Concentrated sulphuric acid project

In a zinc production plant, zinc ore is heated with oxygen to produce zinc oxide, a process which releases sulphur dioxide for the production of sulphuric acid. The zinc oxide is dissolved in concentrated sulphuric acid and, through electrolysis, the zinc is recovered with a purity of over 99.99%. The sulphuric acid is stored in tanks without a bottom connection, meaning that the pumps must be suspended from the top of the tank. Plastic is not an option due to medium temperatures ranging between 80 °C and 115 °C.

IB-Pompen selected a special Super Duplex pump with heat-resistant components, offering significantly lower capital costs, shorter lead times and no need for modifications to the tank or pipework.

About this project

The benefits for the customer:

The investment is reduced by more than 60% compared with the current pumps.
Maintenance costs are yet to be determined, but a new pump already costs around 50% less than overhauling the old pumps.
Delivery time reduced from 12+ months to 4 months; parts in stock.
Pumps are fully bespoke: no modifications to the tank top or pipework are required.

Background & situation

Background
The existing pumps were supplied by an American manufacturer, and the local partner was entirely dependent on this factory. Delivery times were over 12 months for a pump and 8 to 12 months for spare parts. Due to these long delivery times, the factory was obliged to keep several pumps in stock to ensure operational reliability.

Situation
The pumps regularly broke down due to the corrosive environment. Without sulphuric acid, the process cannot run and the factory comes to a standstill. The investment in pumps was enormous and their reliability was questionable. In addition, a large number of spare pumps and parts were held in stock, which tied up a great deal of liquidity. However, a production stoppage costs even more, so the options were limited.

Problem & cause

Problem
These pumps are used in multiple applications, but their reliability is not ideal. The plant requires a minimum of 1.5 years between maintenance intervals for each application, and preferably two periods of 1.5 years without maintenance. The first period was achievable, but the second was considered too risky. Therefore, the pump was replaced after each period and sent for overhaul.

Average service life: approx. 1.5 years
Overhaul costs: > € 70,000 per pump
Purchase price of a new pump: > € 120,000 per pump
Downtime costs in the event of premature failure: impossible to estimate; spare parts and new pumps are extremely expensive and require significant lead times

Cause
1. The current pumps are being damaged by the process medium
2. The plant and supplier are not actively contributing to finding solutions

Our solution

Salvatore Robuschi pumps are suitable for pumping concentrated sulphuric acid up to a maximum temperature of 80 °C. For applications above 80 °C, we offer other makes constructed from different materials.

The selected pump fits perfectly into the tank and onto the pipework. The Super Duplex (SAF2507) material is suitable for the medium and ensures a long service life, meaning the pump will last for several maintenance cycles.

In addition to being a technically sound solution, it is important to the customer that the investment costs are only a fraction of the current ones, and that in the event of replacement or maintenance, both the pumps and the spare parts are available considerably more quickly. This makes a huge difference to the investment required for spare pumps and parts.

In the customer’s own words

FROM:

“We cannot reach the second maintenance interval and therefore have to replace the pump every 1.5 years with an expensive spare.”

TO:

“With the short lead time, we can inspect, overhaul or replace the pump in time, significantly reducing costs and downtime risk.”