Title: Chemical Reactors Energy Integration Applied to Supercritical Water Oxidation
1Chemical Reactors Energy Integration Applied to
Supercritical Water Oxidation
- E.D. Lavric1,3, H. Weyten2, J. De Ruyck3, V.
Plesu1, V. Lavric1
1University Politehnica of Bucharest-CTTIP 2Vlaams
e Instelling vor Technologisch Onderzoek 3Vrije
Universiteit Brussel
2Supercritical water oxidation (SCWO) main
features
- The SCWO technology is an efficient, economical,
and environmentally safe method to destroy a
significant share of the aqueous wastes - SCWO is a homogeneous-phase process that occurs
in water at temperatures and pressures above the
mixture thermodynamic critical point (for water
22.1 MPa and 647 K).
3Problems to be solved before starting the analysis
- Units topology of the process
- Type of the chemical reactor
- Kinetics of the SCWO oxidation
- Package of properties to be used
4Main parameters of the process
- Pressure (between 24-50 MPa)
- Temperature of the reactor feed (gt 650 K)
- Pollutant concentration
- Maximum allowable temperature 925 K
- Destruction efficiencies of over 99.99
5Type of the chemical reactor
- Perfectly mixed
- Plug flow
- Adiabatic
- Non-adiabatic
6SCWO Flowsheet
7Parameters
- Organic concentration 1.67 (n-C6H14) Tout r
893 K - Pressure 23 MPa
- Destruction efficiency over 99.99 (?length
reactor) - Mixer input temperatures
- 673 K (adiabatic reactor)
- 683 K (non-adiabatic)
- 693 K (non-adiabatic)
- 703 K (non-adiabatic)
- 713 K (non-adiabatic)
- 723 K (non-adiabatic).
- Package of properties Peng Robinson with
modified Huron-Vidal mixing rules
8Kinetics of oxidation
9Pinch Analysis - basics
- Identifies
- sources (hot streams)
- sinks (cold streams)
- Builds
- composite hot and cold stream curves
- grand composite curves
- problem table
- Designs
- HEN topology avoiding heat transfer across the
pinch - Economically optimum configuration - transfers
some heat across the pinch, breaking loops
accordingly
10Chemical Reactors Energy Integration (CREI)
Analysis - Basics
- Identifies
- heat generated by the chemical process
- reversible reaction temperature
- Builds
- virtual heat exchangers
- Designs
- optimal plant topology, through extended pinch
analysis
Trev reversible temperature (no entropy) T
actual working temperature dqchem heat of
chemical process dq heat exchanged with the
surroundings
11ImplementationA) Reversible Temperature
Computation
- zero order approach
- Trev is computed for the entire chemical reactor
- first order approach
- (Trev) in is computed considering an infinitely
small advancement of the chemical process at
entrance - (Trev) out is computed following the same
procedure, but for the exit conditions.
12B) Reactor Replacement Adiabatic (exo case)
13Guideline from Chemical Reactors Energy
Integration (CREI) Analysis
- The CREI analysis guideline emerged from
previous works states to heat up as much as
possible the input of the chemical reactor for
exothermic processes using if possible some low
value utilities or a part of the generated heat
and to generate as much as possible high grade
utility.
14SCWO Flowsheet
15Balanced composite curvesPinch
16Pinch Analysis Flowsheet, 673 K
17Balanced Composite Curves for Chemical Reactors
Energy Integration (CREI)
18CREI Flowsheet, 673 K
19Pinch Analysis Flowsheet T gt 673 K
20CREI Flowsheet, T gt 673 K
21Conditions to be fulfilled for non-adiabatic
cases
- The imposed inlet temperature of the pollutant in
the mixer - The length of the reactor used for the chemical
process (active length) - Pinch both
- CREI one
22Generated Entropy
23Conclusions
- Applying CREI first gives the same scheme with
the cascade pinch/CREI - The generated entropy has practically the same
value after the CREI analysis or after pinch/CREI
analysis - An adiabatic operation of the reactor is
desirable - A better energy-power integration could be done
using a supercritical turbine or an Organic
Rankine Cycle
24Acknowledgements
This work is the result of the cooperation
between VITO, VUB and UPB-CTTIP developed under
the auspices of the bilateral agreement between
the Flemish and the Romanian governments BIL
031326 - Application of chemical pinch technology
in process industries.