Installation for the energetic management of the over-sieve fraction of municipal waste and sewage sludge with the addition of plastics by using the gasification process which is finalised with a highly effective production of electricity and heat in cogeneration.
The installation consists of 5 basic technology units:
Fuel preparation unit
In this unit, the basic task is the preparation of a uniform fuel consisting of:
- over-sieve fraction of municipal waste - preRDF - 75-80% by mass,
- dried sewage sludge (water content max. 15%) - 20% by weight,
- polyolefin waste for energy stabilisation (optional) - 5%.
The over-sieve fraction of municipal waste, sewage sludge and plastics are subjected to homogenization in planetary mixers. The prepared fuel is formed into pellets, which ensures stable operation of the gasification reactor. The advantage of this approach is the fact that, it ensures a continuous fuel transportation to the gasifier and restricts the amount of residual air in the porous structures of the materials.
Gasification is carried out by a movable segmented grate. Gasifying agent is air, whereas the energy efficiency in terms of energy conversion of formed fuel / syngas amounts 82%. The calorific value of the syngas is approx. 5.6 MJ/Nm3.
The innovative generator design:
- increases the efficiency of the process (approx. 5-6%) compared to the standard construction.
- ensures the stability of the syngas composition,
- maintains a low temperature of the syngas at the outlet.
Furthermore, low temperature gasification process minimizes the production of slag, whereas the innovative use of thermal energy recycling guarantees process stability and quality of the syngas.
The syngas purification system plays an important role in the entire technology line. This is due to the need to meet very strict quality requirements for the permissible amount of pollutants, especially when fed to internal combustion engines. The syngas is purified from unwanted chemical residues tars and heavy metals in the system using the method "dry-wet".
Syngas treatment consists on:
- separation of tars through a cooling system and two-stage filtration,
- separation of acidic gases through absorption,
- thorough cleaning and stabilization of the syngas quality through adsorption.
In this process is generated a small amount of industrial waste, and also is carried out a continuous quality control of the syngas at the inlet to the cogeneration system.
Release of flue gases by using a continuous emissions monitoring system (CEMS)
The flue gases from the syngas combustion process in the engine will be discharged to the emitter. A continuous measurement of the quality of the process is provided in terms of fuel composition formed, the composition of syngas at various stages of production and the quality of exhaust gas. The scope for continuous emissions monitoring of flue gases includes all pollutants which are required to be monitored in syngas combustion plants.
Syngas combustion and energy production
This unit is composed by a highly efficient cogeneration system - internal combustion engine with a catalyst, generator and a combined heat and power (CHP) system. The energy efficiency of the engine is 34%, the total thermal efficiency is 56% and the overall efficiency of the cogeneration system is 90%. The designed engine has a built-in system for stabilizing and controlling the quality of the syngas. Minimum threshold of the syngas calorific value for this model is 4.6 MJ/Nm3.