چكيده به لاتين
The chlor-alkali process, as an electrolytic process (electrolysis), has been widely used to produce chlorine and sodium hydroxide since the 19th century. In this regard, three electrolytic processes have been employed: diaphragm, mercury, and membrane cells. The first two processes were abandoned due to environmental concerns, such as the use of asbestos and mercury. The membrane chlor-alkali process has gained attention as the superior method in terms of energy efficiency and the absence of harmful chemical emissions. In the membrane chlor-alkali process, the cell is the most critical component, and it is categorized into two-chamber cells, limited-gap cells, and zero-gap cells. The zero-gap cell has garnered more attention due to its ability to reduce energy consumption and increase production efficiency. The cell's dimensions in the chlor-alkali process are significant in performance and energy consumption. Therefore, COMSOL multiphysics software was used to simulate and design the flow channel to examine the potential for clogging caused by bubbles produced in the cell and to design an appropriate flow channel model. This simulation was conducted using a two-dimensional geometry in a time-dependent mode over a 10-second interval, to design a flow channel that includes a two-phase liquid and gas flow. The results indicated that using a single spiral flow channel with dimensions of 3x3 cm² facilitates the release of gases and minimizes the likelihood of clogging or blockages in the path. Subsequently, a zero-gap cell with an engraved flow channel on the respective electrodes was constructed. The construction of the zero-gap cell in this research was achieved by using a dimensionally stable anode (DSA), a nickel cathode, and a commercial two-layer sodium ion-exchange membrane, model Flemion 316. Next, the cell's performance and efficiency were evaluated. The operational parameters affecting cell performance, including cell temperature in the range of 25-90°C, current density in the range of 1-4 kA/m², feed flow rate of 5-25 ml/min, and brine concentration of 200-300 g/l, were examined to assess the variation in cell voltage and sodium hydroxide current efficiency. This was done using the response surface method at three levels, which included 27 experiments. From these experiments, the optimal conditions for each parameter were obtained at a current density of 4 kA/m², a temperature of 90°C, a brine concentration of 300 g/l, and a flow rate of 25 ml/min. Under these conditions, the cell achieved a sodium hydroxide current efficiency of 99% and a cell voltage of 4V. Thus, the results indicate that current density and cell temperature had the greatest impact and interaction on cell performance.
