Question regarding GC sampling

[lfcfan]

Hello,

We are currently using Agilent 7890A GC. We are running a cyclic process which consits four steps. I want our GC to take samples only during the first step. During the other steps it should not run or take samples. I do not have any idea how to do it. Can any of you help me on this issue?

Thank you,

[GasMan]

A little more information would be useful.

1. How are you putting the sample into the GC?

2. Are you using a data system? If so which one.

3. Is the cyclic part without sample just the oven program?

Gasman

[lfcfan]

Hi,

Thanks for the reply.

I have given the answers to your question below,

1. The sample is injected automatically after every run.

2. Data system?? We use, Ezchrom elite software to extract the data.

3. Oven program is always constant. Cyclic part is only our process.

Thank you again.

[GasMan]

lfcfan,

It is still not clear to me what you are trying to do. You mention that you inject the sample after every run. Normally, you inject the sample and then make the 'run'.

You also mention that the oven program is always constant. Does this mean that you running isothermal.

At the moment I understand the following:

You inject a sample and collect the data. After the data has been collected, you wish to do the 'cyclic' part of the process. All of this is done with the oven at the same temperature.

If this is the case, I can give you a suggestion.

Gasman




Gasman

[lfcfan]

Hi Gasman,

Let me explain to you bit more clearly.

I have a reactor where I am running a reaction. The main reaction runs for several minutes and after certain time, the main reaction is stopped to regenerate the catalyst. After the regeneration, main reaction continues again. The steps I have mentioned above are automated. So the cyclic process which I mentioned in my previous mail was the abovementioned reactions which run in my reactor.

At this moment, our GC runs all the time, means during the main reaction as well as during regeneration. But I want my GC to run only during the main reaction and during regeneration it should remain idle, means it should not run. When my main reaction starts again, my GC has to run again. All these things need to be done automatically.

I do not have much idea, how to do it. At this moment, I am thinking the following:

During the main reaction, main gas inlet valve to the reactor is opened. If the GC can communicate with this external valve position, probably then the GC can be run just during the main reaction in my opinion. Is there a way to make GC to communicate with external valves?

Please let me know if you can solve it differently,

Hopefully, I have defined the problem better now:-)

Thank you,

[GasMan]

lfcfan,

It is possible to control valves from the 7890. However, this can only happen while the GC is in the 'run' mode.

It is possible to set up the 7890 via EZChrom, to start the GC in a sequence. The GC could control the valve that you mention, and run for the alloted time. If you look in the GC setup screen in EZChrom, and go to the oven program tab, you will see a box for entering the 'Post Run' temperature and the 'Post Run' time. The post run time would be the time that you require to regenerate your catalyst. When the 'Post Run' time is up, the GC would restart the process.

Regarding your valve control, the 7890 has 4 internal valve controls for 24Volt DC solenoid valves that require not more than 500mA. There is a connector at the rear of the GC that has a further two controls for 24 Volt DC solenoid valves that require not more than 75mA, plus two low power relay contacts.

The first thing that you need to decide is which device is to be the master controller of your system. Is it the GC or the device controlling your cyclic regeneration? It is possible to start the 7890 remotely using a contact closure, so if the controller of the regeneration cycle could supply a contact closure this might be the way to go.

Gasman