The basic items are the density and viscosity of the pulp, and the pressure from this on the rakes.  If you have an existing thickener (as Maaden probably does) then I'd begin by taking a failed unit to pièces and reverse engineering to find out why it failed.

Then having spent too much time on the project, I'd go to a reputable thickener supplier in the area (someone like EIMCO KCP in India) who I know very little about, so this is not a recommendation to select them but they do have a product name to defend), and ask them to design a thickener.

I maybe getting older, and this is no reflection on you Saeed or on other correspondents who ask for step by step instructions on gold elution and refining, but I really wonder what is going wrong with either our (the global "we") university education of process engineers, or our on-job training of graduates in their early career?

There is an equation of thickener capacity based on throughput in tons/hr and the base area of the thickener, but I'm loath to disclose it unless the engineer asking has some understanding of steel thicknesses and foundations for the tank. These are numbers I learnt over many years but having rules of thumb can lead to catastrophic failures when the basic concepts are missing.

You can probably work it out for Maaden, by taking the total thickener area and design throughput.

If you are interesed in other "design parameters" I'd suggest you get hold of McIntosh Rules of Thumb (chap 25 & 26 are on Mineral Processing

http://911metallurgist.com/C/Engineering_Rules_of_Thumb.pdf and

https://rsteyn.files.wordpress.com/2010/07/thickening-basics.pdf

Also the standard mine engineers handbook has always been the latest issue of "Perry".

Do you have settling or test work data? That's the first place to start.

I'm very thankful for the the valuable post you wrote, definitely it will help.

Bill, this is the problem, I miss the start point, as you mentioned, I will start with settling data.

I came across technical people some 30+ years ago who ran a all Hydro Refinery, but had absolutely no clue of how their thickeners actually worked! We performed on-site testing and video-taped a performance that reproduced problems that they were experiencing. I watched in amazement as they had an "ah ha" moment, and left me scratching my head in disbelief.

Take a look at the Sedimentation chapter in Wills' Mineral Processing Technology (7th Ed). The discussion and quick look through the chapter references will provide some underlying understanding and guidance on this design and asking the right questions and understanding the answers.

All of the above is good. In my experience however it would be a big step for someone who has not designed a thickener to endeavor to do one from a low starting point of understanding of the principles etc.  It is reasonably easy to determine a thickener area requirement from settling data but that is simply the first step on a fairly long journey.

You must apply judgement to the calculations to allow for surges in feed rate and for process plant tonnage increases, ore mineralogy etc. Rakes and rake torque control is also very important. The process control systems need a very good understanding if the thickener operation as well.

My advice is to get a basic understanding of the principles and then discuss your issues with the experts i.e. the thickener suppliers and rake suppliers and get them to look at a design which suits your application. This is a large capital cost we are discussing so the best advice will come from those who know how to design these items from the start. Don't forget you must have good representative samples from the start.

I have worked with classifier of rakes for but of 15 years of the mark Outokumpo, treating cloudy solutions coming from the treatment of sour waters and cyanide destruction. The objective has always been to recover the clear water and to extract the heavy metals. In my alone experience we carry out sedimentation tests to choose the best floculante since for the design construction and installation was taken charge to a supplier of the mentioned mark.

If he/she comments the objective of the prospective design perhaps I can comment something.

Maya, am ready to read your valuable advise since you worked for 15 years with classifier technology.

Not yet I understand the objective of their design. If you comment so that operation type can comment with some clarity my suggestion. 

When the supplier not yet gives a team, the operation of the plant it begins his activity and it is ignored that type of cloudy solutions will try, even the magnitude of the required design, then they are carried out sedimentation tests in laboratory and also to select the best floculante that serious feasible to use in the team which has controls to determine the levels of very dense muds that are necessary to evacuate and the clear water of it overflows.

Well not if I'm the right person to answer but I know the topic in question, and my recommendation on design issues for these teams is the work in the laboratory sedimentation tests with the parameters you handle pulp, starting from there there are some methods to determine final sizes of units thickeners as Coe & Clevenger or Talmadge & Fitch methods.

I can share a document for your review better, contains enough basic information and remember, we never stop learning despite having 1000 years working.

In the tests of the laboratory we determine what we call the terminal speed, the diameter and the height of a clarifier or sedimentation tank. The team, materials and disposition of the pipe and required controls enter of specialists in the plan and construction. These prove of the laboratory they have been of a lot of utility to build puddles of sedimentation of great utility since in the operation of the plant the solid type it allowed their application.

In first time you need to be sure that you need use a thickener, the size and kind of thickener depends of volumes of pulp, reology of ore, turbid and destination of UF solids. The big difference of thickeners are if they are High Capacity or Conventional. They need to be feeded with a max range of 30%of solids. The UF its in The range of 50 - 56 %solids and they have auto dilution in the feedwell for big capacity, the conventional its in the range of 50 - 54 % of solids. If you need a bigger %solid in the underflow you must think in a paste thickener. But (it's a good idea) you can increase %solids in the UF of a thickener putting a dewatering screen. I have more information about this process of sedimentation and filtration.

Thank you everyone.