Conceptual Design of a Mid-Sized Semi-Closed Oxy-Fuel Combustion Combined Cycle

Abstract

This paper presents the study of a mid-sized semi-closed oxy-fuel combustion combined cycle (SCOC-CC) with net power output around 108 MW. The paper describes not only the power balance and the performance of the SCOC-CC, but also the conceptual design of the SCOC turbine and compressor. A model has been built in the commercial heat and mass balance code IPSEpro to estimate the efficiency of semi-closed dual-pressure oxy-fuel combustion combined cycle using natural gas as a fuel. In order to obtain the real physical properties of the working fluids in IPSEpro, the code was linked to the NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP). The oxy-fuel turbine was modeled with the in-house Lund University package LUAX-T. Important features such as stage loading, loss modeling, cooling and geometric features were included to generate more accurate results. The oxy-fuel compressor has been modeled using a Chalmers university in-house tool for conceptual design of axial compressors. The conceptual design of the SCOC-CC process has a net efficiency of 47%. The air separation unit and CO2 compression reduce the cycle efficiency by 10 and 2 percentage points, respectively. A single-shaft configuration was selected for the gas turbine simplicity. The rotational speed chosen was 5200 rpm and the turbine was designed with four stages. All stage preliminary design parameters are within ranges of established industrial axial turbine design limits. The main issue is the turbine exit Mach number; the stage must be lightly loaded in terms of pressure ratio to maintain the exit Mach number below 0.6. The compressor is designed with 18 stages. The current value of the product of the annulus area and the blade rotational speed squared (AN2) was calculated and found to be 40·106.

High-efficiency low LCOE combined cycles for sour gas oxy-combustion with CO2 capture

“…Details of the power The CPU (CO 2 Purification Unit) and ASU (Air Separation Unit) power inputs are fairly similar for all of the cycles. These efficiency penalties for these two components agree with what is found in the literature 320 [21]. But a slightly smaller power is required in the CPU for the SO x Removal cycle because the SO x compounds are already being removed in the main cycle before entering the CPU.…”

“…This cycle configuration is similar to the methane combined cycles modeled in [12,18,19,21,22,23]. The only difference being the fuel composition (70% CH 4 , 15% H 2 S, 15% CO 2 ) and the assumption of acid resistant materials being used for all the low temperature cycle components.…”

“…For the Graz cycle [12,16,17], both H 2 O and CO 2 are used as diluents. Finally in the Semi-Closed Oxy-fuel Combustion Combined Cycles (SCOC-CC) [12,16,18,19,20,21,22,23], only CO 2 is recycled back to the combustor by condensing and removing the H 2 O from the flue gases. 25 The focus of this paper is on sour gas combined cycles; the previous paper [1] focused on the sour gas water cycles.…”

Oxyfuel combustion for CO2 capture in power plants

“…In a single-shaft design for power generation a gear between turbine and generator is needed. Sammak et al (2011) present a preliminary compressor design for a geared mid-sized SCOC-CC at approx. 100 MW e with a pressure ratio of 37 and 18 stages at 5200 rpm at comparable loading coefficients as Woollatt and Franco (2009).…”

Conceptual Mean-Line Design of Single and Twin-Shaft Oxy-Fuel Gas Turbine in a Semiclosed Oxy-Fuel Combustion Combined Cycle

“…Bolland and Mathieu [7] showed that the difference in power between dual-and triple-pressure steam cycles is very small. In a previous study, Sammak et al [8] investigated a single-shaft oxy-fuel gas turbine with a rotational speed of 5200 rpm. Ulizar and Pilidis [9] studied twin-spool oxy-fuel gas turbines with a compressor turbine (CT) rotational speed of 5000 rpm and a power turbine (PT) rotational speed of 3000 rpm.…”