GB2271171A

GB2271171A - Boilers and steam boilers

Info

Publication number: GB2271171A
Application number: GB9220852A
Authority: GB
Inventors: Roger Arthur Briggs
Original assignee: EDGE CHRISTOPHER WILSON FREEGA
Current assignee: EDGE CHRISTOPHER WILSON FREEGA
Priority date: 1992-10-03
Filing date: 1992-10-03
Publication date: 1994-04-06
Anticipated expiration: 2012-10-03
Also published as: GB2271171B; GB9220852D0

Abstract

A combined waste heat and fired boiler or steam boiler comprises a combustion chamber having a burner, a plurality of banks of fire tubes extending through a shell, and headers for leading flow of combustion products from the combustion chamber through each of the banks of tubes in series, wherein by opening and closing dampers waste process gas or exhaust gas from a gas turbine may flow through all of the banks of tubes in parallel. <IMAGE>

Description

BOILER? This invention relates to boilers It is known to use waste heat from hot process gases or the exhaust from an engine as the heat source for a hot water or steam boiler. In many instances a back-up system is required for the occasions when the hot gases are not available for any reason. A fuel- fired boiler is normally provided. The two boilers are necessarily of dissimilar type because of the different flame and gas temperatures. Thus the back-up boiler burner may have a flame temperature of the order of 20000C. whereas the process or exhaust gases may be much lower, e.g. between 450 and 10000C and typically about 6000C.So the one boiler may be a single pass boiler in which the temperature falls from the mentioned 6000C to about 2000C when it reaches the flue, whereas the other will be a multi-pass system in which the temperature falls progressively in successive passes in opposite directions through the boiler to reach the same low point.

The object of the invention is to simplify such installations According to the invention a boiler comprises a shell to contain water and/or steam, a combustion chamber provided with a burner, a plurality of banks of fire tubes extending through the shell, and header chambers at each end for transferring gases for flow from the combustion chamber through each of the banks in series.

and is characterised by the provision of means for introducing hot gases from an alternative source to flow through all of the banks in parallel.

Hence, multi--pass or single--pass flow is possible in one and the same boiler, so that a waste heat boiler can be provided with a fuel-fired back-up in one and the same water filled shell.

In one presently preferred embodiment of the invention, the boiler is, in its fuel fired operating mode, a triple-pass boiler. However, other possibilities are feasible within the scope of the invention.

The boiler of the embodiment has a cylindrical water filled (and/or steam) shell with a generally cylindrical but smaller diameter combustion chamber eccentrically located in the lower portion of the shell so as to be completely water-jacketed. The boiler may be dry back or wet back, that is the end of the combustion chamber may be the end wall of the boiler or inset therefrom.

A refractory plug closes a port extending through the end wall of the boiler from the rear transfer (or main transfer) chamber, for cleansing and like purposes.

Two banks of fire tubes extend through the shell about the combustion chamber.

The combustion chamber has the fuel-fired burner at the front end.

A main and first transfer chamber extends radially from the combustion chamber at the back end, and the first one of the banks of tubes opens from this transfer chamber and extends to the front end of the boiler.

Further and secondary transfer chambers extend across the front end to connect the tubes of the first bank to those of the second bank. The tubes of the second bank extend to the back wall and open into a main flue header The construction so far described is for use as a fuel fired backup boiler and is substantially conventional.

The said further and secondary transfer chambers at the front end, which may be a single further secondary chamber, have a port or ports for connection to the process gas or engine exhaust e.g. a gas turbine. When in use in this mode, said port or ports are open and gas turbine exhaust gas flows in the same direction through both banks of tubes. When not in use a damper blanks off the port or ports so that fuel burner gases do not reach the gas turbine At the back end. the said refractory plug is disposed in an auxiliary flue header connected to a separate or the main flue header, and arranged so that the plug may be withdrawn from its normal operative position to a second position, and thus open a route for gas flow via the tubes of the first bank, via the main transfer chamber, and the auxiliary flue header to reach the flue. When in the waste heat or turbine fired mode the fuel fired burner may be isolated or protected from gas turbine or process gases.

In a modification. the refractory plug can be removed and a shut off damper arrangement incorporated into the auxiliary heater as shown in the accompanying informal drawing In some constructions according to the invention, the auxiliary header may have to be connected to a separate chimney liner to maintain acceptable chimney efflux velocities.

Claims

1. A boiler comprising a shell to contain water and/or steam, a combustion chamber provided with a burner, a plurality of banks of fire tubes extending through the shell, and header chambers at each end for transferring gases for flow from the combustion chamber through each of the banks in series, characterised by the provision of means for introducing hot gases from an alternative source to flow through all of the banks in parallel.

2. A boiler as claimed in Claim 1 wherein the combustion chamber extends through the shell between a burner at the front end and a header at the back end and the header is connected to a chimney, and in which a refractory plug is movable between two positions, in one of which gas flow from the chamber to the header is possible and in the other of which it is not possible.

3. A boiler as claimed in Claim 1 wherein a transfer chamber is provided at the front end, two banks of fire tubes extend through the shell and open to said chamber, and a port in said chamber connects to the alternative source.

4. A boiler as claimed in Claim 2 wherein a damper is provided to open and close the flow path in the header at the back end.

5. A boiler as claimed in Claim 3 wherein a damper is provided to open and close the port.

6. A boiler substantially as described with reference to the accompanying drawing.