Cremators-Macroburn

MACROTEC ccSPECSHEET MACROBURNCREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUPMACROBURN CREMATOR UNITSMACROburn Cremators utilise the high standard of technology developed for MACROburnIncinerators. Many years of experience building tough, rugged, economical, reliable andsmokeless incinerators enabled MACROtec to design cremators that provide outstandingperformance and have an exceptional life span.COMBUSTION CHAMBERSThe MACROburn Cremator has five chambers. The coffin, or cadaver in a bag or shroud, isplaced on the hearth in the Phase I Primary Chamber. After the highly combustible componentshave burnt away, the remains are raked down into the Phase II Chamber, where burnout iscompleted. A second cremation can be started on the Phase I Hearth during the Phase IIburnout of the first cremation.Gases from the primary chambers pass through a mixing chamber and tertiary combustionchamber, where smoke and odours are completely eliminated by high temperature combustion.The chimney is mounted over the tertiary combustion chamber.The fifth chamber is a cooling chamber for the ashes.FUEL & BURNERSBurners are required for ignition and smoke elimination. MACROburn Cremators can be firedby diesel oil, towns gas, L.P. gas or natural gas. The burners have fully automatic startsequence, flame monitoring and shut down. Automatic temperature controls regulate theauxiliary heat supplied. This ensures longer refractory life and maximum fuel saving.OVERVIEWA PROUD MEMBEROF THE Ai-TEC GROUPSPECSHEET I 01FLAME INTENSIFIERThe MACROburn Flame Intensifier is a recuperative system for providing greatly improvedcombustion efficiency and enormous fuel savings. Fuel consumption is reduced drastically.Hotter, cleaner flames produce less unburnt carbon and less smoke. Secondary air is preheatedin an antechamber where heat is collected from the base of the chimney.CHIMNEYS & FLUESMACROburn Cremators operate best with top mounted, natural draught chimneys. Werecommend the use of 3CR12 corrosion resisting steel. Such chimneys do not require refractorylining or insulation. Although mild steel is quite adequate, it will require more maintenance,Mechanically induced draught systems can be used and are generally necessary if the crematoris to be fitted with scrubbers or dry filters. Accurate draught control is essential. MACROtecmanufacture sensors and control dampers specifically designed for these applications.AUTOMATIC CONTROL OF AIR & COMBUSTION RATEAn excessive burning rate is immediately and automatically reduced. Conversely when theburning rate is low, more rapid combustion is induced. Control is achieved by variations in gasflows and pressures and does not incorporate any moving or wearing parts.Automatic air control completely eliminates the necessity for manual operation of air dampers.Quantities of primary and secondary air are constantly varied to suit changing combustionconditions. No moving parts are involved.Automatic fan controls keep the burner fans running after shutdown. They switch off automaticallyonce the cremator has cooled off sufficiently. This results in longer life for the burner draughttubes, nozzles, diffusers and flame detectors.Simplified electric control panels on standard MACROburn incinerators are designed foroperation by unskilled labour. A single, lockable push-button actuates the starting of all burners,fans, ignition transformers, solenoid valves and control instruments in the correct sequence.Similarly a single push-button actuates the shut down.Door operated draught reducer automatically reduces the chimney draught while the loadingdoor is open and shuts off the normal air supplies. The resulting reduction in the amount ofcold air drawn in through the loading door reduces fly-ash entrainment and thermal shock onthe refractory, with resultant longer refractory life.Explosion relief safety doors swing open in the unlikely event of an explosion. The slidingloading door swings out at the bottom and the blast is directed downwards.High alumina monolithic refractory linings withstand temperatures in excess of 1500°C andare specially selected to give maximum durability under conditions of sudden and extremetemperature change (thermal shock). The carefully controlled bake-out, which is part of theservice supplied by MACROburn agents, ensures optimum linings with a long life expectancy.High quality insulation around the entire cremator ensures low surface temperatures andminimum fuel consumption.Dry type smoke and fly ash elimination which has proved completely effective, also ensuresdry corrosion- free chimney stacks and hot dry gasses that rise straight off the top of thechimney. (No wet, dragging plume.)The large sliding loading door is at the right height and angle for easy loading or raking.Smooth outer casing free of obstructions is easy to keep clean. All the rolled steel sectionsused to brace the cremator are inside the 4.5mm thick casing.MACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUPSPECSHEET I 028MACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUPSPECSHEET I 031 23456791011121. Secondary Burner “Hi/Lo”2. Primary Burner “Hi/Lo”3. Extended Primary Chamber4. Loading Door5. Primary Chamber6. Hearth7. Fat Retention Tray8. Ash Removal Door9. Phase II Chamber10. Phase II Burner11. Fat Retention Tray12. Cooling Chamber1 234567C.L. LOADING DOORC.L. PRIMARY CHAMBER1. Secondary Burner:Horizontal flame fires intomixing chamber.2. Primary Burner:Flame angled downwardsto form a vortex in theprimary chamber.3. Control Panel4. Phase II BurnerShort flame for intense rapidburn-out of ash in lower chamber5. Loading Door(Stainless Steel Optional)6. Chimney7. Tertiary Combustion Chamber:For final burn-out.8. Roof Outline9. Secondary Mixing Chamber:With heated refractory screenfor turbulence.89MACROBURN CREMATORPRIMARY CHAMBERSMACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUPSPECSHEET I 03EMISSION CONTROL SYSTEMObnoxious emissions can be divided into three main groups:1. CARBONACEOUS MATTERThis group includes hydrocarbons, many of which are malodorous and/or acidic, carbonmonoxide and pure carbon. Very fine particles of carbon constitute black smoke. Carbonaceouspollutants can be eliminated by complete combustion. Carbon and hydrocarbons are brokendown into carbon dioxide and water. Requirements for complete combustion are:• Oxygen. Air must be available in sufficient quantities for complete oxidisation of the carbonand hydrogen (volatiles) released. An oxygen shortfall is usually the result of volatiles beingreleased too rapidly. Control of the rate of release (the Rate of Combustion) ensures thatcarbonaceous emissions due to a shortage of oxygen are eliminated.• Time. Combustion is a chemical reaction (oxidisation). It requires time for completion. Thetime available is determined by the speed at which the volatiles pass through the crematorand by the volume of the chambers. Large secondary chamber volumes and a controlledRate of Combustion ensure sufficient time.• Turbulence. Thorough mixing of air and volatiles is essential for complete combustion. Theflame port, mixing chamber and heated refractory screens are designed to produce turbulence.Optimum turbulence is dependent on gas velocities. Gas velocities are determined by theRate of Combustion.• Temperature. Elevated temperatures are required for complete oxidisation in the secondaryzones of the cremator. Conversely, reduced temperatures are required on the hearth andin the primary chamber to control the rate of volatilisation. Temperatures have a direct effecton the rate of combustion and the rate of combustion has a direct effect on the temperatures.Control of the Rate of Combustion is essential.2. ENTRAINED ASHFine particles or flakes of incombustible material usually light in colour, are entrained in thestream of gases. Visible flakes are called fly ash. Clouds of fine dust are described as whitesmoke. They cannot be eliminated by combustion.Removal of entrained fly ash becomes more difficult as the gas volume and temperatureincrease. The combustion process, secondary air, gases from the secondary burner andincreasing temperature all add to the volume of gases. Ash entrainment prevention is bestcontrolled at source, on the hearth, before the volume and temperature increase. Entrainmentfrom the hearth is minimised by control of the Rate of Combustion.3. CHEMICALLY FORMED COMPOUNDSObnoxious, incombustible vapors and gases are sometimes liberated or formed during thecombustion process. Many of these emissions are completely invisible. Others are in gaseousform at the temperatures in the cremators and condense to a visible plume of liquid or solidparticles on leaving the chimney. They cannot be eliminated by combustion. However in somecases ensuring combustion conditions that inhibit the process can reduce the formation orliberation of these compounds.Chemically formed compounds are so diverse that it is impossible to do any more than describea few of the more common ones:• NOx is formed at very high temperatures. Such high temperatures are prevented byCombustion Rate Control.• Halogens include chlorine, fluorine, bromine and iodine. The most common sources arePVC and PTFE plastics. Fortunately these are not the most common plastics in coffins etc.Most plastics do not contain halogens. Ashes produced by wood, paper and animal tissueconsist of basic oxides. They have a high affinity for halogens and combine readily to formchlorides, bromides etc. If small percentages of halogenated plastics are burnt, a significantamount of the halogen will remain in the ash. Emissions will be minimal.SPECSHEET I 04MACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUP• Dioxins and Furans, which are a cause for concern in incinerators, are not formed in theabsence of halogens.• Sulphur. The fuels used in cremators and the components of a typical cremation have relativelylow sulphur contents. Therefore sulphur emissions from cremators rarely cause concern.• Very small amounts of lead, silver, mercury, chrome and cadmium may occur in oxide formbut the quantities are usually negligible. Controlled combustion reduces the oxidisation.THE COMBUSTION CONTROL SYSTEMMACROburn Cremators eliminate emissions at source by utilising advanced techniques ofcombustion control. Combustion takes place in two distinct phases:Phase I: When heat is applied to waste, volatiles are driven off. These can be oxidised (burnt)at source, in the fire-bed or later in a secondary combustion zone. Volatilisation does notrequire air or oxygen. The rate of volatilisation is temperature dependent. Volatiles, burnt inthe fire-bed, raise the temperature of the bed and promote more rapid volatilisation. Inhibitingcombustion of the volatiles in the fire-bed can slow volatilisation. Not all volatiles are combustible.Water vapour is a volatile. High percentages of incombustible or low heat volatiles, requireadditional heat from auxiliary burners.Phase II: Once the volatiles have been driven off, a black carbon char remains. This char iscompletely unaffected by heat. It can only be burnt in the fire-bed and requires a steady supplyof air or oxygen at high temperature for combustion.“PRIMARY” VS. “SECONDARY”The two phases of combustion outlined above must not be confused with what are commonlyknown as Primary and Secondary combustion.Primary Combustion refers to combustion that takes place on or in the fire-bed itself. Thus allof the combustion in PHASE II above is primary combustion. The combustion of any volatilethat is burnt in the fire-bed is also regarded as primary combustion.Secondary Combustion refers to combustion that takes place at some point away from thefire-bed. Similar distinctions are made between:• PRIMARY and SECONDARY AIR,• PRIMARY and SECONDARY HEAT and• PRIMARY and SECONDARY BURNERSAir or heat added to the gas stream above the fire-bed in the Primary Chamber can have eithera primary or a secondary effect. If the gas stream moves down onto the fire-bed, it has aprimary effect. If it moves away from the fire-bed it is actually SECONDARY air or heat, eventhough it was introduced in the primary chamber. It is possible to increase or decrease therate of volatilisation (rate of combustion) by simply diverting heat and air either down onto thefire-bed or away from it.FOUR ELEMENTS OF COMBUSTION CONTROL1. The primary chamber of a MACROburn cremator is designed so that the heat, air and hot gasesmove in a vortex with horizontal axis. Temperature differential and the release of volatiles from thefire-bed interrupt the vortex and deflect the heat and air into the second chamber. This ensures aconstantly modulated supply of heat and air to the fire-bed and thus controls the rate of combustion.2. Negative pressure resulting from the chimney draught induces some of the air into theprimary chamber. When strong burning is in progress, a pressure build-up in the primarychamber reduces the negative pressure and the air available for primary combustion. The rateof combustion is reduced accordingly.3. Most of the air for secondary combustion is induced by negative pressure. It is introducedinto the gas stream at a point where a constriction in the gas flow path causes an increase inthe gas velocity. This creates a venturi effect. As the volume and velocity of the gas streamincrease, the venturi effect is increased. Consequently the volume of secondary air inducedwill increase to compensate for the reduction in primary air mentioned in the previous paragraph.SPECSHEET I 05MACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUP4. Natural draught chimneys on MACROburn cremators provide an automatic increase indraught as the chimney temperature increases.• The four control elements are fully modulating.• Control is achieved without the use of moving parts.• The system is simple and effective and will not wear out.• Burners, mounted on the primary chamber perform both primary and secondary functions.• Almost instantaneous diversion of heat and air from primary to secondary providescorrespondingly rapid adjustment of the conditions required for optimal combustion.The control elements outlined above are complimented by conventional controls such aspyrometers, to switch burners and fans on and off according to heat demand.In addition to the Combustion Control System there are several other features that contributeto effective emission control in MACROburn cremators.ADDITIONAL EMISSION CONTROLSTHE HEATED REFRACTORY SCREENA portion of the "fly ash" entrained in the gas stream is carbon not pure ash. The carbon canbe burnt away, but the time required is much longer than that required for the combustion ofvolatiles. The carbon flakes have a large surface area, are readily entrained and difficult to trap.Two sets of refractory slabs, located across the gas stream in the mixing chamber, force thegas to zigzag between them. Fly ash and carbon impinge on the slabs and are stopped brieflyin a zone of high temperature, turbulence and plenty of excess oxygen. This is very effectivein ensuring complete burnout of the carbon. The additional turbulence ensures better mixingof the volatiles and air and better, more complete combustion. It also breaks down the flakesinto particles with smaller surface areas, that are caught effectively in a settling chamber.THE FINAL COMBUSTION AND SETTLING CHAMBERThe combustion of carbon and volatiles takes time. A large “secondary” or final combustionchamber is required to ensure sufficient time for complete burn out. MACROburn crematorshave exceptionally large final combustion chambers.The effective size is further increased by the fact that the secondary air and heat are addedto the gas stream as far upstream as possible. The secondary burner (or after burner) ismounted on the side of the primary chamber. The upper levels of the primary chamber, theflame port and the mixing chamber are all effectively part of the secondary combustion zone.The large final combustion chamber also acts as a settling chamber. After burn out of thecarbon on the heated refractory screens, the mechanical strength of the flake is reduced.Impingement and the subsequent turbulence brake the flakes down into particles with muchreduced surface areas. These settle very effectively in the large MACROburn final chamber.DOOR OPERATED DRAUGHT LIMITERThe inrush of cold air when a cremator door is opened is a potential cause of fly ash entrainment,loss of combustion control, over-cooling of the fire and thermal shock on the refractories. TheMACROburn loading door is fitted with an automatic draught limitter that reduces the chimneydraught, and the inrush of air, as the door is opened. Some negative pressure must howeverbe maintained to prevent hot gas and flames from escaping through the open door. A reducedamount of excess air is therefore drawn in through the open door. To compensate for thisexcess air, the normal secondary air supplies are automatically reduced as the door is opened.The draught and the air supply are restored as soon as the door is closed.CONCLUSIONMACROburn cremators make full use of every aspect of emission control by sophisticatedcombustion control and elimination of entrainment within the cremator itself. The systems aresimple to operate and maintain having no moving parts except for those in burners and fans.SPECSHEET I 06MACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUPSPECSHEET I 07MACROBURN CREMATOR UNITSA PROUD MEMBEROF THE Ai-TEC GROUPREGISTERDesigned by MACROtecManufactured by MACROline Eng.COMBUSTION RATESG.R.E. Rating 220kg per hourMaximum Rate 132kg per hour(continuous load)Average Rate 60-80kg per hour(intermittent load)Model No V221DIMENSIONSCremator casing (excl. burners & controls)Length 2916mmWidth 2420mmHeight 2545mmLoading Door 700mmMass 11800kgCHAMBER SIZESPrimary Chamber 1.90m3 (Volume)Primary Hearth 2.20m2 (Area)Phase II Chamber 0.30m3 (Volume)Phase II Hearth 0.50m2 (Area)Secondary Chamber 2.76m3 (Volume)BURNERSMake/Model FBR or RIELLOType Packaged/F.D.FanFuel LPG or Natural Gasor Diesel OilPrimary Output 250kW high fire150kW low firePhase II Output 150kW high fire30kW pilotSecondary Output 250kW high fire150kW low fireAIR SUPPLIESPrimary Over Fire Natural inducedconcentric with burner.Flame Intensifier Preheated, forced,side blast air to mainand Phase II Hearths.Secondary Venturi induced intomixing chamber.Burner Air Packaged forced draughtfans integral with burners.CHIMNEYConfiguration 600mm dia top typeDraught Natural InducedStandard Height 12.5m a.g.lCONTROLSTemperature Individual Cr Al, indicatingcontrollers for:- Primary Burner- Secondary Burner- Phase II BurnerBurner Start and Fully auto burner cyclesShut-down including pre-purge, airproving, spark ignition,pilot proving and mainflame start. Hi/lo primary& secondary burners.Flame Monitoring (diesel) Flame Eye(gas) IonizationAuto Shut Down In the event of flame failure,one attempted restart before“lock out”. Manual reset bypush button on burner.Air Quantities Internal back pressuresmodulate primary overfire air.Gas velocities modulatesecondary venturi induction.Door operated draught limitterreduces draught and air supplywhen loading door is opened.Auto dampers on hi/lo burners.SAFETY FEATURESGas Train Double shut off valves.Explosion Relief Loading door and ash doorsswing open.Auto Burner Controls Prevent start up in the event ofspurious signals, lock out in theevent of flame failure, prepurge.Liquid Containment Fats & liquids, contained bystainless steel pan under hearth,are burnt in Phase II Chamber.EMISSIONSTypical averages for actual, uncorrected stack volumes.Short term variations will occurO2 12 - 18%N2 70 - 75%CO2 4 - 7%H2O 3.5 - 4.5%CO less than 10ppmCl2 or HCl less than 30mg/m2Fl2 or HFl less than 30mg/m3SOX less than 25mg/m3Heavy Metals traces - negligibleRETENTION TIMESPrimary 1.2 secondsSecondary 2.0 secondsPhase II Small - negligibleTotal 3.2 secondsTECHNICAL DATA