bijan hejazi

In the gas sweetening process with amine solution, the amine reacts with acids in the sour gas, anticorrosions, and sour water, producing heat-s table salts. The heat-s table salts in the amine can increase corrosion and amine loss, produce foam, increase operational cos t, and decrease sweetening capacity. Removing the s table salts with different methods is necessary to decrease their negative effects on the process. One of these methods is salt adsorption with ion exchange resins. This method has two main s teps. The firs t s tep is salt adsorption with ion exchange resin and the second s tep is resin regeneration by caus tic solution and then washing the resin bed with indus trial water. The adsorption and regeneration processes happen in a bed that can be fixed or fluidized. In this s tudy, the fixed and fluidized bed performances are experimentally compared for the regeneration and washing s teps of the resin bed which is located in the desalination and chlorination unit of Khangiran gas refinery. The results show that using a fluidized bed for the regeneration s tep has positive effects on the operational parameters of the process. As a result of this change, indus trial water consumption and was tewater production decreased by 28% and resin loss decreased by 20%. The bed pressure drop also decreases from 7 psi to 2 psi. In addition, annual repair and maintenance cos ts are expected to decrease by 66%. The other positive effect of using the fluidized bed ins tead of the fixed bed is the bed channelization reduction which can increase the process performance significantly.

 One of the most challenging aspects of coronavirus disease 2019 (COVID-19) is that a newly infected individual shows diagnosable symptoms, such as body temperature (Tb) rise, several days after contracting the disease. In the early phase of infection (i.e., incubation period), an undiagnosed and unaware individual can spread the virus to others. The fastest and most efficient route of COVID-19 transmission is the respiratory system. Therefore, developing a model of the respiratory system to predict changes in the lung performance upon COVID-19 infection is useful for early diagnosis and intervention during the incubation period.

 This modeling study aimed to evaluate the respiratory system to present an early intervention for COVID-19 and its transmission.

 A simple model was developed by performing mass and energy balances on the lungs; it was simulated by the Aspen HYSYS chemical process simulator.

 To compensate for the virus-infected lung inefficiency, the O2 concentration increased in the exhaled air at the cost of decreased CO2 concentration. Contrary to previous findings on the reduced stability of coronavirus in hot and humid environments, it was found that very hot and humid environments promote the viral transmission rate because of the direct heat transfer to the body via respiration and condensation of water vapor that may cause infection in the respiratory tract.

 Our model revealed that measurement of O2 or CO2 composition of exhaled gas, using a non-invasive and inexpensive device at home, allows for the early diagnosis of infection and its prevention. This study also aimed to highlight the actual effects of high temperature and high relative humidity (RH) on increasing the virus transmission rates, as opposed to the generally accepted hypothesis of decreased coronavirus stability under these conditions.
 

This paper investigates the economic feasibility of installing a turboexpander in parallel with the throttling valve of a city gate station for the purpose of distributed electricity generation through exergy recovery from pressurized natural gas. The preheating requirements for preventing hydrate formation due to pressure reduction are provided by the combustion of a small fraction of the outlet natural gas stream. As a case study, the simulation of Tehran No.2 City Gate Station demonstrates an exergy loss of more than 36.5 million kWh per year for the present throttling valves. Thermoeconomic analyses gives the optimum operating conditions for electricity generation through a turboexpander. Optimization of preheating temperature leads to an exergy recovery of >60%, cost to generate electricity of <$0.04/kWh, and discounted payback period of around ~4 years. Simulation results can be used for designing an automatic preheating temperature control system to optimize exergy recovery via turboexpander under the variable operating conditions of a pressure reduction station.