incinerator

INTRODUCTION

Today the toughest challenge to any industry is to avoid pollution / reduce pollution. For any industry waste / effluent generation, although not desired, happens automatically. So the challenge to industry is to develop efficient systems of waste disposal to satisfy pollution norms.

Incineration is the process of complete burning and destroying the hazardous materials into non-hazardous constituents. For every chemical there is a definite time temperature relationship for its complete destruction. For majority of materials at temperature of 1000° C the incineration process completes within fraction of second.

A Fluidised sand bed gives the necessary residence time, increases the heat transfer coefficient, & provides thermal inertia to take care of variations in physical properties of waste sludge.

This system is successfully used for waste either in the form of liquid waste, waste containing high molten salt, sludge containing high water content & solids.

In our Fluidised Bed Incinerator incineration process is achieved in two stages.

Burning of materials and generating volatile gases in sand fluid bed.

Destroying these volatile gases in after burner. This ensures that NOx quantity is at lower level.

Incinerators are installed to protect the environment. Industries consider it to be liability and hence running cost should be kept as low as possible. In addition to the above complete incineration following makes our Fluidised bed incinerator unique.

Utilization of energy in exhaust gases as follows-

To heat the incoming air of the incineration system.

Remaining energy can be used elsewhere in the plant in the form of hot water/steam/hot thermic fluid.

This makes our Fluidised bed incinerator the most energy efficient.

If the waste sludge/solids has calorific value, heat is generated in Fluidised bed chamber. This reduces the fuel consumption in After burner reducing the running cost of the system.

WORKING PRINCIPLE OF INCINERATOR

See Figure No.1

Figure 1 depicts working of an Incinerator.

F. D. Fan supplies air at high pressure for fluidization of sand.

Air is heated to desired temperature and supplied to Fluidised chamber where sand is Fluidised.

To initially heat the sand fast from cold condition, Start-up burner is provided. Once the temperature of sand is reached, the burner cuts off.

The sand temperature is maintained constant.

In running condition Air Preheater will heat the air to desired temperature maintaining the temperature of sand.

The material (liquid/solid) will be fed in the chamber where it will get burned.

The hot air and gases passes through cyclone where solid particles & ash will get separated.

The gases pass through after burner where the volatiles are incinerated & destroyed completely meeting the environment rules.

The temperature of gases after ‘After Burner’ is very high (typically 1000° C or more). To recover the heat from these gases Air-Preheater is installed. Heat is transferred from flue gases to process air.

The gas coming out of air-Preheater is still at high temperature. Further heat is recovered from gas in heat exchanger to generate hot water/steam etc.

Venturi type scrubber is provided to arrest solid particulate matter from the flue gases. After scrubbing, the gas is suitable for exhaust to atmosphere.

I.D. Fan sucks the flue gas and exhausts it to atmosphere through chimney / exhaust duct.

MAIN COMPONENTS OF INCINERATOR

1. F. D. Fan.

This gives necessary air for fluidization and combustion of fuel of Start-up & After burner.

This is a Roots blower and ensures constant airflow rate irrespective of system pressure.
Tolerances between rotors, as well as rotors and stator are very close to achieve better efficiency.
Inverter is provided to change the speed of blower motor thereby controlling the airflow rate.

2. Heat Recovery Air Preheater

See Figure No. 2

Air Preheater is used to utilize the heat available in incinerated gas. The gas transfer heat to process air going to Fluidised bed chamber increasing its temperature. This saves fuel consumption and reduces the operating cost of the system.

This is a shell & tube type heat exchanger of Stainless Steel construction to withstand high temperature.
This saves lot of fuel, which would have been required otherwise.
Expansion bellow is provided on the shell to take care of stresses due to high temperature avoiding cracks.
Self-cleaning action prevents deposition of solid material on tubes.
Both ends are kept flanged for easy access of tubes.

3. START-UP BURNER.

See Figure No. 3

In running condition air coming from heat exchanger itself keeps the fluid bed at desired working temperature. When we start the system the heat exchanger air is also of low temperature and leads to high startup time. This burner provides the air of 800° C directly which heats up the sand bed very fast.

Once the desired temperature is achieved this burner gets OFF automatically and permanently.

High Alumina Refractory is provided at the burner and fluid bed joint to withstand high temperature.
Specially designed fuel oil filter eliminates frequent cleaning of burner nozzle even on heavy oil operation. Heating pumping unit is provided with stand-by filter and stand-by feed pumps reducing the down time of system.
Furnace and diffuser plate is of AISI 310 giving long life.
Internal damper is provided for burner air adjustment.
Easy operation and maintenance of burner.
Expansion bellow is provided on outer shell to take care of thermal expansion giving long life.

4. Fluidised BED CHAMBER

Sand is Fluidised in this chamber by hot air. The material to be incinerated is fed in this chamber.

See Figure No.4

It consists of

AISI 310 bedplate and nozzles (refer figure 5).
Sidewall of AISI 304.
Sand bed of –20 to +40 mesh size.
Outlets to drain the sand.
Material feeding system consisting of:

Screw conveyor for solid material (refer figure 6).
Pump for liquid material (refer figure 7).

Following is essential for proper design of fluid bed chamber:

SS nozzles used instead of ceramic tile bed for following reasons:

Porosity in tile is not uniform. Hence makes the airflow non-uniform.
Joints need to be cemented together which lead to thermal cracking with time.
This leads to channellization of air and hampers the fluidization.
Requires frequent replacement and maintenance of tiles.
It is very easy to obtain vigorous fluidization. However to obtain optimum level of fluidization following need to be critically designed.
Airflow required.
Pressure drop across the fluidizing plenum.
Number of nozzles and nozzle pitch.
Diameter of nozzle.
Number and diameter of holes on the nozzle.

5. CYCLONE

Cyclone is used to separate ash & solid particles from gases. Kettles and butterfly valves are provided at cyclone outlet that collect separated particles.

Optimally sized for the desired airflow.
Low-pressure drop across inlet and outlet.
Settling vessel is provided for better separating efficiencies.

6. AFTER BURNER TO DESTROY VOCs

See Figure No.8

VOCs (volatile organic compounds) from Fluidised bed chamber get burned in the after burner.
Sufficient residence time is provided for completely burning & destroying the VOCs.
Furnace as well as outer shell is of AISI 310.
Specially designed fuel oil filter eliminates frequent cleaning of burner nozzle even on heavy oil operation. Heating pumping unit is provided with stand-by filter and stand-by feed pumps.
Continuous modulation linked with after burner temperature is provided to control the fuel flow rate.
Furnace and diffuser plate is of AISI 310.
Internal damper is provided for burner air adjustment.
Easy operation and maintenance of burner.
Expansion bellow is provided on outer shell.

7. HEAT RECOVERY HEAT EXCHANGER
See Figure No. 9

Flue gases heat the incoming fresh air in the Air Preheater.

Still the gases have lot of heat that can be recovered.

The heat can be recovered to get hot air, hot water, hot thermic fluid etc. as per the requirement.

This has shell and tube types construction and can be of carbon steel.

This saves lot of fuel that would have been required otherwise.

Self-cleaning action prevents deposition of solid material on tubes.

Both ends are kept flanged for easy access of tubes.

8. SCRUBBER SYSTEM

Scrubber is used to remove the solid particles from exhaust flue gases. This broadly consists of:

Water tank
Water pump
Spray nozzle and piping
Venturi.
Scrubber cyclone.
Water filter system.

System is made automatic as per P & I diagram enclosed (Refer figure 10). Water is pumped and sprayed through a nozzle to a solid cone of spray that covers the throat of venturi completely. Thus entire gas is washed by the spray and wets the suspended particles entrained in the gas. These wetted particles become heavier and get separated in the cyclone, letting clean gas go to chimney through ID FAN.

System is optimally designed for the followings-

Airflow rate.
Water flow rate.
Spray nozzle.

If the material to be incinerated produces hazardous gases that cannot be incinerated viz. SO₂, HCl etc. appropriate scrubbing system is provided. For more details on removal of SO₂, please refer to "Flue Gas Desulphurization Scrubber System".

9. I.D. FAN

It is used to extract the gases from the system to exhaust stack. F. D. Fan and I. D. Fan operate in push pull principle.

Salient Features:

Designed for the required duty point.
High efficiency – upto 80%.
Tested for performance.
Tested for vibrations as per IS 1940.
Tested for rise in bearing temperature.
The bearing block is single piece machined component – alignment & rigidity.
Drain plug for condensate removal.
Access door for inspection/cleaning.
Damper at outlet to control airflow rate.
Manometer tapping at inlet & outlet.
Direct driven & belt driven construction.
Guard at air inlet & belt – safe installation.
Rigid base frame and supports – vibration free performance.

10. CONTROL PANEL/ INSTRUMENTATION.

The plant is fully automatic with various safety interlocks –

Automatic temperature control for fluidizing sand.

Automatic firing of burners with flame monitoring and safety trip control.

The temperature of gases in After Burner is monitored for complete incineration of gases.

Switchgears & fuses for motors.

Digital temperature indicators and controllers at various locations for proper monitoring.

Manometers are provided for monitoring air pressure at various locations.

EXCLUSIVE FEATURES

Unit has after burner to incinerate the organic vapors / gases generated during the burning operation.

The unit has two heat recovery units so that energy efficiency is at it’s best.

In the after burner organic vapors get completely decomposed destroying their toxicity.

The entire plant is insulated that ensures heat losses are bare minimum.

The unit is provided with cyclone separator for grit arrest after Fluidised Bed Chamber.

Fluidised bed distributor plate is made of AISI 310. There are no ceramic tiles that frequently break or clog.

Entire unit is made of Stainless Steel hence long life.

Entire plant is factory assembled and tested.

The entire plant is mounted on chassis for ease in transportation.

Expansion bellows are provided at various places to take care of thermal expansions.

Plant is fully automatic with appropriate safety interlocks.

Wet scrubber is provided to remove ash from the gases before they are exhausted to the atmosphere.

HOW OUR INCINERATORS ARE HIGHLY ENERGY EFFICIENT

Incineration is a high temperature process and lot of energy is generated. If the material being incinerated has high calorific value viz. waste oil, organic matter, its burning liberates additional energy. This energy if not recovered will go as waste.

Incinerators are installed to protect the environment. Industries consider it to be liability and hence running cost should be kept as low as possible.

We incorporate heat recovery system to recover the heat as much as possible that compensates partially for the fuel spent. Following is incorporated in our system to recover the heat from flue gases-

Air Preheater: The gas leaving from ‘after burner’ is at very high temperature @ 1000° C. In this unit heat is transferred from hot flue gas to incoming fresh air. The fresh air gets heated to almost 500° C recovering about 50% of the heat.
Heat exchanger: The gas leaving from air Preheater is still at high temperature. Hot gas transfer heat in heat exchanger to get hot water / hot thermic fluid / steam as per requirement.

ESTIMATED SAVINGS AS COMPARED TO OTHER MAKE INCINERATOR

We compare ours & other make Fluidised Bed Incinerator having Fluid bed chamber holding 2.6 m³ sand. The sand bed is maintained at 500° C and volatiles are incinerated at 1000° C.

Sr.	Description	Transparent Incinerator	Other make Incinerator
	HSD consumption	37.5 lph	67.5 lph
	HSD saved with second heat exchanger	19.5 lph	-
	Effective HSD consumption	18 lph	67.5 lph
	Savings in HSD	49.5 lph	-
	Savings (HSD – 19 Rs/l)	940.5 Rs./hr	-
	Annual savings (7200 hrs)	67,71,600 Rs.	-

APPLICATIONS

One of the uses of incinerator is as PAINT STRIPPING EQUIPMENT.

Industrial sludge.

Chemical effluents.

Distillery effluents.

Destruction of biological waste.

Burning of inorganic and organic wastes.