Refinery Process Solutions · Case study

Northshore CC827495: Crude calcium removal at a lower dose ratio

A refinery evaluated Northshore CC827495 on a high-calcium crude in its existing electrostatic desalter. Seven paired samples showed 70.8–76.3% calcium removal, averaging 73%, at an applied ratio below the technical agreement’s range.

Request Full Case Study

Operating context and objective

A refinery introduced a crude containing 11.5–12.8 mg/kg calcium to an atmospheric–vacuum unit. The plant wanted to remove the calcium in its existing electrostatic desalter, without adding equipment or changing the desalting duty. The technical agreement for the decalcification program provided for a chemical dose of 3.5–5 times the calcium content of the crude.

Organically bound calcium does not transfer to wash water by simple partitioning. A decalcifier converts it to a water-soluble salt within the desalter residence time so that the calcium can leave with the brine rather than continue to the preheat train, furnace and FCC unit.

Product and monitored application

Northshore CC827495 was metered through the existing metal-removal injection facility into the wash-water line ahead of the second-stage desalter vessel. Treatment began on 21 May 2020 at 30 ppm on crude, about 2.5 times the seven-sample mean feed calcium.

Operating conditions were left as found: desalter temperature 125–135 °C, interface 30–50%, wash water at pH 9 with staged brine recycle, and mixing-valve pressure drop of 35–60 kPa. From 9 to 30 June, the plant laboratory collected seven paired inlet and outlet crude samples and analysed calcium in both.

Reported results

Calcium removal was consistent across all seven sample pairs. Removal ranged from 70.8% to 76.3% and averaged 73%. Feed calcium of 11.5–12.8 mg/kg was reduced to 2.8–3.7 mg/kg; no sample fell below 70% removal.

Calcium removal across seven paired samples

Average 73%

0%70.8–76.3% reported range100%

Figure 1. Whole reported range over three weeks at an unchanged 30 ppm dose. Plant laboratory data, June 2020.

The result was achieved below the agreement’s dose-ratio range. The report’s data section states the ratio as 2× and its conclusion as 2.5×. Using 30 ppm and the seven-sample mean feed calcium of 12.1 mg/kg gives approximately 2.5×; the webpage and summary PDF use that calculated ratio and preserve the discrepancy in the detailed account.

Reported trial conditions and outcomes
Measure	Reported value
Crude rate	370–380 t/h, about 21% above the agreement’s 310 t/h basis
Wash water	11–13 t/h per stage, below the contracted 14–16 t/h
Desalted-crude salt	1.1–2.6 mg/L, averaging 1.82 mg/L
Reported side effects	None on unit operation, corrosion control, product properties or downstream units

The customer recorded steady desalting during the trial. The report does not provide a pre-trial salt baseline, so the salt result describes conditions during treatment rather than a before-and-after improvement.

Operational value

The source report presents the result in process terms and provides no monetary figure. Under the reported conditions, the program reduced the average calcium leaving the desalter to 3.3 mg/kg, compared with an average 12.1 mg/kg in the feed, while using the existing injection point and operating at an elevated crude rate.

For another refinery, an economic review can connect calcium removal with desalter stability, furnace and heat-exchanger fouling, and FCC catalyst condition. Those are evaluation inputs; this trial report does not quantify savings in those areas.

Applying the findings

Use paired inlet and outlet samples to evaluate calcium removal, and record crude calcium, chemical dose, wash-water rate, interface, temperature and mixing-valve pressure drop with each sample. Express the chemical rate both in ppm on crude and as a ratio to measured feed calcium so the treatment can be compared across crude slates.

Establish a pre-trial salt baseline when desalting performance is part of the evaluation. This case confirms the salt level observed during treatment, but the missing baseline prevents a direct claim about improvement.

Discuss a similar application

Request the full illustrated case study and share your crude-calcium range, desalter configuration and current treatment ratio. Cestoil can review the application and propose a paired-sampling plan for your crude.