Development of a process simulation model for energy analysis of hydrogen production from underground coal gasification (UCG)by Aman Verma, Babatunde Olateju, Amit Kumar, Rajender Gupta

International Journal of Hydrogen Energy

Text

u ro (U , Depar

Alberta T6G2G8, Canada b Department of Chemical and Materials Engi reserved.

Introduction

Around 2.52 GJ of H2 energy is required to upgrade one cubic meter of bitumen to SCO [2]. Steammethane reforming (SMR) is the dominant H2 production pathway in Alberta and leads to se (GHG) emissions, from 8.9 to 14.21 kg of CO e per kg of H produced [2e8]. To put om SMR accounts for g1 GHG emissions in 2010, the Alberta oil o Alberta's total GHG f GHG emissions, the f a 50% reduction in projected business-as-usual GHG emissions in 2050, which is around 200 million tonnes in GHG emissions reduction [9].

Therefore, there is justification to explore and study an * Corresponding author. Tel.: þ1 780 492 7797; fax: þ1 780 492 2200.

E-mail address: Amit.Kumar@ualberta.ca (A. Kumar). 1 Well-to-upgrading emissions are those associated with bitumen extraction and upgrading to SCO. In absolute numbers, 0.25 tonnes unt of H2 to upgrade one cubic meter of bitumen [2e6].

Available online at www.sciencedirect.com

ScienceDirect w. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n en e r g y 4 0 ( 2 0 1 5 ) 1 0 7 0 5e1 0 7 1 9of CO2 will be emitted if SMR is used to produce the required amoCanadian crude oil production from the oil sands is projected to rise from 1.8 million barrels per day (bpd) in 2012 to 3.2 and 5.2 million bpd in 2020 and 2030, respectively [1]. The production of hydrogen (H2), required to upgrade bitumen to synthetic crude oil (SCO), will increase in a similar fashion. 2 2 things into perspective, H2 production fr around 43% of the total well-to-upgradin the Canadian oils sands industry [2]. In sands industry contributed around 23% t emissions [9].With a focus on reduction o

Government of Alberta has set a target oa significant amount of greenhouse houCarbon capture and sequestration (CCS) the pressure swing adsorption (PSA) unit has a major effect.

Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rightsa r t i c l e i n f o

Article history:

Received 13 November 2014

Received in revised form 24 June 2015

Accepted 27 June 2015

Available online 23 July 2015

Keywords:

Underground coal gasification (UCG)

Modeling

Energy analysis

Hydrogen productionhttp://dx.doi.org/10.1016/j.ijhydene.2015.06.1 0360-3199/Copyright © 2015, Hydrogen Enerneering, University of Alberta, Edmonton, Alberta T6G2G8, Canada a b s t r a c t

This paper presents amodel to perform energy balances and estimate hydrogen conversion efficiency from UCG-based syngas. The model was developed for H2 production from UCGbased syngas with and without CCS, along with the co-production of electricity and steam in a conventional combined cycle plant. In this paper, at base case conditions (H2O-to-O2 injection ratio of 2 and a steam-to-carbon ratio of 3), the coal-to-H2 conversion efficiency is estimated to be 58.1% forUCGwith andwithout CCS. For the plant configuration involvingno

CCS, in addition to H2 production, approximately 4.7% of coal energy is converted to electricity that is exported to thegrid. In the caseofUCGeCCS, aminor energypenalty is incurred; wherein theelectrical energyexportedperunit coal energy is around2.4%,withaCO2capture efficiency of 91.6% being achieved. The H2 conversion efficiency decreases with rise in H2Oto-O2 injection ratio, but increases with fall in steam-to-carbon ratio. Effect of ground water influx in UCG on the H2 conversion efficiency is minor, whereas H2 separation efficiency ina 4-9 Mechanical Engineering Building tment of Mechanical Engineering, University of Alberta, Edmonton,Aman Verma a, Babatunde Olateju a, Amit Kumar a,*, Rajender Gupta bDevelopment of a process sim energy analysis of hydrogen p underground coal gasification journal homepage: ww49 gy Publications, LLC. Publlation model for duction from

CG) elsevier .com/locate/heished by Elsevier Ltd. All rights reserved. through technology like underground coal gasification (UCG) [12,14]. In UCG, gasifying agents (a combination of eitherwater and oxygen, steam and air, steam and oxygen, or water and

Nomenclature

ASU air separation unit bpd barrels per day i n t e rn a t i o n a l j o u r n a l o f h y d r o g e n en e r g y 4 0 ( 2 0 1 5 ) 1 0 7 0 5e1 0 7 1 910706CC combined cycle

CCS carbon capture and sequestration

CO2e carbon dioxide equivalent

CRIP controlled retractable ignition point

ECBM enhanced coal-bed methane

EOR enhanced oil recovery

FUNNEL-EGY-H2-UCG FUNdamental eNgineering principlEs-based modeL foralternate, less GHG-intensive, hydrogen production pathway for the bitumen upgrading industry.

Coal reserves in Alberta are estimated to be in the range of 2e3 trillion tons (Tt) [10e13]. Of the total reserves, there is the potential to recover around 0.62 Tt (or 25% of total reserves) by surface and undergroundmining [13]. There is an opportunity to retrieve the remaining 75% of the un-minable coal reserves2 estimation of EnerGY consumption and production in hydrogen (H2) production from

Underground Coal Gasification

GHG greenhouse gas

GJ gigajoule

GT gas turbine

HP high pressure

HRSG heat recovery steam generator

HT high temperature

HX heat exchanger

IGCC integrated gasification combined cycle kWh kilowatt hour

LHV lower heating value

LP low pressure

LT low temperature

MDEA methyl diethanolamine

MEA monoethanolamine

MPa megapascal

MW megawatt

PSA pressure swing adsorption

SCG surface coal gasification

SCO synthetic crude oil

SMR steam methane reforming

SRR syngas reforming reactor

SOFC solid oxide fuel cell

ST steam turbine

Tt trillion tons

UCG underground coal gasification

WGSR water gas shift reactor he electrical energy exported per unit coal energy hh coal to hydrogen conversion efficiency 2 Initial studies have suggested that three coal zones in Alberta e Ardley, Horseshoe Canyon, and upper Mannville e are suitable for UCG. These three zones constitute around 54% of the total coal reserves. Owing to greater depth, upper Mannville (which has around 16% of the total coal reserves) is the most favorable coal zone for UCG in terms of ground water protection and unwanted overburden subsidence [12].air) are injected into a coal seam, and syngas is produced through chemical reactions that normally occur in surface coal gasifiers [15,16]. This produced syngas can be used to produce electricity, hydrogen, liquid fuels, etc. [15,16]. In a world of anthropogenic induced climate change, UCG has been deliberated as a clean coal conversion technology and a carbon neutral energy pathway [7]. This is due to the fact that while in operation, UCG does not compromise the economic viability and maintains a negligible GHG footprint, especially when combined with CCS [7,17]. UCG is not only a pragmatic technology for clean coal conversion but also has several economic advantages over surface coal gasification (SCG) [14,15,18,19]. UCG significantly reduces the cost of upstream operations such as coal mining, coal handling, coal transport, and coal gasifiers, and leads to low fugitive emissions, low dust, no ash residues, and reduced noise pollution [14,15,18,19]. However, implementation of UCGeCCS technology on an industrial scale remains a challenge in order to gain the merits over other fossil fuel based pathways, especially SMR, for H2 production. Some of the challenges to adopt