LAWI EtaComb® - Combustion & Moving Grate Systems

Biomass and solid wastes are available in large quantities almost all around the world and its thermal utilization is an efficient approach of not only carbon neutral electricity generation but also waste management. Biomass and other solid wastes, especially in multi-fuel applications, are non-homogeneous fuels, which vary in size, heating value and moisture. Hence, control of the combustion (also called furnace, incinerator, stoker) is essential for an efficient thermal utilization and therefore, the combustion system is the heart of every power plant of this kind. The combustion system is the most essential part in terms of efficiency and feedstock flexibility and is significantly responsible for the overall performance, because in it the feedstock is converted into thermal energy which can be further used for different purposes.

Why choosing a LAWI EtaComb® installation? The strategic technical development goals of LAWI Engineering have always been guided by the challenge of how to increase the efficiency and the flexibility of thermal solid waste utilization.

Over the last years of intense R&D we have combined our experience from 20 years of designing multi-fuel combustion systems & incinerators with moving grate technology and created the German patented LAWI EtaComb® of today. It was successfully installed in more than 40 projects in different countries across the world and proved to have a convincing combination of strong points and resulting benefits.

up to 98 %

Combustion Efficiency

up to 120 MWth

Firing Capacity

4.5-26 MJ/kg

Lower Heating Value

up to 65 %

Moisture Content

Biomass & WtE Combustion Systems

The requirements towards solid waste combustion systems are continuously increasing. Modern combustion systems are required to be not only efficient, robust and capable of utilizing multifuel applications but also to have the least possible environmental impact. Thus, releasing least possible emissions which requires full control of the entire combustion process.

The LAWI EtaComb® combustion systems are LAWI's answer to these challenges and provide a top-tier solution for the efficient utilization all sorts of solid wastes such as all kinds of biomass, municipal solid waste (MSW), industrial wastes and recovered fuels such as RDF and SRF. As a competent solution provider LAWI is well aware of the fact that specific plant configuration cannot be transferred to every other project due to project-specific requirements.

Therefore, LAWI develops a customized combustion system application together with each of our customer to specifically address each project requirement and to implement the perfect matching solution either on turn-key basis or on individually optimized scope of work – but it is always a LAWI EtaComb®.

EtaComb® Advance - LAWI's Flagship

The flagship of the LAWI firing systems is the LAWI EtaComb® Adiabatic - A high efficiency multi-fuel combustion system in which the conversion of solid fuels to heat takes place in a controlled and isolated adiabatic combustion. The LAWI EtaComb® Advance is available with different design features and can be applied in various applications and industries.

EtaComb® Direct Firing

The LAWI EtaComb® Direct Firing - LAWI's answer to applications with high calorific value fuels, homogenous single fuels or limited space requirements. The LAWI EtaComb® Direct Firing system is designed to be integrated into steam boilers and thermo-oil boilers and allows a controlled combustion process within or partly within the boiler radiant chamber.

Efficiency

A high plant efficiency increases the income from energy sales. Especially in terms of additionally procured fuels, every percentage point in efficiency represents a few months shortened pay-back time of investment.

Flexibility

Due to its natural origin, solid biomass or municipal solid waste are not homogenous. Wet, dry, coarse, fine, or contaminated with inert materials, the flexible multi-fuel LAWI EtaComb® Combustion Systems offer a wide range of options for firing the various fuel qualities with high reliability.

Emission

Even ambitious CO- and NOX-values may be guaranteed. The innovative exhaust gas recirculation system reduces the heat losses of exhaust gas at stack and reduces the formation of nitrogen oxides (NOX). Furthermore it avoids ash melting difficulties and its potentially expensive consequences, even when critical fuels are used.

Quality of Ash

Dry de-ashing and an outstanding burn-out of the ash can provide a valuable by-product and at least minimizes the costs of disposal.

LAWI Moving Grates for Solid Waste Combustion

Air-Cooled Moving Grate

The LAWI EtaComb® hydraulically driven moving step grate system with grate segments arranged in the form of stairs is especially developed for the operation for different kind of solid wastes of inhomogeneous characteristics.

The moving step grate design with multiple independent zones and a sophisticated zone-independent air distribution system allows a sufficient mixture of the fuel with air in each zone. The operation mode of the moving grates can be adjusted in relation of burning behavior as well as fuel size and bulk density.

Apart from the grate bars, the grate consists of grate carriages, support rollers, guiding tracks, guiding rollers, separation walls with moving grate base frame and casing as well as temperature and position instrumentation. Grate movement is controlled by timer and piston position control via proximity switches.

Water-Cooled Moving Grate

LAWI's water-cooled moving grate provides superior grate durability for combusting high calorific waste of up to 30 MJ/kg, which can cause high thermal stresses in the grate. The grate bar cooling is independent of the combustion air supply.

The water-cooled grate significantly reduces wear on the grate bars and maintains the long-term integrity of the grate surface.

LAWI Recirculation Gas System

Without coolant, solid waste fuels burn at temperatures at up to 1,800 °C. In order to avoid adherence deposits (ash melting) in the combustion chamber as well as damages to the boiler (high temperature corrosion), cooling-down of the furnace temperature is required. The standard principles are:

cooling down by excess air results in heat losses and high amounts of exhaust gas and, therefore in low efficiency
cooling down by water-wall chambers results in low flexibility for multi-fuel application

The solution is the LAWI EtaComb® Combustion System with recirculation gas technology for furnace temperature control and cooling purposes: highly flexible multi-fuel application combined with high efficiency. The combustion recirculation gas system provides combustion air and recirculated flue gas to the combustion chamber to allow a controlled and evenly distributed combustion and heat generation at all stages. The LAWI EtaComb® Combustion System operates on an automatically controlled, optimal air supply level with a very low excess air rate keeping the oxygen content below 4 %. This results in combustion efficiency over 98 % and very low emissions regarding CO, NOx, and unburned hydrocarbons.

LAWI EtaComb® - Product Features

Automated Radar-Controlled Fuel Dosing System
The hydraulic driven LAWI EtaComb® Fuel Dosing System provides a reliable and fully automated processing of feedstock into the combustion
Fire Protection System
LAWI's advanced ignition control and backfire protection system combining low oxygen content reci-gas supply with a hydraulic driven guillotine gate to safely control fuel ignition even for high calorific fuels (such as RDF) and protect the fuel dosing system.
Moving Step Grate
LAWI's hydraulic driven moving step grate with independent speed control of each grate zone allowing optimal fuel retention time in each combustion zone (drying zone, ignition zone, combustion zone and burn-out zone
Air & Gas Supply System
The LAWI EtaComb® operates on optimal air supply level with a very low excess air rate keeping the oxygen content 3-4 %. This results in combustion efficiency over 98 % because CO emissions and unburned hydrocarbons are kept on very low rates.
Refractory & Adiabatic Design
The adiabatic (heat insulated) combustion design with multi-layer brick lining that not only insulates but is highly resistant against chemical attacks during the combustion process
Post-Combustion Chamber
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
Advanced Automation System
LAWI EtaLogic®, the customized control and optimization system signficantly increases process stability and simplicity of operation for combustion and boiler, profiting from advanced MPC, adaptive controllers and using LAWI’s long-term know-how in biomass and solid wastes power incineration design.

Selected References - LAWI EtaComb®

Apr 2020

28 MWel Multi Fuel Biomass Power Plant, Suphan Buri | Thailand - LAWI EtaComb® 1000

Rice Husk, Wood Chip, Bagasse, Wood Bark

Suphan Buri | Thailand

Technical Project Data

Firing Capacity: 93.7 MWth
BMCR: 115 tph
Steam Parameter: 68 bar(a) | 485°C
Plant Type: Power Generation
Plant Capacity: 28 MWel

LAWI Scope of work

Overall Power Plant Basic Engineering
Owner's Consultant (Tech.)
EP Supply: LAWI EtaComb® 1000 Combustion System
- Boxer Type 6 Lane adiabatic Multi-Fuel Combustion with Post-Combustion
- 2x 3-Lane Fuel Dosing System
- Moving Grate
- Air System with Recirculation Gas
- LAWI EtaLogic® Control & Optimization System

Jun 2012

9.9 MWel Biomass Power Plant, Roi Et | Thailand - LAWI EtaComb® 400 - WINNER OF THAILAND ENERGY AWARD 2014

Eucalyptus Bark, Rice Husk

Roi Et | Thailand

Technical Project Data

Firing Capacity: 40 MWth
BMCR: 45 tph
Steam Parameter: 66 bar(a) | 485°C
Plant Type: Power Generation
Plant Capacity: 9.9 MWel

LAWI Scope of work

Overall Power Plant Basic Engineering

EPC Supply: LAWI EtaComb® 400 Combustion System
- Multi-fuel 3-lane adiabatic Combustion Chamber
- Fuel Dosing System
- Moving Grate
- Air System with Recirculation Gas

WINNER OF THAILAND ENERGY AWARD 2014

Jun 2022

16.6 MWth SRF Power Plant, Yeoncheon | South Korea - LAWI EtaComb® 200

Industrial Waste, SRF

Yeoncheon | South Korea

Technical Project Data

Firing Capacity: 16.6 MWth
BMCR: 20 tph
Steam Parameter: 19 bar(a) | 211°C
Plant Type: Heat Generation
Plant Capacity: 12.3 MWth

LAWI Scope of work

Detail Design & Engineering:
LAWI EtaPlant® WtE Boiler Island

EP Supply:
- LAWI EtaComb® 200 WtE Combustion System
- Water-Cooled Moving Grate
- LAWI EtaLogic® Control & Optimization System (PLC)

See all references