نشریه مهندسی گاز ایران
پیاپی 4 (شهریور 1395)

Generally, gasoline product from a catalytic reformer is sent to hydrogenation units for separation of benzene and its derivatives from gasoline. Indeed, to produce desirable products, we need to inject hydrogen at hydrogenation unit. Because whole gasoline is sent to hydrogenation unit, the hydrogen consumption will increase. As a suggestion to decrease hydrogen demand, we can design a separation system as Three Product System )TPS) for catalytic reformer. By the new designed system, initially we can separate C6 fractions from output gasoline and then solely sending C6 fraction to hydrogenation unit to reduce hydrogen’s requirement. In this article, different types of TPS are discussed and the performance of these units along with design costs and energy consumption are estimated. Ultimately with comparing of their performance, optimum separation system has been suggested for case study.

Pressure liquefied gas storage tanks are always at risk of fire and explosion. Review of past events shows that the worst and the most tragic incident occurred during storage of pressurized liquid gas, is “boiling liquid expanding vapor explosion”. Most of boiling liquid expanding vapor explosion occurred in a tank surrounded by fire. The fire prevention around the tanks and periodic inspections are two main methods for pressure liquefied gas tanks safety. Periodic inspections of tanks significantly help prevention of leakages in tanks and pipes it.

Associated Gas with crude oil containing hydrogen sulfide, and amine solutions should be used to sweeten it. The genetic/quadratic search algorithm )GQSA) is a hybrid genetic algorithm )GA) for optimizing plant economics when a process simulator models the plant. By coupling a regular GA with an algorithm based upon a quadratic search, the required number of objective function evaluations for obtaining an acceptable solution decreases significantly in most cases. The GQSA combines advantages of GA and quadratic search techniques, e.g. determining a global optimum for a problem with a high probability for discontinuous as well as non-convex optimization problems while at the same time providing faster convergence than conventional GA. The performance of both the GQSA and the GA was compared using four different test functions and an economic optimization problem for a turbo-expander process. Numerical test results indicate that the convergence of the GQSA is either better than or at least comparable to those of GA for all tests employing the same genetic parameters. Also, the results show that the high concentration of ethanol amine increase acid gas absorption, power, steam and water consumption and thus operating costs increase. Also, high temperature of the inlet amine decreases the H2S absorption. It also reduces power consumption and increases the amount of makeup water and ultimately reduces operating costs. Increase the amount of circulating amine and overhead stream from the tower increase the acid gas absorption, electricity consumption and the operational cost.

Processing the sour gas is one of the main methods for production of sulfur in the country and worldwide. In this way, during the sweetening process, sour gases such as hydrogen sulfide are separated from the gas flow and processes in different units. Claus unit is one of these main sections. The output product of this unit is not pure and requires further degassing before introducing to the market. The degassing methods are generally taken in catalytic and non-catalytic approaches. In this paper, different degassing techniques have been described in addition to investigating the advantages of catalytic methods and the optimum method is finally introduced.

In order to prevent environmental polution and production of elemental sulfur, the acid gases outcoming from the oil and gas refineries is converted to elemental sulfur in Sulfur Recovery Units )SRUs). Tail Gas Treatment Units )TGT) are applied at the end of SRU for more processing of tail gas. These TGT units enhance low recovery of sulfur from 96% to over 99%, and therefore, respect to environmental regulations in term of fatal SO2 emission. The temperature of outlet gas from TGT reactor should be decreased to a proper value. Fot this purpose, a cyrculation water together with a cooling column system or a air cooler can be considered. In this paper, a typical industrial unit of sulfur recoveryr equiped with tail gas treatment was considered and for these two cases, the required equipment were designed and the construction and operational costs were compared. The results show that using cooling column has lower construction cost than using air cooler system, but the operating cost is more than operating cost of air cooler.

Molecular diffusion of solution/non-equilibrium gas between oil within the matrix blocks and fracture system in the gassing zone is an important production mechanism of naturally fractured reservoirs. In well-to- moderately fractured reservoirs, the process of molecular diffusion, due to convective currents in the fissures will be active and large volumes of gas would be transported to the gas cap as reservoir pressure declines and consequently results in bubble-point pressure depletion of the oil zone. Conversely, in gas injection scenarios, molecular diffusion can transfer the gas of the gas cap to the matrix blocks and increases the bubble-point pressure of the oil. In order to evaluate the contribution of molecular diffusion in oil production of fractured reservoirs, production history of Haft-kel field was analyzed. Gas-in-place calculations indicated that in case of diffusion, extra oil of about 16.5 percent of the total recoverable reserve is produced during primary natural depletion period )20 years) of the reservoir. In other words, in the case of non-inclusion of molecular diffusion, material balance calculations overestimates oil displacement efficiency by water than that by gas to a value equal to amount of transported gas to the gas-invaded zone of the reservoir by diffusion process.