High throughput rate

Grenzebach's vibrating tube mills are the solution for grinding medium-hard to hard, abrasive products such as slag, ashes, fire clay etc.

They are based on the principle of vibration milling with three milling tubes aligned at 60° to each other. The mill achieves high and constant throughputs with low energy consumption. It can be operated continuously as well as intermittently. Throughput rates of up to 20 tons per hour can be achieved. Product temperatures up to 350°C are possible. For feed particle sizes < 10 mm, final grinding of d90 = 50 µm can be achieved depending on the product quality.

Properly separated

With Grenzebach's jet airstream sifter, powder can be separated into three fractions (fine, medium and coarse material) in one step. This is efficient for sifting bulk goods, as well as for the separation of fine material without over-sized grains in all the areas of solid material process engineering. Depending on the application and sifter type, throughputs between 3,000 to 50,000 kg/h can be achieved with product temperatures of up to about 130°C.

The jet airstream sifter can be used for particle sizes up to 3 mm. It is suitable for classifying or extracting dust from powders in the range of 20 - 150 µm.

Compressing carefully

Vacupress systems are used for deaeration and compressing powders smaller than 40 µm.

They are used as compactors before packaging units. Clear practical benefits are the reduction of transport volume and minimization of dust generation or even improvement of handling properties for the end user. The Vacupress systems can also be used as a dosing unit for better incorporation in downstream processing steps or as pre-compression unit along with granulators.  Volume reductions of up to 75% can be achieved.

The product is compressed very carefully. The properties of the products handled are hardly changed due to the relatively low compression forces used in the process. The product flakes generated in the process can be returned to their fine powdered state at any time without the application of high shear forces.

The Vacupress is suitable for bulk material weights of less than 750 kg/m³ and temperatures of up to 100°C.

A class by itself in super-fine grinding

The Grenzebach whirlwind mill offers application benefits especially in the area of fine and super-fine grinding of soft and medium-hard products up to Mohs hardness level of 5. Existing complex systems, consisting of expensive sifter mills or conventional beater mills with downstream sifters, can be replaced with a cost-effective whirlwind mill. This is efficient process technology. Throughput rates from 50 kg/h up to 20,000 kg/h can be achieved at product temperatures of up to 200°C.

In addition to the super-fine milling in the range < 100 µm, Grenzebach's whirlwind mill has especially proven itself in the area of shredding organic substances (paper, cardboard, cellulose, etc.), grinding coating, cryogenic cold-milling, milling-mixing as well as milling-drying.

Professional heating

Rotary kilns are used for high temperature treatment (heating, annealing, roasting, calcination, reaction, burning etc.) of solid, pasty or sludge-like bulk materials. Typical application examples are petroleum coke, cristobalite (white pigment), phosphates, activated carbon and catalysts.

Grenzebach manufactures directly heated rotary kilns for process temperatures of up to 1600°C. The product goes through a rotary element rotating around its own axis. Heating takes place directly in a hot gas stream that flows through the product space of the rotary tube.

This kiln is characterised by a simple and robust design, high operational safety, large throughput rates and the possibility of being used even with varying feed quantities. An additional benefit: the waste heat from a downstream product cooler or waste gas from other processes can also be used.

Save up to 15% of primary energy

Rotary heat exchangers can also be designed as recuperative tubular coolers. With the indirect air-cooled rotary coolers from Grenzebach, the energy of heated solids can be recovered from high-temperature processes. A clear contribution to the energy efficiency in process engineering. The product inlet temperatures can be up to 1000°C.

The coolers are often used behind kilns heated using hot gas (e.g. rotary kilns). On the one hand, heating the kilns requires a lot of primary energy. On the other hand, the finished product has to be generally cooled to prepare it for transport or further processing. The contact between the solids and cooling air takes place indirectly using internal tubes, which rules out the air from getting polluted by dust. The use of dust-free cooling air heated to 200 - 300°C in furnaces enables up to 15% saving in primary energy.

Typical products are titanium dioxide and other inorganic chemical products.

Fit for mass flows of products

Grenzebach's moving bed heat exchangers enable the transfer of large amounts of heat and handle mass flows of products with very little space requirement. They use indirect water-cooling and steam heating.

This process technology is used in high temperature zones behind furnaces and dryers. The moving bed heat exchanger can be operated up to product temperatures of 1200°C.

The products, specifically fine-grained and free-flowing bulk materials, are handled very carefully. The wear on the equipment itself can be hardly measured. The patented surface design ensures a high degree of heat exchange, as well as complete utilisation of the entire heat exchange area.

The moving bed heat exchanger is also suitable for heating powdered bulk materials. We would be happy to implement the Grenzebach's food-grade version.

Hardly any dust dispersion

Grenzebach's annular tray dryer is the perfect way for continuous drying of sensitive powders, crumbs, pastes, flaky or chunky products. It consists of a rotary ring frame with levels arranged one above the other.

A special feature of Grenzebach's annular tray dryer is that the particles are moved slowly, gently, almost without any abrasion and with little dust dispersion. Typical application examples are precipitated calcium carbonate, calcium phosphate, activated charcoal, bentonite, and titanium dioxide.

Grenzebach manufactures annular tray dryers, which are particularly suitable if the wet product has difficult rheological properties, long retention times are needed and the product has to be handled very carefully. Our equipment is ideal if intermediate milling is required after drying the product. The structure of the product is retained during drying, and there is no separation during the engineering process.

The geometry of the equipment ensures good performance and high throughput with relatively little floor space required compared to other dryers. Several process flows, such as drying, heating and cooling, can be implemented into one piece of equipment.

Works without dust extraction

Sectional coolers are indirectly water-cooled rotary tubes for cooling solids heated up to 1400°C.

Grenzebach's sectional coolers are suitable for very fine particles as well as for solids, which are permeated with coarse particles or even agglomerates. Reactive products can also be handled.

The interior is divided into several sections. The walls between the sections and the double-walled rotary shell is flushed with cooling water during the rotation of the cooler. The water cooling system of the sectional cooler works without pressure.

Indirect cooling has the advantage that there is no product loss due to dust that is carried along. Dust extraction units are therefore not required.

The geometry of the sectional cooler ensures optimum cooling performance and high throughputs with compact dimensions. 

From quartz sand to cristobalite

Cristobalite is a substance manufactured from quartz sand. It is characterized by its high abrasion resistance and high whitening property.

In the Grenzebach systems, the already pre-treated (that is washed, classified and filtered) quartz sand is dried and pre-heated first in a drum dryer. The advantage of Grenzebach's process technology is the more efficient treatment of waste gases. The rotary kiln is also shortened due to the material preheating using the exhaust gases.

The calcination / crystallisation takes place in the rotary kiln by heating the sand further to more than 1200°C. The cristobalite sand is finally cooled down to 700°C in the cooling fluidised bed. It is brought to a manageable final temperature in a second cooler that works indirectly with water.

Cristobalite is suitable for abrasion-resistant exterior wall paints, road markings or counter-tops in kitchens.

Highest quality of finished products

Technical phosphoric acid is manufactured, for example, from apatite using sulphuric acid digestion process. The calcium phosphate in the apatite reacts with the sulphuric acid. One of the by-products is hydrofluoric acid (in case of fluorapatite). The water-insoluble calcium sulphate (phosphorus gypsum) is filtered out. The phosphoric acid solution is concentrated, purified, and then crystallised in a precisely controlled temperature range.

Phosphoric acid solution can be further processed to phosphate fertilizers or phosphoric acid salt using different processes. For example, one such process is the Sodiumtripolyphosphate (STPP) process. STPP is a white, odorless and water-soluble phosphate salt. It is used mainly in the detergent and food industry.

In Grenzebach's STPP manufacturing process, phosphoric acid, sodium carbonate and soda are first made to react. They are then neutralised, dried, and converted to STPP using polycondensation and calcination of the dried orthophosphate. With Grenzebach's flexible production concepts, heavy as well as light sodiumtripolyphosphates can be manufactured.

Our plants have proven themselves for decades. This practical experience implies a high degree of flexibility in designing the process steps and in process control for our customers. The result is a constant high quality of finished products.

Calcinated green coke

Petroleum coke is a carbon containing solid which is a by-product of crude oil refining. A common product example is green coke.

After carbonization, the green coke is dried in the Grenzebach plant in a pre-dryer which is heated indirectly using exhaust gases. It then reaches the directly heated rotary kiln. There, it is calcined at temperatures exceeding 1200°C. The calcination process for manufacturing coke is the core of the Grenzebach petroleum coke plant. This process has some special features compared to other further refining processes. For example, by dispensing with tertiary air, the burning of calcined petroleum coke is avoided by up to 3% in our plants. The length of the rotary kiln can also be reduced by up to 40% by using the pre-drier. Another advantage of Grenzebach's calcination is that the dust generated is continuously fed back to the rotary kiln.

The calcined green coke is cooled down to temperatures below 120°C in a sectional cooler so that it can be transported further.