Pumps for Thickened Sludge / Slurry Service

If the pressure conditions allow, consider a diaphragm pump.

It would be useful to know flow and head.

You could consider a recessed impeller pump (vortex pump), perhaps a Discflo pump, or a slurry pump from the likes of Weir (Warman). A vertical cantilever might be a bit expensive, depending on pump size, and if duty permits a peristaltic could also be considered.

Approx. capacity and head of existing pumps:

Vertical pump - 10 m3/hr capacity and 12 m head (HTDS DAF)

Progressive cavity - 5 m3/hr capacity and 100 m head (thickened oily sludge)

For the first duty, as long as the pump isn't too long a vertical cantilever pump might not be too expensive. Also, Weir do a Warman vertical slurry pump. I'd stick with a centrif, if possible.

For the second duty I would avoid any type of centrif due to relatively low flow/high head and viscosity, which could result in high absorbed power. I would be inclined to consider either a peristaltic pump or a diaphragm pump. A lobe pump or rotary piston pump (Tuthill) could probably also do the job, but might be expensive.

For this capacity, diaphragm type sludge pumps are suitable and easily available. These are less expensive then many other options.

Straining a slurry--now ain't that an amusing roadblock?

Strain a slurry with a basket strainer 1/8" holes. Keeps the cats and dogs and lumps out but allows dispersed slurry through. Deflakers do this in paper industry by breaking the lumps down rather than straining them out - often used when recycling paper.

Dewatering and a conveyor belt?

• If you need to transfer all solids in the slurry---

Use the system followed for transferring Bottom Ash from Pulverized Coal Fired Boilers:

Automatically programmed Air Piston

• If you would rather leave the solids behind to be conveyed separately- use ElectroCoagulation. Rest is clear liquid to pump. .All problems solved.
  

we used a "sludge pump". it was portable and driven by a 5 hp engine. it was a diaphragm type and was able to pump oblects up to 3" in diameter.

we used a diaphagm pump that was able to pump objects up to 3". i don't remember what the head capacity was, but you could connect two or more in series if you required more head capacity.

Are you interested in dewatering the slurry so as to recover the solids as a thick sludge? Or is the slurry the way you want it, and you just need to move it as is, rocks and all?

For the former, consider this design. For the latter, a shearing centrifugal pump in the nature of a double disk mill would take an axial feed and extrude the slurry at the periphery of the counter-rotating disks. With a peripheral drive wheel for counter-rotating the disks, you get a lot of torque for advecting the sludge.

Suggest to ask any Steel Mill Producer !!-it is dealing with sludge from steel scale...

Vishal, I was a pump sales engineer in the Houston market for almost 20 years. I have pumped everything that will fit through a pipe and I repped ALL types of pumps (many brands and technologies including both positive displacement and centrifugal) so I am not prejudiced in my selection. Without knowing your specific operating conditions, a PC pump is probably your best selection. Since your viscosity is only at 250 cp, I doubt that upgrading to a piston pump (i.e. Putzmeister or Schwing at roughly $100K) would be worth the expenditure. I would suggest getting with your PC mfgr and reviewing the operating conditions first. Slowing the pump down, adding stages, oversizing or undersizing the rotor, and changing the elastomer material are all options to be considered for maximizing your pump's stator life. If you don't know who to contact, I would suggest contacting Moyno, Netzsch, or Seepex via their websites. They have always seemd to be the most technically competent to me.

At Martin Marietta Magnesia Specialties we produce high-solids (60%) slurry containing abrasive particles at pH 9-10. We have had very good experience with peristaultic pumps for relatively low flow rates at <100 psi discharge pressure, and especially if there is a possibility for the suction to be empty while the pump is operating. Not all peristaultic pumps are created equal.

Progressive cavity pumps work well for those applications with higher flow rates if the suction is never restricted, since running empty would damage the stator. These can develop higher discharge pressure than peristaultic pumps. Good for continuous circulation of thick or abrasive slurries.

Air Diaphragm pumps are ideal for start-stop transfer operations. Although the checkvalves may wear due to abrasive materials, this can be overcome by preventive maintenance. We recommend these pumps for receiving/unloading since they can run until the load is transferred to storage and not damaged by running empty when the transfer is done. Flush in between uses. Best if the air supply is "dry" and an exhaust silencer is used.

Centrifugal pumps have their place but select seals and impellers with care to prevent wear when pumping abrasive slurry. This option is usually associated with higher cost.

Our stable Magnesium Hydroxide slurry is "milk of magnesia" and is a high-solids non-neutonian fluid. Caution - all slurries contain particles that may settle over time, and some resist settling and are easier to pump than others. Martin Marietta Magnesia Specialties magnesium hydroxide slurry generally does not thicken or thin out as shear increases, but initially resists starting to flow. That puts it in a "pseudoplastic" flow category at delivered solids.

Thanks to you all for suggesting different options. Looking at these, I infer that the existing progressive cavity pump in sludge service may be modified and the strainer in its suction be removed so as to prevent empty running.

If possible please suggest a reasonable stator material. The present one is having nitrile rubber as stator material.

High density polyethylene (HDPE) is very abrasion resistant.

You may want to look at Penn Valley Pump. PD pump that can run dry, good with solids/slurries.