Flue Gas Cleaning

Keppel Seghers DRY SCRUBBER | Keppel Seghers ROTARY ATOMISER
Keppel Seghers DEDINOX | Keppel Seghers CATFILTER

Applications
Dry scrubbing for removal of acid components, metals and dioxins from flue gases

Advantages

• Recirculation eliminates pollutant spikes and excursions at the exhaust stack
• No wall build-up, nozzle clogging or wear
• Low energy consumption with high availability and reliability
• Ease of operation and minimal maintenance cost.
• Maximal energy recovery due to operation at low temperature
• Minimal investment cost

Description
In the vertical venturi reactor the flue gases are homogeneously mixed with the hydrated lime and activated carbon as well as the recirculated product from the fabric filter.

This homogeneous mixture of reagents and flue gases is maintained throughout their passage through the reactor, which ensures a pre-determined reagent/gas contact time is achieved providing very high scrubbing effiencies.

The high volume of recirculated product provides an excellent buffer against variations in pollutant inlet levels ensuring constant compliance.

Applications
Semi-wet scrubbing for removal of acid components, metals and dioxins from flue gases.

Advantages
The integrated design of the semi-wet reactor and the Keppel Seghers ROTARY ATOMISER assures:

• optimum conditions for the neutralisation reactions
• a homogenous distribution of flue gases throughout the reactor
• intense mixing of the flue gases with fine homogeneously atomised liquid
• sufficient residence time in order to attain a dry reaction product
• cooling of the flue gases (water evaporation) to a temperature at which reactions are most effective
• drying out of the reaction products
• zero water discharge.

The Keppel Seghers ROTARY ATOMISER is characterized by

• a compact system
• optimal reactor design by CFD analysis
• droplet size being independent of the discharge to be atomised
• finer droplets compared to conventional atomisers
• homogenous and stable atomisation
• low lime consumption
• reduced risk of 'caking', which in turn means higher operational reliability and a reduced need for maintenance
• lower electricity consumption than compressed air atomisation.

Description
The Keppel Seghers ROTARY ATOMISER is a very compact and easy system to manipulate (maximum external diameter = 380mm, overall height less than 1m). The system has an open disk incorporating open chambers (analogous to pump wheel). The danger of lime caking is therefore considerably reduced and the open disk lends itself to easy maintenance.

The Keppel Seghers ROTARY ATOMISER is equipped with a double distributor. That way, the additional water is injected separately into the reactor, avoiding problems of blocking caused by the formation of CaCO3 in the piping.

The Keppel Seghers ROTARY ATOMISER is equipped with a simple and direct drive (no gearbox). The motor is located centrally on the axle of the system. The short axle and the symmetrical and compact composition ensure that the bearings are less susceptible to "bending" and radial forces, and the vibration and noise levels are also reduced as a result of this.

The Keppel Seghers ROTARY ATOMISER is fitted with quick-release couplings. Likewise there is also a tackle and transport container so that the rotating atomiser can be exchanged for the spare atomiser within a maximum time limit of 15 minutes.

Applications
SCR installation for catalytic removal of dioxins and nitrogen oxides (NOx) in flue gases.

Advantages

• pollutants (dioxins and NOx) are destroyed and not relocated or captured
• destruction of dioxins to extremely low levels (0.02-0.001 ngTEQ/Nm³)
• high degree of operational safety since risk of formation of "hot spots" on the catalyst is minimal
• no disposal of dioxin-laden solids, no additional CO and dust emissions
• minimum expenditure for operator control and maintenance
• variable integration into existing flue gas cleaning systems possible

Description
The Keppel Seghers DEDINOX is a unique concept that allows for the reduction of nitrogen oxides and simultaneously, the destruction of dioxins/furans. The concept is based on the proven SCR technology.
This type of flue gas cleaning, in which the pollutants are not only captured, but actually destroyed, is currently considered the best available technology (BAT).

The technology can be applied to a new flue gas cleaning installation or an existing installation. Before entering the Keppel Seghers DEDINOX the flue gas has to be heated to a working temperature, somewhere between 150 and 300°C. At the entrance of the reactor a NH3-solution is injected in order to create reducing conditions for nitrogen oxides and achieve a good reaction velocity. At the same time the dioxins and furans are destroyed using the available oxygen in the flue gas passing over the catalyst material.

The Keppel Seghers DEDINOX consist of following components:

• reheating unit, heat exchanger and in-line duct burner (natural gas);
• NH3-injection system;
• reactor with catalyst;
• process control module.

Flow range: 5 000 - 300 000 Nm3/h.

Applications
Flue gas cleaning with catalytic dioxin removal

Advantages
The Keppel Seghers CATFILTER is the only integrated solution solving both the problems of gaseous dioxins, particulate dioxins and dust on a minimised footprint and with minimised pressure drop and operational costs.

The simplicity of the concept (no moving parts, no fluid or gas injection etc) ensures a trouble free operation to:

• Avoid the plugging of the catalyst & improving the filtration
• Avoid the risk of Ammonium Bisulphate (ABS) formation
• Increase the availability of the plant
• Limited additional footprint
• Minimise the exploitation cost.

Description
The concept of the Keppel Seghers CATFILTER is based on the synergy between a high efficiency fabric filter and a bed of honeycomb catalyst; two proven, simple and efficient technologies.

This very simple and secure technology concept consists in adding the honeycomb catalyst modules in one layer above each compartment of the fabric filter. The perfect laminar flow and the low face velocity (about three times lower than the typical face velocities in a traditional SCR reactor) at the outlet of the bags sealing plate guarantees the high dioxin destruction efficiency (up to 99%) with low pressure drop.

The Keppel Seghers CATFILTER can be combined with ammonia injection at high temperature (in the post combustion chamber) for preliminary removal of nitrogen oxides step. Having the Keppel Seghers CATFILTER work at lower temperature (180 - 240°C) will make the catalyst to destroy the gaseous dioxins and to act as a polishing step for the nitrogen oxides removal. The absence of high local ammonia concentration guarantees a trouble free operation without risk of ammonia salts formation whatever is the operating temperature.