1. Technique summery

Blast furnace is a kind of melting equipment that stays in high temperature for a long time continuously. In the long-term operation, the inside lining can be eroded, peeled off or damaged easily, which affects the normal operation of furnace deeply. In order to achieve great longevity and high efficiency for furnace, prolonging the life of furnace has been a great concern for melting engineers. Furnace’s longevity is one of the indicators for melting technology. Currently, in China, people widely use remote control hot spraying to repair lining, that is, repairing the lining during the blowing down period while the furnace is still working. Traditionally, the furnace is shut down during repairing. Compared to traditional one, this technique brings more convenience for running the furnace, consume less time and can put into operation faster. But the technique employs dry spraying method, the following drawbacks are unavoidable:　bad durability, bad uniformity of spraying coating( water is added onto the spray gun head, water and related materials can not be mixed evenly), too much dust etc. To solve the problem, our company tested and developed wet spraying technique to make lining, combining the most advanced wet spraying technique and remote control hot spraying method. This technique combines wet spraying machine and remote control spraying manipulator, so that inside lining can be made by remote control hot spraying. Its lining making effect can as good as that of formwork casting.

2. Use

RCGN wet spraying castables--- used on the upper and middle part of furnace’s stack during hot spraying repair.

RCGN wet spraying castables --- used on the under- part of furnace’s stack during hot spraying repair.

3. Technique characteristic

Compared to dry spraying coating:

With enough mixing time, water saving dispersant can be made the best use.

Less water added, the strength and abrasive resistance would improve.

Water and related materials would not be separated and the spraying coating would be more well-distributed and intense.

Rebound degree would be reduced obviously and rebounding of large particles will not exist and particle size would remain as designed.

Comparison of Technical indices for difference materials

4. Brief introduction of execution of works

4.1 Preparation for spraying

4.1.1 Relevant personnels and equipments enter into the field one day in advance. Safety personnel from Party A conduct safety education and make it clear how to identify hazards. Technological personnel from Part A pass on technological details and make sure the equipments installed and run properly.

4.1.2 Party A lowers the stockline to the lower edge of tuyere. After loading slag mulch, spray light damping-down mulch into furnace from various tuyeres and angles as to block the coal gas , hold back ignition point and accelerate temperature dropping. Hydraulic station should be water-cooled forcibly and hydraulic pipes and spraying manipulator should be wind-cooled forcibly so that the temperature in the furnace is lower than 300℃.

4.2 Spraying

4.2.1 cleaning with high pressure water

Our company clean the chamber wall and cooling wall with 400kg high pressure water. There are only two high pressure equipments of this kind. In this way, te clinker, oil stain, the attachments in the groove can be got rid of thoroughly, so that the spraying coating can be stuck onto the cooling wall tightly.

4.2.2 Spraying

Start the equipment, pour the materials into the continuous mixer connected with spraying machine , add water mixing continuously; Put the materials mixed into the spraying maching which is carried into the remote rotating spray gun. Adjust the metering pump of accelerating agent appropriately so that the castables sprayed would not spread out excessively after repairing. Adjust the rotation speed and rotation direction of remote spray manipulator to make the thickness of spraying coating well-proportioned and appropriate. Through telecontrolling four electric hoists, spray evenly from bottom relying on positioning rule until the repair is over. The spraying work is done after on-site inspection by supervisor from Party A.

4.3 Evacuation

Clean up and spraying equipments would be moved out through cast house and furnace house platforms.

5.Baker and furnace running

5.1 baker

After coating spray, rake out the residue through tuyere cooler. Reinstall the tuyere. Blow hot air into the furnace which would be dispersed via exhaust stack. Bake 48 hours under close monitoring to get rid of the water from coating spraying. Without baking, the coating would be peeled off and that would affect the its life and proper operation of furnace greatly.

5.2 Equiblasting and starting furnace

The wind is carried on through tap hole with a wind pipe that is connected with the blast pipe from the air heating furnace (as shows in Diagram 1). This can ensure good connection between tap hole and tuyere, which helps keep the melten iorn and slag liquid at the tap hole. That would help the furnace work properly. Equiblasting operating process is as follows: Cut a hole on tap hole part with a drill. The hole cut must match the blast pipe. Connect the main branch hot air pipe above, which sends the hot air into tap hole(not tuyere). Keep the section valves in the furnace closed and all tuyeres open; Keep blowing through tap hole for eight hours, open the section valves sending the hot air into furnace, after that, take out all hot air pipes from tap hole. That is all for the euiblasting and starting furnace process.

By equiblasing in this way, the output would improve obviously after running the furnace for four day.

Diagram 1 Sending hot air into furnace