GB2526099A

GB2526099A - Reaction chamber

Info

Publication number: GB2526099A
Application number: GB1408448.7A
Authority: GB
Inventors: Matthias Grundmann; Duncan Bulmer; Edward Charles Baker
Original assignee: EDM ENERGY Ltd
Current assignee: EDM ENERGY Ltd
Priority date: 2014-05-13
Filing date: 2014-05-13
Publication date: 2015-11-18
Also published as: GB201408448D0

Abstract

A combustor 10 is suitable for burning fuel and heating water. At the heart of the combustor 10 is a ceramic-walled combustion chamber 12 where fuel is burned to produce heat. Flames and combustion gases enter a reaction chamber 14 in the direction of Arrow A, and then they pass along pipes 16 of a heat exchanger in which heat is transferred to water 18 which is pumped into and subsequently out of tanks that surround the heat exchanger pipes 16. The cooler combustion gases then enter a twin cyclone separator 20, in which any remaining particulates are removed, before the gases either re-circulate the combustion chamber or are expelled at an exhaust 22.

Description

Reaction Chamber The present invention relates to a reaction chamber for a combustor, and with a combustor incorporating a reaction chamber.

In many combustor designs a restriction is typically constructed in close proximity to the combustion zone for the better mixing of gases and air to promote the final and complete burn out of any available gases in a following expansion section provided, before passing through the finer tubes or plates of the boiler's ho-at exchangers.

It is often said that the three T's of combustion are: Time, Temperature, and Turbulence. In other words, these threc elements must be maximisod for efficient combustion.

In many burners the above conditions are often compromised due to mainly space considerations and cost. The result is to limit the effectiveness of sLaged air and exhaust gas recirculation in combustion for the reduction of nitrous oxide emissions, and increase the likelihood of larger fly ash particulate carry-over and incomplete combustion, especially when running the combustor nearer its designed heat output maximum.

Embodiments of the present invention aim to provide a reaction chamber for a corabustor in which at least some of the above-mentioned drawbacks of the previously considered designs are addressed.

The present invention is defined in the attached independent claims, to which reference should now be made.

Further, preferred features may be found in the sub-claims appended thereto.

According to one aspect of the present invention, there is provided a reaction chamber for receiving combustion gases in a combustor in use, wherein the reaction chamber comprises a flow path for the combustion gases which flow path has an inverted portion configured to cause turbulence in the gas flow.

The reaction chamber may comprise a first body portion through which combustion gases are ar ranged to flow in use, which first portion may comprise an inlet for the combustion gases. The reaction chamber may comprise a second body portion arranged in use to receive combustion gases from the first portion. Preferably the firsb portion is located at least partly within the second portion.

Preferably the second portion comprises a deflector wall arranged in use to direct combustion gases back towards the first portion, and more preferably around an outer wal.] of Lhe first portion to an outlet.

The reaction chamber may comprise at least partly a double heat-exchanger. In a preferred arrangement, a part of the reaction chamber, which part is preferably the second body portion, may be at least partly surrounded by a fluid for heat exchange. The fluid may be held in a fluid jacket and may comprise water in a water jacket.

The first and/or the second portions may be tubular or box-shaped.

The invention also provides a combustor, for burning fuel and heating a fluid, the combustor comprising a combustion chamber for burning the fuel. The combustor may include a reaction chamber according to any statement herein.

The combustor may comprise a split grate, wherein in use a portion of the fuel to be cornbusted resides in a first grate member and a portion of the fuel to be combusted resides in a second grate member.

One of the first and second grate members preferably comprisos a static grate member and the other of the first and second grate members preferably comprises a moving grate member.

!fhe combustor may comprise a cyclone separator. A fan may be provided to draw combustion gases into the cyclone separator.

The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually oxclusive, or mutually inconsistent.

A preferred embodiment of the present invention will now be described. By way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows in schematic sectional view a combustor according to an embodiment of the present invention; and Figure 2 shows a portion of a reaction chamber of the combustor of Figure 1.

Turning to Figure 1, this shows, generally at 10, a combusto.r for burning fuel and heating water. At the heart of the combustor 10 is a ceramic-walled combustion chamber 12 where fuel is burned to produce heat. Flames and combustion gases enter a reaction chamber 14 in the direction of Arrow A, and then they pass along pipes 16 of a heat exchanger in which heat is transferred to water 18 which is pumped into and subsequently out of tanks that surround the heat exchanger pipes 16. The cooler combustion gases then enter a twin cyclone separator 20, in which any remaining particulates are removed, before the gases either re-circulate to the combustion chamber or are expelled at an exhaust 22.

A more detailed description of the combustor and its operation will now be provided.

Fuel (not shown) preferably in the form of chips of wood or other biomass, enters a fuel inlet 24 whore an auger carries it towards the combustion chamber 12. A hinged fuel spreador flap 28 helps to spread the fuel chips onto an upper ramp 30 in the chamber. Some fuel also falls onto a lower ramp 32 so that the fuel is split between the ramps 30 and 32. AIr is drawn in through an air inlet 34 beneath the ramps. The fuel chips on the upper ramp 30 become pushed by newly introduced fuel onto a static grate 36, where most of the combustion takes place. The fuel chips on the lower ramp tall onto a moving grate 38, which -i-s driven slowly as an endless belt by a mechanism that is well known in the art, and which does not require description here.

The reaction chamber 14 receives the combustion gases and flames from the combustion chamber 12 initially in the direction of Arrow A as described above. Once inside the reaction chamber the flow of gases and flames is effectively inverted, before exiting. This is because the geometry of the reaction chamber, which comprises a first tube 14a within a second tube 14b (see Figure 2). The outer tube 14b is closed at its upper end and the gases are forced to turn back and travel downwardly into the annular space outside the inner tube before exiting. The hot gases are then drawn through the heat exchange pipes 16, past turbulators 17 and into the cyclone separator 20, by an induced draft fan 40.

The separator 20 removes fly ash and any remaining particulates that can be collected conveniently together with the ash from the grate 38 at a common ash discharge point 42. The separated exhaust gases, now free from particulates, and may be re-circulated to the combustion chamber or else discharged from exhaust outlet 22 in dependence upon the position of flap 44. The oxygen levels of the exhaust gases can be monitored using a lambda probe (not shown), and this can be used to determine whether to recirculate the exhausb gases or to expel them and draw in fresh air from the surroundings.

The design of the combustion reaction chamber 14 ensures and maxirnises the residence time, temperature and turbulence of the combustion gases and flames in a limited space by effectively inverting the incoming flames and any unburned gases. Furthermore, they become physically enveloped within the fully burnt out, and hottest, gases exiting the reaction chamber.

This design not only reduces gas emissions and the potential for tarry deposits, it fully utilizes the expansion chamber optimising its heat exchange surface area and also ensures particulate fly ash is further reduced and remains airborne without settling and fouling the down-stream heat exchanger pipes 16. This further increases efficiency and reliability and reduces the maintenance requirements of the boiler.

Turning to Figure 2, this shows schematically a portion of the reaction chamber 14 and the arrows indicate the direction of flow of the hot gases and flames. This drawing shows the water surrounding the outer tube 14b in the manner of an annular water jacket 14c. Since the water in the wator jacket l4c has hot gases on both sides, the apparatus effectively acts as a double sided heat cxchanger, in which the transfer of heat energy from the gases to the water is optimised.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should he understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A reaction chamber for receiving combustion gases in a combustor in use, wherein the reaction chamber comprises a flow path for the combustion gases which flow path has an inverted portion configured to cause turbulence in the gas flow.
2. A reaction chamber according to Claim 1, wherein the reaction chamber comprises a first body portion through which combustion gases are arranged to flow in use, which first portion may comprise an inlet for the combustion gases.
3. A reaction chamber according to Claim 2, comprising a second body portion arranged iii use to receive combustion gases from the firsL porLiori.
4. A reaction chamber according to Claim 2 and 3, wherein the first portion is located at least partly within the second portion.
5. A reaction chamber according to Claim 3, wherein the second portion comprises a deflector wall arranged in use to direct combustion gases back towards the first portion.
6. A reaction chamber according to any of the preceding claims, comprising at least partly a double heat-exchanger.
7. A reaction chamber according to Claim 6, wherein a part of the reaction chamber is at least partly surrounded by a fluid for heat exchange.
8. A combustor, for burning fuel and heating a fluid, the combustor comprising a combustion chamber for burning the fuel and a reaction chamber according to any of the preceding claims.
9. A cornbustor according to Claim 8 comprising a split grate, wherein in use a portion of the fuel to be combusted resides in a first grate member and a portion of the fuel to be coinbusted resides in a second grate member.

1O.A cornbustor according to Claim 9, wherein one of the first and second grate members comprises a static grate member and the oLhor of the first and second grate members comprises a moving grate member.