BIBKO® INFRATEC - Recycling of drilling fluid
GRAALMANN GmbH in Leer invests in its own recycling system
Drilling fluids are liquids that are used for backfilling and grouting cavities, as well as for horizontal and geothermal drilling. In addition to cleaning the borehole, the drilling fluid also cools the drilling tools, stabilises the borehole wall and reduces the friction between the drill string and the rock.
Drilling fluids are initially a mixture of water, bentonite and minerals. Due to the wide range of applications, large quantities of used drilling fluids are produced that have lost their relevant construction properties. Further use is no longer possible, so they have to be disposed of. However, as these are stable and do not separate on their own, or only very slowly, disposal is difficult. Due to the high liquid content, disposal in landfills is not possible without prior treatment for landfill construction reasons.
| GRAALMANN GmbH - A company with ideas Environmental protection, legal certainty and sustainability are the cornerstones of responsible waste disposal and logistics at GRAALMANN GmbH in Leer. Founded in 1999, GRAALMANN GmbH today specialises in the professional processing of mineral waste, such as drilling fluids, with the motto of not disposing of waste wherever possible, but rather recycling and reusing it sensibly. Special emphasis is placed on sustainability and environmental protection. In this way, resources and thus the environment are conserved. |
Recycling system for drilling fluids - a building block for implementing the company strategy
Before the installation of the BIBKO® INFRATEC recycling system, the processing of drilling mud essentially consisted of buffering the drilling mud delivered in large polders. Dewatering and volume reduction was carried out by wind and sun. For further dewatering, the partially dewatered material was also moved several times a year using excavators.
Limitations of the original system
Although the use of wind and sun for dewatering and volume reduction had the advantage that only renewable energies were used, this also resulted in dependencies that influenced the throughput and thus the amount and quality of waste that could be processed. Furthermore, drainage areas were only available to a limited extent. Continuous processing and reliable planning, in particular of the quantities accepted, was therefore only possible to a limited extent.
GRAALMANN therefore decided to invest in a complete solution for the recycling of drilling mud. The BIBKO® company, INFRATEC division, was commissioned to design a suitable recycling system for this purpose. This recycling system has now been successfully in operation for several months.
Plant parameters
The following parameters were used as a basis for the design of the recycling system.
- Waste type: Waste from freshwater wells (drilling fluid)
- Waste code: AVV 01 05 04
- Composition: variable (depending on region)
- Input quantity: 10,000 tonnes/year
- Material feed: 2 vehicles simultaneously
The integrated, 4-stage recycling solution
Based on the system parameters, the recycling system was designed as a 4-stage recycling solution:
Process stage 1: Material feed
Process stage 2: Material recycling
Process stage 3: Fine particle separation
Process stage 4: Process water recycling
The aim of the recycling system is to achieve the following in particular:
- Volume reduction through separation of the water content
- Recovery of the contained minerals (sand) as a secondary raw material
- Recovery of the remaining solid material in a solid form
- Recovery of the water content
Process stage 1: Material feed
The drilling fluid from the vehicles is first fed into the dosing buffer via a feed hopper. There, the drilling fluid is buffered and then continuously transported to the recycling plant (process stage 2). Excess water is channelled directly from the dosing buffer to the recycling plant in a free fall.
The dosing buffer thus decouples the material feed and the material recycling and therefore equalises peaks and fluctuating volume flows during the material feed. The continuous addition of material to the recycling system ensures a constant separation cut.
Process stage 2: Material recycling
In the recycling plant, the drilling fluid first enters the pre-wash chamber. This contains a water bath. A rotating spiral conveys the drilling fluid through the water bath and segregates it in the process. At the same time, water flows through the chamber using the counterflow principle. The minerals ≤250 µm are washed out and discharged from the system together with the excess process water. The pre-washed minerals >250 µm are removed from the pre-wash chamber via a bucket elevator and fed into the main wash chamber. The main washing process takes place there, similar to the pre-wash chamber, in which the minerals are again mechanically conveyed through a water bath. In order to achieve an optimum washing result, water flows through the chamber using the counterflow principle. A second bucket elevator removes the washed minerals from the main washing chamber and feeds them to the spiral conveyor. The material is partially dewatered via this conveyor and conveyed into the material box. The discharged process water enters an intermediate buffer. This contains an agitator to keep the solids in suspension and thus prevent sedimentation.
Process stage 3: Fine particle separation
In order to further reduce the proportion of minerals ≤250 µm in the process water, the process water is fed to the fine particle separator in the next step. Here, the components >63 µm are separated. This reduction allows additional minerals to be recovered and also reduces the addition of precipitants and flocculants required for the treatment and recovery of the water content.
In addition, the lower mineral load in the process water reduces wear during treatment (process stage 4). The remaining process water with minerals ≤63 µm from the fine particle separation enters a further intermediate buffer with agitator.
Process stage 4: Process water recycling
The centrifuge is fed from this second intermediate buffer via a feed pump. The process water is conditioned by adding precipitants and flocculants. The solids are separated in the centrifuge and discharged into a material box. This solid matter is disposed of (material utilisation).
The resulting centrate (recycled water) is fed into another tank and is used in the recycling process in the recycling plant and as process water. Excess water is discharged after being analysed and released.
Material flows and utilisation
The recycling process described above results in a total of three material flows.
» Minerals >63 µm from recycling plant
» Solids ≤63 µm from centrifuge
» Centrate from centrifuge
Suitability-tested building material
Due to the good quality of the recycled minerals >63 µm, they can be sold as a suitability-tested building material and reused as a secondary raw material. The resulting centrate is also reused in the recycling process. This reuse conserves natural resources and contributes to sustainability. Only the solid material from the centrifuge ≤63 µm is disposed of (material recycling). Possible further uses are currently being examined.
Projected and actual annual volume
Now that the BIBKO® INFRATEC recycling system has been in operation for some time, the settings with regard to processing capacity, quality of the material flows and the consumption of precipitants and flocculants have been continuously improved. This means that the entire system can be operated in an economically optimised range. As a result, the projected input quantity of 10,000 tonnes per year is expected to be significantly exceeded.
Complete solution - Partial solution
The recycling system described above is a complete solution which, in addition to volume reduction, production of solid material and recovery of the water content, also includes in particular the recovery of the minerals contained as a suitability-tested building material (secondary raw material) (process stages 1-4).
Small quantities - more cost-effective variant
If the recovery of the minerals contained is only of minor importance or only small input quantities are available, the recycling system can also be designed as a partial solution. In this case, process stage 2: material recycling and process stage 3: separation of fines are omitted. These are replaced by a special screen with a separation cut of 250 µm. In this case, the recovered material is not washed and therefore does not have the same material properties or qualities as the complete solution. However, as process stages 2 and 3 are omitted, the investment costs for this solution are lower than for the complete solution.
| Summary With the BIBKO® INFRATEC recycling system supplied, the targets set in advance have been fully achieved or even exceeded. This now leads to reduced costs in day-to-day operations and makes the investment in the BIBKO® INFRATEC recycling system a profitable investment in economic efficiency and environmental protection at GRAALMANN GmbH. |