Steuler Acid Microfiltration (SAM)

Using this process the insoluble solids acccumulated in the pickling solution are separated by continuous microfiltration and upconcentrated.

  • Complete separation of finest particles in µm-area at high solid concentrations
  • Use of acid-proof materials and diaphragms
  • Modular design to increase the capacities and later extension by the acid purification
  • High process automation and user-friendly design
  • Feasibility of the sub-assembly of standarized plant parts with few labour at jobsite

Objective of the solid separation is:

  • Drain of the particles from the pickling bath thus reducing the sedimentation of solids, deposits and the accumulation of mud in the pickling bath causing often plant shutdown necessary for cleaning the pickling baths as well as avoiding and increased consumption of acid.
  • The production of an absolutely solid-free filtrate that is further used in a downstream process stage for cleaning the free acid or regenerating the total acid.
  • Condition for the separation of solids by means of filtration in a separate microfiltration cycle is the complete homogenization of the particles contained in the pickling bath itself. Therefore Steuler Anlagenbau uses separate circulation cycles and injectors in the strip and wire coil pickling lines.

Process Description

The solids homogenized due to a continuous mixing of the pickling baths are supplied with pickling solution in a partial stream of the microfiltration system. The principal part of this separating stage are one or more Cross-Flow-Microfiltration modules to press the pickling solution through the membrane at high speed. The solids are completely retained at the surface of the membrane, strongly accumulated in the cycle and being drained with a small partial stream. Due to the combination of hydraulic design and periodic backrinsing the service life of the used acidproof microfiltration membranes is very long.

The plants are constructed in modular design and corresponding to the accumulated solids or to the filtrate flows required for the downstream acid purification/ recovery.

The design of the plants comply with the respective requirements/ standards. At high pickling acid temperatures a single-stage heat exchanger can be installed for cooling with cooling water. As option, when using a double-stage heat exchanger the cooling is carried out in the first heat exchanger stage with the filtrated pickling solution by heat recovery, only in the second stage a small quantity of cooling water is used.

The operation of the microfiltration systems and the periodical backrinsing are fully automatically. The required rinsings of the filtration cycle in case of plant shutdown, maintenance or failures as well as the rinsings of the acid feed and drain pipes can be fully automated. So the high process automation as well as the operation and documentation via the central processing unit (CPU) are the main features ensuring an user-friendly design and operation of the plant.

When using an acid purification/ recovery downstream to the microfiltration systems, it is useful to concentrate further the solids in order to minimize the loss of free acid in the flow to be drained. This is achieved by thickening the suspension being pre-concentrated in the filtration by means of sedimentation or hydrocyclone stages.

The Steuler Acid Microfiltration SAM is mainly used for the filtration of mixed acid (HF/ HNO3), HF / H2SO4 and HCl, and has already been well-proven in appr. 20 reference systems for 20 years.