GEA Niro’s spray dryer absorbers are developed and used for
the removal of acidic pollutants, heavy metals, and dust from flue gases
of various origins, primarily fossil fuelled power stations, waste
incinerators, and steel industries.
The spray dryer absorber module is a key component in the cleaning of
gaseous pollutants such as SO2, SO3, HCl, Hg,
dioxins, etc. using the GEA Niro spray drying absorption (SDA) technology. The GEA
Niro SDA process has its origin in spray drying and
basically consists of a spray dryer absorber module, a GEA Niro rotary atomizer, a downstream dust
collector, and an absorbent feed preparation system.
Special features:
- High acid gas removal efficiencies
- Low capital cost
- Low power consumption
- Low water consumption
- Low operating and maintenance costs
- High plant availability
- Utilizes low water quality
Spray dryer absorber
Hot, untreated flue gas is introduced into the absorber module
via
gas dispersers for
optimum gas flow distribution and contact with the absorbent sprayed by the
rotary atomizer. The efficient contact between the gas and atomized absorbent
slurry allows for rapid mass transfer of acidic components from the gas phase
into the liquid phase. The alkaline absorbent neutralizes the absorbed acid and
the desired reaction product is formed while water is evaporated
simultaneously. A fraction of the dried end-product drops to the bottom of the
absorber chamber and is discharged, while the main part is removed from the
cooled, cleaned gas in the downstream dust collector. The clean gas passes
from the dust collector to the stack without re-heating.
The GEA Niro SDA process
uses slaked lime Ca(OH)2 as absorbent and produces a dry end-product
mainly consisting of fly ash and various calcium compounds. The absorbent is
either purchased directly as slaked lime or, more often and more economically,
prepared from burned lime CaO on site. From a buffer tank, the slaked lime is
pumped to the rotary atomizer by which it is atomized to droplets of less than
50 microns. Following the absorption of acidic components, the chemical
reaction, and the final drying, the powdery end-product is separated from the
gas phase and transported either to an end-product storage facility or recycled
in the SDA process for the improved utilization of excess absorbent.
The SDA technology features excellent performance for absorption of not
only primary pollutants such as SO2 and HCl, but due
to the combination of finely sprayed absorbent into the flue gas stream and the
subsequent dust removal, pollutants like SO3, HF, etc. are
almost completely removed. This feature allows for the use of
carbon steel as construction material throughout the entire flue gas path.
Other features of the GEA Niro SDA process are the possibiliity
to use low quality process water, such as waste water or even sea
water, and that the process generates no waste water.
The end-product from the process is a stable and dry powder that can be used
for a variety of purposes. The majority of the SDA product produced
throughout the world is re-used in road construction, building materials, and
for other purposes in the construction industry.
Worldwide, numerous GEA Niro SDAs are installed at power stations, steel
plants, waste incinerator plants, and as plants burning hazardous waste.
Common for the SDAs regardless of where they are installed is
that they are all operated to or above the required performance as set
by local authorities. Even today, the earliest SDA plants (installed
in the 1980’s) are still operating satisfactorily and well below the allowed
emission limits.
As the process inventor and holder of the key SDA equipment and know-how,
GEA Niro has established a network of trusted licensees and case-to-case
partners all over the world. This alliance-based market approach keeps expenses
low while the quality of the technology and service remains the best. As of
2011, GEA Niro has license agreements with a number of reputable companies in
the USA, South Korea, China and South Africa.
Safety aspects
All plants designed and supplied by GEA
Niro will enable the end user to obtain approvals put forward by the EU directive.
GEA Niro spray dryer absorber references:
- Total plants built: > 175
- Total number of absorbers: > 300
- Total number of atomizers: > 400
- Process installed at close to 20.000 MWe and 4.300 MWt power plant capacity
- Process installed at more than 140 incineration lines worldwide
- Process installed at more than 6.000 m2 sinter band worldwide