The inquiry was about crystallizers in diameter DN/ID 2000 for chemical plants in Germany and Thailand as an elementary part of the extraction process for Tantalum. Tantalum is a very valuable and precious material. It is used in our modern environment mainly for microelectronics, medical implants, vessels for chemical industry and automotive and can not be replaced easily by other materials. The worldwide yearly production quantity is around 1400 tons. The company Jäger is looking back on a long history for manufacturing that kind of apparatus and has quite a lot of experience in fabrication with thermoplastic and duroplastic materials in general. Crystallizers are a challenging product, due to the sensitivity of the chemical process and needed accuracy in temperature control. The crystallizers are made of Polypropylene Homopolymer due to the high temperature resistance, the low thermal conductivity and low thermal expansion.
Tailormade according to the requirements
Polypropylene Homopolymer can be used under consideration of the creep rupture strength until ca. 100 °C. The Krah pipe product is selected, because Krah pipes can be manufactured tailormade according to the requirements and customer design. The wall structure can be structured with an internal hollow profile and the wall structure can change within a pipe. And that is exactly what is needed. The production of a cylinder shell is made by Krah Pipes Germany, located in Schutzbach, in the Westerwald region. Krah pipes with structured wall and with smooth inner surface are standardized according to DIN 16961. The pipe is produced on a preheated steel-mandrel in several layers to achieve the requested wall profile and thickness. According to requirements the pipe wall includes a strong inner wall, a spiral hollow profile for controlling tempering fluid during operation later on and a strong outer wall. Both ends of the pipes are homogenously closed during production by solid wall. All dimensions (wall thicknesses, spiral shape and diameter of the hollow profile) are made according to the technical design by company Jäger.
Raw material is approved by DIBt
The selected Polypropylene Material is a Polypropylene Homopolymer with high molecular weight, with fine grained ß-modification crystalline structure, leading to excellent mechanical and physical properties and improved chemical resistance. The raw material Type “Borealis BE60-7032” is approved by DIBt, the German-based technical authority and service provider for construction industry. The main purpose of a crystallizer is to generate crystals from a hot solution. While cooling down the solution becomes oversaturated and crystals begin to form. The size and density of the crystals define the quality of the product. Therefore, temperature and agitator control are very important within the crystallization process. The crystallizer is designed for maximum operation temperature of 95°C. The medium is a mixture of Tantalum salt solution and hydrofluoric acid. The working pressure is hydrostatic. At site the crystallizer is mounted in a special steel frame and on top a special agitator is installed for controlled mixing and homogenization process.
Active cooling required
The used Polypropylene Homopolymer works as an insulator so active cooling is required. In this case it is achieved by integrating cooling pipes into the cylinder shell and three additional cooling fingers are installed though the cover of the vessel. The design has to be done under consideration of all static and dynamic load cases. For assembling is very important to ensure that all elements are fabricated and installed with highest accuracy. Especially the contact area between Polypropylene crystallizer and steel-frame has to match, to avoid unnecessary stresses. Before leaving the factory, the crystallizer gets quality checked and tested. The integrated cooling pipes in the cylinder and the cooling fingers has to pass a pressure test at 3 bar and 24 hours. It is elf-evident, that for such chemical apparatus experienced fabricators are preferred. All welders are approved by third party inspection and of course all welding are done according to DVS 2205.
Author: KW Jäger GmbH