A crematorium for funeral use is a sophisticated technology. It must be adapted to the most stringent environmental requirements. Only the most modern equip with proven systems to reduce pollution and low consumption.
Funeral cremation ovens are generally designed with a primary and a secondary combustion chamber.
The design of this equipment is thought so that the process is one-way. That is why the coffin places inside the primary chamber of the crematorium. There, it will reach 800-850 ° C.
The primary chamber is usually constructed of laminated carbon steel sheet and a reinforced structure to give it strength.
The insulation is made up of special concrete, firebrick, and low thermal mass insulating materials. Low thermal mass insulating materials cover the interior of both the incinerator and the surrounding area.
The primary chamber has the thickness of insulation. So that the external temperature of the equipment cannot cause an accident due to burns on the external walls.
Logically, the design of the incinerator and the materials used allow the movements of the expansion of the inner refractory lining. The primary chamber has burners that release fire and air to break up debris and facilitate combustion.
Most crematoriums are multi-fuel, that is, they can use gas (butane, propane, natural gas), diesel, fuel, or electricity. The secondary chamber, however, is preheated with support fuel to keep it at approximately 850 ° C.
Energy consumption of a crematorium oven
The maximum thermal power of the burners in a crematorium is around 600 kW. The fuel used in an efficient furnace cremation varies depending on the fuel used.
Energy consumption is between 22.5 and 30 m 3 of natural gas. 30 liters of diesel (inefficient furnaces), or 900 kWh.
The combustion starts at the primary chamber and is then fed through a small series of ducts from the secondary chamber.
This is heated with afterburners and fed with secondary air that allows complete combustion and reduces emissions of carbon-based particles (PM), and volatile organic compounds (VOC), and persistent organic pollutants (POP).
The secondary chamber at about 300 ºC serves to burn the gases emitted for a time of one to two seconds.
From there they go to the cooling system prior to the purification systems formed by a multiple heat recovery system. It can provide savings in the operation of the furnace.
The purification system uses different filters and reagents. In a modern oven, the reagent consumption is around 0.5 kg/cremation.
The time required to complete cremation may vary depending on the type of burner. It may depend on the weight and size of the coffin, and the person.
Generally, the cremation time lasts between 75 minutes and 3 hours, including the cooling-down period.
Currently, there are modern ovens with automatic combustion control that can efficiently and sequentially perform up to 8 cremations in a 12-hour shift.
Human ashes are not toxic
The cremation process begins when the casket is automatically introduced from the introduction system to the incinerator.
In most crematoriums, one does not require the casket to be made of environmentally friendly materials such as cardboard or untreated wood.
The contamination of a crematorium is conditioned by the composition of the materials and finishes of the coffin.
Other countries allow coffins. But in Spain, the funeral sector lives by burning quality coffins.
Unfortunately, when the decease chooses cremation. In Spain, they do not offer coffins that when burned are low emissions.
The chamber of the crematorium incinerates and vaporizes all substances. Except for some bone fragments and other non-combustible materials, such as prostheses, jewelry, metal parts, nails, etc.
The skeleton of the deceased when the organic matter burns reduce to bone fragments and particles (not ashes), called cremation remains. Metal scraps are selectively collected for recycling.
The ash refining process can be simultaneous to another cremation. it carries out in an attached chamber without the possibility of mixing ashes. The whole non-combustible matter separates or removes from bone fragments by magnetic or visible separation.
This non-combustible material is disposed of by the crematorium so that it is not recoverable. The bone particles vary in size and shape. They mechanically process to a workable consistency for placement in an urn.
The remains in the form of ashes resulting from the incineration process will weigh approximately between 2 and 4 kilos. The ashes that are delivered to the family at the end of the process do not contain any toxic elements.
Generally, the ashes are processed by mechanical grinding to give them a more uniform texture and appearance.
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Emissions treatment and filtration
The norm that regulates the emissions of cremation furnaces requires not exceeding 10 milligrams per cubic meter of air of solid particles in suspension per furnace per day. 10 milligrams per cubic meter of hydrocarbons, nor 10 milligrams per cubic meter of chlorinated compounds, especially hydrochloric acid, all of them very low and that require purification systems to be achieved.
This in theory forces crematorium manufacturing companies to have the equipment to reduce the toxic burden of emissions from these.
The most common technologies that we find in filtration systems are co-flow, solid-bed, catalytic adsorbent with honeycomb filters, dry scrub, and gas scrubbers (according to the commercial terminology of the sector).
Toxic gases from the crematorium
The mercury emissions originate from dental braces that may contain from 5 to 10 grams of mercury, according to the quantity and types used.
The environmental impact of this element emitted from crematoria has been widely studied. Since 1999, most dental fillings no longer use mercury and are based on organic materials.
Particulate control devices remove heavy metals except for mercury. Selenium salt removes mercury in the cremation chamber It can also be done by adding charcoal to particle control devices.
The COVNM (volatile organic compounds not metanoides) are produced from the incomplete or inefficient combustion of hydrocarbons contained in the fuel, the tissues of the deceased, and paddings and varnishes coffin. NMVOCs are reduced through proper use and adjustment of the crematorium, but above all by avoiding burning materials with unnatural elements.
The dioxins and furans are the result of the combustion of wood cellulose, chlorinated plastics and vary the temperature range. Dioxins and furans reduce by reducing chlorinated plastics and employing sufficiently high temperatures and residence times in the secondary combustion chamber.
Neutralize toxic gases
We use a gas filtration system to neutralize highly acidic waste gases and absorb heavy metals, dioxins, and furans in an absorbent medium.
Prior to the filtration system, there is equipment for the cooling of the furnace gases that can provide energy savings, either in the form of hot water production for air conditioning, or reduce the fuel consumption of the furnace.
After the cooling period, the resulting ash removes from the chamber with special brushes, rakes, and other equipment. Every effort is made to remove all unburn debris.
A small amount of residue can remain within the cremation chamber. It removes when the oven’s operability allows.
Most pollutants, but heavy metals minimize by proper operation of the crematorium along with the appropriate temperature and residence time in the secondary combustion chamber.
The formation of dioxins and furans minimize by a good design of the combustion gas circuit, reducing the deposition of particles and avoiding the temperature range in which dioxins and furans form (from 200 to 450 ºC). Dioxins and furans are 0.2% of the gases emitted in a cremation.
Emissions minimize by using eco-friendly caskets with natural woods, water-based varnishes, and cotton textile padding. We should avoid wood with chipboards and organic gloss varnishes.
If we compare the pollution of a crematorium to a private car that meets the Euro 4 2005 anti-pollution standards according to 98/69 / EC and 2002/80 / EC, is the same as a vehicle that performs an average of 15,000 km in one year.
In this case, if we imagine that all crematories equip in accordance with the standards for the protection of air quality required by the EU. Then their sum of the emissions into the atmosphere of a single crematorium would be equal to:
- to the pollution of 132 cars in terms of nitrogen oxides.
- then 5 cars in terms of CO (carbon monoxide), and
- of a car in terms of particles.
The number of emissions for a crematorium according to these data could be below. If we equip the cremators with decontamination systems.
Unfortunately, most of the crematories built do not have filtration equipment adapted to European regulations.