This cryogenic storage system project in Cairo, Egypt was developed around a large-scale liquid air separation plant designed to produce and store cryogenic oxygen and nitrogen. The system integrates vacuum-insulated cryogenic storage tanks, liquid transfer pumps, piping, valves, instrumentation, and centralized PLC-based control to provide a controlled interface between cryogenic production and downstream liquid gas distribution.For an overview of how these components work together, see our Cryogenic Storage Systems Guide.
The technical basis for the project is a KDON-1500 full-liquid air separation system with a nominal production capacity of 1,500 Nm³/h of liquid product on a gas-equivalent basis. The system can be configured for liquid oxygen or liquid nitrogen production according to the operating condition. The design documentation specifies dedicated 200 m³ vacuum-insulated storage tanks for both liquid oxygen and liquid nitrogen, together with cryogenic pumps for tanker loading.
Project Overview
| Project Item | Technical Configuration |
|---|---|
| Project location | Cairo, Egypt |
| System type | Cryogenic liquid storage and transfer system |
| Associated process | KDON-1500 full-liquid air separation plant |
| Liquid products | Liquid oxygen (LOX) and liquid nitrogen (LIN) |
| Nominal production basis | 1,500 Nm³/h, gas-equivalent liquid product |
| LOX storage | 1 × 200 m³ vacuum-insulated cryogenic storage tank |
| LIN storage | 1 × 200 m³ vacuum-insulated cryogenic storage tank |
| Liquid transfer | Cryogenic pumps for tanker filling |
| Control system | PLC-based process monitoring, control, alarm and interlock |
Cryogenic Storage System Design
The storage section is designed to receive cryogenic liquid products from the air separation process and maintain them under controlled conditions before delivery to downstream users or liquid tanker vehicles.
For this project, the technical specification includes two independent vacuum-insulated storage systems. The liquid oxygen storage system consists of a 200 m³ vacuum liquid storage tank, associated piping, fittings and valves, together with two cryogenic liquid pumps for tanker loading. The liquid nitrogen storage system follows the same configuration, with a 200 m³ vacuum storage tank and two liquid nitrogen pumps.
Vacuum insulation is particularly important for cryogenic storage because it reduces heat transfer from the surrounding environment and helps limit liquid evaporation during storage. The storage tanks therefore provide a buffer between continuous cryogenic production and intermittent downstream liquid gas transportation.
Liquid Nitrogen Storage System
The liquid nitrogen storage section uses a separate 200 m³ vacuum-insulated cryogenic storage tank. Dedicated piping, valves and fittings connect the tank with the liquid nitrogen transfer system.
Two liquid nitrogen pumps are provided for tanker filling. Their specified operating parameters are a 300 L/min flow rate, 0.2 MPa inlet pressure, 72 m pump head and 20 hp motor power.
Separating the LOX and LIN storage systems allows each cryogenic liquid to be handled through its own tank, piping and transfer equipment. This configuration is suitable for facilities where liquid oxygen and liquid nitrogen are produced and distributed as separate products.
How the Cryogenic Storage System Works
The basic process can be summarized as:
Air separation → Cryogenic liquid production → Cryogenic storage → Liquid transfer → Tanker filling → End-user delivery
In the associated air separation process, atmospheric air is filtered, compressed, precooled and purified before entering the cryogenic separation section. Molecular sieve purification removes moisture, carbon dioxide and certain hydrocarbons before the purified air enters the main heat exchanger and distillation system.
Liquid oxygen is withdrawn from the lower section of the upper distillation column, subcooled and delivered from the cold box as product. Liquid nitrogen is produced through the corresponding nitrogen separation process. The cryogenic products are then directed to their respective storage systems.
Once liquid product is required for distribution, the corresponding cryogenic pump transfers the liquid from the storage tank to the tanker-loading connection. This creates a practical interface between continuous production and scheduled liquid gas transportation and forms part of an integrated industrial gas supply system.
Storage System Control and Instrumentation
Reliable instrumentation is essential for a cryogenic storage installation because pressure, temperature, liquid level, flow and equipment status must be continuously monitored.
The project technical specification uses a PLC-based control system for the overall air separation and associated liquid storage process. The control scope includes monitoring and alarm functions for the liquid storage and vaporization sections, while important operating parameters are displayed and recorded through the central control system.
The instrumentation package includes pressure and differential-pressure transmitters, temperature measurement, liquid-level measurement, flow measurement, control valves, online gas analysis and alarm/interlock functions. The specification also calls for online analysis of key process parameters, including oxygen, nitrogen, carbon dioxide and moisture.
This centralized control approach helps operators monitor storage conditions and coordinate the cryogenic production, storage and transfer processes from a central operating station.
Design Conditions for Cairo
The technical proposal uses a design ambient temperature of 32°C and relative humidity of 80%, together with an atmospheric pressure of 101.3 kPa. These conditions are relevant when designing outdoor cryogenic equipment, cooling systems, insulation, instrumentation and supporting utilities for the project location.
The associated cooling-water system is designed around a 32°C inlet temperature and 42°C return temperature. The electrical design basis includes 9 kV high-voltage power and 380/220 V low-voltage power at 50 Hz. These utility requirements should be confirmed against the final site conditions and local project requirements before detailed engineering.
Cryogenic Equipment and Components
The storage system is part of a larger integrated cryogenic plant. Major equipment in the associated process includes the air intake filtration system, centrifugal air compressor, air precooling system, molecular sieve purification system, distillation columns, main heat exchanger, turboexpander, cryogenic storage tanks, cryogenic pumps and instrumentation.
The technical proposal specifies a 19500 Nm³/h centrifugal air compressor, an air precooling system, two molecular sieve adsorbers and a cryogenic distillation system. The cold box includes aluminum plate-fin heat exchangers and low-temperature distillation equipment designed for temperatures down to approximately -196°C.
For the storage section specifically, the main equipment includes:
- 200 m³ vacuum-insulated liquid oxygen storage tank
- 200 m³ vacuum-insulated liquid nitrogen storage tank
- Liquid oxygen cryogenic pumps for tanker filling
- Liquid nitrogen cryogenic pumps for tanker filling
- Cryogenic product piping and fittings
- Low-temperature valves
- Pressure, temperature and liquid-level instrumentation
- PLC-based monitoring and control
- Alarm and process interlock functions
Safety Considerations
Cryogenic oxygen and nitrogen storage requires appropriate controls for low-temperature fluids, pressure management, oxygen service cleanliness, liquid-level control and safe transfer operations.
The associated air separation plant incorporates safety measures including pressure relief devices, controlled valve operation, monitoring of process parameters and online analysis. The technical proposal also identifies the main cryogenic heat exchanger as a critical safety area and describes measures intended to control hydrocarbon accumulation and maintain safe operating conditions.
For the storage system, final safety design should be coordinated with the applicable Egyptian requirements, project specifications and the relevant pressure-vessel, cryogenic equipment, oxygen-service and electrical standards applicable to the final installation.
Project Engineering and Integration
A cryogenic storage system is not simply a storage tank. The tank must be integrated with the upstream production system, cryogenic transfer equipment, tanker-loading connections, instrumentation, electrical systems and operating controls.
For this project, the storage equipment is integrated with the air separation plant so that liquid products can move from the cold box into dedicated storage and then to tanker-loading facilities. This arrangement provides additional storage capacity between production and distribution and allows liquid gas deliveries to be managed independently from the instantaneous production rate.
The project documentation also specifies PLC control of the major process systems, including the air compressor, precooling system, purification system, distillation system, turboexpander and liquid storage system.
Why Use Vacuum-Insulated Cryogenic Storage?
Vacuum-insulated storage tanks are widely used for bulk storage of liquefied gases because the vacuum space significantly reduces conductive and convective heat transfer. Combined with appropriate insulation and cryogenic piping, the storage system can maintain the required low-temperature conditions while limiting unwanted heat input.
For a liquid gas production and distribution facility, bulk storage also provides operational flexibility. Production can continue while tanker loading is scheduled according to delivery requirements, while the storage capacity provides a buffer between the production plant and downstream customers.
Application of the Project
A cryogenic storage and transfer system of this configuration can support bulk distribution of liquid oxygen and liquid nitrogen to industrial, medical, laboratory, energy and other users requiring reliable supplies of cryogenic gases.
With separate LOX and LIN storage tanks and dedicated tanker-loading pumps, the system is suited to a bulk liquid gas supply model in which products are stored at the production site and subsequently transported to customer facilities.
Project Summary
This Cairo project demonstrates an integrated approach to cryogenic liquid storage, combining large-capacity vacuum-insulated tanks with cryogenic transfer pumps, process piping and centralized instrumentation and control.
The technical configuration includes 200 m³ liquid oxygen storage capacity and 200 m³ liquid nitrogen storage capacity, with dedicated cryogenic pumps for tanker filling. The storage systems form the distribution interface between the associated air separation plant and downstream liquid gas transportation.
For projects requiring bulk liquid oxygen, liquid nitrogen or other cryogenic gases, tank capacity, operating pressure, product purity, filling rate, ambient conditions, utility availability and applicable local standards should be established during the engineering stage. The final cryogenic storage configuration should then be developed around the customer’s production and distribution requirements.
Related Cryogenic Equipment
Looking for a cryogenic storage system for your project? Contact our engineering team with your required liquid gas, storage capacity, operating pressure, site conditions and delivery requirements for a project-specific configuration.
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