Of 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.
One 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 incinerators consist 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.
KEY FEATURES OF A COMBUSTION INCINERATOR:
1. MASS BURN-MOST COMMON
Minimal 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
(LIMITED USE IN THE US)
Mixed solid waste is placed into an anaerobic digestor to reduce its Volume and to produce methane. The process involves:
Uses 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.
The following reactions take place for combustion of fuels containing C, H, and S (in order of occurrence):
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:
COMMERCIAL OR INDUSTRIAL INCINERATORS-
PLEASE DIRECT COMMENTS AND QUESTIONS TO:
ANNA C. RUEPPrueppa@rpi.edu