Reliable Technology – Continuously Improved and Optimised
Grate combustion is the best-proven thermal waste treatment technology for mixed municipal solid waste, and the heart of any modern, state-of-the-art energy from waste (EfW) plant. HZI has constantly optimised, developed and adjusted its proprietary grate combustion systems to meet changing statutory requirements. Grate combustion is now the most advanced technology with regard to environmental sustainability, operating reliability and cost-effectiveness.
Grate Combustion
Our in-house grate combustion technology is designed specifically for the thermal treatment of municipal solid waste. It has been constantly optimised through decades of operating experience, and now achieves an unsurpassed level of efficiency and reliability.
The core of the combustion process is a maintenance-friendly, inclined reciprocating grate, plus the following elements:
- Waste feeding system
- Air-cooled or water-cooled grate
- Combustion air system
- Flue gas recirculation system
- Advanced combustion control system
- Bottom ash extractor
Well-Proven and Reliable Combustion Technology
The rugged construction of the HZI grate and its insensitivity to highly heterogeneous waste fractions are why it remains the most widespread and reliable method for the thermal treatment of residual waste today. In fact, it constitutes the very heart of energy from waste plants, and is the technology of choice not only for untreated municipal and industrial wastes, but also for refuse-derived fuels (RDFs) and pre-treated waste.
The waste crane supplies the waste to the feed hopper and ram feeder, which doses it onto the HZI grate in a controlled manner. On the grate the waste is combusted in accordance with strict regulatory requirements governing residual total organic carbon (TOC) content in the resulting bottom ash.
Generating Steam While Cooling the Flue Gases
The flue gas resulting from the combustion process is cooled down in the boiler. In the process, heat is transferred to water, producing steam. This steam is expanded in a turbine or used for heating purposes: what is called combined heat and power (CHP). Some 173 tailor-made HZI steam boilers have been installed in EfW plants worldwide to meet individual client objectives.
Precisely Adapted for the Highest Combustion Efficiency
More than 1100 HZI grates have been built globally, with capacities ranging from 4 to up to 50 tonnes per hour.
The air- or water-cooled grate with its robust design has proven to be very reliable, and is the most favourable solution in terms of capital and maintenance costs. For waste with higher calorific values, water-cooled grate bars ensure increased lifetime.
On the grate, the waste is combusted in accordance with strict regulatory requirements governing residual total organic carbon (TOC) content in the resulting bottom ash.
The element-based design allows precise adjustment of airflow and waste transport by both lane and zone. This makes the grate ideal for getting equipped with an advanced combustion control system.
Combustion Control System
The combustion control system (CCS) developed by Hitachi Zosen Inova provides increased control quality for all important process parameters. The advantage for your plant: controlled and uniform combustion, stable steam generation, reduced component stress and less fouling of the combustion chamber. The main control objectives of the CCS are:
- Maintaining a set constant steam flow rate
- Keeping the volumetric combustion air flow rate constant
- Assuring complete gas burnout by stabilising the oxygen concentration in the flue gas and in combination with the homogenous flow
- Running the plant in the optimal operation point under consideration of process limits
Enhanced Combustion Control System
The Enhanced Combustion Control System (CCS+) increases revenues and reduces costs at the same time. The software monitors the combustion process and supplies real-time data feeding an AI module that reacts in case of exceptional events.
With CCS+, more detailed data enables a very high degree of automation. As a result, the system-specific safety margins are more effectively exhausted, and operation is optimised. The CCS+ thus helps the plant operator to achieve the facility’s maximum performance.
The system can be installed as an upgrade to a combustion control system or as a retrofit.