High Pressure/Flow Acidic Slurry 2

[JRLAKE]

I need to pump a 3.5% sulfuric acid / 20% wood pulp slurry. Flow needs to be variable from 1 GPM to 800 GPM and will be injected into a reactor at 400 PSI. Temperature of the slurry is 140 degrees F.

We are currently using a Seepex progressive cavity pump for 1 GPM injection but we need to increase flow and I have concerns about the reliability of these types of pumps.

Anyone have any suggestions?

 

[Artisi]

A bit away from your question at this point, but how are you getting 20% wood pulp slurry to flow into the pump?

Are you currently pumping this 20% slurry at 400PSI?

 

[moltenmetal]

I guess you are beginning to appreciate why it's tough to build cellulosic ethanol plants!

There are patented and proprietary/trade secret devices to do this job. And they're not simple progressive cavity pumps...

Why are you mixing the acid with the pulp before feeding it?

 

[JRLAKE]

Hit the nail on the head moltenmetal and I can't answer that question.

Artisi, we used a progressive cavity pump with a suction feed hopper, bridge breaker and screw conveyor to force the pumpage into the suction.

 

[JRLAKE]

...and yes Artisi, we are injected @ 400 PSI @ 1 GPM. Sorry forgot to answer that part.

 

[nickelkid]

Have you had any problems with the small pump you are using now?

Are you planning on using 1 pump or multiple for the 800 gpm?

 

[JRLAKE]

Yes there have been problems. The stator has not held up well for a variety of reasons (pressure,temperature,chemical) I am worried with the added flow (and therefore speed), reliability will be an issue. Also, teflon stators for pumps this size are high dollar items.

We are pretty sure it will have to be a multipump system due to the turndown.

 

[moltenmetal]

Yes, you SHOULD be concerned with the reliability of these pumps...

Explain what you mean by "the flow has to be variable between 1 and 800 gpm". If you mean "the same single pump has to be capable of discharging this stuff at 1 gpm or 800 gpm", you're tilting at windmills. That's an unrealistic expectation of turn-down capacity for a water pump, much less one pumping pulp.

 

[JRLAKE]

Correct molten. I have accepted the fact that it will have to be a multipump system. But not knowing all the options out there that are available, I stop short declaring it a fact. PD pumps have impressive turndown capability, but like you said, it's highly unlikely.

Initially I was thinking of a four or five pump system, with an additional "jockey pump". However this brings me back to my original question, is there a better way to do it than with a pc pump? Multiple 100-200 GPM pc pumps with teflon stators is not my ideal installation.

 

[moltenmetal]

IDEAL PD pumps have infinite turn-down. Real ones have turndown limits due to back leakage and other real concerns, like how slow you can spin an electric motor at constant torque without it overheating, etc.

Real PD pumps are limited to about 10-20:1 on speed and about 10:1 on stroke, even when pumping clean fluids. Your progressive cavity unit has no stroke control, hence its practical turn-down limit is about 10-20:1 on speed- even if back-leakage isn't an issue.

And it will be...especially if teflon is your only stator option.

You need to get real about your capacity range. Realistically you're not talking about five pumps: even at 100:1, you're looking at eight pumps...

As to alternatives to your Seepex unit, aside from calling one of the people who have (apparently) already patented feeders for this purpose, unfortunately I'm short on suggestions! I have absolutely no idea how well (or poorly, or how long) these units work. But you're right to ask, as it never hurts.

With respect, I suggest you may be thinking about this the wrong way: you're thinking this is a pump selection exercise when it's really a process development exercise. I do wish you the best of luck with it.

 

[JRLAKE]

I agree with you completely about the process development exercise comment. The feedback I am getting is sending us down that road. We are merely entertaining the idea described above. Seems foolish to not consider all possibilities during the design stage. Wouldn't you agree? I mean it's federal money we're dealing with (consider that a "partial", yet I agree, very poor, joke).

To be honest I haven't run through the numbers on the number of pumps in the multipump system. It's a non issue. We can add as many as needed. I am more concerned about the pump design at this point.

And the people that have patented this type of pump that I should contact, I guess that completely answers my original question (almost!). Thanks to you I now know they exist. On to the next step, who are these people and how do I contact them?

 

[moltenmetal]

I'll give you a hint: they're cellulose ethanol companies, NOT pump companies. So I doubt they'll be too interested in selling you a pump!

 

[JRLAKE]

Bologna. Companies license their technologies to each other all the time. But thanks for the hint. That answers my question.

 

[Artisi]

JRLAKE
A couple of hots in the dark for you to consider - concrete placement pump - well drillers mud pump.

 

[JRLAKE]

Those are great suggestions Artisi, thank you. That's why I come here, for the outside the box thinking.

I was also thinking about contacting some oil & gas gurus.

 

[HEC]

Netzsch pumps may be another alternative, we are currently considering one of their PCP's for an acidic mineral slurry at 72%ww.


Mark Hutton

 

[moltenmetal]

JRLAKE: you're absolutely right- there may be someone who will license their feeder technology to you for a fee- that's what I was implying. But that will of course involve a license fee, not simply the cost of the "pumps" themselves. It will also come with the benefit of all the experimental/trial and error work having been done for you already- or at least most of it. Which begs the question: if you're going to license the feeder, why not license the digester as well?

I'm not in that business, but either

http://www.sunopta.com/bioprocess/index.aspx

or

http://www.iogen.ca/

might be worth a try.

Again, best of luck to you.

 

[JRLAKE]

Molten, thanks for the advice.

I just realized that I misled you earlier. This is not a cellulostic ethanol application. The nail on the head comment referred to the "There are patented and proprietary/trade secret devices to do this job. And they're not simple progressive cavity pumps...", as in, that is exactly what I am looking for.

What we are trying to do, referring to the process, has never been done before. I was hoping however, that the pump application, or something similar to it, had been done before.

 

[moltenmetal]

Cool- now I understand much better!

It'd be a tough job to make a concrete pump suitable for dilute acid at 140 F. But that might be a good option. 800 gpm's a fairly large flow, though, and against 400 psig- you're doing a LOT of mechanical work. Is energy efficiency a secondary consideration at this point?

Can you feed the pulp separately from the dilute acid using a lock-hopper arrangement, then mix them under pressure?

 

[Compositepro]

Check-out twin screw pumps. Warren Pumps has a video of their pump pumping 20% pulp. They only claim 200 psi, however.

http://www.warrenpump.com/industrial/pulp&paper.htm