2005 OBP Bi-Annual Peer Review

In situ Causticizing for Black Liquor GasifiersScott Sinquefield, IPST

Xiaoyan Zeng, IPSTAlan Ball, IPST

James Cantrell, Jacobs Engineering

Thermochemical PlatformNovember 15, 2005

Overview

• Project start: Oct 1, 2002• Project end: Oct 31, 2006• 70% complete

• Process Integration• Validate integrated black liquor

gasification and causticiziation processes.

• $600,000• DOE $480,000• IPST/Jacobs $120,000

• Funding in FY04: $137,402• Funding for FY05: $165,605• Requested FY06: $176,978

Timeline

Budget

Barriers

• Institute of Paper Science at GA Tech

• Jacobs Engineering

Partners

Detailed Investigation

Impetus

Entrained-flow gasifier950C, O2- or air-blown, ~5 sec residence time

Steam reformer~600C, fluidized bed ~50 hrs residence time

Both of the current, actively marketed, black liquor gasification technologies results in an increased causticizing load which must be addressed

Project Goals and Objectives

• Phase 1: Direct- and auto-causticization processes (i.e. borates, titanates, and manganates) have been demonstrated effective on pure Na2CO3 in the laboratory. We test the processes on black liquor at realistic gasification conditions and determine which chemistries hold promise. Both equilibrium modeling and experimentation are employed. Successful processes move on to phase 2. (IPST) Go/No go

• Phase 2: For the successful causticizing chemistries we confirm that concentrated caustic can be recovered, suitable for a pulping liquor (i.e. white liquor). We also identify feasible ways of purging non-process elements (“dregs”). (IPST) Go/No go

• Phase 3: For the methods passing Phase 2 (if any), we determine the most rational ways of integrating them into the mill and perform economic evaluations. (Jacobs + IPST)

Project Strategic Fit

Black liquor gasification (BLG) promises significant market incentives such as combined cycle power generation, syn-gas to chemicals, and high-yield pulping synergies. However, pulping chemicals must still be recovered, and the inherent increase in causticizing load must be addressed:

• Partial in situ causticizing would offset the load increase for a full scale gasifier utilizing the existing lime cycle; while complete causticizing would eliminate the petroleum-intensive lime cycle:

• A 1000 ton/day pulp mill uses 90,000 bbls/yr #6 fuel oil to fire the kiln. (=$3.78 Million/yr at current prices)

• Total US kraft pulp production is 156,700 ton/day. 100% adoption = 14 Million bbls/yr fuel oil saved.

(=$650 Million/yr in fuel saved)

• BLG for incremental capacity on a boiler-limited mill will require equivalent incremental causticizing capacity.

• Pilot demonstration is easy with either a gasifier or a recovery boiler

• IPST membership includes P&P companies committed to BLG

Project Approach

Chemistry for the titanate case; others are analogous

Sodium is bound up by titanates within the gasifier:

Na2CO3+3 TiO2(s) Na2O.3TiO2(s)+CO2 (g)

7Na2CO3+5(Na2O.3TiO2)(s) 3(4Na2O

.5TiO2)(s)+7CO2(g)

Na2O6TiO2(s)+Na2CO3(s) 2(Na2O3TiO2)(s)+CO2(g)

[Abbreviated NT3, N4T5, NT6]

The caustic is later recovered by hydrolysis:

3(4Na2O.5TiO2)(s)+7H2O 14NaOH(aq) + 5(Na2O

.3TiO2)(s)

2(Na2O3TiO2) (s)+H2O 2NaOH (aq)+Na2O6TiO2 (s)

Project Approach cont.

IPST’s Pressurized Entrained Flow Reactor (PEFR) was built for gasification research in a variety of gas environments at pressures to 30 bar, temperatures to 1500C, and residence times to 8 seconds.

Phase 1

We begin by gasifying mixtures of black liquor and the causticizing agents (titanate, borate and manganate) at industrially realistic gasification conditions (i.e. entrained flow at 950C, and steam reforming at 600C) and determine which chemistries work. We also employ equilibrium modeling with FactSage 5.1 for comparison.

Causticizing conversion is determined by the carbonate content remaining in the char (solid) phase compared to char from un-doped liquor.

Project Approach cont.

Phase 2

The gasified char is hydrolyzed to recover the caustic. The leachate solution is analyzed by ICP for metal species, and titrated to verify the amount of hydroxide. The leached solids are characterized by SEM-EDS, XRD, ICP, and BET to close the material balance and narrow the dregs removal options between chemical and physical processes; then test.

Air, O2, steam

Gasifier

Mixing

Leaching

Dregs Purge(?)

Dregs Purge(?)

Black liquor

Char

Leached solids

Raw White Liquor

White liquor for pulping

Raw Syn Gas

CleanedTitanate orManganate

Project Approach cont.

Phase 3

The final phase includes mill integration and economic evaluations by Jacobs Engineering

Project Approach cont.

Phase 3

Economic evaluation

Project Tasks

• Phase 1: We must first demonstrate a high degree of causticizing conversion for each of the chemistries. 85% causticizing efficiency is common for the current lime cycle technology. If not, we abandon the option (Go/No go)

• Phase 2: We must then confirm that we can hydrolyze the char and get hydroxide back. The causticizing agent must be in its starting form to be used again. If not, we abandon the option (Go/No go). Also the dregs must be removable from the cycle or they will accumulate.

• Phase 3: For any processes that remain, they must be such that they can be integrated to the mill and they must be economical or they have little value to the industry. Jacobs Engineering assumes the lead in this phase.

Project Collaboration

Collaboration and Tech Transfer

• Coordinate with BLG vendors/users to include in situ causticizng in pilot trials and incremental capacity applications

• Publish results in open literature

• Jacob’s can utilize the design data on its gasification projects.

• Revisit overall BLG (Low Temp and High Temp) economics for kraft mill applications incorporating results of viable in situ causticizing. Should help with justification for incremental units as well as replacement systems.

• Apply results to conventional recovery boilers for mills with bottlenecked lime kilns. [Note that borates have application in Tomlinson-based recovery systems as well]

• On-going exchange of results with Adrian van Heiningen (U. of Maine) who leads a project focusing on titanates and high-yield pulping for low temperature steam reforming.

• Potential customers are pulp producers, bio-refineries, and electric utilities with the intent of building, owning, and operating a gasification-based recovery island with combined cycle power generation while processing pulping liquors for an adjacent pulp mill.

• Threshold for adoption is IRR=25% (Larson, et.al. ‘A Cost Benefit Assessment of Black Liquor Gasification’, 2003). Larson found the IRR to be 20%, but without considering in situ causticizing, environmental benefits, energy credits, or external social benefits.

Market & Customers

• In situ causticizing processes provide an additional economic incentive for adoption of black liquor gasification, and therefore have the same window of opportunity; that being that the technology must be ready for deployment as aging recovery boilers are replaced or undergo major rebuilds.

• Competing technologies are state-of-the-art Tomlinson recovery boilers and the supposed “high efficiency recovery boiler”. While compatible with conventional pulp mills, they do not integrate well with multi-product biorefineries. Gasification offers greater flexibility over a wide range of process/product variations.

• Market effects would include reduced demand for #6 fuel and lime, and increased use of TiO2, and/or NaBO2, and/or Mn3O4

• With regard to economics, the savings in offset fossil fuel (#6 fuel oil) alone justifies the use of in situ causticizing.

Competitive Advantage

Project Stage

In situ causticization processes have been proven in the lab to convert Na2CO3 to NaOH. In this work we test them with black liquor at realistic gasifier conditions, investigate non-process element removal, and perform economic and mill integration evaluations. Are the processes truly viable?

Progress and Accomplishments

BLG w/Titanate for 100% Causticizing: CO3 conversion in PEFR at 950C

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0 0.5 1.0 1.5 2.0

CO2 Partial Pressure, Bar

% C

arb

on

ate

Co

nv

ers

ion

Equilibrium (FactSage) prediction of CO2 levels for O2-blown BLG above 5 bar

Equilibrium (FactSage) prediction of CO2 levels for air-blown BLG, 1-5 bar

Results show that titanate direct causticizing will work for high temperature black liquor gasification at low to moderate pressures, but not at 20 bars

(unless the CO2 can somehow be maintained at a lower level)

Progress and Accomplishments

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 0.1 0.2 0.3 0.4CO2 Partial Pressure, Bar

Ca

rbo

na

te C

on

ve

rsio

n

Equilibrium (FactSage) prediction of CO2 levels for steam BLG (reforming) at 1.0 bar and above.

BLG w/Titanate for 100% Causticizing: CO3 conversion at 600C in steam + CO2

Titanate direct causticizing was not effective for the steam reforming case at 600C. However, modeling suggests that it would work at 650C and above.

Progress and Accomplishments

BLG w/Borate for 20% Causticizing: CO3 conversion in PEFR at 950C

0%

5%

10%

15%

20%

25%

30%

35%

40%

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

CO2 Partial Pressure, Bar

% C

arb

on

ate

Co

nv

ers

ion

Equilibrium (FactSage) prediction of CO2 levels in product gas over range of reasonable O2/Fuel ratios for air-blown BLG at 1.67 bar.

Borates added for 20% conversion will be effective for atmospheric pressure entrained flow gasification (such as the Chemrec booster at New Bern)

Progress and Accomplishments

0%

5%

10%

15%

20%

25%

30%

35%

40%

0 0.1 0.2 0.3 0.4CO2 Partial Pressure, Bar

Ca

rbo

na

te C

on

ve

rsio

n

Equilibrium (FactSage) prediction of CO2 levels for steam BLG (reforming) at 1.0 bar and above.

BLG w/Borate for 20% Causticizing: CO3 conversion at 600C in steam + CO2

Borates added for 20% conversion did not prove to be effective for the 600C steam reforming case. Modeling suggests that 925C would be required.

Progress and Accomplishments

Gas Conditions

Fixed (i.e. char)

carbon in smelt

Experimental causticizing conversion

50%H2O 0.00% 100%

50%H2O 0.05% 100%

50%H2O 0.01% 100%

50%H2O+10%CO2 0.03% 95%

50%H2O+10%CO2 0.02% 100%

Manganates proved to be 100% effective for steam reforming at 600C,but at 950C (not shown) they showed zero conversion

Progress and Accomplishments

Phase 2. Summary of non-process element removal results

• Concentrated caustic (white liquor) can be made but will require staged leaching of titanate char

• Leaching of manganate chars consistently yielded 40% of expected hydroxide. We are working to resolve the discrepancy.

• Hydration of borate chars produced high caustic recovery

• ICP analysis of char, leachate, and leached solids produced good material balance closure.

• Most of the B, Cr, Si, and V split to the leachate phase

• The remaining non-process elements favor the solid phase. SEM-EDS will determine the number of phases

Progress and Accomplishments

Phase 2. Non-process element removal options

• Viable techniques depend on fate of NPE’s (i.e. dissolved versus solid phase and number of solid phases)

• Ion exchange

• Mg(OH)2 complexing

• Acid titration

• Laminar air classification (size/density difference)

• Density-based separation for slurries

• APIC jig air pulses produce bed with density gradient

• Knelson/Falcon concentrators centrifugal

Future Work

• Further characterize the leached solids to determine how non-process elements are distributed with respect to phases. This will narrow the removal options to test

• Resolve the hydroxide material balance for the manganate case. If hydroxide cannot be balanced with carbonate, then must abandon this option.

• Test the chemical processes for non-process element removal in the lab.

• Test borates at 100% conversion for HTBLG.

• Mill integration study, including: design basis, material & energy balances, process scope descriptions, flow diagrams, major equipment, +/-25% capital estimate.

• Economic evaluation.