We have written earlier on the subject of incinerator as a system and would like to dwell a little more on this subject here.

First of all, it is not a contraption which simply burns whatever is thrown inside. It is a complex mechanism with mechanical, electrical, instrumentation and combustion engineering aspects of design, construction and performance.

Take for example a hazardous waste incinerator system. What does it consist of?  A well designed system meeting the current rules and guidelines and conforming to emissions which are equal to and comply with the standards, should have the following configuration:

•                 Primary combustion chamber

•                 Secondary combustion chamber

•                 Auto loader

•                 Liquid waste feeding system

•                 Combustion air fan

•                 Gas cooler

•                 Bag filter

•                 Acid gas scrubber

•                 Mist eliminator

•                 Induced draft fan

•                 Stack

•                 PLC control panel

•                 Piping and Instrumentation

•                 Continuous emission monitoring system

The thermal value of the system should be calculated accurately taking into account the characteristics of the waste it is going to handle, providing enough breathing space in the primary chamber and a decent residence time in the secondary.

The refractory used should be such that it does not give problems of premature failure and should withstand high temperature with no structural damage.

The ram loader, which can be hydraulic or pneumatic, should be designed such that the operator is not exposed to heat and the waste that is charged is positively fed into the chamber without any hiccups.

Liquid waste feeding is an option with its own plethora of piping, nozzles and atomizing air.

While the temperature in the combustion chambers may be in the region of 800 – 1100°C, the gas cooler should be designed to bring it down to around 200°C to make the flue gas acceptable to the gas cooler. Initial scrubbing for particulates and acidic gases takes place here.

The bag filter should have a little more than 99% collection efficiency particularly for sub-micron particles.

The flue gas exiting the gas cooler should get scrubbed for NOx and SOx once again, thus leaving clean flue gas to be pulled into the stack by the ID fan safely to the atmosphere without any visible smoke.

The ID fan is generally provided with a Variable Frequency Drive to enable automatic adjustment of the RPM, depending on the flow rate of the flue gas.

The PLC control panel incorporates many features including operation in `auto` mode, `maintenance` mode and `manual mode` as chosen by the operator. It has an HMI which makes it easy for the operator to choose the control philosophy and run the system with least manual intervention.

A Continuous Emission Monitoring System provides data on various pollutant values and can be connected to regulatory bodies.

The entire incinerator system should have good and reliable instruments such as pressure transmitters, flow transmitters, level transmitters, temperature transmitters, etc. It is essential to choose quality instruments because running the system satisfactorily over a period of time is dependent on this.

Such a well-designed incinerator system should last between 10 to 15 years easily and even more!

If you wish to see an incinerator system running for more than 15 years, please visit our Common Hazwaste Incinerator Facility in Bangalore and satisfy yourself.