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SELECTICE CATALYTIC REDUCTION
TIER III regulations in ECAs from January 1st 2016 can at present only be achieved by using SCR Technology… Learn more!
is based on a long-time proven technology applied on land based exhaust gas cleaning systems where calcium powder is used… Learn more!
The DryEGCS® technology was especially developed for 4-Stroke engines used in the maritime industry to clean the exhaust gas of vessels. This system is adapted from land-based applications and calcium hydroxide [Ca(OH)2] in granulate form is used for the absorptive process. This proven technology removes more than 95% of the sulphur oxides (SOx) from the exhaust gas and delivers excellent results in both technical and economical aspects. Sulphur is a natural compound of crude oil and it appears in different concentrations depending on the source of the crude oil. It can be as high 6 vol. %. The sulphur is chemically bound to the hydrocarbons of the oil. The binding energy is quite high which makes it so as difficult and energy consuming to separate the sulphur from the hydrocarbons. During the combustion process inside the engine the sulphur is oxidized to SO2 (app. 95 to 98 %) and SO3 (app. 2 to 5 %). A fraction of the SOx reacts to sulfates and turns into particular matter but the major part appears as gaseous SO2 and SO3 in the exhaust gas.
The DryEGCS® integrated downstream the turbo charger can be operated at temperatures between 300 – 410°C. The exothermic absorption process causes no temperature loss of the exhaust gas, hence boilers and economizers can be operated as usual. The schematic design of the DryEGCS® process illustrates the way of the exhaust gas in and out of the absorber where the chemical reaction between granulate and exhaust gas takes place. The absorber acts as particle filter as well since it removes rough sooty particles and other residues from the exhaust gas. The DryEGCS® causes a back pressure of up to 12 mbar, according to engine manufacturers a tolerable value.
In case of need a fan could be integrated to minimize this back pressure. A silo on top of the absorber supplies fresh granulates. A controlled extraction of the residues underneath the absorber regulates its consumption. Pneumatic transportation of fresh granulates or residues allow flexible planning of storage tank locations onboard. A control cabinet automatically inspects all operational parameters.
The integrated ‘scheme B’ monitoring system continuously plots the emission values and proves that all regulations are met. In case of need the DryEGCS® can easily be shut down by using the bypass.
Selective Catalytic Reduction SCR (DeNOx)
TIER III regulations in ECAs from January 1st 2016 can at present only be achieved by using SCR Technology. NOx is a generic term for mono-nitrogen oxides (NO and NO2) which are produced during the combustion process, especially at high temperatures. In a SCR process nitrogen oxides react with ammonia or urea as reducing agent to form nitrogen (N2) and water vapour (H2O) which occur naturally in the atmosphere.
The SCR process is extremely flexible concerning flow rates and flue gas compositions with the exception of high contents of heavy metals, dust load and especially sulphur oxides which can react with the NH3 to ammonium hydrogen sulphate (NH4HSO4) that clogs the SCR surface and reduces its efficiency.
In consequence ENVAIRTEC offers the DryEGCS® combined with a downstream integrated SCR as an attractive option, technically as well as economically. The SCR process reliably achieves and secures a NOx reduction level of well above 90 %. And the SCR technology is applied in a couple of thousands of combustion
processes on land and has proven its long-term efficiency. More than 300 SCR systems are currently operated onboard of vessels. Envairtecs’ R&D program incorporates optimization of conventional SCR technology and development of new catalysts to effectively meet the future demands of the shipping industry.
The Seatrade Award 2011
The Green Ship Technology 2011
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