1200
300 200 100 500 400 600 700
WASA MDFI
1000
y = 2.3838x + 28.288 R = 0.9913
800
600
y = 1.9865x + 28.288 R = 0.9913
y = 3.7016x + 305.58 R = 0.9783
400
200
0
300 0 In neum R 453 WASA treat rate + constant 100 ppm wt In neum R 309 MDFI, mg/kg 0 200 250 100 150 50
0
100
200
300
400
500
600
Low temperature additive content, ppm
a 78% increase in the electrical conductivity of ULSD (see Figure 3a). The other two SDAs (supplier B, additive A and supplier C) show a 76% and 119% increase, respectively. Winter diesel from Figure 3b responds to 3.5 ppm SDAs as follows: supplier A additive causes a 120% increase in conductivity; and with supplier B, additive A and additive B provide 108% and 113%, respectively. In analysing the win- ter diesel fuel response, it was noted that both types (a and Figure 4 Influence of low temperature improving additives (WASA and MDFI) on electrical conductivity of winter diesel fuel b) of winter grades untreated with SDA from Figure 3 reveal unexpectedly very high electrical conductivity of 242 pS/m for fuel (b) and 334 pS/m for fuel (a) against 0-2 pS/m for the summer grade, which is above the required minimum of 150 pS/m. Thus, there is no need to insert conductivity-improving additives into these winter grade diesel fuels. Moreover, the SDA response is worse for winter diesel than for the It is possible that polymeric material, presented in WASA, could be a reason for faster static charge dissipation
summer grade. For fuel (a), the electrical conductivity increase for dosing 3.0 ppm SDA is 262 pS/m for supplier A, 254 pS/m for supplier B, additive A, and 397 pS/m for supplier C, respectively. Using the slope (see Figure 2) of conductivity increase for summer grade diesel fuel of the same suppliers, and bearing in mind that winter diesel pos- sesses 3.0 ppm SDA, the conductivity increase for winter grades should result in a greater increase as follows: 429 pS/m for supplier A, 431 pS/m for supplier B, additive A, and 513 pS/m for supplier C, respectively. Figure 3 shows that the same inhibition of SDA response is seen by the other winter grade diesel fuel (b), meaning that winter grade diesel fuel contains a component or an additive, revealing an antagonistic effect towards SDA performance in fuel. Noting the significant electrical charge dissipate performance of ultra-low sulphur winter diesel fuel (without antistatic additive) compared to the summer grade (again without antistatic additive) warrants an inves - tigation into the reason for the difference. One of the dif- ferences between the two grades is that the winter grade consists of more light hydrotreated gasoil (LHTGO). Winter grades contain 35-40% LHTGO, while sum- mer grades include only 10-15% LHTGO. This difference does not seem to be the cause, as both light and heavy hydrotreated gasoils reveal 0-2 pS/m electrical conductivity, Figure 5 WASA positive effect over electrical conductivity of winter diesel fuel
350
208 214 212 210 216 218 220 222 224 226
Supplier A, 1 ppm additive Supplier A, 1.5 ppm additive Supplier B, 1.5 ppm additive A
300
250
200
150
100
0
100
200
300
400
500
600
0
100
200 300
400
500
600
700
(a)
(b)
Storage time, h
Storage time, h
Figure 6 Electrical conductivity decrease with time of winter (containing WASA and MDFI) diesel fuels without (a) and with (b) different static dissipator
66
PTQ Q2 2023
www.digitalrefining.com
Powered by FlippingBook