Page 24 - Impiantistica Italiana Maggio Giugno 2014

The essential objectives of the gas cleaning test
runs in FW’s scope were to demonstrate the per-
formance of the gas coolers and the hot gas flters
in long-term operation and to determine the design
basis for this equipment.
The cumulative operation hours of the oxygen-
steam gasifcation were more than 9000 hours by
the beginning of June 2011 and for the slip-stream
gas cleaning plant the operation hours were more
than 5500 hours.
As an example, the main raw gas components of
the oxygen-steam gasifcation during a test run in
Fig. 5 - Process chain of the handling systems and the scrubber. Foster Whee- spring 2011 were CO , H and CO, which together
2
2
NSE demo plant ler also executed themajority of the process design covered around 75-80% of the total dry gas.
including the control system. Process design of the
reforming unit and the complete design of further
gas ultra cleaning and the integration of the FT test 2.3.4. 3D CFB gasifcation model
unit were taken care of by NSE. Foster Wheeler has also developed, in co-opera-
tion with Lappeenranta University of Technology
(LUT), a three-dimensional (3D) modeling tool for
2.3.3. Experimental studies CFB gasifers. The model combines fundamen-
The test runs were carried out to optimize the tal continuum equations and experimental cor-
gasifer process parameters for producing good relations. The modelling is conducted by utilizing
quality raw gas for the follow-up process. Tars, control volume method to discretize the balance
light hydrocarbons, HCN, NH , H S and COS equations in steady state. The three-dimensional
2
3
(CarbOnyl Sulphide) and fy ash/particulates were balance equations are solved by using frst order
analyzed from the raw gas, as well as the gas main upwind scheme and applying Gauss-Seidel met-
components CO, CO , H , CH and H O. Carbon hod with successive overrelaxation.
2
2
4
2
conversion of the gasifer was also determined. The model has been developed to solve full-scale
Test runs included testing at different gasifcation CFB furnaces and to calculate balance equations
temperatures ranging from 860 to 940 °C and dif- for gas, solids, fuel and sorbent reactions and spe-
ferent oxygen/steam ratios. The oxygen content cies, homogenous reactions and species of 16
of the fuidizing agent into the wind box was vari- gaseous components and in addition the tempe-
ed between 23% and 50%-w, typical value being rature feld and heat transfer within the gas-solid
around 45%-w. Fuel consisted of different types suspension and to the walls. The model also re-
of woody biomass: wood chips, frst felling wood, cognizes the combustion of char, evaporation of
bark and forest residues. moisture and devolatilization of the volatile matter

Fig. 6 - The Cartesian,
structured mesh of the model
and calculated temperature
profle

20 Impiantistica Italiana - Maggio-Giugno 2014