All Types of Waste Incinerators

8/3/2019 All Types of Waste Incinerators

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Moving grate incinerator

The moving grate incinerator is used for non-homegenous and low calorific waste. The domestic wasteincinerator is offen called a "Waste-to-Energy" plant, WtE plant or "Energy from Waste" plant. The gate feeprice of the household waste is app.120 - 125 euro/ton and a household waste incinerator of app. 14 ton/hhas an investment price of +/- 90.milj.euro.

The biggest grate is capable of incinerating the design throughput of waste (31,25 tons/h) with the highest

calorific value (2 200 kcal/kg). In normal practice, a household waste incinerator is capable of operating8000 hours per year (in full continuous regime). The installation must comply with the regulationsregarding:

y Environmental protection requirements on the base of the current EU legislation (emissions, odours,noise,...)

y Fire fighting standardsy Safety at work and labour protection rules

The grate need to be cooled because the air is added from the bottom and high temperatures can damagethe grate. Two different types of grate cooling systems exist: the air cooled grate and the water cooledgrate.

Generaly, depends on domestic waste collection and recycling system, if the waste has:

y 6 - 10 MJkg --> Air cooled gratey 8 - 15 MJ/kg --> Partly watercooled gratey 12 MJ/kg and more --> Watercooled grate

The conversion of waste to energy requires an effective control of a complex series of physic - chemicalprocesses, commonly known as combustion. We can distinguish two groups of processes, a horizontalgroup and a vertical group.

1. Horizontal: the conversion of the waste (a heterogeneous mixture of all kinds of solids and liquids)to gases.

2. Vertical: de oxidation of these gases resulting in complete combustion.Each of these groups can be further sub-divided into sub-processes

Horizontal

1. Drying: this is the evaporation of the water present in the waste;2. Outgassing: here volatile compounds in the waste escape as a result of heating up the waste;3. Degassing/pyrolysis: in this sub-process certain compounds in the waste are transformed to

combustible gases;


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4. Burnout: what is left from the previous processes contains mainly combustible solids (fixed carbon)that are now burned in the presence of oxygen and transformed to gases.

5. Cooling of the ashes: the solid non-combustible material (inert) present in the waste have beenheated up in the previous processes and are now cooled as much as possible in order to recuperatethis heat.

Vertical

1. Gas production: at the lowest level the series of horizontal sub-processes takes place2. Gas combustion: by adding air (or rather: by adding the oxygen in the air) the gases are fully

burned3. Gas burnout: in this zone the combustion is completed to ensure that the legal requirements are

met: for a minimum of two seconds the gases remain at a temperature of at least 850C in thepresence of at least 6% (by volume) oxygen after the last addition of oxygen.

A domestic waste incinerator has not only a combustion chamber, there is a whole installation which createsa complete "waste-to-energy" plant. Here is a technical description of the main companents.

Weightbridge

Weighing of incoming and outgoing waste flows is performed by means of weighbridges. The vehicleweighbridges are offen from the electronic type. On this system also the invoice is prepaired, and theincinerator plant operator knows how much waste is in the waste bunker.

Waste bunker with overhead cranes and scredder

Waste is left in the bunker and overhead cranes manage the waste of different types in the bunker. Big sizewaste is scredded and the cranes put the waste in the waste hopper of the furnace.

Furnace

Support burners (and optional start-up burners) are installed to maintain a temperature of more than 850Cduring at least 2 seconds also during start-up and shutdown. The combustion air is supplied in stages (in

different phases) via the air supply system that consists of several fans and air pre-heaters. The combustionresidues are evacuated by the ash extractor and are treated by the slag treatment system.

Burners

The burners installed can be removed from the furnace (whilst the incinerator is in operation). When this is

done a screen is placed in front of the opening. This enables the burner heads to be cleaned easily.

Ash extractor

The ash extractor is installed at the outlet of the grate. Bottom ashes and siftings are cooled down below+/- 60C before evacuation to the ash transport, a vibrating conveyor.

Slag treatement

After the ash extractor, the slag is transferred into a bunker by means of a vibrating conveyor. The ashesare transferred into a truck by means of cranes.

Slag treatement can be don on the incinerator plant or on a special recycle plant.

For example: A band magnet is positioned above the slag ash conveyor belt to separate out the iron in theslag. Also non-ferrous metals can be separated from the ashes (using an eddy current overband system).


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Steam boiler

The thermal energy produced in a waste-to-energy installation is recovered by means of the production ofsteam in a heat recovery boiler (one per line). Downstream the energy of the steam is transformed intoelectrical energy in the steam turbine.

The boiler type wich is well known in municipal solid waste incinerators is the "TAIL-END" type, with severalvertical radiant passes and an horizontal convective section.

The waste heat boiler is of the water tube type, with natural circulation.

Boiler Cleaning

Dust and fly-ash, carried by the flue gas stream, causes erosion and fouling of the boiler pipes, resulting inless efficient heat transfer, flue gas temperature increase through-out the boiler and considerable increaseof pressure drop. This is why an efficient cleaning system is of great importance in a waste to energyinstallation.


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The rotary kiln incinerator

The rotary kiln incinerator consists of a slightly inclinedrotating primary combustion chamber.The waste is

introduced at its highest end and deashing takes placeat its lowest part.Due to its cylindrical form,the heat isequally refracted to the burning waste and the heattransfer and -control is optimal.Because of the(dis)continuous rotation and the inclination of the

kiln,bottom ash is continuously and automaticallyevacuated.Due to the absence of any moving part in thehot zone,the rotary kiln can be operated under very hightemperatures.A rotary kiln is the most versatile incineratoravailable; it can treat a large range of wastes,varying fromlow to high calorific values and different particle sizes.Therotating primary chamber must be equiped with a staticpost combustion chamber,for achieving a complete burnout of the flue gases. The plant must be equiped with aflue gas treatment system,dry or wet - or a combination ofboth -before releasing the flue gases to the atmosphere.

A rotary kiln incineration plant is typically composed byfollowing items :

01 MAIN COMPRESSED AIR SYSTEM

Compressed air is used to power guillotine doors andhopper lids in a fail safe mode (normally closed). It is alsoused to atomise liquid waste and sludges into thecombustion chambers and for pulsating (for cleaning) thebags in the baghouse (if applicable).

02HYDRAULIC PACK

Hydraulic pack is driven by an electric motor,has ahydraulic oil tank and the pressurised oil is used to powerthe skip lift and the feeding ram on the incinerator.

03 SKIP (Waste feeding system)

The skip is hydraulically operated and its operation is

controled by the central computer.

04 FEEDER (Waste feeding system)

Rotary kiln incinerator

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Attachments and links

y Different types of rotary kilny Flue gas cleaningy Energy recoveryy Drying incineratorsy Incinerator and plastic recycling

Size & capacity_guidelines.xls

How to make a business plan of a rotarykiln incinerator plant? Learn more...


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The waste drops into the hopper by gravity, the ram beingretracted. When the hopper door closes (automatically),the guillotine door (fire door) opens and the he ram feedermoves forward to introduce waste into the kiln.When theram retracts, the guillotine door closes again.

05 ROTARY KILN

There are 2 different types of rotary kilns : the

historical co-current - and the modern moreelaborated counter-current design.The co-currentrotary kiln oxydises the total amount of waste under over-stoechiometric conditions (excess of oxygen),while thecounter-current rotary kiln operates partly by under-stoechiometric oxydation (pyrolysis) of the waste.In thiscase,the pyrolysis gases are used to fuel the postcombustion chamber-thus no auxiliary firing is required-while a co-current rotary kiln needs a burner to be fired

permanently to maintain the required temperature levelin the post combustion chamber.

A counter current rotary kiln allows a precise control of theflue gas stream and therefore its overall dimensions are

much more compact than its co-current parent.

Also,the combustion air being introduced at the lowest partof this type of rotary kiln,opposite to the direction of thewaste flow,it cools down the ash extraction area and as a

consequence the bottom ash is cool and dry by nature andnot any slagging occurs.

For more details,please refer to the attachment..

06 MAIN BURNER (natural gas or diesel oil)

The main burner has no other purpose than to preheat thekiln,before feeding any waste.Under normal operatingconditions,this burner is not operative.

07 POST COMBUSTION with auxiliary (start)burner

The post combustion chamber(s) is(are) designed to allowa residence time of the flue gases in excess of 2 seconds-at 1100 Degr.C.As the burner will only be in service for

preheating the post combustion chamber,before anyintroduction of waste can take place,it automaticallyretracts upon reaching the correct operating temperature..

08 SAFETY (emergency) OUTLET

In case of a fatal error (eg. power failure),detected by thecontrol system,the whole plant is automatically andcompletely shut down (no further feeding will beallowed).The remaining thermal energy is released to theatmoshere by natural draft of a dedicated exhaustsystem.After the plant returns to its normal operation

Example 1: Rotary kiln incinerator, dry + wetscrubbing

Example 2: Rotary kiln incinerator with dry scrubbing

Example 3: Rotary kiln incinerator with wet scrubbing

Summary table:

Waste Technology

Medical/hazardous/industrial waste Rotary kiln

Domestic / household waste Moving grate


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condition,this safety device will automatically bedesactivated.

09 COOLING CHAMBER

The particulates,present in the hot flue gas stream,tend to

soften and to become sticky at temperatures above 950Degr.C.For preventing any slagging at the inlet of any heatexchanger,used to recover and/or to cool down the flue

gas,we fit a cooling chamber in which the temperature ofthe flue gases is reduced to 850 Degr.C,by introduction ofa small amount of ambiant air.

10 ENERGY RECOVERY

Raw flue gases need to be cooled before being treated and

being released to the atmosphere.Cooling may be doneeither by quenching (wet flue gas treatment) or byexchanging the heat to another medium.This medium canbe steam or thermal oil or air.If steam is generated,it can

be used to drive a turbo genset or to heat other processequipment.Heat exchangers can be installed,either in lineor in by pass of the process flow.In case of dry scrubbingwith sodiumbicarbonate a bag house is required to filterout the particulates.If hot air is generated,it can be usedfor materials drying.

Below,we summarise the most frequently used types ofenergy recovery.

1. Energy recovery: hot air2. Energy recovery : steam3. Energy recovery : steam + electricity.

13 DOSINGUNIT SODIUM-BI-CARBONATE (dry)

Continuous,proces driven dosing of sodiumbicarbonate forneutralising acid components in the flue gases.Theneutralising reaction is completed in a venturi type reactorin which the reaction time is in excess of 2 seconds.

14 DOSINGUNITACTIVATED CARBON (dry)

Continuous dosing for the absorption of heavy metalsand of eventually re-formed dioxins and furans in the heatexchanger.The absorption process is completed in a venturitype reactor (absorption time in excess of 2 seconds)

15 BAGHOUSE (dry scrubbing)

The filtering bags in the baghouse remain permanentlycoated with a layer of a mixture of sodiumbicarbonate and

activated carbon.The neutralising reaction of acids and theabsorption of heavy metals and dioxins is furthercompleted during the passage of the flue gases throughthis layer.At the same time,all particulates are removedfrom the flue gas stream,before they are evacuated to the

Liquid/gas/fluid waste static hearth

Homogenous waste (ex.WWTP sludge) Fluidized bed

Ammunition destruction Ammunition

Unburnable waste (ex. Asbestos) Plazma


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atmosphere.This guarantees an overall efficiency of the dryscrubber for HCl abatement of at least 97%. Particulateemission after the fabric filter is less than 10 mg/Nm

16ID FAN

One induced draft fan, ebonite coated if a wet scrubberstep is added.The rotation speed of the induced draft fan ispermanently controled by the system for maintaining a

steady negative pressure in the process.

17 CHIMNEY

One chimney for main exhaust.The height can be adaptedto local requirements.

Sitemap | Copyright 2012 BIC Group | Site created by Winderickx

Static hearth incinerator

The combustion of fumes/gas/liquids does not generate

much ash and therefore a static hearth incinerator can beused.Liquid waste is pumped straight from the tanks to theincinerator. The plant looks as follows :

1. A static hearth combustion chamber

In which the residence time is 2 sec at 1100 or 1200Degr.C (depending on the halogenides content of thewaste) .The incinerator is equipped with a start-up andsupport (pilot) burner on natural gas and a liquid waste

injection system equiped with compressed air atomisation.The waste feed stock has to be blended such that thechlorine content of the mix does not exceeded 2% (inmass) ,when using a dry scrubber.(A wet flue gas scrubbercan handle up to 30% of Chlorine,thus no blending isrequired)

2. A flue gas cooling system.

To drop the temperature from 1100 Degr.C down tomax.200 Degr.C.The system may consist of a heatrecovery system (steam,thermal oil,hot air,etc) or of a fluegas quenching or as a combination of any.

3. An activated carbon dosing system

For abatment of dioxins and furans

4. A sodium Bi-Carbonate injection and dosingsystem

Incinerator for hazardous gas/fumes/liquids

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Size & capacity_guidelines.xls


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For the neutralisation of acid components in the flue gas.

5. A dry filter (bag house)

The bag house is equipied with Teflon sleeves and anautomatic fly ash extraction system .

6. An induced draft fan

The speed controled fan regulates the flow in the system

7. A stack

App. 30 m. high

8. A control system

For all process control by PLC Summary table:

Waste Technology








Fluidized bed incinerator

The fluidized bed incinerator is used for waste with alow density and it must be homogenic (ex. WWTP sludge).Also to clean paint from iron or steel, fluidized bed is acommon used technology.

The combustion chamber has mostly a square chape andthere is a lot of sand present. The start up and maintanceburner is upstares the combustion chamber. At the bottom,the floor of the combustion chamber, there is a mixere ofgas and air injected. Every sand particale has now 2forses:


y Moving grate incineratory Fluidized bed incineratory Plazma incinerator

Incinerators for hazardous waste

y Rotary kiln incineratory Static hearth incinerator


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y The graviation forse (Fg) which pulls the sandparticle down

y The pneumatic forse (Fp) which lift the sandparticle up

The sand particles have now the next possibilities:

Fgrav. > Fpneu. Fgrav. = Fpneu. Fgrav. < Fpneu.

Gravitation

The sand particles

are falling down inthe combustionchamber

Fluidized bedstage

The sandparticles arefloating in the

combustionchamber

Pneumatictransport

The sand particlesare flying up to thetop of the

combustionchamber

So, the fluidized bed stage of the incinerator is the stagethat the sand floats in the combustion chamber at atemperature of min. 350 degr.C. The most difficultis controlling the correct air-gas mixure and flowregulations at the bottom of the combustion chamber.

If the combustion chamber is correct working, there is ablue flame tracking over the fluidized bed zone of the

combustion chamber.

Medical waste in fluidized bed?

Medical waste contains hard metal materials, likeneedles, this is not homogenous and the waste fallsthrough the fluidized bed zone. Sometimes a grid basket isset up in the fluidized bed combustion chamber to catch upthe materials which fall through the fluidized bed zone. But

y Ammunition destruction incineratorExternallinks

y http://www.cpfd-software.com/Summary table:

Waste Technology








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the grid basked disturbs the sand floating process,which creates a bad combustion.

Flue gas treatement

Because of the high concentrations of sand in the

combustion chamber, also the flue gas will contain a lot ofsand. As a first flue gas treatement step, a cyclone is used.


Ammunition destruction incinerator

BIC have been asked to fabricate a one-off designedreaction chamber to detonate small caliber ammunition.

The plant featured an armoured reactor kept at about 500

degC in which the ammunition detonates. The scrap metalleaves the reactor by gravity and a magnet conveyorseparates the ferous from non-ferrous metals. The latterare subsequently compressed in a hydraulic press and sentfor recycling, separately from the other scrap.

The plant features the necassary water cooled safety locks

at the feeding and scrap extraction and is built into 2 ISO

20' frames for ease of transport and assembly.


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Summary table:

Waste Technology








All Types of Waste Incinerators

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