In recent years, NEWTEK has continuously undertaken onshore LNG engineering construction projects in Russia, Africa and other countries, among which the most complex is the construction of core process modules for LNG processing. Based on an engineering example of the construction of a core process module for onshore LNG in Russia, we introduced the key technologies of site layout, prefabrication, integration, space assembly, and module loading for the construction of onshore LNG core process modules.
Keywords: liquefied natural gas; core process module; segmentation; integration; loading
Liquefied natural gas (LNG) is recognized as the cleanest and most efficient fossil energy on earth. Many countries have listed LNG as the preferred fuel. In China, as a low-carbon and environmentally friendly primary energy source, the development and application of LNG is also related to the effective promotion of carbon peak and carbon neutrality strategies. In recent years, the production and trade of LNG in the world have become increasingly active, and LNG is becoming a new hot spot in the world's oil and gas industry.
Establishing an LNG processing plant on land is a main means of obtaining liquefied natural gas. The LNG processing plant is usually divided into several process modules in the design stage to complete the construction of a land LNG processing plant. After the construction of each module is completed on site, it is shipped and transported to the mining site for installation and connection. The construction technology of the core process module of land LNG is mainly reflected in the main construction links such as site layout, prefabrication of segments, integration, space assembly, and module loading.
Features of core process modules
Features of core process modules The core process module is a steel structure that includes mechanical equipment, process pipelines, outfitting materials, and industrial cables. It has the characteristics of large number, large volume and weight. Taking a land LNG module construction project in Russia as an example, the entire processing plant contains 36 core process modules with a total module weight of 141,000 tons. The largest single module weighs 6,284 tons, and the length, width and height are 36 meters, 50 meters, and 37 meters respectively. The structural form of the module is mostly a space frame supported multi-leg structure composed of round tube column tie bars and steel decks. The column spacing is 7 to 12 meters, and there are usually 4 to 7 decks.
Site layout
The layout of the construction site should enable parallel construction of multiple modules on site, and completion and shipment in sequence according to the project plan. Usually, the modules are arranged in an open construction area close to the loading dock in the order of shipment, and a crane passage and assembly space are reserved nearby. When planning the layout, the shipping path of each module and possible interferences on the path and solutions should be considered in advance. For modules with heavier weight, it is also necessary to verify whether the site bearing capacity of the area meets the construction requirements.
Slice prefabrication
Due to the huge workload of the steel structure of the core process module, in the actual construction process, the module structure is usually divided into several pieces. After the individual pieces are prefabricated in the workshop, such as assembly, welding, inspection, and painting, they are transported to the module construction site for assembly. This improves work efficiency and reduces the assembly and hoisting workload at the construction site. According to the structural characteristics of the multi-layer deck of the core process module, the segmentation is generally carried out around the splitting of the deck. For larger modules, the deck is usually split into several structural segments. The segmentation plan is dominated by the crane capacity at the construction site, while taking into account the convenience of segment prefabrication, installation and docking..
Integration and spatial assembly
Integration is to install the pipe brackets, cable brackets and a small number of pipelines and cables planned on the deck as much as possible before the space assembly on the basis of the prefabrication of the structural segments, so as to reduce the amount of professional on-site installation such as piping and electrical. At the same time, since the bracket is installed on the ground, the bracket can be painted as a whole with the deck, eliminating the work of on-site repainting after the bracket is installed. After the prefabrication and painting of the structural segments and the integrated segments are completed, the space assembly can be carried out. The space assembly should be hoisted in the order required by the overall construction plan, and finally the main structure capping is completed.
Most of the deck segments of the core process modules of a land LNG module construction project in Russia are built in an integrated manner, among which the seventh layer of the compressor low-pressure scrubber module is the most complete. The external dimensions of a single segment built in an integrated manner are 42 meters x 26 meters x 8 meters and weigh 330 tons. 1,472 brackets, 276 meters of cable brackets, and 164 pipelines were installed in sections, avoiding the installation of side plugs for 245 pipelines under the 7th floor, saving 21 days of pipeline installation time, 750 hours of 250T strand cranes, and approximately 4,536 man-hours of labor.
Module Shipment
Due to the large weight and volume of the core process modules, they are generally transported to the construction site by sea after construction. This requires that after the module construction is completed, several thousand tons of modules need to be transferred to the transport ship, but the general site does not have land lifting resources above a thousand tons. The use of self-propelled module transporters (SPMTs) for loading can solve this problem well, while saving a large amount of slideway resources required for loading by slideway sliding. This is also the most commonly used loading and exporting method in the construction of land LNG modules at home and abroad. To realize the loading of SPMT, in addition to considering the number of axis lines and support point layout of SPMT, it is also necessary to comprehensively consider factors such as ship mooring, ship load adjustment and environmental conditions.
Conclusion
In summary, the construction technology of the core process module of LNG on land is a modular construction technology. This technology is reflected in various key construction tasks. The reasonable application of this technology can achieve the good effects of shortening the construction period, reducing the construction cost and improving the construction quality. It is the further research and development direction of the construction technology of land modular structures in the future.
