If you are thinking about purchasing a freeze dryer, either for the first time or as an upgrade to your existing freeze dryer, you may find it helpful to consider the following points.
Why freeze dry?
Freeze Dryers are used for preserving a wide variety of product types, as diverse as pharmaceutical preparations, foods and beverages, soil samples, flowers and archaeological artefacts. The common objective is the long term preservation of a product without affecting its integrity.
Freeze drying (also known as lyophilization) is a form of dehydration. By freezing the product and lowering the pressure, the moisture content of the product is removed. The freeze drying process facilitates preservation of the original shape, colour and properties of the product.
Step 1: Freeze drying trials
Have you carried out freeze drying trials of your product? Trials will help to determine how your specific product reacts to the freeze-drying process. For example, how long it takes to freeze dry a batch, how much ice your product generates and, importantly, how much it costs in terms of capital equipment and running costs.
Trials can be accomplished either by using a company that offers contract freeze-drying, or by hiring equipment and carrying out your own trials. MechaTech Systems offer benchtop freeze dryers for monthly rental.
Budget
What can you afford? Freeze Dryers are expensive – fact! Prices vary according to equipment quality and manufacturer, but a good quality, 5Kg (ice condenser capacity). -55°C benchtop freeze dryer in the UK, including chamber and vacuum pump is likely to have a starting price over £10,000. For pilot and production scale freeze dryers, prices vary from tens to hundreds of thousand pounds, usually determined by the condenser and chamber size, and temperature and control requirements.
Temperature
What Condenser Temperature do you need? A freeze dryer typically has a condenser temperature of -50°C as a starting point. This is suitable for many product types, but not all. It depends upon the freezing (eutectic) point of your product. For example, if your product has a freezing point of -20°C, then a -50°C condenser temperature is fine, but if your product has a freezing point of -70°C, then you would need a condenser temperature of -85°C. MechaTech Systems offer freeze dryers with condenser temperatures of either -55 °C or -85°C.
What Chamber Temperature do you need? Many small lab freeze dryers, such as Benchtop Freeze Dryers and the larger Midi Freeze Dryers, are modular: this means that you can choose the drying chamber – often an acrylic chamber, perhaps with a tray accessory – or a manifold or chamber with ports for flask drying. In this instance, pre-freezing in the chamber is not an option, so your product must be pre-frozen either in an external freezer, or snap frozen in liquid nitrogen. Heating your product, if appropriate, may speed up the freeze-drying process. For this purpose, the LSAD6H Heated Chamber from MechaTech Systems has a temperature controller and heater mats.
Larger, pilot and production scale freeze dryers, such as the LyoDry Maxi, LyoDry Heritage or the LyoDry Grande include integral, temperature-controlled chambers or shelves. You can both pre-freeze and heat the product. MechaTech’s chamber freeze dryers are typically available with chamber temperatures ranging from -60°C or -40°C, to +60°C.
Capacity
What Condenser Capacity do you need? A given condenser capacity refers to the ice capacity of the freeze dryer condenser per batch, before defrost is required. This is determined by how much moisture is in your original product, which converts to ice during the freeze drying process. This is particularly important if you have a very wet product, which is likely to generate more ice. For example, the LyoDry Compact benchtop freeze dryer has an ice condenser capacity of 5Kg, before defrost is required.
The LHS60 LyoDry Heritage has an ice condenser capacity of 60Kg before defrost is required. If you don’t know how much ice your product will generate, trials will help you to determine this.
What Chamber capacity do you need? i.e. How much space do you need for the product you wish to freeze dry per batch.
Smaller, R&D freeze dryers, such as the LyoDry Compact, are often modular, so you can choose which chamber/drying accessory you need. This might be an Acrylic Chamber, for bulk samples, often with a tray accessory, for freeze drying multiple samples. Or a manifold accessory, for attaching flasks. Or a combination of both so that you have different options available, for example the LSDCV 8-port lidded acrylic chamber. See Freeze Dryer Accessories for LyoDry Freeze Dryer accessory options.
Pilot scale and production freeze dryers usually have an integral chamber, with a set number of shelves offering a total chamber capacity. For example, the pilot-scale LyoDry Maxi Freeze Dryer is available with either 3, 4 or 5 shelves, each measuring 360mm W x 480mm D, up to a total of 0.86m2 drying space. Whereas the LSH60 LyoDry Heritage has a chamber housing 5 trays, providing a total of 5.2m² drying space.
Solvents
What solvents are involved in the process? Usually, the only solvent present in the freeze-drying process is water. In which case, any chamber is suitable. However, some organic solvents can cause an acrylic chamber to corrode, especially if a high concentration of corrosive solvent is present,. In this instance, a stainless steel chamber is a better option. You may also need to protect the vacuum pump with a chemical trap and sorbent.
Control What level of control automation do you need? Entry level, laboratory freeze dryers will usually have a basic digital controller and display, showing temperature, vacuum level and readiness. The operator needs to follow certain steps, such as pressing the ‘Pump On’ button to switch on the vacuum pump, when the freeze dryer display indicates that it has reached the correct pre-cooled temperature. For more closely controlled laboratory freeze drying on a small scale, the LyoDry Benchtop Pro and LyoDry Midi Pro offer touch screen control, data logging, trends, pressure control, USB and ethernet comms.
Pilot and production freeze dryers, such as the LyoDry Heritage, Maxi and Grande, have more comprehensive controllers, usually a touch screen PLC, with pre-programmable, freeze drying ‘recipes’ and endpoint determination. These provide product protection and require only minimal operator intervention. They often include process and product temperatures variables, and real-time systems status and fault indicators. They also have comprehensive alarm management systems, and the option of remote view via an external computer.
If you’re freeze drying in vials, some pilot and production freeze dryers, such as the LyoDry Maxi and Grande, also offer automatic stoppering of vials.
Space and Logistics
Last, but not least, where will your freeze dryer be installed? A benchtop freeze dryer can sit on a lab bench, or a purpose-built trolley on castors so that it can be moved around the lab.
MechaTech Systems also manufacture the LyoDry Midi modular freeze dryer, which offers a larger condenser capacity (18Kg) than the benchtop freeze dryer (5Kg), but is specially designed be positioned next to a typical laboratory bench.
The LyoDry Maxi has a built-in chamber on top, so needs height, but is specially designed to fit through a standard laboratory doorway.
The LyoDry Production Freeze Dryer, however, is a through-the-wall design – so only the chamber doorway and operator control are accessible in the clean room, whilst the mechanical parts such as the vacuum pump and condenser are in a separate room.
To summarise:
Have you carried out trials? What can you afford? What condenser temperature and chamber temperature do you need? What condenser capacity and chamber capacity do you need? What solvents are you using and what is their level of concentration? What level of control do you need? How much space do you have?
MechaTech Systems manufacture LyoDry Freeze Dryers, from our Bristol, UK facility.
We provide advice, quotations and also practical help in the form of rental benchtop freeze dryers for carrying out trials of your product. For further information, please contact us: enquiries@mechatechsystems.co.uk / +44 (0) 1454 414723 or visit https://www.mechatechsystems.co.uk/freeze-dryers.