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Modeling and simulations of a reformer used in direct reduction of iron
Abdelhamid Ajbar,Khalid Alhumaizi,Mustafa Soliman 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.12
This paper presents a detailed modeling and simulations of a reformer unit used in the direct reduction of iron (DRI) process. A one-dimensional heterogeneous model for the catalyst tubes which takes into account the intraparticle mass transfer resistance was developed, while the furnace was modeled with bottom firing configuration. Validation against data from a local iron/steel plant showed satisfactory results. The performance variables of the unit were the process gas temperature, wall temperature and conversions of hydrogen, methane and carbon dioxide. The profiles of these output variables along the distance were calculated. The effect of operating parameters such as inlet temperature,natural gas flow rate and gas composition was also determined.
Control of molecular weight distribution of polyethylene in gas-phase fluidized bed reactors
Mohammad Al-haj Ali,Emadadeen Ali AbdelHamid Ajbar,Khalid Alhumaizi 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.1
This paper presents a feasibility study of the broadening of polyethylene molecular weight distribution produced using a multisite Ziegler-Natta catalyst in a fluidized-bed reactor. A nonlinear model predictive control algorithm,applied to a validated model of the reactor, is used for the on-line control of the entire molecular weight distribution of the produced polymer. Control of a target chain-length distribution is achieved by selecting a collection of points in the distribution and using them as set points for the control algorithm. An on-line Kalman filter is used to incorporate infrequent and delayed off-line molecular weight measurements. Through simulation the control algorithm is evaluated, under tracking conditions as well as plant-model mismatch. The results demonstrate that the control algorithm can regulate the entire molecular weight distribution with minimum steady state error. However, the efficiency of this approach is highly dependent on the dynamics of hydrogen inside the reactor.