Polysius
Difficult fuels
made simple.
polflame® VN – the clinkering zone burnerDifficult fuels made simple.
A variable nozzle burner built for a world where the fuel keeps changing. The entire primary air flow runs through concentrically arranged nozzles that can be swivelled steplessly during operation — so the flame is shaped to the fuel, not the fuel to the flame. From 10 to 300 MW, for kilns below 1,000 up to more than 12,000 tonnes of clinker per day.
Key figures strip
| Thermal capacity range | 10 MW to 300 MW |
| Kiln production capacity | less than 1,000 up to more than 12,000 t clinker per day |
| Variable primary air share | 6 % to 12 % of the stoichiometric combustion air |
| Extended warranty | 5 years on the nozzle adjustment system |
| Possible alternative fuel substitution | up to 100 % |
Overview – Meeting Today's Challenges with Advanced Technology
thyssenkrupp Polysius has continuously improved the polflame® VN variable nozzle burner to adapt it to ever-changing requirements. With rising costs for fossil fuels, stricter emission limits and a stronger focus towards a more sustainable operation, the challenges are more ambitious than ever.
In an increasingly fast-paced and complex economic environment, operators must adapt their fuel and environmental strategies more frequently. As a result, firing systems are required to offer high flexibility regarding the fuels used.
The polflame® VN is designed to address these challenges
Variable adjustment of the primary air between 6% and 12% of the stoichiometric combustion air, depending on the fuel and its physical properties
Optimized fuel mixing with hot secondary and primary air for efficient combustion
Easy nozzle adjustment ensures quick burner tuning, leading to optimal performance across a wide range of kiln conditions
Advantages at a glance
Modular design with interchangeable fuel channel configuration
Maintenance-free nozzle adjustment system
Simplified flame adjustment, based on only two parameters: swirl and primary air fan velocity
Optimized nozzle arrangement and diameter
Successful handling of highly abrasive fuels
Customer-tailored engineering to maximize plant performance
Designed for change Conventional thinking assumes that operators already need to know in the project phase which fuel they will be using in the near and mid term. The polflame® VN departs from that: changes in fuels, substitution rates or capacity increases can be implemented without major modifications. The highly efficient nozzle system allows easy adaptation of the nozzle size in order to maintain momentum — for example after a fuel change or a capacity increase.
Proven track record in single machine business & retrofits The polflame® VN is not only engineered for new greenfield plants but serves as a plug-and-play retrofit solution for your single machine business. We routinely replace existing third-party burner systems to upgrade kiln lines to the latest operational standards without requiring extensive civil modifications.
With over 120 burners installed in the last five years—predominantly across demanding markets such as China and Vietnam—the polflame® VN has proven its superior operational reliability, wear resistance, and combustion efficiency under the most diverse and competitive operating conditions worldwide.
Innovative Nozzle Design — Why Nozzles Beat a Ring Channel
Mixing fuels with hot secondary and cold primary air has proven to be quite challenging. Long-term experience, trials and CFD-supported optimizations have shown that injection capacity — even with low momentum — is more effective when using nozzles instead of a ring channel. Furthermore, twisting the flame has a positive effect on significantly increasing injection capacity: the generated swirl improves the mixing of the fuels with hot secondary and cold primary air.
The polflame® VN applies this principle: the entire primary air flow is fed through concentrically arranged nozzles. The nozzles can be adjusted steplessly in a tangential direction during operation, by means of a hydraulic control unit, to achieve the swirl effect.
The advantage is that the primary air is the only flame-forming air stream, compared to the multiple primary air channels of conventional burners. With simple primary air and pressure regulation as well as the air stream direction, the flame can be shaped narrower or wider. In this way, the point of ignition and the flame shape can be adapted according to the fuels used and the emission requirements.
Flame Control — Two Parameters
The task of the sintering zone burner, or main burner, is to create a defined temperature profile in the kiln in order to ensure an optimal clinker sintering process. The required temperature profile differs from kiln to kiln, depending on the fuel used and its physical properties such as moisture, particle size and calorific value. The role of the primary air nozzles is to adjust the flame length and shape in order to optimize the combustion process.
| Parameter 1 — Swirl | Adjusted via the variable nozzles, steplessly and during operation, either directly at the burner or remotely from the control room. Controls flame shape and temperature depending on fuel properties, making it possible to use even difficult-to-ignite fuels efficiently. The patented adjustment system makes reproducible burner settings possible — a key precondition for process stability under demanding boundary conditions. |
| Parameter 2 — Primary air fan velocity | Together with pressure regulation, it sets the momentum of the only flame-forming air stream. Nozzle size can be adapted to maintain momentum after a fuel change or a capacity increase. |
| Low swirl | Long, narrow flame — later ignition, longer residence time. Suits fuels that need a longer burnout path and a gentler temperature gradient along the sintering zone. |
| High swirl | Short, wide flame — early ignition, intense sintering zone. The setting that makes even difficult-to-ignite fuels usable efficiently. |
Coal particles are injected into a hot and oxygen-rich atmosphere, resulting in the immediate heat-up and ignition of the fuel, prior to it being mixed with cold primary air
As a result, even low-quality anthracite can be used without compromising clinker quality
The coal conveying air additionally acts as cooling air
The CFD-optimized coal channel ensures low wear rates, leading to reduced operating costs and a longer service life with highly abrasive fuels
Main Components
The burner has a modular design with interchangeable fuel channel configuration — so it adapts to a change in fuel, an increased substitution rate or an increased kiln production capacity.
| Variable primary air nozzles | Concentrically arranged, stepless tangential adjustment during operation via hydraulic control unit. Interchangeable, so nozzle size can follow a fuel change while keeping energy consumption as low as possible. |
| Outer coal channel | CFD-optimized and, in the area of the coal dust connection, lined with wear-resistant material. The inlet zone can be inspected by opening the inspection cover. |
| Burner tip & mouthpiece | Simplified for quick replacement — f.[OJ1] The outer burner tip is a straightforward wear part exchange. |
| Fuel channels & lances | Interchangeable fuel channel configuration for coal dust, fuel oil, natural gas and alternative fuels. Additional fuel lances can be retrofitted. |
| Hydraulic nozzle adjustment | Maintenance-free system, operable directly at the burner or remotely from the control room. Patented and reproducible. |
| Burner centre | Designed so that centre, burner tip and primary air nozzles can be easily adapted if requirements change — for example a different burner capacity or a different fuel. |
Fuel Range
In the cement industry, fuels are a significant cost factor. To reduce clinker production costs, high-grade standard fossil fuels such as coal, oil and gas are being replaced by lower-quality alternative fuels. Whereas combustion in the precalciner is non-critical from a process-technological point of view, the thermal conversion of alternative fuels in the rotary kiln is a much more demanding process, in which criteria such as process stability and product quality play a decisive role. The polflame® VN is ideally suited to both.
| Standard fuels | Alternative fuels |
| Coal dust · fuel oil · natural gas · highly abrasive fuels such as anthracite and low-grade coals with high ash content | Fuels derived from waste · difficult-to-ignite fractions · mixed operation with several fuels in combination · up to complete independence from fossil fuels without compromising cement quality |
- Thermal capacity
- 10 MW to 300 MW
- Kiln production capacity
- less than 1,000 up to more than 12,000 tonnes of clinker per day
- Primary air share
- variable, 6 % to 12 % of the stoichiometric combustion air
- Flame-forming air streams
- one — the primary air through the nozzles
- Adjustment parameters
- swirl and primary air fan velocity
Reference: Kiln Burner Exchange – polflame® VN References
thyssenkrupp Polysius successfully executed two kiln burner modernization projects in South Africa and Vietnam, demonstrating the flexibility of the polflame® VN burner concept for integration into existing cement plants with minimum downtime.
In South Africa, thyssenkrupp Polysius was contracted to replace an existing kiln burner with a new polflame® VN. The main objective was to minimize plant downtime. Within a total shutdown period of only two weeks, the old burner was dismantled, the new burner installed, and the kiln returned to production. The burner exchange resulted in a modernized burner tip design and improved operational conditions.
In Vietnam, thyssenkrupp Polysius delivered a custom-made polflame® VN burner designed specifically for integration into the existing kiln structure and process conditions.
Service & Maintenance
With the polflame® VN, thyssenkrupp Polysius offers an innovative clinkering zone burner and focuses on both high-end components and best-in-class service when it comes to maintenance and modernizations. In addition to our own plants, we offer comprehensive services for third-party plants, and we apply our knowledge and advanced technologies to other industries beyond cement.
Coal dust connection
In the area of the coal dust connection, the coal dust channel is lined with wear-resistant material. The inlet zone can be inspected by opening the inspection cover, and the wear protection can be replaced if required.
Inspect the inlet zone by opening the inspection cover
Replace the wear protection if required — before the channel itself is affected
Step up the inspection interval when running highly abrasive or high-ash fuels
Burner tip & wear parts
Check tip and mouthpiece condition at every planned kiln shutdown
Keep a mouthpiece on stock — it is simplified for quick replacement
Record the flame divergence before and after replacement
Nozzle adjustment system
Log swirl and fan velocity settings per fuel — the system is reproducible, so use that
Verify remote and local adjustment both respond before a fuel trial
Re-check nozzle size when substitution rate or capacity changes
Five years of extended warranty
The simplified, maintenance-free nozzle adjustment system boosts reliability and durability — which is why thyssenkrupp is able to offer customers an extended warranty of five years on it.
Upgrade & Retrofit
Should requirements change with regard to, for example, burner capacity or fuels, the polflame® VN is designed so that the parts that matter can be adapted to the new conditions.