SIC Refractory Castable

7/25/2019 SIC Refractory Castable

1/5

Innovationfuture driven I-06

NEW SILICON CARBIDE CONTAINING REFRACTORY CASTABLE

FOR RESOLVING PROBLEMS IN CEMENT KILN

Chanvit Chawengkul1 Thanapong Prasertphol 2 Punyoot Huantanom3

(1)

Senior Researcher, The Siam Refractory Industry Co. Ltd., Thailand(2) Researcher, The Siam Refractory Industry Co. Ltd., Thailand(3) Researcher, The Siam Refractory Industry Co. Ltd., Thailand

ABSTRACTA major and frequent problem occurring in the outlet zone and burner pipe of cement rotary kilns are thermo-chemical and

mechanical wear which shortens the life of refractory monolithic linings to less than 1 shutdown (4-6 months). The loads generally act onthe refractory lining come from abrasion of clinker ball, abrasion and chemical reaction of clinker dust, and thermal cycling of secondaryair from cooler.

To find a solution to such problem, a new and highly thermal spalling resistance property silicon carbide containing refractorycastable has been developed. It also helps resist chemicals attack of alkali and clinker during the operation, thereby formation of

protective film on surface of lining. The important features of silicon carbide containing refractory castable enabling it to overcome theproblems at the outlet zone and burner pipe of cement rotary kilns are its high level of hardness, outstanding mechanical strength at

elevated temperature, excellent thermal shock resistance etc.The development of silicon carbide containing refractory castable was started from applying QFD and DOE for finding the

optimum content of silicon carbide in order to help solving problem of refractory in these areas. Silicon Carbide is the main material togenerate thermal spalling resistance property as well as its abrasion resistance. Special additives were studied and experimented to

preserve the good properties of silicon carbide in high oxidation atmosphere. Thermal spalling resistance of silicon carbide containingrefractory castable is relatively higher than other types of refractory castable. The abrasion resistance of this castable has been improvedwhich also related to amount of silicon carbide in the recipe.

The performance of newly developed silicon carbide containing refractory castable after several trials at SCG cement kilns has

showed an obviously improvement of service life at outlet zone and burner pipe up to 1 shutdown.

Keywords: Thermal spalling, Silicon Carbide containing refractory castable, Monolithic

INTRODUCTIONRegarding high competition of cement market, cement manufacturers must cut down their operating cost and prolong kiln

operation for high productivity. Kiln operation with high running factor is targeted and needed for all cement manufacturers. Frequent

break down time is not preferred. Generally, mechanical and electrical problems are main factors of break down time. Another factor was

shut down of relining refractory bricks which also affected cement production loss. This major relining refractory should be done atabout once a year. Several minor shut down times of refractory works basically must be avoided. So that, these minor works could affectthe running factor of the kiln and need to be resolved.

Surveying customers needsAccording to continuous development of refractory materials with advanced technology and TQM concept of Siam Refractory

people, High alumina brick and Magnesia Spinel brick using in cement kiln should last up to one shutdown plan at least. However, somepart of refractory lining at critical area such as outlet and main burner pipe faced short service life and they needed to reline prior thetargeted planned shutdown. The records showed that the relining time of this minor shut down was about 5 days in average of production

loss. Most refractory materials using at outlet and main burner are refractory castable (monolithic) which requires careful setting, curingand preheating process. So that critical path of minor relining time is the castable works at the outlet of cement kiln. In order to improve

service life of the castable at outlet and burner, Siam Refractory set up a P-team (Product team) which included teammates from Productdevelopment, Quality assurance, Production and Marketing department observing problem and finding solution. By this, observation ofP-team at customers sites was set up in order to see the fact beginning from installation, heating, operation, demolition to disposal.

Details of each step were noted and distinguished customers needs. The interviews with related persons in the route were done such as

masons, contractors, operators, supervisors, engineers and managers. Questionnaires were also prepared and send to customers forchecking and prioritizing their needs. Reverse engineering for failed samples were deeply investigated as well as bench marking of otherproducts was tested and compared. In doing so, the closed relationship and good communication with customers were simultaneously

developed.The observation of P-team found that the major and frequent problems occurring in the outlet zone and burner pipe of cement

rotary kilns were thermo-chemical and mechanical wears. The loads generally acted on the refractory lining coming from abrasion of

clinker ball, abrasion and chemical reaction of clinker dust, and strong thermal cycling of secondary air from cooler as showed in figure

1. However, improper installation and installation techniques also affected short service life of them. These fact finding factors need to beresolved by new development of refractory castable.


2/5


Quality function Deployment (QFD)The needs and fact finding were reviewed, grouped and prepared in matrix table. Quality characteristics of product were

related, weighed and considered. Deployment of customers needs and quality characteristics was developed following QFD stages and

QFD tables were prepared as shown.

Table 1: The QFD table

Development stageFrom above table 1, quality characteristics of products were related with quality of raw materials and processes. Development

plan was set up. Materials and equipments were also prepared for the development.

Planni ng stageMost refractory castable are Alumina materials which are widely used by all refractory manufacturers such as Calcined Kaolin,

Calcined Bauxite, Tabular alumina, etc. In order to develop innovative product, selection of new raw materials was a key of development

because the new raw materials should have superior properties than ordinary Alumina materials. Properties of various kinds of raw

materials were studied comparing with the ordinary Alumina materials. Silicon carbide material was found that its properties could copewith the needs.

From the table 2, Silicon carbide material is inert, high hardness and low thermal expansion material which could generate

excellent properties of castable such as good abrasion resistance, good chemical resistance, excellent thermal shock resistance and highrefractoriness. This could be used in the critical conditions of outlet and burner pipe. However, its resistance to high oxidationatmosphere at high temperature is poor and its structure could be transformed from Silicon carbide to fluffy Silicon Dioxide which could

be quickly abraded. However, P-team though that this important property could not be compromised. In vice versa, if oxidation resistant

Main Problem

( 60% Al2O3 Low Cement Castable )

Thermal ShockThermal Shock

Burner Pipe

Nose Ring (Kiln Outlet)

Thermal, MechanicalAnd Chemical Spalling

Thermal, MechanicalAnd Chemical Spalling

Thermal&MechanicalSpalling

AbrasionAbrasion

Alkali AttackAlkali Attack

Thermal spalling caused by cold

air from cooler at the boundary

Abrasion of cement clinker

Cracking by mechanical stress

Infiltration of alkali components

Figure 1: pictures of cement rotary kiln and failed outlet & main burner

Refractoriness

Hard

Inert

LowTE

Non-toxic

Binder

Sizedistribution

Flow-ability

Settingtime

Gaspermeability

Bulkdensity

Strengthafterinstallation

Strengthafterfiring

Refractoriness

Abrasiontest

Alkaliattacktest

Clinkerattacktest

Oxidationtest

Thermalshockresistanc

Thermalexpansion

Thermalconductivity

Reheattest

Demanded

Quality

weight

Needs + + + - - 0 0 + 0 0 0 + + + - - - - + - - -Installation

fast demoulding 4 2 3

long shelflife 4 3

good flowing 4 4 4 4

optimum setting 4 2 4 3

easy mixing 4 4 5

easy casting 4 4 4 7

no explosion 2 2 2 2 4 2 7

Low consumption 2 4 3

Long service life

Thermal shock resistance from clinker bed 4 2 4 2 2 9

Thermal shock resistance from air cooling 4 4 4 2 2 9

Thermal shock resistance from main burner 4 2 4 2 2 9

Thermal load resistance at about 1500 C 4 4 2 2 2 4 4

Thermal load resistance in high oxygen atm. 4 4 2 4 2 4 4

thermal expansion allowance 4 4 3

abrasion resistance from clinker 4 4 2 2 4 4 7

abrasion resistance from dust 4 4 2 2 4 4 7

resistance to alkali attack 4 4 3

resistance to clinker attack 2 4 2 4 4 4

resistance to dust attack 2 4 2 4 4 4

less sticking of snowman 2 4 2 3

Energy saving

Low kiln shell temperature 4 3

short preheating 2 2 2 4 2 9

short curing 4 2 4 4 9

Waste management

easy wrecking 4 3

recycle 4 4

non toxic 4 4

Strong Weak

Material Quality characteristics


3/5


4/5


Checking stageThe test results were verified and reviewed in QFD table again. Negative effects of using higher percentage of Silicon carbide

were also considered and discussed among P-team such as cost, price per performance, and thermal conductivity values. Higher amountof Silicon Carbide could generate higher heat loss due to its high thermal conductivity characteristic. If using 80% Silicon Carbideproduct is applied, kiln shell and anchor of cement kiln will be destroyed by heat load. So that medium amount of Silicon Carbideproduct (60% SiC) was considered.

Action stageFrom checked and discussed results, reproduced samples were done and tested again. Test results showed that new refractory

castable with 60% Silicon carbide and 10% additive C gave optimum test values which properly applied to outlet and burner of cementkiln. Samples of new anti-oxidant Silicon Carbide castable were tested and fired at temperature 1500 Degree Celsius for 5 hours in

oxidation atmosphere comparing with normal Silicon Carbide castable. The fired samples showed that forming of protective film could

be perfectly covered Silicon carbide material and oxidation reaction could be prevented as showed in figure 6. Hence, all excellentproperties of Silicon Carbide could be preserved by new mixes design. New Silicon Carbide containing castable was trialed and launchedto market.

Figure 6: Left; Oxidized general Silicon Carbide castable and Right; Anti-Oxidant Silicon Carbide castable

Customer trialsMarketing materials of new refractory castable were prepared and presented to a customer in order to make trial lot in the real

application. A cement plant in SCG group accepted the concept of development and works trial of new Silicon Carbide containingcastable was produced. New castable was installed at area of outlet and burner tip by 60% Silicon carbide containing castable namely

TufDura S600. It could show outstanding performance after running 1 shut down as showed in figure 7 and 8. This was much

improvement and could satisfy the customer.

Commercial stageAfter finished the first trial, this new castable namely TufDura S600 was launched to world-wide market. Performance of

these castable could satisfy customers due to their tough and durable properties. Siam Refractory sold this type of our products tomore

than 10 countries such as Malaysia, The Philippines, Vietnam, India, Pakistan, Nigeria, Indonesia and Australia, etc.

ConclusionChanging raw material based from Alumina materials to Silicon carbide material could produce higher performance refractory

castable which has excellent thermal shock, chemical and abrasion resistance. Added additive C with certain content could protectSilicon Carbide from oxidation reaction and preserve excellent characteristics of the same. This type of new refractory castable couldsatisfy, resolve problem and fulfill customers needs. The most important step of development is how to find out what customers need

and how developed products or services can satisfy or delight them. These need good vehicles, tools and techniques of TQM such as

QFD, DOE, and other statistical models could help to be easier and faster development. This also was pushed by policy deployment oftop management as well as daily management of teammates. An example of this development of new silicon carbide containingrefractory castable could satisfy the customer trough TQM steps.

TufDura S 600: At one of SRICs customers in Thailand

Normal service life of Low Cement Castable: 3-4 months (90-120 days)Solution: TufDura S600 : service life after 200 days

Trial of refractory profile at burner pipeTrial of refractory profile at burner pipe

TufDura CastableTufDura Castable


Low Cement High Alumina Castable

Bottom Part of Burner pipe

TufDura S 600

TufDura S 600

Low Cement Castable

Burner tip

TufDura S 600Low Cement Castable

Burner tip

TufDura S 600

TufDura S 600

Performance ofPerformance of TufDuraTufDura SS 600600

atat one ofone of SRICSRICss customers incustomers in

ThailandThailand (after 219 days)(after 219 days)

LCC, 60% Al2O

3LCC, 60% Al

2O

3

Feature of TufDuraCastable:

Excellent abrasion and thermal

shock resistance

TufDuraS 600Abrasion loss4.0 cc.

LCC,60%Al2O3Abrasion loss8.0 cc.



TufDuraS 600TufDuraS 600

TufDuraS 600TufDuraS 600

Abrasion Resistance Evaluation

Media : Silicon Carbide size -20+50 mesh, 1 kg.Condition : Air Pressure 65 psi

Sample : After firing at 1400 oC

Figure 7: outstanding result at burner pipe Figure 8: outstanding result at outlet


5/5

SIC Refractory Castable

Documents

Transcript of SIC Refractory Castable