A limited amount of waste is stored near the incinerator to prevent any fire hazard. Solid waste is always stored in drums or other containers and fed through an automatic ram loading system. Odd sized material is fed manually through a door. As the system always operates under negative pressure, atmospheric air is pulled in every time feed doors are opened, there is no leakage from these doors.
Liquid wastes are unloaded into a liquid waste storage tank from where they are pumped directly to the incinerator. Some oil sludges are loaded into a separate tank where they are heated to increase their viscosity and then fed in to the primary chamber. Other semi-solid material is fed through a hopper which controls the feed rate.
Haat's high efficiency system consists of 2 static hearth primary chambers with combustion air nozzles placed at relevant locations to enable air to permeate throughout the wastes and increase the DRE of organics. Having 2 primaries enables us to cater to variations in waste material, size, deashing cycles, lower waste generation days, etc. without having to switch the system off. Both the primary chambers are connected to a common secondary which is sized for a flue gas residence time of more than 2 seconds at temperatures in excess of 1050 deg C. All volatiles are completely incinerated particularly with the turbulence created in the secondary chamber.
Flue gases from the secondary chamber enter a large gas cooler where they are cooled by atomised water which brings the temperature down to around 200 deg C. The water sprayed here is completely evaporated and the cooled gas enters 2 bag houses placed in parallel. The bag filter system eliminates 99% of particulates and is provided with automatic pulsing so dust is shaken off and collected in enclosed drums at its base. The next stage is to eliminate acidic gases which takes place in a scrubber that is recirculated with caustic solution. A mist eliminator removes water from the flue gas which is now at around 80 deg C. An ID fan provides the necessary draught to pull the gases through the system and out through a 30-m rubber lined stack.
All of Haat's vast experience in the incineration line, lessons learned from the field, hazop studies, aspect / impact studies and feedback from various quarters have all formed inputs into the design of the control system that runs the entire plant. Instruments for key parameters are in place including redundancy where required and control philosophies with interlock schedules and cause and effect diagrams have been developed. The entire system is operated by a PLC with a HMI that provides information on the process, alarms, set points, etc. All the operator has to do is load waste and remove the ash. Human error leading to untoward situations is completely eliminated.
Haat uses a high end German make continuous emission monitoring system for some key pollutants which are interlocked to waste feed and are connected 24/7 to the CPCB. There are many types of emission monitoring systems available such as electro-chemical ones which are cheap but unreliable. Haat's system ensures accurate recording of values.
After the incineration process, solid ash is produced which is collected in drums, cooled and then disposed of only to the authorised secured landfill. The air emissions are clean and barely visible at the top of the stack. Liquids from the acid gas scrubber are constantly bled to the gas cooler preventing a salt concentration build up. The residual solids are collected by the bag filter and Haat's system is a zero water discharge plant without the requirement of a water treatment system due to this.
