A European manufacturer of autoclaved aerated concrete (AAC) and calcium silicate products operates several production facilities. At a plant in the Czech Republic, the company manufactures high-quality aerated concrete blocks based on silica sand.

AAC is produced by first finely grinding silica-rich sand in a ball mill. The resulting sand slurry is then conditioned in a mixer with water, lime, cement, anhydrite and aluminium powder to form a slurry. The mixture is subsequently cast into moulds, where it expands through a chemical reaction and the formation of fine hydrogen bubbles, creating a porous structure. After standing for several hours, the mixture forms a block that is sufficiently firm for cutting and is finally cured in high-pressure steam autoclaves.

During the sand-mixing stage, slurry temperature and density are critical parameters for ensuring consistent AAC production conditions. To maintain the target slurry temperature required for the downstream mixing and casting processes, hot and/or cold water is added as needed, and the temperature must be closely monitored.

The customer was therefore looking for flowmeters capable of reliable and repeatable measurement while meeting the application's requirements. What initially appeared to be a straightforward hot- and cold-water flow measurement application proved to involve challenging process and environmental conditions.

As the measuring points are located directly next to a ball mill, the flowmeters had to withstand vibrations and shocks occurring during the grinding process. In addition, pressure surges may occur when the dosing valves are opened and closed. The water used for dosing contains high levels of calcium compounds, which gradually form deposits on the inner pipe walls. The pipelines are therefore periodically cleaned with an acid solution that dissolves these deposits and allows them to be flushed away. Ensuring reliable measurement under these demanding operating conditions required careful selection and design of the instrumentation.

After discussing the flowmeter requirements with the operator, the OPTIFLUX 1050 proved to be the most suitable and economical solution for dosing hot and cold water into the sand mixer. The electromagnetic flowmeter is designed for flow measurement applications where moderate accuracy is sufficient, but high measurement repeatability and fast signal processing are essential, particularly in start-stop dosing applications. With a maximum process temperature range of up to +120°C / +248°F, it is also ideally suited for hot-water dosing.

The OPTIFLUX 1050 features a robust PFA liner that is hot-pressed into a stainless-steel reinforcing grid. This ensures the long-term dimensional stability of the liner. Combined with its rugged Hastelloy^® electrodes, the flowmeter offers excellent resistance to the acidic cleaning solution used by the operator for periodic descaling.

The flangeless design makes the OPTIFLUX 1050 particularly compact, lightweight and cost-effective. Its wafer-style, or “sandwich”, construction enables space-saving installation between counter flanges. Given the environmental conditions and the established process control concept, the customer opted for a signal converter without a local display. Measurement values are transmitted to the control room via pulse output.

The OPTIFLUX 1050 is a key element of the sand-mixing process control loop, enabling precise conditioning of the sand slurry and helping to achieve the target temperature and pressure required for the AAC mixing and casting processes. In this way, the KROHNE flowmeter contributes to the production of high-quality aerated concrete blocks with the desired thermal insulation properties.

Thanks to its liner and electrode materials, the flowmeter fully meets the application requirements beyond straightforward water measurement. It can remain installed during descaling operations, eliminating the need for disassembly. Furthermore, its robust fully welded construction and chemically resistant wetted materials minimise the risk of leakage or damage. In addition, the OPTIFLUX 1050 features a full-bore design without mechanical obstructions or moving parts that are subject to wear and tear and can cause significant pressure loss in mechanical flowmeters. Vibrations and shocks generated by the ball mill, as well as pressure surges in the water lines, are also not an issue for the KROHNE flowmeter.

The OPTIFLUX 1050 is part of a comprehensive, tailored portfolio of electromagnetic flowmeters that KROHNE offers to customers in the construction materials and mining industries. The portfolio also includes versions with exceptionally low-noise electrodes and highly wear-resistant liner materials for very demanding applications involving abrasive slurries and high solids content.