Gasification in Aspen Plus
CHEN 4470 – Process Design Practice
Dr. Mario Richard Eden
Department of Chemical Engineering
Auburn University
Lecture No. 3 – Modeling Gasification Systems in Aspen Plus
January 17, 2013
Components
Feedstock used in this example is
Montana Sub-Bituminous Coal
Note: NOT an exhaustive list.
Stream Classes
Used for models where you have both conventional
(carbon) and nonconventional (coal/biomass + ash)
solids present, but no particle size distribution
Properties
The first parameter (6) indicates that you want to
enter the heat of combustion information yourself,
rather than have Aspen estimate it.
Properties
Properties
Enter a new pure component parameter here. Since
we are entering the heat of combustion for the
coal/biomass, it is classified as nonconventional
Properties
From feedstock information for Montana
Sub-Bituminous Coal
Feed Specification
Simple basis: 1000 kg/hr
Note that the coal is located in
the NC substream!
Feed Specification
Note: PROXANAL values for FC,
VM, and ASH sum to 100!
Moisture is added separately.
Feed Specification
Note: ULTANAL values sum to 100!
Values taken from feedstock description
Feed Specification
Note: SULFANAL values sum to ULTANAL value
for sulfur!
Sulfur breakdown from feedstock description:
45% pyritic, 45% organic, 10% sulfate
Pyritic: 0.45*1.22 = 0.549
Organic: 0.45*1.22 = 0.549
Sulfate: 0.10*1.22 = 0.122
Coal Decomposition
First reactor (RYIELD) serves to convert/decompose the coal/biomass into its
constituent parts, i.e. H2, O2, N2, H2O, S, C, and ASH.
This is NOT a true stand alone reactor, but an integral part of the gasification
reactor. The decomposition reactor serves to convert the nonconventional solids
into true components and ash.
Coal Decomposition
Coal Decomposition
Yield distribution is entered as mass yield of component per total mass of feed and calculated from
the ultimate analysis data:
mH2 = (1 – XMoisture)*XH*mFeed = (1 – 0.105)*0.0489*1000 kg = 44 kg
→ yield H2
= 0.044
mO2 = (1 – XMoisture)*XO*mFeed = (0.895)*0.1304*1000 kg =
117 kg
→ yield O2
= 0.117
mN2 = (1 – XMoisture)*XN*mFeed = (0.895)*0.0149*1000 kg =
13 kg
→ yield N2
= 0.013
→ yield H2O
= 0.105
mH2O = XMoisture*mFeed = 0.105*1000 kg =
105 kg
mS = (1 – XMoisture)*XS*mFeed = (0.895)*0.0122*1000 kg =
11 kg
→ yield S
= 0.011
mC = (1 – XMoisture)*XC*mFeed = (0.895)*0.6684*1000 kg =
598 kg
→ yield C
= 0.598
→ yield ASH
= 0.112
mASH = (1 – XMoisture)*XASH*mFeed = (0.895)*0.1251*1000 kg = 112 kg
Coal Decomposition
Note: It is necessary to specify that the ASH
component is 100% ash in PROXANAL.
Coal Decomposition
Note: It is necessary to specify that the ASH
component is 100% ash in ULTANAL.
Coal Decomposition
Note: It is necessary to specify that the ASH
component is 0% sulfur in SULFANAL.
Coal Gasification
Second reactor (RGIBBS) serves to convert the decomposed coal/biomass into
synthesis gas by reacting it with oxygen. The stream labeled GASFEED does not
exist in reality. It serves as a means of transferring the constituent elements of the
decomposed coal/biomass to the actual gasification reactor.
It is necessary to link the two reactor blocks by a heat stream in order to take the
energy required for the decomposition into account!
Coal Gasification
Simple basis: 1000 kg/hr
You will need to identify the
optimal oxygen feedrate along
with temperature and pressure
Coal Gasification
Coal Gasification
Important: The elementary
carbon formed (if any) needs to
be specified as a pure solid.
Solids Removal
The SSPlit subroutine allows for splitting the feed according to the individual
substreams, i.e. It enables separating the solids that are ”carried” in the NC and
CISOLID substreams to be separated from the gaseous products in the MIXED
substream
Solids Removal
A Few Results
Stream: SYNGAS
Substream: MIXED
Mole Flow kmol/hr
HYDROGEN
OXYGEN
NITROGEN
WATER
SULFUR
CO
CO2
H2S
METHANE
C
AMMONIA
Total Flow kmol/hr
Total Flow kg/hr
Total Flow cum/hr
Temperature C
Pressure bar
Vapor Frac
Liquid Frac
15.6820753
4.47E-15
0.46290993
11.2474944
8.55E-09
34.8003674
14.797821
0.34304247
0.18950623
0
0.00230474
77.5255214
1888
273.345722
1005.92981
30.3975
1
0
Stream: ASH
Substream: NC
Mass Flow kg/hr
COAL
ASH
Total Flow kg/hr
Temperature C
Pressure bar
Vapor Frac
Liquid Frac
Solid Frac
Enthalpy kcal/kg
Enthalpy Gcal/hr
Entropy
Density kg/cum
Average MW
0
112
112
1005.92981
30.3975
0
0
1
55.4111977
0.00620605
3486.88409
1