Incineration Plant Emissions Monitoring – December 03, 2015 – Gary Egerton – Environmental Science News Articles
Incineration is a rapidly growing method of waste disposal as well as an increasingly important source of energy. Emissions from waste incineration plants can potentially contain many harmful pollutants, but with the use of modern monitoring equipment, regulatory compliance can be ensured and emissions reduced to a minimum. This ABB Measurement & Analytics article explains the options available.
Incineration is playing an increasing role in municipal waste treatment as well as in energy supply. Around the world, some 2,200 incinerators dispose of around 255 million tonnes of waste per year. By 2017, 180 new factories, with a capacity of around 52 million tonnes, are expected to be built. Growth is particularly strong in Europe where, due to the ban on the landfill of untreated waste, a large number of waste incinerators have been built in recent years, and many more are under construction.
Incinerators reduce the volume of waste by about 95 percent, significantly reducing the space required for disposal. Recoverable energy is just under 3 MWh per tonne of municipal waste, of which around 25 percent can be converted to electricity and the remaining 75 percent can be used for district heating.
Waste incineration produces more pollutants than a natural gas plant, but less than a coal plant. Flue gases can contain high levels of particulates, heavy metals, dioxins, furans, sulfur dioxide and hydrochloric acid. Incineration also produces CO2, about a ton per ton of waste, but since much of the waste is biological, incineration is often classified as renewable energy.
A number of techniques are used to ensure that pollutants are reduced within allowable limits. For example, factories are equipped with a high temperature zone where gases are heated to a minimum of 850 Â° C for at least two seconds to ensure the decomposition of dioxins.
A flue gas cleaning system, located downstream of the combustion processes, ensures that the concentration of emissions is below legal limits, using various systems for removing dust, acids, heavy metals and micropollutants. The resulting emissions consist of fine ash in the flue gases, with varying amounts of organic and inorganic matter, which depend on the composition of the waste and the incineration process.
Directive requires control
In the European Union, the Industrial Emissions Directive (IED) 2010/75 / EU imposes strict obligations on Member States to ensure that Continuous Emission Monitoring Systems (CEMS) are used to monitor flue gases. These systems must meet EN14181, the CEN standard for quality assurance of automated measuring systems in chimneys.
The Directive applies to a range of different types of incinerators, in addition to the municipal waste facilities already mentioned. These include incinerators dealing with hazardous chemical or clinical waste, which may be owned and operated by specific waste producers or may serve multiple customers on a contractual basis. It also includes co-incineration plants such as cement plants, which burn waste as fuel, as well as advanced technologies such as gasification and pyrolysis.
All incineration plants that fall under the Directive are required to monitor a variety of contaminants in their emissions, including carbon dioxide, oxygen and water vapor, total organic carbon, hydrogen chloride , hydrogen fluoride, dust and oxides of sulfur and nitrogen. . These are in addition to a wide range of specific chemical species that could be considered a possible risk in a particular facility. Monitoring should be continuous, providing average readings every half hour and daily.
In the event of a measurement fault, operators must act quickly to remedy any malfunction in their monitoring equipment, as the directive only gives them four hours to resolve the problem before having to scale back or shut down their operations.
In addition to ensuring regulatory compliance, data from emissions monitoring technology can provide valuable insight into plant performance, enabling plant operators to optimize efficiency and operational control. which results in better energy recovery.
In a traditional system, monitoring is done by extracting a small sample of flue gas, using a pump, into the CEMS system via a sample probe. In some systems, the sample is diluted with clean, dry air, usually at a ratio of 100 to 1, to make hot, wet, or sticky samples more manageable. The sample is then transported through a sampling line, or umbilical, to a collector where individual analyzers can extract samples. A data acquisition and processing system receives the output signal from each analyzer and collects and records the emission data.
An alternative method is dry hot extraction or direct CEMS. Here, the sample is not diluted but is transported along a heated sample line in a sample conditioning unit. The sample is filtered to remove particles and then dried, before entering the sample manifold. An advantage of this method is that it makes it possible to measure the proportion of oxygen in the sample. Since dilution systems mix the sample with clean air, they cannot measure oxygen.
A more modern approach is to measure the flow of all pollutants at a single point. Fourier transform infrared spectroscopy (FTIR) analyzes the spectrum of incoming infrared light. The infrared spectrum makes it possible to identify molecules as well as concentrations of substances. An electronically controlled air injector sampling system transports sample gas, at constant pressure, from the sampling point to the analyzers. To prevent pressure from influencing the sample, which could happen with a conventional diaphragm pump, no moving parts are used. Adjusting all gas sampling, transport and measuring elements to a constant temperature of 180 Â° C ensures that the chemical and physical properties of the sample are maintained while avoiding possible deterioration due to condensation. The absence of sample pumps, hot ovens and connection gaskets ensures accurate measurement and minimizes maintenance costs.
This technology also makes it possible to improve the efficiency of the flue gas purification system by analyzing the flue gases after combustion and then after treatment. The result is used to adjust the addition of reagents used in the processes.
The increasing use of waste incineration frequently raises concerns about air pollution, especially in the local community. However, this article shows that with the use of modern instruments, emissions to air can be effectively controlled and documented.
ABB has extensive expertise in the design, manufacture, supply and maintenance of instrumentation and monitoring equipment for waste incineration. For advice on the best solution for your application, please call 0870 600 6122 or email [email protected] ref: âwaste incinerationâ.