Process and apparatus for de-icing roadways and re-using collected melting solution

#The present invention relates to a process for de-icing roadways to which is applied a melting-agent solution in water to lower the freezing point, which solution, mixed with precipitation water and melted snow and ice, as melt water which is collected, runs off the roadway, is purified, if necessary, and, after its melting-agent content has been tested, at least partially is re-used by re-applying it to the roadway as the aqueous melting solution, if necessary after adding fresh melting-agent, and further relates to an apparatus installation for implementing the process, with facilities for applying the melting solution to the roadway along the roadways to be de-iced and with extracting devices for the collection of melt water running off the roadway, said extracting devices being connected, via channels, a concentration sensor for melting-agent concentration and a switch controlled by the sensor, on the one hand, to a drainage and on the other hand, to a collector tank which, in turn, is connected to the facilities for applying the melting-agent.

#Such apparatus installation and process are known from publication No. WO 93/00481. According to this reference, the melt water running off roadways, in particular off expressways, is collected and, after adding more melting-agent or a highly concentrated melting solution if necessary, is re-applied to the roadway, in particular sprayed automatically onto the road surface via spray nozzles. Pure rainwater running off the roadway can also be diverted directly to a drainage receptacle. The re-use of the melt water for a new melting solution helps save melting-agent and is also less damaging to the environment, which is otherwise put under strain by the melting-agent content of the melt water, salt in particular. On the other hand, it has been proven that a particularly large quantity of melting-agent has to be added for the implementation of the known process in order to reach the required melting-agent concentration for de-icing purposes. If salt is used for de-icing purposes, a melting-agent consisting of an 25% solutions are used preferably. The melt water has, in the meantime, been rather diluted by added precipitation water and melted snow and ice, so that a major percentage thereof even has to be diverted directly to the drainage receptacle as it is not worth re-using.

#The present invention, in contrast, is to ensure improved evaluation of the re-usable melting-agent. This is achieved by increasing the concentration of the solution in the melt water to be re-used before re-applying it as melting solution by subjecting it to a separation step in the course of which water free of or low in melting-agent content on the one hand and a more highly concentrated solution on the other hand are created as partial flows, preferably by means of an apparatus installation wherein a concentration increase stage is inserted between the collector tank and the facilities for applying the melting-agent, for concentrating the melting-agent in the melt water to be re-used as melting solution and with a drainage for the flow of reduced-concentration melt water. By means of these measures, a higher percentage of melt water can be re-used in the cycle.

#Further details, advantages and developments of the invention are shown in the following description of a preferred embodiment with reference to the drawing. The only figure shows a top view of a roadway with a device along the length of the roadway for the automatic de-icing process.

#The drawing shows a roadway 1 with verges 2 and drains 3 shown along the length of one of the verges, which are connected to a joint drainage channel 5 via run-off channels 4. This installation is marked along the length of one of the verges, it can also be installed on two sides or, in the case of roadways with a median strip, it can be implemented three-fold. On the surface between drains 3 and directed to them there are collecting pipes 6. These installations are required for the extraction of melt water as well as rainwater.

#Further, there are facilities for the application of melting solution along the length of the roadway, that is spray nozzles 11 fed via distribution line 12, which, in turn, is supplied with melting solution, generally salt solution under pressure, via a line 13.

#The melt water collected in drains 3, containing not only the melting solution sprayed onto the road surface but also melted snow and ice and precipitation water, partially is re-used as melting solution after a corresponding re-using process. For this purpose it initially passes through sensor 18, which, in the depicted embodiment, is at the same time a sensor for the pollutant impact of melt water, e.g. for oil, as well as for the melting-agent concentration, and controls two switches 19 and 20; switch 19 is switched on first and is a pollutant switch; switch 20, a solution switch, is connected to one outlet of switch 19. The first outlet of pollutant switch 19 leads to pollutant collector tank 23, which collects water heavily polluted with oil or chemicals spread on the roadway, for example as a consequence of an accident, for the purpose of disposal.