Exergy-Based Investigation of Hydrogen Production via Aluminum Chloride (AlCl₃)-Based Chlor-Alkali Electrolysis

Öz

In this study, an electrolysis system based on aluminum chloride (AlCl₃) was designed as a potential alternative to the conventionally used sodium chloride solutions in chlor-alkali processes. The exergy performance of the system was experimentally investigated under varying temperature and cell voltage conditions. The experimental setup was tested at a constant electrolyte flow rate of 0.3 g/s, with temperature levels of 20 °C and 45 °C, and cell voltages of 5.0 V, 7.5 V, and 10.0 V. In the laboratory-scale cell used in the study, the anode and cathode compartments were separated by a Nafion 212 membrane, which allows the selective passage of Al³⁺ ions. Five graphite electrodes were employed in each compartment. Since the effect of electrolyte flow rate on hydrogen and chlorine gas production was found to be negligible, it was kept constant throughout the experiments. During operation, the generation of reactive chlorine at the anode side led to chemical degradation of the electrode surfaces, resulting in lower chlorine output compared to hydrogen production. According to the experimental findings, the lowest hydrogen generation rate was measured as 0,94 mL/min under 20 °C and 5.0 V conditions, while the highest rate reached 3,577 mL/min at 45 °C and 10.0 V. Regarding exergy efficiency, the lowest value was calculated as 1,544 % at low temperature and voltage, and the highest efficiency was recorded as 4,98 % under the highest tested conditions. This study highlights that the AlCl₃-based system was experimentally evaluated for the first time in terms of thermodynamic (exergy) efficiency, offering a novel and alternative approach within chlor-alkali technologies. Moreover, in addition to hydrogen gas, the system facilitates the formation of aluminum hydroxide (Al(OH)₃), a value-added by-product, thereby enhancing both the environmental sustainability and economic feasibility of the process.

Anahtar Kelimeler

• Hydrogen production
• Chlor-alkali reactor
• Energy
• Exergy

Alüminyum Klorür (ALCL₃) Bazlı Klor-Alkali Elektrolizi ile Hidrojen Üretiminin Ekserji Temelli İncelenmesi

Öz

Bu çalışmada, klor-alkali proseslerinde geleneksel olarak tercih edilen sodyum klorür çözeltilerine alternatif oluşturabilecek nitelikte, alüminyum klorür (AlCl₃) esaslı bir elektroliz sistemi tasarlanmış ve sistemin farklı sıcaklık ve voltaj düzeylerinde sergilediği ekserji performansı deneysel olarak değerlendirilmiştir. Deneysel düzenek, sabit elektrolit debisi (0,3 g/s) koşulunda, 20 °C ve 45 °C sıcaklıklar ile 5,0 V, 7,5 V ve 10,0 V hücre gerilimleri altında test edilmiştir. Çalışmada kullanılan laboratuvar tipi hücrede anot ve katot bölmeleri, Al³⁺ iyonlarının seçici geçişine imkân tanıyan Nafion 212 membranıyla birbirinden ayrılmıştır. Her iki bölmede beşer adet grafit elektrot kullanılmıştır. Elektrolit akış hızının hidrojen ve klor üretimi üzerindeki etkisi deneysel olarak önemsiz bulunmuş ve bu nedenle sabit tutulmuştur. Deney süresince anot bölgesinde meydana gelen klor gazı üretimi, elektrot yüzeylerinde kimyasal aşınmaya neden olmuş; bu durum, klor gazı veriminin hidrojen gazına kıyasla daha düşük olmasına neden olmuştur. Elde edilen deneysel bulgulara göre, hidrojen üretim hızı 20 °C sıcaklık ve 5,0 V gerilim altında en düşük seviyede olup 0,94 mL/dk olarak kaydedilmiş, buna karşılık 45 °C ve 10,0 V koşullarında 3,577 mL/dk ile en yüksek üretim hızına ulaşılmıştır. Ekserji verimliliği, düşük sıcaklık ve gerilim koşullarında % 1,544 seviyesinde kalırken, en yüksek verim % 4,98 ile yüksek sıcaklık ve voltaj kombinasyonunda gözlemlenmiştir. Bu kapsamda, AlCl₃ çözeltisiyle çalışan elektroliz sisteminin literatürde ilk kez termodinamik verimlilik (ekserji) açısından deneysel olarak incelendiği vurgulanmakta olup, bu tür sistemlerin klor-alkali teknolojileri içerisinde alternatif ve yenilikçi bir yaklaşım sunduğu değerlendirilmiştir. Ayrıca, reaksiyon sonucunda hidrojenin yanı sıra, ekonomik değeri yüksek olan Al(OH)₃ bileşiğinin oluşması, sürecin çevresel sürdürülebilirliğini ve ekonomik cazibesini artıran önemli bir unsur olarak öne çıkmaktadır.

Anahtar Kelimeler

• Hidrojen üretimi
• Klor-alkali reaktör
• Enerji
• Ekserji

Kaynakça

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