Clean Air Sustainable Recycling

Clean Air
Sustainable Recycling
Cleaning flue gases to preserve air quality:
a major challenge for Waste-to-Energy plants
and other industries
In this context, industries are facing a double
challenge:
■■
Comply with an increasingly binding legislative and regulatory framework. Industrial
flue gases must meet the requirements at the legal standards on acid gas emissions
(hydrochloric acid, sulphur dioxide, hydrogen fluoride and nitrogen oxides), heavy
metals and micro pollutants, dioxins and furans.
■■
Achieve performance
which
is not only economical
but
also socially and
environmentally
respectful.
“Best Available Techniques”: The European reference
The Industrial Emissions Directive IED
2010/75/EU requires that licenses to
operate industrial facilities in various
sectors take into account the reduction
and control of their environmental impact.
To allow this, a European Office based in
Seville defined the “Best Available Techniques” for each industrial sector.
These BATs are described in the Best
available techniques REFerence (BREF)
documents, which are becoming the
reference for providing information
regarding the emission levels that can be
achieved using specific techniques. The
dry sodium bicarbonate system is given as
one of the BATs.
SOLVAir ® Solutions backed by SOLVAY
The SOLVAir® Solutions were developed
and patented by SOLVAY, an international
group active in chemistry.
SOLVAir® mission is to offer and continuously develop competitive and sustainable
environmental solutions used for air emission control and associated waste, through
a range of products, services, technologies and treatment systems.
2 / SOLVAir
SOLVAY is the leading producer of sodium
bicarbonate worldwide and in Europe, with
seven BICAR® production sites in Europe.
BICAR® :
Production in Europe
Bernburg (DE)
BICAR® applications are numerous:
health, hygiene, detergents, disinfection,
food and feed, water treatment, paper,
powder extinguishers, pharmaceuticals
and many more.
Rheinberg (DE)
Dombasle (FR)
Torrelavega (SP)
Rosignano (IT)
Devnya (BG)
SOLVAir® : … the complete solution
Sodium Bicarbonate
Raw flue gases
Clean air
Clean flue gases
Residual Sodium Chemicals
Sustainable recycling
Recyclable product
Towards zero waste
Clean air
■■
Efficiency: the SOLVAir® bicarbonate dry process allows very high abatement rates,
which respect the strictest emission limits at an excess of BICAR® down to 10 %.
It eliminates sulfur oxides (SOx), chlorhydric acid (HCl) and fluorhydric acid (HF).
Combined with activated carbon, it adsorbs heavy metals, dioxins and furans.
■■
Economy and simplicity: BICAR® is a very effective reagent. Thanks to its
simplicity, the SOLVAir® bicarbonate process requires low investment and limited
maintenance costs. The quantity of Residual Sodium Chemical (RSCs) is reduced
and there is no need for liquid effluent treatment.
■■
Total safety of use: BICAR® is a neutral powder. It is non-corrosive, non-irritant and
non-toxic, and can be handled easily and safely.
Sustainable recycling
The SOLVAir® RSC Recycling Solutions
make it possible to treat and recycle the
Residual Sodium Chemicals coming
from the flue gas cleaning.
SOLVAir / 3
The SOLVAir® bicarbonate process:
dry injection of BICAR®
The sodium bicarbonate BICAR®, in
contact with the flue gases, effectively
neutralizes the acids.
Chemical reactions
(netto reactions with massic ratio)
NaHCO3
2.301
+
2
NaHCO3
2.625
+
2
NaHCO3
2.100
+
NaHCO3
4.200
+
Residue/sorbent ratio
➜
HCl
1
SO2
1
+
½
O2
➜
SO3
1
➜
HF
1
➜
NaCl
1.602
+
Na2SO4
2.218
+
Na2SO4
1.775
+
NaF
2.100
+
CO2
+
H2 O
0.696
2
CO2
+
H2 O
0.845
2
CO2
+
H2 O
0.845
CO2
+
H2 O
0.500
Thermal activation
2 NaHCO3
4 / SOLVAir
➜Na2CO3
+CO2
+H2O
Thermal activation of BICAR® through the microscope
Inside the flue gases, BICAR® is activated and becomes high specific surface sodium
carbonate.
This transformation is the key reaction wich gives the SOLVAir® bicarbonate process its
excellent acid neutralization performance.
Sodium bicarbonate before thermal
activation
Activated sodium carbonate
Temperature
The efficiency of BICAR® and the SOLVAir® bicarbonate process are optimal between
140°C and 300°C. Outside this temperature range, contact the SOLVAir team to define if
BICAR® can be used.
140° C
300° C
SOLVAir / 5
Clean air
Effective and simple, the SOLVAir® Bicarbonate Solution is a dry sorbent injection process
for air emission control.
SNCR
(optional)
Energy Recovery
Electricity
Steam
HCI
SOx
Waste
Clean gas
SOx, HCI, HF
Role of the bag filter
The acid neutralization reaction
begins as soon as BICAR® is in contact
with the acid gases.
With a bag filter, the sodium bicarbonate
forms a homogeneous layer on the whole
filtrating surface (filtration cake). This allows
neutralization of the acid gases efficiently
while complying with the strictest emission
limits and optimizing BICAR® consumption.
6 / SOLVAir
1
2
3
4
5
6
Comply with
2010/75/EU
Milled
Sodium
Bicarbonate Adsorbent
De-dusting
Reactor
(optional)
Bag
Filter
NH3
SCR
DeNOx
Heat
Recovery
(recommended)
Stack
Residual Sodium Chemicals
Fly ash
Towards Zero Waste
Step 1 1
Step 3 3
Step 5 5
To further enhance recycling of residues,
a first step of de-dusting is recommended
prior to neutralization.
The solid Residual Sodium Chemicals
(RSCs) resulting from the neutralization
are captured by the bag filter, ready
for sustainable recycling. Their main
components are sodium chloride, sodium
sulphate, sodium fluoride and sodium
carbonate.
A heat exchanger prior to the stack is
recommended to increase marketable
energy by improved recovery efficiency.
Step 2 2
The ground sodium bicarbonate BICAR® is
injected into the flue gas to neutralize the
acids present in the gas, particularly:
■■
hydrochloric acid (HCl)
■■
sulphur oxides (SOX)
■■
hydrogen fluoride (HF)
Together with activated carbon or lignite
coke, the process allows adsorption of
heavy metals and organic micro pollutants.
Step 4 4
Step 6 6
The clean gases are sent to the stack. The
SOLVAir® process can easily be adapted to
comply with future, more severe legislation
regarding emission limits.
A catalytic DeNOX device allows the reduction of NOX below the limit imposed by
the most severe legislation. Thanks to the
excellent SOX removal efficiency and adequate operating temperature, reheating of
the gases is not necessary.
Efficient and so simple
The SOLVAir® Bicarbonate process features a unique combination of pure simplicity
and excellent cleaning performance. Thanks to its thermal activation, the milled Sodium
Bicarbonate BICAR® succeeds in achieving the highest abatement rates of acids with a
very low excess. This result is achieved by a fully dry system, with nothing other than a
silo, an injection system and a filter as equipment. Too simple to be true ? Hundreds of
SOLVAir® users witness the efficiency of its performance everyday !
SOLVAir / 7
Clean air with a simple and safe process
A few operating settings will allow the optimization of
mitigation rate
Milled BICAR® particle size
The particle size distribution is a key element in the SOLVAir® Bicarbonate process. The
finer the grains, the larger the contact surface: efficiency is then improved.
Milling at d90 < 35 µm* is recommended for HCl mitigation (waste to energy plant) down
to 10 mg/Nm3.
A lower emission value of HCl or a SOX mitigation rate above 80 % requires d90 lower
than 20 µm to reduce the BICAR® consumption.
Mixing with flue gas
For best performance of the process, a homogeneous mixing is required and can
generally be achieved with a residence time of minimum 2 s before the filter. For ducts
bigger than 1 m2 section, BICAR® should be injected using a mixing system like a multiple
point injection.
Bag filter operation
The filter is one of the fundamental elements of the SOLVAir® Bicarbonate Solution. It acts
as a de-dusting device and also as a “reactor”. Thanks to the reagent layer formed on the
bags, the bag filter allows reduction of the BICAR® consumption.
Dust and water content
Even in cases where the raw gases contain a high level of dust or water, sodium
bicarbonate BICAR® allows very high mitigation rates.
* d90 < 35 µm : particles with the diameter less than 35 µm represent 90% of the volume.
Compatibility with DeNOx, particularly catalytic (SCR)
NOX reduction is accomplished by means
of either Selective Catalytic Reduction
(SCR) or Non Catalytic (SNCR) systems.
The SOLVAir bicarbonate Solution is
compatible with both.
The SCR system uses ammonia and a
catalyst to convert the NOX to N2. It needs
to operate at relatively high temperature
in order to avoid the condensation and
deposit of ammonium (bi)sulfates on the
catalyst layer.
When the catalyst system is installed at the
end of the treatment (tail end), as in many
waste to energy plants, using sodium
bicarbonate BICAR® enhances the energy
recovery. First of all, sodium bicarbonate
8 / SOLVAir
has the highest reactivity towards SO3
and SO2, allowing a very low level of
remaining pollutants, and minimizing the
risk of formation of ammonium (bi)sulfates.
Furthermore, the extended operating
temperature range for BICAR® avoids any
injection of water and the subsequent
cooling of the flue gases. Combined, these
facts enable the use of the catalytic device
at the same temperature as the bag filter,
saving the energy often used to re-heat the
gases.
A heat exchanger prior to the stack
increases marketable energy by improved
recovery efficiency.
Performance in acid mitigation
The HCl and SOX removal efficiency mainly depends on the design and optimization
of the air emission control system
Acid removal performance
When plant parameters comply with the SOLVAir® technical specifications, very high
acid removal rates are reached, above 99,9% for HCl and 99% for SO2. If the required
SO2 removal rate is below 80%, an extremely low excess of bicarbonate is necessary to
comply with the emission limit.
Generally observed HCl mitigation on a bag filter
100
95
90
HCl mitigation (%)
85
80
75
70
65
60
55
50
0,5
0,6
0,7
0,8
0,9
1,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
Stoichiometric ratio
Generally observed SO2 mitigation on a bag filter
100
95
90
SO2 mitigation (%)
85
80
75
70
65
60
55
50
0,5
0,6
0,7
0,8
0,9
1,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
Stoichiometric ratio
BICAR® is extremely efficient on SO3
BICAR® preferably neutralizes SO3 compared to SO2. This effect allows:
■■
to protect DeNOX catalysts from ammonium (bi)sulfate deposits
■■
to increase the regeneration time interval of catalysts
SOLVAir / 9
Typical process control
As the acid concentrations are measured at the stack, the BICAR® flow rate can be effectively controlled in order to respect the strictest emission limits with a minimum sorbent
consumption.
40
100
30
75
20
50
10
25
0
Sodium bicarbonate flow rate (kg/h)
HCI in clean gas (mg/Nm3 dry at 11% O2)
Respect of an emission limit of 10 mg/Nm³ HCl dry at 11% O2
(daily average)
0
0:00
2:00
4:00
6:00
8:00
10:00
12:00
HCI in clean gas (mg/Nm3 dry at 11% O2)
Bicarbonate flow rate (kg/h)
Peak shaving
The SOLVAir® process is extremely flexible. It has proven its efficiency for acid concentrations even above 10 000 mg/Nm3. Acid raw gas peaks are very rapidly absorbed thanks
to the fast reaction speed of BICAR®.
3200
80
2800
70
2400
60
2000
50
1600
40
1200
30
800
20
400
10
0
0
24.05.2011
09:36:00
24.05.2011
10:48:00
24.05.2011
12:00:00
HCI in raw gas (mg/Nm3 wet)
10 / SOLVAir
24.05.2011
13:12:00
24.05.2011
14:24:00
24.05.2011
15:36:00
Bicarbonate flow rate (kg/h)
24.05.2011
16:48:00
24.05.2011
18:00:00
24.05.2011
19:12:00
HCI in clean gas (mg/Nm3 dry at 11% O2)
HCI in clean gas (mg/Nm3 dry 11% O2)
HCI in raw gas (mg/Nm3 wet)
Sodium bicarbonate flow rate (kg/h)
Example of removal of HCl peaks at waste-to-energy plant
(10 mg/Nm³ HCl dry at 11% O2- daily average)
Energy efficiency
Recovery from Waste can also benefit
from green energy certificates, since a
major part of Municipal Solid Waste (MSW)
is renewable biomass, thus boosting
profitability.
Energy efficiency is becoming more
and more critical for the waste to energy
industry because it contributes to the
reduction of CO2 emissions. As cheap
fuels are becoming rare, the competition
between energy producers increases daily.
Bag
Filter
For instance, in the EC directive on waste
2008/98/EC, an energy efficiency factor
‘R1’ is defined. If an installation is rated with
a factor lower than 0.60 (or 0.65 depending
on the permit date), the operation will not
be accepted as ‘Energy Recovery’ but
as ‘Disposal’. In some countries Energy
NH3
Heat
Recovery
SCR
DeNOx
185° C
(recommended)
185° C
135° C
Heat + 131 kWh/t
The reactivity of sodium bicarbonate BICAR is high within a large moisture content and
temperature range. This is why SOLVAir® bicarbonate process avoids water injection
for cooling/conditioning purposes and reheating of the flue gas upstream of a catalytic
DeNOx system (SCR). By saving steam or fuel for flue gas reheating, and by optimizing
heat recovery, the marketable energy expressed in the graph below as net conversion
yield is boosted for SOLVAir® process :
®
■■
From 29% for a wet flue gas treatment with only electricity production to 88% for
a waste-to-energy plant using SOLVAir® process and connected to district heating
network
■■
From 40%, which is the average of 314 plants (CEWEP 2013 study), to 51% with
SOLVAir® process by reducing the internal heat consumption and increasing the
energy recovery (131 kWh/t MSW)
Total net conversion yield on input (0 - 100%)
88%
R1 - Waste Frame Directive Definition (0 - 2,37)
R1 - Corrected with Climatic Factor (0 - 3,27)
29%
0,84
0,99
Wet F.G.T. MSWI Example
Germany (2007)
1,69
1,31
51%
40%
0,79
0,79
Average CEWEP 314 EU Plants
Actual situation (2013)
If all of them would use SOLVAir®
bicarbonate process
SOLVAir® MSWI Example
Italy (2011)
The graph above shows that the R1 factor is not linked to the net conversion yield, due to
the fact that each flue gas treatment technology has a different internal energy use. The
R1 climate correction factor which is already implemented in some southern countries
increases the value of the R1 factor, in this example from 1,31 to 1,69.
Sources:
P. Billig, Beitrag der Abfallwirtschaft zum Klimaschutz, 2007, Duisburg (DE)
CEWEP Energy Report III by Dr.-Ing. Dieter O. Reimann, 2013, Bamberg (DE) and Energy Recovery / Energy increasing potential
using Sodium Bicarbonate for Dry Flue Gas Cleaning in Thermal Waste Treatment by Dr.-Ing. Dieter O. Reimann
R. Boero, Tecnologie e gestione nell’incenerimento dei rifiuti. Operatori e comunità scientifiche a confronto, 2011, Cassino, (IT)
Clerens / ESWET report for JRC and HDD data according to Eurostat
Gazzetta ufficiale della Republica Italiana del 31.07.2013
SOLVAir / 11
Sustainable recycling
Waste-to-Energy industry
The Directive 2008/98/EC indeed gives
a much higher priority to recycling over
disposal.
With the SOLVAir® Bicarbonate Solution,
the recycling of residue is an industrial
reality. It provides practical answers to
environmental issues, minimizing the
disposal of final waste in accordance with
the European waste policy.
Since the beginning, SOLVAir® Research
teams have developed and patented solutions to recycle residual sodium chemicals. These studies have allowed SOLVAY
De-dusting
1 t RSU
Sodium
Bicarbonate
± 15 kg *
Adsorbent
± 0,4 kg
Fly ash ± 20 kg
SOLVAY proposes an original and patented
technology to treat the Residual Sodium
Chemicals (or RSC) of waste-to-energy
plants. The sodium salts based on sodium
chloride are treated and recycled as a
substitute for one of the raw materials used
to produce sodium carbonate.
Bag
Filter
Brine
Purification
Filtration
Dissolver
* Depending on waste quality
Recyclable brine ± 45 kg
(± 10,5 kg salts)
Cake 1 to 2 kg
Stabilisation
Final residue 2 to 4 kg
Disposal on licenced landfill site
The SOLVAL® unit in Rosignano, Italy, a 100 % SOLVAY
subsidiary, processes the Residual Sodium Chemicals of several
Italian waste-to-energy plants, and sends the purified brine to the
soda ash plant.
12 / SOLVAir
In France and Italy, SOLVAY has invested in
the recycling of flue gas cleaning residues
from waste to energy plants.
Residual Sodium Chemicals ± 11,5 kg
Water
Towards
Zero Waste
to implement, alone or in partnership,
industrial scale treatment plants.
Soda Ash production
The RESOLEST® plant, located in the East of France near Nancy,
is a joint venture between SOLVAY and SITA FD (SUEZ). The brine
is transported by pipeline to the SOLVAY Dombasle plant located
4 km away, and is used in the production of sodium carbonate.
Desulphurization facilities
For facilities having SOX as main pollutant, such as power plants, ceramics production,
sewage sludge incineration, ferrous and non ferrous production etc., the major component
of residue is sodium sulphate.
To enable the recycling of these residues, SOLVAir® has developed the RESOGYPSE®
process, based on the following reaction:
Na2SO4
+
CaCl2
➜
CaSO4
+
2 NaCl
This process presents the advantage of transforming residuals into two valuable products,
calcium sulphate, known as gypsum, widely used in cement production, and sodium
chloride, used as a raw material in soda ash production.
Calcium
chloride
solution
Brine
5.5 tons
Soda ash plant
Residue
1 ton
Gypsum
0.75 ton
Building
materials
Gypsum
Sodium
carbonate
production
Resogypse® is in operation
RESOLEST® plant near Nancy
at
the
Glass and aluminium industries
The glass industry and secondary aluminium production are among the sectors
for which SOLVAir® offers an economical
and combined solution: in addition to the
neutralization of the acids in the flue gases,
RSC can be recycled as raw materials in
their production.
SOLVAir / 13
Importance of bicarbonate particle size
Savings on sorbent
Sorbent avergae consumption per line (Kg/h)
The flue gas treatment performance may be significantly lower when sodium bicarbonate
particle size distribution is coarser than SOLVAir® technical specifications values (d90 < 35
µm for HCl mitigation down to 10 mg/Nm³ and d90 < 20 µm for SOX mitigation rates above
80% or HCl < 10 mg/Nm³ at stack). According to SOLVAir® MSWI customer experience,
the sorbent consumption may decrease up to 18% if milled sodium bicarbonate particle
size distribution decreases from d90 ~46 µm to d90 ~28 µm.*
160
140
120
100
80
60
40
45,6
20
28,0
0
Particle size distribution : d90 (µm)
Savings on residues
A sorbent overconsumption of 18% also increases RSC production of almost 12%**. This
has to be added to the extra sorbent costs.
Optimizing the sorbent consumption has therefore a double positive effect for the customer operating costs and also for the flue gas treatment environmental footprint.
How to get the right particle size?
Milling on site
A hammer milling technology and dynamic air classifier system enables to get the adequate particle screening and delivers a constant particle size distribution at all sorbent
flow rates.
Ready-to-use product
SOLVAY supplies ready-to-use sorbent, specially designed for flue gas treatment purposes. The ready-to-use sorbent solution has the advantage to:
■■
lower the costs
■■
be easily implemented
■■
increase flexibility on the dosing rate
■■
be formulated for easy handling
For any further information, please contact SOLVAir ® team.
*Q
uery: SOLVAir ® optimization campaign at a French Waste-to-Energy facility (2 x 8 t/h
lines) with weekly follow-up of RSC composition from November 2007 till May 2008.
** Assuming that overdosed sorbent with coarse particle size distribution will generate
soda ash and not mitigate acid compounds.
14 / SOLVAir
Expertise serving industry
SOLVAir® has built its know-how and renowned reputation on its capacity to partner
industries in their technical, economical and environmental evolution.
The SOLVAir® team is at your side throughout every stage of your project.
Alongside engineering companies or your own technical teams, they offer you expertise
and advice to:
■■
establish a diagnosis of your installations’
emissions
■■
assist in the design of the flue gas
cleaning plant
■■
explore the possibilities of converting
existing flue gas cleaning systems to the
SOLVAir® Bicarbonate process
■■
propose and carry out preliminary
tests in situ with mobile equipment and
laboratories
■■
ease and optimize the start-up and
commissioning stages : air emission
control performance analysis, verification
and optimization
■■
consider purification and/or recycling
possibilities for the Residuals Sodium Chemicals.
The SOLVAir® markets
Ceramic Industry
Industrial Boilers
SOLVAir ® has acquired
and continues to
develop expertise in
many markets to provide
the best solution for
each of its numerous
customers.
Steel Industry
Cement Plant
Paper Mills
Non Ferrous
Metallurgy
Waste to Energy
Wastewater (sludge)
Glass Industry
Oil Refinery
Energy from Biomass
Carbon based
Industry
Mineral Wool
Industry
SOLVAir / 15
SOLVAY SA - NV
Rue de Ransbeek 310
B – 1120 Brussels
© 2014, Solvay
www.solvairsolutions.com
www.solvaybicar.com
www.solvaychemicals.com
The information contained in this document is given in good faith and by way of information at the time of publishing. SOLVAY does not
engage its responsibility.The use of our products is the treatment of flue gases, excluding all others uses and applications. The buyer
is required to monitor and respect, in his sole liability, the conditions under which our products are stored and used in his territory, to
provide all required information to the user, and to respect all existing patents and all regulations applicable to our products and to his
activity.

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