PTQ Q1 2026 Issue

Cracking section

Fractionating section

Air n ccoler

Accumulator

Abs

Main fractionator

Gas compressor

Reactor

Naphtha

C-gaso

Waste water stripper

Regenerator

LCO

HDS

HCO

Riser

WWS

Slurry pump around

Figure 1 Common salt fouling and corrosion locations¹

high levels of corrosive components. Therefore, even at low levels of co-processing ratios, corrosion risks can signifi - cantly increase in these units. Salt formation and its impacts Salts commonly encountered in refinery process include CaCl 2 , MgCl 2, NaCl, NH₄Cl, NH₄HS, and amine salts. In light of the previously discussed feedstock trends, NH₄Br and amine bromide salts will soon be added to this list. These salts are water-soluble solids, and except for Ca, Mg, and Na salts, are typically formed via condensation reactions from the gaseous phase. Since salts are water-soluble, they do not dissolve in hydrocarbon fluids but instead absorb moisture and adhere to metal surfaces in a semi-solid state.

Under completely dry conditions, they may interfere with flow or hinder heat transfer, but corrosion rates remain lim - ited. However, in humid conditions, corrosion rates increase dramatically. As NH₄Cl and NH₄Br are acidic salts formed from weak bases and strong acids, they exhibit low pH values (typi- cally around 4-4.5) when dissolved. The rate of salt dep- osition is governed by the equilibrium constant (K p ), which is calculated from the partial pressures of the acid and base components. These partial pressures depend on the molar ratios and the total pressure of the system. At a given temperature, there is a threshold K p value that determines whether solid salt deposition will occur. 2 Thus, deposition is influenced by temperature, pressure, and, most critically,

Salt KP value [(P )(P )] acid NH

150

No deposition

Feedstock acid increase

140

Gasoline mode

130

Diesel maximisation

Simultaneous scenario

120

Deposition

110

n salt (s)

Figure 2 Impacts of KP constant and temperature on salt deposition

PTQ Q1 2026