Is Your Money Just Going Up In Smoke?

Phil Black - PII Editor 30/03/2021

288 4 minutes read

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Power plants, cement plants, steel plants, smelters, asphalt plants, incinerators, food manufacturers, chemical producers, pharmaceutical producers, and other industrial companies are widely using bag filters to control Dust Emission. On some applications bag filters are also used to capture other product coming out of mills, for example, cement, coal, and other raw materials.

Fabric filters, without doubt, are an extremely efficient pollution control device with the ability to capture 99% plus of dust collected from process gas but with one drawback, they are prone to leaks.

Most fabric dust collectors clean their filter bags by injecting a short blast of compressed air down a single row of bags. This is repeated until every row of bags is cleaned or until the desired level of differential pressure is achieved. The cleaning sequence is usually by a timer or differential pressure gauge. When the air has stopped and the dust ‘cake’ removed, the bag becomes momentarily porous and particles rush through the open pores until dust gradually reseals the bag.

This event is seen by the sensor as a ‘spike’ 3 to 4 times higher than the normal dust level. However, if a particular filter bag becomes torn, the spike detected from that row becomes much higher. The row containing the leaking filter bag is found by counting the number of spikes from the beginning of the cleaning sequence.

Before You Can manage, You Have To Measure

Tribo-electric dust monitors will monitor the dust collector as the efficiency drops. By setting the damping to a low value, say 20 seconds, ‘rapping’ events are identified. This will show how much dust is being emitted during ‘rapping’. If the amount of dust is especially low for a particular field, then it follows that it is ineffective and may require attention.

It is important to set the instrument damping to less than 20 seconds. If a longer time is set, the spikes become integrated over a longer period and it becomes much harder to pick out leaking filter bags. On some types of filter bags, it may take up to 20 seconds for the bags to reseal.

Ongoing performance can easily be achieved by periodic filter bag replacement, as well as filter inspection and monitoring. The optimum timing for a filter bag replacement is one that maximizes the length of a bags use, and one that takes place before a significant leak event occurs which could then result in exceeding emission limits and in turn causing the process to stop.

An accurate prediction for bag replacement can be achieved with the aid of a continuous leak detection system. The advantage of this being that the replacement or maintenance of a bag filter can be routinely planned rather than having to stop a process because of the immediate necessity to replace a filter bag, a very costly unplanned plant shutdown!

Optimise Your Dust Collector Performance!

Can you afford an unplanned shutdown? What does it really cost?

A continuous leak detection system results in significant cost-savings particularly when capturing product.

CODEL’s ET301 Triboelectric Sensor, has been successfully applied to a number of bag filter leak detection applications. One example is of six ET 301’s installed on 6 modules of semi-dry NID^TMFGD. Each module consists of an FGD reactor and fabric filter, as a final pollution control device. Outlet ducts from the six FGD modules merge into one duct before entering the stack.

CODEL ET301 sensors are fitted on the outlet from each module, allowing independent monitoring of the bag filters, enabling operators to schedule maintenance more effectively and isolate leaking bags without stopping the plant. This helps to prevent excess emissions and improve process whilst using reliable, accurate and low-cost particulate monitoring.

ET 301 installed on the semi-dry NIDTM FGD module

So, let us take a closer look at the main features of the ET 301 leak detection sensor:

Capable of detecting the smallest levels of dust, below 0.1mg/m³
Capable of detecting particulates in a size range of 0.1 to 100µm
Fast response time
Early warning of bag leak detection.
Easy networking for multi compartments and modular arrangements. RS 485 MODBUS and 4-20A output.
Real-time measurement of filtration systems with optional remote condition monitoring for trend analysis, text notification and report generation.
Minimum maintenance requirement
Simple installation, no alignment required.
No optical surfaces, purge air not required.
No interference with other measurements

These features translate into multiple benefits for the customer; not only in contributing to gaining operating permits through real-time monitoring in mg/m3 but also in the prevention of loss of product on some applications. On multi-compartment bag filters CODEL’s modular arrangement allows for the leaking part of the bag house or leaking module to be identified.

These benefits enable a reduction in the visual inspection of the filter frequency, improved quality and reduced spoilage which in turn reduces maintenance inspections and extends filter life.

Importantly, these all contribute to the reduction of potential risk to the environment and personnel as well as meeting EPS/OSHA regulations.

There are also additional benefits of knowing when to change the filters at the most efficient and economical time, based on running costs, as well as protection of the dust collector and its blower and the highlighting of any failed valves on the dust collector.

Benefits That Deliver Significant Savings in Running Costs!

In summary, the EnergyTech 301 is a low-cost dust monitor using well proven tribo electric technology providing accurate and rapid results. Importantly, it requires no critical alignment and has no-optical surfaces to keep clean. The sensor is easy to install, requiring only a simple probe which makes it ideal for small duct sizes and comes with a 2-year warranty for complete peace of mind.

Here at CODEL we treat each measurement location as a unique installation and offer professional advice on which technique suits your needs and which model analyser is best suited to the task.

If you would like more information, please contact sales@codel.co.uk.

www.codel.co.uk