TECHNICAL FIELD
[0001] The invention relates to a device for incinerating waste materials, in particular
hazardous waste materials, and to a method for incinerating said hazardous waste materials.
PRIOR ART
[0002] The incineration of waste materials has long been a proven method of processing waste.
This happens, for example, in rotary kilns. The rotary kilns are used in a continuous
process and are therefore quite efficient. Generated heat is used for the production
of steam, which in turn has further practical applications for heating homes and for
the production of electricity.
[0003] Such rotary kilns are used for incinerating hazardous waste. A disadvantage of incinerating
hazardous waste is that different hazardous waste materials cannot necessarily be
supplied together because in certain cases they can react very violently with each
other or because the hazardous waste materials are not compatible with each other.
In such cases it is necessary to first burn a first hazardous waste material completely
in the rotary kiln, after which a second hazardous waste material can only be supplied
for incineration in the rotary kiln. Because the first hazardous waste material was
completely burned up, there is no longer a continuous process, and the incineration
of the hazardous waste is less efficient. Another possible disadvantage is that a
hazardous waste material does not have a high calorific value, so that insufficient
heat is produced to achieve complete combustion of the hazardous waste. In that case,
it is necessary to introduce an auxiliary fuel into the rotary kiln in order to burn
the hazardous waste completely, further reducing the efficiency of the incineration.
[0004] CN111306549 describes a green and efficient method for incinerating hazardous waste in a rotary
kiln. This known method has the disadvantage that the flow rate of liquid waste materials
introduced into a post-combustion chamber cannot be accurately controlled, which can
lead to a loss of efficiency.
[0005] CN104501178 concerns a system for incinerating hazardous industrial waste, comprising a rotary
kiln. The disadvantage of this system is that only flue gases from the rotary kiln
are led to a post-combustion chamber, so that possibly hazardous waste materials are
not completely incinerated and are discharged from the rotary kiln via the ashes.
[0006] The present invention aims to solve at least some of the above problems or drawbacks.
SUMMARY OF THE INVENTION
[0007] In a first aspect, the present invention relates to a device according to claim 1.
[0008] An advantage of this device is that the device comprises at least one injection lance
for direct injection of liquid waste into the post-combustion chamber. As a result,
two hazardous wastes that cannot be supplied together via the feed hopper, for example
because the hazardous wastes are reactive with each other or are incompatible with
each other, can still be incinerated simultaneously because a first hazardous waste
is incinerated via the feed hopper in the rotary kiln and a second hazardous waste
is atomized via the at least one injection lance in the post-combustion chamber. Because
the first hazardous waste has already largely been incinerated in the rotary kiln
and the second hazardous waste is immediately incinerated, the two hazardous wastes
cannot react with each other. It is therefore not necessary to first burn a first
hazardous waste completely in the rotary kiln in order to subsequently burn the second
hazardous waste in the rotary kiln. An additional advantage is that if a first hazardous
waste has insufficient calorific power, a second hazardous waste can be atomized in
the post-burning chamber, in order to increase the calorific power and to achieve
complete combustion of both hazardous wastes in the post-burning chamber.
[0009] Preferred embodiments of the device are set out in claims 2-9.
[0010] A specific preferred embodiment concerns a device according to claim 3.
[0011] This preferred embodiment is advantageous because a flow rate of liquid waste can
be regulated by regulating the flow rate of the gas to the at least one injection
lance. A control valve for gas can be controlled accurately, while a control valve
in a liquid waste supply line is more subject to wear from the liquid waste and can
therefore leak or get blocked and can also be controlled less accurately. Accurately
controlling the flow rate of the liquid waste results in a more efficient incineration
of the hazardous waste in the post-combustion chamber.
[0012] In a second aspect, the present invention relates to a method according to claim
10. This method has the advantage, among other things, that two hazardous wastes that
react with each other or that are not compatible with each other can be incinerated
simultaneously, because the first hazardous waste has already largely been incinerated
in the rotary kiln and the second hazardous waste is incinerated immediately after
atomization in the post-combustion chamber. An additional advantage of the method
is that the incineration of hazardous waste can be carried out as a continuous process,
because a first hazardous waste does not have to be completely incinerated before
a second hazardous waste is incinerated, resulting in a more efficient incineration
of the hazardous waste. The method is also advantageous in case a first hazardous
waste has insufficient calorific power to burn completely. By adding a second hazardous
waste in the post-combustion chamber, the calorific power in the post-combustion chamber
is increased, so that both hazardous wastes burn completely, without or with only
a minimal addition of auxiliary fuel. This results in a much more efficient incineration
of the hazardous waste.
[0013] Preferred embodiments of the method are described in the dependent claims 11-14.
[0014] In a third aspect, the present invention relates to metals which have been recovered
after incineration of hazardous waste by means of a device according to the first
aspect or a method according to the second aspect.
[0015] Many hazardous wastes are supplied in metal drums and placed in the feed hopper in
these metal drums. After the hazardous waste has been incinerated, these metal drums
remain in ashes. By melting down these metal drums, these metals can be recovered,
so that the incinerated hazardous waste has an additional economic value. An additional
advantage is that these metal drums do not have to be landfilled, which can be harmful
to the environment.
DESCRIPTION OF THE FIGURES
[0016] Figure 1 shows a schematic representation of a device according to an embodiment of the present
invention.
DETAILED DESCRIPTION
[0017] Unless otherwise defined, all terms used in the description of the invention, including
technical and scientific terms, have the meaning as commonly understood by a person
skilled in the art to which the invention pertains. For a better understanding of
the description of the invention, the following terms are explained explicitly.
[0018] In this document, "a" and "the" refer to both the singular and the plural, unless
the context presupposes otherwise. For example, "a segment" means one or more segments.
[0019] The terms "comprise," "comprising," "consist of," "consisting of," "provided with,"
"include", "including", "contain", "containing", are synonyms and are inclusive or
open terms that indicate the presence of what follows, and which do not exclude or
prevent the presence of other components, characteristics, elements, members, steps,
as known from or disclosed in the prior art.
[0020] Quoting numerical intervals by endpoints comprises all integers, fractions and/or
real numbers between the endpoints, these endpoints included.
[0021] Atomization in the context of this document means the transformation of a bulk liquid
into a mist of liquid droplets in a surrounding gas.
[0022] In the context of this document, a waste is pasty if a waste has a consistency similar
to a paste, dough or gruel.
[0023] A hazardous waste is an industrial or medical waste that is harmful to the environment
and/or to human health according to Regulation 1272/2008 of the European Union.
[0024] In a first aspect, the invention relates to a device for incinerating hazardous solid
waste.
[0025] According to a preferred embodiment, the device comprises a rotary kiln, a feed hopper
for supplying waste materials to the rotary kiln, a post-combustion chamber, a steam
boiler and a gas scrubbing installation.
[0026] An outlet of the feed hopper is located on an inlet of the rotary kiln or connected
to the inlet of the rotary kiln. For example, the outlet of the feed hopper is connected
to the inlet of the rotary kiln by means of a ramp or a conveyor belt. A feed hopper
is suitable for supplying preferably solid hazardous waste. It will be apparent to
one skilled in the art that, depending on the design, a feed hopper can also be used
for liquid and/or pasty hazardous wastes, if the liquid and/or pasty hazardous wastes
are packaged.
[0027] The rotary kiln extends along a longitudinal axis. The rotary kiln is rotatable about
the longitudinal axis. The rotary kiln is set up at an angle, with the longitudinal
axis at an angle to a horizontal plane. The longitudinal axis has a first end and
a second end, the first end being higher than the second end. The inlet of the rotary
kiln is located at the first end of the longitudinal axis. The rotary kiln has an
outlet at the second end of the longitudinal axis. A rotary kiln is advantageous for
mixing and churning hazardous waste, so that complete incineration of the hazardous
waste is achieved. Because the rotary kiln is set up at an angle, the contents of
the kiln move under the influence of gravity towards the outlet of the rotary kiln.
[0028] The outlet of the rotary kiln preferably leads directly to the post-combustion chamber.
This is advantageous for automatically introducing combustion products from the rotary
kiln into the post-combustion chamber and for limiting calorific losses. The combustion
products typically comprise 10% to 22% bottom ash and 78% to 90% flue gases. The flue
gases typically comprise 3% to 5% boiler and fly ash. Due to heat in the post-combustion
chamber, residual hazardous waste from the rotary kiln continues to burn. A complete
incineration of the hazardous waste from the rotary kiln is achieved.
[0029] The device comprises at least one injection lance for direct injection of liquid
waste into the post-combustion chamber. Preferably, the device comprises at least
two injection lances, more preferably at least three injection lances for direct injection
into the post-combustion chamber. It will be apparent to one skilled in the art that
each injection lance can inject a different hazardous waste or that each injection
lance can inject the same hazardous waste directly into the post-combustion chamber.
It will also be apparent that an injection lance can inject a traditional auxiliary
fuel into the post-combustion chamber. The at least one injection lance is advantageous
for simultaneous incineration of two hazardous wastes that cannot be supplied together
via the feed hopper, for example because the hazardous wastes are reactive with each
other or are incompatible with each other. Because a first hazardous waste is largely
incinerated in the rotary kiln via the feed hopper and a second hazardous waste is
atomized via the at least one injection lance directly in the post-combustion chamber
and immediately burns, the two hazardous wastes cannot react with each other. An additional
advantage is that it is not necessary to burn a first hazardous waste completely in
the rotary kiln in order to subsequently burn the second hazardous waste in the rotary
kiln. It is also very advantageous that if a first hazardous waste has insufficient
calorific power to maintain a high temperature in the post-combustion chamber, a second
hazardous waste can be atomized in the post-burning chamber, in order to increase
the calorific power and to achieve complete combustion of both hazardous wastes in
the post-burning chamber. In this case, no or only a minimal amount of auxiliary fuel
is supplied, so that a higher efficiency can be achieved in the incineration of hazardous
waste.
[0030] The post-combustion chamber comprises an outlet for flue gases. The flue gas outlet
of the post-combustion chamber is connected to an inlet of the steam boiler. The steam
boiler comprises a heat exchanger for generating steam. To this end, heat is extracted
from the flue gases.
[0031] The steam boiler comprises an outlet for flue gases. The flue gas outlet of the steam
boiler is directly or indirectly connected to an input of the gas scrubbing installation.
The gas scrubbing installation comprises a first section for cooling the flue gases
by injection of scrubbing water. The gas scrubbing installation comprises a second
section of the gas scrubbing installation for scrubbing the flue gases with scrubbing
water from the first section. The second section comprises a supply of milk of lime
(Ca(OH)
2) to regulate the acidity of the flue gases. The gas scrubbing installation comprises
a third section for SO
2 removal. The third section comprises a feed for NaOH for controlling the acidity
of the flue gases.
[0032] According to an embodiment, the device comprises a bunker for solid hazardous waste.
The device comprises a movable crane with a gripper arm for grabbing solid hazardous
waste and placing solid hazardous waste in the feed hopper of the device. The movable
crane can be moved between the bunker and the feed hopper.
[0033] Preferably, the bunker and the feed hopper are placed in the same building. A bunker
is advantageous for safe and temporary storage of solid hazardous waste.
[0034] According to a preferred embodiment, the device comprises at least one storage tank
for the storage of liquid hazardous waste. An outlet of the at least one storage tank
is connected to the at least one injection lance via a supply line. If there are multiple
storage tanks, preferably all storage tanks are connected to the at least one injection
lance via one or more supply lines. Preferably, each storage tank is connected to
the at least one injection lance with a separate supply line, with a collector for
the supply lines being placed on the at least one injection lance. If there are several
injection lances, the at least one storage tank is preferably connected to all injection
lances via one or more supply lines. If there are several injection lances and several
storage tanks, all storage tanks are preferably connected to all injection lances
via one or more supply lines. Preferably, the storage tanks and/or the supply lines
and/or the injection lances comprise shut-off valves so that connections between storage
tanks and injection lances can be shut off. Storage tanks are advantageous for the
temporary safe storage of liquid hazardous substances.
[0035] The supply line comprises a pump. The pump is suitable for pumping the liquid hazardous
liquid from the at least one storage tank to the at least one injection lance.
[0036] Preferably, the supply line comprises a filter.
[0037] The device comprises a return line from the at least one injection lance to the at
least one storage tank. If there are several storage tanks, the device preferably
comprises one or more return lines from the at least one injection lance to all storage
tanks. The device preferably comprises a separate return line from the at least one
injection lance to each storage tank, a collector for the return lines being placed
on the at least one injection lance. If there are several injection lances, the device
preferably comprises one or more return lines from all injection lances to the at
least one storage tank. If there are several injection lances and several storage
tanks, the device preferably comprises one or more return lines from all injection
lances to all storage tanks. Preferably, the return lines comprise shut-off valves
so that return lines between storage tanks and injection lances can be shut off. This
is advantageous in order to prevent liquid hazardous waste from a first storage tank
ending up via a return line in a second storage tank with another liquid hazardous
waste, possibly causing an undesirable reaction. Supply lines and return lines between
a first storage tank and a second storage tank are preferably separated in order to
avoid possible mixing of liquid hazardous waste from the first storage tank and liquid
hazardous waste from the second storage tank.
[0038] A return line comprises a control valve. A control valve comprises a controller for
controlling the control valve. The device comprises a pressure sensor for measuring
pressure in the supply line and/or return line. The controller of the control valve
is coupled to said pressure sensor. In this context, coupled means that the controller
can directly or indirectly receive measured values from said pressure sensor and/or
can read them directly or indirectly.
[0039] This embodiment is advantageous for obtaining a constant pressure at an entry point
of the at least one injection lance. This pressure may vary, for example, by a changing
level in the at least one storage tank, by a pressure difference across the filter
in the supply line, by a varying flow through the injection lance, etc. A varying
pressure at the entry point of the at least one injection lance results in a varying
direct injection of hazardous waste into the post-combustion chamber, resulting in
an irregular supply and combustion in the post-combustion chamber. Compensating the
varying pressure at the entry point of the at least one injection lance by controlling
the pump in the supply line is too slow for accurate compensation because it requires
changing the speed of the pump. A control valve, on the other hand, can open or close
almost immediately, completely or partially, so that if the pressure at the entry
point of the at least one injection lance is too high or too low, more or less liquid
hazardous waste can flow back to the at least one storage tank, thereby minimizing
pressure variations at the entry point of the at least one injection lance.
[0040] According to an embodiment, the device comprises a storage tank for chlorofluorocarbons
(CFCs). The storage tank for CFCs is a fixed storage tank or a temporary movable storage
tank. CFCs are gases that are hazardous to the environment and are responsible for
the hole in the ozone layer. Freon
® is the best known CFC. The storage tank is connected by a supply line to the at least
one injection lance. It will be apparent to one skilled in the art that in the case
of a temporary mobile storage tank, the supply line between the storage tank for CFCs
and the at least one injection lance can be disconnected at least at the level of
the storage tank for CFCs. CFCs are suitable to be injected directly into the post-combustion
chamber as a hazardous waste.
[0041] According to a preferred embodiment, the device comprises a supply line with lifting
device for feeding drums to the feed hopper. The device comprises a storage space
for drums. The supply line with lifting device connects the storage space with the
feed hopper. The supply line with lifting device comprises near the feed hopper a
piercing means, such as for instance pins or cutters, for piercing the drums so that
the drums do not explode during combustion in the rotary kiln. Hazardous waste is
often transported in drums. This embodiment is advantageous because the drums do not
have to be opened and emptied manually, which limits the risk of accidents.
[0042] According to an embodiment, the device comprises a connection point. The connection
point is connected to the at least one injection lance by a supply line. The connection
point is advantageous for connecting, for example, a tanker to the at least one injection
lance. This allows hazardous waste from the tanker to be injected directly into the
post-combustion chamber.
[0043] According to a preferred embodiment, the injection lance comprises a longitudinal
supply channel for the supply of liquid waste. The longitudinal supply channel extends
from an opening at a first end of the injection lance to an opening at an opposite
second end of the injection lance. The opening at the first end is an entry point
for the injection lance. The opening at the second end is an exit point of the injection
lance. Concentrically around the supply channel, the injection lance comprises a gas
channel for supplying a gas. The gas channel also extends from an opening at the first
end to the second end. The gas channel comprises at the second end at least six outlet
openings for distributing the gas, preferably at least eight outlet openings, more
preferably at least ten outlet openings and even more preferably at least twelve outlet
openings. The outlet openings are preferably distributed evenly over a circumference
around the supply channel. The gas is preferably an inert gas. Non-limiting examples
of gases are nitrogen gas, compressed air and steam. A spray head is placed on the
injection lance. The spray head is placed on the injection lance at the second end.
The spray head comprises an internal mixing chamber. The supply channel and the gas
channel open into the internal mixing chamber.
[0044] An injection lance with a gas channel around a supply channel is advantageous for
cooling the liquid waste materials during transport through the injection lance, for
instance by means of nitrogen gas or compressed air. This is advantageous, for example,
for cooling the injection lance itself in order to prevent the injection lance from
being damaged by heat in the post-combustion chamber.
[0045] An injection lance with a gas channel around a supply channel is advantageous for
heating the liquid waste during transport through the injection lance, for instance
by means of steam. This is particularly advantageous in case the liquid wastes are
very viscous or solidify easily in order to prevent the liquid wastes from blocking
the supply channel.
[0046] The mixing chamber is advantageous for mixing the liquid waste with the gas. As a
result, a mist of the liquid waste is formed. The at least six outlet openings are
advantageous for an optimal distribution of the gas in the mixing chamber. By atomizing
the liquid waste, the liquid waste is uniformly distributed in the post-combustion
chamber, as a result of which an even combustion of the liquid waste takes place in
the post-combustion chamber.
[0047] According to a further embodiment, the device comprises sensors for measuring the
temperature, flow rate and density of liquid hazardous waste to the at least one injection
lance in the active state of the device. The sensors may or may not be wholly or partially
combined. The device further comprises a control valve for controlling a flow rate
of the gas to the gas channel. The control valve comprises a controller for controlling
the control valve. The controller of the control valve is coupled to the said sensors.
In this context, coupled means that the controller of the control valve can directly
or indirectly receive measured values from said sensors and/or can read them directly
or indirectly.
[0048] This preferred embodiment is advantageous because a flow rate of liquid waste can
be regulated by regulating the flow rate of the gas to the at least one injection
lance. A control valve for gas can be controlled accurately, while a control valve
in a liquid waste supply line is more subject to wear from the liquid waste and can
therefore leak or get blocked and can also be controlled less accurately. By regulating
the flow rate of the gas, the mixing chamber is filled more or less with gas and less
or more with wastes. The required gas flow rate for atomizing the liquid waste depends
on the flow rate, the temperature and the density of the liquid waste. Accurately
controlling the flow rate of the liquid waste results in a more efficient incineration
of the hazardous waste in the post-combustion chamber. This embodiment is also advantageous
for avoiding flashback in the at least one injection lance. Possible flashback can
be avoided by throttling the mixing chamber with gas.
[0049] This embodiment can be advantageously combined with a previously described embodiment
in which the device comprises at least one storage tank, a supply line and a return
line, for obtaining a regular supply and combustion of the liquid waste in the post-combustion
chamber.
[0050] According to an embodiment, the device comprises a water purification installation
for purifying the scrubbing water from the gas scrubbing installation. This water
may still contain dust, as well as metal salts and mercury and therefore cannot be
discharged. By purifying the water in the water purification installation, the scrubbing
water is dischargeable.
[0051] According to a preferred embodiment, the device comprises an electrofilter for filtering
flue gases from the steam boiler. The electrofilter is a dry electrofilter. This is
advantageous because no water is polluted, which has to be purified. The electrofilter
is advantageous for removing fly ash from flue gases leaving the steam boiler. Up
to 85%, preferably 90%, more preferably 95% and even more preferably 99.5% of the
fly ash is removed from the flue gases. The electrofilter is preferably placed between
the steam boiler and the gas scrubbing installation.
[0052] According to a further embodiment, the device comprises an outlet for recuperating
fly ash from the electrofilter. Fly ash is still a hazardous inorganic substance that
requires further treatment and then safe storage.
[0053] According to a preferred embodiment, the post-combustion chamber comprises an outlet
for recovery of bottom ash. Bottom ash comprises still usable metals from metal drums
in which hazardous waste was introduced into the feed hopper. These metals can be
recovered from the bottom ash. By recovering these metals, these metals can be reused,
so that the incinerated hazardous waste has an additional economic value. An additional
advantage is that these metals do not have to be landfilled, which can be harmful
to the environment.
[0054] According to an embodiment, the steam boiler comprises an outlet for recovery of
boiler dust.
[0055] According to a preferred embodiment, the device comprises a urea tank. The urea tank
is connected to the steam boiler via a supply line. This embodiment is advantageous
for feeding urea into the steam boiler, as a result of which an amount of NOx in the
flue gases from the steam boiler is reduced. Nitrogen oxides are reduced to nitrogen
gas. The reduction proceeds according to a selective non-catalytic reduction. Simplified,
the reduction can be written as 4 NO + 4 NH
3 + O
2 → 4 N
2 + 6H
2O.
[0056] According to an embodiment, the device comprises a dioxin filter. The dioxin filter
is preferably placed after the gas scrubbing installation. The dioxin filter comprises
a lignite filter. A lignite filter is beneficial for removing dioxins from flue gases,
but also for removing furans, mercury and other heavy metals.
[0057] According to an embodiment, the steam boiler is coupled to a heat network. This is
advantageous for using the steam produced for industrial applications or for heating
industrial and residential buildings. The steam produced can also be used as an inert
gas as in a previously described embodiment.
[0058] According to an embodiment, the steam boiler is coupled to a turbine. This is advantageous
for using produced steam to produce electricity. The electricity produced can be used
in the device, as well as externally for industrial and residential applications.
[0059] According to an embodiment, the device comprises an induced draught fan. The induced
draught fan is preferably placed between the dioxin filter of a previously described
embodiment and the gas scrubbing installation. An induced draught fan is advantageous
for a good flow of flue gases from the rotary kiln to the gas scrubbing installation
and from the gas scrubbing installation to the dioxin filter. Due to the induced draught
fan, there is an underpressure in the device from the rotary kiln to the gas scrubbing
installation and an overpressure from the gas scrubbing installation.
[0060] According to an embodiment, the device comprises at least one secondary injection
lance for direct injection of hazardous liquid waste into the rotary kiln. Preferably,
the device comprises at least two secondary injection lances, more preferably at least
three secondary injection lances for direct injection into the rotary kiln. The secondary
injection lances are preferably located at the first end of the rotary kiln. The secondary
injection lances are advantageous for injecting liquid hazardous wastes directly into
the rotary kiln that do not react very violently with hazardous solid wastes or with
packaged liquid and/or pasty hazardous wastes supplied via the feed hopper, so that
these liquid hazardous wastes can be incinerated in the rotary kiln together with
the hazardous solid waste or the packaged liquid and/or pasty hazardous waste. This
is also advantageous for increasing the calorific power in the rotary kiln if the
hazardous solid waste or the packaged liquid and/or pasty hazardous waste has a limited
calorific value, as a result of which the hazardous solid waste or the packaged liquid
and/or pasty hazardous waste burn better in the rotary kiln. It will be apparent to
one skilled in the art that the calorific power in the rotary kiln can also be increased
by directly injecting an auxiliary fuel into the rotary kiln. It will be apparent
to one skilled in the art that previously described embodiments about injection lances
for direct injection of liquid waste into the post-combustion chamber also apply mutatis
mutandis to secondary injection lances.
[0061] According to an embodiment, the device comprises at least one tertiary injection
lance for direct injection of pasty hazardous wastes into the rotary kiln. The tertiary
injection lances are preferably located at the first end of the rotary kiln. The tertiary
injection lances are advantageous for injecting liquid hazardous wastes directly into
the rotary kiln that do not react very violently with hazardous solid wastes or with
packaged liquid and/or pasty hazardous wastes supplied via the feed hopper, so that
these pasty hazardous wastes can be incinerated in the rotary kiln together with the
hazardous solid waste or the packaged liquid and/or pasty hazardous waste. This is
also advantageous for increasing the calorific power in the rotary kiln if the hazardous
solid waste or the packaged liquid and/or pasty hazardous waste has a limited calorific
value, as a result of which the hazardous solid waste or the packaged liquid and/or
pasty hazardous waste burn better in the rotary kiln.
[0062] In a second aspect, the invention relates to a method for incinerating hazardous
solid waste.
[0063] In a preferred embodiment the method comprises the steps of:
- placing hazardous waste in a feed hopper;
- feeding from the feed hopper of the hazardous waste into a rotary kiln;
- incineration of the hazardous waste in the rotary kiln;
- post-burning of incinerated hazardous waste from the rotary kiln in a post-combustion
chamber;
- generating steam in a steam boiler using hot flue gases from the post-combustion chamber;
- scrubbing of hot flue gases from the steam boiler in a gas scrubbing installation.
[0064] An outlet of the feed hopper is located on an inlet of the rotary kiln or connected
to the inlet of the rotary kiln.
[0065] The rotary kiln extends along a longitudinal axis. The rotary kiln rotates during
the incineration of the hazardous waste. The rotary kiln is set up at an angle, with
the longitudinal axis at an angle to a horizontal plane. The longitudinal axis has
a first end and a second end, the first end being higher than the second end. The
inlet of the rotary kiln is located at the first end of the longitudinal axis. The
rotary kiln has an outlet at the second end of the longitudinal axis. By rotating
the rotary kiln, the hazardous waste is mixed and churned up during incineration,
so that the hazardous waste is burned as completely as possible. The contents of the
kiln moves under the influence of gravity towards the outlet of the rotary kiln.
[0066] The outlet of the rotary kiln preferably opens directly into the post-combustion
chamber, so that combustion products from the rotary kiln are automatically introduced
into the post-combustion chamber. In addition, this limits calorific losses. Due to
heat in the post-combustion chamber, residual hazardous waste from the rotary kiln
continues to burn in the post-combustion chamber.
[0067] Liquid hazardous waste is injected directly into the post-combustion chamber using
at least one injection lance, preferably using at least two injection lances, more
preferably using at least three injection lances. It will be apparent to one skilled
in the art that each injection lance can inject a different hazardous waste or that
each injection lance can inject the same hazardous waste directly into the post-combustion
chamber. It will also be apparent that an injection lance can inject a traditional
auxiliary fuel into the post-combustion chamber. The liquid hazardous waste is atomized
by the at least one injection lance when it is injected directly into the post-combustion
chamber. The direct injection of liquid hazardous waste is particularly advantageous
because two hazardous wastes that react with each other or that are not compatible
with each other can be incinerated simultaneously, because a first hazardous waste
has already largely been incinerated in the rotary kiln and a second hazardous waste
is incinerated immediately after atomization in the post-combustion chamber, as a
result of which the first hazardous waste and the second hazardous waste cannot react
with each other. An additional advantage of the method is that the incineration of
hazardous waste can be carried out as a continuous process, because a first hazardous
waste does not have to be completely incinerated before a second hazardous waste is
incinerated, resulting in a more efficient incineration of the hazardous waste. The
method is also advantageous in case a first hazardous waste has insufficient calorific
power to burn completely, in other words if the combustion of the first hazardous
waste generates insufficient heat to maintain a high temperature in the post-combustion
chamber to completely burn residues of the first hazardous waste in the post-combustion
chamber. By adding a second hazardous waste in the post-combustion chamber, the calorific
power in the post-combustion chamber is increased, so that both hazardous wastes burn
completely, without or with only a minimal addition of auxiliary fuel. This results
in a much more efficient incineration of the hazardous waste.
[0068] The post-combustion chamber comprises an outlet for flue gases. The flue gas outlet
of the post-combustion chamber is connected to an inlet of the steam boiler. The hot
flue gases from the post-combustion chamber flow through the steam boiler. The steam
boiler comprises a heat exchanger for generating steam. To this end, heat is extracted
from the flue gases.
[0069] The steam boiler comprises an outlet for flue gases. The flue gas outlet of the steam
boiler is directly or indirectly connected to an input of the gas scrubbing installation.
The hot flue gases from the steam boiler are cooled in a first section of the gas
scrubbing installation by injection of scrubbing water. The flue gases are then scrubbed
in a second section with the scrubbing water from the first section. To this end,
milk of lime (Ca(OH)
2) is added to regulate the acidity of the flue gases. In a third section, the flue
gases are scrubbed again to remove SO
2. To this end, NaOH is added to regulate the acidity of the flue gases.
[0070] According to a preferred embodiment, the method comprises the additional step of
measuring temperature, flow rate and density of the liquid hazardous waste to the
at least one injection lance. The at least one injection lance comprises a longitudinal
supply channel for the supply of liquid or pasty hazardous waste. Concentrically around
the supply channel, the at least one injection lance comprises a gas channel for supplying
a gas. The gas is preferably an inert gas. Non-limiting examples of gases are nitrogen
gas, compressed air and steam. A spray head is placed on the injection lance. The
spray head comprises an internal mixing chamber. The supply channel and the gas channel
open into the internal mixing chamber.
[0071] The flow rate of the liquid hazardous waste is controlled by regulating a pressure
of the gas to said gas channel with the aid of a control valve on the basis of the
measured temperature, flow rate and density.
[0072] This is advantageous because a control valve for gas can be controlled accurately,
while a control valve in a liquid waste supply line is more subject to wear from the
liquid waste and can therefore leak or get blocked and can also be controlled less
accurately. By regulating the flow rate of the gas, the mixing chamber is filled more
or less with gas and less or more with liquid waste. The required gas flow rate for
atomizing the liquid waste depends on the flow rate, the temperature and the density
of the liquid waste. Accurately controlling the flow rate of the liquid waste results
in a more efficient incineration of the hazardous waste in the post-combustion chamber.
This embodiment is also advantageous for avoiding flashback in the at least one injection
lance. Possible flashback can be avoided by throttling the mixing chamber with gas.
[0073] According to a preferred embodiment, the liquid hazardous waste is supplied from
a storage tank to the at least one injection lance via a supply line with the aid
of a pump comprised in the supply line. Part of the liquid hazardous waste is returned
to the storage tank via a return line from the at least one injection lance. A pressure
in the supply line and/or return line is measured. A control valve comprised in the
return line is controlled in such a way that a constant pressure is obtained at the
least one injection lance.
[0074] This embodiment is advantageous for obtaining a constant pressure at an entry point
of the at least one injection lance. The pressure measured in the supply line and/or
return line is a measure of the pressure at the entry point of the at least one injection
lance. It is assumed here that pressure losses between the point where the pressure
is measured in the supply line and/or return line and the entry point of the at least
one injection lance are constant. The pressure at the entry point of the at least
one injection lance can vary, for example, due to a changing level in the at least
one storage tank, due to a varying flow through the injection lance, etc. A varying
pressure at the entry point of the at least one injection lance results in a varying
direct injection of hazardous waste into the post-combustion chamber, resulting in
an irregular supply and combustion in the post-combustion chamber. Compensating the
varying pressure at the entry point of the at least one injection lance by controlling
the pump in the supply line is too slow for accurate compensation because it requires
changing the speed of the pump. A control valve, on the other hand, can open or close
almost immediately, completely or partially, so that if the pressure at the entry
point of the at least one injection lance is too high or too low, more or less liquid
hazardous waste can flow back to the at least one storage tank, thereby minimizing
pressure variations at the entry point of the at least one injection lance.
[0075] According to a preferred embodiment, the various hazardous wastes are tested for
reactivity and compatibility before incineration of various hazardous wastes.
[0076] The hazardous waste is mixed with different products before incineration. These are,
for example, water as a solvent, HCl as an acid, NaOH as a base, a polar solvent such
as acetone, a halogenated solvent such as CH
2Cl
2, an apolar solvent such as hexane. It is tested whether there are temperature rises,
whether there is gas formation, whether there is precipitation, ... both during and
after mixing. This is important in order to determine whether mutual reactions can
be expected if different hazardous wastes are introduced into the rotary kiln at the
same time.
[0077] Different hazardous wastes are also brought into contact with each other. Incompatible
hazardous waste will then react with each other, mix or just separate. Mixing or separating
is important because it can affect the even and complete incineration of the hazardous
waste.
[0078] If it is determined that a first and a second hazardous waste are non-reactive and
compatible, they may be simultaneously introduced into the rotary kiln, allowing the
first hazardous waste and the second hazardous waste to be incinerated simultaneously.
[0079] This is also advantageous when determining an optimum operating point for a device
for the incineration of hazardous waste using a combustion diagram. A combustion diagram
shows on the X-axis a quantity of hazardous waste that is processed per hour in the
device and on the Y-axis a thermal load on the device. This is preferably expressed
in tons/h. The thermal load corresponds to an amount of heat released by the incineration
of the hazardous waste. This is preferably expressed in MW. A combustion diagram is
basically a rectangle. A corner point at the bottom left is determined by a minimum
amount of hazardous waste that must be incinerated and the minimum amount of heat
that must be released in order to have a cost-effective installation, so that sufficient
steam and electricity are produced, and the hazardous waste can be incinerated at
an acceptable cost. A corner point at the top right is determined by a maximum amount
of hazardous waste that can be incinerated in the device and a maximum amount of heat
that may be released in order not to damage the device. Typically, a combustion diagram
is cut off by two oblique lines. A first slanted line cuts off a corner at the top
left. This is due to a first hazardous waste with a calorific value, the amount of
heat released during combustion expressed in kJ/kg, which is sufficiently large, so
that before the maximum amount of hazardous waste that can be incinerated in the device
is reached, the maximum amount of heat that is permitted for the device is already
released. A second slanted line cuts off a corner at the bottom right. This is due
to a second hazardous waste with a calorific value that is so small that, only with
an amount of the second hazardous waste that exceeds the minimum amount of hazardous
waste that must be incinerated, an amount of heat is obtained that is equal to the
minimum amount of heat which must be released during combustion. Preferably, an operating
point of the device is as close as possible to the top right corner point. By determining
the calorific value of various hazardous wastes and by determining whether the various
hazardous wastes are reactive and compatible, a mixture of various hazardous wastes
can be determined that are non-reactive and compatible and where the operating point
of the device is as close as possible to the top right corner point.
[0080] According to a preferred embodiment, metals are recovered from bottom ash from the
post-combustion chamber. Bottom ash still comprises usable metals. These metals come
from metal drums in which hazardous waste is introduced into the feed hopper. By recovering
these metals, these metals can be reused, so that the incinerated hazardous waste
has an additional economic value. An additional advantage is that these metals do
not have to be landfilled, which can be harmful to the environment.
[0081] According to an embodiment, the method comprises the additional step of filtering
hot flue gases from the steam boiler using an electrofilter. The hot flue gases are
preferably filtered in the gas scrubbing installation before scrubbing the hot flue
gases. The electrofilter is advantageous for removing fly ash from flue gases leaving
the steam boiler. Up to 85%, preferably 90%, more preferably 95% and even more preferably
99.5% of the fly ash is removed from the flue gases.
[0082] According to an embodiment, liquid hazardous waste is injected directly into the
rotary kiln using at least one injection lance, preferably using at least two injection
lances, more preferably using at least three injection lances. It will be apparent
to one skilled in the art that each injection lance can inject a different hazardous
waste or that each injection lance can inject the same hazardous waste directly into
the rotary kiln. It will also be apparent that an injection lance can inject a traditional
auxiliary fuel into the rotary kiln. The liquid hazardous waste is atomized by the
at least one injection lance when it is injected directly into the rotary kiln. This
embodiment is advantageous for injecting liquid hazardous wastes directly into the
rotary kiln that do not react very violently with hazardous solid wastes or with packaged
liquid and/or pasty hazardous wastes supplied via the feed hopper, so that these liquid
hazardous wastes can be incinerated in the rotary kiln together with the hazardous
solid waste or packaged liquid and/or pasty hazardous waste. This is also advantageous
for increasing the calorific power in the rotary kiln if the hazardous solid waste
or the packaged liquid and/or pasty hazardous waste has a limited calorific value,
as a result of which the hazardous solid waste or the packaged liquid and/or pasty
hazardous waste burn better in the rotary kiln.
[0083] According to an embodiment, pasty hazardous waste is injected directly into the rotary
kiln using at least one injection lance. This embodiment is advantageous for injecting
pasty hazardous wastes directly into the rotary kiln that do not react very violently
with hazardous solid wastes or with packaged liquid and/or pasty hazardous wastes
supplied via the feed hopper, so that these pasty hazardous wastes can be incinerated
in the rotary kiln together with the hazardous solid waste or packaged liquid and/or
pasty hazardous waste. This is also advantageous for increasing the calorific power
in the rotary kiln if the hazardous solid waste or the packaged liquid and/or pasty
hazardous waste has a limited calorific value, as a result of which the hazardous
solid waste or the packaged liquid and/or pasty hazardous waste burn better in the
rotary kiln.
[0084] One skilled in the art will appreciate that a method according to the second aspect
is preferably performed using a device according to the first aspect and that a device
according to the first aspect is preferably configured for performing a method according
to the second aspect. Each feature described in this document, both above and below,
can therefore relate to any of the three aspects of the present invention.
[0085] In a third aspect, the invention relates to metals recovered after incineration of
hazardous waste by means of a device according to the first aspect or a method according
to the second aspect.
[0086] Many hazardous wastes are supplied in metal drums and placed in the feed hopper in
these metal drums. After the hazardous waste has been incinerated, these metal drums
remain in ashes. By melting down these metal drums, these metals can be recovered,
so that the incinerated hazardous waste has an additional economic value.
[0087] An additional advantage is that these metal drums do not have to be landfilled, which
can be harmful to the environment.
[0088] In what follows, the invention is described by way of non-limiting figures illustrating
the invention, and which are not intended to and should not be interpreted as limiting
the scope of the invention.
DESCRIPTION OF THE FIGURES
[0089] Figure 1 shows a schematic representation of a device according to an embodiment of the present
invention.
[0090] The device (1) comprises a feed hopper (2) for supplying hazardous waste to a rotary
kiln (3). The hazardous waste is transferred from a bunker (13) for the temporary
storage of solid hazardous waste by means of a movable crane with a gripper arm (14)
into the feed hopper (2). The hazardous waste can also be transferred from a drum
storage (15) by a supply line with lifting device in drums into the feed hopper (2).
The device (1) further comprises a connection point for a tanker (10). Liquid hazardous
waste can be temporarily stored from the tanker (10) in a storage tank for liquid
hazardous waste (12). Liquid hazardous waste can be injected from the tanker (10)
via the connection point and supply lines directly into the rotary kiln (3) or preferably
directly into a post-combustion chamber (4). The device (1) comprises a storage tank
for chlorofluorocarbons (11). The chlorofluorocarbon storage tank is a fixed storage
tank or a temporary movable storage tank. The chlorofluorocarbons (11) can be injected
directly into the rotary kiln (3) via supply lines or preferably injected directly
into the post-combustion chamber (4). As already mentioned, the device (1) comprises
at least one storage tank for liquid hazardous waste (12). The liquid hazardous waste
is injected from the storage tank for liquid hazardous waste (12) via supply lines
directly into the rotary kiln (3) or is preferably injected directly into the post-combustion
chamber (4). The hazardous wastes are incinerated in the rotary kiln (3). Under the
influence of gravity, kiln content moves from the rotary kiln (3) to the outlet of
the rotary kiln (3) and ends up in the post-combustion chamber (4). Due to heat in
the post-combustion chamber (4), residual hazardous waste from the rotary kiln (3)
continues to burn in the post-combustion chamber (4). Direct injection of liquid hazardous
waste into the post-combustion chamber (4) increases the calorific power in the post-combustion
chamber (4), so that the hazardous waste burns completely, without or with only a
minimal addition of auxiliary fuel. Hot flue gases from the post-combustion chamber
(4) heat water to steam in a steam boiler (5). The steam can be used for residential
and industrial applications. The steam can also be used to drive a turbine to generate
electrical power. In the steam boiler (5), urea is fed from a urea tank (9), as a
result of which an amount of NOx in the flue gases from the steam boiler (5) is reduced.
The hot flue gases from the steam boiler (5) are filtered in a dry electrofilter (6)
and then scrubbed and filtered in a gas scrubbing installation and dioxin filter (7).
Finally, the flue gases leave the installation (1) through a chimney (9). Bottom ash
(19) from the rotary kiln (2) is discharged through an outlet (16). Boiler dust (20)
from the steam boiler (5) is discharged through an outlet (17). Fly ash (21) from
the electrofilter (6) is discharged through an outlet (18). Metals from the bottom
ash (19), originating from metal drums, are recovered. Scrubbing water (22) from the
gas scrubbing installation (7) is purified in a water purification installation (23).
Residue (24), comprising sludge, is discharged.
[0091] The numbered elements in the figures are:
- 1
- device
- 2
- feed hopper
- 3
- rotary kiln
- 4
- post-combustion chamber
- 5
- steam boiler
- 6
- electrofilter
- 7
- gas scrubbing installation and dioxin filter
- 8
- chimney
- 9
- urea tank
- 10
- tanker
- 11
- storage tank for chlorofluorocarbons
- 12
- storage tank for liquid and/or pasty hazardous waste
- 13
- bunker
- 14
- movable crane with a gripper arm
- 15
- drum storage
- 16
- bottom ash outlet
- 17
- boiler dust outlet
- 18
- fly ash outlet
- 19
- bottom ash
- 20
- boiler dust
- 21
- fly ash
- 22
- scrubbing water
- 23
- water purification installation
- 24
- residues
1. Device for incinerating hazardous solid waste comprising a rotary kiln, a feed hopper
for supplying hazardous waste to the rotary kiln, a post-combustion chamber, a steam
boiler and a gas scrubbing installation, characterized in, that the device comprises at least one injection lance for direct injection of liquid
waste into the post-combustion chamber.
2. Device according to claim 1, characterized in, that the injection lance comprises a longitudinal supply channel for supplying liquid
waste materials, wherein the injection lance comprises a gas channel concentrically
around the supply channel for supplying a gas, wherein a spray head is arranged on
the injection lance, wherein the spray head comprises an internal mixing chamber,
and wherein the supply channel and the gas channel open into the internal mixing chamber.
3. Device according to claim 2, characterized in, that the device comprises sensors for measuring, in the active state of the device, the
temperature, flow rate and density of liquid hazardous waste to the at least one injection
lance, the device further comprising a control valve for regulating the flow rate
of the gas to the gas channel of the at least one injection lance, wherein the control
valve comprises a controller and wherein the controller of the control valve is coupled
to said sensors.
4. Device according to any of the preceding claims 1-3, characterized in, that the device comprises at least one storage tank, wherein an outlet of the at least
one storage tank is connected to the at least one injection lance via a supply line,
wherein the supply line comprises a pump, wherein the device comprises a return line
from the at least one injection lance to the at least one storage tank, wherein the
return line comprises a control valve, wherein the control valve comprises a controller,
and wherein the controller of the control valve is coupled to a pressure sensor for
measuring pressure in the supply line and/or return line.
5. Device according to any of the preceding claims 1-4, characterized in, that the device comprises an electrofilter for filtering flue gases from the steam boiler.
6. Device according to any of the preceding claims 1-5, characterized in, that the device comprises at least one secondary injection lance for direct injection
of liquid waste materials into the rotary kiln.
7. Device according to any of the preceding claims 1-6, characterized in that the post-combustion chamber comprises an outlet for recovery of bottom ash.
8. Device according to any of the preceding claims 1-7, characterized in, that the device comprises a supply line with lifting device for supplying drums to the
feed hopper.
9. Device according to any of the preceding claims 1-8, characterized in, that the device comprises a urea tank, the urea tank being connected to the steam boiler
via a supply line.
10. Method for incinerating hazardous solid waste comprising:
- placing hazardous waste in a feed hopper;
- feeding from the feed hopper of the hazardous waste into a rotary kiln;
- incineration of the hazardous waste in the rotary kiln;
- post-burning of incinerated hazardous waste from the rotary kiln in a post-combustion
chamber;
- generating steam in a steam boiler using hot flue gases from the post-combustion
chamber;
- scrubbing of hot flue gases from the steam boiler in a gas scrubbing installation;
characterized in, that liquid hazardous waste is injected directly into the post-combustion chamber using
at least one injection lance.
11. Method according to claim 10, characterized in, that the method comprises the additional step of measuring the temperature, flow rate
and density of the liquid hazardous waste to the at least one injection lance, wherein
the at least one injection lance comprises a longitudinal supply channel for the supply
of liquid hazardous waste, wherein the at least one injection lance concentrically
around the supply channel comprises a gas channel for supplying a gas, wherein the
flow rate of the liquid hazardous waste is controlled by regulating a pressure of
the gas to said gas channel using a control valve based on the measured temperature,
flow rate and density.
12. Method according to claim 10 or 11, characterized in, that the liquid hazardous waste is supplied from a storage tank to the at least one injection
lance via a supply line with the aid of a pump comprised in the supply line, wherein
part of the liquid hazardous waste is returned from the at least one injection lance
to the storage tank via a return line, wherein a pressure in the supply line and/or
return line is measured, and wherein a control valve comprised in the return line
is controlled in such a way that a constant pressure is obtained at the at least one
injection lance.
13. Method according to claim 10, 11 or 12, characterized in, that the different hazardous wastes are tested for reactivity and compatibility before
incineration of different hazardous wastes.
14. Method according to any of claims 10-13, characterized in, that metals are recovered from bottom ash from the post-combustion chamber.
15. Metals recovered after incineration of hazardous waste using a device according to
any of claims 1-9 or a method according to any of claims 10-14.