Modeling Contaminant Transport of Nitrate in Soil Column

Soil forms solution when it is in contact with water or any liquid. This soil solution disperses into the ground in different parts, at different velocities. Hence, the chemical contents of the soil are leached gradually from soil with infiltrating water. Soil parameter characterizing this phenomenon is referred to as Solute dispersivity. The objective of this study is to model contaminant transport of nitrate in soil, calibrate and verify the model derived. Dispersion studies were performed in the laboratory using soil columns filled with silver nitrate (AgNO3) solution. Samples were collected from the column outlet at intervals of 5minutes and the dispersion coefficient calculated. The dispersion coefficient calculated was incorporated into existing Notordamojo’s model and solved. Results obtained from the research showed that the R2values ranging from 0.741 to 0.896 and 0.484 to 0.769 were obtained for the modified model and the existing Notordamojo’s model respectively. The model verified with the experimental data showed predicted transport was in close agreement with experimental values having coefficient of correlation (r) ranging from 0.86 to 0.98. The difference between the experimental and predicted results, when expressed as a percentage of the experimental value was less than 5%. The study has established that the modified model which accounted for variability in dispersion coefficient offered a better approach than the conventional one. Doi: 10.28991/esj-2021-01290 Full Text: PDF

EVALUASI KINERJA METHYL DIETHANOL AMINE (MDEA) DALAM PENYERAPAN KANDUNGAN H2S PADA PROSES PENGOLAHAN GAS ALAM

Drilling natural gas contains water vapor (H2O) and contaminant gases such as CO2 and H2S which must be removed because it reduced the calorie value of the product. H2S gas is also corrosive, easily damaging equipment so that it increased maintenance costs. The process of removing CO2 and H2S gas uses MDEA (methyl diethanolamine). This study aims to determine the optimal concentration and flow rate of absorbent methyl diethanolamine (MDEA) to absorb H2S in the plant I gas flow in Energy Equity Epic (Sengkang) Pty.Ltd. The study was carried out with a steady MDEA mix absorbent flow rate (50% pure amine and 50% demineralization water) fixed at 13 US Gallons per minute flowing continuously at the upper absorber inlet, sour gas flow rate, at the bottom of the absorber inlet with variations in the flow gas namely 7,9,11,13,15,17 MMSCFD and is contacted with amine solution counter-current. Purified natural gas (sweet gas) produced from the top absorber column outlet with an H2S content below 10 ppm. The results showed that the greater the flow rate of gas inlet, the greater the acid gas absorbed. The amount of gas entering and exiting gas follows the equation y = 0.003 x - 2.2537. The ability of the amine solution to absorb H2S follows the logarithmic equation y = 0.167 ln (x) + 101.02 with a value of R = 0.9857, y is H2S absorbed by the amine solution and x is the H2S rate.

CFD study on the effects of different temperatures and feed velocities for CO2, CH4, and C2H4 adsorption using 5A molecular sieve

The removal of carbon dioxide (CO2) from natural gas is a practical measure in dealing with problems such as CO2 emissions into the atmosphere and reducing the cost of gas processing operations. Adsorption is a promising technology currently used, specifically pressure swing adsorption (PSA) method. In this paper, the adsorption column packed with 5A molecular sieve was simulated using COMSOL Multiphysics software for the separation of CO2 from natural gas components, which are methane (CH4) and ethylene (C2FLi). The effects of different temperatures on adsorption time were investigated and the optimum adsorption time was determined by the purity of CH4 and C2H4 at the column outlet. This study will be beneficial for optimising the design and process configuration of PSA.

Effect of Interstitial Velocity on the Adsorption of Bacteria onto Soil

The adsorption of bacteria onto soil is affected by the physical and chemical characteristics of the soil and water, the size and morphology of the bacterial cells, and the water-flow characteristics in the soil. The present study focuses on the latter factor by investigating the effect of the interstitial velocity on the adsorption of bacteria onto soil. Columns of 10 cm diameter and 130 cm height, respectively, were packed with a sandy soil. The columns were saturated with water containing nalidixic acid-resistant Escherichia coli as a bio-tracer at three different pH levels. The columns were maintained at 20°C for 24 h before connecting the column outlet to its inlet by a pump in a closed loop. Water containing the biotracer was re-circulated through the column for another 24 h at three different interstitial velocities. Water samples were taken from a sampling tap connected to the pump at 4-h intervals. These samples were analyzed to determine the biotracer concentration. The results show that more biotracer cells were retained in the soil at the lower interstitial velocity. The higher interstitial velocity resulted in higher shear forces which caused more desorption of the biotracer cells from the surfaces of the soil particles. Bacterial adsorption was higher at the acidic pH value. The survival of the biotracer cells in soil solution was also tested at three different pH levels. The results show that no decline in the biotracer concentration occurred during the test period.

A Simple Probabilistic Model of Bubble Column

A probabilistic model of bubble column was derived from a deterministic model so that noncorrelated or autocorrelated noise was added at the column outlet. A pseudo-random binary series of maximum length - PRBS was used as input signal The effect of noise was observed in terms of impulse characteristics calculated by the correlation method from the responses of model to the PRBS input. The possibilities of PRBS when simulating the behaviour of bubble column were judged in the work, and the effect of magnitude of noise amplitude on the form of impulse characteristics was evaluated.

Comments On the Effect of Gas Velocity On Oxygen Index Measurements

For certain materials, the velocity of the mixed gas stream used in an oxygen index determination has been reported to exert a strong influence on the ex perimental result. It is now possible to rationalise these reported dependences which are shown to result from the form of column used in the test. A proposed modification to the column outlet eliminates the dependence of oxygen index on gas velocity over the range of gas velocity permitted by the testing standards.