Capacity Improvement of your Existing Falling Film Evaporator with a Potential Increase on the Dryer Output
- Posted on 18th January 2014
- in Dryers, GLM Hydro
- by Jan de Geest
GLM Hydro Evaporator Problem Solving: –There are several ways you can improve the overall evaporation capacity of your evaporator and by doing so, increase the powder output on your dryer.
The distribution of the product creating the film on the boiling tube is one of the most important things in the evaporator system. At the bottom of the falling film tube, you need to have the correct tube coverage. Tubes that have too high coverage are not good, the tubes take product that should go onto the other tubes and at some point, you can even get problems with boiling suppression of the film. Too low coverage is bad as well, this can create tubes running dry and a local over-concentration of your product. Especially when you have a product that starts to crystallize at higher solids, over-concentration should be avoided at all times. The crystallization not only causes fouling but it also reduces the boiling of the film in the tube and it will reduce the capacity of the falling film evaporator. To be able to run your evaporator on the maximum solid content possible, feeding the dryer with the lowest possible water content, it is very important to be able to run your evaporator close to the limit. All tubes should have the same amount of liquid.
Depending on your product viscosity going to higher solids, you may have to take measures to lower the viscosity. In most cases, this can be done by means of a time/temperature profile change, a slight change in boiling temperatures or a change in the pH of the product, or a combination of it all.
Back and Forward Mixing
Another way to get the best performance out of your evaporator is to make sure that there is no internal back mixing. When the concentrate is short-circuiting from one pass into the other, it will have an effect on the liquid load of the falling film tubes. It will over-concentrate some of the product in case of back mixing. You lose capacity if you have feed-forward mixing, which means that some of the product is by-passing the evaporator passes. Undesired mixing of product can happen in the distribution system or in the sump of the falling film evaporator. So together the distribution forward or back mixing will have a negative effect on being able to run the solids as high as possible.
Typically 1-2% higher concentrate solids feeding the dryer can result in an increase of 4-8% capacity on the dryer.
Cleaning in Place (CIP)
With the optimization of the tube coverage on the evaporator, it may be possible to extend the run time of the evaporator. Extending the run times and optimize (shorten) the CIP times can also be a great way to get more annual production out of your system. If specific parts or places have more fouling than others or if some areas are just harder to clean then it may be worthwhile to explore if there are ways to eliminate or reduce the fouling, or if there are betters ways of cleaning. If a heating system of the evaporator is the problem it may even be profitable to make a parallel pre-heating train, so you have the possibility to run longer and clean the problem area while the parallel system is in production.
Contact us for more information when your installation has these or any other kind of issues.