Lehigh Cement operates plants in Edmonton, AB and Delta, BC. This is where we supply cement for all of Lehigh Hanson Canada’s affiliated companies. Learn more about our Delta Plant and processes below.
Raw Material Silos
There are five raw material silos: one 3000 tonnes (T) (3,300 short tons (t)) silo for limestone; two 2500 T (2,750 t) silos for shale; one 360 T (400 t) silo for silica; and one 150 T (165 t) silo for iron slag. Underneath are weigh scale feeders, controlled in real-time by the laboratory, that proportion approximately 79% limestone, 15% shale, 3% silica and 3% iron slag onto a belt conveyor that feeds to the roller mill in the raw grinding system.
Electrostatic Precipitator - Roller Mill
The electrostatic precipitator comes after the raw grinding system and its role is to remove the ground rock carried out of the roller mill by the air stream that passes through the mill. This precipitator unit has three full electrical fields in series and two parallel half fields immediately after the third field. In each electrical field, a network of wires passes electrical charges to the rock particles. The particles are then collected on oppositely charged plates and fall into hoppers. The de-dusted material is known as ground raw meal which ultimately is used as kiln feed. There is another large electrostatic precipitator on the site to de-dust warm air coming from the grate cooler as well as fifty five baghouse dust collectors sited throughout the plant to remove dust wherever it might be generated.
The recovered fine raw meal from the roller mill is blended in two Fuller Air Merge blending silos. The blending silos use low pressure air to mix the raw meal and make it chemically uniform. Subsequently the meal, now called kiln feed, is conveyed to the top of the four stage preheater tower by a pneumatic lift system.
Down from the preheater tower in continuation of pyroprocessing, the hot, semi-calcined kiln feed goes into the rotary kiln where it is heated to approximately 1450°C (2650°F) to undergo still more chemical changes to form the intermediate product of clinker. The kiln is the heart of the cement plant. It is 88 m (289 feet) long by 5.2 m (17 feet) in diameter and weighs more than 1400 T (1540 t) and rotates almost two and a half times per minute. The daily clinker production rate is 3500 T per day (3850 t). Located at the discharge end of the kiln is the Pillard Tri-fuel Rotoflam burner which supplies 80% of the total heat in pyroprocessing, the remaining 20% being fired at the bottom of the preheater. The main fuel used in the plant is pulverized coal.
Electrostatic Precipitator-Grate Cooler
This electrostatic precipitator de-dusts the excess warm air coming from the grate cooler. The recovered fine material goes onto the common clinker conveyor after the cooler to the clinker silos. The precipitator unit has three electrical fields in series.
Coal Storage & Coal Mill System
Coal is the main fuel for both the kiln and the preheater tower. The coal is ground in a 1000 hp KVS ball mill with a Polysius SEPOL dynamic separator. This coal mill system has a production rate of 20 T per hour (22 t). The pulverized coal is conveyed to and stored in a 200 T (220 t) coal bin. Two Pfister rotary weigh feeders control the coal firing rate to the tri-fuel Pillard main burner for the kiln and the riser duct burner in the pre-heater tower. This is an indirect firing system since the pulverized coal goes first to a storage bin and not directly to the burners.
At the packhouse silos there are three bagging machines that bag Type GU General Use cement, Type HS High Sulphate Resistant cement and Specialty Masonry cement. While homeowners may be most familiar with bagged cement, it represents only a small part of the plant production. Most of the cement is shipped in bulk to terminals, ready mix concrete plants and concrete products manufacturers.
Cement Storage Silos
Storage for cement consists of nine packhouse silos and six dock silos. Cement from the pack silos is shipped out in bags or in bulk via truck and rail. Cement from the dock silos is shipped out by barge.
Fraser River Dock
At the dock there are two barge unloading stations for raw materials. Limestone, shale, silica and gypsum are unloaded from the barges by front end loaders and either conveyed or trucked to storage. Also at the dock, there is a station where covered barges are loaded with cement which has been pneumatically conveyed from the dock silos.
As an alternative fuel, Bunker C fuel oil is available for firing in the rotary kiln. Coal, natural gas, bunker oil, waste oil and recycled tires are all fuels that can be fired under strict conditions set out in the plant’s air emission permit issued by Metro Vancouver.
Clinker is interground with limestone and gypsum in two Aerofall 12.5 m (41 feet) by 4.2 m (14 feet) diameter two compartment ball mills coupled with Fuller O-Sepa dynamic separators for classification to produce the finish cement products. Each mill has a 4500 hp motor and a grinding capacity of 80 T/hr (88 t) for CSA Type GU / ASTM Type I/II cement for local and export markets. EcoCemPLC (CSA Type GUL) and Specialty Masonry cements are also produced from these mills at a slightly lower capacity.
Clinker Storage Silos
There are four silos and an interstice that have a total storage capacity of 85,000 T (94,000 t) for clinker. In the same location, there are two additional silos for gypsum and masonry limestone. Weigh scale feeders underneath the silos proportion the correct amount of clinker, limestone and gypsum for the specific product being produced onto belt conveyors that feed directly to two ball mills for the cement grinding. CSA Type GU (General Use), ASTM Type I/II (Normal Portland), EcoCemPLC (CSA Type GUL) and Specialty (Masonry) cements are produced from these mills.
Raw Material Storage Building
The raw material storage building is over 215 m (700 feet) long and has a total storage capacity of 110,000 T (121,000 t). Limestone, shale, silica and gypsum are unloaded from the barges and transferred to the building for storage. The Schade portal scraper reclaimer inside the building automatically reclaims the raw materials onto a belt conveyor to the raw material silos.
Clinker leaves the rotary kiln and enters directly into the Claudius Peters inclined grate cooler where it is air-cooled to about 100°C (212°F) and then conveyed to the clinker storage silos. At the end of cooler is a hammer mill that breaks down any large clinker balls before exiting onto the conveying system to the silos.
Recycled Tire Storage
As an additional energy source, recycled whole tires are injected one at a time at a rate up to 1 T/hr (1.1 t/hr) into the lower section of the riser duct of the preheater. Each tire drops down into the kiln inlet where it will combust. Whole tires make up approximately 7% of the total fuel for pyro-processing.
The raw meal is conveyed to the top of the four stage preheater tower to begin pyroprocessing. The preheater tower stands 85 m (280 feet) in the air. From a distance it is the dominating feature of the cement plant. The preheater consists of a series of large cyclones and ductwork whose only purpose is to recover heat energy and transfer it to the kiln feed. In the lower part of the tower, the kiln feed starts to undergo chemical reactions or pyroprocessing. The raw meal is in direct contact with hot combustion gases as the meal travels from the top of the preheater down into the rotary kiln. 16% of the total heat for pyro-processing is supplied with the riser duct burner in the preheater and 4% from whole tires that combust in the inlet section of the kiln. The remaining 80% of total heat is supplied by the main kiln burner located at the discharge end of the kiln.
Raw Grinding Mill
Rock from the raw material silos is metered to the 2500 hp Polysius vertical roller mill. Inside the mill, within seconds the rock is ground as fine as flour. Four roller tires pulled down hydraulically on top of a rotating table grind 275 T per hour (300 t/hr) of rock. To achieve the necessary raw meal fineness, there is a FLS dynamic separator above the grinding rolls.