Float Glass Kiln Structure (3)

Part Two Melting End

(1）Front wall structure

1-kiln roof (crown); 2-crown feet (springer); 3-upper making-up brick;  4-breast wall; 5-tuck stone; 6-lower making-up brick; 7-tank wall; 8-tank bottom; 9-stay 10-stand column;11-springer angle steel; 12-upper iron; 13-joining beam; 14-breast wall plate; 15-lower iron; 16-tank wall against iron; 17-tank wall against weir; 18-column base angle iron; 19-column base bolt; 20-flat steel; 21-sub beam; 22-main girder; 23-kiln column

 1-vertical wall area; 2-under nose area 3-suspender; 4-steel shell; 5-heat exchange door (cooling water)

① arch crown front wall(drawing 1-5)

  This kind frond wall is built on the crown by 2~3 layer of refractory brick, below arch crown front wall, there need add fire wall to prevent flame out and save fuel, protect feeder.Big water bag across feeding pool is loaded fire wall the whole weight, and there is a knife shape brick on the big water bag to prevent flame directly contact with water bag.On the knife shape brick, layered with lath brick.

  For safety reason, this kind front wall’s span usually not more than 7 m.While front crown and fire wall still easy broken and erosion by flame and alkali environment.When fire wall and water bag broken, we can change by hot maintenance, while since front crown broken heavily, we only can do cool maintenance. So this kind structure is gradually be replace by L type hang wall structure in float glass kiln.Plate glass kiln still using this kind front wall.

Common arch crown structure is restricted by span and safety. In order to further increase the melting area, it is necessary to widen the feeding pool and expand the feeding surface. To solve this, L type hang wall appears.

② L type hang wall structure (drawing 1-4)

Float glass furnace widely used L type front hang wall, this wall is suspended alone, company can adjust the distance from hang wall to glass liquid surface by jack machine.This wall contains heat resistance steel and refractory material, its structure’s safe will not affect by width.L-shaped hanging wall’s width can be equal to melting pool, this can meet the design requirements.

L type hang wall can longer the feeding tank, reduce dust flying and enhance the batch’s preheating. L shape hang wall can be divided into two part, straight part and L part. Straight part uses great silica block, nose area uses sintered mullite block and zircon refractory material. Outside the hang wall using ceramic fiber blanket for insulation; water bag is front the nose area whose function is sealing after cooling.

(2)Breast wall structure (drawing 1-3)

Different part in float glass furnace has different erosion situation, to separate the most damage part when hot maintenance, experts made the breast wall, crown and kiln tank as three separate support parts, finally three parts load fall on kiln bottom steel structure.

Breast wall’s weight fall on breast wall plate and lower iron, then stand column, in then end the load fall on kiln bottom steel structure. (see drawing 1-3)

Breast wall design need make sure has enough strength under high temperature, and the tuck-stone is key point.Breast wall’s bottom has tuck stone brick to block flame, prevent it outside and burn the breast wall plate and upper/lower iron. Usually breast wall in meling zone use fused cast AZS 33# block; upper making-up brick using sintered zircon brick with low creep and crack resistance; Breast wall in clarification uses great silica block.

Breast wall’s height depends on fuel types and quality, kiln size, melting rate, heat consumption, heat release, etc.

Theoretically speaking, since we make sure refractory material’s corrosion resistance, breast wall will not become the key point which affect kiln’s service life. While in actual running process, many kiln’s service life shorten due to breast wall tilt inside in melting zone. some kiln release raw material not on time in late period and made the breast wall collapse. Another reason is after tie brick on tank wall, breast wall plate is exposed to flame space which will make the plate deformation, made breast wall tile inside in further.  To reduce or avoid this phenomenon happen, experts improve breast wall design, they cancel the made-up brick, made the crown feet directly contact breast wall, lower breast wall plate height, inclined upper breast wall tile inside; crown brim brick uses three layer zircon brick; melting end tuck stone brick cancel the hook design, this can void breast wall tilt because tuck stone brick broken. And, some float glass kiln replace 50 mm common carbon steel plate with 60 mm silicon spheroidal carbon-cast iron plate, this also improved breast wall tilt.

（3）Crown structure

Crown is used to form flame space with breast wall and front wall, and absorb heat energy released during fuel burning, then re-radiated to glass liquid surface.

Crown’s load fall on tank bottom steel structure through springer angle iron, upper iron and stand column.

Height and features of crown can be shows through span rate. From the thermal point of view, lower crown is good which can re-radiated more heat to glass liquid surface, this can realized by lower breast wall height and crown height, while breast wall height is confined by port mouth, crown structure strength, etc;

The lower of crown, the more thrust force and little heat dissipation; lower crown will increase crown’s horizontal thrust which will enhance crown’s instability. Usually float glass kiln’s crown spam is around 1:8. Depends on melting end’s length, crown can be divided into several sections, usually three section. When build crown, each section crown need has 100-120 mm expansion gap, front and back gable in crown roof also need wider expansion gap.

Crown widely uses high quality silica block(wedge shape), transverse joint built with staggered-joint way, grey joint depends mortar’s requirement, usually 1~2 mm.

Float glass kiln crown spinger usually uses steel material, and air blast cooling. Steel spinger crown’s bevel extension line on both side needs to pass through the center of crown circle, and the formed angle is crown’s  central angle.

Crown’s life span defines whole kiln’s service life. Thermometer hole, pressure hole, other holes, transverse joint, each section crown head and crown brim are weak parts. When kiln running normally, inside kiln is positive pressure, holes in crown roof easy be burnt bigger, and if crown brim contact spinger angle steel not so tightly, it east burn broken by flame. So this parts should used great refractory material, usually use sintered zircon brick.

（4） Structure of tank wall and tank bottom

Kiln tank contains tank wall and bottom, both be built by refractory block.

The whole load of kiln and glass liquid evenly fall on steel structure supported by column. Glass kiln has two type column: concrete and steel. H type or I type main girder is on the column, large float glass kiln usually use 4 pieces main girder,

Installed I shape sub girder on main girder(along the vertical direction of main girder).Laying channel steel on sub girder (along the vertical direction of sub girder), brick pillar built inside channel steel, before laying fire clay block on the kiln bottom, insulation layer should be built first. Also 25 mm thickness zircon corundum ramming mass as protect layer on the fire clay block, finally 75 mm thickness fused cast azs block on the protect layer.

Glass liquid surface temperature usually more than 1450℃,liquid level up and down, so tank wall easy get erosion, especially where tank wall contact glass liquid line. At present, tank wall usually uses fused cast azs 33# block without brick joint, little pollute the glass liquid, and lower the erosion speed, tank wall thickness usually 250 mm.Using hilt shape block (fused cast azs refractory material), we can tie twice refractory brick which enhance kiln service life (more than 10 years).

To be continue