DVGW G 262 Use of Gases from Renewable Sources in Public Gas Supply

The standard “DVGW G 262 Use of gases from renewable sources in public gas supply”, developed by the German Technical and Scientific Association for Gas and Water (DVGW), specifies the requirements for gases from regenerative sources that are available for public use. This standard includes a procedure for determining the quality of renewable gases supplied to the grid. This standard currently only allows a maximum hydrogen concentration of 10 percent in Germany.

The regeneration gas is a portion of the dried gas that has been cooled to ambient temperature after passing through the regeneration bed and taking up desorbed water. The source of this gas depends on the plant requirements and the availability of a suitable gas flow. The regeneration gas should be dry when low effluent moisture content (in the range of 0,1 ppm) is required.

In recent years, studies on increasing thermal efficiency have gained momentum. Increasing thermal efficiency reduces fuel consumption, leading to a decrease in operating costs, which in turn reduces the emission of flue gases (carbon dioxide, (such as nitric oxide and nitrogen dioxide) emissions to the environment. Therefore, intensive research activities are being carried out to increase the thermal efficiency of thermal power generation of gas and steam turbine cycles. Different methods are used to increase the thermal efficiency of cycles. Reheating is a process used to increase the thermal efficiency of gas and steam turbine cycles. Regeneration is also a process used to increase the thermal efficiency of both simple gas turbine and steam turbine cycles.

Regenerative is a thermal process that uses the residual heat energy of the exhaust gases from the gas turbine. This can be done by exchanging heat between the hot exhaust gases from the gas turbine and the compressed air from the compressor using a shell and tube heat exchanger.

The regenerative cycle, in which the exhaust gas is used in a heat exchanger (regenerator) to preheat the compressor discharge air before it enters the combustion chamber, and the combined cycle, in which the exhaust gas is used in a heat recovery steam generator to produce steam for plant use or as expansion fluid, are steam turbines.

Regenerative cycle is a widely used method and is independent of temperature range. In regenerative cycle, a regenerator is added between the pump and the evaporator to reuse the waste heat from the low-pressure gaseous refrigerant at the turbine outlet. Thus, the refrigerant temperature at the evaporator inlet increases and the temperature at the condenser inlet decreases, which can reduce the heat transfer temperature differences between the evaporator and the condenser and take advantage of their thermal coupling.

With the publication of G 260, the DVGW G 262 standard, which specifies the quality of renewable gases fed into the grid, has been withdrawn. However, users still have to comply with the German gas grid entry regulation. This regulation requires that biogas legally containing hydrogen from regenerative sources must comply with the conditions specified in the DVGW G 260 and DBGW G 262 standards at the feed-in point and during the feed-in. As a result, regenerative gases fed into the grid to date still have to comply with these standards.

The requirements for the quality of fuel gases for the public gas supply are set out in the DVGW G 260 standard.

According to DIN EN 51624, 2 percent hydrogen is tolerated in the natural gas network. Due to the danger of hydrogen embrittlement in natural gas tanks in passenger cars, the mixing ratio cannot be increased. The DVGW standards (including the G 262 standard) specify regulations for the use of gases from regenerative sources in the public gas supply. These regulations relate to different application conditions. Thus, manufacturers limit the mixing limit of hydrogen for gas turbines to 5 percent by volume or even 1 percent by volume in some cases. Other regulations of the G 262 standard state that only cavern storage facilities are suitable for storing hydrogen. All storage facilities can be used if the mixture contains no more than 1 percent hydrogen by volume. Furthermore, lower yields are expected in the summer months. As a result, mixing of hydrogen and natural gas is only possible to a limited extent, so that higher hydrogen concentrations can occur. According to the DVGW regulations, a hydrogen concentration of up to 10 percent by volume is permitted in the natural gas network, with increases of up to 20 percent by volume being envisaged.

Among the numerous testing, measurement, analysis and evaluation studies carried out for businesses in various sectors, our organization also provides testing services defined in the “DVGW G 262 Use of gases obtained from renewable sources in public gas supply” standard with its trained and expert staff and advanced technological equipment.