WO2000040839A2

WO2000040839A2 - Method for the cogeneration of heat and power in conjunction with decentralised heat needs

Info

Publication number: WO2000040839A2
Application number: PCT/GR1999/000049
Authority: WO
Inventors: Athanasios Katsanevakis
Original assignee: Athanasios Katsanevakis
Priority date: 1998-12-30
Filing date: 1999-12-23
Publication date: 2000-07-13
Also published as: GR1003342B; AU1673500A; WO2000040839A3; WO2000040839B1

Abstract

Method of Cogeneration of Heat and Power where turbine CHP set exhaust gases are used desentralised as oxidiser in local distributed heat needs. This invention concerns a new method of applying cogeneration of heat and power in cases where decentralised generation of high temperature -up to 1500 °C or more - heat is needed locally in multiple positions of small up to medium -say up to maximum 500 kW nominal at each position- power. This method is characterised by the decentralised use of the turbine exhaust gases of the CHP set(s) as oxidiser for the local distributed combustion of additional fuel in special burners of small to medium size -say up to 500 kW maximum nominal each-. It is additionally characterised by the ability to enrich exhaust gases with a mixture of air and/or oxygen of various temperature levels and/or compositions. It is applicable in all industries where decentralised generation of heat of up to high temperature level is needed locally.

Description

Method for the Cogeneration of Heat and Power in conjuction with decentralised heat needs The present invention concerns the applicability of Cogeneration of Heat and Power in relation with decentralised heat needs of lower or higher temperature level as those used in e.g. ceramics and heavy clay firing kilns, in re-heating kilns and furnaces in the steel industry, in glass furnaces or in direct fired dryers in the paper, pulp or textile industry etc. It is widely known that Cogeneration of Heat and Power uses more efficiently the available in the fuels energy than the separate generation of Power and Heat. In several cases one of the common obstacles of CHP applicability is the efficient use of the heat which is cogenerated with the power. In many practical cases this is the limiting factor for the applicability of cogeneration methods. Especially in cases where the heat which is needed by the process is of higher temperature level than that produced by the CHP method and, because of process needs, this heat should be generated locally at several distributed points, application of CHP is difficult. Examples include as mentioned above ceramics or heavy clay firing kilns, glass furnaces etc. Moreover the decentralised local generation of heat using small or medium size burners - e.g. up to 500kW maximum nominal output- each one being able to be controlled separately and using natural gas or LPG is known to increase overall fuel utilisation efficiency. This comes among other reasons because of the accurate local control of the heat process demands. On the other hand decentralised heat generation forms a major obstacle for the application of CHP as efficient use of the heat cogenerated is being performed centrally and near the CHP unit(s) to produce steam or diathermic oil of medium temperature levels for the heat needed by the process. Then this diathermic medium is used to cover process heat needs locally. The use of turbine based CHP sets is a usual CHP method and is based on the reliability of these units for continuous operation and relatively low service costs. It is known that the heat generated by the usual turbine sets is of relatively high temperature level -about 500 oC- is mainly in the form of hot exhaust gases and contain a significant amount of oxygen. Thus turbine exhaust gases can be used as oxidiser to burn additional fuel. This method is known to significantly increase the total thermodynamic efficiency of the combustion process depending on the final exhaust gas temperature. This is the reason for the common use of turbine exhaust gases as oxidiser in large centrally located regenerative boilers where additional fuel is burned in special large burners to produce, with proper heat exchange, diathermic medium -usually steam- for the process needs. Then this medium is circulated in the plant to cover the local decentralised heat needs of the process. Having all the above in mind and taking into account that an approach to cope with all the above mentioned facts would form a significant benefit for energy conservation in energy intensive industrial sectors where high temperatures are used, it was found that the decentralised use of turbine exhaust gases as oxidiser in individually operating small to medium nominal size burners used locally where heat is needed by the process, forms an efficient alternative of applying cogeneration of Heat and Power.

Thus the present invention concerns the decentralised use of the exhaust gases generated by the rurbine(s) of CHP set(s), as oxidiser alone or in a mixture with air of various temperatures or even in a mixture with air and/or oxygen of various temperature levels for the combustion of additional fuel locally where distributed and controllable generation of heat is needed.

Exhaust gases are produced by the turbine(s) of the CHP set(s). Exhaust gases may contain oxygen at various volume percentages according to the type and the construction of the turbine. Exhaust gases are guided to the points where decentralised generation of heat is needed. These points are usually distributed along the kilns according to the process temperature profile needed to be achieved in the kiln or in the furnace. There, specially constructed burners of small up to medium size - up to say 500kW maximum nominal output each- are used to burn additional fuel, each one using these exhaust gases as oxidiser. The burners can be individually controlled to achieve process needs. If and when needed, turbine exhaust gases can be enriched by a mixture of air and/or pure oxygen of various temperature levels to achieve process conditions.

By using this method decentralised generation of heat can be achieved by applying simultaneously Cogeneration of Heat and Power with all the related benefits. Moreover it is possible to apply CHP in processes where heat of high temperature level is needed to be generated decentralised and to be locally controllable. Environmental benefits are also significant as the use of the fuel is performed with high efficiency.

Claims

1. Method for cogeneration of Heat and Power where turbine exhaust gases are used as oxidiser. This method is characterised by the decentralised use of the turbine exhaust gases as oxidiser, decentralised as in e.g. the multiple burner ports of e.g. kilns or dryers of up to say 200 meters long, in properly modified or constructed, usual or regenerative, small to medium size, individually controllable burners of up to say 500kW nominal maximum each-, either alone or enriched with a mixture of air and/or oxygen of various temperature levels, to generate heat locally with the combustion of additional fuel, to cover local controllable distributed small to medium -up to say 500kW maximum each- heat needs.

2. Method in which according to claim 1 the turbine exhaust gases are used decentralised as oxidiser locally in specially designed individually controllable burners of small to medium nominal output of say up to 500kW maximum each, to cover locally distributed heat needs

3. Method in which according to claim 1 the turbine exhaust gases are used decentralised alone or enriched with a mixture consisted of air and/or oxygen of various temperature levels and of various oxygen levels to achieve the various temperature levels needed locally by the process.