What can the concentration ratio of circulating water indicate?

The salinity of fresh water differs from that of recycled water that has undergone a concentration process. The ratio between the two is known as the concentration factor, which is expressed by the formula: N = S_recycled / S_freshwater. Here, S_recycled represents the salinity of recycled water in mg/L, while S_freshwater represents the salinity of the fresh water added, also in mg/L. Generally, the concentration factor indicates the efficiency of water utilization; a higher concentration factor means that less fresh water is needed under the same conditions. A concentration factor of 1.8 is far too low; currently, the concentration factor in Sinopec’s circulating water systems is generally above 4.5. Of course, the concentration factor is closely related to water quality, management practices, and chemicals used; any issue in any of these areas can prevent the concentration factor from increasing.

In an open-loop circulating cooling water system, the concentration ratio is a key parameter. The higher the concentration ratio, the greater the reuse rate of water, the less wastewater is generated, and naturally, less water needs to be added. Therefore, increasing the concentration ratio is the key to saving water. During operation of circulating cooling water, losses occur due to evaporation, wind-induced loss, blowdown loss, and leakage. To maintain the water level in the pool, corresponding replenishments are made. The sum of these four types of losses constitutes the water replenishment amount. The dissolved salts in the circulating water also become concentrated over time. This is because the water lost through evaporation does not carry away any salts, while the salts present in the water added to the system accumulate in the circulating water. As a result, as the water system operates for longer periods, the salts in the circulating water become more concentrated. We use the concentration of a certain salt to determine the concentration factor. The more common method is to use chloride ions in water (potassium ions can also be used under certain conditions). The calculation formula is: concentration ratio = Cl- in circulating water / Cl- in make-up water. To save water and reduce emissions, it is necessary to understand the relationship between the concentration ratio and the wastewater discharge rate. The amount of water needed for make-up consists of losses due to evaporation, wind, leakage, and wastewater discharge; leakage losses are purely caused by external factors and can be ignored. The wind-induced loss is related to the wind volume, tower type, and the presence of a water collector; it is generally estimated at 0.1–0.2% of the circulating water volume. Evaporation losses are primarily determined by factors such as external temperature and humidity, tower design, and the temperature difference between cold and hot water, while discharge losses are related to water quality and the concentration ratio allowed by chemical treatment processes. A high concentration ratio is allowed, resulting in less wastewater; if the conditions are met, no wastewater may even need to be discharged. Therefore, to save water and reduce emissions, it is necessary to increase the concentration ratio, and increasing this ratio can only be achieved by using high-quality chemicals and processes, or by improving the quality of the make-up water in order to enhance the quality of the circulating water.

We control it by looking at the values of chloride in the recirculated water/chloride in the raw water; 3-5 is sufficient

The concentration ratio is closely related to the water savings rate, which indicates that your factory’s water utilization efficiency is not high, and the level of water savings is low. The other factors don’t matter much; concentration is used to save water. DC power would be sufficient in such cases. Even in areas where there is an abundance of water sources, DC power is still used. Sigh

It can be seen the utilization rate of circulating water

Formula for selecting the concentration ratio: B = E/(N-1). C: Salt content of the make-up water, in mg/l; CR: Salt content of the circulating water, in mg/l. The higher the concentration ratio, the more water savings are achieved, but it’s not true that the higher the better – the optimal value lies between 2.5 and 4.5.

The water recycling concentration ratio indicates the degree of water conservation in that recirculating water system. 1.8, which is the ratio of water added to wastewater discharged. If the make-up water is fixed, the higher the concentration, the less wastewater is generated.

The concentration ratio can indicate the utilization rate of water, and it can also indirectly show the difference in quality between recycled water and newly added fresh water. For example, if the iron content in the circulating water differs significantly from the iron content calculated based on the concentration factor, corrosion is likely to be severe.

Potassium ions can be used; it’s a very important indicator

We can control it by using the values of chloride in the recycled water/chloride in the raw water, with a target range of 2-3. Controlling the concentration ratio can improve water utilization, but a higher concentration ratio is not necessarily better.