Key considerations before implementing an in-line NIR process control system.
We asked FOSS process Specialist Ib Haunstrup if he could tell us his secret to success with in-line NIR process control.
The interview can be seen in the video. Having trouble playing the video or prefer a good read? Don’t worry we have transcribed the video, and added headlines for easy navigation.
Where should we measure for optimal process control?
When we are in process, we are sometimes in places where there are very high vibrations, and there are temperature changes, there are a lot of things going on out there. We want, really, to be independent. We want to go in to the process where the really critical point is, not 10 or 20 meters further down, because the vibration is not as heavy down there. No, we need to be in the right place, to be able to react and control our process as tightly as possible. I have been out many times, consulting about where to install.
How to get value out of an in-line process control solution
The most important thing is to know your process and to split it up into different small steps. Then, of course, you can say, "I would like to monitor this and this, in this and this position." This is the first step. The next step is to identify the really critical point. Because the critical point is where we can actually give a lot of value by having continuous results, because then you can react on it. But that's not enough. Finding the most critical point in the process is of course often possible, but you also need to be able to do something.
The next question to be answered is, can I control my process? Because just monitoring doesn't add much value. Yes, you don't have a person running out and in, taking samples. Yes, you have a monitor, but do you know where your processes are? No. To really get value out of an in-line solution, you have to use the results for continuous adjustment of your process. If you don't know how to adjust your process, then there's not a lot of value. Find the critical part, find out how you will use the results to optimise your process, for instance, reducing the variation or moving the production target closer to the specification.
If you want to get the real value out of a process instrument, you will need to react on the results. Maybe reduce the variation and produce closer to a specification, add more water, reduce the protein concentration, and so on, by controlling your process better.
Let me give you an example
Let me give you an example, if you want to measure moisture, protein, fat, fibre and so on. If you get four results out of an in-line instrument, and you have to react on all these four results, how would you control the system based on four different parameters?
I know how to do it with one parameter because then you can open a valve or adjust the pump and stuff like that. If we have two, then we have to have two strings in, to adjust both total solids and fat for instance. That's very complicated because if you just add a little bit of this and then change this one - they are not independent. If you add a third parameter, then it's not going to be easy. What we normally say is; what is the critical parameter in this step of the process? This is used for process optimisation. The other parameters are, you'll say, for monitoring. They may be monitoring something going on further upstream in the process.
You can take any application or any installation of in-line. The most important thing is, as I said before, you have to find the critical point in your process, and find out what parameter is most important to control to optimise your process. I can take an example from a dairy, a flourmill, or a meat plant, it is the same story all over.
If you take a feed mill, there are a lot of places where you can add value by going in-line. You can say; okay, we have the raw materials and we have the mix of the raw materials. Then of course, if you go further into the process, then you make pellets and maybe you add fat. There are a lot of steps. So, to identify the most critical point, is the first step, as I said before. In feed, or in some types of feed, one of the main parameters or the important parameter is of course, protein. How do we control the protein concentration in the final product? Where in the process can we interfere and optimise so we have the exact protein concentration we want in the final feed?
Then you have to go back in your process and find out – where is the main control point if you want to control the protein in the final product? Then you can go further back in the process, and say; here it is, this is where we have to go in. We have to go in and install it, and again - how do we control it? We can say; if we do this and this, then the protein will be correct in the final end. It’s the same if you want to control the moisture concentration in your final product - in the feed product. Then it's another place in the process where you may have to go in to control. Depending on what you're going to do, you have to identify the most critical point, where you can control your parameter.