MSW Incineration To Power
Incineration is one of the waste treatment technologies that involve the combustion of Municipal Solid Waste (MSW) without any pre-treatment (also called mass burning). Mass burning has been in practice in developed countries for more than 100 years. More than 600 mass burning plants are operating around the world.
Until 2000, much importance was not given to the management of MSW in Asia and Africa. But, once CDM activities began, the project developers started paying attention to MSW projects for the benefit of revenue from CER sales which would make the project feasible.
Volume reduction of MSW for about 90% is possible with incineration plants, thereby resulting in considerable land saving, as land will not be required to dispose of the 90% MSW.
Only few countries in Asia have a long history of proper management of MSW using incineration power plants. As of now, in Singapore, 4 power plant of sizes ranging from 30 MW to 80 MW are in operation (for more than 25 years) and one more plant is under commissioning. A 2.5 MW plant is in operation in Phuket, Thailand.
The lower heating value of MSW varies considerably from country to country depending on several factors. In general, if the economic situation is better, then the heating value will be higher.
For the mass burn facilities, the minimum calorific value requirement is 7 MJ/kg on an annual average basis.
The moisture content and percentage of combustible are also important parameters in MSW mass burn technologies. The impact of MSW scavenging on LHV should also be taken into account.
In MSW mass burn system there is no pre-treatment except the removal of visible bulk items. However, some of the wastes such as construction debris, earth, concrete, stones, chemical waste, explosive or highly flammable waste, carbon fibres, insulation materials, Polyvinyl Chloride (PVC) etc., are not suitable for mass burn. It is also advisable to separate biodegradable wastes from MSW to use in digesters so that biogas resulting from the digester can be used to generate power using gas engines.
MSW plants generally have limitations in the usage of steam cycle and the plant design concept is different from biomass combustion system. Due to the level of complexity in design and lower demand for such plants in developing countries, there are only limited suppliers available in Asia. Though several suppliers may claim that they have the technical know-how, it is worthwhile to do a due-diligence on the supplier’s capability. The equipment suppliers need more knowledge in combustion to burn MSW than to burn any other kinds of fuels. The power plant should be designed with more flexibility and plenty of margins. Generally, the excess air requirement is high.
The investment cost and annual O&M costs for such MSW based power plants are much higher than biomass projects. The revenue generation from the sale of electricity alone is not sufficient to make the project commercially attractive. The major aspects which make the project commercially attractive are the tipping fee and CDM CER revenue. The higher investment cost is mainly because of the use of high corrosion resistant materials for incinerator and complex environmental control systems. SOx, NOx, dioxin, heavy metals, HCl and air born particulates, fly ash and bottom ash are the pollutants from mass burn power plants. The devices/processes commonly used for effective removal of pollutants include electrostatic precipitators, fabric filters, scrubber & lime injection system and activated carbon injection system.
With the use of modern technologies, it is also possible to minimise water pollution, odour and noise problems. It is also possible to recover ferrous metals from the ash which provides additional revenue.
Implementing MSW projects are more time consuming than biomass power plants as very careful preparatory work are needed for the incineration plants. Without proper preparation, the chances of failure for such plants are high. While we have visited several successful MSW plants that are in operation for more than 10-20 years, we have also come across several failure plants which were sold as scrap. Hence, project developers should pay adequate attention and do the necessary preparatory works before implementing these projects. It may also be worthwhile to engage qualified experts to study all modern concepts and innovative technologies. But the technology selection should be done carefully.
Although MSW plants are eligible under Clean Development Mechanism, there are certain restrictions in selection of technology and usage of MSW. Therefore, the project developer should not neglect these aspects while developing the projects to get CDM CER revenue. The potential for incineration plants in developing countries is high in the near future.
Among all MSW management systems, incineration to power is getting more and more popular in cities as it eliminates the need for land requirement in land filling. However, for the existing landfill sites that are in operation for more than 10 years, landfill gas recovery and power generation using gas engine is practiced. In some sites, engineered landfills are also used.
Refused Derived Fuel (RDF) combustion, gasification and pyrolysis are also used as other options for power generation from MSW. For services related to MSW to power, contact us.