| 摘要 |
An evaporator includes a tank covered by a lightweight lid which is easily lifted to avoid high pressure in the event of an explosion. The bottom of the tank includes a flat portion which slopes downwardly toward an outlet in the sidewall of the tank. The flat section is substantially wider than the outlet to accommodate use of a square-nosed shovel to clean the tank. A fire tube in the bottom of the tank receives hot gases from a burner. A thermometer senses the temperature of the wall of the fire tube to respond to low liquid level in the tank, scale on the fire tube wall, and buildup of solids in the mixture. The open lower end of an upwardly extending standpipe is in liquid in the tank. The upper end of the standpipe is closed by a ball valve and extends above the mixture in the tank. Devices are provided for making the pressure in the standpipe different from atmospheric pressure. Devices are also provided for sensing pressure in the standpipe to turn off the evaporator when the level of the mixture in the tank drops below the lower end of the standpipe.
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