Dear Mr. Teus,

Before Anything, thank you for your reply!

Let me explain a little the system i have in mind. This equipment, basically will aspire the grains to a truck. In this truck will be another system which will analysed the grains, and in another stage, the grain will be poached in sealed bags.

Obviously, this will be for a project, so, probably will be a gap between the technical requirements in the project with a reality scenario.

In a firs place, we analysed the possibility of put a small bag filter before de blower (i´m working like designer in a company specialized on dust and emission control, so it would have been practical) But our professor made us to change it because on an economic study that we made, and talking with people who had the grain conveyor, we noticed that the duration of the blower were about one and a half year minimum, so the operation and maintenance cost will we acceptable for the total cost of the machine, that grown the total cost putting a filter bag with a pneumatic cleaning system (we don't have compressed air either).

The first cyclone discharge is on a rotary valve that I selected for a rotation speed of 25 RPM, and the second cyclone on a deposit only for dust. I read something about in the outlet pipes both cyclones have a like a filter cloth, but I will ignore that for now

This i hope clarify a little the system, and why i will use the two cyclons even when is not the best option. Is because of this that I need to define this cylone (or grain separator)

You asked me about the pressure on the cyclones, i estimated 8" of water column. I have to tell you that all my calculations were very very approximated. At this stage i need to define the system, and later in another stage of detailed engineering I should make the final calculations and probably change some parts. But i tried to estimated in a conservative way. I also saw that similar equipments have approx the same flow and pressure, so I kept going with the other parts. I clarify this for you to know that probably, in my ignorance, I will say a lot of incorrect things.

Going back to the first cyclone again, you said that i need to define the measures of the cyclones, estimating and slow air speed, for example 10 or 8 m/s, so the grain going down?

And in this case, the physics of the cyclone continued compliance? The double vortex, etc.

Or i should to analyse it like another thing completely different, like a simple basel or something like that?

In other hand, i ask in advance. If i have to design this cyclone by the same laws, the ways it would be, with the inner speed, I define the inlet section, with this, the exterior diameter, and with that, the rest of the cyclone. Now, I need to adjust the cone part, right? I need to put a cone with an angle between 30-45 degrees? Doing this, I will have a shorter cyclone.

This i'll be a correct procedure?

I saw, for this grain capacity, in some comercial grain conveyor, that the cyclone has a diameter of 18" and a total hight of 36"

Thank you for your time!

Best regards, Emiliano ■

Mr Tuinenburg,

Exactly! that's the equipment which I saw before, and which looked the measurements of the cyclone of 18"x 36". And then I did get doubts about the size

But I will take your advise on the cyclone size for the 20Tn/h and 850 m3/h air flow. Thank you!

And I´ll insist with my professor about the filter, if he doesnt desist, probably i have to make a secondary cyclone with more efficiency. At least Im sure now that if sometime I have to build something like this, I need the filter.

Im going to investigate more about the vortex finder to made ir smaller, standard sizes, etc, and about some theoric data about the separator to justify that in the paper. But at least now I know how to face the problem to keep on going.

Thank you again Mr Teus.

Have a nice Sunday

Emiliano ■

Dear Mr Tuinenburg,

Sorry to bother you again, but I have a doubt about the calculation you did before, but first of all, let me put some light on what I did at the first place

Indeed, I thought in the first place to make a system like that, with the blower for suction and discharge. To define the blower, approximately, I made the calculation for the 20 tons/hour of capacity, for a total distance of 10 meter, and a pressure lost of 8" of water column on the cyclone. But with that distance, i tried to include the entire trail. The part of aspiration and the discharging.

For that I assume the total presure need of 450 mbar with a flow of 850 m3/h, with a product/air ratio of 27.

Now, I´m quite lost with the calculation you made to get the flow of 425 m3/h. Unfortunately I could not understand why you used those values. I thought i could have 850 m3/h with that blower.

About the system balance, yes, It's probably more complex than I can analyze.

Not only I dont have a clear idea about the equilibrium of the system with the distance (I try to think about it like an unstable equilibrium). Because the system probably will take the grain with a hose which could be in differents positions. But also, would be differents grains, with different densities, granulometries, and shapes.

Investigating a little the existing equipments, I saw that they have in the suction nozzle, a false air inlet which can be regulated by the user while is using the equipment.

Could this be for the system regulation that we are talking? I mean, that can be open by the operator, for sacrifice a little flow capacity to get the correct pressure, and equilibrate the vacuum pressure with the blowing pressure.

As you can see, more I try to analyze this problem, the more questions I have

Thank you for the patience.

Regards, Emiliano ■

Dear Mr Tuinenburg,

Thank you very much for clarify all this trouble. I see where I was mistaken. I didn't thought there was so much difference considering the difference in the density of the gas. I think I got now all the picture about the problem.

With the same positive and negative differential pressure (+/- half of the total catalog pressure) I have the total pressure before and after the blower (vacuum and blowing) then I take the same mass flow, and calculate both airflows, and with that and my suspension velocity, the pipelines diameter. Also, that negative pressure that i will have, it has to be enough to beat the transport itself and the pressure drop in the cyclones. So, in order, I need to design a first system from the capture nozzle until the rotary valve, and with the resultant mass flow like condition, and the same differential pressure (but positive) I have to find the way to blow the grain to the other side.

I will make all the calculations for the new air flow, and probably i going to need to change the solid loading ratio, and also with the new air flow or something I thought had defined.

Again, thank you very much for the classes Mr Tuinenburg

Well, now I think I have no excuses to dont put myself to work.

Reggards, Emiliano.

PS: I will keep on insisting to my profesor about the filter ■

Dear Mr Teus,

First of all, sorry to answer so late. I finished the pre-project in part, because of your help, but then I had to suspend for a while this part of the project to face the rest of it. Plus some exams. Now, I just started the detailed engineering, so I had to write some theoretical principles of all the system to define it, calculation method, etc. Everything is OK so far, but some things are strange to me, so i would like to share with you what I did

First, I tried to find the correct SLR and air velocity for some grains, but I couldn't. So I made an approximation based in the performance, used blowers, power, and pipes of another equipments like this, like the Walinga or Kongskilde, and other installations for grain conveyor that work only with negative or positive pressure. So what I had, in a very approximate way, was this:

Air Speed: 27 m/s.

Relation product/air: 25 kg/m3

Capacity 20 tons/h

I´m not really sure if this is correct, and maybe was a little obsessed with have the correct parameters, but we had to take it like a correct values to keep going with our work. After all, it's a project for the university and we won´t to build them

With this, I guessed, I only needed a justified calculation method (at this point I only made some approximate numbers)

So then, I did some research about how to make a correct calculation of the system, but I found that more theoretical is the method, more difficult is to set some parameters, because I need to transport different kind of grains, in different situations. Also I will have the possibility of regulate the airflow with some false air.

Also, I couldn't find a method which is considered THE method, or at least the way to design this kind of combined conveyor system generally.

Said that, I could find a very very empirical and simplified method that gave me what it looks logical values.

I suspect quite how to calculate this, but several coworkers have used for very simple things, and those seemingly run.

This was from an old technical bulletin from Mikro from ´77.

I dont want to bother you with all this thing of the calculations, I just want to share this with you than maybe you can tell me how wrong are the results and am I

In this method, with the air flow, air speed and naturally the diameter, One have to calculate the dynamic pressure (Hd).

Then, the pressure loss in the system is the sum of a series of losses that describes how to calculate.

- The loss because of the entrance of the material (0,75xHd)

- Acceleration losses (2,25xRwxHD). Here Rw is the SLR in kg/kg

- Losses in strait pipes (here use the linear meters of pipes and some factors of friction of the air and the mix material/air. those came from an abacus)

- Losses in the elbows

- Other losses (filters, etc)

So I made the calculations considering the relations speeds, etc that I said before

I considered an inner pipe diameter of 102mm, for the longitudes from the entrance to the grain separator (vacuum system) 2 meters of high and 5 meters in horizontal, then, after blower (pressure system) 5 meters horizontal and 5 meters in high. 2 elbows in both sides

So, with this, I get an air flow of 800 m3/h. For the pressure losses, to the vacuum system, I considered all the pressure losses I told before, and 200 mm of water for the losses in the cyclone and the grain separator.

For the pressure system, I do it considered losses of the entrance of materials and nether losses due acceleration. Here I have doubts. I do not considered that because It seems that the air was accelerated before, in the entrance, so, at the exit of the blower I don´t need to accelerate that again, also, if I do that, the pressure drops is 50% higher than any other existent similar equipment. But also, the truth is that the grain after the rotary valve will be still

However, I keep going with that and I get this.

For the vacuum system i have a pressure drop of 3244 kg/cm2 (with the extra 200 mm)

For the pressure side 1178 kg/cm2

Total pressure drop 4322 kg/cm2

I also tried to calculate the conditions in some points of future interest:

The air mass flow of air was 960 kg/h

- In the entrance: volumetric flow 800 m3/min, pressure 1 at, air speed 27 m/s

-in the entrance of the grain separator: volumetric flow 1145 m3/min, pressure 0,696 at, air speed 39 m/s

-entrance of the blower: volumetric flow 1178 m3/min, pressure 0,676 at, air speed 25 m/s, but here I estimated to put a pipe with an inner diameter of 128 mm approx

-exit of the blower: volumetric flow 712,9 m3/min, pressure 1,117 at, air speed 24 m/s

So far, the calculations I just made of the system.

I don't know if i'm uncomfortable because I don't trust in the method or what but I feel like something is wrong.

I tried to compare my results with for example the Walinga equipment for the same capacity, and based on the blower, pipes diameters, etc, it has the same potency, and it seems to be very similar.

I don´t know, maybe because the distances are short the error is like dilute in the margins o safe or something like that.

Maybe you can see the problem here.

Anyway, now I am designing the grain separator and the cyclone. For cyclone, I will take the geometrical relations for the air flow calculated before, and for the grain separator I will take the suggestion you made me before for the size. I guess the thing is to get an air speed slower than the suspension air speed for the grains, right?

To make this, I will simulate with a CFM program and get the air speed and the capacity of separation

That done, probably the rest is simple mechanical stuff to do.

Thats all I have for now.

Regards, Emiliano ■

Dear Mr Teus,

First of all, sorry to answer so late. I finished the pre-project in part, because of your help, but then I had to suspend for a while this part of the project to face the rest of it. Plus some exams. Now, I just started the detailed engineering, so I had to write some theoretical principles of all the system to define it, calculation method, etc. Everything is OK so far, but some things are strange to me, so i would like to share with you what I did

First, I tried to find the correct SLR and air velocity for some grains, but I couldn't. So I made an approximation based in the performance, used blowers, power, and pipes of another equipments like this, like the Walinga or Kongskilde, and other installations for grain conveyor that work only with negative or positive pressure. So what I had, in a very approximate way, was this:

Air Speed: 27 m/s.

Relation product/air: 25 kg/m3

Capacity 20 tons/h

I´m not really sure if this is correct, and maybe was a little obsessed with have the correct parameters, but we had to take it like a correct values to keep going with our work. After all, it's a project for the university and we won´t to build them

With this, I guessed, I only needed a justified calculation method (at this point I only made some approximate numbers)

So then, I did some research about how to make a correct calculation of the system, but I found that more theoretical is the method, more difficult is to set some parameters, because I need to transport different kind of grains, in different situations. Also I will have the possibility of regulate the airflow with some false air.

Also, I couldn't find a method which is considered THE method, or at least the way to design this kind of combined conveyor system generally.

Said that, I could find a very very empirical and simplified method that gave me what it looks logical values.

I suspect quite how to calculate this, but several coworkers have used for very simple things, and those seemingly run.

This was from an old technical bulletin from Mikro from ´77.

I dont want to bother you with all this thing of the calculations, I just want to share this with you than maybe you can tell me how wrong are the results and am I

In this method, with the air flow, air speed and naturally the diameter, One have to calculate the dynamic pressure (Hd).

Then, the pressure loss in the system is the sum of a series of losses that describes how to calculate.

- The loss because of the entrance of the material (0,75xHd)

- Acceleration losses (2,25xRwxHD). Here Rw is the SLR in kg/kg

- Losses in strait pipes (here use the linear meters of pipes and some factors of friction of the air and the mix material/air. those came from an abacus)

- Losses in the elbows

- Other losses (filters, etc)

So I made the calculations considering the relations speeds, etc that I said before

I considered an inner pipe diameter of 102mm, for the longitudes from the entrance to the grain separator (vacuum system) 2 meters of high and 5 meters in horizontal, then, after blower (pressure system) 5 meters horizontal and 5 meters in high. 2 elbows in both sides

So, with this, I get an air flow of 800 m3/h. For the pressure losses, to the vacuum system, I considered all the pressure losses I told before, and 200 mm of water for the losses in the cyclone and the grain separator.

For the pressure system, I do it considered losses of the entrance of materials and nether losses due acceleration. Here I have doubts. I do not considered that because It seems that the air was accelerated before, in the entrance, so, at the exit of the blower I don´t need to accelerate that again, also, if I do that, the pressure drops is 50% higher than any other existent similar equipment. But also, the truth is that the grain after the rotary valve will be still

However, I keep going with that and I get this.

For the vacuum system i have a pressure drop of 3244 kg/cm2 (with the extra 200 mm)

For the pressure side 1178 kg/cm2

Total pressure drop 4322 kg/cm2

I also tried to calculate the conditions in some points of future interest:

The air mass flow of air was 960 kg/h

- In the entrance: volumetric flow 800 m3/min, pressure 1 at, air speed 27 m/s

-in the entrance of the grain separator: volumetric flow 1145 m3/min, pressure 0,696 at, air speed 39 m/s

-entrance of the blower: volumetric flow 1178 m3/min, pressure 0,676 at, air speed 25 m/s, but here I estimated to put a pipe with an inner diameter of 128 mm approx

-exit of the blower: volumetric flow 712,9 m3/min, pressure 1,117 at, air speed 24 m/s

So far, the calculations I just made of the system.

I don't know if i'm uncomfortable because I don't trust in the method or what but I feel like something is wrong.

I tried to compare my results with for example the Walinga equipment for the same capacity, and based on the blower, pipes diameters, etc, it has the same potency, and it seems to be very similar.

I don´t know, maybe because the distances are short the error is like dilute in the margins o safe or something like that.

Maybe you can see the problem here.

Anyway, now I am designing the grain separator and the cyclone. For cyclone, I will take the geometrical relations for the air flow calculated before, and for the grain separator I will take the suggestion you made me before for the size. I guess the thing is to get an air speed slower than the suspension air speed for the grains, right?

To make this, I will simulate with a CFM program and get the air speed and the capacity of separation

That done, probably the rest is simple mechanical stuff to do.

Thats all I have for now.

Regards, Emiliano ■

Dear Mr. Teus

Sorry for my re post, I dont know how I sent it two times. Sometimes it takes a while to update. But now I cant erase the duplicated thread

If it's not much trouble, I prefer to send you that information by mail.

I can take the opportunity to send you some schemes I did.

Once again, thank you so much for your help.

Regards, Emiliano ■