Note: Descriptions are shown in the official language in which they were submitted.
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Method And Plant For Recovering Material And/Or Energy From Phosphorus-
Containing
Waste
The invention relates to a method and to a plant for recovering material and
energy from
phosphorus-containing waste by way of air and/or oxygen melt gasification in
metallurgical shaft
furnaces.
The recycling industry is increasingly pursuing the objective of reducing the
consumption
of finite natural resources, including phosphorus, or of using such resources
more efficiently
["Kreislaufwirtschaft Pflanzennahrstoffe, insbesondere Phosphor" (Closed loop
recycling
management of plant nutrients, in particular phosphorus) funding initiative,
final presentation,
Berlin on 09/14/2011 , Dohmann, Conference Paper 1]. Phosphorus is essential
for all biological
processes and plays a key role in the transfer and storage of energy and in
the synthesis of amino
acids and proteins, cannot be substituted, and is the limiting factor for many
growth processes. It
is not consumed, but is diluted, making enrichment increasingly economically
complex. The
most important source for phosphorus recovery is animal and human excretions
(sewage sludge).
When fully recycled, sewage sludge (66,000 Mg P/a) as well as animal and bone
meal (23,700
Mg P/a) allow approximately 75% of Germany's mineral fertilizer imports (on
average, 120,000
Mg P/a) to be saved ["Kreislaufwirtschaft Pflanzennahrstoffe, insbesondere
Phosphor" (Closed
loop recycling management of plant nutrients, in particular phosphorus)
funding initiative, final
presentation, Berlin on 09/14/2011 , Pinnekamp, Conference Paper Introductory
Remarks].
According to the prior art, the following process-based / plant-based
solutions for
recycling sewage sludge, animal meal and their ashes from the respective mono-
incineration
processes are considered to be particularly promising ["Kreislaufwirtschaft
Pflanzennahrstoffe,
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insbesondere Phosphor" (Closed loop recycling management of plant nutrients,
in particular
phosphorus) funding initiative, final presentation, Berlin on 09/14/2011 ,
Rosckosch, Conference
Paper German Federal Environmental Agency].
- ASH DEC - thermochemical process
Product: phosphate fertilizer (raw product, optionally multi-nutrient
fertilizer) made of
sewage sludge ashes by heating in a rotary kiln while adding additives
- Mephrec - metallurgical process
Product: lime phosphate fertilizer from sewage sludge, sewage sludge ashes and
other
phosphorus-containing waste by way of air and/or oxygen melt gasification in a
fixed bed
reactor
- PhosRec - special sintering process
Product: phosphate fertilizer or phosphate resource from animal meal by
incineration in a rotary
kiln, while simultaneously utilizing the recovered energy.
Previously, only the Mephrec process achieved the simultaneous material and
energy recovery
from organic, phosphorus-containing waste having varying degrees of calorific
values and/or
feed materials in one method step, by generating a phosphorus-containing slag
, which is
comparable to the well-known fertilizer "Thomas meal" and has high solubility
in citric acid of
the lime silicophosphates formed in the slag matrix, an iron metal alloy,
which acts in a method-
specific manner as a heavy metal drain, and a fuel gas, which has varying
degrees of calorific
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values and is suitable after purification for direct energy generation via gas
motors or units
comparable to these.
Such a metallurgical method for recovering energy and material from inorganic
and/or
organic waste having a high calorific value and for minimizing the necessary
method-related,
plant-related, production organizational and therefore financial expenditures
for processing the
feed materials into formed bodies or briquettes is claimed according to DE 10
2008 045 289, in
which the waste that has a high calorific value and/or is rich in recyclable
fractions and brings
about material binding is mixed, either as a binding agent alone or in
combination with a
hydraulic binding agent content and/or an opening material, with further
inorganic and/or
organic waste that has a high calorific value and/or is rich recyclable
fractions, thereafter formed
and/or pressed or extruded to obtain formed bodies or briquettes and/or is
compacted or formed
into briquettes by other method steps, stored, and subsequently used for the
simultaneous
recovery of energy and material in a single method step, utilizing known
metallurgical procedure
techniques in cupola melting furnaces, oxygen cupola melting furnaces, shaft
melt gasifiers,
high-temperature oxygen melt gasifiers or similar metallurgical units as bulk
material. As the
bulk material, which, in total, is composed of coke and/or coke substitutes,
mineral and/or
metallic aggregates added, or not added, based on melting and gasification
aspects, and the
molded bodies and/or briquettes, moves downward, it is dried in the furnace
shaft, heated,
gasified and subsequently melted, wherein, depending on the composition of the
molded bodies
or briquettes forming the bulk material, at the same time a furnace gas that
has a high calorific
value, which is to say that has not been spent, a liquid slag that is high in
recyclable fractions,
and a liquid metal alloy are created in the reduction zone that exists in the
metallurgical unit.
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The waste that has a high calorific value and/or is rich in recyclable
fractions and brings
about the material binding can also be bone meal and/or animal meal. Cement
and/or cement
substitutes are claimed as hydraulically acting binding agents. The opening
materials, which are
added in particular to waste that has a high calorific value and/or is rich in
recyclable fractions
and high in moisture, are in particular ashes and/or slags and/or mineral
and/or metallic and/or
oxidic granular or pulverulent substances that are high in recyclable
fractions and/or rich in
phosphorus. Further inorganic and/or organic waste that has a high calorific
value and/or is rich
in recyclable fractions can be mixtures of sewage sludge and/or further
organic and/or inorganic
phosphorus-containing substances and/or substances that increase the calorific
value.
The method is characterized in that a furnace gas that has a high calorific
value, which is
to say that has not been spent, a liquid slag that is rich in recyclable
fractions, which is to say rich
in phosphorus, and a liquid metal alloy acting as a heavy metal drain are
created simultaneously
in the metallurgical unit.
The disadvantage is that, in a way that is specific to the method, a furnace
gas that has a
high calorific value and has not been spent is generated, which prior to the
energetic use for
power generation necessitates a complex, wet gas purification process that is
combined with an
integrated quenching step for the purpose of cooling to approximately 5 C, due
to organic
residues that are present.
It is further disadvantageous that, in a way that is specific to the method,
phosphorus
and/or phosphorus compounds reaching the gas phase require technically and
technologically
complex separation in the gas purification process, and therefore cannot be
used for the
metallurgical material recycling.
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DE 000002952642 Al describes a method for the dry hot purification of gases
containing
harmful substances, such as process gases and waste gases from thermal
treatment plants, which
are created during the pyrolysis of waste substances by heating them to the
decomposition
temperature, for example, in which the harmful substance-containing raw gas is
caused to react
at an elevated temperature with the additives that are added to the raw gas,
and the harmful
substances are thus removed from the raw gas.
The disadvantage is that the dust separated during gas purification contains
reaction
products of harmful substance and additives, which result in undesirable
accumulations during
the recirculation into the thermal treatment plants.
It is therefore the object of the invention to create a method and a plant for
recovering
material and energy from phosphorus-containing waste, in which, without the
use of a complex,
wet gas purification process that is combined with an integrated quenching
step for the purpose
of cooling to approximately 5 C, for example due to organic residues that are
present, the
phosphorus and/or phosphorus compounds reaching the gas phase, in a way
specific to the
method, during the material and energy recovery of phosphorus-containing waste
by way of air
and/or oxygen melt gasification in metallurgical shaft furnaces can be easily
separated and
rendered usable for metallurgical material recycling.
The object is achieved by integrating a post-incineration chamber, which is
integrated in
or directly on the metallurgical shaft furnace, as an integral part of a
graduated gas purification
process, comprising a dry dedusting step without adding additives for binding
and removing
gaseous harmful substances by a dedusting device having integrated dust
recirculation into the
melting and superheating zone of the metallurgical shaft furnace, without
adding additives for
binding and removing gaseous harmful substances according to the features of
the claims.
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Advantageously, the apparatus-related, economical and process-related
advantages
recognized according to the prior art of metallurgical shaft furnaces with
direct post-incineration
of furnace gases are combined with the air and/or oxygen melt gasification of
organic matter-
and phosphorus-containing waste, such as sewage sludge, by directly post-
incinerating the fuel
gas, which has a high calorific value and is directly generated in the furnace
for air and/or
oxygen melt gasification, with an excess of incineration material ( X.> 1) to
obtain a dust-laden,
completely spent offgas, without binding gaseous harmful substances by way of
additives.
In in-house examinations, it was surprisingly found that the phosphorus and/or
the
phosphorus compounds reaching the gas phase largely as aerosols, due to the
nature of the
method, can basically be fully converted into an oxide, hereafter referred to
as phosphate,
separated after cooling to below the melting temperature of P205, which is to
say below 340 C,
as a dust component from the first stage of simple, dry dedusting according to
the prior art, and
recirculated into the melting and superheating zone of the furnace for air
and/or oxygen melt
gasification. In a second stage then, gaseous harmful substances, such as S
and Cl compounds,
are easily separated from the gas, likewise according to the prior art, for
example by adding
additives and/or by integrating scrubbers.
During the recirculation of the dust from the first stage of dry dedusting, an
accumulation
of highly volatile heavy metals may occur in the dust that is removed with the
fully post-
incinerated gas, depending on the content of these heavy metals. Depending on
the level of
accumulation, this is counteracted by outwardly transferring portions of the
separated dust.
The invention will be described in more detail hereafter based on two
exemplary
embodiments for separating phosphorus-containing dust from the first stage of
the graduated gas
purification process. The experiments were carried out using a metallurgical
shaft furnace for air
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and oxygen melt gasification, having an inner shaft diameter of 400 mm, a
usable shaft height of
2 m, and post-incineration provided directly over the charging opening. The
average batch
weight was 19.5 kg. The feed amounts and the briquette components for each
experiment are
illustrated in Table I.
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Table 1 Feed material and charging
Mixture II IV
Components in the briquette
Sewage slude % 60 49
Ashes from sewage slude mono- % 40
incineration % 15
Cement % 47
Animal meal % 4
Sawdust
Feed amount per experiment
Briquette kg 335 315
Iron kg 9.3 15.3
Batch coke kg 89.5
31.5
Limestone kg 6.3
Table 2 shows the average furnace parameters that were set.
Table 2 Furnace parameters
Mixture II
IV
Melting [Batch 1 to end of batch] kg/h 248
315
capacity
Oxygen Quantity 0 Nm3/h 25
22
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Air Quantity 0 Nm3/h 251
143
Air Temperature 0 C 236
217
Upper fire [estimated visually] normal
strong
Corresponding to the composition having a high calorific value composed of 47%
animal meal,
49% sewage sludge, and 4% sawdust as opening material, a strong upper fire
developed in
Experiment IV compared to Experiment IL
Slag granules having the following oxide analysis (Table 3) were generated.
Table 3 Oxides
Si02 A1203 CaO MgO FeO + Fe203 Femee
P205
% % % % % % %
II 27.6 19.9 32.5 3.8 3.3 0.2
10.6
IV 28.7 20.5 33.8 3.3 1.3 1.3
3.8
Table 4 Chemical dust analysis
Mixture II
IV
P205 total % mass 17.3
19.8
S03 total % mass 0.16
0.08
ZnO total % mass 1.25
1.79
TiO2 % maa 0.56
0.19
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Fe2O3 % mass 11.5 35.9
A1203 % mass 14.9 3.47
S102 % mass 25.9 19.3
Na20 % mass 0.83 1.92
K20 % mass 1.77 3.76
CaO % mass 24.5 10.0
MgO % mass 2.85 1.38
MnO % mass 0.15 0.46
The dust separated from the completely post-incinerated furnace gas contained
a significant
amount of P205, in addition the customary ash components according to Table 4.
The phosphate content according to Table 5 forms a Ce-Fe phosphate
(Ca9Fe(PO4)7),
which represents a stoichiometric mixture of Fe203, CaCO3 and Ca2P207 (Solid
State Sciences
6(2004) 186].
Table 5 Mineralogical dust analysis
Mixture II IV
Quartz Si02 S102
Ca-Fe phosphate Ca9Fe(PO4)7
Ca9Fe(PO4)7
Hematite Fe203
Maghemite Fe203
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Calcium aluminate (C3A) Ca3A1206 Ca3A1206
Magnesite MgCO3
Calcite CaCO3
Meionite (Ca, Na)2(Si, A1)6012(CO3)o 5
K-Fe oxide KFe02
Picromerite
K2Mg(SO4)2*6H20
Jarosite
(K, H30)Fe3(SO4)2(0F1)6
