Construction of HDP Enviro-mat for Heavy Lifting at the Dangote Petroleum Refinery and Petrochemicals

The Dangote Petroleum Refinery is located at Lekki Free Zone, Lagos, Nigeria, with a processing capacity of 650,000 barrels per day (bpd) of crude oil. Once commissioned, it would be Africa's biggest petroleum refinery and the biggest single-train refinery in the world. It is expected to boost Nigeria's oil exports and reduce its reliance on petroleum product imports, thereby improving economic growth and creating thousands of jobs.

The Dangote Petroleum Refinery at a Glance

The Dangote Petroleum Refinery is made up of two main units:

Processing units: The Dangote Petroleum Refinery is composed of different processing units, with each contributing to the process of turning crude oil into finished petroleum products. The processing units are either separation units, conversion units, treatment units, or supporting process units. The major processing units include the crude distillation unit (CDU), residue fluid catalytic cracking (RFCC) unit, gasoline block, alkylation and C4 butamer block, sulfur block, mild hydrocracking (MHC) unicracking unit, hydrogen generation unit, and polypropylene unit.

Offsite and Utilities: These consist of the areas outside the process units. They include tank farms, utilities, and marine infrastructure.

Tank Farms and Trading Facilities: This comprises crude tanks for receipt of crude through SPM via dedicated pipelines, crude storage and intermediate storage tanks, blend component tanks, product tanks, product dispatch day tanks, pump stations, truck loading gantries, etc.

Utilities: The Dangote Petroleum Refinery needs utilities in order to function. The major utility systems include: water systems (such as raw water systems, cooling water systems, dimerized water systems, condensate polishing units, and effluent treatment plants); a 435 MW captive power plant to supply electricity for refining operations; firefighting facilities; flare trestles; extensive piping networks; etc.

Marine Infrastructure: This is made up of 2 crude SPM capable of unloading ships from Aframax to VLCC tankers up to 320,000 TDWT connected via 2x48" subsea crude pipelines with interconnection; 3 product SPM for hydrocarbon products and ethanol unloading, capable of handling a range of vessels from 20,000 TDWT to 160,000 TDWT (Suez Max vessels) via 4x24" subsea pipelines with segregation between grades; and one berthing facility to handle the auxiliary crafts to service the above infrastructure, as well as slurry evacuation.

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After the successful construction of the equipment foundations in the various units of the refinery, there was the need to transport a total of 239 heavy refinery components weighing about 84,900t over a distance of 10km from the jetty at the Atlantic Ocean to the refinery site. Transportation and heavy lifting of the refinery components require a stable ground surface capable of bearing very heavy loads. To accomplish this task, Mammoet, a heavy equipment lifting and transporting company, was engaged to stabilize the reclaimed swampland into a stable heavy lift surface and help transport the heavy refinery components to the site as well as install some of them.

Prior to transportation and installation of the heavy equipment, civil ground preparation works and the construction of HDP Enviro-mat were carried out by Mammoet with its Nigerian partner, Northridge Engineering, under the close supervision and management of the Dangote supervisory civil team.

Civil Ground Preparatory Works and Construction of HDP Enviro-mat

The access roads, hard stands, laydown areas, and crane pads needed to be ready before the delivery of refinery components to the site and heavy lifting operations. Access roads and turns were widened, leveled, and reinforced to carry the weight of the heavy cargo to be transported from the jetty to the refinery site. In order to provide solid pavement for access roads, laydown areas, hard stands, and crane pads, Heavy Duty Pavement (HDP) Enviro-Mat was employed. Mammoet's inventive and environmentally friendly method of ground reinforcement is called Enviro-Mat, a highly advanced method for improving soil bearing capacity. It was developed as a method of strengthening the soil so that it could support extremely heavy loads without settlement during transportation to the site and heavy lifting operations.

Civil ground preparation work, such as the supply, leveling, and compaction of earth materials, was completed at laydown locations, hardstands, and assembly areas prior to the construction of the enviro-mat. Unsuitable soil was substituted with suitable sand and compacted in layers to receive the Enviro-mat. Installation of Mammoet's Enviro-Mat was carried out by combining the natural soil, Portland cement, and the Enviro-Mat additive. The Enviro-Mat was sprayed with a tank truck, and the mixture was thereafter adequately compacted with a roller. Under the careful supervision of Dangote's supervisory engineering team, Mammoet, with its partner, Northridge Engineering, carried out the required civil ground preparatory works and constructed the needed HDP enviro-mat, thereby improving the load carrying capacity of the soil by up to 50 tons/m2.

The following civil ground preparation works and HDP enviro-mat were constructed by Mammoet under the strict supervision of Dangote’s supervisory engineering team:

- Preparatory ground work 25,000 m2 ODC Laydown area plus PT50 PTC 200/140DS Hardstands

Preparatory Ground Work for ODC Laydown Area (125,489 m2)

- Preparatory Ground Work and Construction of 180,000 m2 ODC Laydown Area

- Construction of a 25,000 m2 laydown area plus 2,250 m2 hardstand and assembly areas for the CKE2500 crawler crane

- Construction of 54,000 m2 PT50 crane hardstand plus assembly areas

- Construction of 34,900 m2 PTC 200DS and 140DS Crane Hardstand

- Construction of the 85,750 m2 hardstands and 28,890 m2 assembly areas for the crawler main crane and tailing crane areas.

Seven Enviro-Mat yards were built in total, at a maximum rate of about 5,000 m2 per day, comprising laydown areas totaling 253,776 m2, assembly surfaces totaling 36,059 m2, and 78 heavy lift crane hardstands totaling 80,000 m2.

?After the civil ground preparation and construction of HDP Enviro-mat were finished, Mammoet mobilized the necessary lifting and transport equipment to the refinery site. Equipment mobilized to the site includes conventional trailers and trucks, hundreds of axle lines of SPMT, and mobile and crawler cranes with capacities ranging from 250t to 1600t. Also, Mammoet mobilized its two largest ultra-heavy lift ring cranes, the PTC 200 DS and PT 50, to ensure the project is executed as efficiently as possible.

List of major heavy equipment lifted and installed successfully at the Dangote petroleum refinery:

Lifting of a 3,000-ton regenerator: The 3000-ton regenerator measures 56 meters long, 23 meters wide, and 25 meters high. It was offloaded from the ship by the roll-off method using 108 axle lines of SPMT in a 3 x 36-line configuration and then safely transported to the site. It is the world's heaviest regenerator (3000T) and was successfully erected by Mammoet!

Lifting of a 1,673-ton Reactor: A 1673-ton reactor, measuring 44 meters long, 16 meters wide, and 17 meters high, was transported using 78 axle lines in a 3 x 26-line configuration and installed successfully.

Lifting of a 2,350-ton crude column: The crude column, which is 112 meters tall, was lifted and placed on its foundation as a single piece successfully.

Installation of 1,240T of propylene-mounded bullets: the propylene-mounded bullets weighing 1,240T were installed perfectly well.

?At the completion of its scope, Mammoet succeeded in transporting about 239 heavy refinery components weighing about 84,900 t over a distance of 10 km from the jetty at the Atlantic Ocean to the refinery site, as well as installing a total of 154 heavy refinery components with a total weight of about 68,000 t.