Case Studies

Ellwood Quality Steels
Richard Schochet, Engineering Manager for EQS was asked to identify and select proven equipment to handle and deliver the dolomitic lime

Background

Ellwood Quality Steels’ New Castle, Pennsylvania plant is a custom steel toll ingot producer. EQS combines railcar supplied scrap metals with ferro-alloys such as cobalt, manganese, nickel, and others, and special “conditioner” additives such as pebble and dolomitic lime to produce made-to-order shapes and sizes of steel to 400(+) specifications. After cooling, ingots are shipped to open die forgers that produce specialized products such as corrosion resistant deep sea drilling equipment and heavy-duty aircraft landing gear, among other diverse goods.

The Problem

Ellwood supplies its customers with custom and exacting metallurgical specification steel without sacrificing production capacity. As such, EQS has to utilize accurate and dependable automated systems wherever possible in its production process. A key steel additive, dolomitic lime, had previously been manually added into the 3000° arc fired furnace ladles via sacks. This method was not production efficient, presented undue safety risks and resulted in unacceptable levels of spillage and dusting. Bulk and semi-bulk supply were considered with bulk being the method of choice based on cost pay back analyses.

Richard Schochet, Engineering Manager for EQS was asked to identify and select proven equipment to handle and deliver the dolomitic lime. Schochet favored a pneumatic conveying approach over mechanical alternatives for several reasons including accurate yet speedy delivery with dust control and a desire for system integration and high operational reliability. However, due to its hygroscopic and abrasive character, dolomitic lime presented unusual handling challenges for most pneumatic conveying equipment. Schochet initially considered a dilute phase pneumatic system but rejected this alternative due to the highly abrasive nature of dolomitic lime, which would degrade the vanes of the air lock and thus further decrease the limited ability of a dilute phase system to deliver precise quantities of the material. A dense phase pneumatic system was then considered but later rejected in favor of a semi-dense phase system due to concerns about material clumping in the batching process, and plugging while “slugged” in the convey line.

The Solution

Based on Ellwood’s experience with Cyclonaire brand semi-dense phase equipment from other applications and installations in its facilities, Schochet and others selected Cyclonaire’s proprietary Semi-Dense Phase C-3/20 Conveyor equipped with load cells, automated weigh / batch programming and remote control system capabilities for Ellwood’s dolomitic lime injection application. Cyclonaire Vibra Pad aeration / vibration kits, using existing “dried” or conditioned plant air, were installed in the silo cone and in the conveyor cone to prevent bridging and clumping due to the material’s affinity for moisture.

Results

The C-3/20 semi-dense phase conveyor used at EQS is gravity filled from an overhead silo, although it is also capable of venturi-induced vacuum loading via the same low pressure (15 psig) blower used to pressure convey materials to their destination(s). Vacuum loading is utilized where overhead space for gravity loading is not practical, such as with existing silos, and where the cost of excavation for pits to increase vertical clearance is prohibitive.

From the control room the ladle / furnace operator can quickly enter precise quantities of dolomitic lime via a touch sensitive color graphic operator interface CRT screen and programmed logic controls (PLCs) based on predetermined metallurgical batch recipes for varying individual custom orders. The precise amount of lime is then automatically weighed from the silo outside the plant wall into the Cyclonaire C-3/20 conveyor and then conveyed via an underground convey line into the ladle. Manual fail-safe capability ensures that data and operation is maintained in the event of power fluctuations.

Program controls enable the pneumatically actuated slide gate between the silo cone and the Cyclonaire conveyor to accurately dispense the required amount of lime via input feedbacks from the load cells and slide gate positions based on initial gross loading followed by more precise dribble feeding when 90+% of the required batch is reached.

Schochet commented, “We have been pleased with the performance of Cyclonaire equipment after the addition of the VibraPads to aerate the dolomitic lime with conditioned plant air. This material is now delivered in assured quantities as specified by the ladle operator via the automated control system.”

Cyclonaire C-Series conveyors identical to the one used at EQS are also capable of vacuum or gravity loading from multiple sources, such as separate bulk material silos or hoppers, and pressure conveying to multiple destinations, such as more than one blast furnace ladle.