GB2026673A

GB2026673A - Regenerator Chequer Brick Construction

Info

Publication number: GB2026673A
Application number: GB7831147A
Authority: GB
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1978-07-26
Filing date: 1978-07-26
Publication date: 1980-02-06
Also published as: GB2026673B

Abstract

A coke oven regenerator chequer brick of cuboid form penetrated by two sets of upright slots 21 separated by a centrally extending, apertured, web 22, the side faces 12, 14 and the upright slots being formed with wavelike corrugations of 3-5 m.m. arc radius and the front and rear faces 15, 13 being formed of alternate straight and concave arc section corrugations. Flats, standing proud of the corrugations, are provided adjacent arises between the front, side and rear faces and centrally of the side faces and three lugs or rises 18, 19 are provided on the bottom face for spacing purposes. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Heat Exchangers and Chequer Brick Components Thereof This invention relates to heat exchangers such as coke oven batteries and, more particularly, to regenerators-and the construction thereof-in which waste gases produced by combustion are used to preheat fuel gas mixture and/or air before discharge to combustion chambers.

In known coke oven regenerators, chequer bricks, manufactured from a refractory material, are used to alternately absorb and radiate heat.

The hot waste gases from combustion chambers of a coke oven are channelled into the regenerator and over, through plane sided slots, and around conventional chequer brick contained therein.

These hot waste gases heat up the chequer bricks. After a pre-determined time the flow of hot gases is re-channelled into a companion regenerator, which has been on a cooling portion of the cycle. In coke oven batteries heated with a fuel gas mixture of low calorific value, the fuel gas mixture, which is burned in the coke oven to provide heat for the coking process, is made up of air and lean gas. At a pre-determined time, the lean gas is channelled through one quarter of the overall regenerator or one half of a waste gas preheated regenerator. Air is channelled through the remainder of the preheater regenerator. Hot waste gases are concurrently conducted through the remaining half of the overall regenerator, which has been previously cooled by earlier passage of lean gas and air.The lean gas and air are preheated by being channelled across the preheated bricks, resulting in a higher combustion temperature per given volume of the fuel gas mixture. In coke oven batteries heated with a fuel gas mixture of high calorific value, using a rich gas, the combustion air used to burn the fuel is not channelled across the preheated chequer bricks, but the air is preheated to a lesser degree outside of the regenerator. The higher temperature per given volume of fuel gas mixture allows less fuel to be used to maintain a temperature within the coke oven sufficient to produce coking of coal, thus enhancing economy of operation.The efficiency of a coke oven regenerator depends on the ability of the chequer brick to transfer heat while at the same time minimizing the degree of restriction of flow of the various gases, including waste gas, air or fuel gas, which move through the regenerator.

According to the present invention there is provided a chequer brick for a heat exchanger, the brick being of cuboid form having planar top and bottom faces and side, front and rear faces formed with upright corrugations and penetrated by a plurality of upright slots extending between the top face and the bottom face with faces of the slots being formed with upright corrugations.

The invention also includes a coke oven battery having a heat exchanger, or regenerator, constructed with such chequer bricks.

The invention will now be described, by way of example, with reference to the accompanying, partly diagrammatic drawings in which Figure 1 is a plan view of a chequer brick; Figure 2 is a side elevation of a chequer brick; and Figure 3 is an isometric projection of a chequer brick together with portions of adjacent chequer bricks positioned as in a coke oven regenerator.

Referring to the drawings, there is shown a coke oven regenerator chequer brick 11 of conventional dimensions and overall cubic shape.

The chequer brick 11 has six faces, namely, a right face 12, a rear face 13, a left face 14, a front face 15, a top 1 6 and a bottom 1 7. The bottom 17 includes a pair of front lugs or risers 1 8 positioned adjacent to the corners made by the front face 1 5 with the right face 12 and the left face 14 and a rear lug or riser 19 is positioned centrally of the rear face 13. The three risers 18 and 19 serve to space, without rocking, the chequer brick 11 from a subjacent chequer brick (not shown) in a regenerator to provide equalization of gas flow pressure within the regenerator.Faces 12 and 14 of the chequer brick 11 are formed each of two sets of a corrugation configuration 20, recessed from the outer planes of the faces, having alternate convex and concave 1800 arcs, in a wave-like pattern as illustrated in the drawings. The radius of each arc is between approximately 3 m.m. (1/8 of an inch), the minimum threshold level below which there is found to be a significantly increased tendency for the corrugations to clog with exhaust gas particulate matter, and 5 m.m. (3/16 of an inch) beyond which the concave arcs would be spaced too far from the surface plane increasing constriction and turbulence in the gas flow.

The chequer brick 11 contains two sets of slotted apertures 21, each set nominally containing four slotted apertures, although this number may change depending on the overall dimension of a given chequer brick, together with a cross-aperture 22. By providing two sets of slotted apertures 21, as illustrated in Figure 1, rather than four long slotted apertures in the chequer brick, manufacture of the chequer brick by the re-press method is facilitated. Each of the walls 23 of the apertures are formed with the corrugation configuration 20 aligned "in phase" across the apertures and, for the sets of apertures 21, across the intervening walls and to the faces 12, 14 to give approximately constant distances between corresponding points over the apertures and over the walls.In a similar manner the faces 12 and 14 have two sets of corrugation configuration 20, rather than a single section extending over the face to produce an approximately constant thickness of the refractory material 24 throughout the brick. The crossaperture 22 serves to form a convenient separator between the two sets of slotted apertures 21 while producing additional means for gas flow.

The overall combined crosssectional flow area of the slotted apertures 21 and the cross aperture 22 is equivalent to the cross-sectional flow area of passages found in a conventional chequer brick. However, the surface area of the walls 23 of the apertures is approximately 50% greater in total than that found in conventional chequer brick having straight sided passages and of the same overall size.

The rear face 13 and the front face 1 5 have a different corrugation shape 25 from the corrugation configuration 20. The corrugation shape 25 is in the form of alternate straight sections and modified concave arcs registering with the apertures 21 and material therebetween, as illustrated in the drawings and serves to channel the gas flow through the apertures formed by the abutment of the front face 1 5 of one chequer brick with the rear face 13 of an adjoining chequer brick, away from the risers 1 8 and 1 9 thereby normalizing the turbulence created by the flow of gas past those risers 1 8 and 1 9. The rear riser 1 9 forms a continuation of the corrugation shape 25 so that there is no abrupt change in the flow pattern of the gases as the gases pass the rear riser 1 9.

The chequer bricks 11 are laid up in a coke oven regeneratòr in horozontal layers. Starting along the side edge of the regenerator, a row of chequer brick is placed, each with its front face 1 5 abutting the side of the regenerator, with the left face 14 of each chequer brick 11 abutting the right face 12 of the next chequer brick 11 in line forming an aperture similar in shape to the slotted apertures 21. A second row of chequer brick 11 is then placed with the front faces adjoining the rear faces of the first row, with successive rows following until a first layer of chequer brick is in place. An additional three layers are laid up, duplicating the positioning and placement of the chequer brick in the first layer.A fifth layer of chequer brick 11 is laid with the courses transversely of the the courses of the first four layers to stabilize the lay-up and thereby avoid the need for a retaining brick heretofore required for stabilization. By virtue of the arrangement of the slotted apertures 21 in the individual chequer brick 11 heated gases may flow freely to the fifth transverse course of chequer brick 11, thus avoiding undesirable pressure differentials within the coke oven regenerator.

In operation, waste gases are directed downwardly through the apertures 21 and 22 in the chequer brick 11 and through the apertures formed intermediate abutting bricks, heating the brick through the surface walls. The smooth faced corrugation configuration 20 avoids sharp projections which would otherwise tend to create turbulence in gas flow. The radii of the corrugation configuration 20 are such as to avoid entrapment of particulate matter found in the waste gases.The brick 11 being of approximately the same mass as a conventional chequer brick of the same material retains the same amount of heat after exposure to the waste gas; however, due to the approximately 50% greater surface area of the aperture walls 23, compared with planar walls heat is transferred from the waste gas to the chequer brick 11 at a significantly faster rate enabling the brick to achieve a requisite temperature in a shorter period of time than is achieved with a conventional chequer brick. This allows a rechannelling of the exhaust gases in a shorter period of time; or, alternatively, in the same period of time, the chequer brick 11 may be heated to a higher temperature than obtained with a conventional chequer brick, thus providing a greater potential heat exchange resulting in thermal efficiency.Since more heat is absorbed from the waste gases, the waste gases leave the bottom of the regenerator at a lower temperature compared with a regenerator of the same mass of conventional chequer bricks.

At the end of the heating period, the hot waste gases are rechannelled to the top of a companion regenerator and fuel gas mixture (or air) is introduced into the bottom of the regenerator chamber, directed upward through all the apertures and the heat retained by the chequer brick 11 is transferred to the fuel gas or air. Due to the increased capacity for heat transfer, a given volume of fuel gas or air may be heated to a requisite degree in a shorter period of time.

Therefore the flow rate of fuel gas through the regenerator may be increased providing an increased volume of preheated gas at the requisite temperature available for combustion per unit of time. Thus the size of the regenerator may be decreased or heat input to the coke ovens may be increased for a given size of regenerator or the average temperature within the regenerator may be increased by raising the lower threshold temperature at which the cycle is changed over from fuel gas to exhaust gas in order to maintain adequate combustion so that less fuel gas per unit of time is required.

It will be appreciated that the chequer brick 11 may be readily formed by a "repress" process in which viscous refractory material is extruded through a die press to form a slug. The slug is then re-pressed into a mold and ejected in the form desired. This refractory form is then dried and placed directly into a kiln to be cured.

It will also be appreciated that the chequer brick may be utilised in heat exchangers, or regenerators, for use in conjunction with piant other than coke ovens, such as blast furnaces and boilers.

Claims

1. A chequer brick for a heat exchanger, the brick being of cuboid form having planar top and bottom faces and side, front and rear faces formed with upright corrugations and penetrated by a plurality of upright slots extending between the top face and the bottom face with faces of the slots being formed with upright corrugations.

2. A chequer brick as claimed in Claim 1, wherein the upright slots are of elongate crosssection with walls of greater dimension extending substantially parallel to the side walls and the upright corrugations in the side walls and corresponding walls of the upright slots are of wave-like pattern and are aligned in phase to give approximately constant distances between corresponding points over the apertures and over the walls.

3. A chequer brick as claimed in Claim 1 or Claim 2, wherein the upright corrugations in the side walls and walls of the upright slots are of wave-like pattern having alternate convex and concave arcs or radius from 3 to 5 millimetres.

4. A chequer brick as claimed in any preceding claim,çwherein the upright corrugations in the front and rear faces are in the form of alternate straight sections and modified concave arcs respectively registering with the upright slots and the material between the upright slots.

5. A chequer brick as claimed in preceding claim wherein portions of external wall faces adjacent arrises between the front, side and rear faces are of planar form and stand proud of the upright corrugations in the front, side and rear faces.

6. A chequer brick as claimed in any preceding claim, wherein the upright slots are arranged as two sets respectively adjacent the front and rear faces and separated by a centrally extending apertured, web.

7. A chequer brick as claimed in Claim 6, wherein portions of external wall faces of the side walls adjacent the centrally extending, apertured, web are of planar form and stand proud of the upright corrugations in the side faces.

8. A chequer brick as claimed in any preceding claim, wherein the bottom face is provided with a pair of front lugs or risers positioned adjacent corners adjoining the front and side faces and a rear lug or riser positioned centrally adjacent the rear face.

9. A chequer brick arranged and constructed substantially as hereinbefore described with reference to the accompanying drawings.

10. A coke oven battery having a heat exchanger, or regnerator, constructed with chequer bricks as claimed in any preceding claim.