GAS PROCESSING
Year:2016 | Volume:4 | Issue:1|Papers Count:5

Natural gas is associated with nitrogen and heavy compounds. These heavy components in the natural gas not only can feed downstream units, owing to the low temperature process, but may be formed solid as well. Heavy components separation is a necessity and can they produce useful products. All natural gases contain nitrogen which lower theirheating value. Removing nitrogen from natural gas at a concentration of more than 4% is essential. Integration of the natural gas liquids (NGL), liquefied natural gas (LNG) and nitrogen rejection unit processes is an effective procedure which can reduce the required refrigeration. A new mixed fluid cascade natural gas liquefaction process is assessed here through the exergy and exergoeconomic analysis methods. One of the vapor compression cycles is replaced with a water-ammonia absorption refrigeration cycle. The results include cost of exergy, exergoeconomic factor, exergy and exergy efficiency. Results of exergoeconomic analysis indicates that the maximum exergoeconomic factor, 89.49%, is related to the HX8 in the water-ammonia absorption refrigeration cycle and the minimum exergoeconomic factor, 0.0026%, is related to the HX2 in the liquefaction cycle. In this process, the fourthcompressor has the highest exergy destruction cost of (5750307$/hr) and HX8 in the absorption refrigeration cycle has the lowest exergy destruction cost of (2.033 $/hr). Due to the high value of fuel cost in compressor, their exergy destruction cost is much higher than other devices.

How CO2 and H2S are removed from a natural gas stream, through a nanofluid containing nanoporous graphene in Diehanolamine (DEA) is revealed. The appropriate values are chosen for the nanosheet dosage and the liquid and gas flow rates to be applied in the absorption experiments. These experiments are run in a laboratory scale wetted wall column. The nanosheet concentration is within 0.005 to 0.5 wt% range. The surfactants and ultrasonic treatment is administered to prepare stable nano-fluids. It is found that applying nanoporous graphene in DEA has a significant affect on CO2 and H2S absorption in comparison with DEA. The absolute zeta potential values of nanofluids are greater than +35 mV. The effect of different parameters including nanosheet, CO2 and H2S concentrations, in the feed gas stream (two different samples) on simultaneous absorption of H2S and CO2 from CO2-H2S-CH4 gas mixture is studied. By processing sample #1, abstract i.e, an improvement in CO2 absorption to 39% and H2S absorption up to 9% is observed at 0.1 wt% of nanoporous graphene/DEA nanofluids.

For energy saving retrofit projects, its economics are usually evaluated in terms of capital investment and payback time. The capital investment is in direct relation to the total heat recovery area of the network and the payback time factor is base on both the area and the energy savings. The debottlenecking is an increased throughput, which can be profitable in economic sense. The combination of these two different objectives leads to a new definition of payback time, which differs, from the simple payback of savings to investment ratio. The correlation among area, energy savings and throughput increase is assessed based on pinch technology. The variation in energy savings and network area with throughput increase considering both economic factors of investment and payback time is reflected in the results. The decomposition approach is implemented as well, and its contribution in rapid detection of the most economical opportunity of network debottlenecking is discussed and the findings are diagramed separately. A visual software code is developed and validated in this study.

Different flow patterns of downward gas-liquid two-phase flow using simple mixer are studied in an experimental manner. An experimental setup is designed and fabricated to allow the visual observation of downward two-phase flow patterns and their transitions. The flow patterns are recorded by a 1200 frames per second high speed video camera. The quality of downward two-phase flow patterns photos are improved through image processing. The setup includes a transparent vertical pipe of 50 mm diameter and the (L/d) aspect ratio of 80. Flow patterns are obtained through 374 test cases during which air and water superficial velocities changed. In order to assess the performance of the mixer, all expected flow patterns are obtained. The four observed flow regimes are: of falling film, bubbly, slug and froth. The flow map is plotted and transitions among different flow patterns are compared with previous finding in specified conditions indicating a good agreement was observed.

The propylene production with 1-butanol co-feeding for methanol in relation to propylene process (MTP) at 440-490oC temperature range and at 0.9-15 hr-1 WHSV range over H-ZSM-5 zeolite catalyst is assessed in a isothermal fixed-bed reactor. The feedings here are of: pure 1-butanol, pure methanol and a 1-butanol and methanol mixture. The effect of 1-butanol co-feeding on selectivity of propylene is assessed through RSM an experimental design method. The results indicate that the selectivity of propylene is 69% in the feed mixture of 13, 37 and 50 wt% of 1-butanol, methanol and water, respectively. The optimum conditions to obtain high level of propylene selectivity is suggested to be at 480oC, WHSV of 0.9 hr-1 and 1-butanol concentration of 0.135 wt.% through RSM method. The sensitivity analysis of the RSM method reveals that the WHSV is the most effective parameter on the propylene selectivity with a P-value of 0.003.