Ingenuity-Summer-2017

Pond Ingenuity Summer 2017 9 price, either in capital costs or as a tariff on the attached butane delivery contract. The least expensive blending process involves off-loading butane directly into an established gasoline storage tank. This uses facilities and infrastructure tank farms already have, so upfront costs are low; however, because the butane is forced from a pressurized tanker truck directly into a non-pressurized tank, a portion of the butane will bubble out and evaporate, giving a nearly immediate loss of potential revenue. The third blending option is much less expensive than the “into-truck” method, but is significantly more efficient than the least expensive option. This is the solution Pond recommended to their midstream client. The client did not have to install LPG bullet tanks or expensive infrastructure. To minimize the loss of butane, Pond designed a system that combined the butane pumped from the tankcar and the gasoline being stored in one of the tanks into a recirculation pipe with blending features. Doing so mimicked the “into-truck” blending method and decreased the amount of boil off that tends to happen in the cheapest in-tank blending option. This is largely due to the additional dwell time the butane and gasoline have while under pressure, as well as the turbulent flow, which allows additional chemical bonding time resulting in less boil off in the tank. Special consideration was also given to how to transfer the butane from the tank cars to the gasoline. Compressors are the most efficient method of off-loading, since they can do so at higher flow rates and also result in very little residual product in the tank car. However, since there is no LPG bullet tank with a vapor space to offload to, a compressor is difficult to use. Pond developed a option to use compressors with a pipeline injection using two vapor development flash tanks, which allow the use of higher flow rate compressors without a bullet tank as the target vessel. Ultimately, the client chose to use a positive displacement pump (PD pump) to off-load the tank cars. These pumps unfortunately have flowrate limitations in LPG service. If the liquid butane is pumped out of the tank car too quickly, it boils off more rapidly in the tank car, therefore decreasing efficiency and profits. The pump can also cause a vacuum in the tank car if not enough oxygen is let in, increasing the risk of implosion. Timing was also a factor in choosing a solution. There is a limit how long the client could keep the railcars on their site. The client wanted to hook up and unload a railcar within a 12-hour shift, so the pump couldn’t be so slow that it affected off-loading time. Pond worked closely with the equipment manufacturers to make sure the pumps in the client’s new system could not only work well with the butane, but also operate safely within the client’s time limits. SAFETY AND OPERATIONS Because the client’s terminal had stored only liquid up to this point, it was also imperative to address the additional operational challenges and required safety measures for handling a LPG product like butane. Just like high- pressure pneumatic testing versus hydrostatic testing, handling compressed gases can be very different than atmospheric liquids due to stored energy of the gas. Very minor actions can cause potentially catastrophic events. One of the biggest safety challenges with butane is spotting and dealing with leaks. Vapor leaks can’t be seen like liquid leaks, unless they are large enough to frost, so in addition to visual leak inspections, Pond included strategically placed gas detection systems to help identify potential safety issues. The fire protection methods also needed to be addressed, as fighting a butane fire requires a different response than gasoline fires; gasoline fires burn in place, whereas butane fires pose a high explosion risk and can result in unexpected flameups. Additional safety reviews were added to the design process and several full days were dedicated in the schedule for the client and Pond to slowly walk through the system design to review for potential hazardous operational issues and safely address them. These discussions led to slight alterations in the design and system operation that increased system safeguards to help prevent hazardous situations. In addition, process safety management (PSM), risk management plan (RMP) and additional operator training, as is typically required by agencies for these new systems, were implemented to ensure the safety of the client’s employees. Overall, butane blending is one of the best ways currently available for midstream companies to increase their profit margins. Finding a way to do it efficiently, with low up-front costs, is key to capitalizing on the opportunity. Given the options for how it can be done, companies of all sizes can find a solution that fits their financial situation and needs. By Todd M. Eldridge, PE | Program Manager, Midstream | Oil & Gas Excerpt from Pond article published in Tanks & Terminals Magazine.  Offload assembly using PD pumps  Rail offload platforms, under construction