A low-pressure exhaust steam recovery and utilization system

Abstract

The invention relates to a low-pressure exhausted steam recycling system. The system comprises a low-pressure vessel, wherein one or more heat exchangers are arranged inside the low-pressure vessel; excess low-pressure exhausted steam in a dilution tank enters the low-pressure vessel via a low-pressure exhausted steam pipe and is condensed on the surface of a heat exchanger so as to transfer heat to a low-temperature material in an inner pipe of the heat exchanger; red-mud washing low-temperature water is conveyed into the heat exchanger by a red-mud washing low-temperature pump through a red-mud washing low-temperature water pipe, and red-mud washing high-temperature hot water heated to 95 DEG C enters a red-mud washing hot water tank through a red-mud washing high-temperature water pipe; a seed precipitation spent liquor pump conveys seed precipitation spent liquor to the heat exchanger via a pre-heat-exchange seed precipitation spent liquor pipe, a plate type heat exchanger and a refined liquor cooling outlet seed precipitation spent liquor pipe, and the heated seed precipitation spent liquor enters an evaporation stock solution tank via a preheated seed precipitation spent liquor pipe; and low-pressure exhausted steam condensate water is conveyed into the red-mud washing hot water tank via a condensate water pipe. With the low-pressure exhausted steam recycling system provided by the invention, a large amount of heat and water steam can be recovered by an alumina plant every year, so that significant economic benefits and social benefits are obtained.

Description

technical field [0001] The invention relates to a recovery and utilization technology and system of low-pressure exhaust steam, in particular to the recovery and utilization of low-pressure exhaust steam in a Bayer process dissolution dilution tank in alumina production. Background technique [0002] In the production of alumina plants, red mud washing liquid is generally used (some factories also use aluminum hydroxide washing liquid in addition to red mud washing liquid) to dilute the Bayer process to dissolve ore pulp, and this operation is completed in the dilution tank. The temperature of the dissolved pulp is generally 120°C to 140°C, and the temperature of the red mud washing solution is generally 92°C to 98°C. The temperature of the red mud washing solution and the stripping pulp is about 106°C after mixing under normal pressure. Because the mass ratio of dissolved pulp and red mud washing solution is approximately 1.3-1.8:1, the red mud washing solution cannot comp...

AI Technical Summary

Problems solved by technology

Especially at the end of each indirect heating dissolution unit’s operating cycle, due to the reduced heat transfer capacity of the heat exchanger due to fouling, the amount of exhaust steam discharged to the atmosphere is greater

The exhausted steam discharged to the atmosphere not only takes away a lot of heat, but also the exhausted steam contains alkali, which is a hidden danger to personal safety and equipment corrosion, pollutes the environment, and causes waste of water resources

It is relatively easy to recover low-pressure exhaust gas, but it is difficult to utilize it

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