Search

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℃ 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℃ 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.

Fosforoz asit ve potasyum hidroksitin ekzotermik nötralleşmesi tepkimesi sonucu oluşan monopotasyum fosfit ve dipotasyum fosfit tuzlarının üretiminde kullanılacak reaktör sistemin geliştirilmesi için tepkimeye ilişkin bilinmeyen unsurların saptanması, tepkimenin gerçekleştirileceği reaktörün ve işletim türünün, stokiyometrik oranın tespiti gerçekleştirilmiştir. Reaksiyon kinetiğinin bulunması için farklı derişim oranlarında fosforoz asit ve potasyum hidroksit çözeltileri hazırlanarak deneyler yapılmıştır. Tepkimeyle açığa çıkan ısının işletim türüyle ilişkisini incelemek için deneyler yarı-kesikli, kesikli ve sürekli işletim türlerinde gerçekleştirilmiştir. Ekzotermik reaksiyon sonucu oluşabilecek patlama, sıçrama gibi durumların etkisini gözlemleyebilmek, ürün spesifikasyonlarını değerlendirmek için deneyler asit üzerine baz ve baz üzerine asit beslemesi şeklinde gerçekleştirilmiştir. İki deney setinde de bir farklılık olmadığı saptanmıştır. Aynı zamanda yapılan deneyler sonucunda tepkime stokiyometrisinin 1:1.5 (asit:baz) molarite oranında gerçekleştirilmesi gerektiği ortaya konulmuştur. Yarı-kesikli reaktör sistemi yerine borusal bir reaktör sisteminde girdilerin reaktör boyunca belirli aralıklarla beslenmesini ve böylece ani patlama, sıçrama, sıcaklık yükselmesi ve reaksiyon hızının önüne geçilmesini sağlayacak aynı zamanda da bu besleme yöntemiyle ürün verimliliğini artırmayı amaçlayan bir borusal reaktör tasarlanmıştır. Deney sonucunda istenilen pH değeri olan 6.5 civarına ulaşılmış, reaktör içerisindeki sıcaklık kontrol edilebilmiş, istenen derişimlerde potasyum ve fosfor içeren ürün elde edilmiştir.

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.

Hydrogen can be produced via dark and photo-fermentation using either single-stage or two-stage processes. The advantage of a two-stage system is that it is possible to separately optimize and control culture conditions for the dark and photo-fermentative bacteria. In the present study a mixture of starch and glucose was used as carbon source for the dark fermentation step. Response surface methodology (RSM) with a Box-Behnken design (BBD) was applied to the photo-fermentation stage for the optimization of key parameters: inoculum concentration (Rhodopseudomonas palustris), substrate concentration (dark fermentation effluent (DFE)) and pH. In this sequential two-stage system, the highest overall hydrogen yield (8.3 ± 0.1 mmol H2/gCOD), overall hydrogen production (1.62 mmol) and the photo fermentation yield (7.21 ± 0.2 mmol H2/gCOD) were achieved at inoculum of 9 mL (1.64 ± 0.7 × 108 cells), a DFE dilution of 2.5× and a pH of 7.5, which were center points of the design. 97% COD removal was achieved at the highest dilution of DFE (lowest concentration of carbon source) at pH 6.5.

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 H 2 /L) was achieved at the highest substrate concentration (5 g/L); however, the highest hydrogen yield (3.84 mol H 2 /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.

Biological hydrogen production is under extensive investigation worldwide and has attracted the interest of researchers in a number of disciplines including the fundamental sciences, e.g., microbiology and biochemistry, and the applied sciences, e.g., chemical engineering. While the multidisciplinary approaches being used have been very fruitful in terms of advancing biohydrogen research, the data sets rapidly accumulating in the published literature are often difficult to compare due to the use of different units, or the incomplete description of experimental conditions. Here we review some of the common methods that are used in various aspects of biohydrogen research and suggest ways of reporting data that enable conversion to other units and comparison with similar research being carried out elsewhere. In addition, we have compiled in one place common abbreviations and definitions as well as useful physical/chemical constants and laws pertaining to hydrogen. Unlike other reviews that examine the results of specific studies, or describe the different systems being deployed and compare them, here we provide in one place for the first time a detailed listing and description of the up-to-date methods used in measurement and quantification of biohydrogen production. Useful conversion factors and physical constants are also given.

Bu calismada oksijensiz kosullarda patates besi ortaminda Clostridium butyricum mikroorganizmasi kullanilarak biyohidrojen uretilen kesikli biyoreaktorlerde calkalama hizi, mikroorganizma aktarim orani, baslangic substrat derisimi ve inkubasyon sicakligi parametrelerinin biyohidrojen uretimine etkisi incelenmistir. En uygun parametreler sirasiyla, calkalama hizi 200 devir/min, mikroorganizma aktarim orani 1:10, baslangic substrat derisimi 32,4 g KOI/L ve sicaklik 37 o C mikroorganizma aktarim orani olarak belirlenerek, bu kosullarda 1257 ml H 2 uretilmistir. Inkubasyon sicakliginin 37 o C oldugu durumda gecikme fazinin baslangic substrat derisiminden bagimsiz olarak yaklasik 6,5 h surdugu gozlenmistir. Substrat derisimi ile urun uretimi arasindaki iliski degerlendirilirken elemanter tepkime hiz modeli icin tepkime mertebesi 1, tepkime hiz sabitleri ise 28 oC ve 37 oC sicakliklar icin sirasiyla 6,5x10 -5 min -1 ve 7,92x10 -5 min -1 olarak hesaplanmistir. Arrhenius modelinin sabitleri, Arrhenius katsayisi 9,74x10 34 min -1 ve aktivasyon enerjisi 229,20 kJ/mol olarak hesaplanmistir. Michaelis-Menten modeli ile maksimum H 2 uretim hizlari 28 oC ve 37 oC sicakliklar icin sirasiyla 0,01147 L H 2 /L.min ve 0,07466 L H 2 /L. min, bu sicakliklar icin Michaelis sabitleri (K M ) sirasiyla 181,9 g KOI/L ve 447,7 g KOI/L, R 2 degerleri ise 0,9458 ve 0,9505 olarak hesaplanmistir. Modifiye Gompertz modeli ile R 2 degerleri tum calismalar icin 0,99’dan buyuk olarak elde edilmis, en yuksek H 2 uretim potansiyelleri 28 oC ve 37 oC sicakliklar icin 32,4 g KOI/L baslangic substrat derisiminde sirasiyla 2,126 L H 2 /L ve 2,777 L H 2 /L olarak bulunmus, en yuksek H 2 uretim hizina 0,01525 L H 2 /L.min ile 37 oC sicaklik ve 27 g KOI/L baslangic substrat derisiminde ulasilmistir.

Hydrogen yields of dark fermentation are limited due to the need to also produce reduced side products, and photofermentation, an alternative, is limited by the need for light. A relatively new strategy, dark microaerobic fermentation, could potentially overcome both these constraints. Here, application of this strategy demonstrated for the first time significant hydrogen production from lactate by a single organism in the dark. Response surface methodology (RSM) was used to optimize substrate and oxygen concentration as well as inoculum using both (1) regular batch and (2) O2 fed batch cultures. The highest hydrogen yield (HY) was observed under regular batch (1.4±0.1molH2/mollactate) and the highest hydrogen production (HP) (173.5µmolH2) was achieved using O2 fed batch. This study has provided proof of principal for the ability of microaerobic fermentation to drive thermodynamically difficult reactions, such as the conversion of lactate to hydrogen.

A detailed system identification procedure and self-tuning generalized minimum variance (STGMV) control of glucose concentration during the aerobic fed-batch yeast growth were realized. In order to determine the best values of the forgetting factor (λ), initial value of the covariance matrix (α), and order of the Auto-Regressive Moving Average with eXogenous (ARMAX) model (n a, n b), transient response data obtained from the real process wereutilized. Glucose flow rate was adjusted according to the STGMV control algorithm coded in Visual Basic in an online computer connected to the system. Conventional PID algorithm was also implemented for the control of the glucose concentration in aerobic fed-batch yeast cultivation. Controller performances were examined by evaluating the integrals of squared errors (ISEs) at constant and random set point profiles. Also, batch cultivation was performed, and microorganism concentration at the end of the batch run was compared with the fed-batch cultivation case. From the system identification step, the best parameter estimation was accomplished with the values λ = 0.9, α = 1,000 and n a = 3, n b = 2. Theoretical control studies show that the STGMV control system was successful at both constant and random glucose concentration set profiles. In addition, random effects given to the set point, STGMV control algorithm were performed successfully in experimental study.

In this work inoculation media are selected as potato, glycerine and milk to investigate the best storage condition that is important to maintain microorganism activity and stable hydrogen production performance. Cheese whey, potato and enriched potato (with additional glucose and CaCO3) are used as the production media and their hydrogen production results are compared in order to determine the best biohydrogen production media. Batch growth of anaerobic Clostridium butyricum for biohydrogen production is performed in 500 ml screw-capped bottles at 28°C. It is noted that both the inoculation and the production media are highly effective on hydrogen production. Results show that the highest hydrogen production yield is obtained as 50.50 ml H2/g COD using milk as inoculation medium and enriched potato as production medium. Another important production factor is the production rate and when the results of three different inoculation media are compared for different production media, milk inoculation and enriched potato production media give the highest results as 41.9291 mL/L.h.