Method for flexibly controlling the use of hydrochloric acid from chemical production

The method as claimed in claim 5, wherein the multistage continuous neutralization (G) of hydrochloric acid having an HCl concentration of at least 10% by weight and having a volume flow of at least 1 m3/h, is carried out to a target pH in the range from 3 to 9, by means of the following steps:

• A) introduction of the hydrochloric acid to be neutralized and a proportion of 95%, preferably at least 99%, of the stoichiometrically required alkali metal hydroxide (5) in a first stage into a volume flow of neutralized hydrochloric acid, which is recirculated, cooled, from the second stage, subsequent mixing of the streams and full reaction of the primary reaction mixture in a neutralization and resident zone, where the pH of the stream coming from the first stage has a pH of at least 1 and the volume flow which is recirculated cooled from the second stage corresponds to at least 3 times the hydrochloric acid volume flow which is fed into the first stage,
• B) transfer of the volume flow from the first stage into a neutralization zone of the second neutralization stage, further setting of the pH of the secondary reaction mixture to a value of preferably pH 3 by addition of alkali metal hydroxide or hydrochloric acid in a secondary circuit, where this secondary circuit results from offtake of a substream from the main stream to be cooled of the second reaction stage and the ratio of the volume flow of the neutralized hydrochloric acid to the volume flow of the substream is at least 10:1 and, after cooling of the main stream in the second stage, recirculation of a further larger substream of the secondary reaction mixture of the second stage into the first neutralization stage for carrying out the reaction A),
• C) introduction of a further substream from the secondary reaction mixture of the second stage into a neutralization zone of a third neutralization stage, further setting of the pH of the tertiary reaction mixture in the third neutralization stage to a pH in the range from pH 3 to pH 9 by addition of alkali metal hydroxide or hydrochloric acid in a further secondary circuit which is connected to the neutralization zone, where this secondary circuit consists of a smaller substream of the main stream of the reaction mixture exiting from the third stage, which is passed to cooling, and the larger substream of the main stream exiting from the third stage is, after cooling, passed to final quality control for temperature and pH monitoring and, if this cooled stream of the tertiary reaction mixture satisfies the quality criteria, this stream 13 is taken off as product stream, or otherwise the tertiary reaction mixture is to be introduced as recycle stream into the third stage for further pH adjustment.