Dr. Benjamin R. Vaughan, Zach Higginbotham, Dr. Anand … · Dr. Benjamin R. Vaughan, Zach...

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Laboratory Scale Nitration of Cellulose as a Cost Effective Risk Mitigation Tool for the Production of Nitrocellulose at Radford Army Ammunition Plant

Dr. Benjamin R. Vaughan, Zach Higginbotham, Dr. Anand Mangalam, Leslie Ben’Ous, Peter Bonnett

May 13,2009

Laboratory Scale Nitration of Cellulose as a Cost Effective Risk Mitigation Tool for the Production of Nitrocellulose at Radford Army Ammunition Plant

Dr. Benjamin R. Vaughan, Zach Higginbotham, Dr. Anand Mangalam, Leslie Ben’Ous, Peter BonnettMay 13,2009



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OUTLINE

NITROCELLULOSE MANUFACTURING AT RFAAP

LAB SCALE NITRATION / STABILIZATION

PART I: LAB SCALE NITRATION STUDY

• MIXED ACID COMPOSITION

• KEY INPUT VARIABLES – EFFECTS

PART II: CELLULOSE SOURCE STUDY

• KRAFT VS SULFITE PULP

• ACADEMIC WORK


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ACID BOILING

POACHING& BLENDING

ACID

NITRATION

CELLULOSE

REFINING

ANALYSIS

NITROCELLULOSE MFG. 101

OO

O O

O

O

OONO2

O2NO

ONO2

O2NO

O O

O2NOONO2

O2NO ONO2

O2NOONO2

ONO2O2NO


4

ACID BOILING

POACHING

NITRATION

CELLULOSE

REFINING

LABSCALE NITRATION


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PART I: NC REACTION CONDITIONS STUDY

1.Demonstrate that laboratory nitration can be used as a tool to aid production with risk mitigation associated with sensitive products

2.Understand how mixed acid composition

and key process input variables (KPIV)

change our

nitrocellulose in terms of:

• % Average Nitrogen

• Acetone solubility, and Ether / Alcohol Solubility

• Processing of NC


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Grade D Water Sensitivity Models

Water sensitivity models developed for Grade D and E nitrocellulose products

AFY09 NC production data fits within lab scale model’s 95% prediction limits for Grade D NC

Process data fits have led the NC technical team to use less water set changes during manufacturing

Lab data shows linear response of %N to water at current process acid composition

Good fit of data to simple model

14.2 14.3 14.4 14.5 14.6 14.7

12.0

12.1

12.2

12.3

12.4

% Water

%N

Resp

onse

%N Response = 18.6145 - 0.446 % Water

S = 0.0285671 R-Sq = 89.7 % R-Sq(adj) = 88.2 %

RegressionLab Scale

95% PI

Grade D NC % Water in Nitrating Acid Sensitivity

Scale ModelProduction

GRADE D WATER SENSITIVITY AT CONSTANT NITRIC ACID CONTENT

12.00

12.05

12.10

12.15

12.20

12.25

12.30

12.35

% WATER IN ACID

% N


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Nitration with various mixed acids

PRODUCTION IS CURRENTLY USING THE MODELS DEVELOPED IN THE LAB TO ADJUST NITRATING ACIDS FOR PRODUCTION OF GRADES D

AND E NITROCELLULOSE

%WATER

%N

ITR

IC

14.714.614.514.414.314.2

75

70

65

60

55

50

45

40

35

30

Grade D Nitrating Acid Sensitivity

% WATER

% N

ITR

IC

14.814.714.614.514.414.3

75

70

65

60

55

50

45

40

35

30

> – – – – – < 10.0

10.0 10.510.5 11.011.0 11.511.5 12.012.0 12.5

12.5

%N

Grade E Nitrating Acid Sensitivity

INCREASING Δ 0.5 % INCREASING Δ 0.5 %

INC

REA

SIN

G Δ

45 %

INC

REA

SIN

G Δ

45 %


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KEY PROCESS INPUT VARIABLES AFFECTING ATK NC

VARIABLE

(NITRATING ACID MAKEUP FIXED)

RESPONSE

AI EAS %N

ACID \

CELLULOSE

TEMP.

TIME

CHIPS OVER FIBERS

Run Time (min) Temp (ºC) A/C Ratio Cellulose %N AI EA %Sol %N AI EA %Sol

1 HIGH LOW HIGH Chips 12.051 0.21 99.70 12.315 0.93 98.932 HIGH HIGH HIGH Fibers 12.038 0.19 99.71 12.251 0.59 98.283 MID MID MID Fibers 11.740 0.59 98.70 12.182 0.22 99.184 LOW HIGH LOW Fibers 11.740 0.91 97.78 12.040 1.16 97.575 HIGH HIGH LOW Chips 11.819 0.10 99.94 12.105 0.07 99.666 HIGH LOW LOW Chips 11.804 2.30 97.78 12.038 4.15 95.467 LOW HIGH HIGH Chips 12.043 1.14 98.65 12.371 0.93 99.148 LOW LOW HIGH Fibers 11.809 1.93 93.71 12.235 2.50 93.729 LOW LOW LOW Chips 11.714 15.68 79.66 11.865 11.94 86.9210 MID MID MID Chips 11.985 0.26 99.74 12.306 0.14 99.80

GRADE E GRADE D


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PART II: CELLULOSE SOURCE STUDY

Answer two Questions:

1.

Is it feasible to make nitrocellulose from Kraft paper? Which pulp candidates look most promising?

2.

Why do similar pulps nitrate so differently? What are the key cellulose characteristics influencing nitration?

•Hemicelluloses content

•Crystallinity

•Fiber wall thickness

•Tree species used

•Sheet Physical Properties


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TWO MAJOR PULPING PROCESSES

SULFATE (KRAFT)

•Basic digestion

•Universal process for recovery of cooking chemicals

•Dominant process

•Cost ~ $ -

0.20 / lb

•Use most types of trees

SULFITE

•Acidic digestion

•Limited recovery of acid gas

•Mills diminishing

•Cost ~ $baseline

•Use limited tree species


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NITRATION QUALITY AND SOLUBILITY

12.2

12.3

12.4

12.5

12.6

12.7

12.8

0.0 0.5 1.0 1.5 2.0 2.5% Acetone Insolubles

% N

itrog

en

SULFITESULFATE

%N (FeSO4) %AI %EAS

SULFITE A 12.68 0.2 99.8SULFITE B 12.28 0.6 98.9SULFITE C 12.23 1.7 97.1SULFITE D 12.53 0.5 99.3SULFITE E 12.55 0.1 99.9SULFITE F 12.29 1.0 98.4SULFITE G 12.71 0.2 99.9SULFITE H 12.34 1.4 97.9SULFATE A 12.57 0.6 99.3SULFATE B 12.62 0.7 99.1SULFATE C 12.37 2.0 97.5SULFATE D 12.54 0.9 98.9SULFATE E 12.61 0.1 99.8SULFATE F 12.68 0.3 99.8

SEVERAL OF THE SULFATE PULPS TESTED TO DATE APPEAR TO HAVE PROPERTIES THAT MEET MILITARY GRADE NC SPECS

% NITROGEN = 12.6 +

0.1% , ACETONE INSOLUBLES < 0.4%


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FIBER QUALITY

10 100 1000

0

2

4

6

8

10

FINES

SULFATE-E SULFITE-A

PER

CEN

T

FIBER LENGTHW

FREE FIBERSSAMPLE >850 um 500 - 849 um 250 - 499 um FINES < 200um

SULFITE A 28% 26% 11% 31%SULFATE E 0 7% 20% 18%

PARTICLES

SULFATE-E IS EASILY SEPARATED INTO

FIBERS AND HAS A LOW PERCENT FINES

(µm)


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WOOD PULP FIBERS

Resin (Extractable) –

can survive the pulping process

Lignin –

(binder) likely removed during the pulping process

Hemicelluloses (polysaccharides) –

can survive pulping process

Alpha Cellulose –

survives pulping process

micro fibrils

Hemicelluloses bind elementary fibrils

elementary fibrils (cellulose)

fiber


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CRYSTALLINITY % AND HEMICELLULOSE %

XRD SULFATE PULP - E

14.798 16.38718.898

22.37

10 15 20 25 30 350

1020304050607080

01020304050607080

10

30

50

70

90

10

30

50

70

90XRD SULFATE - E NITROCELLULOSE

12.699

19.832

10 20 30 40-5

0

5

10

15

-5

0

5

10

15

0

5

10

15

20

0

5

10

15

20

60% CRYSTALLINITY 5% CRYSTALLINITY

SULFITE PULPS SULFATE PULPSAVG HEMICELLULOSES = 5% AVG HEMICELLULOSES = 19%

NEITHER CRYSTALLINITY OR HEMICELLULOSES CONTENT APPEAR TO BE MAJOR FACTORS IN THE NITRATABILITY OF CELLULOSE


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CONFOCAL RAMAN MICROSCOPY

Nitrate Stretches

Ram

an intensity

z

SURFACE

INTERIOR

cellulose fiber

WE ARE COMPARING THE NITRATION LEVEL AT DIFFERENT DEPTHS WITHIN THE FIBER WALL FOR DIFFERENT PULP SAMPLES


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CONCLUSIONS

•WE HAVE BEEN ABLE TO PERFORM NITRATION EXPERIMENTS AT THE LAB SCALE WHICH WOULD HAVE BEEN DIFFICULT, TIME CONSUMING, AND EXTREMELY EXPENSIVE AT THE PRODUCTION SCALE.

•LAB SCALE NITRATION HAS BEEN AN EFFECTIVE METHOD FOR TUNING NITRATION CONDITIONS FOR THE PRODUCTION SCALE PROCESS.

•LAB SCALE NITRATION IS HELPING ATK TO ASSESS FUTURE SOURCES OF CELLULOSE FOR NC PRODUCTION AS WELL AS ANSWERING SOME FUNDAMENTAL QUESTIONS .


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ACKNOWLEGMENTS

We would like to thank PM Joint Services and ARDEC for funding the cellulose source study portion of this research.

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