Industry projects – current research put into practice in the industry.
The following projects show examples of the knowhow of CSE-Engineering. All projects were carried out by employees of CSE-Engineering within the last few years.
Sizing of vent lines for multipurpose plants for the throughflow with vaporising gas/liquid mixtures
Vent line – Emergency relief pipe – Two-phase flow
Multipurpose plants are often secured with mechanical safety devices like safety valves or bursting discs. Because of frequent product change, it is important to regularly examine if the safety device is large enough to allow the production of a new product in the existing reactor. However, the sizing of a safety device can be very complex on a case-by-case basis.
As part of a project the release surface depending on the reactor content and type of heating (external heat supply through a heat transfer medium, fire, chemical reaction) was calculated for about 60 typical solvents. Therefor the HNE-DS method was used in consideration of the boiling retardation of the liquid. Recommendations concerning how to handle product changes were developed for multipurpose plants with an existing safety device.
Literature: Schmidt, J. und Stoessel, F. (2011), safety and restraint systems for multipurpose plants. Part 1 – safety concepts and safety devices. Chemie Ingenieur Technik, 83: 1173–1187
Sizing of a safety valve for thwo-phase flow on a multipurpose reactor
Safety valve | Emergency relief pipe | Two-phase flow
The the topic of this project was a multipurpose reactor that should be secured for the use of a certain substance. The maximum of the mass flux that needs to be dissipated has to be determined by a scenario definition. Based on this mass flux the proper safety valve can be determined.
The mass flux that can be dissipated through a safety valve for a two-phase emission can be determined with the HNE-CSE model. This model is a advancement of the approved HNE-DS model which is commonly used in the industry.
Literature: J. Schmidt, S. Claramunt: Sizing of rupture disks for two-phase gas/liquid flow according to HNE-CSE-model, Journal of Loss Prevention in the Process Industries, 41 (2016) S. 419 bis 432
Protection of a heat exchanger for the scenario of a ruptured pipe
Heat exchanger | Safety valve | State of technology
The protection of a heat exchancer had to be conducted for the scenario of a ruptured pipe in this project. The operating pressure of the shell side which has to be secured is 30 bar. In case of a ruptured pipe within the heat exchanger the shell side has to be protected against the inadmissible high pressure of the tube side. Under the assumption that the complete cross section of the pipe is released, the surface that the inadmissible pressure can pass into the shell area is two times the size of the free cross section of the pipe. The mass flux through this are represents the minimum of the mass flux that has to be dissipated through the safety valve. The flow through the valve occurs with a two-component flow out of the medium from the tube and shell side.
Literature: VDI Heat Atlas Chapter L2.3: Sizing of safety devices for heat exchanging devices, Springer Verlag Berlin
Assessment of pressure shocks in a heat exchanger for the scenario of a ruptured pipe
Heat exchanger | Pressure shock | Ruptured pipe
Leakages usually can’t be ruled out in heat exchangers. They are especially critical during the demolition of a pipe because the abrupt change of pressure can cause a pressure shock. This can deeply harm the heat exchanger.
Within the scope of a project the occurring pressure shock in a front head of a heat exchange was estimated. In the studied case, the low-pressure side was on the tube side. For this reason, the medium from the shell side is abruptly penetrates in the tube side. The resulting pressure wave spreads through the pipe until the end of the heat exchanger. Subsequently it spreads hemispherical until it reaches the wall. For this reason heat exchangers should be sized in a way that the pressure shock resistance of the vessel can’t be exceeded not even during the demolition of a pipe.
Simulation of the pressure and temperature profile in a 500 km long grid gas pipeline and evaluation of various pipe line routings
Ecological efficiency analysis | Gas network | Grid gas pipeline
Various pipe line routings of a natural gas high-pressure pipe were assessed for the comparison of the temperature and pressure profiles for different load conditions (mass fluxes, summer/winter mode). Very precice equations of state were considered for different load conditions. The calculations were carried out for a 500 km long pipeline taking into account that natural gas is removed at several places of the pipeline for different consumers.
Places for compressors were optimised and a pipe line routing with a minimum of compressor stations was selected. These stations always require an interference with nature and are associated with high investment costs. With the use of the lowest possible number of compressor stations the CO2-emissions for the compression can be reduced.
Comparison of the approach for the protection of natural gas high-pressure pipelines in Germany and Switzerland
Plant security | Grid gas pipeline | Dispersion calculation
In Germany risks have to be avoided in accordance to a deterministic safety approach. Appropriate safety-related measures have to be taken against risks that cannot be completely dismissed. In neighbouring countries like Switzerland, the Netherlands and Great Britain the evaluation of risks by a probabilistic approach is mandatory.
During this project the approaches for the protection of technical plants in Germany and Switzerland were compared in detail. The swiss framework report for natural gas high-pressure pipelines was used as a basis for the comparison. The influence of the pipe diameter and the permissible pressure of the pipeline on the possible effects during a worst case scenario were considered.
Literature: J. Schmidt: Safety of natural gas high-pressure pipelines in an international comparison using the example of Germany and Switzerland. IRO Oldenburger Rohrleitungsforum, Oldenburg, 7./8.
Measurements of the condensate ratio, number and distribution of particles in natural gas high-pressure pipelines
Grid gas pipeline| Condensate ratio | Flow investigation
In Germany natural gas pipelines are typically operated at pressures between 95 und 50 bar. The pipe diameters are between 500 and 1400 mm. At the gas feed-in stations of the pipe network gas drying plants are located to reduce the moisture within the natural gas through adsorption of water with diethylene or triethylene glycol (lowering of the dew point).
During the drying of the natural gas a very small amount of glycol is dissolved in the gas and flows into the pipeline. As a result of the following temperature and pressure drop in the pipes, the glycol condenses and drops down onto the pipe walls. In case of high flow velocities or foam formation in the gas drying station, glycol can be carried away in the form of aerosols (liquid droplets). Depending on the droplet size, the aerosols drop down immediately after the pipe inlet or get carried away for long distances into the pipe before they drop down onto the wall.
The amount of glycol in the natural gas after the drying process was measured in a gas drying station. Both the dissolved part and the part that got carried away in form of particles (aerosols) were determined. An appropriate test stand for the isokinetic extraction of natural gas and the measurement of the particle size distribution was developed with a xenon transmitted light measurement method. During the modelling of the condensation, the operation mode of the pipeline (summer/winter mode) and the effects of a recondensation of already existing glycoles were considered.
Literature: D. Jerinić, J. Schmidt, M. Piontek: Calculation of the condensation of semi-volatile componets in grid gas pipelines. GWF Gas Erdgas 01/2009