Energy From Waste
Energy from Waste (EfW) facilities are seen as the most beneficial option for dealing with the UK’s waste problem (due to the extensive growth in population and subsequent waste generation). Not only does energy recovery provide a purpose for the once valueless waste sent to landfills, but it also provides a dependable source of renewable energy.
Due to the harmful gases that waste incineration produces, these plants are governed by strict environmental regulations. All waste burning plants, including small waste incineration plants, must meet the stringent emissions limit set by the Industrial Emissions Directive (2010/75/EU)
Waste Delivery & Storage
The waste delivery areas are otherwise known as the waste tip bunker. Refuse trucks dump the waste and it is stored until the grabber crane moves the waste into the furnace. Within this area, there are many different types of waste materials accumulating which poses several dangers. Not only does it smell bad, there is a huge danger of the build-up of hazardous gases which are dangerous to people but also increases the risk of damage to the site.
In biomass sites, this area is also used to store the wood pellets used to fuel the incinerator. Wood dust is one of the major causes of fires within the biomass industry. It is a problem where there are large quantities of material stored in a single silo or pile, and where material is damp.
Hazardous Gas Safety
Within the waste delivery and storage areas fixed gas detectors are permanently installed to continuously monitor the risk of oxygen depletion, Carbon Monoxide (CO) and combustible gases. Throughout the gasification process, whilst patrolling the site, EC&I technicians should be armed with personal single CO monitors to continuously detect the threat of the silent killer.
Mitigate Fire Risk
The burning of an unconfined wood dust cloud has the potential to produce a flash fire. However, if the wood dust is contained within a full or partial enclosure, the pressure build-up can produce an explosion. Friction sparks can cause fires or explosions. For wood chip and wood pellet biomass storage and transport, wood dust is prone to self-heating and is explosive, establishing the need for flame detection.
During the transport of powders and wood chips, fine particles become airborne. Respirators are worn by workers to protect against inhaling dangerous substances such as dust or particulates, and gas and vapours, or any combination of these thus protecting the respiratory tract. For short-term use, a half-face mask is suitable to protect against various airborne hazards. For protection over the course of several hours, a powered air respirator should be worn.
Waste recycling in incineration plants starts with the delivery and incineration of waste. The waste reaches the combustion chamber via a falling chute, which is followed by a hydraulic feed device. To guarantee a constant incineration process, the falling chute must be filled constantly.
Point Level Detection
The “high“ and “low“ limit values should be detected and alarmed. The plant operator looks for a device that measures the point level completely over the whole cross-section. To control the filling level, a limit level monitor measures limit levels in a falling chute. The detection of the limit levels guarantees a constant filling of the combustion grate and thereby a continuous firing.
Material Flow Measurement
In most combustion type processes with high-temperature conditions, atmospheric nitrogen reacts with oxygen to produce Nitrogen Oxides (NOX) which are highly dangerous when emitted to the atmosphere. Therefore, these gases need to be cleaned.
Sites will need to evaluate their SCR or SNCR methods to effectively regulate NOX emissions by injecting either an ammonia (NH3), coke or lime reagent directly into the process.
These materials are stored in silos. Via a rotary valve, the materials are blown from storage into a conveying air flow and thereby reach the exhaust gas stream which they clean.
Mass Flow Measurement
Flow monitors are perfectly suited for industrial applications especially in power generation or incineration plants where they can be used to regulate or control the desired volume of reagent in flue gas treatment.
The control of reagent, of course means that sites can avoid pouring in unneeded reagent into the process in a bid to control costs. Flow monitors measure the amount of reagent dosed by a screw conveyor and regulates its speed control. Flow monitors continuously monitors the flow volume of reagent to determine whether the rotary valve (used for material dosing) has become clogged. If flow is reduced, this would cause interruption to the process.
If the flow monitor transmits a problem to the plant control room, it can be assumed, that the internal of the rotary feeder requires cleaning.
Material Flow Measurement
Cyclones are used to separate solids from the gas flow, for example after scrubbers. At the cyclone outlet, the flow monitors signals the status of flow or no flow. A non-existent material flow after the valve indicates a blockage in the cyclone. In the case of a material flow interruption, it is now possible to detect quickly whether there is a problem because the lower screw no longer removes any material, or the feed screw no longer supplies material.
Reagents for the flue gas cleaning such as hydrated lime or activated carbon are stored in silos. These bulk chemicals are delivered to the process by feeding into a pneumatic blow line. For optimum process control, reliable level measurement is essential to ensure that adequate quantities of reagent are made available.
Extreme dust generation and material build-up are the main challenges.
That is why an advanced and reliable contactless level sensor complies with the requirements in this application.
In many bulk material processes, storage silos, process containers, pipelines, ducts or free-fall sections, limit levels inside a storage tank need to be monitored to prevent overflowing. To prevent the silos from overflowing, continuous level measurement is necessary. With its measuring range of 120 metres, radar sensors have been designed to continuously measure the level of materials in storage vessels. The Nico 120 can be used on a wide range of different materials having varying particle sizes and compositions. The measurement is unaffected by dusty atmospheres, obstructions, or temperature variations.
Continuous monitoring of the flue gases on a boiler or burner makes economical sense as well as ecological.
- Reduces the long-term impact of the CO corrosion. Poor combustion can produce corrosive compounds on the boiler wall and ash deposits in the boiler.
- Continuously measuring O2 and CO allows for immediate adjustment of the air injection and better control of feeders, which optimises the efficiency of the combustion process.
Raw Gas Measurement
When waste is incinerated, high volumes of pollutants are released which threaten the environment. Control of stack emissions is no longer enough to ensure compliance with regulatory ELVs.
Raw gas measurement optimises the process by recording the level of pollutants in the gas stream to better control abatement.
During abatement, Ammonia (for NOx) and lime reagent (for HCl) is injected into the scrubber to control emissions. Activated carbon is also injected to adsorb total organic carbons and heavy metals.
With known quantities, raw gas analysers can help control how much absorbent is needed to neutralise raw gas concentrations.
To achieve compliance with NOx emission limits the application of ammonia or derivatives of ammonia (e. g. urea) as a reduction agent has proved successful. The nitrogen oxides in the flue-gas basically consist of NO and NO2 and are reduced to N2 and water vapour by the reduction agent. Two processes are important for the removal of nitrogen from flue-gases – selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). In both these systems, the flow rate and control of NH3 must be continuously adjusted and controlled to prevent excess NH3 emissions (slip), to reduce environmental impact and cost of reagents. To optimize this process, it is essential to use an analysis system for simultaneous and continuous monitoring of NH3 and/or NOx.
For SCR, the use of the NDIR heated and extractive multi-gas analyser, offering the capability of measuring the NH3+H2O or NH3+NOx+H2O in parallel is recommended. For information, the same analyser can measure additionally other parameters such as H2O, CO and O2. If sole the measurement of NH3 is to be made, the use of the Cross Stack TDL sensor offers real time monitoring.
Baghouse Performance Monitoring
Multi-chamber bag filters are becoming increasingly common to effectively contain and measure particulates. The baghouse is equipped with hundreds of filter bags.
Broken Bag Detection Failure
A basic dust filter detects significant increases in particulate loading providing advanced warnings of filter media degradation in baghouses. The dust filter can achieve both cost savings in terms of reduced baghouse maintenance and lost production and in addition achieve reductions in emissions to atmosphere.
Broken Bag Leak Filter
The dust leak alert filter is particularly suited for use on fabric filter baghouses. It provides reliable and robust monitoring of particulate dust levels and leaks from faulty bag media where performance approvals are not required.
Predictive Bag Filter Row Monitoring
Over time, filter bags will burst, and it is important to identify and replace the defective bag as quickly as possible. A dust leak locate filter is a valuable filter-maintenance tool giving advance warning of filter deterioration before catastrophic failure enabling users to make significant savings in spares, maintenance time and lost production time.
Flow Detection at Ash Transportation
Ash transportation in most cases is done by air slide systems. It is essential to ensure material flow inside the transportation system. Any plugging or interruption in the material flow must be avoided. A flow monitor will detect the flow of ash contactless via a microwave beam hitting the material flow and defining Flow or NoFlow condition. The flow monitor can be retrofitted from the top of the upper conveying chamber avoiding shutdown due to plugged filter outlets.
Ash Level Detection
The dust particles which pass through the bag filter are collected on the surface of the bag filter. The fly ash is shaken off and falls into the collection hopper. To determine whether the hopper is full, point level measurements are taken.
Managing Ash Residue with Moisture Measurement
The install of continuous online moisture measurement has multiple benefits for Energy from Waste plants. There are savings in transportation of ash due to weight of excess moisture, to savings in water usage for dust suppression. EFW plants also use moisture measurement to reduce the risk of dust and ash build up which prevents blockages on the conveyor, which would otherwise result in shutting down the boiler.
Flue Gas Emissions
Continuous Emission Monitoring Systems (CEMS) consist of gas and particulate analysers, temperature, flow, and opacity monitors that are integrated with a data acquisition system to ensure full environmental regulatory compliance of the Industrial Emissions Directive (2010/75/EU).
Quality data from emissions monitoring technology can provide valuable feedback on abatement plant performance. This enables greater efficiency and control over plant operation helping sites to achieve compliance.
The Heated Fourier Transform Infra-Red technology is designed for measurements of hot, wet, and soluble sample gases. It is the most popular MCERTS certified CEM with the capabilities of continuously measuring up to 14 gases including Ammonia.
The Infra-Red Gas Filter Correlation based technology monitoring system measures up to 10 gases simultaneously. It is designed to measure corrosive samples on a dry basis measurement.
Particulate measurement systems are generally used to monitor emissions to the atmosphere, but if specified with the necessary features and implemented correctly, they can be deployed as valuable condition monitoring and preventative maintenance planning systems. This facilitates both the extension of service life for bag filter elements, and a significant reduction in reactive maintenance interventions and therefore process down times.
Flue Gas Velocity & Flow Monitoring
Flow monitors measure flue gas velocity, temperature, and pressure within the flue. They are designed to work in elevated temperatures and applications with high dust loadings. Our accredited flue gas cems facilitate stack velocity, volumetric flow and pollutant mass release calculations when linked to gas and dust CEMS.
Featured Case Studies
Our solutions satisfy applications from small facilities up to large multi-site facilities and everything in between.
Explore some of our featured case studies for more information or chat to an expert.
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Broken Bag Detectors Continuously Monitor for Dust Filter Damage
According to the client, the Dusty offers the following advantages:
More cost-effective than comparable products
Continuous filter damage monitoring
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