Sep 9, 2024
Article
Landfills, a traditional method of waste disposal, are overflowing. These sites take up significant space and can pollute the environment as waste decomposes. In 2009, the European Environment Agency released a report advocating for the transition from landfill disposal to more sustainable alternatives [1]. One viable solution uses a thermal treatment process to burn waste and generate energy. While incineration can reduce landfill waste and create energy, it is important to understand how the waste incineration process works and which steps are needed to run it in a safe and environmentally conscientious fashion.
First, municipal solid waste arrives by truck and is stored for processing (Figure 1).
Next, the waste is introduced into a high-temperature furnace where it is burned. The burning process creates flue gas – a mixture of hot gases and byproducts – which must be thoroughly cleaned before release.
Finally, the heat generated in the furnace plays a key role in electricity production. This captured heat creates steam that drives a turbine, ultimately generating power.
In the rest of this article, the most important components of waste plant incinerator analysis are discussed, with a focus on how process analyzers are used to monitor emissions such as ammonia, sulfate, and heavy metals.
Incineration is a waste management strategy that reduces solid waste (i.e., landfill) while also converting energy. A projection from the UNEP indicates that municipal solid waste production will increase from 2.3 billion tons in 2023 to 3.8 billion tons by 2050 [2]. Therefore, ensuring the efficient and compliant operation of such incinerator plants is paramount but can be achieved through meticulous monitoring and mitigation.
Incineration technology has evolved, offering diverse options tailored to specific waste types. There are various types of incinerators: simple incinerators, fixed or moving grate incinerators, rotary kiln incinerators, and fluidized bed incinerators [3]. Each type possesses unique advantages in terms of capacity, efficiency, and emission control.
In a waste incineration plant, the journey begins with delivery of trash by collection vehicles (Figure 1). A grabbing mechanism (Figure 2) lifts the waste and deposits it into a high-temperature furnace.
Here, combustion occurs, breaking down the waste and releasing heat energy and flue gas – essentially hot exhaust containing combustion byproducts. Importantly, this heat from the combustion process is used to generate steam energy and to produce electricity in the adjacent thermal power plant.
During incineration, flue gas containing pollutants like acidic gases, heavy metals, and particulate matter (PM) is generated. The scrubber (Figure 3) acts as a barrier, capturing these pollutants before they reach the atmosphere.
The flue gas is not released directly into the atmosphere. Instead, it passes through several emission control steps (e.g., scrubbers and filters) in order to remove various undesired components that cannot be released to the environment. Scrubbers utilize water or specific chemical solutions to capture pollutants including PM, heavy metals, and acidic gases.
Finally, the leftover ash from the furnace and any wastewater generated during the cleaning process undergo rigorous analysis before they are discarded. This ensures these materials are properly treated and disposed of in an environmentally responsible manner.
These facilities do more than just dispose of waste materials—they also use the heat produced to generate energy.
Waste incineration plants thus offer a two-fold benefit: significant reduction of the volume of waste in landfills and energy generation.
Scrubbers, essentially the air pollution control units within the waste-to-energy incineration process, play an important role in maintaining emissions levels by trapping pollutants in liquids (Figure 4) or specialized dry materials.
Scrubbers reduce the emission of pollutants such as sulfur dioxide (SO2), nitrogen oxides (NOx), heavy metals, and PM. This allows waste incineration plants to comply with stringent environmental regulations.
By neutralizing acidic gases, scrubbers prevent acid rain formation, preserving soil fertility and aquatic ecosystems in areas near the incinerator.
Scrubbers positively contribute to public health by reducing the release of hazardous substances that can cause respiratory illnesses and other health complications.
Untreated (or undertreated) wastewater from waste incineration plants threaten the environment and public health. Accurate monitoring ensures the various effluents meet the requirements of discharge regulations and do not cause harm.
Process analyzers help to minimize mistakes that can occur during sample collection and laboratory analysis. They provide a real-time picture of plant conditions, allowing for proactive adjustments to optimize performance. Furthermore, online process analyzers eliminate the need for manual handling of potentially hazardous chemicals, enhancing safety for plant operators and personnel.
Despite being fully automated, online process analyzers deliver lab-grade accuracy, ensuring reliable data for critical decision-making.
Some segments of the waste-to-energy incineration process where online process analyzers can be installed for monitoring purposes are listed in Table 1. Metrohm Process Analytics offers a comprehensive suite of solutions for monitoring critical parameters in waste incineration facilities and power generation plants. These are described in more detail later in the article.
| Parameter | Analysis technique | |
|---|---|---|
| Flue gas / Furnace | Acids and heavy metals | VA / XRF |
| Calcium and sulfate | Titration | |
| Sulfate | Titration / Photometry | |
| Scrubber | Heavy metals | VA / XRF |
| Ammonia (NH3) in scrubber ash | ISE | |
| Sodium hydroxide, calcium carbonate, sulfate | Titration | |
| Cooling water | Sodium, ammonia (NH3) | Titration |
| Copper corrosion inhibitors | IC | |
| Heavy metals | VA | |
| Turbine | Flow Accelerated Corrosion (FAC) | IC / VA |
| Effluent for wastewater treatment plant (WWTP) | Zinc, cadmium, lead, mercury | VA |
| Manganese, iron (Fe2+/Fe3+), chromium (Cr6+), silica (Si4+) | Titration / Photometry | |
| Ammonium (NH4+) | ISE |
When should you choose process analysis over traditional laboratory measurements? Read our blog article to know which factors are the most important to consider when making this decision.
Laboratory vs. process analysis: Key factors for informed decision-making
Voltammetric analysis is a powerful technique for quantifying trace levels of heavy metals in incinerator emissions. A sensitive analytical method is needed as the environmental regulations for the release of these pollutants is usually in the µg/L (parts per billion, ppb) levels. By leveraging electrochemical principles, voltammetry offers high sensitivity and selectivity, enabling precise detection and quantification of pollutants.
Voltammetry works by measuring the electrical current produced by a sample when it is subjected to a changing voltage. This allows for the detection and quantification of various dissolved metals, anions, and cations in solution.
In power plants and incineration facilities, voltammetry proves invaluable for:
Scrubber optimization. VA helps monitor heavy metals like lead and cadmium within the scrubber effluent, ensuring optimal scrubber performance and preventing these contaminants from reaching the environment.
Application Note: Online analysis of cadmium in incineration plant wet gas scrubbers
Cooling water analysis. Cooling water systems are susceptible to corrosion and contamination by heavy metals. Voltammetry facilitates the detection of these pollutants, allowing for preventive measures and safeguarding the integrity of critical infrastructure (e.g., heat exchangers, cooling towers, and turbines).
Wastewater treatment efficacy. Effluent from power plants requires proper treatment before release. Voltammetry helps monitor heavy metals like zinc, cadmium, mercury, and lead in the wastewater stream, ensuring efficient removal and compliance with environmental regulations.
Traditionally, titration relied on manual sample collection and analysis in a lab, introducing the potential for human error. Online titration (Figure 6) revolutionizes this process by offering several key benefits as mentioned above.
Titration plays a vital role in various applications within power generation plants and waste incineration facilities, such as:
Protecting assets. Monitoring the ammonia (NH3) concentration in cooling water safeguards pipes, boilers, and other expensive equipment from corrosion.
Application Note: Ammonia in cooling water of thermal power plants
Combating corrosion. Consistently measuring the «m-number» (alkalinity) of cooling water helps to prevent corrosion within the system.
Application Note: Power generation: analysis of the m-number (alkalinity) in cooling water
Early detection of issues. Ultratrace analysis of iron and copper in power plant water provides early warning signs of potential corrosion problems.
Application Note: Monitoring corrosion in power plants with online process analysis – Faster ultratrace measurements of iron (Fe) and copper (Cu)
Boiler health. Continuous monitoring of silica levels in boiler feed water ensures the smooth operation of boilers and prevents costly downtime.
Application Note: Online analysis of silica in boiler feed water of power plants
Learn more about the principles of titration in our blog post.
IC excels at separating and quantifying ions in aqueous samples. When used in an online capacity in power plants, IC is ideal for monitoring trace levels of various analytes which helps with:
Corrosion control. Cooling water systems are susceptible to corrosion, which can adversely impact plant efficiency and safety of personnel. Monitoring the concentration of copper corrosion inhibitors in cooling water online with ion chromatography (Figure 7) allows for proactive maintenance and prevents costly equipment damage.
Application Note: Online monitoring of copper corrosion inhibitors in cooling water
Power plant optimization. Analyzing even trace levels of amines in the alkaline water-steam circuit of power plants helps to optimize system performance and minimize potential issues.
Application Note: Online trace analysis of amines in the alkaline water-steam circuit of power plants
[1] Diverting waste from landfill - Effectiveness of waste-management policies in the European Union — European Environment Agency. https://www.eea.europa.eu/publications/diverting-waste-from-landfill-effectiveness-of-waste-management-policies-in-the-european-union (accessed 2024-05-01).
[2] Environment, U. N. Global Waste Management Outlook 2024. UNEP - UN Environment Programme. http://www.unep.org/resources/global-waste-management-outlook-2024 (accessed 2024-04-24).
[3] Incinerator - an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/engineering/incinerator (accessed 2024-04-23).
Brochure: Environmental Testing Industry I - Online Analyzers for Municipal Wastewater Analysis
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