~"'~ AD-E400 371

CONTRACTOR REPORT ARLCD-CR-79017

' ,CALORIMETRY STUDIES OF AMMONIA,

NITRIC ACID, AND AMMONIUM NITRATE

R. T. REWICK

B. J. GIKIS

SRI INTERNATIONAL IMENLO PARK, CA 'i

i. WEISMANPROJECT LEADER, ARRADCOM E

OCTOBER 1979

US ARMY ARMAMENT RESEARCH AND DEVELOPMENT COMMANDLARGE CALIBER

WEAPON SYSTEMS LABORATORYDOVER, NEW JERSEY

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The views, opinions, and/or findings containedin this report are those of the autbor(s) andshould not be construed as an official Depart-ment of the Army position, policy or decision,unless so designated by other documentation.

Destroy this report when no longer needed. Donot return it to the originator.

The citation in this report of the names of com-mercial firms or commercially available pro-ducts or services does not constitute officialendorsement or approval of such commercialfirms, products, or services by the United StatesGovernment.

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I. REPORT NUMBER '2. GOVT ACCESSION NO. 3 RECIPIENT'S CATALOG NUMBER

Contractor Report A.RLCD-CR-79017 i

4. TITLE an ubtite. 5. TYPE OF R R

.CALORIMETRYTUDIES OF AMMONIA, NITRIC ACID, C Fina •" 17AND AMMONIUM NITRATF S.6 PE"• ... I..G. B..REPORT NUMBER

S.AUTHOR() 8. CONTRACT OR GRANT NUMBER(*,

R. T.JRewick, B. .,ýGikis I SRI International D AA' 1 - 72- C-$2I.Ieisman��n/'•rorect ea i, ARRADCOM

9. PERFORMING ORGANIZATION NAME AND AD'.RESS 10. PROGRAM ELEMENT, PROJECT, TASK

SRI International AREA & WORK UNIT NUMBERS

333 Ravenswood Avenue Menl CAPrje tNMenlo Park, CA 94025 Project No. 5762528

II1 CONTROLLING OFFICE NAME AND ADDRESS 0

ARRADCOD , TSD

STINFO (DRDAR-TSS) N. -NUMBER OF P•AW"Dover, NJ 07801 . 23

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ARRADCOM, LCWSL UNCLASSIFIEDManufacturing Technology Division (DRDAR-LCM-PE) IS. DECL ASSI FICATION/ DOWNGRADINGDover, NJ 07801 SCHEDULE

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IIII. YPPLEMENTARY NOTES _-_

IS. KEY WORDS (Continue on :*vetoa aide lf necee•sry and Identify by block nmmber)

Calorimetry Heat of reactionAmmonium nitrate Heat capacityNitric acid Heat of solution•Amonia

20. ABSTRACT r(Cmrtfe m,.re a N "no•a.•r sd iderfiyf by block number)

" Based on calorimetry studies, basic thermochemical data were obtained forthe design of the nitric acid-ammonium nitrate reaction process to be used forthe RDX/iHMX %XA Facility.

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S�CUAiTy CLASSIFICATION OF THIS PAOE(I�en Dare Entered)

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TABLE OF CONTENTS

Page no.

Introduction 1

Experimental Details 1

The Calorimeter 1Reagents 2The Heat of Reaction of NH3 W~ and HNO 3 (2,) 2Thz- He-at of Dilution of HNO3/NH4NO 3 (56.4/42.6 wt %) 9

4The Heat ojf Reaction of 1*13(2) with a Dilute Mix 16

Heat Capacity of H-N0 3/NH4N03 Mix 16

Conclusions and Action Taken 16z

References 17

Distribution List 19

\ TA or

'I.-ee ~ ,

TABLES

1 Summary of calorimetric dataJ

2 Thermochemical cycle for calculating heat ofreaction between NH3(k) and HN03(0.) 10

3 Heat of dilution of mix 13

4 Heat of formation of NH4NO 3 solution 14

5 Heat capacity of mix at 25.4°C 15

FIGURES

1 Outside view of calorimeter reaction vessel 3

2 Inside view of calorimeter reaction vessel 4

3 Heat of solution of NH±4NO 3 (s) in 99.6 wt % 5

HNO3( ) (run no. 6)

4 Integral heat of solution of NHMNO 3 (s) in 11

99,6 wt % HNO 3 (k) versus molality NH4NO 3

5 Integral heat of solution of NH4NO 3 (s) in 1299.6 wt % HNO 3 (s) versus moles HNO3/mole NH4 NO13

..

INTRODUCTIONThe Army is contemplating building another facility (in addi-

tion to the one at Holson Army Ammunition Plant (HAAP)) to manufac-

ture RDX and HMX and its compositions. One of the processes in thismanufacturing operation is the production of ammonium nitrate iii anitric acid solution. The process contemplated for this new facilityhas enough differences from the present operation at HAAP that thebasic thermochemical data of the following reactions are required; aswell as the heat capacity of the mix:

7 NH3(k) + .4NO3 (k)-• NH4NO3 (s) (1)

HIMOS(9) + mix 1 -* mix - HNO 3 (2)

NH (k) + dilute mix 2 -- mix (3)

This report describes the calorimetry work and subsequent calculationsto obtain these data.

EXPERIMENTAL DETAILS

The Calorimeter

Figures I and 2 show photographs of the ca'irimeter reactionvessel used for this study. The reaction vessel is constructed fromDuiimet 20, a stainless steel alloy enriched in Cu and Ni. This alloyis reported in Perry's Chemical Engineering Handbook to be highly re-sistant to corrosion by 100% nitric E-id (51 microns per year at 500 C).Special features of the vessel include a propeller-type stirrer, anampule holder, and an ampule breaker (plunger device designed to breakthe ampule). Aftei loading, the react('r vcs3el is sealed, placed inan insulated Dewar flask, and covered with about 2,700 cm3 of water.Extending through the styrofoam cap of the Dewar flask are the ampulebreaker and stirrer connections, a bath stirrer, a calibration heater,and an M:S-calibratcd platinum resitance thermometer. Calorimetricmeasurements were conducted using well documented procedures (ref 1)that included the application of the NBS heat-leak correction formulas(ref 2). The results oE a typical experiment are shown in figure ?

JNH NO 6 81.77) ENO3. 43 32NH4N03 *(1.77) HNO03

41ASAWMJ-1

Reagents

Concentrated ammonium iydroxide C25.67 wt % NH3 ) was standardizedby potentiometric titration against standard 1 N HCI, For calorimetricmeasurements, samples were transferred by syringe into weighed 4-cm3

glass ampules that were flame-sealed, reweighed, and mounted in afixed position in the sample holder.

Ammonium fi.Ltrate (99.5% assay, Mallinckrodt Chemical Company)was dried for several hours at 1300C and then transferred to a dry boxthrough an antechamber that was evacuated to less than 50 microns ofHg. Glass ampules containing NH4NO3were filled in the dry box and thenflame-sealed under a nitrogen atmosphere. A Karl-Fischer titrationof the NH4 NO3handled under these conditions showed the presence ofless than 0.1% H20. An x-ray diffraction pattern of the dried samplewas identical to the literature spectrum of W NO3.

Anhydrous nitric acid was prepared by distillation of 90% HNO 3

from fuming sulfuric acid (oxides of nitrogen were removed beforedistillation by treatment with urea). Nitric acid samples stored insealed polyethylene bottles in the dark at -800C were transferred bypipette to the calorimeter immediately after thawing to room tempera-ture. The HNO3 content of samples used in the study, determined frompotentiometric titration against standard 1 N NaOH, was 99.6 + 0.2 wt%HNO3. As a measure of tte extent of reaction with the wall oTthe3*calorimeter, HNO3 samples were analyzed following the calorimetric de-termination. After correction for the HN0 3 consumed during the reactionof interest, the analysis of the final composition varied less than 1%fr'om the calculated final composition. In addition, no Fe or Ni was de-tected by atop;ic absorptio- analysis of the NH03 in contact with thereaction vessel.

The Heat of Reaction of NH3 (z) and HN0 3(t)

During a meeting on 2 August 1978 with ARRADCOM; Project Managerof Munitions Production Base Modernization and Expansion; US ArmyFngineer District, Huntsville, Engineering Division; and SRI it wassuggested that direct measurement of reaction (1) would be difficult

because of problems of safety, temperature control, and accurate mea-surement associated with handling ,iquid ammonia. As an alternativeapproach, it was proposed to measure the following reaction:

NH3 -H20(t) + HN0 3 (') -b NH4NO3-H 20-HNO 3 (5)

2

, *w�

-r

p

N )

-4

-y

Figure L Outside view of calorimeter reaction vessel.

3

- A-. 7- - �

-4E-

FP W(N

(N

0 (N to00

CDb

z co

CD

0l CD

100 -~~1 z1-4

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00 -4 4%

%000 -a

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u 0 0 '

4-j m 00 m00 0J m

( 7 0 '

4 -J4

E-

0 144 F, C.) 0'4.1 10 (1

0'0

40 0 '0mcn e c n0 Il 'n0 N.

0o -4 0- '-4 O N 0-

N O4 N O c7 N O N

-c 0 00

00

0 Nt')L

-441

UD CD('

03 04 -44 co 0N) t*- CD0N )

LA. 0D 0 0n 0 00 00

4-)-

0, 0 0 0 0

0 01 01 0 7 0 0 0 0,

0.4 j t0 r- tr-t. L r 0)

04 %0 C; .- 0.-

0 N

0 4 0 0 0 CD 00

0i Nl N 01 0 = 03 0 =' a

t C14C'

41 4 N 0 0 a% 0

u 0 r- aa% n a 000 0 0,ý 0 0 '(d C) a% - q 4 C 0 0 C-4 1-

C-4o 04 0A -4 .?.t-

S 4-)

0z jNU C14 Nl 4JH

70IV90

co.~

4.l

co CAr0o

-~CD 0ý C

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4~C4J .-~ acc00! '-I C>4

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00 0 N

I -4

0 0-1)

0n k0 0)

4o 00

.0 m coK

(v 0

Z I

M oI

CU -. . I~ z o

I *0

To obtain the desired heat of reaction (•HM) of (1), the measured value

for C5) was combined with the AH for the following reactions:R

tant to apply 'HR values for reactions C6) through (8) that are meas-sured or calculated at compatible concentrations with (5). For reac-

H is calculated from literature values (ref 3) to bekcal/mole. Similar information for reactions (7) and (8) is

eiter otavailable or is in concentration ranges that cannot beaccratlyextrapolated to required laboratory conditions. Therefore,

Smeasured for (7) and (8) at the required concentrations forusewitant (5) and (6) to obtain (1). These reactions are summarizedsured 2. calUsing calculated or measured AR values for reactions

(5)thrugh(8) and Hess' law of constant heat summation, AHl-J29 ofreaction (1) was calculated to be -31.755 kcal/mole. 298

The reliability of the data can be assessed from replicatevalues obtained for reaction (5). As shown in table 1, the 95% con-fidence limit of the average value (-42.43 kcal/mole) is + 0.90 kcal/mole. It is estimated that the error introduced from thewater (lessthan 0.02 mole) contained in the 99.6 wt % HN03 used in these measure-ments is less than 0.5 kcal/mole.

The Heat of Dilution of HNO3 04 T3 (56.4/42.6 wt %)

To the best of the investigators' knowledge, the heat of solu-tion of NH4NO3(s) in 99.6 wt c HNO (Zb ) has not been previously reported.

The observed exothermic heat of solution is of theoretical interestsince the solution of most crystalline materials involves the adsorp-tion of heat. The data appear to fit a straight line on a semilogplot (fig 4), which permits an accurate interpolation between concen-trations. In another presentation of the results, the heat of solu-tion per mole Of HN03W is given in figure 5, and the heat of solu-tion at infinite dilution approaches a value of -6.5 kcal/mole NH4NO3.

The heat of dilution of the HNO /NH4 NO mix is calculated from

the thermochemical cycle shown in table 3. The results (-1.38 kcal/mole HN03 (298 K) can also be derived directly from data for the heat

L99

0 c, 4

WI -:T

m - tLC

0) In

m 0 o -

C) +l

4-)

4, 0 C -

o 0 ~ 4 Cj

C'J 'Z C Cl

0CDc C

Q In CDCD L

0 Cý

0 -.

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i" 9

8

7

l, 6\00

5

0z

I 0z 4-J

3< 0

-j00

* 2

0/

MIX COMPOSITIONMOLALITY NH4 NO3 = 9.45AHSOL = -1.68 kcal/mole

10 . I I I I

0 2 4 6 8 10 12

MOLALITY NH4 NO3

Figure 4. Integral heat of solution of NH4NO 3 (s) in

99.6 wt % HN0 3(Z) versus molality NH 4N03.-

K ,

010

o (o

4-0

(N

(N

0y 00

LL 0 E2

-0 0 C)

oo C

(0 if)

(N

N~~- C0 w :(N0

(CONt'HN 3'10AJ/lVDN) iO0SH,7

12

Table 3. Heat of dilution of mixa

Molality (kcal)Reaction NH4N03 (from fie 4)

NH4NO3.(1.68)HN0 3 -) NH4NO3 + (1.68)HNO 3 (9.45) +1.68

NH4NO3 + (1.77)HN0 3 -+ NH4NO3.(1.77)HNO 3 (8.97) -1.80

Sol A Sol B

NH4NO3.(1.68)HNO 3 + (0.087)HNO 3 4 NH4NO3.(1.77)HNO 3 -0.12b kcal/moleNH4NO 3

(11.49)NH 4NO3.(19.31)HNO 3 + HNO 3 -+ (11.49)NH 4NO3.(20.31)HNO 3 -1.38 kcal/moleHNO 3

a"1,00 parts mix + 29.51 parts HNO 3.bAHR = AHf Sol B - AIf Sol A = -1.80 (-1.68) -0.12 (fig 4)

*1000 parts mix + 29.51 parts HNO3.

13

............ .. . . _ _ . ......

LU *

0

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Ur) CO ~

0

0 0

x . ,I~

V) 0,. 4

cr0 44Cr,

*-0

'V) (v -

C-4 =~ r=

0 +r -a

E= =o0 44 Eý =*%

4-c 0 4.) =r- C)- 0

4-) '- 00 rq-z

4-) u CI+~V a 4-.

.0

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+ a) 4-)

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C+ cc cn+ iCr, - 004. .

**- ý m.0c

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__ __ _ __ _ iin~~a 4.j-

! I Table 5. Heat capacity of r1 ix* at 25.4°C m

C, system (heat/*C) Cpmix

Blank + mix -p cal/g/°C

3.057 3.120 0.063 0.47

"*133.30 g, 43.6 wt % 0H4N03/56.2 wt % HN0 3/0.2 wt % H20

I

is

"' EWE

* •,' , .•• , ***- &.-- . • - • -••- • A' ... . .. . .

of solution of NH4NO3 (s) in HN0 3 (,). This calculation involves thedifference in the heats of formation of NH4NO3 dissolved in HNO 3 (fig 4)of the product and the reactant compositions. The importance of thisapproach is that the heat of dilution or concentration of an HN0 3/NH4NO3mix over the composition range studied can be calculated directly fromfigure 4 without recording the separate steps involved. The cycle intable 3 represents the point in the nitric acid-ammonium nitrate reac-tion process where the nitric acid is added.

The Heat of Reaction of NH3(W) with a Dilute Mix

The heat of reaction of NH3 (k) with a dilute mix (molality8.97) to generate the normal mix (molality = 9.45) is calculated fromthe thermochemical cycle shown in table 4. The result (-29.74 kcal/mole) is obtained by first adding the heat of reaction for the formationof NH4NO3 obtained in table 2 to the heat of dilution of NH4NO3 in nitricacid to obtain the normal mix composition. These are represented bysteps 1 and 2 in table 4. Finally, the heat of dilution of ammoniumnitrate in nitric acid to obtain the dilute mix must be added as instep 3. Figure 4 is used to obtain the required heats for steps 2and 3 on a mole of NH4 NO3 basis. These heats are then multiplied bythe number of moles of NH4 NO3 involved as shown in the chemical equa-tions of steps ? and 3. The algebraic sum of the respective heatsgives the overall heat of reaction, and the chemical sum of equations I,2, and 3 gives the overall reaction involved. This reaction will takeplace in the reactor generating NH NO3 in the production facility.

Heat Capacity of HN03/NH4NO3 Mix

The heat capacity of an HNO 3/NH4NO3 mix (56.4 Wt % HNO /43.6 wt %NH4N0 3) was determined experimentally from the difference in heat ca-pacity of the empty reaction vessel and the vessel containing a weighedquantity of the mix. The result of 0.45 cal/g/°C at 25*C (table 5) isclose to that expected for the HNO 3/NH4NO3 system, since both compon-ents have reported equal heat capacities of about 0.4 cal/g/0 C.

CONCLUSIONS AND ACTION TAKEN

The following heat of reaction data pertinent to the design ofa nitric acid-ammonium nitrate reaction process for the RDX/HMX facil-ity were obtained:

1. NH3(W) + (54.48)HNO3.(30.8)NH4 NO3 _-+ (53.48)HNO 3.kcal

(31.8)NH4NO3 AH = -29.74 gm-mol

16

_ _ _ _ _ _ _ _ _ i

2. (11.49)NH4NO 3 *(19.31)HNO 3 + HNO 3 . (11.49)NH 4 NO3.S~kcal

(20.31)HN0 3 AH = -1.38 gjjjol

Also obtained was the heat capacity of the mixture:

43.6 wt % NH4NO3

56.2 wt % HNO 3

0.2 wt % H2 0 0.47 cal0g/0 C

These data were forwarded to the U. S. Army Engineer District,Huntsville, Alabama, for their design of the NA/AN process to be usedin the manufacture of RDX/HMX.

REFERENCES

1. A. Weissberger and B. Rossiter, Eds., Physical Methods ofChemistry, Part V: Determination of Thermodynamic and SurfaceProperties, Wiley-Interscience, New York, 1971, p 347

2. R. S. Jessup, National Bureau of Standards Monograph 7,

Precise Measurement of Heat of Combustion with a Bomb Calori-meter, 26 February 1960

3. National Bureau of Standards Technical Note 270-3, 1968

LJ

17

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CommanderUS Army Armament Research and

Development CommandIATTN: DRDAR-LCM-PE (4)

DRDAR-LCM-PDRDAR-LCM-E (2)

Dover, NJ 07801

Project Manager for Munition ProductionBase Modernization and ExpansionUS Army Materiel Development and

Readiness CommandATTN: DRCPM-PBM-EE (4)Dover, NJ 07801

US Army Engineer District, HuntsvilleATTN: Engineering Division, HNDED-ME (3)

HNDED-PM (2)P.O. Box 1600 West StationHuntsville, AL 35807

CommanderHolston Army Ammunition PlantATTN: SARHO-E (3)Kingsrort, TN 37662

DirectorUS Army Industrial Base Engineering ActivityATTN: DRXIB-MT (2)Rock Island, IL 61299

Ralph M. Parsons CompanyATTN: K. Lewis (5)100 West Walnut StreetPasadena, CA 91124

SRI InternationalATTN: B. Gikis (5)

R. Rewick (S)Dr. D. D. Cubicciotti (3)

333 Ravenswood AvenueMenlo Park, CA 94025

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