burners in rotary cement kiln

kiln burner and flexiflame - a tec - innovative technologies for tailor-made solutions (atec)

kiln burner and flexiflame - a tec - innovative technologies for tailor-made solutions (atec)

While the Standard Kiln Burner has three shaping airflows, the FLEXIFLAMERotary Kiln Burner operates with four airflows.The unique design of the burners with two tangential airflows to enfold the solid fuel injection flow - allows, throgh simple procedures, to optimize complex fuel firing and increased control over NOx emissions.

A TEC GRECO burners are developed to meet, with flexibility and without any efficiency loss, the specific necessities of rotary kilns for clinker for white and grey cement production, lime and pozzolana, among others products.

With four independent air channels, FLEXIFLAME burners deliver a flame with the best shape and settings for the production process, feedstock and fuel mix. Through simple procedures as opening (or closing) inlet air valves, kiln operators can optimize firing conditions in a way that is not possible for burners that do not count on FLEXIFLAME features.

The FLEXIFLAME burner versatility and features - that includes the capability to be operated locally or via remote control - make it the best option for applications where NOx emissions control are mandatory or when the firing includes complex fuels, including alternative fuels like plastic fluff. FLEXIFLAME main features:

flsmidths rotary kilns for enhanced thermal processing

flsmidths rotary kilns for enhanced thermal processing

At FLSmidth, we understand how important it is to have a burner that offers complete combustion and is able to produce the most effective thermal processing available. Because of this, we have engineered a range of rotary kiln burners that provide you with efficiency, versatility, and quality.

As it is our promise to create systems that are more sustainable, our rotary kiln burners have been designed to lower the amount of nitrogen oxide being put into the atmosphere. They are capable of functioning with a wide range of fuels, including alternative fuels, such as methanol and hydrogen. They are also multi-channel systems, providing more productive combustion of materials. With numerous configurable features to choose from, we aim to satisfy.

FLSmidths Uniflow Burner is a rotary kiln burner that offers a versatile processing experience. As a two-channel machine, fuel is placed into one channel, while the other channel is filled with primary air, resulting in a burner that is more compact and can be used with smaller kilns. It is compatible with alternative fuels and possesses features that are designed to lower emissions, giving it a lighter environmental footprint. It is highly configurable and customisable, allowing you to dictate its applications as well as its parameters.

The FeNi Burner is a variant of the Uniflow Burner, with three channels instead of two. While the first two channels complete the same processes as the Uniflow Burner, the third channel is used to process secondary air, allowing it to achieve a more complete combustion of fuel. Although it is less compact than the Uniflow Burner, it provides you with a second option that offers similar benefits.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

cement kiln burners d-flame. - dynamis

cement kiln burners d-flame. - dynamis

Burner designs for modern clinker kilns must fulfil several requirements. Operational flexibility, high durability, low energy consumption, easy tuning, low emissions, and fuel flexibility are some of these requirements to be met. The evaluation of many of these features is straightforward.

Nevertheless, none of them contemplate geometrical aspects which are certainly paramount too if overall performance is to be enhanced. Therefore, relying on these indices alone to evaluate a burner might lead to lack of information on the process once combustion is governed by far more complex phenomena.

Dynamis has recently adopted a more complete methodology to evaluate and compare burner designs in order to develop its new generation of burners: the D-FLAME. This development is the result of many years of Dynamis experience in this field, highly specialised technical body, as well as customer feedback. The new D-Flame burner is the product of a complete analysis of factors crucial to burners performance enhancement, such as the one addressed here: the secondary air entrainment into the fuel injection region.

For the same primary and secondary air flow rates, and consequently the same swirl, turbulence and impulse indices, tests with different designs for the external and tangential primary air were carried out to verify how the geometry of the burner head might improve not only the burners performance but also the whole kiln operation.

On the left hand side of figure 2, it is presented four control surfaces at different cross sections from burner head: CS1, CS2, CS3 and CS4, located, respectively, half a metre, one metre, one and a half metre and two metres away from it.

Measurement of secondary air entrainment calculated on these control surfaces (CS1 to CS5) for all geometry design considered are shown on figure 3. It can be seen that the fewer the nozzles on the head for the external and tangential primary air, the higher the value of secondary air flow rate through control surfaces CS1 to CS4, with one only exception for surface CS1, half a metre away from burner head, for the configuration of 6 orifices. For the cylindrical surface CS5, only the flux entering into the fuel injection region were considered once the flux coming out of it could be related to the expansion due to combustion of coal and, therefore, should not be taken into account in such analysis.

Evidence supporting that there is an improvement of secondary air entrainment into the fuel region for a smaller number of nozzles on the head is seen on figure 4. In this figure, the coal particle tracks calculated are coloured by the char mass fraction of coal, with the red colour on the range indicating that particles are volatile free. The black plume is, therefore, shorter for configurations with fewer nozzles for primary external and tangential air on the burner head.

The temperature profile along the kiln length for all cases studied seemed, at a first glance, to be similar for all configurations, with exception of the annular case that showed a very unstable profile. But a closer look onto the temperature profile, as shown in figure 5, reveals a cooler region near the burner head (indicated by the darkest shade of blue) as the number of nozzles raises. This is again an indication that the hot secondary air entrainment is greater in head configurations with fewer nozzles.

By assumption, the burner head is adiabatic. So the temperature gradients are solely due to the entrainment of hot secondary air in this region. For the annular configuration, the external primary air creates a barrier, isolating the central region of burner head, and preventing secondary air to get mixed with the fuel in the first few metres.

Figure 7 shows the radial velocity near the burner head. Only the negative values of this variable were considered since the aim is to identify which configuration allowed more secondary air into the fuel injection region. In this case, it seems that the head with 6 openings is not as symmetrical as the other configurations. This might suggest that there is some degree of instability for this head design. Looking at the designs with 12, 18 and 24 orifices, it can be noticed that the radial velocity reaches its peak around the external primary air injection. For the other 3 cases, annular, 36 and 48 orifices, the values for the radial velocity are 33 to 50% smaller around this region.

Last but not least, it was set a correlation between a new dimensionless geometrical index proposed by Dynamis, as defined below, and the flux of secondary air entrainment into the fuel injection region per nozzle interval, as presented by figure 8. The proposed geometrical index is defined by:

Where d is the distance between nozzles, Dh is the external primary air orifice hydraulic diameter, R is the distance from the centre of the head to centre of the external primary air orifice, Dh_eq is the equivalent annular hydraulic diameter of the external primary air, and C is a constant.

The key purpose of a burner is to enable the use of fuel by creating the conditions for proper reaction rates as efficiently as possible. This purpose is achieved by the injection of primary air through the burner channels. Rather than being a reactant in the combustion, primary air is mostly related to the entrainment of secondary air in the fuel stream, the formation of recirculation zones and the increase of turbulence levels to improve mixing.

Regarding the secondary air entrainment, burner head geometry makes a huge contribution to its optimization, as it has been indicated by the study presented in this article. It is essentially a local phenomenon which can only be entirely assessed using well posed CFD (Computational Fluid Dynamics) simulations. The amount of secondary air entrainment is considered by Dynamis to be of great impact on burners performance.

CFD simulations show that head designs with fewer nozzles tend to raise the suction of secondary air in the first two metres off burner head. On the other hand, there are physical aspects that cannot be ignored if a small number of nozzles are employed. The most important of them is that the cooling of burner head could be highly affected, causing overheating and consequently wearing out.

It was also noticed that, despite the head design with 6 orifices for the primary external and tangential air injection had presented higher values of secondary air entrainment in almost all control surfaces evaluated, its performance in the near head region might be compromising, as evidenced by the radial velocity.

rotary kiln burners | northstar combustion, inc. | low nox, multi-fuel

rotary kiln burners | northstar combustion, inc. | low nox, multi-fuel

Maintaining the proper heat profile of a rotary kiln is of the utmost importance in realizing the lowest Btu per ton of production as well as the highest quality product. To achieve the optimum burner flame shape and the most efficient combustion possible, the rate of mixing of both the air and fuel through the burner is paramount. NorthStar ProflameTMRotary Kiln Burners are capable of adjusting the flame shape and intensity while in continuous operation with no shutdown necessary. This has the effect of eliminating costly downtime and process temperature fluctuations that may otherwise affect your kilns heat profile and overall efficiency. In other words, although the rotary kiln burner is custom engineered for your specific target burning rate an operator may reconfigure the burner with simple, easy to perform adjustments should production parameters dictate a change in fuel consumption or flame shape. ProflameTMrotary kiln burners are capable of 10:1 turndown and can operate as much as 50% over the target design firing rate.

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cfd modeling of combustion in cement kiln - cfd flow engineering

cfd modeling of combustion in cement kiln - cfd flow engineering

The cement kiln is one important part in cement production industries and it is used to heat the cement mixture. It rotates slowly at its axis. The cement kiln is exposed to carry high temperature cement mixture. The inner surface kiln has high temperature around 1200 C and outer surface is exposed to ambient temperature. To maintain structural strength, its our surface is continuously cooled with air or water jets.

In the enthalpy (energy) equation, there is the source term, Sh due to combustion That is heat source and heat transfer within the system that affect temperature of flue gases. In rotary kilns, heat transfer mode is dominated by thermal radiation.

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