Innovative fabric filter design reduces costs and cuts emissions

December 15, 2014 lars gamborg

FLSmidth introduces two new DuoClean™ filters

FLSmidth has recently introduced two new, revolutionary DuoClean™ filter types – the DuoClean™ DC2 and the DuoClean™ DC8. Continuing FLSmidth’s objective of providing cost-efficient and effective filter solutions, the new DuoClean filters meet the strictest emission requirements, while reducing upfront costs. They feature an innovative octagonal shape and a compact, modular design. 

Lars Gamborg, FLSmidth’s Global Product Manager for Fabric Filters, explains that FLSmidth set out to design a fabric filter that performed exceptionally, but at a lower cost of investment. “Based on this vision, we developed a compact filter that is simple to manufacture, transport and assemble, while also delivering low operational costs, high performance and low emission. With the new, compact DuoClean filters, which are based on modules, we focused on manufacturability and constructability, and this enabled us to create filters that minimise environmental footprint to an even greater degree.”

Further development of proven technology
Already installed at more than 50 plants worldwide, the DuoClean filter has a proven design and technology concept. In creating the two new filters, FLSmidth has further developed the most important DuoClean features, including the cleaning system, gas distribution capabilities and the long-bag technology. A close look at supply chain and customer requirements revealed the need to reduce engineering, manufacturing and installation costs. To meet these needs, the new filters feature a standardised, modular design.

Advanced gas and dust distribution screen
DuoClean’s technology is characterised by a dual-flow gas approach. Gas flows from the bottom and side of the bags ensuring low, uniform velocity over the entire bag filtration area. This allows the use of longer bags, which reduces the filter footprint. 

To ensure gas is distributed evenly to the hoppers and on the bags, individually designed gas distribution screens are used for each filter application.

These 8 steps illustrate a Duoclean DC2 filter taking shape. Construction and installation can be as quick as just four weeks. The components arrive on-site in containers. You only need a crane for the final moving of the pre-installed components to the final filter location; otherwise all construction is done at ground level.

Lighter filters reduce investment costs
The DuoClean DC2 and DC8’s modular design features eight identical panels assembled in an octagon. The filter uses simple reinforcement profiles and requires fewer components. Its near-round shape has a self-reinforcing, strengthening effect, which, together with the optimised casing and hoppers, means it is significantly lighter than comparable fabric filters. This leads to lower capital expenditures (CAPEX) requirements, as lighter filters are easier and more cost-effective to fabricate, transport and assemble. 

Easy transportation and installation
The octagonal shape also plays an important role in simplifying transportation and installation. The filter’s steel components, transported in standardised containers, are designed so the casing, the eight side-panels and the hole-plate elements are a perfect fit to the container. The container is packed efficiently utilising the entire space, so fewer containers are required. This helps to minimise transportation costs.

The filter components are then typically assembled at a dedicated area close to the plant, and construction is completed onsite. This process reduces the demand for scaffolding and crane capacity and means construction takes place quickly, safely and cost-effectively. The use of standardised, prefabricated parts reduces the risk of errors and optimises quality assurance. 

Cleaning system increases bag lifetime
FLSmidth’s DuoClean filters ensure outstanding performance at a low operational cost. Thanks to the unique gas distribution and pre-separation of dust, the pulse jet cleaning system operates with a minimal number of cleaning cycles, resulting in low compressed air consumption, less wear of the bags and an increased bag lifetime. The low pressure cleaning system (cleaning pressure ≤ 2.0 bar), developed with extensive R&D, is also available to ensure efficient cleaning and reduced stress of the long bags. This means that the traditional high-pressure compressor (6-7 bar) can be replaced with a root blower, saving investment and operational costs.

Top access;Walk-in plenum;Weather enclosure

Smaller filters for smaller applications
FLSmidth’s DuoClean DC8 filter has been designed to meet the needs of smaller cement mill applications. Also featuring an octagonal-shaped casing, The DuoClean DC8 is a compact, one-compartment filter for use at a gas flow range of 45,000 to 150,000 Am3/h. With a small footprint and typical bag length of six to eight metres, it is up to 40 percent lighter than conventional filters. 

Significant R&D investments
The new filter types are the result of substantial R&D efforts by FLSmidth, in particular using computational fluid dynamics (CFD) to achieve optimal control of gas distribution and the ideal dualflow split. The CFD results demonstrated a well-distributed gas flow with a significant amount of dust being preseparated to the hopper. This delivers uniform gas speed to the bags, reduces compressed air usage and increases the lifetime of the bags, all factors that help reduce operating costs.

Lars Gamborg elaborates on FLSmidth’s R&D efforts: “We have invested extensively in R&D to ensure that a well-proven technology is transformed into innovative filter solutions responding to the needs of today’s plants and industry trends. The testing was carried out at our R&D Centre Dania, which is now the biggest in the industry. Besides testing many prototypes, the full-scale pilot filter allowed us to test the 10m long bags in different operating conditions.”

“As a technology leader, FLSmidth is committed to delivering excellent solutions for reducing emission levels now and in the future. It is definitely our objective to provide our customers with a future-safe investment.” - Lars Gamborg
Global Product Manager, Fabric Filters

The following plants testifies results at an actual emission of 1.24mg/Nm3 :

BMIC, Egypt
At the BMIC cement plant in Egypt, all emission targets have been met successfully with the DuoClean DC8 filter. With a bag length of six metres, the filter operates at a gas flow of 72,000 Am3/h and temperature of 140 °C.

Askale Cement, Gumushane, Turkey
AThe skale Gusmushane plant in Turkey selected the DuoClean DC2 filter for the plant’s cement mill due to the filter’s compact design and ability to handle large gas flows. With an emission guarantee of 10 mg/Nm3, the filter has a 10-metre bag and operates at a gas flow of 850,000 Am3/h and temperature of 95 °C.

CEMEX, APO, Philippines
At CEMEX APO in the Philippines, the DuoClean DC2 filter is installed on the plant’s cement mill. The eight-metre bag provides an emission guarantee of 15 mg/Nm3 at a gas flow of 780,000 Am3/h and temperature of 100 °C.

Lafarge Cement, Rezina, Moldova 
A nine-metre bag provides an emission guarantee of 10 mg/Nm3 on the kiln/raw mill at Lafarge, Rezina plant in Moldova. The filter operates at a gas flow of 630.000 Am3/h and temperature range of 100-250 °C. 

Read more about our Air pollution control solutions here>>

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