Feasibility study for supercritical water gasification of black liquor

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Abstract

The purpose of this study is to investigate the feasibility of supercritical water
gasification (SCWG) of black liquor integrated to a pulp mill. SCWG has potential as an alternative treatment for black liquor, thus enabling the conversion of pulp mills to multiproduct biorefinery plants. The current literature has investigated the yields and efficiencies, and this study investigates the economic analysis. The scenario in this study is to integrate SCWG process to a Kraft pulp mill with the capacity of 400000 ton dry pulp/year. 10 tons of black liquor is produced per ton of pulp and 20 percent of weak black liquor is transferred to the SCWG plant, i.e. 100000 kg/h weak black liquor is processed in SCWG plant. SCWG plant is designed for four different cases: for either energy or hydrogen production, in either Inconel 625 or stainless steel reactor. The energy production cases have the issues of high heat need in the reactor. In contrast, the hydrogen production cases provide reactor inlet with higher temperature, thus reducing heat needed in the reactor. In addition, even though Inconel reactor provides higher hydrogen yield or hot gas efficiency, the cases with stainless steel reactor is more profitable due to the difference in material price. The most profitable case is hydrogen production with stainless steel reactor at 700 °C: requiring 31.19 M$ total investment and providing return of investment in 4.1 years. These calculations assumed that the cooking
chemicals are completely recovered in brine and char discharge of the reactor.
Nevertheless, the sensitivity analysis shows that the process can be profitable with up to 20 % loss in cooking chemical. The profitability is affected very slightly by capacity change; however, the process becomes unfeasible for small capacity, i.e. not encouraging the integration with small-capacity non-wood mills. Several factors are to be investigated further for more precise feasibility study: mainly price of black liquor and heat integration.

Details

Original languageEnglish
Title of host publicationVenice 2016 - Sixth International Symposium on Energy from Biomass and Waste. Proceedings
Publication statusPublished - 2016
MoE publication typeB3 Non-refereed article in conference proceedings
EventInternational Symposium on Energy from Biomass and Waste - Venice, Italy
Duration: 14 Nov 201617 Nov 2016
Conference number: 6
http://venicesymposium.it/

Conference

ConferenceInternational Symposium on Energy from Biomass and Waste
Abbreviated titleVENICE
CountryItaly
CityVenice
Period14/11/201617/11/2016
Internet address

ID: 9420285