MSW Processing- Gasifier Section

Transcription

1 MSW Processing- Gasifier Section Chosen Flowsheet MSW Gasifier SynGas H2S/Solids Water wash Clean Syngas CO Conversion Shifted SynGas CO2 Separation CO 2 Urea H 2 O 2 Urea Plant Air Air Separation N 2 Ammonia Plant NH 3 Argon???

2 MSW Plant SHREDDER AND GASIFIER Metals 8.93 tons/unit time MSW 100 tons/unit time Front-End Sorting and Shredding Refuse Feed tons/unit time Oxygen tons/unit time Pyrolysis Reactor Syngas tons/unit time Water tons/unit time Slag tons/unit time Metals MSW Shredder

3 MSW Plant MOVING BED GASIFIER: Calculate diameter assuming 4 mm diameter pellets with 30% void fraction and 0.5 cm/sec downward velocity of the moving bed. GASIFIER Reference point for diameter: 720 tpd of coal 12 diameter. L/D=

4 Assumptions: - Gasifier produces gases in equilibrium - Pressure is close to atmospheric. - Temperature can be regulated by small & quick quenching - Final quenching to room temperature is needed. Why? How? - For simplicity, we will assume 8% ash (metal carbonates) and tar in the form of elemental C Problems: - Simulators do not have gasifiers - Simulators like Aspen do not use non chemical components, like paper, cellulose, plastics, etc.

5 Typical formulas for materials exist: - Dry Paper: C 6 H 9.6 O 4.6 N S Mixed Plastics: C 6 H 8.6 O Mixed organic wastes: C 6 H 10 O 4. - These are examples. Make sure they are correct How to handle the simulation? - Just obtain a stoichiometrically sound equilibrium composition. Use Gibbs reactor

6 What is the feed to the Gibbs reactor: - An arbitrary mix of gases that mirrors the atom-mol composition of the MSW. - Example (Ash has been already removed). Original mass (100 Kg) 92 Kg left Reduced further by metals and glass. MSW wt% Content wt% Atom-Moles Carbon Hydrogen Nitrogen Sulphur Oxygen Total Moles Extra O2 What is the composition of the mixture of gases that represents the atom-mole amounts? Extra H2O CO CO2 CH4 H2S SO2 NO NO2 H2O H2 C(Tar)

7 What is the composition of the mixture of gases that represents the atom-mole amounts? MSW wt% Content wt% Atom-Moles Carbon Hydrogen Nitrogen Sulphur Oxygen Total CO= moles-moles of CO2 and CH4 chosen. H2S= atom moles of sulfur NO= Atom moles of N moles of NO2 chosen. H2O needs to take into account Moles Extra O2 Extra H2O CO Calc C balance CO chosen CH chosen H2S Calc S balance SO chosen NO Calc N balance NO chosen H2O Calc O balance H Calc N balance C(Tar) chosen CO CO2 CH4 H2S SO2 NO NO2 H2O H2 C(Tar)

8 Simulation Results This is at room temperature, right? Feed Comp Moles CO CO CH H2S SO NO NO H2O H C(Tar) x inlet CO CO CH H2S SO NO NO H2O H C(Tar) T=600 Equilibrium Now you can vary the amount of Oxygen And water added. Also, you can vary the temperature.

9 Temperature? This part is not part of the project. This is at room temperature, right? - From the simulation at a given temperature (600, 700, 800?), one can get the enthalpy of the products. - The gasifier is adiabatic, so the first law says that H prod (T)+H ash (T)=H MSW (25)+H O2 (25)+H H2O (T=??). Looks like the heat of reaction!!! - If we know H MSW (25), then we can vary the temperature of the Gibbs reactor until you get the equality to hold. - What is H MSW (25)? It is the heat of formation of MSW. Is it available? Maybe. - If the heat of formation is not available, the heating values (HHV and/or LHV) is available. These are related to the heat of combustion MSW+ O 2 CO 2 +H 2 O+ nitrogen and sulfur compounds +ash. If the heat of combustion is known and the adiabatic flame temperature is known then the H MSW (25) can be obtained.