WO2011131834A1

WO2011131834A1 - Steam generator

Info

Publication number: WO2011131834A1
Application number: PCT/FI2011/050346
Authority: WO
Inventors: Taisto MÄKIVIRTA
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-04-20
Filing date: 2011-04-18
Publication date: 2011-10-27
Anticipated expiration: 2012-10-20
Also published as: FI20105419A7; FI20105419A0; FI20105419L

Abstract

The invention relates to a steam generator including a combustion chamber (2) delimited by a metal jacket (1) and having fuel supply means (3) in order to supply and burn fuel in the combustion chamber, combustion air supply means (4) in order to supply combustion air to the combustion chamber, and an exhaust gas duct (5) in order to lead exhaust gases out of the combustion chamber. According to the invention, in the combustion chamber (2), in the area of the hottest combustion and exhaust gases, there is a steam chamber (6) to which a water supply duct (7) and a steam duct (8) leading out of the steam chamber are led through the exhaust gas duct (5). In addition, the combustion chamber (2) is formed by at least a two-jacket (1, 9) structure in such a way that the air cooling the structure is arranged to circulate between the jackets (1, 9).

Description

STEAM GENERATOR

FIELD OF THE INVENTION

The invention relates to a steam generator as defined in the preamble of claim 1.

BACKGROUND OF THE INVENTION

Conventionally, large steam boilers in power stations are structures having a height on the order of 20 to 30 m wherein fuel, such as gas, liquid or solid fuel, is burnt within a water-cooled jacket. The water under pressure that has been heated in the jacket is led to a steam header where it evaporates. The steam is led to one or more superheaters disposed in the hottest areas of the boiler in order to raise the temperature of the steam before leading it to a turbine or other applications. The known structures are functional but large and expensive to build and maintain. The multi- step heating, evaporation and superheating of water requires many different components, heat exchangers, pipes, welding and installation work, etc.

OBJECTIVE OF THE INVENTION

It is an objective of the invention to eliminate the drawbacks of the prior art referred to above. In particular, it is an objective of the invention to provide a structurally and operationally new type of a steam boiler by which the production of steam is made more energy-efficient and the apparatuses to be used are smaller, lighter and thereby less expensive to build and maintain.

SUMMARY OF THE INVENTION The steam generator according to the invention includes a combustion chamber delimited by a metal jacket and having fuel supply means in order to supply and burn fuel in the combustion chamber, combustion air supply means in order to supply combustion air to the combustion chamber, and an exhaust gas duct in order to lead exhaust gases out of the combustion chamber. According to the invention, in the combustion chamber, in the area of the hottest combustion and exhaust gas- es, there is a steam chamber to which a water supply duct and a steam duct leading out of the steam chamber are led via the exhaust gas duct. Thus, no separate container where the water would be evaporated and thereafter separately superheated in superheaters is needed in the structure according to the invention, but instead the water may be led cold, hot or evaporated, according to need, to the steam chamber disposed within the combustion chamber where it is finally evaporated and superheated, reaching the pressure and temperature required by the final application.

Another essential feature in the invention is the use of high temperatures, permitted because the combustion chamber consists of at least a two-layer structure, wherein air, and not water as conventionally, is circulated as a cooling agent between an interior jacket and an exterior jacket. This provides for high temperatures and clean combustion in the combustion chamber. The air that cools down the structure and circulates between the jackets can be led partially or completely as primary combustion air, secondary combustion air and tertiary combustion air, according to need, to the combustion process taking place in the combustion chamber. Heat can also be drawn by suitable heat ex- changers from the hot air between the jackets for different kinds of thermal needs. Furthermore, because the air is free from exhaust gases and clean, it. can be led to any application where heat is needed. Around the combustion chamber there may also be several metal jackets with separate air circulations. This way, low- er-temperature air for applications that require lower heating is obtained from the outer air cooling circulations .

The structure according to the invention provides for extremely high temperatures on the order of 900°C in the steam chamber and the surrounding structures. Therefore, the steam chamber is preferably provided on support in the combustion chamber only by the exhaust duct. As the exhaust duct is formed by a pipe leading directly up from the middle of the combustion chamber, the steam chamber may for example hang in the combustion chamber only by support of the steam duct starting from the combustion chamber so as to extend up from the combustion chamber along the exhaust duct. Of course, other suspension means may be used as well in the exhaust duct to suspend the steam chamber in its place .

Preferably, the water supply duct is also led to the steam chamber through the exhaust duct either within the steam duct or along with it.

Preferably, the steam chamber to be used in the invention is a substantially round container. It may be a sphere or other closed structure mostly consisting of curved surfaces. This way, it is made better to withstand extremely hot temperatures and high pressures.

The steam generator according to the invention provides considerable advantages as compared with the prior art. The structure is simple and small as com- pared with the prior art. For example, the height of the steam boiler according to the invention is approximately 10 meters, whereas the height of a conventional steam boiler having the same efficiency is approxi- mately 20 to 25 meters. The invention provides for simple and quick control over generation of the steam, because the water and steam flow paths are short and cooling is effected by clean air, the amount of which can be varied freely and quickly according to need. Furthermore, the quick and easy controls are permitted by a structure where the hot combustion chamber and even hotter steam chamber are completely separate from each other, i.e. the steam chamber hangs within the combustion chamber. This way, even large-range and quick temperature variations in the cooling air flows of the combustion chamber jacket or in the amounts or temperatures of the water to be supplied to the steam chamber do not impose on the structures or connecting structures therebetween stress caused by thermal ex- pansion that would damage the structures.

LIST OF FIGURES

In the following section, the invention will be described in detail with reference to the accompanying drawing which schematically represents one steam generator according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The steam generator schematically represented in the figure includes a combustion chamber 2 delimited from the inside by a metallic interior jacket 1. Outside the interior jacket there are also a metallic intermediate jacket 14 and thereoutside an exterior jacket 9. This way, the walls of the combustion chamber include two air ducts between the jackets by which the structure is cooled down and the air circulating therein is heated up. The bottom part of the combustion chamber includes fuel supply means 3 to supply gaseous, liquid or solid fuels to the combustion chamber. Of course, the combustion of certain fuels requires grate struc- tures or the like, which have not, however, been depicted in the schematic figure.

Naturally, the combustion chamber also has combustion air supply means 4 to supply primary combustion air 10, secondary combustion air 11 and tertiary combustion air 12 to the combustion process in a controlled manner and according to need. The tertiary combustion air nozzles 12 may also be provided with the possibility to lead water or steam therethrough to the hottest area of the combustion chamber found around the steam chamber. This way, the temperature of the steam chamber can be lowered quickly and efficiently according to need.

The combustion chamber 2 preferably having a circular horizontal cross section narrows in the upwards direction, tapering into an upwardly rising straight exhaust gas duct 5. In the middle of the top part of the combustion chamber 2 there is a spherical closed steam chamber 6 opening only into a steam duct 8 that sepa- rates upwards therefrom. Furthermore, the steam chamber 6 is secured only to the steam duct 8, i.e. it hangs thereby in the combustion chamber 2.

A water supply duct 7 is led into the steam duct 8 outside the combustion chamber 2, extending down in the steam duct and ending within the steam chamber 6 at nozzles 15. Water is supplied to the water supply duct 7 by a high-pressure pump 13 by which the pressure of water and steam to be generated therealong can be controlled to be at all times suitable for the current need. If the required steam is low-pressure, i.e. the normal water supply pressure of the water source is sufficient, the high-pressure pump 13 can be skipped by a bypass 16. Also connected to the water supply duct 7 is a three-way valve 17 and a heating circulation 18 coupled thereto with a heat exchanger 19 disposed in the space between the interior jacket 1 and the intermediate jacket 14. This way, water to be supplied to the steam chamber 6 can be preheated according to need and, therefore, it is possible to supply to the steam chamber either cold water, heated water or steam, which is then superheated in the steam chamber .

The invention is not limited merely to the examples referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims .

Claims

1. A steam generator including a combustion chamber (2) delimited by a metal jacket (1) and having fuel supply means (3) in order to supply and burn fuel in the combustion chamber, combustion air supply means (4) in order to supply combustion air to the combustion chamber, and an exhaust gas duct (5) in order to lead exhaust gases out of the combustion chamber, characterized in that within the combustion chamber (2), in the area of the hottest combustion and exhaust gases, there is a steam chamber (6) to which a water supply duct (7) and a steam duct (8) leading out of the steam chamber are led through the exhaust gas duct (5) and that the combustion chamber (2) is formed by at least a two-jacket (1,9) structure in such a way that the air cooling the structure is arranged to circulate between the jackets (1,9).

2. The steam generator according to claim 1, characterized in that the steam chamber (6) is provided on support in the combustion chamber (2) only by the exhaust gas duct (5) .

3. The steam generator according to claim 1 or 2, characterized in that the exhaust gas duct (5) is formed by a pipe leading directly up from the middle of the combustion chamber (2) .

4. The steam generator according to any one of claims 1 to 3, characterized in that the air cooling the structure is led to the combustion air supply means (4) in order to use preheated primary, secondary and/or tertiary combustion air (10,11,12).

5. The steam generator according to any one of claims 1 to 4, characteri zed in that the water supply duct (7) is led to the steam chamber (6) within the steam duct ( 8 ) .

6. The steam generator according to any one of claims 1 to 5, characteri zed in that the water supply duct (7) includes a high-pressure pump (13) in order to supply pressurized water to the steam chamber (6).

7. The steam generator according to any one of claims 1 to 6, characteri zed in that the steam chamber (6) is a substantially round container.