Closed-loop circulating water heating system and method thereof

Abstract

The invention discloses a closed-loop circulating water heating system and a method thereof, which are applied to the field of preparation of ammonia-air mixed gas and are used for improving the production safety of dilute nitric acid. The system comprises a circulating water booster pump, an evaporator, an absorption tower, a heat exchange tower layer, a shell-and-tube heat exchanger and a low-pressure steam pipe network, the circulating water booster pump is installed at the outer bottom of the absorption tower, connected with the shell-and-tube heat exchanger, the evaporator and the absorption tower and used for achieving closed-loop water circulation, and the low-pressure steam pipe network is installed in the shell-and-tube heat exchanger. The heat exchange tower layer is arranged in the absorption tower and is used for realizing water vapor heat exchange, and the shell-and-tube heat exchanger is communicated with the low-pressure steam pipe network and is used for increasing the closed cycle heat temperature. The method comprises the steps that the temperature corresponding to the closed-loop circulating water is controlled based on the preset control temperature; and the actual evaporation demand quantity is obtained, and the closed-loop circulating water is heated to the preset temperature based on the actual evaporation demand quantity and the temperature.

Description

technical field [0001] The invention relates to the field of preparation of ammonia-air mixed gas, in particular to a closed-circuit circulating water heating system and a method thereof. Background technique [0002] At present, dilute nitric acid production mostly adopts double-pressurized liquid ammonia evaporation technology. Preparation is carried out with an ammonia-air mixture. The preparation process is as follows: the raw material liquid ammonia from the boundary area is evaporated (maintain the evaporation pressure at 0.52MPa·G), overheated (maintain the temperature of gas ammonia at 100°C-120°C), and then filtered through the gas ammonia filter to remove impurities and enter Ammonia Air Mixer. The process air enters the axial flow compressor after passing through the four-stage filter. The compressed air from the axial flow compressor is about 0.35MPa·G, 180°C-230°C, divided into two streams of primary air and secondary air; the primary air removes ammonia from...

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Problems solved by technology

[0003] In the production process of double pressurized nitric acid, the evaporation of liquid ammonia is divided into internal closed-circuit circulating water and external circulating water introduced from the outside for heat exchange and evaporation. The internal circulating water system absorbs nitrogen dioxide in the absorption tower (designed with 40 layers of absorption pedals) Nitric acid is generated, and the reaction releases a large amount of heat at the same time. The closed-circuit circulating water is used to cool down and exchange the reaction heat for use by the evaporator. However, since the closed-circuit circulating water is designed on the 16th to 40th tray of the tower, the heat energy of the compressed air is insufficient at the beginning of the start-up, resulting in cold The temperature of the closed-circuit circulating water in weather is low, which is not enough to meet the gas ammonia volume and the preparation of ammonia-air mixture in the early stage of starting up, resulting in a large amount of gas ammonia being directly vented, which increases the cost, pollutes the environment, and makes it difficult to maintain normal ignition operation. In severe cases, the system direct shutdown

[0004] Therefore, in the existing dilute nitric acid production process, there is a problem of low safety of dilute nitric acid production due to insufficient heat energy at the initial start-up stage

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