Search

PID control, which is a type of automation, was used to ensure that neutralization takes place in a controlled manner. To determine the PID parameters of the system with the Cohen-Coon tuning method, two different dynamic experiments were carried out for pH and temperature in the first stage, and the transfer function and model parameters were found. In the experiment carried out for the pH variable; time constant (τ) is 59 s, dead time (Ɵ) is 261 s and steady state gain (K) is read from the graph as 14,72, while PID parameters are calculated as KC =0.0375, τI =315.759 s and τD =52.601 s. Likewise, while τ=1402 s., Ɵ= 88 s, and K=-6 were read for the temperature variable, the PID parameters were calculated as KC =6.196, τI =47.23 s, and τD =-19.20 s. The determined controller parameters were used as initial parameters and simulated using the Sfunction block via MATLAB (2007b). The pH set range was coded as 6.5-8.5 and Tset for temperature was coded as 22 °C. As a result of the oscillation observed due to the nature of the PID control parameters that are intended to be controlled, the safe operation of the process and the desired set values are ensured. When the obtained PID controller parameters were applied to the neutralization reaction, the PID control successfully controlled the reactor temperature and pH and eliminated possible hazards in operation. Anti-windup provides better control rather than traditional PID control method. [ABSTRACT FROM AUTHOR]

The phosphorous acid salts are widely used in the industry because of the effective treatment against various fungal diseases encountered in plants. The production process is exothermic and, with high temperatures around 94°C achieved, significant risks were observed in terms of occupational health and safety. Therefore, the aim is to design a control system that will make this production process reliable for human health, economic and ecological damage. For this purpose, studies were carried out to determine the optimum operating mode, heat transfer system, and temperature controller design to prevent a sudden temperature rise. First, the overall heat transfer coefficient between the reactor and the jacket was determined as 51.0930 W/m²°C and, the refrigerant was chosen as cooling water with 1.271 g/s flow rate which is relatively more economical and accessible. The model parameters of the system were determined with a detailed dynamic analysis by giving positive and negative step inputs to the cooling water flow rate and then obtaining model parameters through reaction curve and linear regression methods. By using the obtained model parameters theoretical P, PI and PID parameters were calculated by Cohen Coon and, Ziegler-Nichols approaches, and the success of controller parameters was tested, simulated with the MATLAB Simulink program and lastly, successful temperature control was achieved in the experimental system. [ABSTRACT FROM AUTHOR]

Both dark and photo-fermentation can be used for biological hydrogen production; either performed separately, in two-stage systems, or in co-culture. A single stage process is less laborious and costly; however, the two types of microorganisms have different nutritional requirements requiring optimization of culture conditions. Here a response surface methodology (RSM) with a Box-Behnken design was used to optimize microorganism ratio and substrate and buffer concentrations, and to evaluate their interactive effects for maximization of hydrogen yield. Clostridium butyricum and Rhodopseudomonas palustris were grown on a potato starch/glucose base medium at 30 °C under continuous illumination (40 W m−2 light intensity). The highest hydrogen yield, 6.4 ± 1.3 mol H2/mol glucose, was obtained with a substrate concentration of 15 g/L, buffer concentration of 50 mM, and microorganism ratio of 3. The observed strong interaction between buffer and substrate concentration is most likely due to the need to optimize the pH for co-cultures. [ABSTRACT FROM AUTHOR]

Biohydrogen production from cellulose by a bacterial co-culture is a potentially promising approach for producing bioenergy from a low cost substrate. The use of a cellulolytic bacterium, Cellulomonas fimi, permits cellulose conversion and the in situ production of substrate for growth and hydrogen production by the photosynthetic bacterium Rhodopseudomonas palustris. Response surface methodology (RSM) with a Box-Behnken design (BBD) was used to examine variations in the key parameters: substrate (cellulose) concentration, yeast extract concentration and the microorganism ratio (Rps. palustris/C. fimi). For the co-culture of R. palustris and C. fimi the highest hydrogen production (44 mmol H2/L) was achieved at the highest substrate concentration (5 g/L); however, the highest hydrogen yield (3.84 mol H2/mol glucose equivalent) was observed at the lowest cellulose concentration and highest microorganism ratio. High COD removal efficiencies, over 70%, were achieved over a wide range of conditions and were positively affected by the concentration of yeast extract. [ABSTRACT FROM AUTHOR]

This study proposes that the on-line pH control via a model-based adaptive controller markedly improves the dark fermentative hydrogen production. According to the dynamic behavior of the dark fermentation process, pH, which rapidly declines with the beginning of the biogas production, should be precisely controlled around its optimal value in a narrow range. The success of on-line pH control was guaranteed by performing the preliminary simulation studies by experimental data obtained from dynamic analysis to determine ARMAX model order with Recursive Least Squares parameter estimation method and then to control the pH with Generalized Minimum Variance (GMV) controller. On-line control of pH at the optimal value of 6.0 during the 25 h dark fermentation process resulted in 5.4 times higher biogas production, 6.2 times higher biogas production potential, nearly doubled the duration of fermentation, and 18.4% biogas production rate increment in comparison with the uncontrolled pH case. Image 1 • First on-line System Identification and Generalized Minimum Variance Control (GMV) application on biohydrogen production. • Effective hydrogen production by dark fermentation with on-line pH control. • Higher biogas production was achieved compared to uncontrolled fermentation. • PH control nearly doubled the duration of fermentation. [ABSTRACT FROM AUTHOR]