Coal chemical industry

Coal chemical industry is the process of using coal as raw material, converting it into gas, liquid, and solid products or semi-finished products through chemical processing, and then further processing it into chemical and energy products. With the continuous reduction of world oil resources, coal chemical industry has broad prospects, and in recent years, coal chemical industry has also developed rapidly in China.

In the coal chemical industry, there are many occasions where Yokogawa pressure transmitters are used. However, compared with traditional industries, there are many working conditions where the medium is black water or grey water, with a temperature of over 200 ℃ and a pressure of over 4MPa. Due to the high temperature and high pressure, as well as the complex composition of the medium, the liquid receiving metal diaphragm (usually 316L) of the Yokogawa pressure transmitter is prone to hydrogen permeation. Hydrogen permeation refers to the permeation of hydrogen gas molecules through a metal membrane under external force, entering the sealed liquid chamber and generating bubbles (hydrogen gas accumulation). After a certain period of time, the metal isolation membrane in the sealed liquid chamber will bulge, and in severe cases, even rupture.

For the prevention of hydrogen permeation phenomenon, the industry usually uses the method of gold plating on 316L membrane. Hydrogen gas does not dissolve in gold, and the gold layer is very dense, so membrane gold plating is used as an effective barrier layer to prevent hydrogen from penetrating the membrane. However, in high-temperature and high-pressure environments such as coal chemical industry, where the medium is black water/grey water, 316L gold-plated diaphragms from various transmitter manufacturers around the world can usually only be used for 3-6 months before hydrogen permeation occurs, which has become a headache for the coal chemical industry.

In 2014, Chongqing Henghe Chuanyi Technology Department developed 316L fully gold-plated products for hydrogen permeation prevention in the coal chemical industry according to the company's requirements. The structure and process of the original gold plating were changed, and the thickness of the gold plating layer was increased. This type of product began to enter the market in October 2014. Firstly, 21 Yokogawa EJA transmitters were used in the gasification unit of Yantai Wanhua, and the anti hydrogen permeation effect was very significant.