De Danske Gærfabrikker (DDG) (The Danish Yeast Factories) produce 25,000 tonnes of yeast per year, around the clock. The yeast production is a sensitive fed-batch fermentation process, e.g. with sterilisation, garnish, cultivation, centrifugation and filtration. At yeast production, temperatures must only fluctuate very little, and therefore it is monitored, through the highly automated process, around the clock.
Since DDG were going to be burning coal continuously on their 15 MWt boiler, the boiler should be optimised for emissions, including NOx emissions, to meet government requirements.
In order to design the most efficient customised SNCR system, AET performed an on-site test with different locations of NOx lances in the furnace, e.g. based on the design of the furnace, grate, secondary air injection and temperature distribution in the furnace.
It was found from the test that ammonia water was an optimal NOx reduction medium, as it does not cause salt deposits in the boiler and does not give rise to increased CO emissions.
The test was conducted in March 2018 and verified by third party. The order was received in APR 2018, the plant was commissioned taking into account avoiding unnecessary downtime in DDG's production and the plant was delivered NOV 2018.
The AET SNCR DeNOx system is an integrated part of the boiler control, as this has been made in the existing ABB control system for the boiler. AET SNCR DeNOx System reduces NOx emissions by approx. 25%, so that the current emission requirement can be met. AET's SNCR DeNOx System is designed to reduce even more.
The plant is extremely reliable and runs smoothly, seeing that the AET SNCR DeNOx system, made of stainless steel, was adapted to our boiler, made of stainless steel, and also because the plant can handle the rapidly varying steam vapour we experience due to the batch-based process, says Technical Director, Jack Domino.
The plant consists in its simplicity of a tank for ammonia water, control panel, injections lances at one level in the furnace, NO meter and control system.
The Danish Yeast Factories (De Danske Gærfabrikker), which originate from the De Danske Spritfabrikker (The Danish Destilleries), are today owned by the Canadian family owned Lallemand Inc, which employs 2,900 people in 40 different countries.
The Danish Yeast Factories produce a large part of the yeast sold to the bread industry, local bakers and grocery stores. In addition, De Danske Gærfabrikker produce specialties such as wine yeast, yeast extracts and yeast for animal and human nutrition.
Aalborg Energie Technik a/s (AET) is a leading, independent engineering and construction company that supplies and services biomass-fired plants, including emission-enhancing systems.
The business includes design, engineering, delivery and service of plants combusted with any variety of biomass. The AET Biomass Boilers and AET Combustion System are based on more than 30 years of practical experience with industrial processes, steam generation and biomass combustion.
AET has a recognised reputation for supplying biomass-fired plants with exceptionally high efficiency, high availability, high fuel flexibility and low emissions.
Service Engineer: Kjeld Arendt, kAr@aet-biomass.com, +45 23 23 71 29
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