Stockyard layout (re)design Delft University of Technology Faculty 3ME, Transport Engineering & Logistics G. Lodewijks, T.A. van Vianen and J.A. Ottjes
Content • Stockyard functions • Stockyard machines • The machine selection for capacity & blending or homogenizing • The machine selection for the storage of bulk materials • CASE: stockyard layout design for an import terminal • Summary Delwaidedok, Antwerp (Courtesy HeliHolland/Kees Vlot)
Stockyard machines - Overview (1) Handling coal using wheel loaders and mobile feed bunker (Courtesy N.M. Heilig BV) Stacking of coal using a stacker (Courtesy ThyssenKrupp) Circular storage (Courtesy HeliHolland/ Kees Vlot)
Stockyard machines - Overview (2) Bucket wheel reclaimer (Courtesy FAM) Bucket wheel stacker/reclaimer, left: stacking, right: reclaiming (Courtesy ThyssenKrupp)
Stockyard machines - Overview (3) Double sided bridge scraper reclaimer (Courtesy ThyssenKrupp) Reclaiming with a side scraper and stacking with an overhead belt conveyor (Courtesy Taim Weser)
3. The machine selection for capacity & blending or homogenizing
Stockyard machines - Effective capacity ratio (1) • During terminal (re)design, the effective capacity ratio is essential to prevent selecting a machine with insufficient capacity • Effective capacity ratio for a bucket wheel reclaimer relates to the used reclaiming method Long-travel reclaiming method Slewing bench reclaiming method
Reclaiming capacity for the slewing bench reclaiming method relates to (i) slice cross-sectional area, (ii) the slewing speed and (iii) bulk density of the reclaimed material. • The reclaim capacity can be kept stable with an increase of the slewing speed Without slewing speed adjustment With slewing speed adjustment
Stockyard machines - Effective capacity ratio (2) • The effective capacity ratio was calculated for bucket wheel reclaimers for the long-travel and the slewing-bench reclaiming method.
The effective capacity ratio was for the long-travel reclaiming method 75% and for the slewing bench reclaiming method 45% Note: these ratios are not general but were derived using specific input parameters Reclaiming capacity during a time interval of 40 hours for two reclaiming methods
Reclaiming efficiency versus the pile's length for the long-travel reclaiming method
Stockyard machines Main Characteristics
Blending or homogenizing machines • Stacking is the starting point of the blending process. Generally there are four basic stacking methods
4. The machine selection for the storage of bulk materials • Selection of archetype • Cost calculation • Operational performance
Selection of archetype • Multi-purpose machine (stacker/reclaimer) or two single-purpose machines (stacker and reclaimer) Two layout archetypes
Cost calculation • Selection must be based on the archetype’s investment cost and performance • It was assumed that the machine investment cost relates to its weight and the belt conveyor investment cost relates to its capacity Price per meter for belt conveyors versus its transport capacity Stacker/reclaimers weight versus capacities as function of boom length
Operational performance • The performance at dry bulk terminals is generally expressed in the total time that ships and trains spend in the port • The port time is the sum of the waiting time and service time • The ships waiting time relates to: • Interarrival time distribution • Carrier tonnage distribution • The ship (un)loader utilization • Mean service rate • Mean arrival rate Queuing theory formulas or simulation
Main requirements: • Import terminal with an annual throughput of 37 [Mt/y], 21% bypass (no storage and handling by stockyard machines) • Required stockyard area: 92 [ha] • Seaside: bulk carriers, landside: trains • Interarrival time distribution seaside and landside: NED • Carrier tonnage distribution: based on historical data (avg. 101 [kt]) • Train tonnage distribution : uniform distributed between 2 and 4 [kt] • Stockyard machine efficiency: 0.55 [-] • 4 unloaders at seaside and 4 loaders at landside • Average seaside’s port time (Wss): 3 days and average landside’s port time (Wls): 0.5 day • Blending of coal: 1.7 [Mt/y] • 28 different grades of bulk materials must be stored separately
Step 1: • Determine the number of stockyard lanes (nl) and dimension the stockyard lanes (length Ll and width w). • Assume a machine’s boom length (lb) of 60 meter and use 10 meter as distance from the machine’s centerline to the stockyard lane (p). • Assume that the lane’s length (Ll) must be in the range between 1,000 and 1,500 meter • Number of stockyard lanes must be an even number to realize complete archetypes. Calculate the number of archetypes using the following equation: • An outcome is nl = 14, Ll = 1,315 [m] and w = 50 [m]
Step 2: Determine the required machine capacity based on Wss ≤ 3 days and Wls ≤ 0.5 day for both archetypes. Layout A with 7x archetype (I) Layout B with 7x archetype (II)
Step 3: • Calculate the total investment cost per archetype. • Calculate the stockyard machine’s weight (w) based on the determined stacking and reclaiming capacities • Investment cost of the stockyard machine(s): • where for this case it was assumed that κsm was 8 [€/kg], machine fully installed at the stockyard • Investment cost for the belt conveyor(s): • where Lbc is conveyor length (1,400 [m]) and κbc was according Figure slide 22 “upper limit”.
Step 4: • Design the blending bed with associated machine types. • Future: high-quality coal will probably become scarce thus install stacker and reclaimer combination which is able to realize the highest bed blending ratio • Blending bed dimensions: assume coal-fired power plant’s own storage of 5 days and use two blending beds for simultaneously stacking and reclaiming.
Step 5: Final layout.
Summary • Three main stockyard functions: storage, blending and homogenizing • Main characteristics of stockyard machines were presented • The effective capacity ratio for bucket wheel reclaimers differs per reclaiming method; a method has been provided. • Different combinations of stacking methods and reclaimers result in specific bed blending effect ratios. • A selection procedure was introduced to select single-purpose or multi-purpose machines for the storage of bulk materials • For a specific case, the stockyard layout was designed • Future work: Design of the network of belt conveyors