DEMECH has been supplying Submerged Scraper Conveyors (SSC) since 1990 and has a technical collaboration with Hitachi Power Europe, Germany to manufacture SSCs of large size which are required for the bigger boilers.
SSCs provides an ideal solution for handling hot bottom ash from coal fired boilers and hot kiln dust from steel plants. These materials which are in red hot condition when discharged are difficult to safely handle by any other means than SSC. DEMECH SSCs require less water and less headroom below the furnace. The hot Economizer Ash and the Pyrite rejects (coal mill rejects) can also be discharged to the SSC installed for handling bottom ash, which in turn saves the necessity of a separate system for these materials.
- SSC is a double strand chain conveyor for handling high temperature materials, which drops in the water which the conveyor is filled with. The chain strands are submerged in water and moves at very low linear speed of about 0.03 m/s and scraps out the material from the water.
- There can be two variants in SSC depending on top or bottom chain action as the material conveying member. In the first one where the top chain conveys the material, has the return inactive chain outside the water filled chamber. The other variant where the bottom chain does the conveying activity has both the chain paths submerged in water.
- DEMECH SSCs are custom designed to suit the bulk material to be handled. For SSC, it is the material properties which decide whether the conveying will be with ‘En-masse’ effect or ‘Drag’ effect. DEMECH’s vast experience in this field ensures that the conveyor is designed to operate at optimum efficiency by proper selection of speed, type of chain and flight.
- The conveyors are designed with single or multiple numbers of inlet and discharge openings provided at the required locations along the conveyor path.
- The conveyors are manufactured according to application using Carbon Steel, Stainless Steel or other such material with various types of lining.
- DEMECH chains are made of alloy steel drop forgings. They are machined and heat treated to achieve desired strength and hard outer surface to withstand wear due to abrasion.
- Sprockets suitable for the forged chains are also manufactured by DEMECH in Carbon Steel and Alloy Carbon Steel which are case hardened for longer life.
- Flights of different shapes and construction are welded or bolted to the chain links as per following drawings
- The surface over which the chain scraps off the material is lined with hard material like Cast Basalt tiles or plates of 400 BHN hardness. The chains are either forged round link chains or drop forged machined chains.
- A major part of SSC is the cooling water system. The water is maintained at a constant level in the conveyor chamber which is also used to air lock the furnace internals against atmospheric pressure by dipping the inlet in this water. The quantity of flow of cooling water to the conveyor is calculated based on the temperatures and flow rate of the material. The excess water is allowed to overflow from the conveyor through simple trap separator or a parallel plate separator. The overflowing water can be re-used after cooling it or drained off as per customer’s requirement.