This study investigated the effects of electrical parameters of a corona discharge reactor on the partial oxidation of methane in air and on carbon dioxide reforming with methane in the presence and absence of Pt loaded KL zeolite (Pt/KL). The experiments were conducted over a wide range of applied frequency (200–800 Hz) and input low side voltage (32–72 V). For partial oxidation of methane, the reactant conversions increased with decreasing applied frequency and increased with input low side voltage both in the presence and absence of Pt/KL except that the oxygen conversion was 100% in the presence of Pt/KL. Compared to the corona discharge in the absence of Pt/KL, the presence of Pt/KL resulted in higher oxygen conversion but lower methane conversion. In the absence of Pt/KL, the CO/C2 and H2/CO ratios were constant of about 12 and 1.8 at high current but in the presence of Pt/KL, the CO/C2 and H2/CO ratios both increased with decreasing applied frequency and increasing input low side voltage. For carbon dioxide reforming with methane, applied frequency and input low side voltage affected only reactant conversions with no significant effect on reaction pathways both in the presence and absence of Pt/KL. The combination of catalyst and corona discharge had no strong effect on carbon dioxide reforming with methane.
A steady-state model incorporating interactions between separate bubbles and emulsion phases in a fluidized-bed polyethylene reactor is employed to study the effect of operating conditions on the stability of gas-phase polyethylene reactors. A simple optimization program is developed to find the optimum combination of operating parameters at which the maximum polyethylene production rate is achieved with the constraints only on the reactor temperature, which should not exceed the melting point of polymer. Using the optimum values found, the parametric investigation for the effect of the catalyst deactivation rate constant and process operating parameters, such as the catalyst feed rate and the gas superficial to minimum fluidization velocity on system behavior are investigated. The investigations reveal that, the fluidized bed polyethylene reactor is prone to show unstable behavior and temperature oscillations, and the optimum polyethylene production rate could be achieved when it operates close to its melting point under a suitable controller to avoid polymer melting.
A study on temperature control of a free-radical polymerization continuous stirred tank reactor (PCSTR) system was carried out subject to physical input constraint and output multiplicity. Strong thermal effects tend towards operation with stability margins, and process states are unavailable in the real-time evaluation. First, nonlinear control algorithms derived from the state-space formulation of model-based controller design for nonlinear relative-degree-one and relative-degree-two systems are addressed. Second, modified PI- and PID-types control frameworks with the aid of the equilibrium-based design are developed. In addition, the tuning procedures of controllers are relatively simple and straightforward, and the low-and-high gain technique connected to anti-reset windup design is used to enhance the process control performance.
The cascade control technology has been widely implemented through the industries. The focus of this paper is the assessment of a parallel cascade control system scheme against an achievable performance standard. Following the methodology of the univariate control loop performance, a procedure is derived based on the minimum variance and the Diophantine decomposition for the parallel cascade control system. The performance bound is computed using the minimum process variances which depend on the controllers. Besides, the achievable performance bound and the corresponding optimal parameters of the PID controller structure computed from the closed loop operating data are also proposed. It can assess the performance of the current given controller. If the cascade controllers are not operating at the achievable bound, the reduction of the output variability can be achieved based on the estimation of the controller parameters of the PID-achievable performance. The performance of the proposed method is illustrated through a simulation problem and a pilot scaled experiment.
This paper presents a practical identification method of the linear part of a plant which has nonlinearity in its input. A Hammerstein-type model is used for the plant model and only the linear dynamic part is identified independently of the input nonlinear element by restricting the manipulated variable to take only two values during the identification experiment. The identification signals are generated using a kind of limit cycle test modified to produce fractional harmonic components in the signals. A second order lag plus an all-pass filter is used for the linear model and its parameters are calculated to fit the model frequency responses to the ones obtained by the limit cycle test at two frequencies. A numerical example is presented and adequateness of the model structure is discussed.
Reactivities of bio-related molecules with active oxygen species were measured by the sonochemical luminescent (SCL) method proposed in our previous paper. Sixteen kinds of amino acids, four kinds of nucleobase-model compounds and α-tocopherol as a typical antioxidant compound were measured by the method. Among the amino acids, L-tyrosine, L(–)-phenylalanine, L-tryptophane, L(–)-cystine were found to be more reactive than the others. Among the nucleobase-model compounds, purine bases exhibited higher reactivity than pyrimidine ones. α-Tocopherol was examined while dissolving it as the micellar solution because of its low solubility in water. To evaluate the reactivity of α-tocopherol itself, the reactivities of surfactants used to prepare micellar solution were also measured, and cetyltrimethylammonium bromide was found not so reactive as obstructing the measurement of α-tocopherol’s reactivity. The experiments in the micellar solution showed high reactivity of α-tocopherol. On the basis of these results, application of the proposed method to the evaluation of antioxidant reactivity was discussed.
A recent development in heat insulating materials offers decreased energy consumption for air-conditioning and an improvement in the thermal performance of the insulating glass in windows and the openings of houses and buildings. In insulating glass, the use of a resin spacer, rather than an aluminum spacer, is useful for improving insulation efficiency, but water vapor is still transmitted into the air space of the insulating glass, leading to dew condensation and decreased transparency. The lifetime of resin spacers is predicted by the diffusion coefficient of water vapor without knowledge of the dew point of the insulating glass. The amount of water adsorbed in various resin spacers of polyisobutylene with zeolite 4A was measured at temperatures of 40–80°C and relative humidities of 15–95% at atmospheric pressure from one hour up to one month. In this study, the relationships between the lifetime of the insulating resin, the adsorbed amount of water, and the optimum resin spacer components for increased lifetime are discussed. In addition, a diffusion model for the transmission of water into the air space is proposed.
The chlorine in polyvinyl chloride (PVC) originates from sodium chloride separated by electrolysis consuming a large amount of electricity. On the other hand, approximately 1/2 of soda ash, which is made from sodium chloride, is used for manufacturing soda glass. To show the potential of utilizing waste PVC and waste glass that have been mainly disposed as landfill, in the present work, it is experimentally demonstrated with a laboratory scale fixed bed reactor that most of the chlorine generated from PVC can be neutralized by sodium in waste glass particles forming NaCl in the range of 450–550°C. SEM and EDS studies confirmed the crystallized salt on the surface of glass particle after the reaction. Chlorine content in char was lower than NEDO’s RPF (refused plastic/paper fuel) target value for coal alternatives indicating that the product char can be readily combusted with little potential of corrosion of downstream units and toxic organic halides emissions. Closing the nationwide sodium and chlorine material flows can be conducted by reacting waste PVC with waste glass.