Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal

Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal 2017-04-04T06:57:46+00:00
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Tailings Filtration Technologies and Systems (24 replies and 1 comment)

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

To get a proper flotation system, we have to filter the cleaner tailings from Tungsten concentrates after a cleaning flotation process (mainly sulfur and Arsenic). What Tailings Filtration Technologies and Systems is it better to use a drum filter or disc filter? What are the advantages of each one? The reason is because we need to handle our Arsenic and Sulfur safely and almost dry for final disposal.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

Depends on the capacity, even how high is your plant. At high altitude levels the low air pressure are in favor of the filter press. Al high altitude on the disc and drum you need higher suction pumps, in general for small medium capacity I would prefer filter press.

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

Your question is very clear (drum or disc filter), but the filter type selection, in our case, is a complex action, due to process, environmental and financial criteria. In addition to valuable operation conditions mentioned by Jorge, you need take into consideration the following data of filtration process:

1) Tailing size distribution;

2) Slurry temperature;

3) Final cake moisture.

The tailing size distribution and slurry temperature (by its viscosity) have a direct impact on the filtration efficiency. The final cake moisture can be selected on the financial criteria (filtration and cake drying costs - CAPEX and OPEX). Without the knowledge of these process data is difficult to provide you the right response to your question. I met similar situations generated by tailing and/or concentrate filtration. I suppose you have already a filtration phase and you can use the available operation data.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

Make sure of the PSD of the material you wish to filter. Drum and disk filters often cannot filter very fine materials and a filter press (horizontal or tower) is required because a proper filter bed is formed. Do a proper investigation on the capabilities of each filter don't just go on the general info of the supplier.

Bill Rico
2 years ago
Bill Rico 2 years ago

When the drum and disk filers can't do due to various condition of the material like PSD, fines, viscosity, etc. Then explore the press filter with automatic water cleaning system.

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

We are using DIEMME filter press both for concentrates and for tailings.

Ace Levy
2 years ago
Ace Levy 2 years ago

The last process phase of our project was the sulfide flotation (pyrrotite removal). After sulfide flotation, the fine product of 0.030 mm size (D80) is submitted to the filtration aiming the final moisture of 6%...7%. Taking account of the very fine size of the product and low temperature of the slurry (3 degree C; high viscosity) we proceeded to the filtration with Bokela, Germany and the test results met our requirements. We are in touch with Diemme people and their equipment is OK too. Due to environmental requirements, we expect to proceed to the flotation tailing before their disposal. If you need further information or to introduce you to Bokela or Diemme.

Marshal Meru
2 years ago
Marshal Meru 2 years ago

All comments above by colleagues are valid and also to an extent true. There are several factors that can effect filtration rates and these are PSD, feed sg, clays, any washing requirement which extend cycle time. Depending on your -40um fraction I would suggest doing test work with one of the filter suppliers.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

We use Bilfinger Water Technology Filter formerly Diemme filter. One of those excellent filters.

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Depending on the total quantity and the characteristic of the slurry you can decide to use either filter press (I would prefer vertical FP due to much better performance including PLC control) or Horizontal Belt filter. Drum filters are better avoided.

Bill Rico
2 years ago
Bill Rico 2 years ago

If you need to get a very dry cake I'd suggest you think about going with the pressure filter technology. Drums take a lot of space for the capacity they provide and are old technology. The disc filters have less of a footprint than the drums for the capacity. As someone above has suggested the vacuum filters are more inefficient if you are trying to obtain a dryer cake and of course if the particle size of the material is fine they become quite inefficient and will require some sort of filter aid or flocculent.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

I agree to most of the comments made by people earlier. However I would like to submit that please do not try to decide the equipment first but undertake tests on the sample and determine the filtration characteristics of the material. You may adopt all the different methods of tests such as through vacuum technology, pressure filtration technology or a combined system of vacuum & pressure technology. You could also check if flocculent additions are beneficial or not. These will provide valuable data on the cake, whether the filtrate contains any dissolved Arsenic, Sulphur or not, the filtration area required by the different processes and of course the achievable moisture. Based on these information you may appreciate what level of performance is possible through different routes with your material. You can then call upon the suppliers and discuss. You will be able to decide from much higher level of knowledge & confidence.

Marshal Meru
2 years ago
Marshal Meru 2 years ago

Most equipment suppliers will provide testing of your products that require filtering. Pressure Filters can certainly give you the moisture that you need since the drying time can be varied to optimize the moisture content. While pressure filters are expensive, they can virtually run without supervision, other than regular filter cloth inspections/changes.

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

As has been suggested, run some filtration tests. That would typically cost less than $20,000 (possibly as little as $5,000) and is time/money well spent. Outotec and FLSmidth provide a range of filter options and have less reason to select a type of filter that you may not need. Independent labs are fine too, if they are qualified to do filtration testing. A great many are not.

If you do vacuum filter tests, make sure the testing includes air-flow measurement. If you have to guess the vacuum pump sizing because the test engineer didn't measure air-flow, you can spend a lot of money unnecessarily.

As indicated above, you will want to provide all practical information to the test proposal person. Things like particle size distribution, site elevation, upstream/downstream processes, target cake moisture, etc. Even your estimate of those things is better than their assumptions. That will reduce the amount of testing required.

To answer your original question, disc filters are the lowest cost per square meter of filtration area and footprint. Drums are a little more expensive and larger per unit filtration area, but have operating advantages over discs; although recent advances in disc designs have narrowed the window between the two.

Both are continuous processes, which are their main advantage over filter presses of any design. It has been mentioned, but the main disadvantage for all vacuum filters is that filtration driving force is limited to atmospheric pressure, which typically means less dry filter cakes.

I always say that if it can be filtered, a filter press will do it. However, operating costs are very often high because of operator attention required for the batch process. Automated filter presses help that situation, but of course have higher capital costs and cannot be used in all applications.

A reputable filter manufacturer can help sort out all of those details, but will provide you with better answers once you have test data. I will be happy to comment further or suggest someone who can help if this hasn't answered your questions.

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

I think vacuum disc filters are mostly used for very fine particles such as cement, micro-pulverized coal, etc, where a good thickness of cake is built on the filtering surface. But as the filtering surface is almost vertical, the washing of cake is not recommended in disc filter.

While in case of vacuum drum filter operation is easier, we can easily do the cake washing (if required) and can be used for coarser particles also.

As suggested in earlier comments, the test results in laboratory shall be helpful to select the filter: drum or disc.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

Thank you for following up with the washing comments. I considered mentioning it, but decided my note was already too long. Flat-top horizontal filters such as belts or pans have the highest wash efficiency. Discs are near zero, drums in the 60% range and pans/belts are typically over 90%. However, the latter may be three times the cost of a drum filter for the same tonnage of material.

We should be careful about the term "fine" particles. It really comes down to specific particle size distribution. (Particle shape can also play a role in filtration.) One could as easily (and correctly) say that vacuum filters are a poor choice for "fine" particles because they don't have enough driving force.

Conversely, disc filters can be used on coarser particles. It's simply a matter of ensuring the filter components can move enough air and liquid.

The science around large process filters is well established. There is a little variation among different practitioners, but they won't come up with radically different results if they've done their work properly. Get your test data and engage an expert (probably a manufacturer) to select / size the filter(s). That is the best path to maximize the desired results and minimize CAPEX / OPEX.

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

I must concur with the comments made by some of the contributors above that you need to undertake some testing with your flotation product to determine both the filter technology that best suits your purpose and to size the equipment for your operation.

In fact it would be unwise (if not impossible) to recommend any particular method without sufficient data and / or further testing. Each deposit is unique and it is not possible to make an inference that because plant X uses a particular technology for dewatering their tailings that it will work for your operation. Mineral assemblage, liberation / grind size, reagent suite, plant location, target moisture content, etc. will all differ to a greater or lesser extent and will all impact equipment selection.

Any information that you already have can help in decision making and reduce the time and cost of the testwork required. This testing can be provided by a manufacturer or by some independent labs.

Ace Levy
2 years ago
Ace Levy 2 years ago

You correctly mentioned that it is only material characteristics (and also particular application) which really says what type of filter they need.

I believe, this is not only in case of filtration but also for all mineral processing equipment; nothing can be firmly defined for their selection. It is only their test results which indicates their type selection with a strong back up of our experience for that equipment, particular application, selection methodology, our data base for similar application and finally some thumb rules.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

All process, flowsheet and equipment selection needs to be based on proper testing of the ore, with the expert input you mention.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

These discussions are particularly very useful to next generation mineral engineering-- all are very frank and informative.

Now let me add regarding the testing; many times a sample is sent for testing without the Engineer concerned himself not fully knowing whether the testing is done keeping all the factors into consideration and tests are done at optimal machine and process variables.

A good knowledge from the customer/ or a good advice by a person knowing should proceed before sending the sample for testing by a manufacturer of the machine.

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Generally Disc and Drum Filters are cheaper compared to Belt filters. But Belts filters normally offer higher specific filtration rates, which can lead to filtration of higher capacities per unit. More number of disc and drum filters will add up CAPEX for civils and other auxiliary equipment. Belt filters normally provide very high equipment availability compared to disc and drum filters, as they are very simple to operate and maintain.

Where Cake washing is required, there many case studies where multiple disc / drum filters used for cake washing are replaced with one belt filter to filter and cake wash in one unit.

Belt filters scores high where the permeability of cake is high and needs high air flow for filtration. This kind of material would struggle to form cake and hold on till cycle completion in disc and drum (thanks to gravity).

As noted by many contributors 'fines' and 'coarse' are relative and needs to be referred in context.

All types of filtration technologies have their own advantages and disadvantages. More importantly the commodity pricing and economics which dictate the adoption of technology / equipment. For example, Iron Ore sector in India up to early 2000, Majority of the beneficiation plants lived with classifier as dewatering equipment for their concentrates (sun dried concentrates). Barring few government owned technology savvy companies and pellet making companies. Now, Iron ore price can accommodate any find of filtration technology depending on moisture content required in downstream process.

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

Why is not plate and frame filtration an option for you? It would better meet your described purpose.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

Drum and Disc Filters are high maintenance. Belt Filters have the highest wash efficiency. As Roger suggested have you considered a plate and frame pressure filter. I commissioned a plate and frame pressure filter for arsenic removal at Jingfeng Gold Project in China.

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

Very interesting discussions. Everyone at the end is suggesting test work to determine the filtration characteristics. Indeed wise advice. I would only like to add that the test work should be undertaken preferably at site with small size pilot machines which all major manufacturers now possess. Simple laboratory tests with one or two samples do not tell the whole story and are misleading in many instances. Also since it is tailings the alumina level should be kept in mind; it is one of the biggest impediment in achieving good filtration.

Bill Rico
2 years ago
Bill Rico 2 years ago

I agree with your comment about bench versus pilot testing. A bench test won't tell you everything. From a proper bench test you will get information like:

* Filtration rate for vacuum and/or pressure (i.e. - filter size)

* Bottom feed vs. top feed (e.g. - drum filter vs. belt filter, or filter press vs. tower press)

* Cake washing efficiency

* Air flow requirements (primarily for vacuum, but can also be air-dry in pressure filters)

* Approximate operating vacuum or pressure level

As a rule, that is sufficient to select the filter type and size. Of course the sample(s) used, must be representative.

If there are concerns about how the cake may discharge or cloth behavior issues (tracking, blinding, wear, etc.), a pilot test can help answer those questions. A pilot test can also be useful for things like understanding the impacts of process variations and educating plant personnel about the particular type of filter.

johnclark
1 year ago

Do you add a flocculant prior to sending the slurry to the filtration device (using the optimum flocculant dosage for improved filtration)? Kemess Mine in BC Canada used a flocculant prior to pressure filtration and did not need to dry the concentrate.Prior to using the flocculant, the pressure filters did not remove moisture effectively.

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