Energy Conservation Opportunities in an Industrial Boiler System

Transcription

1 CASE STUDIES Energy Conservation Opportunities in an Industrial Boiler System Durmus Kaya 1 and Muharrem Eyidogan 2 Downloaded from ascelibrary.org by Technische Universiteit Delft on 09/13/17. Copyright ASCE. For personal use only; all rights reserved. Abstract: In this study, an experimental study has been performed for a natural gas fueled boiler operating at 42,000-kPa pressure and K temperature with a nominal capacity of kg/s to find improvement in the boiler efficiency., pressure, velocity, and gas emissions measurements have been made and energy, mass balances, and exergy analysis have been formed. Then, efficiency of boiler, potential energy saving options and saving quantities, investment costs, and payback period for normal operating conditions have been calculated. From the measured data, the boiler and exergetic efficiency were calculated as and 36.7%, respectively. It is seen that the main efficiency losses are leakage of air in the rotary type air heaters, operation of the boiler at high excess air/fuel ratios, operation of the boiler under the rated load, surface thermal losses, and high flue gas temperatures. The largest part of the boiler efficiency losses is due to the air leakage in the rotary type air heater. Due to air leakages, the load of the induced-draft fan increases and prevents the boiler to reach its normal boiler capacity. It has been calculated that if air leakage in rotary type air heater is reduced to acceptable limits 10% in practice, boiler steam production capacity will be increased by 34.2% from to 32.8 kg/s. Implementation cost is required only for reducing air leakages in the rotary type air heater and surface thermal losses. The investment cost for reducing air leakage in the rotary type air heater to the acceptable limits 10% is between $600,000 and $700,000. Under these circumstances, the payback period of this investment cost is about 15 months. DOI: / ASCE :1 18 CE Database subject headings: Energy; Conservation; Experimentation; Natural gas. Author keywords: Steam boiler; Energy efficiency; Energy savings; Exergy analysis. Introduction Boilers are generally defined as closed containers operated under high pressures to convert the chemical energy of the fuel to thermal energy. For the selection of the boiler: operation purpose, manufactured steam amount, pressure and temperature, the inlet temperature of feed water, water hardness, fuel type, lower heating value of fuel, fuel analysis, and fuel cost must be evaluated Onat et al The efficiency of a boiler is a measure of its ability to generate the steam demand from a given fuel supply Kilicaslan and Ozdemir The main factors affecting the boiler efficiency are incomplete combustion, excess air, thermal loss due to water vapor in flue gas, flue gas temperature, fuel type, burners, boiler load, thermal loss from boiler surface, and dirtiness of the heater surface Kaya et al TUBITAK-MRC, Energy Systems and Environmental Research Institute, P.O. Box 21, Gebze-Kocaeli, Turkey corresponding author. Durmus.Kaya@mam.gov.tr 2 Dept. of Mechanical Education, Kocaeli Univ., Kocaeli, Turkey. muharrem_eyidogan@hotmail.com Note. This manuscript was submitted on April 11, 2008; approved on August 10, 2009; published online on February 12, Discussion period open until August 1, 2010; separate discussions must be submitted for individual papers. This paper is part of the Journal of Energy Engineering, Vol. 136, No. 1, March 1, ASCE, ISSN / 2010/ /$ Boiler Efficiency and s Affecting Efficiency There are two ways to calculate the thermal efficiency of boilers. These are direct or indirect methods. In direct thermal efficiency calculation, feed water and steam amount, feed water and intermediate temperature and pressure, feed fuel amount, and fuel low heating value must be measured. By these measured values, the efficiency is calculated by the following equation: = ṁ si s ṁ w i w BH u where ṁ s =steam flow rate kg/s ; ṁ w =water flow rate kg/s ; i s =steam enthalpy kj/kg ; i w =feed water enthalpy kj/kg ; B =fuel flow rate kg /s ; and H u =fuel lower heating value kj/kg. In indirect thermal efficiency calculation :1 Z Z refers to the ratio of different thermal losses. In this method, flue gas analysis temperature, velocity, pressure, dust measurements, and gas analysis, air flow rate and temperature, boiler surface temperature, and blow-down quantity are measured. Fuel elemental analysis is done and the lower heating value of the fuel is determined. According to these measurement results, specific air quantity and specific flue gas quantities are first determined. Then, theoretical specific air quantity, theoretical specific smoke quantity, excess air coefficient, actual specific air and smoke quantities, flue gas heat loss ratio, incomplete combustion loss ratio soot / JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010

2 Table 1. Technical Specification of Boiler Boiler heat transfer surface m 2 2,085 Boiler volume ton 120 Superheater steam output pressure kpa 45,700 Superheater steam output temperature Boiler feed water inlet temperature Boiler manufacturer Babcock Wilcox loss is found from the dust emissions, unburned fuel loss ratio, and blow-down loss ratio are determined, and finally, thermal efficiency is calculated. This study has been carried out due to the request of the industrial organization. The main aim of this study is to investigate the reasons of efficiency drop for the boiler, which cannot reach the full load, to give recommendations for compensation, and to determine the amounts of thermal losses, the investment cost, and payback period Kaya and Eyidogan Measurement Methods and Devices The boiler system consists of boiler, rotary type air RTA heater, burners, induced-draft ID and forced-draft FD fans, and chimney. The technical specification of the boiler is given in Table 1. A schematic view of the boiler system and its measurement system are given in Fig. 1. To constitute energy and mass balances between the inlet and the outlet of the boiler and between the inlet and outlet of the rotary type air heater, flow rates, pressure, and temperature measurements were done and present countermeasures on the system were read. The flow rate of natural gas was read from the T = K Nm3/s Flue gas T = K Nm3/s Fresh air RTA Heater T = K Nm3/s Flue gas counter and then the chemical composition of combustion products and flow rates were calculated. The accuracy of these calculations was checked with the combustion gas flow and gas analysis measurement at the exit of the boiler and chimney. Approximately the same value was obtained discrepancy is less than 1%. For determination of steam flow rate used in the system, PANMETRICS brand transit time ultrasonic flowmeter was used measurement accuracy 0.5%. measured by this instrument was checked with the steam flowmeter in the boiler and the proximity between these values was seen. Air flow rate at the inlet of the boiler was measured by a TESTO 445 brand flowmeter. Flue gas and boiler exit gas measurements were done by TESTO 360 and TESTO 350 brand gas analysis instruments based on electrochemical detection method. TESTO 445 brand instrument was used for flue gas velocity and pressure and then flue gas flow rates were calculated. Then, boiler combustion gas flow rate was calculated by using O 2 at boiler exit. By subtracting the boiler combustion gas flow rate from the flue gas flow rate, the amount of air leakage was calculated. Excess leakage flow rate was found by subtracting leakage air from 10% of the burning air. Evaluation of the Measurements and Calculations For normal operating conditions, boiler efficiency was calculated by using natural gas and steam flow rates and inlet enthalpies of vapor and water. The results are given in Table 2. Natural gas flow rates, oxygen ratio of the boiler combustion gas, and combustion gas temperature are given in Table 3. Combustion gas analysis was done by fuel amount, boiler combustion gas oxygen percentage, and elemental analysis of the fuel. The results are given in Table 4. By using the components in Table 4, total stochiometric com- Steam m = kg/s Boiler Water T = K m = kg/s Natural gas T = K 2.22 Nm3/s ID FAN FD FAN Leakage air Nm3/s Combustion air T = K 31.2 Nm3/s Fig. 1. Schematic view of the boiler system and its measurement system JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010 / 19

3 Table 2. Boiler Efficiency Calculation at Normal Operating Conditions Steam flow rate ṁ s kg/s Steam enthalpy i s kj/kg 3, Water inlet enthalpy i w kj/kg Enthalpy difference i s i w kj/kg 2, Heat given to water W =ṁ s i s i w 69, Natural gas flow rate m 2.22 The lower heating value of natural gas kj/n m 3 35, Total heat of fuel F =ṁ Hu 78, Efficiency W / F bustion gas, theoretical combustion air, excess air, theoretical total combustion air, boiler outlet gas flow rates, and excess air ratio were calculated Table 5. By using measured and calculated values, energy equations were formed for the boiler, the RTA heater, and the whole system. The results are given in Tables 6 8. Potential Energy Saving Options Reduction of Excess Air Leakage Losses One of the most important potential energy saving options in the boiler system is the air leakage losses in the RTA heaters. In practical life, it is impossible to completely avoid air leakage in RTA heaters Stultz and Kitto In these types of heaters, air leakage increases as time passes because of the corrosion due to the combustion gases. Then, the total boiler efficiency decreases as a result of increased air leakages. Expected air leakage value in the design of this boiler is 7% of the burning air. From our energy audit experience, the maximum acceptable level for air leakage is 10% of the flow rate of the air burning in the blower. The amount of air leakage can be determined easily by the measurements of O 2 at the outlet of the boiler and the outlet of Table 3. Natural Gas Flow Rates, Ratio of the Boiler Combustion Gas, and Outlet Gas Natural gas flow rate 2.22 ratio of the boiler combustion gas 5.40 Boiler outlet gas temperature Table 4. Elemental Analysis of the Natural Gas, Its Combustion Products Analysis, and Flow Rates Fuel Combustion products N m 3 /h Table 5. Boiler Combustion Gas Total Flow Rate, Theoretical Combustion Air, Excess Air Flow Rate, and Ratio for the Normal Operating Conditions name uantity Total stoc. combustion gas ob a Theoretical combustion air ob a Excess air a 8.79 Theoretical total combustion air a Boiler outlet gas flow rate ob a Excess air ratio a Measurement accuracy= 0.1%. flue gas. In the measurements, combustion gas oxygen value is found as 5.40%; however in the flue gas measurements this value was found as 10.0%. By using excess leakage air flow, specific heat of the gas, flue gas and ambient temperatures, energy loss, and potential energy savings were calculated and the results are shown in Table 9. By decreasing air leakages, electric consumption of flue gas emission fan will decrease. However, the ratio of this saving potential is low, so no extra calculation is given here. Reduction of Excess Air/Fuel Ratio A boiler should always be supplied with more combustion air than theoretically required to ensure high efficiency and safe operation. At the same time, boiler efficiency is very dependent on the excess air rate. Therefore, the excess air rate should be optimized to increase the system efficiency Kilicaslan and Ozdemir Excess air should be kept at the lowest practical level to reduce the quantity of unneeded air West In the measurements of the boiler, it was found that the boiler operates over the optimum excess air/fuel ratio 10% for natural gas. Reducing excess air to that needed for complete combustion will improve boiler efficiency. Most boilers operate best when the stack gas has excess air or oxygen levels similar to those shown in Table 10. Excess air levels will be different for different firing rates and for different boilers. For natural-gas boilers, high-firing rates may require less than 2% excess oxygen 10% excess air, while lowfiring rates may require more than 6% excess oxygen to ensure complete combustion. When air is delivered for combustion, the nitrogen absorbs heat and is carried up the stack, resulting in energy losses. If there is excess air, the result is unused oxygen as Fuel analysis % ob Stoc. O 2 CO 2 SO 2 N 2 Argon H 2 O O 2 CO Methane , , , , Ethane Propane Butane Pentane , Nitrogen Carbon dioxide Total 100 2, , , Excess air , Gas components % original base Accuracy of measurement instruments 0.3% 5% 5% 0.2% 5% 20 / JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010

4 Table 6. Mass and Energy Balance for the Boiler Inlet Lower heating value kj/kg total Natural gas , , c s 0 Burning air , Water a , Total 99, Downloaded from ascelibrary.org by Technische Universiteit Delft on 09/13/17. Copyright ASCE. For personal use only; all rights reserved. Outlet Enthalpy kj/kg total Steam a 3, , Combustion gas , Losses surface heat, humidity in the air, etc. 5, Total 99, a c=combustion heat; s=sensible heat: kg/s. Table 7. Mass and Energy Balance for the Rotary Type Air Heater Inlet Combustion gas , Burning air , Leakage air Total 17, Outlet total total Flue gas , Burning air , Losses surface heat losses Total 17, Table 8. Mass and Energy Balance for the Whole System Inlet Lower heating value Hu kj/kg Natural gas , , c s 0.1 Burning air , Water 24.44* , Leakage air Total 80,758, total Outlet Enthalpy kj/kg total Boiler flue gas , Leakage flue gas , Steam 24.44* 3, , Losses surface heat, humidity in the air, etc. 5, Total 93, Note: * denotes kg/h. JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010 / 21

5 Table 9. Energy Savings by Avoiding Excess Air Leakage Losses Leakage air gas flow rate Burning air flow rate Acceptable leakage flow rate 3.12 Excess leakage air flow rate Flue gas temperature Ambient temperature Energy saving 1, Annual energy saving MJ 40,290,500 well as even more nitrogen to absorb heat that is carried up the stack. The potential energy savings by reducing the excess air/fuel ratio to the optimum value is given in Table 11. Operating the Boiler at Full Load Average steam production is found to be kg/s in the measurements at the normal operating conditions. Rated load for this boiler is kg/s. When the boiler is operated at the design load, approximately 2% efficiency increase is expected. The amounts of energy savings are given in Table 12. Reduction of Flue Gas Under operation conditions, flue gas temperature was measured as K. Flue gas temperature can be decreased to K by Table 10. Variation of Optimum Excess Air and O 2 According to Fuel Type Fuel type Optimum excess air Optimum excess O 2 Natural gas Propane Table 11. Potential Energy Savings by Reducing Excess Air Excess air flow rate 8.79 Excess air ratio 39 Target excess air ratio Reduction in air 6.54 Air inlet temperature Flue gas temperature Energy saving potential Annual energy saving kj 23,042,556,906 Table 12. Amount of Energy Savings by Operating the Boiler at Full Load Energy given to the boiler 78, Target increase 2 Energy saving potential 1, Annual energy savings kj 47,305,908, / JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010 Table 13. Amount of Energy Savings by Reducing the Flue Gas Flue gas flow rate Flue gas temperature Target flue gas temperature Energy saving potential Annual energy savings kj 18,750,061,860 applying the suggestions given in the Introduction. By this way, an important amount of energy can be saved by decreasing flue gas temperature. Saving potential was calculated by using flue gas flow rate, specific gas heat, and flue gas temperature and circumstance temperature, and results are given in Table 13. Decreasing Boiler Surface Losses The boiler surface was scanned by thermal camera to determine surface losses and weak isolated areas. When these weak isolated areas are reinforced energy saving at a ratio is possible. Since the ratio of this saving potential is low, no extra calculation is given here. Total Energy Saving Potential By considering all the energy saving potentials, energy is given in terms of fuel equivalence to natural gas and the financial values of this are shown in Table 14. Investment Costs and Payback Periods In the above energy saving options, only avoiding excess leakage air is required for investment cost. Among the other saving areas, decreasing the excess air and operating boiler at full load do not require any investment. These two options require boiler care and operation rules such as regular cleaning of boiler tubes and operating the boiler at optimum air-fuel ratio. Therefore, the payback period was calculated for only the first option: excess air leakage. For this option, one of two methods is suggested. Table 14. Total Energy Savings Potential Type of energy saving Avoiding excess leakage air losses Reduction of excess air Operating the boiler at full load Reduction of flue gas temperature Energy Energy saving potential Natural gas Liq. m 3 /h Annual financial value $ 1, , ,750 1, , ,138 Total 4, ,729 Note: Cost of 1-m 3 liquefied natural gas is taken as $0.19 and its calorific value is taken as 34,541 kj.

6 Table 15. Potential Energy Savings by Changing the Current Rotary Type Air Heater with a Static Recuperative Heat Exchanger Leakage air gas flow rate Ambient temperature Flue gas temperature Energy saving 1, Annual energy saving kj 51,925,693,407 Annual financial saving $ 285,627 Table 16. Expected Efficiency after Potential Energy Savings Energy saving t 4, Energy will be given to water after energy saving 73, H + t Fuel heat F 78, Efficiency H + t / F 93.7 Table 17. s That Will Increase Steam Production by Excess Air Leakage Prevention Leakage air flow rate Steam flow kg/s Boiler efficiency Natural gas flow 2.22 Natural gas lower heating value kj/kg 35,227 Combustion product flow/natural gas flow ṁ ky /ṁ k Steam enthalpy kj/kg 3,299.2 Water inlet enthalpy kj/kg Enthalpy differentiate kj/kg 2,824.7 Table 18. Possible Increase in Steam Production via Decreasing the Excess Air Leakage Prevented excess leakage air ratio Prevented excess leakage air flow rate Additional natural gas flow for capacity increases Modernization of the Present Rotating Air Heaters Air leakage of N m 3 /s at the RTA heaters can be reduced to 3.12 N m 3 /s, the acceptable limit of 10% of combustion air. To reach this value, the present system must be modernized. The manufacturer has offered $600,000 for modernization of the present rotating air heaters. Energy loss can be prevented by decreasing the excess air leakage and the ID fan load will be reduced to 25%. Therefore, by increasing the boiler production capacity, boilers can be operated at nominal loads. The effect of decreasing air leakage on the steam production increase will be given later. Consequently, the total saving potential is the sum of savings due to the prevention of excess air leakage and the operation of boiler at full load for this option. This is $221,625+ $260,215 = $ 481, 840. The payback period is 600, 000/ 481, 840 =1.245 years 15 months. Changing the Current Rotary Type Air Heaters with a Static Recuperative Heat Exchanger When RTA heaters are used for a long time, leak-proofness systems corrupt due to corrosion and erosion. Therefore, some corporations have changed the RTA heaters with static recuperative heat exchangers. In these types of heaters, corrosion problems have been overcome owing to the construction materials used. Besides, as all leakage loss was prevented, the saving ratio increased Table 15. For this situation, the amount of total saving is $285, $260,215= $545,842. From the market survey, it is concluded that change of rotating air heaters with static recuperative heat exchangers requires investment costs of about $700,000. The payback period is 700, 000/ 545, 842= years, approximately 15 months. Although the second investment suggestion requires more capital, the return period is nearly the same with the first investment suggestion. Besides, the second suggestion provides $64,002/year extra saving. Expected Boiler System Efficiency Level after Potential Energy Saving As a result of the potential energy saving options mentioned above, the expected efficiency values are given in Table 16. As it can be seen from Table 16, when saving potentials are evaluated, the boiler efficiency will increase from to 93.7%. Additional natural gas energy Total combustion gas flow after capacity increase Capacity increase kg/s , , , , , , , , , , Increase ratio JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010 / 23

7 Effect of Excess Air Leakage Prevention to Increase of Steam Production s that will cause the increase of steam production by excess air leakage prevention are given in Table 17. Possible increase in steam production was calculated via decreasing the excess air leakage with data given above and the results are given in Table 18. As it can be seen above, when the excess air leakage is prevented, ID fan load decreases and the steam production capacity will increase by 8.36 kg/s. When all air leakage is prevented, the steam production capacity increase will be higher. Exergy Analysis Exergy is defined as the maximum amount of work which can be produced by a stream of matter, heat, or work as it comes to equilibrium with a reference environment Rosen and Dincer Exergy appears to be an effective measure of the potential of a substance to impact the environment Cengel et al The assumptions for simplifying calculations: Combustion air and exhaust gas were accepted ideal gas; Combustion air consists of 75.67% N 2, 20.35% O 2, 0.03% CO 2, and 3.03% H 2 O, molar basis; and Potential and kinetic energies of fuel, combustion air, and exhaust gas are ignored. The exergy of fuel and exhaust gas are equal according to the collection of chemical exergy and thermomechanical exergy e = e th + e ch The chemical exergy of gas fuel can be determined from Ghamarian 1981, e F ch = 1, H C C LHV where h and c=atomic ratio of hydrogen and carbon, respectively. The thermomechanical exergy of exhaust gas is evaluated from the following equation: n e th = a i h i T h i T 0 T 0 s 0 T s 0 T 0 R ln P i=1 P 0 where a i =molar amount of component i; s 0 =absolute entropy at standard pressure; and R =universal gas constant Sayin et al The chemical exergy of exhaust gas is evaluated from the following equation: n e ch = R T 0 i=1 a i ln y i y i s where y i s =molar ratio of ith component in the reference environment and y i =molar ratio of the ith component in the exhaust gas. and pressure in the reference environment are T K and P 0 1 atm, respectively Sayin et al The thermomechanical exergy of fuel, combustion air, and chemical exergy of combustion air are ignored since these values 24 / JOURNAL OF ENERGY ENGINEERING ASCE / MARCH Table 19. Exergy Analysis of Whole Systems Fuel chemical exergy kw Exergy losses in boiler kw are close to reference environment. Table 19 shows that exergy analysis of whole systems. Conclusions and Recommendations Energy efficiency measurements have been done in a boiler of an industrial facility. By using measurement and also existing accurate device reading values, mass, energy balances, and exergy analysis have been formed and potential energy saving have been assessed. Main energy losses are excessive air leakages at the RTA heater, operating boilers at high excess air coefficients, surface thermal losses, high flue gas temperatures, and operating the boiler under the rated load. The present boiler efficiency and the possible efficiency increase due to potential savings, saving potentials, required solution cost, and payback periods have been calculated. The findings for the boiler are summarized as follows: The most important part of the boiler efficiency loss is due to the excess air leakage at the RTA heater. Two different solutions were recommended to prevent this efficiency loss; The first solution choice is the modernization of the present rotating air heaters. The solution cost for modernization is $600,000. The payback period is 15 months; The second solution choice is replacing the current RTA heaters by static recuperative heat exchangers. The solution cost is $700,000 and the payback period is 15 months; The excessive air leakages at the RTA heater increase the load of the ID fans and prevent the boiler from reaching the rated load. When the excess air leakage is reduced to acceptable limits 10%, the boiler steam production capacity will increase from 34.2% to 32.8 kg/s. When all air leakage is prevented, the steam production capacity increase will be more; During boiler combustion gas measurements, CO value is read near zero. Therefore, no incomplete combustion phenomenon is encountered. However, it is determined that this boiler is operated at higher combustion air than the optimum case; and There is no need to make any solution for the boiler operating at optimum excess air coefficient and also at full load conditions. According to the calculation results, for the normal operating conditions the boiler efficiency, exergetic efficiency, and total potential energy savings are 88.28%, 36.25%, and 4, kj/s, respectively. Annually, the financial value of this energy equivalent to natural gas is $711,729, and as a result of energy savings, the boiler efficiency will be 93.7%. Acknowledgments Exergy losses due to exhaust gas kw Exergy losses in air heater kw Exergetic efficiency 81, , , % The writers are grateful to Dr. Bulent Imamoglu for editing the paper.

8 Notation The following symbols are used in this paper: a i molar amount of component i; B fuel flow rate kg h 1 ; e specific molar exergy kcal kmol 1 ; H u fuel lower heating value kj kg 1 ; i s steam enthalpy kj kg 1 ; i w feed water enthalpy kj kg 1 ; LHV lower heating value kcal kmol 1 ; ṁ s steam flow rate kg h 1 ; ṁ w water flow rate kg h 1 ; P 0 pressure in the reference environment; heat rate kg h 1 ; f total heat of fuel kg h 1 ; W heat given to water kg h 1 ; R universal gas constant kcal kmol 1 K 1 ; s 0 absolute entropy at standard pressure kcal kmol 1 K 1 ; T 0 temperature in the reference environment; y i molar ratio of the ith component in the exhaust gas; y s i molar ratio of ith component in the reference environment; Z refers to the ratio of different thermal losses; and boiler efficiency. References Cengel, Y. A., Wood, B., and Dincer, I Is bigger thermodynamically better? Int. J. Exergy, 2 2, Ghamarian, A The exergy method of power plant systems analysis and its application to a pressurized bed coal-fired combined-cycle power plant, The George Washington University, Washington, D.C. Kaya, D., and Eyidogan, M Energy conservation opportunity in boiler systems. J. Energy Resour. Technol., 131 3, Kaya, D., Sener, T., Sarac, H. I., and Cankakilic, F Energy conservation opportunity in boiler systems. Proc., Energy Efficiency Congress, Energy Efficiency Congress, Kocaeli, Turkey, Kilicaslan, I., and Ozdemir, E Energy economy with a variable speed drive in an oxygen trim controlled boiler house. Int. J. Energy Res., 127, Onat, K., Genceli, O., and Arisoy, A Heat calculation in steam boilers, Denklem, Istanbul. Rosen, M. A., and Dincer, I Exergy analysis of waste emissions. Int. J. Energy Res., 23 13, Sayin, C., Hosoz, M., Canakci, M., and Kilicaslan, I Energy and exergy analyses of a gasoline engine. Int. J. Energy Res., 31, Stultz, S. C., and Kitto, J. B Steam its generation and use, 40th Ed., Babcock & Wilcox Company, Barberton, Ohio. West, T From mechanical to electronic control on industrial burners. Technical bulletin, Energy Technology and Control Ltd., Lewes, U.K. JOURNAL OF ENERGY ENGINEERING ASCE / MARCH 2010 / 25