Many folks ask us to design a plant, sort a problem, quote for a machine. The first question we ask is what is the back end like? Without being rude, we mean have you outlets for all this product we are going to produce. Without refusing the sale we must ask the Why? Why do you want to do it this way? In many situations most of our clients have maybe a basic screen or even a multi-million fully automated plant.
What we see is that even with the most sophisticated plant the basic processing principles have not been followed and the operators are still putting some element of the waste around the plant again because it is not designed correctly. Yes, so much of the plant design is limited by the surrounding environment, wet/dry, inside/outside, space or limited space. There are restrictions but limiting re-handling is important. There is no point having a process that ejects plastic straws that you can not sell or disposable cups that are too dirty or even trommel fines that are not good enough for loss on ignition testing. In concluding, check the process step by step in detail and make it flexible. Sometimes, if the process is efficient then you will have RDF and SRF by design default!
In summary our top 5 tips for processing waste
- Do you have outlets for all the different materials you will produce? Why do you want to process in a certain way? Check yourself why?
- Do we really need that material in that way?
- Are we re -handling or re-transporting material with this design?
- Keep the process simple and remember the feed in method or the machine feeding the material is a very important link in the process. How is the material presented to the first process step?
- Is the system flexible for change?
As we distribute stationary trommel screens around the world we thought we would do a small comparison on operational costs. So how do we compare the overall operational costs of a static Trommel Screen XD720 (726) and a Mobile 720 (726) Trommel Screen. The one cost which we can calculate is the actual operational cost. The other cost is the hidden cost of not having stockpile belts and ease of mobility around a yard if needed. The fines storage can be the same but not the oversize. The table below outlines the cost comparison between two trommel screens the same size hopper and the same size trommel drum. The mobile machine has an additional four collection conveyors and onboard stockpile conveyors. We have used current diesel and electric costs both the European average and North American average as of 22nd October. The diesel engine consumes approximately 10L or 2.64 Gallons/hour. This is efficient for a mobile trommel screen. In electric costs there is only a hopper belt motor and a trommel drum drive motor totalling 25Kw. These motors normally average 60% consumption. As one can see below the Fixed Cost and Variable costs comparison is astounding. The mobile trommel screen is running over double the costs/hour over 10000 hours or five years. We have not considered any labour costs or even variation in filter costs or lubricant costs across the globe. Labour costs for servicing and re fuelling have not been added either which would also increase the costs. Do your own calculations. The question really is, do you need a mobile trommel with all the belts or would a static trommel be more cost efficient. Will one get more lifetime out of the mobile trommel screen than the static trommel screen after 10000 hours?
Total Cost/ Hour Excluding Items Below Europe Electric Static v Mobile Diesel € 14.74 € 32.05
Total Cost/ Hour Excluding Items Below USA Electric Static v Mobile Diesel $ 16.23 $ 35.43
Is the flip flop screen or another type of mobile screener or stationary screener right for the application? MacMachinery have over 20 years supplying and designing waste systems and recycling systems for processing all types of material. One of the most topical materials at present is trommel fines or waste fines. Most of our clients need to perform the LOI (Loss on ignition) test regularly. In order to ensure the client meets the test requirement one needs to design the system to give the right outputs. How do we decide which machine for the trommel fines screening solution? Generally, one can use a trommel screen aperture size as low as 30mm or even 12mm but when we get any increase in moisture or wet weather then we have problems. The system does not have screening problems, but the oversize will be contaminated with oversize material. Obviously, the fine material needs to be in the fines bunker or bay. The XD 518 trommel screen can cope with screening wet fines at 12mm but the +12mm material will have some fines in it, and this is when we choose a flip flop screen over a trommel screen. The Flip flop screen has been in use for over 40 years, so the technology is not new. The use of the flip flop screen in waste and recycling is more recent. One also needs to consider; space, wear, running costs, flexibility as the market changes.
MacMachinery supply flip flop screens or otherwise known as flip flow screens, single deck or double deck new and used flip flop screens. On occasion, we will be forced not to use a flip flop screen, because maybe there is no electricity supply on the site or there is a space issue with the depot. Many manufacturers are now producing so called flip flop screens, but the true test is how many years the machines can operate for in the unforgiving operating environment. MacMachinery need to calculate the size of the flip flop screen required using the density, volume and material composition before recommending which size of machine. Flip flow screens can be as small as 500m wide and only 2.5m long. The next step in the process is whether you need a single deck or a double deck machine. The question here is not about needing three products but will having a double deck make the screening system more efficient or will it improve the next step in the process. The guideline really is keep the process simple and stay with proven processes. What is the next step after screening out the trommel fines or super fine material?