. Structural characteristics of the nanocomposites were studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and thermal gravimetric analysis (TGA) to confirm possible interactions which may have formed between the polymers and nanoparticles. According to the results, Ag nanoparticles were well dispersed in PU and PVC matrices giving particle sizes of less than 62 and 76 nm, respectively. The observations revealed that two recommended nanocomposites (PU/Ag and PVC/Ag) could be used for detection of hydrogen sulfide at low level concentration. The response of Ag-embedded polymer films toward H2S vapour showed a better detection by PU/Ag compared to PVC/Ag. Therefore, the suggested silver nanoparticle-loaded PU and PVC sensor films are easily portable, simple to use and cost-less compared with other types of hydrogen sulfide sensors.

Adsorption of gases is one of the important processes in the oil, gas, petrochemical industries and also environmental protection. In this research, modeling of carbon dioxide and hydrogen sulfide gases adsorption was investigated using metal organic frameworks to obtain adsorption system behavior and adsorption capacity prediction. Three parameters and multilayer isothermal models were used in the modeling. Experimental data of carbon dioxide and hydrogen sulfide adsorption on four metal organic frameworks were used to obtain the model parameters. The correlation coefficient was used to evaluate the models performance. The modeling results showed that the adsorption process of CO2 and H2S was physical and the adsorbents have best performance for carbon dioxide adsorption. Between multilayer models, BET model showed a good agreement with experimental data than other models.

Absorption of hydrogen sulfide with aqueous amine solution is one of the most important processes in refinery units. Tray and packed columns are widely used for removal of hydrogen sulfide. For modeling of these kind equipments, equilibrium and rate-based techniques can be used. Since, the hydrogen sulfide absorption with amine solutions is a reactive absorption; using equilibrium-based models would not attain appropriate results. In this study, the wetted wire column was properly introduced; low pressure experimental setup of hydrogen sulfide absorption with amine solutions was constructed and then different type of experiments were performed. the heat transfer coefficient, the gas phase mass transfer coefficient were determined experimentally based on liquid flow-rate, inlet liquid and gas temperatures, amine weight percent and also hydrogen sulfide loading. Also by assuming laminar liquid film over the wires, velocity distribution and liquid phase mass transfer coefficient were calculated based on liquid flow-rate and mean gas-liquid flow temperatures. For modeling the process the general computer code was created. There is a good consistency between experimental data and simulation results; additionally, the effect of different parameters such as liquid flow rate and gasliquid phase temperature on absorption amount were examined.