The seawater desalination process is emerging as a substantial source of fresh water by removing salt and minerals from an infinite supply of seawater effectively. The first stage in a desalination plant is the use of chlorine gas to sterilize the microorganisms in the water. During excess chlorine leakage, an alert is activated, employees are relocated away from the site for a specific period, and dampers will be manually opened. This will cause unsafe working conditions and a waste of time. To overcome this problem, this paper proposes a coefficient diagram method based proportional integral derivative (CDM-PID) control strategy for the tune the control parameter with the distributed control system (DCS) interfaced conical tank. During operation, a 10% NaOH solution is injected into the top of the scrubber column using an ethylene-ter-polymer (ETA) designed distributor to ensure that the solution is evenly distributed across the packing surface. The three control strategies are compared to tune the control parameter with the DCS interfaced conical tank. Instead of the sodium hydroxide tank in the chlorine scrubber system, this work presents the pilot plant of DCS interfaced with two conical tank interacting systems with different liquid level heights. Here, the proposed CDM-PID controller is compared with the standard Ziegler-Nichols (ZN)-ultimate cycling method, and the internal model control (IMC) method. The results demonstrated that the proposed CDM-PID approach is superior to existing approaches in terms of low oscillation, settling period, and high robustness.

A steady global decline in the grade of chromite ores is causing an increase in the mining of low grade and complex ores. The processing of such low grade and finely disseminated ores results in the increased production of primary and secondary slimes. Slimes have very poor recovery performance in most conventional technology and are usually disposed of into tailings storage facilities (TSF). The historic slimes in the TSFs and those arising from most chrome production processes constitute potential recoverable chrome resources. In this study, the selective flocculation of slimes from a chrome processing plant in the north west province of South Africa was conducted using raw corn starch and sodium oleate as flocculants and sodium silicate a dispersant was applied on. Limited work has been reported on the flocculation of non-synthetic chrome slimes. The results showed that a slime sample with a chrome (Cr2O3) head grade of 22.92% was upgraded to a maximum concentrate grade of 42.55% at a sodium oleate dosage of 88 g/tonslurry, a sodium silicate dosage of 44 g/tonslurry, 39.61% at a starch dosage of 106 g/tonslurry and sodium silicate dosage of 62 g/tonslurry. The corresponding recoveries using sodium oleate as a flocculent were between 80–89% and 73–79% for starch. Sodium oleate showed a better performance than starch in terms of both grade and recovery. Decantation washing tests showed that the chrome (Cr2O3) grade of the concentrate can be further increased to above 44%. These results are very encouraging as they indicate that selective flocculation can achieve satisfactory upgrade ratios and recovery when processing chrome ultrafine or slime material.