Block factory on wheel

Raw material storage, dosing, and mixing

Sand lime bricks consist of the two raw materials sand and lime only. For the manufacturing process, water is required in addition. The raw materials that are mostly supplied from local extraction places are stored separately in raw material silos. On the way to the silos, the sand passes a screening station to separate oversize material.

Hawk sand lime brick making plants are designed to use at least two different types of sand. The advantage for the customers is that the product quality can directly be influenced by a specific mixture of the different types of sand.

The raw materials sand, lime, and water are exactly dosed and weighed in individual scales and fed into the intensive mixer. In the mixing process, a homogeneous and highly disperse sand lime compound is generated.

The complete automatic process is controlled and monitored via the Hawk mixing plant control system .

Reactor and chemical reaction

By means of transport devices (eg. belt conveyors and bucket conveyors), the sand lime compound is fed into the reactor . The number of reactors depends on the number of presses. Typically, one reactor per press is used. Advantage: With the help of the Hawk mixing plant control system, each press is always supplied with an optimum sand lime compound, also in case of different products.

Inside the reactor, the lime is turned to calcium hydroxide by means of a chemical reaction that is triggered when water is added. This process is completed after approx. two hours, and processing of the sand lime compound can be continued in the press.

Hawk double shaft mixer

Between the reactor and the press, there is a double shaft mixer. To provide the double shaft mixer and the press with constant quantities of sand lime compound, the reactor outlet is equipped with a special discharge system developed by Hawk. With the help of the Hawk press control system, the quantity of the sand lime compound is adapted to the manufacturing process.

For an optimum moisture content for pressing, an automatic dosing device adds water to the double shaft mixer. All give-over points are particularly tight to avoid the development of dust.

Hydraulic sand lime brick press Hawk HDP

The heart of a sand lime brick making plant undoubtedly is the Hawk press, eg. type HDP 800. Hawk can offer different press types for different capacity requirements.

In fully automatic hydraulic presses, the sand lime compound is pressed to bricks. The Hawk press control system provides for a uniform compaction of the sand lime compound until the required final height and density of the products is reached.

Different moulding tools enable the manufacture of different brick sizes. Depending on the type of tool, it is possible to manufacture perforated or solid bricks with or without tongue and groove or holes for handling or chamfers.

A brick placing automat takes the fresh bricks from the press and smoothly places them on a hardening car. The Hawk press control system enables a precise and space-saving loading of the hardening cars so as to make an optimum use of the autoclave capacity.

Would you like to manufacture colored sand lime bricks?

Hardening car transport from the press to the autoclaves

When the hardening car has been loaded completely, it is moved to a transport platform via a rail track system. Depending on the factory capacity, up to 8 hardening cars can be moved so that loading and unloading of the autoclaves can be carried out quickly.

Autoclaves/steam boiler

The sand lime bricks receive their final strength by means of hardening under steam pressure in special, sealed pressure vessels, the autoclaves.

The steam pressure is approx. 12 bar, the temperature approx. 192° C.

The hardening procedure is precisely defined. The hardening time depends on the density and size of the sand lime bricks. Usually, it is between 4 and 8 hours.

The various autoclaving steps can individually be determined in the Hawk autoclave control system . The complete hardening process runs off automatically and is continuously recorded.

The steam for the hardening process in the autoclaves is generated in a steam boiler plant. Usually, high-capacity steam boilers that are operated with gas or oil are used for the steam generation.

Packaging

When the hardening process has been completed, the sand lime bricks are ready for use.

From the transport platform, the hardened sand lime bricks are transported to the packaging plant on the hardening cars via a rail track system. To guarantee a fast discharge of the autoclaves, a complete autoclave filling can be stored intermediately in front of the packaging plant.

The Hawk cuber takes the sand lime bricks off the hardening car and places them on transport pallets.

Hawk recommend to package the finished products in that way that they are protected from dirt and moisture before they are removed from the factory. Depending on the plant concept, this packaging process can be carried out automatically or semi-automatically.

For a safe transport and storage of the filled transport pallets, these have to be bundled, preferably with plastic straps.

Other individual packaging concepts, eg. with stretch film or shrink-wrapping plants, can be integrated into the packaging line as per customer requirements.

Cleaning of the hardening cars

As soon as the Hawk cuber has taken the hardened sand lime bricks off the hardening cars, the latter are cleaned. The cleaning device consists of a rotating brush and an oscillating scraper.

The empty car platform returns the cleaned hardening cars to the sand lime brick presses where they can be loaded with fresh bricks again.