>> Nitrogen for Oil, Gas and Petrochemical Industries

 

As an inert gas, nitrogen offers a wide range of capabilities to the oil, gas and petrochemical industries. Used predominantly during plant maintenance shutdown and start-up preparations, nitrogen purging and subsequent nitrogen leak testing form a critical path to the success of any project.

 

Nitrogen availability for both project work and ongoing operations has therefore become critically important.

With many oil and gas projects based in remote locations, deliveries of nitrogen to the point-of-use is a major undertaking. With the advent of low cost and reliable nitrogen gas production using air separation in the gaseous phase, many oil and gas projects have opted for in-situ nitrogen generation.

Nitrogen has various applications in the oil and gas and petrochemical industry, including those described below.

 

Blanketing of tanks and tankers

Many hydrocarbons and chemicals are volatile and extremely reactive with oxygen. While storing and transporting these liquids, it is necessary to displace any atmospheric oxygen in the headspace by blanketing with inert gas such as nitrogen.

 

Purging

Nitrogen purging is an industry standard technique for the replacement of a hazardous or undesirable atmosphere with an inert dry atmosphere. The two most common methods of purging are displacement and dilution. The geometry of the process system determines which method is used. For simple systems, displacement purging is often more effective in terms of time and cost. For complex systems, dilution purging is used.

 

Pressure testing

When hydrostatic testing is not possible, components or systems may be tested with nitrogen. However, system design specifications must be reviewed and a detailed risk analysis completed before testing with a compressible medium.

 

Gas lifting

Nitrogen is used in well applications to reduce the weight of fluid in the wellbore. Nitrogen is pumped through coiled tubing (or gas lift tubing) and discharged at the well perforations. As the nitrogen gas flows up the production casing, it expands and reduces the weight of fluid in the column, allowing the well to flow.

 

Cooling of catalyst

During refinery shutdown, it is desirable to reduce the temperature of process catalysts as quickly as possible. Large volumes of nitrogen can be pumped by pumping equipment to assist in the cooling process and save valuable hours of shutdown time.

 

Foam inerting

Nitrogen foam inerting is a simple yet effective process that enables hot work to be carried out on hydrocarbon handling systems in complete safety. The nitrogen foam is injected into a process system at a low-point and allowed to completely fill the vessel and pipework, rendering the internal atmosphere inert.

 

Onsite nitrogen generation technologies

Nitrogen gas can be produced by air separation in gaseous phase by using two distinct technologies – Pressure Swing Adsorption (PSA) and membrane separation. In both technologies, nitrogen gas is produced at pressure by using compressed air as feed and electric power is the only utility required for this process.

In PSA and membrane nitrogen generation systems, the cost of generation of nitrogen is the cost of the power running the air compressor. For systems of up to 5000 nm3/hr, when compared with cryogenically produced nitrogen, both the investment cost and the cost of nitrogen generation is significantly lower. PSA uses Carbon Molecular Sieves (CMS) to separate nitrogen and oxygen. CMS adsorbs the oxygen under pressure and allows nitrogen to pass through as the product gas.

 

PSA is suitable when the purity requirement of nitrogen is higher than 99%. Due to the physical plant size, PSA plants have a constraint on the volume of nitrogen that can be produced from a single system. Even though very large PSA nitrogen plants of volumes as high as 2500 nm3/hr have been built, it is advisable to split large requirements into multiple PSA systems for operational redundancy.

Structurally, a hollow-fibre membrane represents a cylindrical cartridge functioning as a spool with specifically reeled polymer fibres. Air is supplied under pressure into a bundle of membrane fibres. Due to the difference in partial pressures on the external and internal membrane surfaces, nitrogen separation is accomplished. Membrane gas separation units have no moving parts, thus ensuring exceptional reliability. Furthermore, membrane systems require a very small footprint, are suitable for purities up to 99% and, due to a smaller footprint, are suitable for very high flows.

 

AirPro Nitrogen Generators can be delivered to you mounted on a frame, skidded and truck mounted systems or in a shipping container. This makes the generators easily transportable by road, rail and sea.  Designed for outdoors the container provides protection against harsh weather conditions on and off shore.