FREQUENTLY ASKED QUESTIONS:

1. What does ChemiSens mean when they refer to true zero-line and true measurement?
2. Automated chemistry. What is it according to ChemiSens opinion?
3. Why does the CPA202 look different from most other reaction calorimeters?
4. How do I determine Cp with the CPA202?
5. ChemiSens offers three different types of reaction calorimeter systems. Why?
6. Can I operate differnt CPA systems with the dynamic correction included on-line?
7. What are the special features of the ChemiSens Heat-Balance systems?
8. The CPA202 is pre-calibrated once and for all. Why do you then deliver it with a calibration heater?
9. Why is a small reactor volume important for a reaction calorimeter?
10. Is a torque transducer really necessary in a reaction calorimeter?
11. What are the special benefits of the CPA202 compared to traditional reaction calorimeters?
12. Can you point out some particular areas of use where the CPA is really beneficial?
13. Is it complicated to operate the CPA202?
14. Is it time efficient to work with the CPA systems?
15. Why is it important to get the result directly on line in real time?

1. What does ChemiSens mean with true zero-line and true measurement?
Answer:
The output from a true reaction calorimeter is a signal given in true power units (watts) and directly describing the ongoing thermal activity inside the reaction calorimeter. Without any activity the signal is always zero, that’s a true zero-line. If the studied reaction generates a power of XX watts, then the result presented on line should be exactly XX watts, that’s true measurement.

2. Automated chemistry. What is it according to ChemiSens opinion?
Answer:
ChemiSens systems and most other commercial reaction calorimeters include automatic facilities for auxiliary sensors and multi line dosing capability. According to ChemiSens automated chemistry means operations where all necessary process steps can be fully pre-programmed and performed by the system.

The necessity of stable dosing to a reaction calorimeter must always be considered.

Most experiments in a reaction calorimeter are performed as semi-batch operations. One or more reactants are continuously fed to the reactor. With a high-resolution reaction calorimeter any irregular or unstable dosing will be reflected in the measurements. The calorimeter system must be able to handle any necessary dosing of reactants or sampling from the reactor in an automatically controlled way that will not disturb any of the measurements.

3. Why does the CPA202 look different from most other reaction calorimeters?
Answer:
The CPA202 is from the beginning built as a reaction calorimeter with all considerations to be a precision instrument. The reactor itself looks very much like an ordinary small jacketed reactor. The sophisticated measuring devices are located within the base part of the reactor vessel. When the reactor is operating it must be submerged into the CPA thermostatting unit. The thermostatting unit is necessary to establish a uniform thermal surrounding for the reactor. Note that many traditional reaction calorimeters look very different when they are used. They are wrapped in layers of insulation or covered by a box or modified in other ways to improve the measuring capability.

4. How do I determine Cp with the CPA202?
Answer:
There are principally two different ways. Either through a temperature scanning experiment or through a stepwise change of the reactor temperature. In both cases we recommend for the best results to run the experiment with different amounts in the reactor and make a differential calculation. For simple determinations a single experiment is sufficient.

5. ChemiSens offers three different types of reaction calorimeter systems. Why?
Answer:
Our prime system, the CPA202 can solve most problems within reaction calorimetry. For small-scale production or where larger product quantities are required for further testing, the volume capacity of the CPA202 reactor might be insufficient.
For these situations our complement is the CPA122 system.

Some routine tests might not require the sophisticated CPA202. In these cases our CPA102 is a natural choice. The CPA102 is thermostatted by circulating liquid in its jacket. The reactor, when it is operating, is surrounded by air while a liquid surrounds the CPA reactor. In some rare cases the “dry” surrounding of the RM200S reactor might be favorable compared to the CPA102.

6. Can I operate different CPA systems with the dynamic correction included on-line?
Answer:
Yes, it is possible. The dynamic correction compensates for the heat accumulated in the reaction mass and strongly reduces the system time lag.

The heat-balance equation for any reaction calorimeter includes a term q(acc) that describes the heat flow corresponding to the heat accumulated in the reaction mass. In reality the heat balance equation for the whole calorimeter must also include accumulation terms for the different inert thermal masses of the reactor vessel. The CPA systems automatically corrects for the heat accumulation in the known inert reactor masses. The reactor temperature derivative is always calculated. If a value for the heat capacity of the reaction mass is given, this value is multiplied by the temperature derivative and used as the dynamic correction.

7. What are the special features with the ChemiSens Heat-Balance systems?
Answer
ChemiSens offers two different heat-balance systems CPA122 and CPA102 as complement to the CPA202 system. The general problem with the heat-balance technique is to measure the small temperature difference between the outlet and inlet flow of the thermostatting liquid into the reactor jacket. ChemiSens has solved this problem without lowering the flow rate of the thermostatting media. A low flow rate promotes the measurement of the temperature difference but also lowers the control capability of the reactor and might cause reactor instability.

Another problem associated with the heat balance technique is its sensitivity to disturbances from the surroundings. ChemiSens has included separate sensors to measure and correct for these disturbances. The reactor cover is separately heated to avoid internal reflux and uncontrolled heat losses.

8. The CPA202 is pre-calibrated once and for all. Why do you then deliver it with a calibration heater?
Answer:
The calibration heater is used for the regular system validation. The heater is also used for the determination of the heat transfer properties in non-reacting systems.

9. Why is a small reactor volume important for a reaction calorimeter?
Answer:
In most cases the output from a reaction calorimeter is just information. For that reason and the fact that the consumption of sometimes expensive chemicals normally must be considered, the vessel volume should be as small as possible. The minimum size is set by practical considerations. The small volume of our reactor takes into account the space necessary for all of the sensors, both standard and optional, that may be incorporated into the system. The small volume also allows for scaled down reactor conditions such as sampling, dosing of solids, handling of heterogeneous systems, etc.

When studying reactions where energetic compounds are involved it is obvious that the reactor size should be as small as possible.

10. Is it really necessary with a torque transducer in a reaction calorimeter?
Answer:
Mostly yes. Besides being used as a correction in the measurement of the total reaction power , the torque measurements also carry separate information.

Analyzing the torque graph gives valuable information about viscosity changes due to fouling, precipitation, agglomeration, phase inversions etc. This is important information for the understanding of the complete process.

11. What are the special benefits with the CPA202 compared to the traditional reaction calorimeters?
Answer:
The CPA202 presents both the true heat flow and the total reaction power on line and in the real time. You get the true picture of the process with all the details. No time has to be spent on calibration procedures. There is no risk for hiding reactions below misinterpreted baselines.

12. Can you point on some particular areas of use where the CPA202 is really beneficial?
Answer:
The CPA202 is really beneficial for studies of complicated systems. We are then talking about reactions in media’s with changing viscosity due to agglomeration, crystallization, fouling, polymerization, phase inversions etc. Mass transfer controlled reactions can easily be examined by changing the stirring intensity and watch the true result directly on the screen.

13. Is it complicated to operate the CPA systems?
Answer:
The menu system is user-friendly and self-instructing. The reactor is a robust and reliable piece of hardware, easy to lift into or out from the thermostatting unit. The open CPA102 and CPA122 reactor vessels can be placed directly on the bench balance for charging initial material for the experiment.
The reactor armature is easily reconfigured to meet the actual experimental needs. The lid ports and the rest of the armature are compatible with the Swagelok system from Crawford Fittings USA.

14. Is it time efficient to work with the CPA202?
Answer:
Yes it is. You start your experiment directly, run it until you have got the result and then interrupt. You have the true result on the screen and in your log directly. There is no need for electrical calibration pulses before the experiment, each time you change the temperature or the stirring intensity and finally afterwards, when you think the reaction is completed.

15. Why is it important to get the result directly on line in the real time?
Answer:
It’s very time efficient. You get directly the correct response to your changes of the experimental conditions. This is especially beneficial for screening tests. The result/response from an addition or from a change of experimental parameters can be used directly for planning the next experimental step.