INCINERATOR

Piringan bergerakSalah satu jenis insinerator adalah piringan bergerak (moving grate).Insinerator jenis ini memungkinkan pemindahan sampah ke ruang pembakaran dan memindahkan sisa hasil pembakaran tanpa mematikanapi. Satu wadah piringan bergerak dapat membakar 35 metrik ton sampah perjam. Jenis insinerator ini dapat bergerak ribuan jam pertahun dengan hanya satu kali berhenti, yaitu pada saat inspeksi dan perawatan.Sampah diintroduksi ke "mulut" insinerator, dan pada lubang di ujung lainnya sisa hasil pembakaran dikeluarkan.Udarayang dipakai dalam proses pembakaran disuplai melalui celah piringan. Aliran udara ini juga bertujuan untuk mendinginkan piringan tersebut. Beberapa jenis insinerator piringan bergerak juga memiliki sistem air pendingin di dalamnya.Suplai udara pembakaran sekunder dilakukan dengan memompa udara menuju bagian atas piringan. Jika dilakukan dengan kecepatan tinggi, hal ini dapat memicuturbulensiyang memastikan terjadinya pembakaran yang lebih baik dan surplusoksigen. Turbulensi ini juga penting untuk pengolahan gas sisa hasil pembakaran sampah.Fasilitas insinerasi harus didesain untuk memastikan bahwa gas sisa hasil pembakaran mencapai temperatur 850oC selama dua detik untuk memecahracun kimia organik. Untuk lebih memastikan hal tersebut, biasanya diperlengkapi dengan pembakar yang pada umumnya memakaibahan bakar minyak, yang lalu dibakar ke insinerasi untuk mendapatkan panas yang memadai.Gas sisa hasil pembakaran lalu didinginkan. Panas yang ada ditransfer menjadi uap dengan memaparkannya pada sistem pompa air. Uap ini lalu digunakan untuk menggerakkan turbin. Gas yang telah melalui pendinginan dipompakan ke fasilitas sistem pembersihan. Piringan tidak bergerakIni adalah tipe yang lebih tua dan sederhana. Piringan tetap yang tidak bergerak berada di bagian bawah insinerator dengan bukaan pada bagian atas atau samping untuk memasukan sampah dan bukaan lainnya untuk memindahkan bahan yang tidak terbakar (abu,logam, dan sebagainya). Rotary kilnTipe ini cocok untuk menginsinerasi limbah sludge ex WWT atau limbah yang mempunyai kandungan air (water content) yang cukup tinggi dan volumenya cukup besar. System incinerator ini berputar pada bagian Primary Chamber, dengan tujuan untuk mendapatkan pembakaran limbah yang merata keseluruh bagian.Proses pembakarannya sama dengan type static, terjadi dua kali pembakaran dalam Ruang Bakar 1 (Primary Chamber) untuk limbah dan Ruang Bakar 2 (Seacondary Chamber untuk sisa-sisa gas yang belum sempurna terbakar dalam Primary Chamber.

Fluidized bedFluidized bed adalah teknologi pembakaran yang digunakan dalam pembangkit listrik. Fluidized bed menangguhkan bahan bakar padat di atas jet-meniup udara selama proses pembakaran. Hasilnya adalah pencampuran turbulen gas dan padatan. Aksi berjatuhan, seperti cairan menggelegak, memberikan reaksi kimia yang lebih efektif dan transfer panas. Tanaman FBC lebih fleksibel dibandingkan tanaman konvensional yang mereka dapat dipecat pada batubara dan biomassa, antara bahan bakar lainnya.Sistem pembakaran bahan bakar padat untukFluidized bed mengurangi jumlah belerang yang dipancarkan dalam bentuk emisi SOx. Kapur digunakan untuk mengendap sulfat selama pembakaran, yang juga memungkinkan transfer panas lebih efisien dari boiler ke peralatan yang digunakan untuk menangkap energi panas (biasanya tabung air). Endapan dipanaskan datang di kontak langsung dengan tabung (pemanasan dengan konduksi) meningkatkan efisiensi. Karena ini memungkinkan tanaman batubara untuk membakar pada suhu dingin, kurang NOx juga dipancarkan. Namun, pembakaran pada suhu rendah juga menyebabkan emisi hidrokarbon aromatik polisiklik meningkat. FBC boiler dapat membakar bahan bakar lain selain batubara, dan suhu pembakaran yang lebih rendah (800 C / 1500 F) memiliki manfaat tambahan lainnya juga.

Incineration (continued)The following are types of incinerators: ROTARY KILN FLUIDIZED BED LIQUID INJECTION MULTIPLE HEARTH CATALYTIC COMBUSTION WASTE-GAS FLARE DIRECT-FLAMEOf these, rotary kiln, fluidized bed, and liquid injection are the most, prevalent in industry because of their applicability to large scale use and their versatility. Consequently, these three kinds will be emphasized.ROTARY KILN CHARACTERISTICS: ROTATE WASTES IN CYLINDRICAL CONTAINER, ENABLING THOROUGH MIXING WITH AIR OPERATING TEMPS. FROM 1500-3000 F ( 800 - 1650 C ) HAS GREATEST RESISTANCE TO HIGH TEMPS. CAN HANDLE LIQUID, SLUDGE, SOLID, OR GASES IN VERY LARGE QUANTITIES CAN OPERATE IN BATCH MODE, ALLOWING MORE FLEXIBILITY THAN CONTINUOUS MODE CAN BE MOBILE TO ALLOW ONSITE TREATMENT CAN ACCEPT ENTIRE DRUMS OF WASTE, A UNIQUE FEATUREFLUIDIZED BED CHARACTERISTICS: vessel contains inert granular material that expands and acts theoretically as a fluid when gases are injected up through the material bed from nozzles OPERATING TEMPS FROM 1400-1800 F ( 750 -1000 C ) CAN HANDLE LIQUID, SLUDGE, SOLID, OR GASES WASTE ENTERS THROUGH NOZZLES OFFERS NEARLY ISOTHERMAL OPERATION CAN'T HANDLE WASTES THAT MELT AND SLAG, DISRUPTING FLUIDIZATIONLIQUID INJECTION CHARACTERISTICS: WASTES ARE SENT THROUGH NOZZLES AND ATOMIZED INTO SMALL DROPLETS TO ALLOW FOR THE GREATEST POSSIBLE MIXING WITH AIR OPERATING TEMPS. FROM 1200-3000 F FEED MUST ACT AS A LIQUID HAVING A VISCOCITY LESS THAN 10,000 SSU SOLIDS ARE OKAY IF THEY CAN BE MELTED AND PUMPED CAN COMPLETELY COMBUST NONCOMBUSTIBLES LIKE CONTAMINATED WATER, ALONG WITH ORGANIC COMBUSTIBLE MATERIAL HAS A HORIZ. OR VERT. CONFIGURATION A SUSPENSION BURNER, THAT IS THE MOST LABORFREE AND FLEXIBLE KIND OF INCINERATOROne other characteristic that all three types of incinerators (rotary kiln, fluidized bed, and liquid injection) share is that they can all be operated in a pyrolysis or oxygen starved mode. Wastes with high caloric value that are capable of releasing great heat content are most appropriate for this kind of operation. The other types of incinerators are described as follows.Multiple hearth incineratorsconsist of vertically shaped hearths, and are Primarily used for sewage sludge. They are operated from 1400-1800 F ( 750 - 1000 C ). Catalytic combustion, waste-gas flare and direct flame incinerators are all for gases. Catalytic combustors use a catalyst and are designed for low organic concentration wastes. Waste-gas flares are used for non-hazardous waste that has high organic content. Direct flame incinerators operate from 1000-1500 f and are used when waste gas contains particles.On a final note, one very controversial form of incineration that presently has been banned in the United States, but is used in Europe is ocean incineration. For this,two incinerators are mounted on a huge ship that carries the wastes out to the middle of the ocean and burns them out there.the ideal wastes for this kind of disposal are toxic and hazardous wastes such as chlorinated matter, pcb's,and organometallics. Ocean incineration is perfect for these wastes because the acids produced can be neutralized by the huge buffering capacity of the ocean. This eliminates the need for scrubbers and other secondary treatment to detoxify the combustion products and make them more environmentally acceptable.

COMBUSTION INCINERATORS-OXYGEN USING SYSTEMSKEY FEATURES OF A COMBUSTION INCINERATOR: WASTE STORAGE AND HANDLING WASTE FEEDING COMBUSTION STEAM AND ELECTRICITY GENERATION AIR POLLUTION CONTROL ASH RESIDUE HANDLING

COMBUSTION STAGES (1)DRYING-MOISTURE IS EVAPORATED (2)DEVOLATILIZATION-COMBUSTIBLE VOLATILES ARE RELEASED (3)IGNITION-VOLATILES ARE IGNITED IN THE PRESENCE OF O2 (4)COMBUSTION OF FIXED CARBON-VOLATILE MATTER IS COMPLETELY COMBUSTED AND FIXED CARBON IS OXIDIZED TO CO2

TYPES OF COMBUSTION INCINERATORS1. MASS BURN-MOST COMMONMinimal preprocessing required (not much sizing, shredding, etc.). Mass burn Incinerators vary in size. They range from 100 to 1000 tons of waste per day. Use a grate system to mix and agitate the waste as it travels through the Furnace to provide complete combustion. Air for combustion is supplied by fans or blowers under and over the grates.THREE TYPES OF MASS BURN INCINERATORS (BASED ON ENERGY RECOVERY METHOD)(A)WATER WALL FURNACE ENERGY IS RECOVERED BY STEEL TUBES FILLED WITH WATER WHICH LINE THE COMBUSTION CHAMBER

(B)REFRACTORY FURNACE ENERGY IS RECOVERED BY A WASTE HEAT BOILER LOCATED AFTER THE COMBUSTION CHAMBER

(C)ROTARY KILN FURNACE SIMILAR TO A REFRACTORY FURNACE, BUT USES A ROTATING COMBUSTION CHAMBER 2. MODUAL COMBUSTOR TYPICALLY SMALLER THAN MASS BURN INCINERATORS 25 TO 120 TONS/DAY VERY LITTLE PREPROCESSING INVOLVED WASTE IS FED INTO FURNACE BY A HORIZONTAL, HYDRAULIC RAM

3. FLUIDIZED BED COMBUSTOR LIMITED EXPERIENCE WITH MIXED SOLID WASTE PREHEATED AIR, UNDER PRESSURE, IS FORCED THROUGH A BED OF SAND, CAUSING THE SAND TO EXPAND. MIXED SOLID WASTE IS FED ONTO THE SAND BED, WHERE COMBUSTION TAKES PLACE

NON-COMBUSTION TECHNIQUES-OXYGEN DEFICIENT(LIMITED USE IN THE US)1. BIOGASIFICATIONMixed solid waste is placed into an anaerobic digestor to reduce its Volume and to produce methane. The process involves: (A)preprocessing-the organic material is separated from the waste stream, shredded, and placed into a slurry (B) decomposition-the slurry is placed in an anerobic digestor for 5-30 days (C) gas collection-methane gas is collected and refined for combustion (D) less voluminous digested product for disposal

2. PYROLYSISUses heat to decompose the mixed solid waste in an O2-deficit or O2-free Environment. The products of pyrolysis include combustible gases and Various solids that are difficult to manage.COMBUSTION FUNDAMENTALSThe following reactions take place for combustion of fuels containing C, H, and S (in order of occurrence): H2 + H2 + O2 --> H2O + H2O 2C+ O2 --> CO + CO CO + CO + O2 --> CO2 + CO2 S + O2 --> SO2

The optimal temperature for combustion of mixed solid waste is in the range from 1400-1600 degrees f.AIR REQUIREMENTS FOR COMBUSTION:Stoichiometric amount of air or o2 is the amount of air or o2 required based On stoichiometry. Sometimes, extra air or o2 is required for complete Combustion. This is expressed as excess air or o2. Typical excess air Requirements are 80-50% of the theoretical or stoichiometric demand. On The average, 6-10 pounds of air are required to combust one pound of waste.The amount of theoretical oxygen needed can be found by balancing the Chemical reaction. An easy-to-use formula has been developed to determine Volume of theoretical O2 needed to combust a fuel or waste which contains C, H, S, and O:O2 (CUBIC FT.)/LB OF FUEL = 395((C/12) + (H/4) + (S/32) - (O/32))C, H, S, and O are the decimal fractions of that element in one pound of The fuel (dry weight). In new york state, incineration with energy recovery comes right after recyclind and before landfilling on its solid waste management hierarchy list. Used properly and safely, incineration can be an effective way to dispose of our waste while producing a valuable form of energy.The main purpose of incineration is to reduce the volume of solid waste, but There are more specific incinerators that burn off dangerous organic Pollutants or hospital wastes. There is also the possibility of energy Recovery with the addition of a boiler. Incineration itself is a Controversial topic these days. Here are some of the pros and cons:PROS: WASTE VOLUME REDUCTION DESTRUCTION OF COMBUSTIBLE TOXINS DESTRUCTION OF PATHOGENICALLY CONTAMINATED MATERIAL ENERGY RECOVERYCONS: AIR POLLUTION PROBLEMS ASH MUST BE LANDFILLED AND MAY BE HAZARDOUS HIGH CAPITAL AND OPERATION COSTS WASTEWATER PROBLEMS:COMMERCIAL OR INDUSTRIAL INCINERATORS- USUALLY SPECIFIC OR 'TAILOR-MADE' MORE CONSISTANT WASTE STREAM HIGHER TEMPERATURES MAY BE NECESSARY STANDARDS FOR DESTRUCTION OF HAZARDOUS WASTE ARE SET AT THOSE THAT WILL DESTROY PCB'S (POLYCHLORINATED BIPHENOLS).MUNICIPAL INCINERATORS- MORE COMMON LESS CONSISTENT WASTE STREAM PRE-TREATMENT (SHREDDING, DRYING, ETC.) IS USUALLY NECESSARY BATCH OR CONTINUOUSLY LOADED