2 minute read
VOC for off shore loading
PROPOSED AMENDMENT WILL FAN OFFSHORE VOC SYSTEM INTEREST
Wärtsilä Gas Solutions is looking to extend the commercial application of its volatile organic compound (VOC) recovery system to PSVs serving crude oil tankers loading at SBMs, Sea Islands or terminals
This solution has been developed in cooperation with a Norwegian company, Vaholmen VOC Recovery A/S, which holds the patent to the concept.
The solution involves the installation of a VOC system aboard a platform supply vessel to absorb up to 100% of VOC emissions generated during the loading of crude oil from an offshore platform onto a very large crude carrier (VLCC) while the PSV operates in DP2 mode.
The product concept will remove all VOC emissions during loading and the VOC recovery vessel will be able to serve several VLCCs before unloading the liquified VOC (LVOC) onshore.
The solution offers significant greenhouse gas emission savings, as the loading stage accounts for 70% of total VOC emissions from ships. Using a VOC system for loadings would yield net CO2 equivalent (CO2e) savings of 1,200-1,500 metric tonnes per loading of a VLCC.
One of the key advantages of using a VOC recovery system installed upon a PSV for loadings is that the utilisation rate for the equipment could be constant. “You can imagine that a single PSV vessel serving 200+ VLCC loadings per year could generate tremendous total savings,” Hans Jakob Buvarp General Manager, Sales at Wärtsilä Gas Solutions noted.
Precise calculations are complicated by the fluctuating oil price and different carbon tax assumptions, but at US$70/ barrel and a CO2 tax of US$50/tonne, the system would generate income to cover roughly half of the cost of this vessel per year. Even excluding the carbon tax, the additional annual income from LVOC recovery would come close to US$40 million.
Although the first contract for the system has not been concluded, negotiations with interested parties in several countries are ongoing, Buvarp noted.
The system is also robust. Buvarp noted that Wärtsilä have good operational data for its VOC plant installations aboard shuttle tankers, where the company had deployed the system aboard over 10 shuttle tankers operating in the challenging conditions of the Norwegian Continental Shelf.
“One VOC plant built in 2003 is now operating on a relatively new shuttle tanker after having been retrofitted in 2015. Another of the plants built in the early 2000s is now planned to be installed on a newer shuttle tanker. It seems the operating life of these plants are in the range of 30 to 40 years.”
Technical Solution
The solution uses Wartsila Gas Systems' existing VOC technology, which has been successfully deployed.
The solution for offshore loading involves the deployment of a PSV equipped with a VOC system. The system is connected by hose to the vapour connection on the manifold of the VLCC during loading. The VLCC connection features a blind flange, while the PSV connection features a quick release assembly.
Once the connection is made, the VOC is routed through the VOC recovery system, which uses a two-stage condensation process. Following the removal of the heavier fractions during the first stage, a second stage condenses medium fractions (from propane to hexane) into a liquefied VOC stage.
The light fractions of the VOC along with some vaporized
8 Using a VOC
