Some years ago various leading drymix producers started to look for flexible and somehow “portable” drymix plant concepts for their market analysing purposes. They were also looking for a plant concept that could be installed in difficult infrastructure locations in emerging countries.
The main drivers were a quick set-up of the plant, low height requirement in order to use an existing building or warehouse and being easy to relocate the plant to another location. Relative low investment costs as well as easy operation and maintenance, quick change from one product to another without any risks of contamination between various products and the raw materials were also significant factors.
The previously mentioned targets coupled with the ability to produce drymix products from simple mortars up to the most complex products, proved to be an impossible task for that time’s technology and plant concepts. In other words, the all-in-one package solution could not be achieved without compromising the product mix, product quality or investment budget.
FlexiBatch Drymix plant
Lahti Precision started to develop various concepts and can now proudly present the FlexiBatch concept, which meets all of the above-mentioned goals. It started as a “mini-equipment concept” with a mixing capacity of about 5 t / h, but eventually it reached a mixing capacity of 5-20 t / h, enabling an annual production of 25,000-100,000 tons.
Three standard plant sizes were established, introducing mixer net volumes of 500, 1000 and 2000 l. Each of the three FlexiBatch plant models can be expanded and modified according to the customer’s needs. It is implemented by installing raw material handling and logistics solutions that meet the requirements of local construction sites and markets. They also respond to the logistical challenges of raw materials and end products and, last but not least, to the investment budget.
Keeping this in mind the owner of the plant will benefit significantly from avoiding the costs of local steel structures, foundations, and civil works, as the plant can be erected in an existing building. FlexiBatch concept includes design and equipment for conveying, dosing, weighing and mixing of materials and in addition automation system with recipe handling.
Aggregates and binding materials handling
FlexiBatch is truly flexible with aggregates and binding materials handling and logistics. All possibilities are available from small or big bag serving as material storage up to more complex automatic aggregate preparation with direct dosing into the process etc.
This part of the plant is always selected and designed in close co-operation with the customer in order to tailor it to fully match with the local raw materials logistics and availability. As such this part may constitute a major part of the investment, unless original FlexiBatch “all raw materials delivered in bags” logistics system is feasible. Therefore, this plant section should always be designed with great care. Naturally Lahti Precision utilizes fluidization, special material conveyors, and best design practices in this section as well as in other plant sections.
Conveying
In the Flexi-Batch concept conveying of materials are handled in an optimum way by utilizing best available technical practices incorporating the ability to maintain high purity while changing the recipe, low wear and tear of the process equipment, and the lowest possible segregation.
Weighing
FlexiBatch incorporates the best of the best weighing equipment, with a weighing performance being in line with commercial weighing. This performance can be verified against OIML III regulations as all the weighing components are selected from the certified line of equipment (instrument, load cells and load cell installation kits).
Dosing
FlexiBatch incorporates numerous alternative dosing principles (cumulative or loss-off-weighing) and equipment which will be always selected based on material properties and accuracy demand dictated by the recipe or better stated, by the range of recipes. Mostly these consist of dosing equipment based on Lahti Precision’s fluidized dosing and conveying systems as well as Lahti Precision’s specially designed and well-proven screw feeders equipped with motorized agitators.
For low and middle budget applications additives can be dosed manually, but even in these cases the dosed amounts and materials are registered by the control system in order to keep the accurate batch log and minimize human error. Manually dosed additives are an extremely feasible and economic choice for plants having 5 to 10 t/h mixing capacity or applications that require frequent recipe changes, i.e, production of state-of-the-art technical mortars.
Mixing
The FlexiBatch plant incorporates high-quality twin-shaft mixers equipped with four high speed choppers for the 10 t/h and 20 t/h versions. The 5 t/h version has a single shaft mixer with one chopper. All these mixers provide excellent mixing results and are the same mixers that are used at Lahti Precision’s large traditional tower plants. Optionally all these mixers can be equipped with liquid spraying systems and/or semi-automatic easy cleaning systems.
FlexiBatch plant control system
The core of the control system is based on a Windows 7 platform running a Siemens user interface application engineered by Lahti Precision; logic operations are carried out with a Siemens PLC, and distributed I/O modules. On top of everything there is remote connection for maintenance and remote program changes as well as an incorporated comprehensive batch reporting database module.
This package of top-class engineering is well proven in practice and therefore together with the FlexiBatch modular and “ready-engineered” plant mechanics it offers a superior speed for putting the plant into operation compared with any other drymix concept in the market.
The author of the article is Niko Toimela, Sales Director of Lahti Precision. He has extensive experience and expertise in dosing and weighing systems.