LAWI - Model EtaPlant -Boiler Islands & Power Plant Systems

Ash conveying systems integrated into the LAWI EtaPlant® are divided into two: the bottom ash handling and fly ash handling. LAWI provides ash handling systems for the LAWI EtaPlant® that meet the customers` requirements in consideration of usage of ash (dry or wet), ash cooling, ash density, conveying capabilities and distance to storage facility.

Due to increasing environmental requirements, the cleaning of exhaust gases is increasingly becoming a key issue in the design of power plants. LAWI ensures compliance with the statutory emission limits by means of a downstream flue gas cleaning system integrated into the LAWI EtaPlant®.

Particles are separated by bag filters or electrostatic precipitators (ESP) from the flue gas. In addition to minimal dust emissions, the bag filter can also guarantee very low pollutant concentrations in the clean gas due to intensive sorption processes in the filter cake when using semi-dry or dry processes. For the reduction of acidic pollutant gas components like SO2, HCl or HF from the flue gas stream semi-dry or dry processes are being applied. Thereby, calcium- or sodium-based sorbents are added into the flue gas stream for absorbing the acidic pollutant gases. It is also possible to apply wet processes, if requested.

Organic substances such as dioxins (PCDD) and furans (PCDF) are formed during each combustion process. Sufficient high combustion temperatures and a retention time of more than 2 sec above 850°C ensure the elimination of those. Only during cool down of the flue gases along the boiler a recombination of PCDD/F can occur under certain circumstances. This amount on organic substances can be separated by adsorption on activated carbon or other dedicated additives with large internal surface together with heavy metals like Hg or Hg compounds.

NOx emissions are hold already on a very low level due to the low excess rate and the advanced use of recirculation gas within the LAWI EtaComb® Combustion System and meets thus already strict environmental regulations - with the additional usage of a Selective Non-Catalytic Reduction (SNCR) or a Selective Catalytic Reduction (SCR), particularly low NOx limits can be achieved.

For biomass mostly the installation of a dedusting unit like ESP or bag filter is sufficient for flue gas cleaning. Measures for all other pollutants like NOx or acid gas compounds are depending on the fuel properties, local emission limits and partly also on the combustion process.

For WtE power plants a combination of a dry or semi-dry sorption system together with a fabric filter and optionally a DeNOx system is recommended.

THE CEM unit measures continuously the pollutants emitted into the atmosphere in exhaust gases from combustion in order to ensure and constantly measure the emissions from the stack.

Derived from the specific requirements of the project such as available plot or the intended fuel modes and mixtures, LAWI integrates the optimal solution for the transportation of fuel to the LAWI EtaComb® fuel dosing inlet. Such systems can be vertical (bucket elevator) or slope-style applications (apron or belt) that are designed in redundant configuration and equipped with residue extractors to ensure a constant fuel feeding of the LAWI EtaPlant® safely and reliably.

The LAWI fuel dosing provides a reliable and fully automated system, which allows trouble-free processing of feedstock into the combustion. This fuel dosing system is hydraulic driven, which allows independent feeding of each grate lanes. It allows proceeding a wide range of feedstock and lead to full fuel control during the power plant operation.

The design concept of the LAWI EtaComb® Combustion System with exhaust gas recirculation is developed and patented by LAWI Engineering GmbH. By returning the energy of the exhaust gas back into the process, the exhaust gas temperature and therefore the heat loss at stack is reduced. Consequently, it is possible to achieve an absolute combustion efficiency of up to 99%.

Additionally, with the integration of high-grade plant components into the LAWI EtaComb® Combustion System an unsurpassed plant net-efficiency of up to 28% electrically can be accomplished.

The LAWI EtaComb® post-combustion chamber design allows for an optimum protection of the highly stress exposed super heater coils from erosion and fouling and a complete burn-out of flue gas with 2 seconds after last air injection

The natural circulation steam boiler systems of the LAWI EtaPlant® are always designed in Germany and are taylor-made for the specific application. The LAWI boiler are efficient water tube single drum boiler systems with secondary heating surfaces, such as evaporators, superheaters, economizers and air preheaters that accommodate the requirements of stable process steam supply to the industry as well as high pressure steam (superheated steam) supply for electric generation.     

LAWI’s long-term experience and expertise in the design of boiler that use flue gases from solid fuels forms the basis for being capable of addressing the high thermal, chemical and mechanical demands even in difficult process conditions (contaminated gases). LAWI boiler are combined with the LAWI EtaComb® combustion systems presenting our customers an outstanding performance of efficient and reliable steam generation out of one hand.

Examples of LAWI EtaPlant® boiler applications are:

• Common vertical water tube boiler for biomass with capacity of up to 120 MWth and until 95 bar at 515°C
• Tail-End water tube boiler with vertical arranged heat exchanger for waste fuels such as RDF, SRF or MSW

Benefits of LAWI boilers are:

• Thermodynamically advanced heating surface design and materials
• Highest possible techno-commercial efficiency
• Safe operation as well as low maintenance requirements
• Control systems guided by model predictive control
• Fabricated with state-of the art production and factory testing technologies and quality assurance system
• Inspection and acceptance by ASME or any internationally recognised approval organisation