High Emissivity Ceramic Coating of Furnace Walls in Tubular … · 2018-08-22 · In fired heaters and tubular reformers, the necessary thermal energy to drive the endothermic processes

High Emissivity Ceramic Coating of Furnace Walls in Tubular Reformers

Theory and practice

The furnace walls in a tubular reformer are lined with refractory, bricks and fiber materials having a relative low emissivity. By applying a “High Emissivity Coating” on the surface of the furnace walls, it is possible to increase the emissivity and thereby improve the thermal efficiency of the furnace box significantly. The enhanced efficiency of the furnace box can be utilised to alleviate excessive temperatures in the convection section, increase the capacity of the reformer or prolong the lifetime of the catalyst tubes. The lifetime of the catalyst tubes in side wall fired tubular reformers may be further prolonged if the heat release of the bottom row burners can be reduced to half the heat release of the upper row burners. In addition, several other secondary benefits are obtained by sealing the furnace walls with the coating material. High emissivity coating of the furnace walls have been applied in several tubular reformers with satisfactory results. Industrial feed-back from two plants and two case histories are presented.

Peter Bruun Jensen Haldor Topsøe A/S

Copenhagen, Denmark

Venkat Pattabathula and Stephen Maule Incitec Pivot Ltd,

Brisbane, Australia

John Bacon Cetek Limited

Brook Park, OH, USA

Darius Pasaribu Kaltim Pasifik Amoniak

Bontang, Indonesia

532011 AMMONIA TECHNICAL MANUAL

50 AMMONIA TECHNICAL MANUAL2012

Introduction

atalytic steam reforming of hydrocarbons in tubular reformers is the most common process for production of synthesis gas.

The reforming reactions are highly endothermic and the heat is provided by combustion of fuel gas in a furnace box and transferred to the catalyst tubes mainly by radiation. The thermal efficiency of the furnace box is typically 45-60% and additional 35-50% of the heat is recovered from the flue gas in the reformer convection section. The recovered heat is used for preheating of reformer feed, process air, steam superheating and preheating of boiler feed water or combustion air. The thermal efficiency of the furnace box can be increased by applying a high emissivity ceramic coating on the furnace walls which enhance the radiative heat transfer contribution from the hot furnace walls to the catalyst tubes. However, the efficiency improvement depends on the reformer design and the actual conditions in the reformer. Tubular steam reformers are divided into four categories depending on the location of burners and the arrangement of the catalyst tubes in the furnace box. Please see Figure 1.

Figure 1. Reformer furnace configurations

Top fired and bottom fired reformers have the catalyst tubes arranged in several parallel rows with the burners located between the tube rows

either in the top or the bottom of the furnace box. The area and angled view of the surrounding furnace walls relative to the catalyst tube plane limits the radiative heat transfer contribution from the hot furnace walls to the catalyst tubes except for the outermost tubes near to the furnace walls. Attempts of enhancing the radiation efficiency of the furnace walls may impair the heat distribution in the furnace box as the tubes near the furnace walls will receive relatively more radiation than the other tubes in the furnace box. This however can be mitigated by installing lower duty burners in the outside rows and next the end walls. Side wall fired and terrace wall fired reformers have the tubes arranged in single rows between two opposing furnace walls on which the burners are located either in typical 6-7 horizontal rows or in two horizontal terraces. The area and direct view of the surrounding furnace walls relative to the catalyst tube plane results in a significantly higher and more uniform radiative heat transfer from the hot furnace walls to the catalyst tubes than obtained in top and bottom fired reformers. The radiative heat transfer from the hot furnace walls to the catalyst tubes amounts typically to 20-30% of the total heat transfer in a side wall fired reformer. The more uniform and higher radiative heat transfer contribution from the furnace walls makes the side wall fired and the terrace wall fired reformers superior with respect to utilisation of enhanced radiation from the furnace walls. In fact, as explained later, the degree and flexibility of utilising the enhanced radiation of the furnace walls depends on the applied firing profile and the flexibility to change it. The Topsoe side wall fired reformer is ideally suited for this optimisation as the firing profile can be changed by individual adjustment of the heat release in the horizontal burner rows.

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54 2011AMMONIA TECHNICAL MANUAL


Cetek’s Proprietary High

Emissivity Coating Technology The use of high emissivity ceramic coatings, applied to the refractory surfaces in radiant sections of fired heaters and tubular reformers, was pioneered by Cetek and has now become an accepted means of improving the efficiency of radiant heat transfer, leading to energy savings as well as environmental and reliability benefits. A range of ceramic coatings have been developed and used reliably for many years, for different substrate types, operating environments and targeted application benefits. In fired heaters and tubular reformers, the necessary thermal energy to drive the endothermic processes is provided by burning a fuel/air mixture and transferred to the process by three heat transfer mechanisms: radiation, convection and conduction. The primary means of heat transfer is by radiation.

Why High Emissivity?

In the radiant section, of tubular reformer, much of the radiant energy from the flame/flue gas is transferred directly to the process/catalyst tubes; however, a significant proportion interacts with the refractory surfaces. The mechanism of this interaction has an appreciable effect on the overall efficiency of radiant heat transfer. A major factor in determining the radiant efficiency is the emissivity of the refractory surface. At process heater operating temperatures, new ceramic fiber linings, for example, have emissivity values of around 0.4. Insulating fire brick (IFB) and castable materials have emissivity values around 0.6. These materials have been designed with structural considerations and insulating efficiency as the primary requirements. They tend not to handle radiation in the most efficient way. Cetek Ceramic Coatings, however, with emissivity values of above 0.9, have been

designed specifically to supplement the radiation characteristics of the refractory surfaces. It is important to understand how the emissivity property of a surface can affect the efficiency of heat transfer. There are two factors which need to be taken into account. The first is the spectral distribution of the radiation absorbed/emitted from a particular surface and the second is the value of the emissivity of that surface. The amount of heat, Q, radiated from a surface (area, A; temperature, T; emissivity, ε) is given by the following, well-known Stephan Boltzman equation: Q = AεσT4

Where σ is the Stephan Boltzman constant. Lobo & Evans (1) and others extended the calculation with reference to fired heaters and a simplified equation would appear as: QR = Aσ(T1

4-T24)/F

Where F = 1/ε1+{A1/A2}{(1/ε2)-1} for tubes of area A2, surface temperature T2 and emissivity ε2 are inside an enclosure, area A1, with surface temperature T1 and emissivity ε1. The effects of maximizing the emissivity ε1 of the enclosure are obvious; there is a significant increase in radiant heat transfer to the tubes. As stated earlier, much of the radiant heat to the tubes travels directly from the flame/flue gas, but the emissive property of the refractory surface has a profound effect. The chart in Figure 2 shows the energy spectra for two major components of the combustion products of natural gas; water vapour and carbon dioxide. They are compared with the spectrum of a perfect radiator, or black body, at the same temperature. The combustion products will radiate and absorb energy in the narrow wave bands shown, whereas a black body will radiate and absorb energy over a much wider wavelength range.



Figure 2. Energy Spectra of Combustion Products

Products of Natural Gas

High emissivity surfaces are able to radiate energy across a broad wavelength band lessening the interference of the CO2 and H2O in the flue gas. When the radiation from a flame strikes a perfect radiator, all of the energy is absorbed, but most importantly, it is transformed into “black body radiation”, as the wide waveband form. As the energy is re-emitted from the surface, it is able to penetrate the atmosphere in the furnace, composed of the combustion products, with little being re-absorbed and taken to the stack by the draft. Therefore it is more readily available to heat the load in the furnace. If the surface were a poor radiator, or one having a very low emissivity value, the energy striking the surface would be reflected back from the surface still in its untransformed state, therefore more readily absorbed by the furnace atmosphere. The effect is to “super-heat” the furnace atmosphere, or flue gas, resulting in wasted energy lost to the stack.

of Natural Gas

The improvement in radiant heat transfer efficiency naturally leads to a reduction in flue gas temperature. This has consequences in the convective heat transfer in both the radiant and convection sections of the fired heater. In the convection section, heat in the flue gas is used to produce steam and preheating of combustion air and often process fluids. The heat transfer/absorbed duty balance should be examined closely to ensure that the balance is not adversely affected. There is also a contribution, though minor, from convective heat transfer in the radiant section, which may be characterized by the following equation:

Qc = hcA2(T1 – T2) Where hc, the film heat transfer coefficient, is an empirically derived factor related to the design of the radiant section and the tube configuration.

Cetek’s Evaluation Process

Cetek’s high emissivity ceramic coatings applied to the refractory surfaces provide a significant effect, which varies for different types and designs of fired heaters, or tubular reformers. In order to

Spectral distribution of radiation emitted by a black body at

temperature 1350 K.



derive the most benefit, it is important that a complete technical analysis/evaluation of the effects of the application is completed beforehand. The benefit in the radiant section and the effects on the convection section are studied and reported, before any commitment is made by client, or Cetek. Typical approved applications in steam methane reformers show productivity benefits (as energy savings, or production increase) ranging from 2.5% to 5.0%. The life of the coating system applied to refractory surfaces is related to the temperature to which it is subjected and the local environment. Typically in steam methane reformers the coatings will gradually lose emissivity, declining from over 0.9 to around 0.8, after approximately 6 to 8 years. This is still substantially higher than the original, uncoated refractory. At this stage it is recommended to touch-up the coatings to boost the emissivity to the original level and restore performance. The deterioration is caused by high temperature, solid state diffusion of the elements in the coating which provide the high emissivity property. The rate of deterioration may be increased by localized flame impingement.

Environmental Benefits from Cetek’s High Emissivity Coatings

The reduction in flue gas temperature leads to a significant reduction in thermal NOx emissions. The typical reduction in NOx emissions in steam methane reformers is 20% to 30%, irrespective of burner type. CO2 emissions are reduced proportionately with the productivity benefits. Cetek’s ceramic coatings (high emissivity or neutral emissivity) provide a real encapsulation of ceramic fiber (blanket, modules, or panel) insulation. There is no loss of friable fiber from radiant sections and therefore no fouling of radiant section tubes/catalyst tubes, convection section tubes, screens of SCR (Selective Catalytic

Reduction) units or loss to the environment, through the stack. Entry to radiant sections during shut downs is less hazardous since negligible contamination results.

Haldor Topsoe reformer simulation

for evaluation of high emissivity

coating

Tubular reformers and the associated convection sections are complex units operating close to the mechanical design limits. Balancing the reactivity in the catalyst tubes and heat flux along the tubes is obviously essential, but also a correct heat balance between the radiant furnace box and convection section is important to obtain maximum utilisation of the reformer capacity without compromising the mechanical design limits of the unit. Application of high emissivity coating of the furnace walls will increase the radiative heat transfer from the furnace walls to the catalyst tubes and thereby change both the heat flux in the radiant furnace box and heat balance between furnace box and convection section. In-depth analysis of these changes is recommended to determine and optimise the impact on the reformer and plant performance prior to application. Advanced process modelling of the tubular reformer and associated convection section, based on detailed equipment information and actual operating data, is required to accomplish a reliable impact study. In Topsoe, we use our in-house developed proprietary programs for process simulation. A reformer impact study will typically include process modelling by use of following programs: GHEMB – a general heat and mass balance program to reconcile the operating data and evaluate the overall impact, by changing operating parameters, on the entire process plant.



CROSSHEX – a detailed heat exchanger program to simulate the series of coils in the reformer convection section. REFRAD – a detailed reactor and furnace modelling program to simulate the complex interactions of heat transfer and coupled chemical reactions in the tubular reformer furnace box. The furnace model (2) is based on a multi-zone radiation model and divides the furnace chamber into a number of gas, burner, furnace wall and tube wall zones and calculates the radiative heat transfer between them. The flue gas radiation is modelled by a one clear + three grey gas radiation model in order to allow the radiation from the furnace wall to the tube wall in the clear window and weight the ratio of the two radiating components (H2O and CO2) in the flue gas. The clear window is obviously important to account for the increase in radiative heat transfer from the furnace wall to the tube wall when the furnace wall emissivity increases after application of the high emissivity coating. The furnace model is combined with the catalyst tube model by converging the heat flux profiles in the two models.

Figure 3. Modelling of reformer furnace chamber

The first step in the impact study will be a detailed simulation of the actual reformer operation to verify the process model and identify the operational constraints in the reforming unit. Next step includes process simulation with increased

emissivity of the furnace walls, after application of the high emissivity coating, and finally various operating scenarios are investigated to find the optimum solution for the plant. If deemed necessary, the threshold condition for re-coating can also be calculated as the coating efficiency will decline over time.

Primary benefits obtained by coating

The operating constraint in tubular reformers is normally imposed by one or more of the following parameters:

Maximum temperature of the flue gas outlet from the radiant box

Maximum or minimum temperatures of process stream outlet from the convection section coils

Maximum metal temperature of catalyst tubes (TMT)

Maximum heat release of the burners

Increasing the furnace wall emissivity will increase the thermal efficiency of the furnace box and result in lower temperature of the flue gas outlet from the radiant box and also lower fuel gas consumption if the outlet process gas temperature is maintained. Simulations of side wall fired tubular reformers before and after coating, with the expected changes in furnace wall emissivity, show a flue gas temperature drop of 25-50oC (45-90oF) outlet the radiant box and a corresponding drop in fuel gas consumption, after coating. The degree of temperature drop depends on the furnace geometry, applied firing profile and change in furnace wall emissivity. Similar drop in flue gas temperature has been observed in industrial side wall fired tubular reformers after coating. In case the firing profile remains unchanged after coating, in order to benefit from the lower flue gas temperature and lower fuel consumption, the calculated decrease in maximum tube metal temperature (TMT) will be less than 2oC (3.6oF).



However, many reformers in ammonia plants have to maintain a constant flue gas temperature at the inlet to the convection section, or at least inlet to the steam superheating coil in order to keep the temperature of the superheated high pressure steam unchanged. These plants will have to increase the firing in the upper part of the furnace box, which decreases the firing in the lower part of the furnace box as the total heat input to the reformer remains unchanged to maintain the outlet process gas temperature constant. Reformer simulations with change in firing profile i.e. increased firing in the top row of burners and decreased firing in the remaining burners after refractory coating shows typically a drop in the maximum TMT of 2-5oC (3.6-9 oF). If all burners in the lower part of the furnace box operate at the same heat release, the TMT will increase all the way down to the bottom of the furnace box. In case the flue gas temperature outlet from the furnace box, after coating, is increased by decreasing the heat release of the bottom row of burners, and maintaining the outlet process gas temperature constant, the maximum TMT will decrease significantly and the location of the maximum TMT will move upwards from the bottom of the furnace box. Reformer simulations show that the maximum TMT will decrease by 5-10oC (9-18oF) and move a few meters upwards in the furnace box if the heat release in the bottom row of burners is decreased significantly to increase the flue gas temperature outlet from the furnace box. Furthermore, the TMT in the bottom of the furnace box, where the creep damage of the tubes is most pronounced, will decrease by 10-15oC (18-27oF). The above mentioned reduction in maximum TMT of the catalyst tubes is small but still significant considering the rule of thumb, derived from the Figure 4, that operating the catalyst tubes 15-20oC (27-36oF) below the design temperature will double the tube lifetime.

Figure 4. Tube lifetime for various materials

In case the tubular reformer is operating at its capacity limit due to the above mentioned constraints, there is a potential for production gain by improving the furnace wall radiation and optimising the firing profile in the furnace. Simulation of side fired tubular reformers aiming at the same maximum TMT, outlet temperatures of flue gas and process gas, respectively, before and after coating indicate that the production of synthesis gas can be increased by 2-4% after coating.

Secondary benefits obtained by coating

In addition to the benefits derived from the enhanced furnace wall emissivity, refractory coating may also provide secondary benefits like:

Preservation of the lining material around burners, which otherwise is slowly degraded/eroded due to exposure to the flue gas being at high temperature and high velocity when it leaves the combustion zone.

Elimination of refractory dust from

erosion, which otherwise may deposit on the tube surface and decrease the tube wall emissivity resulting in lower thermal efficiency of the furnace box and convection section.



Absence of refractory dust on the tubes makes the TMT measurement less scattered and more reliable due to higher certainty about the tube wall emissivity.

The lower flue gas temperature will result

in lower NOx emission. Furthermore, coating of fiber materials will make the material less unhealthy as the fibers will be encapsulated in the coating.

Case history 1

Incitec Pivot (IPL) operates an Ammonia plant designed by J.F Pritchard, commissioned in 1969, that produces around 890 MTPD of Ammonia. The Reformer is a single cell Foster Wheeler design with a straight row of 108 catalyst tubes heated on each side by two decks of 24 up–firing burners. Downstream of the radiant section, is a mixed steam and natural gas (mixed feed) coil in the transition area before the convection section. In the convection section there is auxiliary firing for steam generation, and for superheated steam. Two induced draft blowers draw air locally through the radiant section burners, and convection section burners. The reformer radiant section is a mixture of approximately ¾ castable brick and ¼ ceramic fiber. Typical furnace draft is -0.1in W.G at the arch and stack exit temperature of 193oC (380 oF). Background In Australia a requirement exists for large energy using companies to identify opportunities to improve energy efficiency under the Energy Efficiency Opportunities Act. The number of opportunities that have been identified, and the status of these opportunities, have to be reported to the public and to the government each year. However, there is no requirement to implement the opportunities identified. This legislation encourages companies to identify and improve energy efficiency and provides additional impetus

to complete energy efficiency projects. IPL identified the potential to install the reformer coating through networking with other Ammonia producers, and this project fitted in with the IPL strategy to improve energy efficiency. In 2008 IPL provided baseline information to Cetek to evaluate the potential benefit of applying the coating in the radiant section. The initial potential benefit, as modelled by Cetek, was a fuel saving of 3.75% to 5% in the radiant section, and a reduction in bridge wall temperature (temperature exit of the radiant section prior to the transition area) of 42oC (75oF) for the same production rate. Alternatively, a similar gain in production was predicted for a constant fuel gas rate. At the IPL plant, the bottleneck for production is normally in the back end of the plant, meaning the target for the project would be in pursuing energy savings not additional production. The other predicted benefit of the coating was a more even split between the top and bottom burner rows. IPL had been running the reformer with significantly more firing on the bottom row of burners; so that the top row of burners could be turned down in order keep the outlet temperature of the downstream mixed feed coil under its alarm temperature. IPL investigated the impact of the reduced temperature from the flue gas on the convection section in more detail to determine if there would be any adverse effect on plant operation. This study determined that the existing superheat coil was significantly underperforming. Replacement of this coil and installation of new brickwork (corbel bricks) would mean the current high rate of auxiliary firing would not be needed and the reduced temperature of the flue gas would not impact superheat temperatures. IPL was planning on doing significant maintenance work on the reformer in the 2011 shutdown, and this was the next available



opportunity to implement the coating. In order to gain more understanding of the practical impacts of the coating, three engineers travelled to Indonesia in 2010 to review two other plants that had also implemented the coating. The feedback from the other plants was positive and as a result of this trip, the project was added to the shut-down scope.

Implementation

The coating was installed by a staff of 6 after all the other work had been completed in the radiant section. The installation of the coating was not on the critical path for re-commissioning, as other work was still progressing in the convection section. Initially, the reformer was cleaned by wire brushing the castable brick and flattening the ceramic fiber with a nylon brush.

Figure 5. Cleaned castable brick and flattened

ceramic fiber

The dust generated from this activity was blown down from the reformer with air. Long plastic sheeting was installed to protect the reformer tubes from any overspray. The ceramic fiber was applied with a rigidizer as a base layer and top coated with R371. The castable brick was then coated with a base layer (R360) and a top coat (R371). As the project was not on the critical path, only day work hours were required and the whole process of cleaning the final coat took 3 days.

Figure 6. Ceramic fiber coated. Castable brick

uncoated

Figure 7. Coated and uncoated wall during job



Figure 8. Finished castable brickwork

Results

After the plant was restarted, a reduction in natural fuel gas was noticed to the reformer for the same production rate. This was due to a combination of not having to fire auxiliary burners in the convection section; due to the super heater coil replacement, and also a reduction in radiant section firing due to the Cetek coating. In the radiant section the balance between top and bottom decks was adjusted to increase firing on the top deck, while reducing the firing pressure on the bottom deck. Importantly this increase did not result in higher outlet temperatures of the downstream mixed feed coil, which typically runs close to its alarm temperature. Comparing a long baseline period before and after the changes were made showed that the overall measured improvement was approximately 600 GJ/day for the same production rate. The super heater replacement was typically contributing 250 GJ/day, and the Cetek coating 350 GJ/day which is approximately 4% saving in fuel gas for the radiant section. The steam generation in the convection section had reduced from 120 klb/hr to 100 klb/hr. This was due to a combination of reduction in auxiliary firing of superheat burners (which in addition to superheating also raised steam), and reduced flue gas temperature from the

radiant section due to Cetek coating. The bridge wall temperature before the mixed feed coil had also reduced by approximately 50oC (90oF) compared to previous operation.

Case history 2

P.T. Kaltim Pasifik Amoniak (KPA) operates a 2000 MTPD ammonia plant located within the Kaltim site in Bontang, Indonesia. The process design for the plant was by Haldor Topsoe. At the time of its commissioning and acceptance in May, 2000 it was the largest single train ammonia plant in the world. The Primary Reformer is a side-fired Topsoe design with draft fans located at the top of the convection section. Sidewalls and roof are insulated with ceramic fiber insulation. From the beginning of operations it was evident that the Primary Reformer operated with high bridgewall temperatures at the top of the radiant section. These high bridgewall temperatures resulted in high process temperatures from some of the lower convection section coils. Since some of these convection coils were operated close to design temperatures, various means were investigated to bring down the bridgewall temperatures and Cetek’s proprietary high emissivity coating technology was an obvious candidate. Both KPA and Cetek carried out evaluations of the benefits of the technology and the decision was made by KPA to proceed. The coating was carried out on a turnaround in November of 2007. The work was done by Cetek technicians in four days and had no impact on the overall duration of the turnaround. Figure 8 and 9 below show the condition of the refractory coating before box-up in 2007.



Figure 9. Ceramic coating condition on ceramic

fiber end wall

On plant start up following the installation of the Cetek coating, bridge wall temperatures were noticeably lower. Both indicated temperatures and calculations by Topsoe showed that bridgewall temperatures were reduced by 40 to 50oC for the same operating rate. Fuel gas efficiency for the reformer was improved by over 2%, and process outlet temperatures were easily achieved without overheating the bridgewall.

Figure 11. Thermal deterioration of ceramic coating

Figure 10. Ceramic coating condition on brick

side wall

Some (not all) of the top row reformer burners which have not been in operation before were then able to be lit. Plant throughput capability was also raised by an estimated 2%. Because the impact of this coating on plant operations was so marked it was decided to re-apply the coating to furnace walls in 2011 as the thermal coating effect deteriorated over time as shown below.



Other industrial feed-back after

coating

Topsoe have received feed-back from two other HTAS licensed ammonia plants, PT Kaltim Parna Industri’s 1500 MTPD ammonia plant in Indonesia (KPI) and Profertil’s 2050 MTPD ammonia in Argentina (PFT), after coating of the furnace walls in their side wall fired tubular reformer. Both plants were coated by Cetek in year 2008, with the primary objectives to increase the thermal efficiency of the furnace box and utilisation of excess firing capacity in the top row burners. KPI observed a drop in flue gas temperature outlet from the furnace box of 27oC after coating. Shortly after start-up, the firing profile was optimised by igniting several burners in the top burner row which reduced the heat release in the lower burner rows. The change in firing profile increased the flue gas temperature outlet of the furnace box by 10oC but reduced the measured maximum TMT of the catalyst tubes approximately 2oC. Subsequently, the plant load was increased by 2.5%, which resulted in additional 10oC temperature rise in the flue gas outlet from the furnace box. PFT experienced a substantial drop in flue gas temperature outlet from the furnace box after coating and adjusted immediately the firing profile after start-up by igniting all burners in the upper burner row, which had previously been switched off to avoid excessive temperatures in the convection section. Although the firing profile was changed significantly after coating a temperature drop of 25oC was observed in flue gas temperature outlet the furnace box.

Conclusion

The benefits obtained after applying high emissivity coating of the furnace walls in side fired reformers, can either be utilised as stand-alone benefits to save energy, lower emissions,

prolong lifetime of the furnace wall lining and catalyst tubes or gain synthesis gas production depending on the operating constraints in the reformer or it can be included as an integral part of a more comprehensive optimisation of the reformer unit. The expected benefits from coating have been obtained in many tubular reformers but the effect will decline over time due to deterioration of the coating material. The thermal lifetime of the coating is typically 4-8 years depending on the coating work and the environment in the furnace box. The declining rate should be followed closely in order to identify the right time to reapply the coating and fit the work into the normal turn-around period.

References

(1) Lobo, W. E. and Evans J.E. (1939) Trans AIChE, 35-743.

(2) Rostrup-Nielsen, and Christiansen, L.J in “Concepts in Syngas Manufacture” Catalytic Science Series – Vol.10, 2011, Imperial College Press, London



Documents

High Emissivity Ceramic Coating of Furnace Walls in Tubular … · 2018-08-22 · In fired heaters and tubular reformers, the necessary thermal energy to drive the endothermic processes