The amount of foam scraped is a crucial aspect of flotation operations. It directly affects the quantitative and qualitative indicators of the flotation process. Besides depending on the thickness of the froth layer, the amount of foam scraped is also related to the balance and stability of the entire flotation process. Maintaining a balance and stability in the amount of foam scraped during roughing, scavenging, and cleaning processes, and strictly controlling the amount of foam scraped in each operation, is essential to obtaining qualified concentrate and fully recovering metals.

It must be pointed out that unilaterally increasing the amount of foam scraped is detrimental to the flotation process, a point often overlooked by inexperienced operators. Superficially, increasing the amount of foam scraped may seem to improve metal recovery, but in reality, as the amount of foam scraped increases in each operation, it not only easily scrapes a large amount of gangue into the product, reducing product quality, but also inevitably increases the amount of middlings recycled, disrupting the balance of the flotation process and worsening the flotation effect.

In flotation, the pulp gate of the flotation machine is mainly used to control the thickness of the froth layer and the amount of froth scraped out. Operators can make appropriate adjustments and use it as an emergency measure to deal with various drastic changes. However, adjusting the pulp gate cannot eliminate the factors causing these drastic changes. In practice, blind and frequent adjustments can disrupt the stability of the flotation process. In fact, many factors affect the amount of froth scraped out. If it’s a change in pulp concentration and fineness, the grinding and classification operator should be contacted immediately; if it’s an inappropriate reagent dosage, the dosage should be adjusted promptly. Only when something directly affects the flotation process parameters (such as pulp overflow, a sharp drop in the liquid level, or other abnormalities) should the pulp gate be adjusted immediately. When adjusting the pulp gate, it should generally be done starting from the tail end and adjusting it step by step towards the front. This maintains a relatively stable pulp volume and minimizes the impact on the next operation. If a sudden change in the overflow rate of the flotation machine causes a change in the flotation volume, adjustments should be made starting from the head of the flotation cell to eliminate the anomaly as soon as possible.

Operators should pay close attention to the thickness and volume of the froth layer in the concentrate output cell and the first few cells in the roughing operation. Because these flotation cells contain a large amount of valuable minerals, their flotation phenomena and froth mineralization are generally more responsive to changes in process factors. Therefore, mastering the operation of these cells is key to achieving high performance indicators for the entire flotation process. Based on the actual situation that the metal content gradually decreases in flotation, the froth volume should be reduced accordingly.