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Notes from Meeting with GEA EGI Contracting/Engineering Co., Ltd.

March 31, 2014

On Monday, March 31, 2014, EPA and ERG participated in a meeting with GEA EGI 

Contracting/Engineering Co., Ltd. (GEA EGI) at EPA Headquarters in Washington, D.C. to discuss GEA 

EGI’s Circumix® Dense Slurry System (DSS) technology. Participants in the meeting included 

representatives from EPA, ERG, and GEA EGI, as listed in Table 1.

Table 1. List of Participants

Name Organization

Istvàn Kovacsics GEA EGI

Ron Jordan EPA

Phillip Flanders EPA

Jezebele Alicea EPA

Deb Bartram ERG (contractor to EPA)

Elizabeth Gentile ERG (contractor to EPA)

Mr. Kovacsics visited EPA to give a presentation on their DSS ash handling technology. The 

presentation, company brochures, and other supporting documents provided by Mr. Kovacsics following 

the meeting are included as attachments to these notes and listed in Table 2 below. Mr. Kovacsics also 

provided copies of the public comments submitted on this rule and the CCR rule (EPA-HQ-RCRA-2013-

0209), which are available in the dockets.

Table 2. List of Attachments

DCN Title

SE05936A1 GEA Circumix® Dense Slurry Technology Brochure

SE05936A2 NAES Circumix® Dense Slurry System (DSS) for Ash and Waste Water Management 

and How it Addresses Proposed ELG and CCR Rule Change

SE05936A3 NAES Corporation DSS Presentation

SE05936A4 NAES Statement of Qualifications

SE05936A5 NAES Corporation Brochure

SE05936A6 Year Two Follow-Up Investigation Report: Soil and Water Quality Evaluation St. 

Mary’s Shoals Park Roadway Improvements

SE05936A7 GEA EGI DSS Technology Photos

Mr. Kovacsics started with an introduction of the DSS technology, stating that mixing water with 

fly ash will result in a product that hardens up naturally (due to the compounds and mineral structures 

that are formed). However, this reaction requires calcium oxide and optimal operating conditions 

including the quantity of water, particles size of the ash, and chemical composition. For each 

installation, GEA EGI evaluates a diverse set of inputs to determine if the DSS technology is an applicable 

ash handling technology for a specific plant. GEA EGI has been experiencing a high level of interest in the 

system from the industry.
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The system is designed for coal- or petroleum coke-fired generating units; however, it is not an 

available technology for oil-fired generating units (mainly due to the small amount of ash generated). 

Mr. Kovacsics stated that pulverized coal boilers are preferred for the DSS technology because of the 

high temperature and low concentration of potassium oxides. Fly ash and bottom ash from circulating 

fluidized bed boilers are also good candidates for the system because plants often add lime to the 

fluidized bed, resulting in high calcium oxide content, and the bottom ash is very reactive (like the JEA 

Northside (Jacksonville, FL) installation).

In order for the system to function efficiently, it is important to identify the optimal level of 

water. If the slurry is too thick, pumping costs can be too high. If the slurry is too thin, large particles can 

settle in the pipelines and won’t be carried to the final destination. The solids to water ratio in a 

traditional wet sluicing system ranges from 1:10 to 1:15. In a DSS, the solids to water ratio is 1:1. 

Typically, fly ash is only considered in the calculations for the design of the DSS. Bottom ash is 

usually too big to affect the viscosity of the slurry. When designing the system, GEA EGI focuses on the 

extremes of different fuel types or coal blends that are used at the plant to calculate the solids to water 

ratio for the slurry. The plant can make adjustments to this ratio when mixing the slurry if necessary. 

Typically, a plant does not need to adjust the solids to water ratio day to day unless a very different type 

of coal is being burned.

The mixer developed for the system makes the mixing of the dense slurry more efficient. 

Previously, the design called for a pugmill; however, this resulted in high maintenance costs because 

components of the pugmill were eroding. It also resulted in poor mixing and dead zones that could not 

be reached by the pugmill pedals. The mixer results in a homogenous mixture. 

Mr. Jordan asked if bottom ash that is currently wet sluiced could be transported by the DSS. 

Mr. Kovacsics stated that because bottom ash is inert, it must be kept in suspension. He stated that 

unlike bottom ash, gypsum helps with the viscosity of the dense slurry because it is a fine powder. In 

order to transport bottom ash, the particle size must first be reduced prior to mixing with the slurry. Mr. 

Kovacsics reiterated that all of these systems are custom built. Additionally, he stated that some systems 

are designed to service all generating units at the plant and some are designed to have one mixer per 

generating unit.

In order to pump the slurry to the final destination, GEA EGI prefers to use centrifugal pumps or 

piston diaphragm pumps (PDP) because they require less maintenance. Mr. Kovacsics stated that the 

maximum conveying distance for the DSS ranges from 15 to 20 kilometers, although that distance can 

be influenced by elevation differences. 

Mr. Kovacsics explained that in the conversion of a traditional fly ash wet sluicing system to a 

DSS, the plant can install any type of dry fly ash handling system and that some silos can be utilized in 

the DSS. In addition, the plant will need to install mixers, pumps, and piping to the landfill. Mr. Kovacsics 
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stated that these systems can range from anywhere to $5 million to $60 million dollars, excluding the 

costs of the landfill.

The main maintenance associated with the system is the pumps; however, they are easy to 

replace. If the pumps are running 24 hours, they need to be replaced every [PLACEHOLDER] years. 

Additionally, an operator must inspect the length of pipe at least once a day for any leaks. Normally, the 

system is designed with a high level of redundancy. For example, there is typically a dedicated mixer per 

boiler and 2 pumps are included per train/pipeline for each mixer. Within the system, each mixer is 

connected to a dedicated pump site, including crossover valves. Therefore, any mixer can supply slurry 

to any pipeline in the system.

The silos for the system are designed for 8-24 hours of capacity. Mr. Kovacsics stated that this is 

enough capacity because any maintenance issue should be able to be resolved within 8 hours provided 

the plant has the parts required for the maintenance. 

Makeup water for the system is required; however, it can come from other wastewaters at the 

plant (e.g., bottom ash transport water). Plants can also use FGD wastewater; GEA EGI does not expect 

chlorides in the FGD wastewater to be an issue in the system. GEA EGI confirmed that there is one plant 

in Romania using FGD wastewater as makeup water for the DSS. Flushing water is also required when 

the system is stopped to flush the slurry pipelines, preventing solidification of the slurry. 

The resulting ash by-product is a solid that dries in the landfill. The by-product is solid; however, 

if dropped it will break. The ash by-product does not generate any dust. The cure time for the byproduct is associated with the hydraulic conductivity of the slurry. The resulting by-product would not 

typically be marketed.

At the disposal site, plants typically scrape the surface into cells. Using this approach, plants can 

sluice the dense slurry into one cell, let another cell dry, and work on the remaining surface of the 

disposal site. Because of the composition of the material, the landfill can be built vertically in tiers. Mr. 

Kovacsics stated that water does not need to be added to the landfill to scrape or spread the ash byproduct. Two operators are required at the landfill to prepare cells and move the slurry pipelines. 

The slurry is a 1:1 ash-water mixture. Approximately 5 to 10 percent of the water is excess water 

that becomes a thin film on top of the ash by-product at the landfill. This water either evaporates or 

slowly seeps and is collected by a leachate collection system. This water and any precipitation that is 

captured is either sent back to the system or discharged. GEA EGI confirmed that any leachate 

associated with the system that can be collected and reused as makeup water to achieve zero discharge.

The dikes built around the landfill are typically 3 meters tall and are typically built using ash by-product. 

Mr. Kovacsics stated that there aren’t any run-on issues and that there can be excess water from 

precipitation. 

Commented [E1]: Note to GEA EGI: Can you provide the this 

maintenance information on the system pumps?
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The DSS may not be ideal in geographic locations that have cold climates (10-15 ̊F) for extended 

periods of time (e.g., Russia). If the slurry freezes it will not harden and set. However, this process is an 

exothermic reaction; therefore, it may be OK in locations that have short periods of freezing weather. 

Plants could also put slurry pumps underground to avoid the freezing of flush water or install trace 

heating.