Gasification of New Zealand Coals: A Comparative Simulation Study

Abstract

The aim of this study was to conduct a preliminary feasibility assessment of gasification of New Zealand (NZ) lignite and sub-bituminous coals, using a commercial simulation tool. Gasification of these coals was simulated in an integrated gasification combined cycle (IGCC) application and associated preliminary economics compared. A simple method of coal characterization was developed for simulation purposes. The carbon, hydrogen, and oxygen content of the coal was represented by a three component vapor solid system of carbon, methane, and water, the composition of which was derived from proximate analysis data on fixed carbon and volatile matter, and the gross calorific value, both on a dry, ash free basis. The gasification process was modeled using Gibb’s free energy minimization. Data from the U.S. Department of Energy’s Shell Gasifier base cases using Illinios No. 6 coal was used to verify both the gasifier and the IGCC flowsheet models. The H:C and O:C ratios of the NZ coals were adjusted until the simulated gasifier output composition and temperature matched the values with the base case. The IGCC power output and other key operating variables such as gas turbine inlet and exhaust temperatures were kept constant for study of comparative economics. The results indicated that 16% more lignite than sub-bituminous coal was required. This translated into the requirement of a larger gasifier and air separation unit, but smaller gas and steam turbines were required. The gasifier was the largest sole contributor (30%) to the estimated capital cost of the IGCC plant. The overall cost differential associated with the processing of lignite versus processing sub-bituminous coal was estimated to be of the order of NZ $0.8/tonne.

Influence of the Selected Parameters on the Effectiveness of IGCC System Integrated With CCS Installation

“…For the calculation a pressurised, oxygen-fed, entrained flow gasifier (based on Shell technology, (Cormos, 2012;Maustrad, 2005;Smitha et al, 2008;Sun et al, 2011;Zheng and Furinsky, 2005)), powered with coal with the composition shown in Table 1 was chosen.…”

Conceptual model and evaluation of generated power and emissions in an IGCC plant

“…Gibb's equilibrium models, such as those found in [21,29,30], which use a general equilibrium model, without pre-specified reactions. Kinetic and mass transfer models.…”

“…Liquid sulphur is recovered from reactor outlets using two phase flash units to model the liquid vapor separations. Gas reactor outlets are fed to a series of two equilibrium reactors, which constitute the catalytic stages represented by the chemical reactions (24), (30) and (31). The hydrogenation step takes place in a conversion reactor that considers S 2 and SO 2 conversion into H 2 S (see Eqs.…”

Process simulation study of coal gasification‐based multi‐product plant with electricity and chemical products

“…In the efficiency improvement study, gasification can be employed to combine IGCC with solid oxide fuel cell (SOFC), convert solid fuel to liquid fuel, or produce electricity and chemical products simultaneously . Although the gasification phenomena are complicated to get exact simulation, it is reasonable to simulate final gas compositions with gasification reactions under higher temperature by employing ideal thermodynamics in system‐level simulation models …”