Shutdown of hydrochloric acid production section

When stopping, the flow rates of hydrogen and chlorine are gradually reduced in proportion at the same time, and eventually, at a certain point, both should be stopped simultaneously. When driving the equipment, ignition is required; hydrogen should be turned on first, as chlorine cannot be ignited otherwise. Only after checking that the color of the hydrogen flame is normal should the chlorine pipeline be activated.

When shutting down the hydrochloric acid furnace (emergency shutdown), close the hydrogen valve first, then the chlorine valve

During an emergency shutdown of the hydrochloric acid furnace, the hydrogen valve should be closed first, followed by the chlorine valve. For a normal shutdown, the flow rate can be reduced first, after which both personnel should close the chlorine and hydrogen valves simultaneously; this is the procedure followed in our plant.

Some of the above mention turning off the hydrogen valve first and then the chlorine valve, while others say to turn them off simultaneously; I think the method described below is more proper. Normal shutdown: Gradually reduce the chlorine-hydrogen flow rate, and finally close the chlorine valve first, followed by the hydrogen valve (stop chlorine supply before stopping hydrogen supply). The isolation valve can be closed first, followed by the manual control valve, and finally the main pipe outlet valve. Emergency shutdown: Immediately close the chlorine cut-off valve, then close the hydrogen cut-off valve. Then close the chlorine and hydrogen control valves.

Thank you all for your advice. The information on the 5th floor is quite detailed. I would like to know what technical considerations underlie such procedures, as well as the impact of the parking order on safe production. I appreciate any guidance you can provide!

Cut off the chlorine first, then the hydrogen – remember this well, as there have been lessons from past accidents

Explain that when reducing the flow rate, we reduce the amount of hydrogen available; this way, hydrogen remains in the absorption system. When shutting down the plant, one should not close the hydrogen valve first and then the chlorine valve, as this can lead to an excess of chlorine and increase the risk of explosion

In general, an excess of hydrogen is used in hydrochloric acid production; the reason for this is well known – chlorine cannot escape. Additionally, chlorine cannot burn under normal conditions, which is why there are differences between starting up and shutting down the process. When starting up, the hydrogen valve should be opened first; once a flame is visible in the viewfinder, the chlorine valve supplying gas to the furnace should be opened immediately； (Because chlorine cannot burn, the hydrogen valve must be opened first.) When stopping the operation, the chlorine valve should be closed first, followed by the hydrogen valve; it is advisable to purge the system with nitrogen for 1–2 minutes after closing the hydrogen valve (this is very beneficial). If the hydrogen valve is closed first, hydrogen and chlorine gases that can cause explosions may form inside the synthesis furnace, and under the influence of the high temperatures, an explosion within the furnace could occur

During the startup of the hydrochloric acid production section, chlorine and hydrogen should be turned on in sequence: hydrogen is turned on first. Once hydrogen is ignited, the chlorine valve is adjusted based on the combustion situation. When stopping the system, stop the chlorine supply first and then the hydrogen supply. It is important to note that the hydrogen valve should be closed immediately after the chlorine supply is shut off quickly. Do not open the furnace door or remove the hydrogen pipeline immediately after parking, to prevent the synthesis furnace from having a mixture with air within an explosive range when the temperature inside the furnace is too high and the hydrogen concentration is high.