### Permission to use the attached copyrighted document provided to the U.S. EPA by email dated

November 3, 2009 from J. Sloesen, Weir Minerals Netherlands b.v., to Steve Souders, U.S. EPA.The fly ash disposal area: ready for soil covering. The problem: hardened slurry obstructing the

bladder. GEHO® Info for sales representatives

Volume 12, No. 2, March 2002



# Water barrier dampener

Sloped disposal

Elektrarna Ledvice (ELE), in the Czech Republic, deposits residue from coalcombustion and flue gas desulphurisation at a distance of 4,700 metres against the slopes of an open pit in amanner, which meets Czech environmental legislation. GEHO® PUMPS met the challenge todevelop a concept, design, build, commission, performance test and warrant the disposal system. It comprises the preparation, pumping, transportation,distribution and dry disposal of a hardening (from CaO reaction) slurry with entrained crushed slag in a rather humid and cold climate. A large section of the sloped disposal has been filled with a 20metres high stack as seen in the photograph. After it is covered with soil and vegetation, the landscape will be as it was before the mining of brown coal. The stack has proved to be so stablethat soil sealing is no longer a requirement. It did not take much more than an extension of the pipeline to prepare the adjacent area for disposal. 

### Solidification

GEHO® PUMPS designs guidelines forequipment and systems that handle selfhardening slurries, which require the avoidance of stagnant areas. The ELE pumps were fitted with a dampener with nitrogen precharged bladder to reduce the pressure variationat the discharge flange for flow and acceleration induced pressure disturbances.

We felt that the special shape of the housing and bladder and the resulting wedge action would keep the dampener clear of product. We were wrong, so we set out to resolve the problem. Solidified product formed scaling and

obstructed the free movement of the bladder, which failed prematurely.



### Water barrier

The operators had to remove the entire dampener weekly for descaling. Theremoval by chiselling of a four centimetre build up of compacted and stone-The solution: a spool pipe between manifold and dampener. hard slurry was labour intensive and not

easy. None of the GEHO® trials, such as a topdown mounting, which put the slurryinside the bladder, improved the situation. We considered the use of variousdampener models available on the market and especially the through-flow types. Not a single one was suitable and without unacceptable drawbacks.

A level controlled air vessel would have been the solution except that it was a costly retrofit. The problem was then resolved with the installation of a spoolpipe between the manifold and dampener. The intermittent injection of water now provides a continuous water barrier between the bladder and the live slurry.



### Empirical proof of concept

A commercial plunger (jet cleaning) type pump is used for the water flushing. Its flow rate is small and independent of the prevailing pipeline operating pressure. The fixed line shown served to sample the contamination of the water by slurry. With each flushing cycle, the clear water level is pushed down the spool.

It creates a fresh water buffer that gradually becomes contaminated due tomixture with slurry solids. When reaching a certain level of contamination, it is displaced into the pump manifold during the next flushing operation. The flushing interval time for pipeline start-up and operation were empirically determined. The water consumptionneeded for keeping the water-slurry mixture below the sample point and ultimately out of the dampener did effectively decrease the slurry solids concentration a negligible 0,06%.

The water barrier design did eliminate the need for descaling and resolved the bladder failure problem altogether. The dimensions of such a spool pipe will obviously vary with the dampener sizeand also with the pipeline pressure operating range. The development is one of the many experiences gained by GEHO® PUMPSfrom the supply of tailings disposal systems.

Weir Minerals Netherlands b.v. P.O. Box 249, NL-5900 AE Venlo Phone: +31(0)77-3895200 Fax: +31(0)77-3824844

Email: weir@weirminerals.com

Website: www.weirminerals.com

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