title: Catalytic supercritical water gasification of primary paper sludge using a homogeneous and heterogeneous catalyst: Experimental vs thermodynamic equilibrium results.
abstract: H2, CH4, CO and CO2 yields were measured during supercritical water gasification (SCWG) of primary paper waste sludge (PWS) at 450°C. Comparing these yields with calculated thermodynamic equilibrium values offer an improved understanding of conditions required to produce near-equilibrium yields. Experiments were conducted at different catalyst loads (0-1g/gPWS) and different reaction times (15-120min) in a batch reactor, using either K2CO3 or Ni/Al2O3-SiO2 as catalyst. K2CO3 up to 1g/gPWS increased the H2 yield significantly to 7.5mol/kgPWS. However, these yields and composition were far from equilibrium values, with carbon efficiency (CE) and energy recovery (ER) of only 29% and 20%, respectively. Addition of 0.5-1g/gPWS Ni/Al2O3-SiO2 resulted in high H2 and CH4 yields (6.8 and 14.8mol/kgPWS), CE of 84-90%, ER of 83% and a gas composition relatively close to the equilibrium values (at hold times of 60-120min).
authors.affiliation: Department of Process Engineering, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Louw
authors.affiliation: Department of Process Engineering, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
authors.forename: Cara E
authors.initials: CE
authors.lastname: Schwarz
authors.affiliation: Department of Process Engineering, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa. Electronic address: ajburger@sun.ac.za.
authors.forename: Andries J
authors.initials: AJ
authors.lastname: Burger
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D002384:Catalysis; D005740:Gases / Q000737:chemistry; D009532:Nickel / Q000737:chemistry; D010209:Paper; D011188:Potassium / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D002254:Carbonates; D005740:Gases; D012722:Sewage; D014867:Water; D012822:Silicon Dioxide; D009532:Nickel; C037593:potassium carbonate; D000537:Aluminum Oxide; D011188:Potassium
keywords: K(2)CO(3); Ni/Al(2)O(3)–SiO(2); Primary paper sludge; Supercritical water gasification (SCWG); Thermodynamic equilibrium yields