Abstract
Scale deposition in wells and in pipes on the surface has been a serious problem for geothermal power plants as the effective method for removing the scales or for preventing the scales from being deposited has not been established yet. In this study, in order to clarify the performance of high speed water jets in removing geothermal scales, fundamental experiments were carried out for three kinds of geothermal scales, a calcium carbonate scale and two silica scales, which were deposited in transportation pipes. Slot cutting in water was conducted first to know the effect of driving pressure and standoff distance, and then removal of the scales with rotary nozzles was tested to clarify the effect of rotary speed, rate of feed and driving pressure. As a result, it is shown that high speed water jets can remove geothermal scales almost perfectly without damaging the pipe if sufficient driving pressure is employed, and that optimum rotary speed gives the largest rate of removal. The test results also show that the driving pressure required to remove the scales is roughly proportional to the tensile strength of the scale, and that larger size of 5 to 15 mm is predominant in particle size distribution of removed scales.
