Sulfuric acid feed pump in the production of aramid fibers

TEF-MAG® - Chemical-resistant gear pump made of non-metallic materials for the conveyance of sulfuric acid in the production of aramid fibers

What is Aramid?
Aramid fibers belong to a class of heat- and flame-resistant, highly robust synthetic fibers, primarily used in specialized applications. The term "Aramid" derives from "aromatic polyamides." These polyamides consist of molecules with rigid and linear structures, granting the fibers their exceptional strength and temperature resistance. Aramid fibers are characterized by high tensile strength relative to their weight and maintain their strength and shape even at elevated temperatures. They are resistant to many chemicals and solvents and do not conduct electricity.

Due to these unique properties, aramid fibers are used in:

Protective clothing: e.g., fireproof clothing for firefighters or in bulletproof vests.
Aerospace: Used for components requiring both lightweight and stability.
Sports equipment: e.g., in racing bicycle tires for increased puncture resistance.
Industrial applications: Like ropes and cables where high strength and/or temperature resistance are required.

Prominent aramid products include Kevlar® (by DuPont), Twaron® (by Teijin), and Creslan® (by Hyosung). Notably, Kevlar® is widely recognized and is often used synonymously with aramid fibers, though it refers to a specific brand of aramid fiber.

In summary, due to their unique combination of properties, aramid fibers offer immense advantages in various specialized applications, especially where robustness, durability, and heat resistance are required.

Aramid Production Process:
The production process of aramid is complex, requiring precise sequences to achieve the specialized properties of these high-performance fibers. Sulfuric acid (H2SO4) plays a pivotal role in this, especially in the wet-spinning process for producing aramid fibers.

In the production of aramid fibers, particularly in the renowned method of producing Poly(p-phenylene terephthalamide), sulfuric acid acts as the spinning fluid. It serves as a solvent for the aromatic polyamide used to manufacture aramid fibers. The polymer is dissolved in concentrated sulfuric acid to produce a spinning solution. This solution is extruded through fine nozzles, creating threads. These threads are introduced into a coagulation bath, typically a diluted sulfuric acid solution, where the polymer precipitates and fiber formation initiates. The high sulfuric acid concentration allows the alignment of polymer chains in the solution before fiber formation commences – an essential step to achieve the impressive tensile strength properties of aramid fibers.

After the spinning process, the fibers are neutralized with water or an alkaline solution to remove sulfuric acid residues and stabilize the fibers.

Using sulfuric acid in this procedure requires specialized pumps that are corrosion-resistant and must withstand the acid's aggressive nature. Thus, selecting an appropriate sulfuric acid pump for producing aramid fibers is essential. It ensures effective and safe acid transport without the risk of leaks or failures.

Pump Design Data:
In the production process, the magnetically-coupled, fully non-metallic external gear pump TEF-MAG® is utilized. The chemical-resistant gear pump is designed to continuously feed between 500 l/h and 1000 l/h of the Sulfuric acid at a differential pressure of 2 bar to 6 bar. The TEF-MAG® 1500 pump is operated using a frequency converter, with the respective operating point adjusted by changing the speed.

Wetted Pump Materials:
Casing: PVDF
O-rings: FKM or FFKM
Shafts: SSiC
Bearings: Pure Graphite or SiC
Gears: z1 PVDF-CFR / z2 PTFEC

Advantages:
Thanks to its excellent chemical resistance and the exceptional dosing ability of a gear pump at low flow rates and high differential pressure, the TEF-MAG® is the ideal solution for this type of application. Magnetically-coupled pumps are generally considered maintenance-free, meaning significant costs for maintenance and repair can be saved over the pump's life cycle.

TEF-MAG® Explanation and working principle video: