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Calcium Silicate

An Effective and Beneficial Thermal Insulation

by
Ms. Rupa Z. Vadodaria, Ketan A. Shah and H. V. Shah
Megha Insulations Pvt. Ltd., Bhavnagar, INDIA

Summary 

Thermal Insulation slows down the rate of heat flow and minimizes losses.  In face of increasing energy costs, industries have to improve efficiency and profitability to survive the pressures of globalization. Calcium Silicate insulation cuts energy costs and helps in achieving this goal faster.1 

Introduction

The need for efficient thermal insulation has increased with increased energy cost. An ideal thermal insulation has low mass, high strength and low thermal conductivity coupled with high service temperature. It reduces heat loss and thereby saves energy significantly and serves several functions such as:

  • Better control of temperature

  • Reduction of startup heating load (in batch processes)

  • Increase in production

  • Fire protection

  • Better working conditions

  • Reduction in thermal spalling in refractory lining, etc.


Rupa Z. Vadodaria is a Chemical Engineer and currently studying for Masters in Engineering Management at Drexel University, Philadelphia, USA.

Ketan A. Shah is a Civil Engineer and currently studying forMBA at Kellogg School of Management, 
Evanston, IL, USA.

H. V. Shah is a Chairman of Megha Insulations Pvt. Ltd.,A-11/6th floor, Dadasaheb Flats Kalanala, Bhavnagar-364 001, INDIA (Phone: +91-98252-07723)

Conventional insulation like Vermiculite and Mica bricks with a bulk density about 1000 kg/m3 have high strength but poor insulating characteristics. Flexible Insulation such as Mineral Wool and Ceramic Wool, has low mass 
and thermal conductivity (equivalent to Calcium Silicate) but no inherent strength and is compressible. 2,3 

Calcium Silicate insulation is a unique and versatile insulation offering the thermal efficiency of flexible insulation and the strength of Conventional Insulation Bricks up to 1000 C temperature. It has a long life and once 
installed requires hardly any maintenance. As a thumb rule, wherever refractory bricks are being used, CSI may be used as a backup layer. Table 1 shows product properties vs. relevant IS and ASTM standards.4

Cost Performance Data For Various Process TemperaturesWe have calculated heat losses and surface temperature data at various process temperatures using NAIMA, U.S.A.s 3E plus program5. The details are:

Assumptions

Process temperatures, C       :   1000, 800, 600 and 400 C
Area                                   :   Vertical flat
Ambient temperature             :   32 C
Wind velocity                       :   0 Kmph
Outside surface emittance      :   0.9 (All service jacket)

Conversion Factor

1 Btu/sq.ft./hr.  =   0.252 Kcal/sq.ft./hr.

                      =   0.252 x 10.764 x 8040 Kcal/Sq.m. for 8040 hrs
                           (335 working days)

                      =   0.0218 Mil. KCal/Sq.m. for 8040 hours

    Current Price:

        Cost of heat energy        Case to case basis
Cost of Calcium Silicate insulation  : Rs. 650/- for 50 mm. thickness/ m2
Cost of Calcium Silicate insulation  : Rs. 1248/- for 100 mm. thickness/ m2
Cost of Calcium Silicate insulation  : Rs. 1755/- for 150 mm. thickness/ m2
Cost of Calcium Silicate insulation  : Rs. 2236/- for 200 mm. thickness/ m2

The system of mathematical heat flux and thermal performance equations used in this analysis has been accepted by A.S.T.M., U.S.A. and calculated using NAIMA, U.S.A.s 3E plus program. Information is based on laboratory condition and as applicable for normal systems. Actual values may vary depending on the service 
conditions 5. 

Table 2 and Graphs 1 & 2 shows outside surface temperature, heat loss and costeconomics for CSI at various process temperatures. It shows that higher the thickness of CSI; the lower is the heat loss and greater the savings in energy. Even using 100 mm. thickness of CSI is beneficial for process temperature 400 C where at surface temperature 55 C value of heat lost (based on use of steam coal) is more as compared to cost of insulation.

Conventional Insulation Brick vs. Calcium Silicate Insulation

A cement plant using 114 mm. Refractory Brick + 100 mm. Conventional Insulation Brick has replaced Conventional Insulation Brick with Calcium Silicate insulation. Table 3 shows surface temperature and heat loss data for gas 
temperatures of 950 C and 850 C.

Results show that Calcium Silicate insulation saves energy significant & pay-back period is less than 2 months, higher thickness is recommended.

Sandwich Insulation : Ceramic Fibre + CSI up to 1400 C

For higher temperature up to 1400 C, Ceramic Fibre backed by CSI will provide high benefit cost ratio to the user in comparison with any other insulation product. 
Table 4 shows surface temperature, heat loss and cost performance data for Ceramic Fibre and CSI at various process temperatures.

Use of hollow refractory box or hollow CSI box in required shape and size containing Calcium Silicate insulation in Powder form will be most cost beneficial.

General

M/s. Saurashtra Cement Ltd., Ranavav, Gujarat state, has insulated their plant equipment using our Calcium Silicate insulation Materials. They have reported savingof fuel and electrical energy value Rs. 11 crores per annum (1998-99). M/s. SCL have been presented the National Award for best improvements in thermal energy 
performance for the year 1998-99 at the 7th NCB international seminar on Cement and Building Materials held on 21.11.2000 at Delhi6.

M/s. IDBI and M/s. USAID have carried out energy surveys in cement plants thru M/s. Holtec Engineers, Cement Consultants, New Delhi, INDIA and M/s. Resource Management Association, Wisconsin, U.S.A. (1995). Their report confirms that thermal energy and electric power consumption savings of 15 % is available to the Indian Cement sector. Therefore, investing in energy efficiency can be as profitable as investing in increased 
production capacity7.

A cement plant manufacturing 1 million tons of cement consumes about 1.80 lac tons of steam coal per year. By using CSI - about 265 tons value Rs. 1.2 crore - it is possible to save 27,000 tons of steam coal value about 
Rs. 7 crores per year.

M/s. HINDALCO has started using CSI in their electrolytic cells reducing electrical energy consumption from 18000 unit to less than 14000 unit saving 4000 unit (KWH) (estimated value Rs. 15000) per ton of aluminium metal produced.

M/s. Bokaro Steel Plant, M/s. B.H.E.L., M/s. Saint Gobain Glass (India) Ltd., Steel Rolling Mills & Others have also benefited considerably.

Significant fuel savings can be obtained in various industries including power plants, petrochemicals, refineries, fertilizers, ceramics, etc. who use thermal equipments.

Environmental and Economic Thickness of Insulation

CSI decreases fuel consumption and thereby reduces emission of carbon dioxide, oxide ofnitrogen etc. minimizing environmental impacts. Carbon reduction input & economic thickness of insulation can be calculated for individual cases based on:

  • Size and material of construction of thermal equipment (In general, thicker the material, higher the heat storage and startup loads and lower the heat loss)
  • Working temperature / peak temperatures (Higher temperatures lead to higherlosses due to larger temperature gradients)
  • Quality, thickness and thermal properties of refractory material being used (Heat loss will vary depending upon insulating properties, thickness, porosity and density of materials used)
  • Wind speed and ambient temperature around the equipment (higher the wind speed and lower the ambient temperatures, more will be the heat loss.)
  • Working hours per year, Batch operation versus continuous operation.
  • Calorific value and cost of fuel (Higher the cost of the fuel, more benefits can be derived using even smaller thickness of insulation), etc.

Conclusion

With rapidly increasing energy costs combined with competitive globalization, all Industries have to face the challenge of improving the quality and winning the price wars to create or sustain profits for future growth. Continuous energy conservation program based on collection & analysis of data and implementation of energy savingmeasures will help in achieving this goal faster.
(Note: We will be glad to help you cut your energy cost. Please send us details of your thermal equipment to enable us to suggest how CSI can effectively help you conserve expensive thermal (heat) energy).


References

  • Catalog of Megha Insulations Pvt. Ltd. and website: www.meghainsulation.com 
    (Phone: 0091-278-411523/526/728), INDIA.

  • Ketan A. Shah, Role of Insulation in Thermal Energy Conservation, at a seminar on Energy Management The New Imperative organized by the Confederation of 
    Indian Industry (CII) at Ahmedabad (1997).

  • Rupa Z. Vadodaria, Industrial Insulators, Project Report, L.D. Engg. College, Ahmedabad (1997)

  • BIS, INDIA, Standard IS 9428 & ASTM, USA, Vol. 6, Standard C533-90

  • NAIMA (North American Insulation Manufacturers Association), USAs 3E plusprogramme

  • Cement. Vol. XXXIV, No. 2, Page 33

  • Resource Management Associates of Madison, Inc., USA., circular: Indias Cement Industry offers Concrete opportunities for Energy Savings and increased profits 1995. (Phone:001-608-283-2880)

Table 1 : Product Properties vs. Relevant Standards

"SONASIL" - Calcium Silicate Insulation (CSI)

SONASIL is available in the form of Blocks, Pipe sections, Segments and Powder 

Properties

IS 9428

ASTM C 533:90

SONASIL Grade:

Type I

Type II

800

1000

 Temperature (C), max.

950

649

871

800

1000

  Bulk Density (kg/m3)

   

(max.)

(max.)

8-11

8-11

      Test Values:

200-320

240

240

220-270

230-275

      Avg. value:

220-280

                               
Compressive strength, Length/Width:

 
kN/m2 :
                                      
   
 Dry, under a load
of  
415 kN/m2 :

5 %

5 %

5 %

3%

3%

  Wet, under a load
 of 170  kN/m2, after 18 hrs. of 

 immersion in water

 

5 %

-

-

3.5 % 3.5 %
Dry, under a load of 345 kN/m2, after 24 hrs. heat soak :

5 %

-

-

3.5 % 3.5 %

  Flexural Strength 
  (kN/m2),min.

240 310 310 400 400

  Heat Resistance after heat 
  soak at max. temp. for 24
 hrs.

             
Linear shrinkage (length),               

  max. :  

2% 2% 2.5% 2% 2%

  typical :

- - - 1.6% 1.8%

  Loss in mass, max. 

1.5% - - 15% 15%

  Thermal Conductivity 
  (W/mk),
  max. at mean temp.

             

    200 C

0.080 0.079 0.095

0.070

0.080

    300 C

0.097 0.095 0.110 0.080 0.090

    400 C

0.121 - 0.136 - 0.105

    500 C

0.148 - - - 0.120

  Cold Crushing Strength  
   (CCS), (N/mm2), min.

- - - 1.4 1.5


  * ASTM thermal conductivity values correspond to mean temperatures of 
   204, 316 and 427 C. 

  December,2001 
                                                                                                                                
Table 1 : Product Properties vs. Relevant Standards (contd.) 

"SONASIL" - Calcium Silicate Insulation Materials (CSI)

SONASIL is available in the form of Blocks, Pipe sections, Segments and Powder

Properties

IS 9428

ASTM C 533:90

SONASIL Grade:

Type I

Type II

800

1000

 Moisture Content(%),  
  max.

7.5

-

-

7.5

7.5

 Alkalinity, pH

8-11

-

-

8-11

8-11

  Dimensional
  Tolerance (mm.):
                          
     Length/Width:
         kN/m2 :

3

3.2

3.2

2

2

     Thickness:
  

-1.5,+3

3.2

3.2

-1.5,+2 -1.5,+2
     Pipe inside
     diameter:

-0,+5

-

-

-0,+5 -0,+5

Chemical Properties: SONASIL is resistant to reduction gases, e.g. moist air, organic solvent vapors, protective gases (N2, inert gases), reducing atmospheres (H2, CO, CH4, NH3) etc.

Note: Tests are performed to relevant standards. Values given in catalog are typical values obtained from lab specimens under standard test conditions and are not for use as maxima or minima in specifications.

  Conversion to conventional units

  1    Kcal/m. hr C    
        hr.C              

                           

=


=

   6.933  Btu.in/ft2


   1.163  W/mK  
  1    Kg/m3             

=

   0.06243  Lb/ft3
  1    KN/m2             

=

   0.145  Lb/in2

 IS 9428 refers to relevant Indian Standard
 ASTM C 533: 90 refers to relevant American Standard of Testing and 
 Materials, U.S.A.

 December, 2001

Table 2 : Heat Loss, Surface Temp. and Cost Data for CSI at

  Process Temp. 1000 C

CSI Thickness mm.

CSI, Outside Surface Temp.C

    

CSI, Outside Surface Heat Loss

Btu/hr. per sq.ft.

Mil. Kcalper M per 8040 hrs.

50 151 304

602

13.12

100 105 221 309 6.74
150 86 186 208 4.53
200 76 157 157 3.42

  Process Temp. 800 C

50 123 254 417 9.09
100 87 189 215 4.69
150 72 162 145 3.16
200 64 147 109 2.38

  Process Temp. 600 C

50 97 206 264 5.76
100 70 158 136 2.96
150 59 139 92 2.01

  Process Temp. 400 C

50 72 161 143 3.12
100 55 131 74 1.61

 


Table 3 : Heat Loss & Surface Temperature data for
                Refractory + Insulation Brick versus Refractory + Calcium Silicate
                Insulation

  At gas temperature : 950 C

Refractory mm.

Insulation Brick mm.

Calcium Silicate Insulation, mm.

Outside SurfaceTemperature

Outside Surface Heat Loss

F

C

Btu/hr.
per sq.ft.

Mil. KCal/M
per 8040 hrs.

114 100 -- 337 169 741 16.15
114 -- 100 200 93 247 5.38
We suggest:
114 -- 150 173 78 174 3.79

  At gas temperature : 850 C

114 100 -- 317 158 657 14.23
114 -- 100 186 86 208 4.53
We suggest:
114 100 150 162 72 146 3.18

  Advantages of using Calcium Silicate Insulation (CSI) vs. Insulation Brick (CIB):

  • Decrease in surface temperature

  • Saving substantial additional thermal energy.

Table 4 : Surface temperature, Heat loss & Cost performance data for
              
  Sandwich Insulation: Ceramic Fibre + Calcium Silicate Insulation


Process
Temp.C
at


Ceramic Fibre Thick,
inch. 


Calcium 
Silicate


Interface Temp.C


Outside 
Surface
Temp. C

Outside Surface Heat Loss

Cost per Sq.Ft. of


HTZ 
128 kg./M

Thick inch
 Board

Btu/hr.
per
sq.ft.

Mil.
KCal/M
per8040 hrs.

% age
Addi-
tional
saving

Ceramic
fibre
Rs. per
Sq.Ft.

CSI 
Rs. per
Sq.Ft.

Total
cost
Rs. per
Sq.Ft.

1400 12 0 -- 76 162 3.53 -- 493 0 493
    6 6 826 74 152 3.31 6.17 267 151 418
    12 0 -- 72 145 3.16 -- 493 0 493
1250    6 6 763 70 134 2.92 7.59 267 151 418
        4 8 917 70 134 2.92 7.59 191 186 377
1100 HTZ 
96 kg./M
Powder                        
12 0 -- 68 126 2.75 -- 360 0 360
    6 6 692 65 115 2.51 8.73 200 110 210
    4 8 827 65 115 2.51 8.73 147 147 294
950 RZ
96 kg./M
Powder                                          
12 0 -- 63 105 2.29 -- 300 0 300
    0 12 -- 60 94 2.07 11.70 0 240 240

 

Copyright 2001 Megha Insulations Pvt. Ltd.. All rights reserved.
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