Biogas Purification by Adsorption. and novel Washing Systems

Transcription

1 INNOGAS Symposium, 26./27. Oct Biogas Purification by Adsorption and novel Washing Systems Reiner Staudt Institut für Nichtklassische Chemie e.v. Permoserstraße 15, D Leipzig, Germany

2 Institut für Nichtklassische Chemie e. V. Institute of Non-classical Chemistry at the University of Leipzig Institut für Nichtklassische Chemie e.v. Founded in 1997 Research Institute serving the general public Cooperation with the University of Leipzig PD Dr. habil Reiner Staudt Director Institut für Nichtklassische Chemie e.v. Permoserstr. 15, Leipzig Business segments Thermophysical data on chemical media of pure substances and compounds Sorting (exhaust air, wastewater) High-temperature reactions Ultrasonic & microwave applications Catalytic Oxidation Stable isotope analysis Adsorption Supercritical fluids

3 Institut für Nichtklassische Chemie e. V. Institute of Non-classical Chemistry at the University of Leipzig Thermophysical data on chemical media Data of pure components [kg/m3] 80 Data of von compounds p = 3 MPa Kinetic Data 60 Selectivity density 40 Excess values 20 Isotope effects y 0.6 CO [ ] e 1 ressur p Pa] p [M 7 Process data Pressure-density correlation of a CO/ H2 compound

4 Institut für Nichtklassische Chemie e. V. Institute of Non-classical Chemistry at the University of Leipzig Supercritical Fluids (SCFs) Thermophysical data of SCFs Sorting and extraction using SCFs Solubility of gases and vapours in polymers Solubility of surfactants in gases Modification of SCFs Kinetics of Reactions Autoclave System

5 Catalytic Oxidation High-temperature reactions Adsorbate analysis Institut für Nichtklassische Chemie e. V. Institute of Non-classical Chemistry at the University of Leipzig

6 Institut für Nichtklassische Chemie e. V. Institute of Non-classical Chemistry at the University of Leipzig Stable Isotope Analysis Isotope ratio of cotton Ivory Coast Mali 2 H, Pima 92 Senegal California Uzbekistan Pima O,

7 High-temperature Reactions II Chemical Characterization of high-temperature material via reference reactios (Pyrolysis, Metal Dusting) Researches regarding the pyrolysis of technical feedstock fractions (Evaluation of coke-forming tendency, product profiles) Influence of additives on the pyrolysis of hydrocarbons (Evaluation of effectiveness of coke forming inhibitors) Thermal treatment of material surfaces

8 Stable Isotope Analysis Isotopenwerte von Baumwollproben Isotope ratio of cotton Elf enbeinküst e Mali 2 H, Pima 92 Senegal Calif ornia Usbekist an Pima O,

9 Impedance Measurement in a Pilot Plant Pilot plant for VOC recovery from waste air

10 Institut für Nichtklassische Chemie e. V. Institute of Non-classical Chemistry at the University of Leipzig Adsorption Adsorption of pure gases, gas compounds and vapours 12 Adsorption of water 10 Characterization of porous solids 8 6 Kinetics of adsorption Diffusion Characterization of catalysts Excess amount adsorbed [mmol/g] Concentration ych Pressure [MPa] Swelling of polymers Adsorption of CO2/ CH4 mixture to activated carbon at 25 C

11 Basics of the Adsorption Technique gas phase adsorption (exothermic) desorption (exothermic) adsorbate adsorbate adsorbate interface homogeneous heterogeneous active centres solid adsorbent

12 Basics of the Adsorption Technique Application of Adsorption in Process Engineering Gas purification: < 10 % of the gas flow are adsorbed Application: gas drying, solvent recovery, exhaust gas purification,... Gas separation: Application: > 10 % of the gas flow are adsorbed air decomposition for the recovery of nitrogen, oxygen, or hydrogen,

13 Basics of the Adsorption Technique Separation Effects of Adsorption Steric effect ( filtering action ): Molecules with a diameter smaller than the pore diameter are adsorbed Equilibrium effect: A few components of the compound are stronger linked than others (e.g. polar molecules are stronger adsorbed to zeolite than nonpolar molecules). Kinetic effect: components are adsorbed at different rates and accordingly through the combination of the effects

14 Basics of the Adsorption Technique Essential Steps of the Adsorption Process: Charging: Adsorbent is charged with gas flow, separation of the components of the compounds using adsorption Regeneration: Removal f adsorbed molecules (desorption), so that adsorbent is available for new charging.

15 Basics of the Adsorption Technique Adsorption Process Temperature Swing Adsorption: Desorption with an increase of temperature Pressure Swing Adsorption (PSA): Desorption with pressure reduction Pressure Swing Adsorption (PSA): Adsorption at overpressure (3-5 bar a ), regeneration with ambient pressure. Vacuum Pressure Swing Adsorption (VPSA): Adsorption at little overpressure (1,2-1,6 bar a ), regeneration in vacuum (0,2-0,5 bar a ).

16 Basics of the Adsorption Technique A to B: Pressure swing or rinsing with inert gas A to D: Temperature swing A to C: Rinsing with hot inert gas Loading [Nl/kg] A T1 5 B D 0 C T2 > T Partial pressure [mbar]

17 Experiment - Gravimetry CAL CAL Calibration of Instrument... electromagnet permanent magnet position sensor adsorbent sample Measurements: Pressure Temperature Mass increase of sample Calculations: Adsorption isotherm Isosteric Heat Kinetics

18 Experiment - Pure Substane Isotherms Isotherms to A zeolite of n-butane, n-hexane, n-octane, n-decane 2,00 2,50 amount adsorbed [mmol/g] 1,50 1,00 0,50 amount adsorbed [mmol/g] 2,00 1,50 1,00 0,50 0,00 0, ,001 0,010 0,100 1,000 pressure [mbar] pressure [bar] n-butane; n-hexane; n-octane; n-decane at 28 C -,-,-,- Parameter adjustment with Langmuir equation

19 Experiment Breakdown Curves Concentration 8 Calibration of Instrument... Time Measurements: Temp. C Temp. C Temp. C Temp. C CO Concentration Mass flow Time Temperature Pressure bar Temp. C 1 Gas supply 2 Flowmeter 3 Pressure/temp. gauge 4 Adsorber 3 5 Thermocouples 6 Capacitor 7 Impedance analyser 8 Concentration detector (TCD) 2 1 He Calculation: Adsorption isotherm Isosteric Heat Kinetics

20 N 2 / CO 2 / CH 4 (10% / 40% / 50%) in AK Norit NR1 Extra 40 Temperaturverlauf Temperature Temperature Temp. of der the Thermoelemente thermocouples in in C C Zeit time in in Sekunden seconds mass AK = 75,9 g, p = 1,2 bar

21 N 2 / CO 2 / CH 4 (10% / 40% / 50%) in AK Norit NR1 Extra 1 Durchbruchskurve Breakdown curve Concentration Konzentration C/Co N2 CH4 CO time Zeit in in Sekunden seconds mass AK = 75,9 g, p = 1,2 bar

22 N 2 / CO 2 / CH 4 (25% / 25% / 50%) in AK Norit NR1 Extra Concentration C/Co Konzentration C/Co N2 CH4 Durchbruchskurve Breakdown curve CO Zeit in Sekunden time in seconds mass AK = 75,9 g, p = 1,2 bar

23 Measuring of Compound Adsorption Isotherms 94,22547 g microbalance Volume Gravimetry: Measurements: p, T, m magnetic coupling T p Calculation: m fl 1, m fl 2, m 1, m 2 sample storage vessel 1 IS 1 injection IS 2 systems storage vessel 2 gas supply gas circulation pump T Volumetry with GC: Measurements: p, T, c Calculation: m fl 1, m fl 2, m 1, m 2 T gas chromatograph vacuum pump

24 CH 4, H 2 S and CH 4 /H 2 S Mixture on Zeolite surface excess, n ex [mmol/g] pure gases: surface excess CH 4 surface excess H 2 S data fit with 2-sites Langmuir AI methane concentration, y CH pressure, p [MPa] mixture: partial surface excess CH4 for 0.5 and 1.0 MPa total surface excess CH 4 +H 2 S for 0.5 and 1.0 MPa prediction of partial surface excess CH 4 from pure gas fit for 0.5 and 1.0 MPa prediction of total surface excess from pure gas fit for 0.5 and 1.0 MPa

25 CH 4 /CO 2 /N 2 on AK Norit R1, T = 298 K nch4, nch4 + nco2, ntot [mmol/g] y CH4 = 0,72 / y CO2 = 0,12 / y N2 = 0, Pressure [MPa]

26 Pressure Swing Adsorption Plant Product gas Storage Control valve Solenoid valve Check valve Air Exhaust gas Compressor Vacuum pump

27 Basics of the Adsorption Technique Parameters of Pressure Swing Adsorption Processes Product rate: PR y PROD m V Adsorbent PROD Yield: AB y y PROD FEED V V PROD FEED Energy value: EW Energy demand y V PROD PROD

28 Components of a Pressure Swing Adsorption Plant Characteristc of a Vacuum Pump Suction capacity [m^3/h] Saugvermögen Suction capacity Energiebedarf Energy demand Energy demand [kw] ,2 0,4 0,6 0,8 1 Pressure difference [bar]

29 Dual Bed Process for adsorptive Gas Separation Product Produkt A B Gasgemischt mixture Abgas Exhaust gas Step 1: Pressure build-up Adsorber A Evacuation Adsorber B

30 Dual Bed Process for adsorptive Gas Separation Produkt Product A B Gasgemisch Gas mixture Exhaust gas Abgas Step 2: Production Adsorber A Evacuation Adsorber B

31 Dual Bed Process for adsorptive Gas Separation Product Produkt A B Gas Gasgemisch mixture Abgas Exhaust gas Step 3: Rinsing Adsorber A Adsorber B

32 Dual Bed Process for adsorptive Gas Separation Product Produkt A B Step 4: Pressure Equalization Adsorber A Adsorber B

33 Dual Bed Process for adsorptive Gas Separation Pressure Curve Dual Bed VPSA Process Pressure [mbarg] Adsorber B Adsorber A Speicher Storage Time [s]

34 Dual Bed Process for adsorptive Gas Separation Product Rate depending on the Cycle Time 1,1 1 0,9 0,8 0,7 0,6 0,5 0, cycle time [s]

35 Results of Simulations and Measurements Product Rate depending on Process Pressures: Simulations and Experiments in a Dual Bed O 2 VPSA Plant 1,0 rel. production rate PR/PRMAX 0,9 0,8 0,7 0,6 0,5 0,4 Experimente Experiments mbar(g) Adsorption pressure mbar(g) Adsorptionsdruck mbar(g) mbar(g) Adsorptionsdruck Adsorption pressure desorption pressure [mbar g ]

36 Results of Simulations and Measurements rel. product yield AB/ABM AX 1,0 0,9 0,8 0,7 0,6 0,5 Yield depending on Process Pressures: Simulations and Experiments in a Dual Bed VPSA Plant Experimente Experiments mbar(g) adsorption Adsorptionsdruck pressure mbar(g) adsorption pressure mbar(g) Adsorptionsdruck desorption pressure [mbar g ]

37 Biogas Purification Purification Stage Hydrogen sulfide Ammonia Mercury Halogenated hydrocarbons Carbon dioxide Adsorption Process Catalytic H 2 S Oxidation on activated carbon Acid impregnated activated carbon Chemisorption on adsorbents impregnated with sulfur Adsorption on activated carbon/ molecular sieves Desorption with water vapour/ inert gases PSA with carbon molecular sieve Other Processes Washings Water or acid wash Oxidierende Wäschen Washings with organic solutions CO 2 scrubbing with water, zeolite, membrane process

38 Energy Costs: PSA Pressure Swing Scrubber Loss of production in percent Loss of chemically bound energy Loss of methane

39 Advantage Biogas Purification Dry process, therefore no wastewater is generated Disadvantages Relatively high power consumption Disposal of activated carbon necessary H 2 S concentration must not be higher than 400 mg/m³; therefore a rough sulfur removal is necessary High losses of methane is another disadvantage of this process

40 Biogas Purification Output Quality The following quality parameters can be kept using the PSA technology: CH 4 concentration in raw gas 65 %, in product gas > 97 % H 2 S concentration in raw gas 300 mg/nm³ in product gas < 5mg/Nm³ Dew point at ambient pressure of 65 C

41 Pressure Swing Adsorption Summary: Pressure swing adsorption technology is suitable for the separation of substances which arise in high concentrations Characteristic of DWA processes is the cyclic alternation of adsorption and desorption. Generally plants with several fixed-bed adsorbers are applied. Parameters of DWA processes: PR, AB, EW Process parameters: cycle time, adsorption and desorption pressure, feed temperature,... Loss of methane Purity of product gases

42 1. Short introduction on Ionic Liquids Ionic Liquids are fused or liquid salts, containing only ions Most common ILs are liquid at or below room temperature Main properties: They are non-volatile - no measurable vapor pressure are non-flammable are thermally stable (up to 200 C, or higher) have high heat capacities can be designed to dissolve a broad variety of chemical substances

43 1. Short introduction on Ionic Liquids Characterization of ILs Hydrophobicity: the immiscibility with water Viscosity: mpas (can change with impurities and solved gases) Solubility of gases, liquids and solids Stability (thermal, electrochemical) toxicology

44 2. Sorption processes using ILs Gas separations: ILs show high selectivity for certain gaseous species (e.g. removal of CO 2 and H 2 S from natural gas) Membrane technology: Supported Liquid Membrane (SLM) Purification of gases: Gas absorption, removal of unwanted impurities Extraction with ILs: Removal of S-, N- and Cl-compounds from hydrocarbon mixtures Homogeneous and heterogeneous catalysis using ILs Gas storage

45 2. Sorption processes using ILs Purification of natural gas: Pressure swing process + Large capacity change of IL for CO 2, moderate compression work - CO 2 recovery at low pressure

46 2. Sorption processes using ILs Purification of natural gas: Temperature swing process + CO 2 recovery at high pressure, relatively low maximum temperature, marginal liquid pumping power required - Low capacity change for CO 2 compared to pressure swing process

47 4. Results of sorption measurements for ILs Sorption Measurements: Pure gas CO 2 in [BMIM][PF6] Spec. Mass Uptake [g/g] Pressure [bar] 25 C 40 C 50 C 60 C [BMIM][PF6] = 1-Butyl-3-methylimidazolium hexafluorophosphate, M = g/mol

48 4. Results of sorption measurements for ILs Sorption Measurements: Pure gases CH 4 and CO 2 in [BMIM][PF6] Spec. Mass Uptake [g/g] t = 50 C CO 2 CH Pressure [bar] [BMIM][PF6] = 1-Butyl-3-methylimidazolium hexafluorophosphate, M = g/mol

49 4. Results of sorption measurements for ILs Sorption Measurements: Gas mixture CH 4 / CO 2 in [BMIM][PF6] Spec. Mass Uptake [g/g] t = 50 C Gas Dosing Ratio: 50% wt CH 4-50% wt CO 2 total mass partial mass CH 4 partial mass CO Pressure [bar] [BMIM][PF6] = 1-Butyl-3-methylimidazolium hexafluorophosphate, M = g/mol

50 4. Results of sorption measurements for ILs Sorption Measurements: Gas mixture CH 4 / CO 2 in [BMIM][PF6] Spec. Mass Uptake [g/g] t = 50 C Gas Dosing Ratio: 90% wt CH 4-10% wt CO 2 total mass partial mass CH 4 partial mass CO Pressure [bar] [BMIM][PF6] = 1-Butyl-3-methylimidazolium hexafluorophosphate, M = g/mol

51 4. Results of sorption measurements for ILs Sorption Measurements: Gas mixture CH 4 / CO 2 in [EMIM][PF6] Spec. Mass Uptake [g/g] t = 50 C Gas Dosing Ratio: 90% wt CH 4-10% wt CO 2 total mass partial mass CH 4 partial mass CO Pressure [bar] [EMIM][PF6] = 1-Ethyl-3-methylimidazolium hexafluorophosphate, M = g/mol

52 4. Summary Conclusion to the gravimetric/ volumetric sorption method: Sorption equilibria and kinetics-of pure gases and mixtures-can be measured in a large pressure and temperature range with magnetic suspension balances [BMIM][PF6] and [EMIM][PF6] show high capacity and selectivity for CO 2. Sorption capacity of [BMIM][PF6] is ~40wt% higher than [EMIM][PF6] Measurements of sorption kinetics have to be improved (sample holder)