RUNAWAY PHENOMENA AND THERMAL EXPLOSION I. Di Somma*, D. Spasiano**, R. Marotta**, R. Andreozzi**

and V. Caprio** *Istituto di Ricerche sulla Combustione (CNR), P.le V. Tecchio, 80, 80125,

Napoli, Italia ** Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione

industriale, Università di Napoli Federico II, P.le V. Tecchio 80, 80125 Napoli, Italia

0

2

4

6

8

10

12

14

16

0 10 20 30

q (W

/g)

t (min)

v=5 K/minv=7.5 K/minv=10 K/minv=12.5 K/min

350

450

550

650

0 200 400 600 800

T (K

)

t (min)

experimental datacalculated data

Comparison between experimental and calculated data (without any parameter adjustment):

Ø  ISOTHERMAL RUNS Varying Temperature

Ø  CALORIMETRIC RUNS

An EXPLOSION is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the

release of gases.

Deflagration/ Detonations

(gas and / or dust)

Thermal explosions: runaway reaction (gas and / or solid and / or liquid)

Explosion due to loss of control of a chemical reaction (they occur in containers in which take place chemical reactions)

Thermal runaway is a process by which an exothermic reaction goes out of control, often resulting in an explosion. Thermal runaway occurs when the reaction rate increases due to an increase in temperature (often caused by failure of the reactor vessel's cooling system), causing a further increase in temperature and hence a further increase in the reaction rate. Many industrial-scale and oil refinery processes have some level of risk of thermal runaway. These include hydrocracking, hydrogenation, alkylation (SN2), oxidation, metalation and nucleophilic aromatic substitution. Thermal runaway may result from unwanted exothermic side reaction(s) that begin at higher temperatures, following an initial accidental overheating of the reaction mixture (this scenario was behind the Seveso disaster).

In the case of runaway phenomena the detailed study of the thermal and kinetic behavior of the reacting system is of great interest for industrial applications

EXPERIMENTAL APPROACH •  Define and quantify the exothermicity of the phenomena

•  Assess the stability of the species that are or could be involved

EXPERIMENTAL EQUIPMENT

A process deviation is assumed: Loss of cooling power

increase in T: start of side reactions

Chemical characterization: to identify all the species involved and the reaction network linked to the process.

Thermal and kinetic characterization: to estimate thermal and kinetic parameters related to the reaction network identified.

Construction of a detailed model able to predict the behavior of the system at varying conditions

1. Magnetic Sirrer 2. Bulk 3. Jackett 4. In cooling fluid 5. Out cooling fluid 6. Recover System 7. Thermocouple 8. Data Acquisition

Radex oven Differential scanning calorimeter

PHITEC calorimeter

5-NITROSALICYIC ACID (5-NS): 5-NS is an important intermediate for pharmaceutical industries. The corresponding amine (mesalazine) is used as active species for the treatment of various pathologies such as ulcerative colitis. Its production through nitration processes using the classic mixed acid results into yields lower that 50% and difficulties for the separation of the reaction mixture. A literature survey indicated that there was still a need to find new nitrating systems to overcome the difficulties associated with current production processes.

The characterization of its thermal decomposition in cumene is of interest for industrial applications

MODEL DEVELOPMENT

•  I. Di Somma, R. Andreozzi, M. Canterino, V. Caprio, R. Sanchirico – AIChE Journal, 2008, 54(6), 1579. •  I. Di Somma, R. Marotta, R. Andreozzi, V. Caprio – J. Hazard. Mater., 2011, 187, 157. •  Di Somma I., Marotta R., Andreozzi R., Caprio V. – Ind. Eng. Chem. Res, 2012, 51 (22) , 7493. •  Di Somma I., Marotta R., Andreozzi R., Caprio V.– Process. Saf. Environ., 2013, 91, 262.

CUMYLHYDROPEROXIDE (CHP): Organic peroxides and hydroperoxides are largely used in chemical industry. Most of them are characterized by a strong tendency to undergo exothermic thermal decomposition, often resulting in runaways: a characterization of their reactivity is important for the safety of their industrial applications. CHP is an important intermediate for the production of phenol, acetone and dicumylperoxide. It is produced through the oxidation with air of cumene. Incidents have been documented in the oxidation reactors, vacuum evaporator and storage tanks.

The investigation aimed at studying kinetics and the safety aspects of the nitration process of salicylic

acid by means of the system nitric acid/acetic acid -0,1

0

0,1

0,2

0,3

0,4

0,5

0 50 100 150 200t [min]

C [m

ol/l]

5-Nitrosalicylic Acid

3,5-Dinitrosalicylic Acid

Picric Acid

2,4-Dinitrophenol

285

295

305

315

325

335

345

355

365

375

0 40 80 120 160t [min]

T [K

]

ADIABATIC RUNS ISOPERIBOLIC RUNS

•  R. Andreozzi, V. Caprio, I. Di Somma, R. Sanchirico - J. Hazard. Mater., 2006, 134, 1-7. •  R. Andreozzi, M. Canterino, V. Caprio, I. Di Somma, R. Sanchirico - J. Hazard. Mater., 2006, 138(3), 452. •  R. Andreozzi, M. Canterino, V. Caprio, I. Di Somma, R. Sanchirico - Org. Process Res. Dev., 2006, 10, 1199 •  R. Andreozzi, M. Canterino, V. Caprio, I. Di Somma, R. - J. Chem. Eng. Data., 2007, 52(1), 122-125.

METHYL M-NITROBENZOATE (NB): NB is a useful starting material for the preparation of dyes and crop agent. This important intermediate is currently obtained through the nitration of methyl benzoate by means of mixed acid. It is well-known that, being nitrations exothermic reactions, runaway phenomena can occur during these processes as the result of polynitration and/or side reactions which take place when thermal control of the process is lost.

ISOPERIBOLIC RUNS

0

0,2

0,4

0,6

0,8

1

1,2

0 50 100 150

C  [m

oli/l]

t  [min]

To=400  K3NMB

3NBA

3,5DNMB

3,5DNBA

345

355

365

375

385

395

0 50 100 150

T  [K]

t  [min]

experimental

calculated

ISOTHERMAL RUNS

The reaction network through which the system could evolve following the loss of thermal control or the uncorrect feed of the reagents is completely

characterized. Also the nitric acid decomposition in mixed acid was studied

from a chemical and a kinetic point of view.

•  Di Somma I., Marotta R., Andreozzi R., Caprio V. – Org. Process Res. Dev., 2012, 16, 2001−2007. •  Di Somma I., Marotta R., Andreozzi R., Caprio V. – Chem. Eng. J., 2013, 228, 366–373.