One way of producing renewable energy is via waste gasification to syngas. However, the differences that occur in waste composition can make it difficult to control this gasification and often lead to inconsistent syngas compositions.
Consistently high-quality syngas production can be ensured by closely monitoring gas composition and adjusting process conditions during gasification. Infrared sensors are the ideal solution for monitoring syngas composition during waste-to-energy processes.
Business, consumer, government, and regulatory demands for green energy have increased significantly in the last ten years, thanks to an increasing awareness of the limited and polluting effects of fossil fuel resources.
This demand for green energy is expected to continue increasing as many of the globe’s most influential companies are committed to the use of 100% renewable energy by 2020 under RE100.1,2
Figure 1. Extraction of non-renewable fossil fuels damages sensitive ecosystems. Image Credit: MustangJoe/Pixabay
Producing Syngas from Renewable Resources
Syngas can be burned to produce heat and electricity or be converted into liquid fuels. Consequently, one way of generating green energy is via the gasification of biomass or waste feedstocks to produce syngas.3,4
Globally, 4 billion tons of waste are produced each year, which makes waste management an on-going global issue. At present, most waste is either sent to landfill or incinerated. The majority of waste sent to landfill can be reduced using waste-to-syngas processes, as energy is released from waste without producing as many emissions as the incineration process.4-6
Figure 2. Waste management is a global issue. Image Credit: vchal/Shutterstock.com
However, there are challenges surrounding the generation of syngas from waste. Syngas quality can vary significantly as it can be hard to control waste gasification. Moreover, the formation of tar and other impurities during the waste gasification process can make it expensive and challenging to operate down-stream processing. Currently, only 0.5% of syngas is produced from renewable resources such as biomass and waste.4,7,8
Ideal Syngas Compositions Vary by Application
Syngas is composed of hydrogen, carbon monoxide, and trace amounts of CO2, tar, methane, hydrogen sulfide, water vapor, as well as other trace species. Almost any carbon feedstock can be used to produce the mixture via gasification – a process that involves heating feedstock to an extremely high temperature with a small amount of oxygen present.
Although it may sound simple, a complex combination of equilibria and chemical reactions is involved in gasification, which results in differing syngas compositions.4,9,10
The generalized gasification reaction is as follows:
Hydrocarbon feedstock → CO(g) + H2(g) + CO2(g)
The specific chemical reactions involved in gasification are as follows:
2C + O2 ⇌ 2CO
C + CO2 ⇌ 2CO
C + H2O ⇌ CO + H2
C + 2H2 ⇌ CH4
CO + H2O ⇌ H2 + CO2
There are numerous potential applications for syngas. Syngas combustion can be used to generate both electricity and heat directly. Liquid fuels can also be produced from syngas, such as methanol, ethanol, diesel, and gasoline for later use.
Different demands are placed on syngas composition in each syngas application. As an example, an H2/CO ratio of 1.0-4.0 is required for methanol synthesis, in combination with a CO2 concentration of 4-8%.4,8-10
Controlling Syngas Composition and Quality is Vital
A variety of waste and biomass feedstocks can be used to make syngas, including agricultural, municipal, plastic, food, wood, and cardboard waste. As the composition of each feedstock varies, so, too, does the composition of the syngas produced.
The final syngas composition can be affected by other factors, such as the composition of the gasification atmosphere, pressure, temperature, residence time, and the presence of any catalysts used during the process.4,11,12
Monitoring syngas composition and varying reaction conditions can help maintain a constant syngas composition which is suitable for an intended application. For example, tar formation can be reduced by injecting CO2 during municipal waste gasification. This also increases the concentration of CO in the syngas produced.
Furthermore, identifying the appropriate gas conditioning processes for obtaining the ideal syngas composition can be facilitated by using online measurements. Consequently, during gasification process development and operation, gas composition monitoring is essential.4,13
Several companies have developed waste gasification technologies. One example is Burkhardt Energy, which supplies gasifiers that produce syngas to generate heat and power using wood pellets.
Using these homogenous wood pellets, Burkhardt Energy systems are now able to deal with difficulties associated with heterogeneous waste streams. The composition and quality of syngas can also be carefully controlled via the combination of gas composition measurement systems from Edinburgh Sensors and intelligent air and fuel regulation.14,15
Infrared Gas Sensors from Edinburgh Sensors
A leading supplier of high-quality gas sensing solutions, Edinburgh Sensors creates solutions that are perfect for monitoring syngas composition during waste-to-syngas conversions. They are easy to use infrared sensors, and they provide fast online measurements of CH4, CO, and CO2 concentrations.
Edinburgh Sensors currently offers OEM infrared sensors (Gascard NG) and complete gas monitors (Guardian NG series). These can be easily incorporated into automated systems which maintain gas composition and quality by adjusting syngas production conditions.
Infrared detectors do not interact directly with the syngas and any contaminants, unlike other available sensors. This protects the detector from damage. Consequently, infrared sensors are low-maintenance, long-lasting, and robust, when compared with different gas composition sensors.16-19
Unlike other IR sensors which struggle with variations in pressure or temperature, the sensors offered by Edinburgh Sensors ensure accurate results in numerous gasification environments through extensive pressure and temperature correction. Edinburgh Sensors’ infrared sensors deliver reliable and precise measurements of gas composition, ensuring high-quality and consistent syngas production.16-19
Figure 3. Gascard NG from Edinburgh Sensors.
References and Further Reading
- ‘RE100 Progress and Insights Report, January 2018’ http://media.virbcdn.com/files/97/8b2d4ee2c961f080-RE100ProgressandInsightsReport2018.pdf
- ‘Competition in Electricity Markets with Renewable Energy Sources’ — Acemoglu D, Kakhbod A, Ozdaglar A, The Energy Journal, 2017.
- ‘Renewable Energy: Sources and Methods’ — Maczulak AE, Infobase Publishing, 2009.
- ‘Progress in biofuel production from gasification’ — Sikarwar VS, Ming Z, Fennell PS, Shah N, Anthony EJ, Progress in Energy and Combustion Science, 2017.
- ‘Progress and challenges to the global waste management system’ — Singh J, Laurenti R, Sinha R, Frostell B, Waste Management & Research, 2014.
- ‘What a Waste’ — World Bank Group, 2012
- ‘State of the Gasification Industry – the Updated Worldwide Gasification Database’ — Higman C, International Pittsburgh Coal Conference, 2013.
- ‘Gasification Can Help Meet the World’s Growing Demand for Cleaner Energy and Products’ — Kerester A, Cornerstone: The Official Journal of the World Coal Industry, 2014.
- ‘Report on Gas Cleaning for Synthesis Applications’ https://ec.europa.eu/energy/intelligent/projects/sites/iee-projects/files/projects/documents/thermalnet_report_on_syngas_cleaning.pdf
- ‘Gasification’ — Higman C, van der Burgt M, Elsevier, 2008.
- ‘Waste into Fuel—Catalyst and Process Development for MSW Valorisation’ — Pieta IS, Epling WS, Kazmierczuk A, Lisowski P, Nowakowski R, Serwicka EW, Catalyst, 2018.
- ‘Biomass Gasification: A Review of its Technology, Gas Cleaning Applications, and Total System Life Cycle Analysis’ in ‘Lignin – Trends and Applications’ — K Koido, T Iwasaki, Intech, 2018.
- ‘An Investigation into the syngas production from municipal solid waste (MSW) gasification under various pressures and CO2 concentration atmospheres’ — Kwon E, Westby KJ, Castaldi MJ, Proceedings of the 17th Annual North American Waste-to-Energy Conference, 2009.
- ‘Heat and Power with Wood Pellets’: Accessed December 2018
- ‘Gasification of Waste Materials: Technologies for Generating Energy, Gas, and Chemicals from Municipal Solid Waste, Biomass, Nonrecycled Plastics, Sludges, and Wet Solid Wastes’ —Ciuta S, Tsiamis D, Castaldi MJ, Academic Press, 2017.
- ‘Landfill: High quality gas sensing solutions’ https://edinburghsensors.com/industries/landfill/
- ‘Biogas: High quality gas sensing solutions’ https://edinburghsensors.com/industries/biogas/
- ‘Guardian NG’ https://edinburghsensors.com/products/gas-monitors/guardian-ng/
- ‘Gascard NG’ https://edinburghsensors.com/products/oem/gascard-ng/
This information has been sourced, reviewed and adapted from materials provided by Edinburgh Sensors.
For more information on this source, please visit Edinburgh Sensors.