The problem of transporting saturated brine

Could non-metallic materials be considered? For example, coatings such as F40 or PFA also belong to the tetrafluoro group!

The pipeline can be made of a non-metallic material, but it must be able to withstand a pressure of 5 Mpa, with a diameter of around 600 mm. For barge hulls, only metal can be considered.

Poster: Hello! I may not have explained it clearly; the materials I’m referring to usually have a steel lining – for example, those coated with F40 have a thickness of only about 1 MM, and their strength relies on the metal itself. The fittings and equipment produced by our company are made of metal, namely carbon steel, but they have linings made of PTFE, PO, PP, PE, F46, PFA, F40, or enamel, among others!

I understand what you mean; it’s a steel pipeline with coatings made of various materials inside. But the mixture that is transported through my pipeline is a combination of saturated brine and salt crystals, and these salt crystals cause friction against the coating as they move turbulently within the pipeline; I’m worried that over time the coating will wear off.

For example, when using PTFE material to make fittings with a diameter of 600, the thickness of the PTFE layer is 4 millimeters. Thanks to its low friction coefficient, PTFE has excellent self-lubricating properties! I would like to ask the original poster: is the flow rate of your mixture high? What is the content of crystalline substances? If the flow rate is low, there should be no problem.

The flow rate of the mixture is 5 m/s, and the volume concentration of sodium chloride crystals with relatively sharp edges is around 10–15%; I think wear and tear will be significant. I’m considering using HDPE pipes – I wonder if anyone is familiar with them

When it comes to the friction coefficient of non-metallic materials, PTFE is considered an excellent choice, outperforming other non-metallic materials. You can try it out with a short experiment first! Is HDPE material commonly used for pipes in urban water supply?

DN600 pipeline, flow rate of 5 m/s. Does the owner confirm that the flow rate and operating pressure in your pipeline are indeed this high? The long-distance brine transport pipelines I’ve seen in Sichuan have an annual transport capacity of ~390,000 cubic meters of brine (~1 million cubic meters in standard units); the flow rate is 55 cubic meters per hour, with a transmission pressure of 4–6 MPa. Steel pipes with a diameter of Φ219x7 are used, and the pipeline length is around 130 kilometers. There are two pressure boosting stations, and the designed flow velocity in these pipelines is only 0.46 m/s. It seems that there’s something wrong with either the flow velocity or the pressure in your case. Based on a pipeline diameter of 600 mm and a working pressure of 5 MPa, compared to this example project, your annual brine transport capacity should be around 3.6 million cubic meters, which is equivalent to 9 million cubic meters in standard units – that would correspond to a production volume of 900,000 tons of crude salt. That seems reasonable. However, a flow velocity of 5 m/s is extremely high. . . HDPE pipes are widely used in engineering projects at salt mines in China (such as the Qinghai Salt Lake), and they yield good results. But the pressure is not that high; generally, the working pressure is below 1.6 MPa. . If a working pressure of 5 MPa is indeed required, either you can choose anti-corrosion coatings with a metal lining (as has been discussed many times by Haiyou earlier), or another viable option is high-pressure epoxy fiberglass pipes, which can meet such pressure requirements. Reputable manufacturers or imported products can achieve a working pressure of 5.5 MPa, though the price is much higher. As for barges, coating for corrosion protection is generally used. As for special measures such as cathodic protection, it is recommended to consult professional manufacturers or shipyards. . Brine transfer pipelines are very troublesome; those with high mineralization levels can even develop scale. It is important to supply fresh water at the suction inlet of the pressure pump stations in order to prevent salt buildup. . If the pipes in the original poster’s system really have such high pressure, it’s better to use metal pipes with an anti-corrosion coating. Even if it is corroded, it can be repaired. .

For transporting brine, it is recommended to use steel-reinforced plastic composite pipes; we have used such pipes extensively in Qinghai and Luoyang Potash, as well as in Sichuan, Henan, and Shandong. However, the maximum pressure they can handle is 2 MPa, which is not sufficient to reach 5 MPa.

What I have here is a pipeline for transporting crystalline sodium chloride and saturated brine. Since the particles of sodium chloride crystals are around 2 mm in size, the flow rate must be maintained at 5 m/s to prevent the particles from settling and blocking the pipeline. With a simple calculation, the hydraulic slope i = 1.25 (density) * 0.012 (friction coefficient of iron pipes) / 0.6 m (pipe diameter) * 5 * 5 (square of flow velocity) / 2g = 0.031. To transport water over a distance of 8 km, the required head pressure is 8000 * 0.031 = 250 m, which equals 2.5 Mpa. But this is just the transportation of pure liquid. With coarse sodium chloride particles at a volume concentration of 15%, frictional resistance **increases**. The model is quite complex, so no explanation will be given here. The pressure loss along the pipeline is at least 10 Mpa. Add a transfer pump in between; the pipes must have a pressure resistance of at least 5 Mpa. If HDPE cannot withstand such high pressure, I will consider pipes with a steel framework instead. I’m also really troubled by salt crystallization right now. There are no sources of fresh water in the area. I wonder if the friction of sodium chloride crystals against the pipe walls will scrape away the crystalline salt.