Know More About Electrostatic Precipitators And Its Control Techniques

The easiest way to remove particles from a gas stream is by using an electrostatic precipitator. Electrical energy is used to charge those particles negatively or positively before they get attracted by the collector plates which are generally of the opposite charge. The collected particles become dry in the collector plates and can be easily removed or washed with water. Not everyone using the procedure is aware of the fact that the collection efficiency of ESPs is more than 99 percent and this is why they are widely used in various industries.

Its Various Components

The four common components you will generally find in an electrical precipitator are discharge electrodes, rappers, collection surfaces and gas distribution plates. These plates comprise of numerous plates which are perforated to maintain and properly distribute the air entering the gas stream.

The discharge electrodes in a majority of the ESPs are divided into 3 or 4 fields. The larger electrodes are divided into around 14 fields which are generally found in series. A solo transformer-rectified set power supply is sufficient to energise those electrodes and create ions. The ions dashes with the particles in the incoming gas stream and applies an electrical charge. The charged particulate matter then collects on the plates or pipes which can be later removed using the rapping system.

Types Of Electrostatic Precipitators

There are generally two types of ESPs, namely dry ESPs and wet ESPs. What differentiates these two is the method through which the plates where the particles collect are cleaned. Vibrations or mechanical impulses are used to loosen the collected particulate matter and clean the dry ESPs from the collection plate. To remove wet ESPs, you have to rinse the collector plate thoroughly using water. Using this wet method becomes necessary when the particles accumulated in the gas streams are sticky and have low resistivity.

ESP Performance And Particle Resistance

For someone not aware of the term, ‘particle resistivity’ is basically the property of the particles that can influence the process through which they deposit or is removed from the collection plates. This is why resistivity of the particles can affect the performance of Electrostatic Precipitators drastically. Moderate resistivity is regarded to be the ideal situation when the particles can automatically accomplish some of their charges after reaching the collection plate. This prevents the inhibition of other deposited particles and makes them capable of retaining their charge while holding them lightly on the plate.

It takes longer for the particles to conduct away their charge if the resistivity of the particles is higher. As a result, a negative charge builds up on the plate which inhibits the other deposits. If the resistivity is too low, the particles will start losing their own charge once they reach the collection plate and start attracting charges from the plate. This will make the negatively charged particles deter back into the gas stream.

Since your knowledge about electrostatic precipitators has enhanced, it’s time you start looking for a reliable company who can take care of all your ESPs needs.


Electrostatic Precipitators: Way to Kill Industrial Flue Gas

industrial air pollution

Okay, ‘electrostatic precipitator’ is way too technical. Let’s call these machines the scrubbers. They are inherently static-electricity filters, designed to steal dust, soot, ash, and grime from industrial smoke. It goes without asking that they contribute to the minimisation of air pollution. Yes, they are a technological marvel.

Want To Know How A Scrubber Works?

Comb your hair vigorously on a cold, dry day, You’ll notice that the strands cling on to the teeth of the comb. Well, that’s static electricity.

ESPAs the comb rubs against your tresses repeatedly, the electrons break free from them and settle on it instead. At this point of time, your hair is positively charged and the comb negatively. This explains the weird attraction.

Something of the like happens in a scrubber as well. Industrial smoke is actually an aerosol. It may look like gas, but the properties are different. That’s solid suspended in a gaseous medium. The suspended particles are unburned carbon.

The idea is to ‘rub’ the particles so that they receive an electrical charge. These when passes through a medium with the opposite charge, can be pulled out and removed.

Simple, right? Wrong.

There’s more.

Industrial smoke, aka flue gas, is forced through two electrodes inside a smokestack. The negative electrode imparts negative electrical charge to the suspended particles. The second electrode is the positive one and located up or beyond the negative electrode. They attract the charged particles.

Until this point, it is more or less similar to the hair strands attaching to the comb. However, the challenge is to get rid of the pulled particles from the electrode, which is also known as the collector plate.

It needs to be shaken from time to time so that the older particles are emptied and there’s room for newer particles. This can be done manually by brushing or, automatically using an automated shaker or rapper, after which, the particles are disposed of.

ESP at a industry

What Are The Typical Activities Of A Scrubber?

If we go by the above explanation of how a scrubber works, here are the six typical activities that take place inside it:

1. Ionisation – The particles are charged.
2. Migration – The particles are taken to the collector plate.
3. Collection – The particles are collected onto the collector plate.
4. Neutralisation – The particles are neutralised on the collector plate so that they fall.
5. Dislodging – The particles are dislodged onto a hopper.
6. Removal – The particles are carried from the hopper for disposal or recycling.

Which Particulate Properties Affect Electrostatic Precipitators?

Various electrostatic precipitators are designed for particles of various sizes, chemical compositions, and amounts. Here are the two most important aspects of suspended particles that normally affect these scrubbers:

• Electrical resistivity
• Particle size distribution

Other aspects include:

• Temperature of the flue gas
• Its moisture content
• Overall design of the machine
• Whether the rapper is manual or automated
• Whether single-stage or multi-stage scrubbing
• Whether the removed particles should be disposed of or recycled.
• Heterogeneity of the pollutants that the flue gas contains

So, now that you know the scrubber inside out and the loads of environmental benefits it brings, why not have it installed in your industrial plant as well? Like they say, let the machine take care of the machine while we enjoy a good life.