Hydrogen Pipeline

Hydrogen delivery by gas pipeline is currently the lowest cost delivery option at high volumes, and is likely to play a key role in distributing hydrogen in a future hydrogen economy. Currently, few dedicated hydrogen pipelines exist—those that are built to transmit hydrogen as a chemical feedstock for commercial uses, and they are not adequate to broadly distribute hydrogen to serve hydrogen vehicles or household applications. Transport of gaseous hydrogen in pipeline system is a technology, which has long been applied. More than 750 km of hydrogen pipelines (1990) have been put in place worldwide [96]. The German company Hüls AG has started as early as 1938 to operate a hydrogen distribution grid in the Rhine/Ruhr region. Long-distance pipeline transportation of hydrogen gas has not reached an international dimension up to now.

Figure 3.20 Description of hypothetical GH2 pipeline routes [72, 119].

The distribution of hydrogen gas seems to be as straightforward as the distribution of natural gas, and therefore a pipeline similar to that used in natural gas could be employed. As it happens, hydrogen reacts with common seals and lubricants currently used in natural gas pipelines and it will be necessary to develop new materials that will not degrade, nor contaminate the gas on its journey. Furthermore, due to the much lower density of hydrogen, much more gas must be moved through a pipe to deliver a certain amount of energy than in use of natural gas. This means the gas must either be transported at a greater speed, or the pipe must be of greater diameter.

3.7.2.1 System Description

The study considers hydrogen transportation by means of a GH2 pipeline from a hydrogen production plant to a user storage operated in Germany. The pipeline has a distance of 53 km, a diameter of 150mm, is located underground, and the operating conditions are a pressure of 2.4 MPa and a temperature of 15°C [72]. The gaseous hydrogen has regularly transported from facility A to facility B through the GH2 pipeline. It is transported over a distance of 53 km through areas with varying population densities.

The pipeline was installed and constructed to meet requirements according to the "Bundesimmunschutzgessetz" (BImSchG) [72]. It constructed by using special steel materials (e.g. ultrafine grain steels) to meet the requirement of high strength and high ductility to enable a high system pressure and appropriate for welding. Besides, it is wrapped, cathodically protected, and hydro-tested before it is put into service. The pipeline crosses four towns, as shown in Fig. 3.20, with one of them closer than 200 m.

3.7.2.2 The GH Pipeline

Fig. 3.21 shows a diagram of GH2 pipeline and associated measuring and control devices. The pipeline is equipped with two compressors each with a capacity of 8000 N/m3 (piston type)

used to increase the hydrogen pressure to 2.4 MPa (24 bar) at rate of 4000 Nm3/h. The pipeline is located three meters below the ground level. It is divided into seven stations (sections). In case of leakage or any problems in the pipeline each station is equipped with an automatic control to close valve. The valves are placed at specific points. For this purpose two types of valve are normally used, i.e. manually (hand wheel) remotely and operated valves. Besides, the pipeline system is also equipped with measuring and control devices linked to control room located in the "central control room", which constantly manned and from which the system is monitored, controlled and supervised. Table 3-8 shows the most important capacity and dimensions of the pipeline system studied.

Figure 3.21 The transport of hydrogen by underground pipeline [ 187, 72] Table 3-8 Description of the hypothetical GH2 pipeline considered in the study [72]

Product:

Length of pipeline: Diameter: Flow rate: Line type:

Normal operating pressure: Wall thickness: Valve stations:

Hydrogen 53 km

150 mm (outer diameter) 4000 Nm3/h (0.1 kg/s) Underground (3 m) 24 bar, 15°C 10 mm 7

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