High-Performance Nano-bonded Refractories for a Wide Temperature Range

High-performance Nano-bonded Refractories for a Wide Temperature Range* M. A" L. Brau!io, V. C" Pandolfelli, J" Medeiros, J. B. Gallo

tr

tnergy savings, sate operations, cost reductions and friendly environment are relevant topics for a sustainable industrial growth. ln order to overcome these challenges, breakthrough innovation by suitable materials microstructure engineering is a key issue. Bearing in mind that technological advances must mingle basic and applied science, this work addresses the development of a nano-engineered bonded refractory for FCC petrochemical units and alumina calcíners"

mina particles I8l, they show higher sinterat lower temperatures which can

ability

speed up the refractory's densiÍication in the usual temperature range of the target applications (800-1250 "C). Based on these aspects, this work addressed

the design of a novel engineered refractory castable by using colloidal binders and

a

transient sintering additive, able to induce

As most of

densification at lower temperature and result in high performance materials for FCC

fulfill the sintering requirements at lower temperatures. This novel refractory comprises the use of colloidal binders and additives, in order to provide densification in lower temperatures. Considering the out-

focused on the application requirements and

commercial refractories show densification above ,l300'C, a different composition approach was designed aiming to

units and alumina calciners. This approach, typical temperatures, led

standing performance attained by these castables (high erosion, hot mechanical and thermal-shock resistances in a wide temperature range), an increase in equipment working life is expected, reducing

,n. r..*urOub,.

t'r

tla,una Craup

'j56\-905

The improvement oí the operational formance

of

petrochemical fluid

per-

catalytic

than

that.

(entet,CENPFS) ) 27

commonly bonded with calcium aluminate

B'azi

rein-

have also been used [1,2]. As hydraulic binders impose specific processing restric-

continuous efÍorts to maximize the campaign and reduce the unit stops must tions, mainly on drying due to their hydrate conducted. The working life of the refrac- decomposition [3, 4], colloidal silica or alutories used as lining in such equipment mina became a potential technological alter-

be

is one of the critical constraints that limits the unit working time. This aspect is a consequence of the low availability of high performance materials for these applications, as the steel-making refractory market represents about 75 % of

comshow at tempeÍatures above

lkedeiros

Petrobras, Research and

These conventional refractory castab|es are

cracking units (FCCU) or alumina refineries cement, that leads to ceramic bonds at high can result in a reievant impact on their temperatures. However, over the last years, spective production chains, as the lost non-cement bonding systems (hydratable come due to a production halt can reach alumina, phosphates, colloidal silica, etc.)

valuesclosetousD0,5mjllion/d.Therefore,

ccl'0s

5áo

native to minimize this shortcome 15,61.

Due to the typical temperature decomposition proíile oí cement or hydratable alumina hydrates, a decay in the mechanical

strength

at

intermediate temperatures

(600-loo0'c) is

generally observed

sP

Brazi,

.Jarivaldo

1 lntroduction

A. L. Braulto l,ctar C. Pdnoottelti

Mater als lvlr.' oslructural F ngneerinq

odu,t'on nu', ally operate at temperatures lower

to materials with

[7],

43 05) fii6

le

Develapnent

t,11pi'n

I

Jorge B. Gallo

Alcoa Latin Anerica and Caribbean 371 19-90A Po os de Caldas Brazi|

Corresponding aulhol. M. A. L. Braulio E-mai1. [email protected]

Keywords: colloidal binders, densification, erosion and thermai shock resistances

Received: 28.12.2012 Accepted:15.01.2013

.

The paper was presented at ALAFAR

in

the overall market, Ihus, refractories monly used in steel shops, which

whereas colloidal binders can keep or even

Cancün/MX in Nov 201 2 and was awarded

densification

improve this property at this temperature

W]th the 1'' prize

range. Furthermore, as these binders are

2012

'1300

"c, are used in these units that

gener_

refractories woRLDFoRUM s

oí the ALAFAR

Award

stable suspensions oí nano-scaled siIica/aIu-

(2013) t2l

75

,

:

Jr' I

i

-CB

+

SA *CB

+

SA

+

-c B + SA 6l E 5l

PA *REF-FCCU

50

40

o o E

Eso

6=

=

;,20 o ín = 0

T'

o

E

o

u.l

500 550 600 650 700 750

*CB

+

SA

+

PA *REF-FCCU

.l 3l ,+

'i

0r

500 550 600 650 700 750

800

Temperature ['C]

Temperature ["C]

800

Fig. 1 Hot rnodulus oÍ rupture (HMOR) and eroded volume as a function oí typical petrochemical ternperatures (500 800 "C) Íor the designed compositions (CB+SA or CB+SA+PA) and Íor a commercial reference (REF-FccU)

outstanding thermo-mechanical performance (erosion resistance, hot mechanical strength and thermal shock resistance),

water) was

oí 5,3

mass-% for the colloidal

elastic modulus measurements (bar reson-

loidal silica one. The gelling additive used

C1'l98 standard) as a function of the thermal cycles (0, 2, 4 and 6), The

hig{"-pu'ity magnes

source

number of cycles was limited to 6 as the

Refratários

rnost relevant mechanical damage took

alumina system and 5,0 mass-% Íor the col-

a

a

ance, ASTM

pointing out a potential for Ionger refractory

was

working lííeand lower maintenance stops as

(9B mass-%

in these units erodible particles are conveyed

s.Á/BR)' For_:the CAC-bonded castables,

at speeds as high as 50 m/s and are also

4,4 mass-% of water was added to attain

ln order to evaluate the formation of tran-

prone to sudden temperature changes.

the same above-mentioned initial freeJlow

sient or permanent liquid and the castables'

value and 0,2 mass-% of a polycarboxylate

densification, hot elastic modulus measure-

2 Materials and techniques

Mqo, Magnesita

dispersant (BASflDE\ was added

to

place mainly in the initial cycles (