Measuring method and measuring device of small amount of ammonia in gas

Abstract

The invention discloses a measuring method and a measuring device of small amount of ammonia in gas. The measuring method comprises the following steps of S1. switching on a sampling valve, and recording the initial flow V0 of gas to be detected; S2. introducing the gas to be detected into mixed liquid of sulfuric acid standard liquid and an indicator so as to react the small amount of ammonia in gas and the sulfuric acid standard liquid; S3. when the color of the mixed liquid is changed, stopping introducing the gas to be detected, and recording the initial flow V2 of the gas to be detected; and S4. obtaining the ammonia content in the gas to be detected according to the differential flow V1-V0 of the gas to be detected and the sulfuric acid standard liquid. According to the measuring method provided by the invention, the measuring device and a sampling pipeline are directly connected on the scene, and the small amount of ammonia is subjected to quantitative reaction in the sample gas, so that the ammonia content is directly calculated; the limitation of the environment temperature does not exist, the problem that the environment temperature cannot be measured as the requirement on the measuring environment temperature is rigor is avoided, and the analysis errors which are caused by the multiple analysis procedure steps of a neutralization titration method and particularly exist in the procedures such as the transfer, washing and titration of absorption liquid can be avoided.

Description

technical field [0001] The invention relates to the technical field of chemical analysis and sampling, in particular to a method and device for measuring trace amounts of ammonia in gas. Background technique [0002] In the process of coal-to-methanol production, accurate analysis of trace amounts of ammonia in the gas is very important. Poor control of ammonia exceeding the target will cause poisoning of the synthesis catalyst and unqualified methanol products (such as odor of methanol, excessive trimethylamine, etc.). At present, there are many mature and reliable methods for the analysis of constant ammonia in the gas in the chemical production industry, such as the Lanshu instrument method, the Austenitic gas instrument method, the pipe method, the acid-base neutralization method, the chromatography method, and the benzene method. for selection and adoption. There is no standard method for the analysis of trace ammonia (10-100ppm) in the synthesis gas and fresh gas of t...

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Problems solved by technology

[0012] The advantage of this method is that it can measure the trace amount of ammonia above 20ppm in the gas. It has a wide measurement range and good expansibility. According to the ammonia content, it can analyze the lower content by controlling the sampling amount, sampling time or adjusting the concentration of the standard solution. The purpose of ammonia, but there are the following disadvantages: first, the analysis is cumbersome and cannot be completed on site; second, there are many links in the analysis process, especially in the absorption liquid transfer, flushing, titration and other links that inevitably cause analysis errors; third, for In the field of coal chemical industry that uses coal as raw material, especially coal-to-methanol fresh gas and synthesis gas, etc., because their composition also contains trace amounts of hydrogen chloride, hydrogen sulfide and other gases, the above-mentioned methods and instruments are used in the sampling process through wet gas flowmeters. Cause corrosion, reduce its service life or damage, and at the same time, hydrogen sulfide will pollute the environment and damage the health of operators; Fourth, there is no buffer device when sampling and absorbing in this method, and the sampling process speed on the high-pressure pipeline needs to be strictly controlled. Be careful that it is easy to cause the sulfuric acid solution in the absorption bottle to splash and cause sampling failure or injury to the staff. In addition, the sulfuric acid solution may enter the wet gas flowmeter and be damaged.

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