GB2075159A

GB2075159A - Shell boilers

Info

Publication number: GB2075159A
Application number: GB8014230A
Authority: GB
Original assignee: Vosper Thornycroft UK Ltd
Current assignee: Vosper Thornycroft UK Ltd
Priority date: 1980-04-30
Filing date: 1980-04-30
Publication date: 1981-11-11
Also published as: CA1156885A; AU542399B2; NZ196938A; AU6990681A; GB2075159B

Abstract

A horizontal shell boiler has within the shell 3 a horizontal furnace section 1 in which a fluidised bed 2 is situated. At one end the furnace section 1 communicates with a flue gas transfer section connected to flue tubes extending horizontally through the boiler fluid above and around the furnace section 1. The furnace section 1 is divided into two portions by a row of inclined water tubes 4 the portion above the water tubes acting as a flue gas flow passage 5 leading (5) into the flue gas transfer section. The end of the lower portion is closed. Combustion gases leave the fluidised bed 2 in a vertical direction and pass between the inclined water into the passage 5 tubes 4, and then travel horizontally along to the flue gas transfer section and do not have any significant tendency to entrain the material of the fluidised bed (2).

Description

SPECIFICATION Shell boilers This invention relates to a shell boiler and it is an object of this invention to provide an improved shell boiler.

According to this invention, there is provided a shell boiler comprising a shell intended to contain boiler fluid, horizontal furnace section within the shell, flue gas tubes extending horizontally through the shell and disposed above and around the furnace section, a flue gas transfer section at one end of the furnace section for transferring the products of combustion from the furnace section into the said flue gas tubes, and a row of inclined boiler fluid tubes extending across the furnace section and communicating at each end with the space between the furnace section and the shell, the space above the inclined boiler fluid tubes within the furnace section acting as flue gas transfer means and communicating with the flue gas transfer section.

In a shell boiler in accordance with this invention the flue or combustion gases leave the portion of the furnace section below the inclined boiler fluid tubes in a vertical direction and at a low and substantially similar velocity over the entire furnace section. If the combustion gases were constrained to enter the flue gas transfer section at one end of the furnace section by moving horizontally immediately above the level of the fuel, then due to the increased volume of combustion gases moving horizontally as the transfer section is approached a corresponding increase in horizontal velocity would occur.In the case in which the furnace section is designed for fluidised bed combustion, this horizontal velocity could increase to the point where it would cause entrainment of the fluidised bed material in the horizontal direction and cause a substantial amount of bed material to be deposited in the transfer section. The flue gas transfer means has the advantage that the combustion gases leave the burning flue in a vertical direction and enter the flue gas transfer means where they move horizontally towards the transfer section but the horizontal velocity of the gases within the transfer section has no effect on the vertical velocity of the combustion gases leaving the burning fuel.

Preferably, there are provided further boiler fluid tubes extending at least over a substantial portion of their length in a vertical direction, extending through the furnace section, and communicating at each end with the space between the shell and the furnace section.

The flow of boiler fluid both through the inclined boiler fluid tubes and through the said further boiler fluid tubes is of course convection driven.

The said further boiler fluid tubes must, of course, pass between the inclined boiler fluid tubes and there are preferably provided a plurality of further boiler fluid tubes which extend substantially vertically over most of their lengths between each pair of adjacent inclined boiler fluid tubes.

In one embodiment of this invention, there are provided two rows of inclined boiler fluid tubes inclined in opposite directions to the horizontal.

It may be arranged that the two rows of inclined boiler flue tubes cross each other.

Embodiments of this invention will now be described, by way of example only, with reference to the accompanying drawings, of which Figure 1 is a schematic end elevation of the furnace section of a first horizontal shell boiler in accordance with this invention (in Fig. 1, vertically extending water tubes disposed within the furnace section are omitted for clarity); Figure 2 is an enlarged end elevation of the furnace section of the horizontal shell boiler shown in Fig. 1; Figure 3 is a horizontal sectional elevation on the line A-A of Fig. 2; Figure 4 is a schematic partial end view of the furnace section of a second horizontal shell boiler in accordance with this invention; and Figure 5 is a partial end view of the furnace section of a third horizontal shell boiler in accordance with this invention.

All three horizontal shell boilers shown in the drawings are designed for fluidsed bed combustion.

In Figs. 1 to 3, the horizontal shell boiler has a horizontal furnace section 2 which may be cylindrical or may have an open bottom and in which the fluidised bed 2 is situated.

At one end the shell boiler has a flue gas transfer section (not shown), the function of which is to transfer combustion gases generated in the furnace section 1 to flue tubes extending horizontally through the space between the furnace section 1 and the shell 3 and above and around the furnace section 1.

The furnace section 1 is divided into two spaces or portions, by a row of inclined water tubes 4, the space above which constitutes a flue gas transfer portion 5 and communicates with the flue gas transfer section referred to earlier. The end of the portion 6 of the furnace section 1 below the inclined water tubes 4 is bricked up as indicated at 7 so that all gases leaving the fluidised bed 2 must pass vertically upwards into the flue gas transfer portion 5 where they move horizontally.

Between each pair of adjacent water tubes 4, a plurality of water tubes 8 extend vertically; each water tube 8 is inclined at each end and communicates with the water in the space between the furnace section 1 and the shell 3 but is always at more than 45 to the horizontal. Despite the fact that the inclined water tubes 8 extend between each pair of inclined wate tubes 4, the water tubes nevertheless form a screen extending along the length of the furnace.

It will be appreciated that the flow of boiler water through the water tubes 4 and 8 is convection driven.

Fig. 4 shows a second embodiment having two sets of inclined water tubes 9 and 10 each of which leaves one side of the furnace section 1 and communicates with the space above the furnace section 1 adjacent to its vertical plane of symmetry. The two sets of water tubes 9 and 10 are curved, each being nearly horizontal at its lower end and nearly vertical at its upper end. There are thus defined two flue gas transfer portions 11 and 1 2 which communicate with the flue gas transfer section.

The horizontal shell boiler shown in Fig. 5 is generally similar to that shown in Figs. 1 to 3 except that there are two rows of inclined water tubes which cross each other and are designated by numerals 1 3 and 14. Consequently, the flue gas transfer portion is divided into three sections 15, 16 and 17, all three of which communicate with the flue gas transfer section.

The water tubes 4 and 8 of Figs. 1 to 3, the water tubes 9, 10 and 8 of Fig. 4 and the water tubes 13, 14 and 8 of Fig. 5, all assist in heat transfer from the combustion gases to the boiler water as they all extend through the furnace section 1 and this is of course desirable.

Claims

1. A shell boiler comprising a shell intended to contain boiler fluid, horizontal furnace section within the shell, flue gas tubes extending horizontally through the shell and disposed above and around the furnace section, a flue gas transfer section at one end of the furnace section for transferring the products of combustion from the furnace section into the said flue gas tubes, and a row of inclined boiler fluid tubes extending across the furnace section and communicating at each end with the space between the furnace section and the shell, the space above the inclined boiler fluid tubes within the furnace section acting as flue gas transfer means and communicating with the flue gas transfer section.

2. A shell boiler as claimed in claim 1 which comprises further boiler fluid tubes extending at least over a substantial portion of their length in a vertical direction, extending through the furnace section, and communicat ing at each end with the space between the shell and the furnace section.

3. A shell boiler as claimed in claim 1 or claim 2 wherein the inclined boiler fluid tubes are curved.

4. A shell boiler as claimed in any of claims 1 to 3 wherein there are provided two rows of inclined boiler fluid tubes inclined in opposite directions to the horizontal.

5. A shell boiler as claimed in claim 4 wherein the two rows of inclined boiler flue tubes cross each other.

6. A shell boiler as claimed in any of claims 1 to 5 wherein the furnace section is designed for fluidised bed combustion.

7. A shell boiler substantially as hereinbefore described with reference to the accompanying drawings.

CLAIMS (7 April 1981)

1. A shell boiler comprising a shell intended to contain boiler fluid, a horizontal furnace section within the shell, designed for fluidised bed combustion, flue gas tubes extending horizontally through the shell and disposed above and around the furnace section, a flue gas transfer section at one end of the furnace section for transfering the products of combustion from the furnace section into the said flue gas tubes, and a row of inclined boiler fluid tubes extending across the furnace section and communicating at each end with the space between the furnace section and the shell, the space above the inclined boiler fluid tubes within the furnace section acting as a flue gas transfer means and communicating with the flue gas transfer section.

CLAIMS (21 April 1981) Claim 6 deleted, claim 7 re-numbered (new claim 1, 6).