ChE 302 - Chemical Process Analysis Sessional
Assignment/project: H2O2 Plant simulation using HYSYS
Process Definition
A hydrogen peroxide plant is to be set-up at Gazaria, Munshiganj having a capacity of 100 metric ton of
hydrogen per oxide (50 % w/w) per stream day, corresponding to 33,000 metric ton of hydrogen peroxide(50%
w/w) per year, including all off sites, auxiliaries, utilities and supporting facilities using natural gas as
feedstock and fuel. Other raw materials include Water and Air.
Process Description
The process of producing Hydrogen Peroxide is divided into two parts. In the first part it is the Hydrogen Generation Plant
where hydrogen is produced through steam reforming reaction. In the second part the hydrogen reacts with the working
solution (heavy aromatic, HA + tri-octylphosphate, TOP + 2-ethyl-anthraquinone, 2-EAQ) in presence of Palladium (Pd)
catalyst to form hydroquinone, this hydroquinone is oxidized to form H2O2. This process is delineated on the attached
PFD.
1.1 Hydrogen Generation Plant
1.1.1 NG Reforming
After being preheated and desulfurized, NG will be mixed with steam at a certain ratio. And then the mixture of NG and
steam will pass through the heating coils in the convection section of the reformer to go up its temperature to 600-700oC
before being fed into the reformer. After that, it passes through the reformer tubes containing Ni catalyst where the
catalytic cracking reaction and CO shift reaction will take place at the same time; in the result H 2, CO2, CO will be
formed. To recover the heat the waste heat boiler is provided to generate the byproduct steam, the most part of which will
be used in it.
1.1.2 Hydrogen Purification
The reformed gas from the reformer contains not only H2 but also other components, namely, CO, CO2 and CH4. In order
to get rid of all the impurities and obtain pure H2, which is used as raw material for producing H2O2, a separation
technique is applied. Pressure swing adsorption (PSA) is used for purification of raw H2. Hydrogen coming from PSA
system will have the purity of not less than 98.5 % H2 and this stream is then fed into the hydrogenation column as a main
raw material for production of H2O.
1.2 Hydrogen Peroxide Plant
The auto-oxidation process for hydrogen peroxide production is depicted in this section. First, working solution is
prepared by adding heavy aromatic and tri-octylphosphate to form an organic binary mixture (called the solvent) and then
dissolved 2-ethylanthraquinone as working compound in the solvent. The working solution is catalytically hydrogenated
to 2-ethylhydroanthraquinone in presence of Pd catalyst. Then the hydrogenated solution enters into the oxidation column
where it converts to anthraquinone and hydrogen peroxide by oxidation with air. The hydrogen peroxide remains
dissolved in the solvent until it is extracted out by de-ionized water in the extraction column. The working solution is
recycled to the hydrogenation column while the hydrogen peroxide solution is send to the purification section where
impurities are removed and the product hydrogen peroxide with a concentration of 50% is obtained.
1.2.1 Preparation of the working solution
The heavy aromatics and tri-octylphosphate (TOP) are added in a certain proportion into the working solution preparation
tank, then 2-ethyl-anthraquinone is added with agitating and heating to make it dissolved completely then the solution is
cooled to ambient temperature, and then send to the production system.
1.2.2 Hydrogenation Section
Hydrogenated reaction is one of the two main reactions in hydrogen peroxide production through anthraquinone method.
EAQ in working solution is hydrogenated under existence of palladium catalyst to produce hydrogenated anthraquinone
(or 4-hydrogen hydrogenated anthraquinone).
Hydrogenate temperature
A certain initial temperature is required in hydrogenate process, so hydrogen and working solution need to pre-heat and
the temperature is about 40°C. Hydrogenate reaction is an exothermic reaction. Hydrogenate temperature shouldn't be too
high, it is controlled between 50°C and 75°C generally to avoid the occurrence of vice-reaction. In order to control
hydrogenate temperature, working solution and hydrogen pre-heating temperature can be regulated.
Hydrogenate pressure
If the hydrogen partial pressure is higher than better the hydrogenated reaction. If hydrogen content keep unchanged,
the higher of total pressure, the higher of hydrogen partial pressure, the better for hydrogenated reaction, but too
high isn't necessary. In general, fixed bed column top pressure is about 0.3-0.4MPa. Raising pressure can compensate the
fall of catalyst activation. Fixed bed column bottom pressure is controlled at 0.25-0.3MPa to make sure that hydrogenated
solution is pumped to oxygenated column.
The working solution from the preparation section is sent by pump to the hydrogenation column. H2 coming from the
hydrogen generation unit is also fed to the hydrogenation column continuously at constant flow and pressure and in the
presence of hydrogenation catalyst (Pd catalyst) the hydrogenation reaction takes place and the working solution is
hydrogenated. The hydrogenated working solution is sent to the oxidation section.
1.2.3 Oxidation Section
Hydrogenated anthraquinone reacts with oxygen automatically, so this method is also called anthraquinone
automatic oxygenation. Reaction is as follows:
OH
O
C2H5
+ O2
OH
C2H5
55-60 OC
+ H2O2
O
A. Pressure
Pressure doesn't have much effect on oxygenate reaction, due to there is a certain resistance for discharge of tail gas,
bottom's is 0.3-0.4MPa, top's is 0.25-0.3 MPa.
B. Temperature
Oxygenate reaction is kind of exothermic heat, if reaction temperature is too low, reaction velocity is too low; but if
reaction temperature is too high, side-reaction will be accelerated. Generally it is controlled at 50-55°C. At oxygenate
column inlet, hydrogenated solution temperature can be adjusted by hydrogenate solution cooling regulator.
Oxidation tower consist of two sections, namely the upper section and lower section. The hydrogenated solution is entered
the oxidation column at the middle of upper section, and the compressed air is divided into two streams; it enters the
oxidation column separately at the bottoms of upper and under sections. Oxidation reaction occurs in the oxidation
column at a constant temperature and pressure to form hydrogen peroxide. The vapor coming from the top of the upper
section is chilled by using a chiller. Then it is fed to the flash separator where the gas is separated from the oxidized
working solution. And the tail gas is vented to the air. The oxidized solution from the upper section flows into the under
section at the bottom, in which it is oxidized further. This solution is sent to a separator where vapor and liquid is
separated. And the vapor is combined with the vapor from the upper section. After cooling, the separated oxidized
working solution enters into the extraction section.
1.2.3 Extraction and Purification section
The oxidized solution is fed to the extraction column at the bottom while the de-ionized water is fed to the column at the
top. They mix and contact each other within this column. The de-ionized water extracts the hydrogen peroxide from the
oxidized solution as a result. The hydrogen peroxide solution (about 50% wt. H2O2 concentration) from the bottom of the
column enters the purification column. The raffinate flowing out from the top of the extraction tower is sent to the post
treatment section. The extraction column is made in stainless steel and sieve plate type.
For removing the organic impurities from the extract phase, the hydrogen peroxide solution is counter currently contacted
with the heavy aromatics (HA) in the purification column and flows out from the bottom of the tower, then it is send to
the storage tank. The organic impurities containing heavy aromatics discharged from the top of the tower is reused after
treatment.
1.2.4 Post-Treatment Section
The raffinate flowing out from the extraction tower is entered (the lower part of the drying tower where it contacted
counter currently with the concentrated potassium carbonate solution to remove moister from it. Then the working
solution flows out from the upper part of the drying tower)/ (the flash separator) and entered the bottom of the argil bed.
In the argil bed, the degraded impurities are removed from it with activated alumina. The working solution flows out from
the upper part of the argil bed is returned to the hydrogenation section by the regeneration working solution pump for
reuse.
Reactions
Rxn-1
CH4+H2O = CO+3H2
Rxn-2
CO + H2O = CO2+H2
Rxn-3
H2+ EAQ = EAQinol
Rxn-4
EAQinol+ O2 = H2O2+ EAQ
Rxn-5
K2CO3 Absorbs H2O
Rxn-6
CH4+ 2O2 = CO2+ 2H2O
Rxn-7
C2H6+ 3.5O2 = 2CO2+ 3H2O
Rxn-8
C3H8+ 5O2 = 3CO2+ 4H2O
Rxn-9
C4H10+ 6.5O2 = 4CO2+ 5H2O
Rxn-10
C5H12+ 8O2 = 5CO2+ 6H2O
Rxn-11
C2H6+ 9O2 = 6CO2+ 7H2O
Reformer: Rxn-1 & Rxn-2
Furnace: Rxn-6 to Rxn-11
Hydrogenation Tower: Rxn-3, 90% conversion.
Oxidation Tower: Rxn-4, 100% conversion.
Product Specification
H2O2 specification:
 H2O2 content
50%
 Free acid (as H2SO4)
0.040% max.
 Non-volatile matter
0.080% max.
 Stability
97.0% min.
 Freezing point
-52.2°C
 Boiling point
113.8°C
 Density
1191 kg/m3
Raw Material Specification
Natural Gas Composition: (mass fraction)
CH4
96%
C2H6
2.15%
C3H8
0.53%
C4H10
0.09%
C5H12
0.15%
C6H14
0.11%
N2
0.97%
WS Composition: (mass fraction)
TOP
AH
EAQ
21.90% 62.59% 15.51%
Process Variables
Temperature
Pressure
NG
25oC
240 kPa
Steam
218oC
2200 kPa
Air
25oC
100 kPa
Supplementary Data
Steam to NG molar flow ratio: 3.5
WS to Hydrogen containing stream ratio: 21
Temperature
Pressure
Compressed NG
PSA outlet
Compressed air to
oxidation tower
40oC
1980 kPa
40oC
650 kPa
25-30oC
300 kPa
Project
A HYSYS simulation of the above process, containing material and energy balance, is required. Necessary Data
will be provided on request. Check out your course teachers’ website for recent updates.
tanvir@che.buet.ac.bd