CRS Autoclave Oven 2.0

Purpose and Description

The CRS Autoclave Oven has been developed as a productive and reliable machine for making multiple individual experiments within one trial. It is therefore ideal for screening purposes, but also for quickly producing long series of reliable experimental data. However, its general design makes it suitable for a whole range of experiments that can be performed in a pressurized rotated autoclave – it’s not at all limited to cooking.

The system is highly automated with an advanced, yet easy to use, PC interface. It requires little operator attention while in operation. In most experiments the machine can be started and left running by the operator until it finishes automatically, including the rapid cool-down of autoclaves. Data acquisition and logging is done automatically.


An overview of the Autoclave Oven

Some examples of the application of the Autoclave Oven include simulation of conventional batch cooks, prehydrolysis, oxygen delignification and pressurized oxygen or peroxide bleaching.

The autoclaves all have individual temperature sensors and each has its own H- or P-factor sampling. The autoclaves are safe, easy to work with, and have excellent mass and heat transfer properties.

Technical overview

Design pressure: At least 20 barg (depending on autoclave type)

Operational pressure: 0 – 18 barg (applicable to the gas option)

Design temperature: 250 C

Operational temperature: app. 40 – 190 C (inside autoclaves)

Materials: 316L equivalent on all process parts, 304 equivalent on supporting structures.

Vessel sizes: Autoclaves can be 3 L or 1.5 L or 0.5 L

Number of vessels: Maximum is 8. However, choosing 3 L autoclaves limits the number to 6.

Heating: 20 kW

Shaft rotation: 2 – 20 Rpm


Schematic overview of the Autoclave Oven


The autoclaves are made in three different sizes. Extra autoclaves can be ordered as an option and each set can be different if need be, for instance of a different size or teflonized. The oven can be equipped with 6 or 8 autoclaves depending on choice at design. However, not all combinations and numbers are possible so check with CRS first before deciding on a set-up.

A set-up of 8 autoclaves of 1.5 L each – note the individual temperature sensor cables

A set-up of 8 autoclaves of 1.5 L each – note the individual temperature sensor cables

Autoclave systems in general face two major challenges. One is heat transfer and one is mass transfer. Both these challenges are rooted in the fact that there is no externally driven circulation of the liquor inside the autoclaves. However, the CRS Autoclave Oven’s unique design – resulting from years of experience of working with these systems – meets both these challenges very well.

The CRS Autoclave Oven has an advanced temperature control, which dynamically manipulates the oven temperature, through high power heating and equally powerful water cooling, to achieve the desired autoclave interior temperature – allowing for both ramping at different rates as well as for stable temperatures. The temperature spread between autoclaves is small compared to other hot air systems and also continuously monitored.

The autoclaves are mounted in such a way that rotating them creates a swirling motion inside them in order to achieve the best possible mixing of liquor and solids. Furthermore the speed of rotation is relatively fast, and also possible to control through recipes.

A very complex temperature profile composed of several ramps – the colored lines are the individual autoclave temperatures tracking the white set point line

A very complex temperature profile composed of several ramps – the colored lines are the individual autoclave temperatures tracking the white set point line

The gas control option allows mid-process gas increase or gas release from the autoclaves, without having to remove them from the oven. The autoclaves are simply stopped (automatically) in an upright position and the operator can work with the pressure control from outside the oven. This is a major increase in safety as well as in experimental quality. Any gas which is allowed for the process can be connected to the system.

The oven operates at temperatures up to around 230 C. Temperatures in the higher end are necessary to provide enough ramp rates of the autoclave interior temperatures. Heating up the oven is done with a powerful electrical coil heater, with a high capacity fan to ensure a high air flow through the oven. Two water spray systems are used to quickly lower the oven temperature whenever necessary, and also to perform a rapid cool-down of the autoclaves by spraying directly onto them.

Inserting and removing the autoclaves is a quick procedure. Even if the oven is running a predefined recipe it can be paused at any time, which will stop the fan and the heater. Opening the oven doors will also stop the fan and the heater on an interlock. The autoclaves are removed or inserted one by one and secured with a quick-snap. The autoclaves can be handled even when very hot, as long as protecting gloves are used. A cooling bath on the side can be used to run an external rapid cool-down. That way the autoclaves can be removed at a certain individual H-factor for instance.

The efficiency of the autoclave oven is very much depending on the logistics of the autoclaves – charging & discharging. The autoclave oven itself is ready for the next experiment as soon as the previous one has ended. If using two sets of autoclaves it is possible to achieve a high throughput.

The oven is made in ordinary stainless steel. The autoclaves are made in 316L quality steel, with a design that minimizes weight to make them easy to handle. The lid can be removed for charge and discharge and also has a quick-fit and a valve for easy insertion or removal of liquor or gas. A holder for the autoclaves when they are outside the oven is included in the delivery.

A 1.5 L autoclave from the CRS Autoclave Oven 1.0 (previous model) with lid taken off – note the quick-fit on the lid

A 1.5 L autoclave from the CRS Autoclave Oven 1.0 (previous model) with lid taken off – note the quick-fit on the lid

The Autoclave Oven is controlled from a PC, with an HMI system developed in a standard industrial framework, Wonderware Intouch or similar. The program is designed with the ambition to be easy to use, offer broad functionality and flexibility, and also to respect safety.

HMI program showing an active experiment

HMI program showing an active experiment

All CRS HMI programs are quite similar in both appearance and logic. They use a common data format which makes it possible to attach several machines to a common database if needed.

A recipe program allows recipes to be built at any time before the experiment is run. The recipe program can be installed on other computers as well, though unless a server solution is also installed by CRS any new recipes will have to be copied manually to the control PC. The recipes can be both flexible and quite unique – allowing complex temperature profiles and varying rotational speeds of the autoclave shaft. A rapid cool-down can be triggered automatically on a set time or a certain average H- or P-factor.

Recipe program (common type with some other CRS machines)

Recipe program (common type with some other CRS machines)

The system will continuously log temperatures, H- and P-factors and other control attributes to either a database or CSV based files (which can be viewed in a spreadsheet program like MS Excel).

On a lower level the machine is controlled from a PLC inside the electrical cabinet.

Scope of delivery and options

The standard scope of delivery includes the following:

  1. Complete autoclave oven.
  2. One set of autoclaves (larger ones have one CE label per set).
  3. External holder for autoclaves for charging, discharging and storing them outside the oven.
  4. Control computer with all necessary programs installed. Network cables and switch.
  5. Required licenses for hardware and software.
  6. Documentation
  7. Connection points for required supplies.

The options follow below. Some additional customization or options are always possible, please inquire.

Option 1:          Start-up & training – one week on site by one engineer from CRS, assisting with practical issues for the installation as well as doing the start-up and training of operators. The customer will need to provide the necessary resources for bringing the machine to the correct location, as well as connecting it to the supplies, but CRS can supervise where needed.

If this option is not ordered the start-up has to be done by customer. However, in such a case CRS will be happy to receive the customer in our work-shop for a one-day free training and walk-through of the machine.

Option 2:          Spare part package – a selection of spare parts aimed at giving the least possible downtime in case parts fail. Spare parts can of course be order individually at a later stage if needed.

Option 3:          Gas control – a gas connection to each autoclave, fed through a common line from outside the oven. Manual control valves and a manometer for gas injection and/or removal are on the side of the oven. A special positioning control of the shaft ensures that the autoclaves are stopped in an upright position, to prevent liquors from being extracted by mistake.

Option 4:          Extra autoclaves – an extra set, either in a different size or the same size. These can be in other materials, teflonized or otherwise specially adapted. Please inquire for more details.

Installation requirements & practicalities

The system has some necessary requirements that need to be fulfilled in order to run it. These have to be prepared by the customer before any installation is to take place.

  1. Power connection – the requirement is a 3-phase 400 VAC 50 Hz connection at no less than 50A capacity. Other setups, like other voltages or 60 Hz, are possible but please check with CRS first.
  2. Water connection –a water pressure of at least 3 bar is required. The colder the water is the quicker the cooling and the lower the temperature range of operation will be. Tap water quality is preferred.
  3. Drain connection – the drain connection must never be blocked or restricted, there has to be free flow at all times. The drain water can reach temperatures of 70 C or above, though the quantities will generally be small.

Vent connection – the vent connection must also never be blocked or restricted in any way. This is even more important than the drain outlet and a major safety requirement. A blocked ventilation outlet can lead to pressure build-up inside the oven. The oven will vent out steam intermittently. A large room can handle this without too much condensation in the room, whereas in a smaller room a vent pipe (again – it has to be open and not restricted in any way!) should be directed outward

Additionally there are some less critical but nonetheless important aspects to consider.

  1. Safety – the system should be used in accordance with what the risk analysis states. Please make sure that the requirements stated in that document can be met with the chosen lab setup. Note also the special hazards related to working with autoclaves.
  2. Noise – the system produces a monotonous noise from the fan whenever it is in operation. Consider placing the system in a room where noise can be tolerated. Alternatively set up a sound barrier (like a surrounding wall) around the system.The machine weighs around 1,000 kg. It can be supported by machine feet or rubber mats (included with the delivery). The outer measurements of the machine and the recommended floor space are shown below.


To transport the machine into a room the door needs a width of at least 1400 and a height of at least 2050.