I believe you have a bigger problem; your circuit is effectively not doing anything but probably sorting by size. If your circuit feed is at 58.8% Fe and your tails are 55% by weight of the feed at 58.1% Fe this means you product is 45% by weight of the feed at about 60% Fe.

You probably need to look at a different circuit (flotation?) as you are throwing away a lot of iron.

Let us not focus on equipment; a spiral does not know whether it is being used as a rougher or scavenger. Look at the products from any unit and then decide what to do. For any gravity separating unit like a spiral, there are design variables and operating variables. Each of them in turn has interactional effects. Please look at ore characteristics/product characteristics and then discuss/ decide.

We will work out as per your suggestion. But, I have a doubt in my mind. We can change the operating parameters but not design variables while it is in running mode. The design specifications for Rougher spiral, Cleaner spiral and Scavenger spiral are different from each others, like pitch, through angle and turns. Now, what we are feeling means, if we use Cleaner spiral as scavenger spiral these design parameters may not produce good yield and recover. Still we are in dilemma position.

I am happy you got what I wanted to convey.

Have you also tried using Jigs? Jigs are preferably used for Iron Ore circuits.

Please do not think of another equipment, the sizes to be treated and the liberation studies should indicate what equipment to use; in general jigs are for coarser size range compared to spirals. As a good doctor (here mineral engineer) do not prescribe the medicine (equipment) without pathological (mineralogical) studies.

We are not ready to go for another equipment. We will work out with spiral only; however my material size range is -1mm +75 microns which is suitable for spiral only. As a mineral processing engineer we will try to get good grade and yield by changing operating variable only. After seeing the results, we will make decision.

Your particle size range would also work well with tables. Also i need to disagree some with previous comments, spirals do come with alternative configurations (pitch, starts, water addition, withdrawal points and such). In fact a cleaner and a scavenger spiral would normally look different from each other do to what the cleaner and scavenger circuits are doing.

In addition let’s get back to what you are trying to do. A rougher cleaner circuit is normally used to get maximum grade and not to worry much about losses, assumes losses are in locked or unrecoverable forms. A rougher scavenger circuit is aimed at maximum recovery regardless of grade. Often the rougher portion produces a on spec grade while the scavenger product is reground and then cleaned.

We agreed with your words. As you said, Rougher Cleaner circuit will give better grade than the Rougher Scavenger circuit, we are highly accepting this. But here, we are little bother about yield%. However, we will go through by both kinds of circuits.

Let me explain couple of points together.

I am not disputing about the new designs and improvements in spirals. As a Mineral Engineer I would be very careful in selecting a spiral for composite ores like iron ores; I have no problem with spirals if we are treating beach sand minerals where most of the grains are well liberated and there is significant differences between the minerals groups we are attempting to separate. With complex (even simple ores) we have liberation/partial liberation characteristics which in turn would lead to equal settling particles (partially liberated particles going along with liberated ones having the same settling velocities.)

I do not understand how you are getting (or tuned your operations to give you) higher grades in rougher and lower in cleaners. Conventionally we tune operations to get higher recoveries in roughers and get the required grades in cleaners.

Thanks for valuable suggestions.

From the data it appears both your spirals are not balanced properly. Cleaner spirals cannot be used for scavenger duty. It would be much more effective if you increase yield in the rougher by producing a lower grade concentrate, say around 61% Fe and clean that in the cleaners to 64% Fe. This will have an immediate effect on the volume of final tails, with some increase in middling tonnage. The basic objective in rougher is to maximize recovery and produce a clean tail which could be rejected. From your description I am getting the impression that you are using the middling thickener to handle final tailings too, as it is of high grade, which is not correct. As the final tailing tonnage is much higher than the middling tonnage /volume. Surely you must be having a tailing thickener as well. You should also look at the % solids in rougher & cleaner spirals as these have a huge bearing on the overall mass balance around the circuit. But I can assure you that you can achieve much better result by balancing the circuit.

Well explained. I am sure that plant needs a good audit and fine tuning.

As you suggested, we will do some more experiments on rougher - cleaner circuit by balancing circuit. Unfortunately, if we not get expected results, then we will approach some engineering company (audit).

I appreciate your response and that you are planning to try out the tests suggested. If you do require a plant audit then our company CDE Asia Ltd could be of service. We have an agreement with GHD of Australia for such work as plant audit, preparation of feasibility, basic engineering.