Patent Number: 
Section: claims

1. An ultrasonic reactor water level measuring device comprising:an upper tube that extends from a gas phase portion in a reactor;a lower tube that extends from a liquid phase portion in the reactor;measurement tubes that are connected to each other and arranged at multiple stages between the upper tube and the lower tube; andunits for generating and receiving ultrasonic waves and measuring levels of water within the measurement tubes, the units being arranged at bottom portions of the measurement tubes,wherein a water level within the reactor is calculated from the sum of the measured water levels, the sum excluding the height of an overlapped part of the measurement tubes. 2. The ultrasonic reactor water level measuring device according to claim 1, further comprisingseparation valves that are arranged in the middle of the upper and lower tubes,wherein when pressure on the side of the measurement tubes is equal to or lower than a set value, the separation valves are automatically closed. 3. The ultrasonic reactor water level measuring device according to claim 1,wherein ultrasonic probes are directly in contact with the water and integrated with flanges so that transmittances of the ultrasonic waves in the water are high, compared with a conventional method using an acoustic couplant. 4. The ultrasonic reactor water level measuring device according to claim 1, further comprisingreflective plates that are arranged in the middle of the measurement tubes,wherein the temperature and pressure of the water are corrected on the basis of ratios of periods of time for waves reflected from surfaces of the water or upper end portions of the measurement tubes to propagate from the surfaces of the water or the upper end portions of the measurement tubes to the generating/receiving units to periods of time for waves reflected from the reflective plates to propagate from the reflective plates to the generating/receiving units. 5. The ultrasonic reactor water level measuring device according to claim 4,wherein the reflective plates have reflection intensities that can be adjusted by adjusting diameters of holes of central portions of the measurement tubes or the areas of constituent members of the measurement tubes. 6. The ultrasonic reactor water level measuring device according to claim 1, further comprisinga temperature sensor that is arranged in at least one of the measurement tubes,wherein a sound speed is determined using a temperature instruction value for the temperature of the water within the measurement tube, and the temperature of the water is corrected on the basis of the sound speed and a time period in which the ultrasonic wave that propagates to the liquid surface or the upper end portion of the measurement tube reciprocates. 7. The ultrasonic reactor water level measuring device according to claim 1,wherein connection tubes and the upper and lower tubes that connect the pressure vessel to the measurement tubes are inclined so that gas-phase-side end portions of the connection tubes are higher than the other end portions of the connection tubes, gas-phase-side end portions of the upper and lower tubes are higher than the other end portions of the upper and lower tubes, and air bubbles are not stored in the connection tubes and the upper and lower tubes.