- To participate in the 911Metallurgist Forums, be sure to JOIN & LOGIN
- Use Add New Topic to ask a New Question/Discussion about Grinding.
- OR Select a Topic that Interests you.
- Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
Using Add Reply allows you to Attach Images or PDF files and provide a more complete input. - Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.
cyclone pressure in water balancing (5 replies and 5 comments)
I am sure you already know what needs to happen. Any contninous system operates well if it is allowed to attain equilibrium and allowed to continue in equilibrium. any changes that affect equilibrium will affect efficiencies and productivity. one way the deal with is to make sure that you control your feed into the mill from whatever your source is constant, ie.e you need surge capacity before the mill so that feed into you mill is constant as this is critical.
Thanks brighton. Thats a a good idea. But the real problem on the ground is there has been a continuous failure in the crushing section due to liner wear and motor failure, chocking....etc. we fill up the whole stock pile, but the failure on the crusher sometimes lasts 2-3 days. In Which case we will runout of ore if we go with the same tonnage like before at 80-90t/h. This is the problem.
you are totally correct. you want to maintain pressure to achieve same size dist'n. If you add more water and cut cyclone feed density you will make a finer product, dont know if that is good or bad, but downstream density will fall. Large mills have many cyclones in a cyclopac. So removing one is no big deal and gives a stepwise flow control. You are a bit hooped having two cyclones. Your thinking however looks correct
I appreciate that mike. Thanks. We have 6 cyclones. Howevere 2 are running at atime. If I try to add cyclone, my pressure will definitely go down. Its why I choose operating using one cyclone. Our problem is that the size of the apex is static. We cant increase or make it smaller. Nothing automatic means of controlling the apex is attached to it.Of is the same all the time.
It may make more sense to cease operation when the throughput is below a certain cut-off point and to wait until the feed can be re-stabilized. Are there reasons this cannot be done?
The turndown in throughput is also likely having a negative impact on subsequent processing circuits as well. The impact of this instability on their performance probably results in higher losses (and other measures of performance) during these times.
A final consideration - the mill can be expected to produce a finer grind if you reduce throughput from 80 to 30 TPH.
Thanks Robert that helps a lot. I think I need to see how much money I am going to save or loss, if the mill shut down. i will also have a word with the Grinding Technicians on how bad will that influence on mill operating conditions. Because if this is going to happen, we are going to stop 2-3 days a month. That feels a bit strange right? Thanks again.
Effectively you are right, it is key to work with a balanced water balance to maintain pulp density and grading conditions, defined in the design, but it is also important to maintain the working pressure condition of the cyclone and as it is a equipment that is sizing volumetrically, the correct action is to withdraw equipment from the operation as the feed decreases.
Therefore, the action of operating with a cyclone for a feed of 30 t / h is correct, however, the initial feed was 80 t / h, which means two things:
1. The mill is being sub-used energetically
2. Each cyclone in normal operation classifies a mass flow equivalent to 40 t / h
3. A flow of 30 t / h is 25% lower than its normal operating condition
4. The above condition will not allow work to the design pressure condition (85 MPa)
5. Therefore the classification condition will be deficient and consequently the particle size (P80) for the next stage will be inadequate
6. All of the above will negatively impact the metallurgical recovery of the process and the cost of operation (OPEX)
7. Increase pumping speed will only exacerbate the problem further, causing problems of accelerated pipe wear and cavitation problems of the pumps when the pumping box is emptied
My recommendation points to two objectives:
1. Maintain classification conditions defined in the design
2. Reduce operating costs
That said, there are two possible paths of solution:
1. Install smaller cyclones, suitable for processing 30 t / h
2. Use batch operation strategy at a rate of 80 t / h, with no need to introduce any changes in the facilities
The detailed strategy of both options would be as follows:
SMALL CYCLONES:
1. Dimension and install a smaller cyclone, suitable for the new feed rate of 30 t / h, if this condition is transient, or replace with a new battery of smaller cyclones, if the condition is permanent
BATCH OPERATION:
1. It would be advisable to evaluate a batch operation strategy at a processing rate of 80 t / h, starting the operation with the collection of full fine ore (80 x 24 = 1920 tons), which would allow a 64 hour autonomy (2 ,7 days).
2. In addition, during the same 64 hours of operation, an additional 1920 tons of ore could be collected (30 x 64 = 1920 tons), which would achieve a further 64 hours of autonomy
3. The proposed strategy would allow a total autonomy of 128 hours (5.3 days) operating at 80 t / h with 64 hours (2.7 days) of detention, intended for maintenance and replenishment of fine ore collection, among other activities
4. To clear any doubts about the advantages and disadvantages of both options, it would be advisable to conduct a trade off, comparing energy consumption, energy efficiency, availability, utilization and opex.
Regards Néstor Pérez
I'm so thankful Nestor. i really appreciate that. i think the batch operation sounds good, and we can go with that. i will put all the things you said in to account. thanks again
Dear Jovani,
To maintain the pressure at the hydrocyclone inlet , you should maintain the % solids in the range of 45-55 % at the hydrocyclone inlet and it can be very easily monitored ene . Densitometer will sense the pulp density and based on that it will operate the water control valve at the ball mill outlet and in that way you can automatically control the Feed parameters . This is a permanent solution to your problem .
Further more you can reduce the diameter of apex to increase the % solids in the overflow .
Thanks for the suggestion ashutosh. But I dont think u understand the problem. My cyclone feed percent is 55%. But that works out when feed is 90t/h. If feed goes down to 40 t/h , you cant do the correct water balance and continue with 55%. The pump is a cyclone pump. Its impeller is big. You try to maintain the pressure through the velocity of the impeller as usual, your sump will be left empty sooner. the pump will suck air and cause problem. I dont want this to happen.this is why I ask the professionals for other options of there is any. I in the comment I wrote before, my apex is static. If it can be altered, it was the best shot. Anyways Thanks for the suggestion.
hi guys. i am working at a small scale mining industry. they have been operating at about 80t/h feed to ball mill. the cyclones operates at about 85MPa feed pressure. 2 cyclones run at a time. however they don't maintain water balance .we all know that the principle is "the less the feed the less the water, but proportionally and vice versa". but they keep saying if the water is less proportional to the feed, the cyclone feed pressure will go down, so will result in undesired classification. this is why they add same amount of water all the time whether the feed is less or more. but i suggest, what if we use one cyclone at a time, in case the feed to ball mill goes down from 80t/h to 30t/h. since they use almost same amount of water even though the feed to mill gets low to 30t/h, cyclone overflow becomes diluted and results in a very low density ( it was supposed to be 23%, but goes down to 10-11%), which becomes out of the designed parameter.in my point of view, with the correct water balance i get my cyclone overflow 23% all the time. but how about the cyclone feed pressure? i think we cant increase the pump speed to maintain the pressure, because tonnage to mill is low. The cyclone feed sump can be left empty. here is the help i need guys. Do I have other alternatives to get the designed cyclone pressure or any other ways by keeping cyclone overflow 23% all he time. thanks a lot