FAQ’s
Is the SPS bead mill the main tool for reducing particle size?
Particle size reduction is undertaken by reactors and bead mill. The process is as follows:-
- De-agglomeration takes place at several points within the reactor, but the degree of de-agglomeration is dependent on the material being processed.
- Polishing The SPS Bead Mill polishes particles that have been through the reactor thereby limiting re-agglomeration.
- Dispersing and Homogenising Material leaving the SPS Bead mill is then fed to the second reactor. In this reactor, dispersing and particle size reduction is achieved and the material is thus homogenised.
What level of foreign particle contamination can be expected?
This depends on the hardness of the material. Hard material has more effect on the beads than softer material. But the SPS bead mill is designed to minimize wear and therefore very low levels of contamination are experienced.
What is the maximum concentration of particles in dispersant that Dena can accommodate?
This depends on the material, but 80% concentration, by weight of material, has been achieved. However, for low density material (typical in pharmaceuticals) the maximum concentration is 40% by weight
Does dispersant have to be a liquid at room temperature?
Dena produce two standard machines usually used for Laboratory and sampling purposes. The dispersant used in these machines is usually a liquid at room temperature, but on larger, individually designed and specified machines used for pilot and full scale production the temperature range is from -20 to + 80 Celsius. The system can in principle be used with liquid dispersants from -50 to +180 Celsius. The critical factor in temperature is the tolerance of the PTFE seal.
Reactors alone can withstand temperatures ranging from -100 to +750 Celsius. The high temperature tolerance enables autoclave cleaning of the Reactors.
If Dena is operated at room temperature what heat increase could we expect to see during processing?
Processing temperature is dependent on the release of energy at a given point in the system. Some material releases high energy thereby creating high localised temperature, but when we use cooling water at 12 Celsius, the temperature at the outlet is 20 to 35 Celsius
Could we operate Dena at say -50 Celsius?
Dena could be operated at -50 Celsius but it would need to be specially designed.
What pressure does the whole system take?
The whole system has a standard working pressure of seven bar (100 psi). Where higher pressures are required, it is possible to fit an intensifier. The whole system (including the SPS Bead Mill can cope with 20 bar (280 psi). For operations in which the reactor alone is used, pressure can be applied to 550 bar (7700 psi)
What is the range of machines on offer by capacity?
Two standard machines produced.
- DM Minimum 75 CC - Maximum 150 CC
- DS Minimum 500 CC - Maximum 1500 CC
Pilot and production machines are tailored to meet client's output specification. With SPS mills in place the maximum is about one tonne per hour. Where reactors only are used, the maximum is over 3 tonnes per hour.
Could machine be used for dispersion only?
Yes, but without a mill. There is, in theory, no limit to the viscosity of the material that can be handled, but we know that it is possible to process material up to 4000 poise.
Are there any problems in dealing with electrostatically charged material?
This depends on the behaviour of the material as it passes through the piping. The reactor does not recognise electrostatically charged material. But on exit from the Dena, System, a charge on the surface material may force re-agglomeration. It all depends on the material's formulation.
Can it be sterilised?
Yes following air purge, the whole system can be sterilised using: Steam (up to 150 Celsius) any detergent (alcohol etc.), however the PTFE seal can be damaged by some solvents - so we would need to advise you. The whole system can be easily dismantled for individual component cleaning if required.
Why is reactor shaped the way it is?
Mainly to enable optimum configuration of internal elements, and for identification purposes (we have a range of over 36 reactors). Reactors can also be jacketed to ensure temperature control.
Could we produce five litres a minute of particle size reduced material?
Depends on material
How does the machine handle material that segregates rapidly?
An example of rapidly segregating material would be sand and water. The turbulence and mixing function created by the Dena System ensures that material remains in suspension throughout the process.
How do you scale-Up?
Use evidence from trials to determine configuration of production machine number of lines contained with machine depends on output volume required.
How can you get the same results in a single pass on production machines as you achieve after several hours of processing using smaller machines?
We work out time, flow rate, and number of units required to achieve the desired product. For example the DS 100 is a sampling machine produced by Dena. It typically handles 1000 Millilitres of material at a flow rate of 250 ml. Thus completing one pass of all material in four minutes in this example, the process material achieves specifications in 20 minutes.
To scale up to 1 litre per minute we would divide the time required for the sample (20 minutes) by the number of minutes required to single pass one litre of material (4). This means we need to design a five unit machine to meet client spec, of one litre per minute.
Obviously, size of reactor would be increased to the optimum (creating more chambers) and larger bead mills used in scale-up.
How does Dena cope with material that has either plastic or elastic qualities?
SPS Bead mill should not usually be used to process materials exhibiting standard or high viscous plastic or elastic material qualities. Dena high pressure reactor system homogenise the product and reduce particle size.
Where is pressure produced in the system, is it greater in some parts than others?
Pressure not equal throughout the system. Greatest pressure is achieved in the SPS Bead Mill and the reactors. It is necessary to have high pressure in the reactors to achieve optimum flow rates (60 - Metres per second) and in the SPS Bead Mill for reasons given earlier.
When process is complete, what % of material is recoverable?
The use of the air purge enables 95% of the material to be recovered on a recycling machine. For pilot and production machines the proportion is much higher 99.8%.
What is the optimum flow rate?
Without the mill it is about 30 litres per minute in one line. This is achievable using water/oil oil/water or oil/oil materials.
What is largest particle size that machine will accept into the system?
Up to 3 millimetres (3000 microns)
What is the maximum viscosity that smaller machines can handle?
Capacities are:-
- DS 100 - Ten poise
- DM 100 One Poise
Dena system is able to produce finer particles with much greater uniformity than other conventional types of machine. All products can be processed with a single pass, and recycling of materials is not necessary for most cases.