Hagen am Teuteburger Wald, Germany
Hagen am Teuteburger Wald, Germany

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Rakette R.,NOXMATGmbH | Mader D.,NOXMATGmbH | Neumann B.,EJOT GmbH and Co. KG
Gaswaerme International | Year: 2017

In the field of process heat utilization, various measures are available for increasing energy efficiency. According to the technological process, a large part of the process heat is generated as waste heat. It is a very effective way of recycling this waste heat directly to the process, e. g. by means of intensive combustion air preheating at industrial burners. The long proven recuperator burners are limited in energy efficiency due to the restriction of the recuperator surface. The use of metal foam in connection with the robust finned tube design generates higher efficiencies which achieve 10-15 % energy savings compared to conventional finned tube recuperator burners.

Mader D.,Noxmat GmbH | Gamarra O.S.,Noxmat GmbH | Schulze M.,Noxmat GmbH | Lohr R.,Noxmat GmbH
Gaswaerme International | Year: 2014

As a matter of fact, the heating system engenders a major part of current operating and servicing costs of a thermoprocessing installation. It is not rare that saving potentials are latent therein which cannot be immediately detected by the end-user. As regards firing efficiency, the index for combustion efficiency, this is not only attributable to the burner but also to other central components of heating system; contrary to the widespread belief. The present article shows various maintenance concepts and describes, on the basis of examples, where and who optimisation potentials can be opened-up by simple measures, for instance, in terms of efficiency-enhancing maintenance.

The energy-efficient operation of a heat treatment plant heated with natural gas depends greatly on the quality and design of the burners used. Often, the burners do not show their full potential due to inconsistencies in operation or unfavorable conditions. Regardless which type of burner is used, whether it is a modern recuperator or a simple cold air burner, operated directly or indirectly, the air ratio is the first important factor for using the fuel effectively. For normal burner operation an air ratio of 1.05 - 1.2 (slightly above stoichiometric combustion) is usually chosen, corresponding to a level of remaining oxygen of 1.0 to 3.5%. The higher the air ratio is above 1, the more excess air has to be heated in the combustion chamber, which in the case of a cold air burner then leaves the furnace chamber unused. The excess consumption rises sharply with increasing temperature in the combustion chamber. The simplest mixture settings are possible when there is no connection between the gas and air supplies to the burner. The quantities of gas and air can be set separately and in an operator-friendly manner. The advantages of this configuration shown can be demonstrated particularly when looking at the individual cycle time, i.e. from when the air is released, to ignition, the burning phase and extinguishing, to the next release of air in the burner. The supply of the fuel gas and combustion air with constant pressures to the burner inlets is also vital for operating the burner efficiently. It is not uncommon for these pressures to vary greatly for the same plant with varying furnace loads. On the one hand there is the combustion air fan and on the other hand the heat treatment plant's gas inlet section has to be mentioned. Both have a significant influence on the inlet pressures. With the help of practical examples, it is demonstrated how unnecessary excess consumption can arise and how it can be avoided effectively and permanently. Alongside many other possibilities, one way of recovering heat and saving energy is to preheat the incoming air using the energy in the hot waste gas. For recuperative air preheating, central recuperators (central heat recovery) and recuperative burners (decentralized heat recovery) have become established in the industry. A high potential energy savings is the result from preheating the incoming air, depending on different furnace chamber temperatures and levels of air preheating. The reduction in the emissions of the greenhouse gas CO 2 corresponds to the fuel gas savings. With decentralized heat recovery, a higher level of air preheating and therefore a better efficiency is reached as the air is heated directly in the burner without being diverted. Furthermore it is shown, that in case of indirect heating the combustion-efficiency directly depends on the surface size of the jacket tube. A larger surface size can be achieved by a variation of the diameter and the jacket tube height. The use of larger Jacket tubes means at first a higher investment amount, but on the other hand it would reduce the fuel costs while using the burner. As noted in a table the payback period can vary considerably.

NOXMAT GmbH | Date: 2015-11-05

A recuperator for a recuperator burner for preheating combustion air by means of exhaust gas heat in a recuperator burner is disclosed, wherein the recuperator is of a tubular shape with an inside and an outside, wherein a plurality of elevations or ribs and recesses are provided at least on the inside or on the outside thereof and wherein at least one cellular structure, preferably consisting of a cellular metal or an open-pored ceramic foam, is accommodated in one of the recesses, at least on the inside or on the outside. In this arrangement, the inlet air is preferably preheated twice in the burner head, namely, in a first inlet air duct section, by an exhaust duct coaxially surrounded thereby, using cocurrent flow, and additionally by a second inlet air duct section, which is coaxially surrounded by the exhaust duct, using counter-current flow.

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