Why is high-purity water used in ethylene plants?

Be more specific – which part of the ethylene plant?

Of course, it is used for the steam drums of the cracking furnace and the waste heat boilers. The high-purity water mentioned by the original poster refers to the boiler feed water in the ethylene plant.

With such high temperatures, if high-purity water is not used, the steam drum is prone to scaling. Once scaled, the heat exchange efficiency declines, which makes it dangerous as heat cannot be removed in a timely manner

The drum must use deoxygenated desalinated water; the steam produced by the pyrolysis furnace is used to drive the turbine, and high-purity water is not required, as this can easily lead to scaling and corrosion of the turbine blades

Is high-purity water deoxygenated water? Ask questions.

Ethylene plants require high-pressure and ultra-high-pressure steam, and high-purity water is essential for the boilers used in such systems. The poster can refer to the **standards** for boilers, which contain detailed regulations.

This high-purity water is water obtained by further deoxygenating second-stage desalinated water

I feel the same way – for steam turbines, waste boilers should use second-stage deionized water along with a chemical dosing system. And to save costs, ordinary boilers often do not use any chemicals.

Desalinated water → Deoxygenation → Phosphate addition → pH adjustment → SS generation in the drum → Turbine → Reheater → Purified water unit → Desalinated water. 1. Phosphate addition to boiler feed water: Addition point: at the inlet of the boiler feed water line for each drum boiler. Function: 1. It serves to prevent scaling ； 2. Form a protective film of iron phosphate on the boiler metal to prevent corrosion. 2. Injection of deoxidizer into the deoxidizer: Injection point: on the pipeline between the deoxidizer tank and the deoxidization head. Function: Deoxygenation. 3. Addition of neutralizing agent in the deoxidizer; Injection point: on the boiler feedwater outlet line of the deoxidizer. Function: To neutralize CO2 in the boiler feedwater and adjust its pH. Turbines have high requirements regarding water quality; once scaling occurs in the turbines, their efficiency decreases, and full-load operation of the equipment cannot be ensured. To maintain good water quality, the drum also needs to be drained regularly to prevent the accumulation of calcium, magnesium ions, and other impurities within it