Hot gas generators with free choice of fuel

Hot gas generators are always used when hot gases are required for direct drying or some other relevant process.

They offer substantial savings potential in that they can be run up to full power within a few seconds, that the targeted temperature can be altered in real time, and that atomized, gaseous and liquid fuels can be used in one and the same burner, hence enabling switchover to the most favorably priced fuel whenever so desired.

Carbotechnik’s patented hot gas generator technology combines all these advantages to achieve maximum performance and best-ever cost effectiveness in combination with high-precision process monitoring and control (Figure 1).

1 Core element of the hot gas generator: the impulse burner

From a technological point of view, there is a fundamental difference between the patented impulse-burner concept and that of conventional systems now on the market. Thanks to its compact design, the Carbotechnik impulse burner generates a flow pattern with unique functional characteristics:

Figure 2 is a schematic diagram of the flow pattern. Essentially, a cold layer is generated around the burner muffle, enabling intimate commixture of the fuel with the combustion air. Thus, the unit achieves optimal combustion and high burnout within the burner muffle. One-off ignition is carried out by a start-up burner. No support flame is required.

The downstream mixing chamber serves to prolong the retention time and for setting the desired temperature. Secondary air is fed into the cooling chamber through an annular gap and only added to the hot gas at the end. The design flow pattern yields a thoroughly homogeneous temperature profile at the outlet of the hot gas generator (or, respectively, at the inlet of the downstream process).

2 Fast, accurate load changing

The system is of all-steel construction and requires no expensive, maintenance-intensive refractory lining, even for high-temperature applications. No time lag is involved for heating up the hot gas generator. Changes in output are effected with practically no time lag and managed with absolute precision by the control system.

3 Low maintenance costs

Carbotechnik systems, being of all-steel construction, are characterized by low lifetime maintenance costs and zero idle time for such time-consuming jobs as refractory lining maintenance. Each individually planned system guarantees maximum harmonization with the overall plant.

4 Reliable fuel supply

If a standardized type of liquid or gaseous fuel is used, e.g., fuel oil or natural gas, fuel infeed is almost sure to be unproblematic. Auxiliary equipment like pumps or compressors provide the requisite pressure head, and appropriate control valves allow the medium to move toward the burner at a constant volumetric flow rate. This fulfills the basic prerequisites for optimal burner operation.

Powdered fuels, by contrast, require a completely different approach: Simple pneumatic infeed by way of an upstream feed screw, rotary valve or the like does not suffice for optimal combustion. Carbotechnik, though, has developed a dosing system that solves the problem with the aid of a horizontal perforated plate. The fluidized fuel fills the holes and is discharged at a rate dependent on the rotational speed of the disk. This way, the fuel dose rate can be controlled with absolute precision and no pulsation for an unlimited length of time and fed pneumatically into the combustion chamber.

5 Electronic monitoring and combustion optimization

Carbotechnik has optimized not only the fuel input, but also the associated instrumentation and control technology. Unlike in conventional units, the fuel/air ratio is not controlled by statically adjusted compound controllers.

In a Carbotechnik hot gas generator, all component flows (air, fuel, …) are accurately monitored and dynamically controlled across the entire output range. This automatically balances out and compensates for any process-dependent changes or fluctuations in the prevailing conditions. It also guarantees an optimally engineered combustion process at all times.

This technology enables the use of various different fuels. For example, the firing system can be switched randomly back and forth between natural gas and powdered fuel with no need for any conversions. Hence, whichever fuel is the most favorably priced at any given time can be used.

6 Assured compliance with emission limits and thermal recycling of waste material

Thanks to such clean combustion, the requirements of the German Clean Air Act (“TA-Luft”) can be reliably complied with, or even beaten, for standard fuels.

Even material that is difficult to recycle, especially climate-destabilizing waste gases or vapors, can be “incinerated”, hence improving both the emission values and the efficiency of the overall process.

7 Digitalization

Plant components like hot gas generators must be integrated as simply as possible into the existing process control systems of complete plants. All control signals, process data and status signals can be evoked via an Ethernet interface set up by Carbotechnik. The plug-and-play control system yields considerable savings potential and enables accurate cost planning from the very start of the project. Service and support are available via remote access at all times. Straightforward visualization permits real-time monitoring of the current status or archive values and their transfer to a smart phone, tablet, laptop or other mobile device (Figure 3). Comprehensive data is collected with pinpoint accuracy for use in application to different processes. This includes, for example, quality assurance in production, consumption monitoring, self-diagnosis or automated service, maintenance and ordering processes.

8 Research, individuality and experience

For purposes of further development, Carbotechnik does not rely solely on existing theoretical calculation programs and simulations. As a leading manufacturer of hot gas generators with 40 years’ experience, Carbotechnik maintains its own research facility in a continuous quest for ever-better optimization and for testing alternative fuels.

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