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Byproduct Stock PhotosThe 27,000 barrel-per-day Denver refinery of Ultramar Diamond Shamrock (UDS) suffered from low profitability and low vitality efficiency. One indicator of those issues was the large flare that burned virtually constantly.

Many refineries, just like the UDS refinery, have waste gases which might be routed to a gasoline header. When the amount of waste gas exceeds the necessities of the refinery furnaces and boilers, the surplus is flared. A small fraction of the waste gas is propane (C3) or heavier-about four% by volume.

If it may be recovered, the refinery can sell the C3+ as both liquefied petroleum fuel (LPG) or gasoline. However, at the low partial strain current in the gasoline header, the C3+ will not condense at ambient temperature and thus can’t be recovered. Calculations show that about half of the C3+ will be condensed by chilling one of many waste gas streams to -20°F (-29°C).

The refinery convened a crew of consultants to determine the best answer. The group considered numerous approaches before deciding on the waste-heat-powered absorption refrigeration unit (ARU). The gaseous effluent from the reformer proved to be a super goal for applying the refrigeration. Chilling that stream to 0°F at nominal refinery summer season working situations recovers 200 barrels per day of liquid C3+, which is more than enough to extinguish the flare.

Solving the problem with a waste-heat-powered ARU also requires an appropriate supply of waste heat. A great supply was discovered at the reformer. The cooling curve showed that the required 6 million Btu/hr (1758 kW) of waste heat may very well be extracted from the goal stream by cooling it from 290°F to 260°F.

The ARU is integrated into the refinery course of and makes use of enhanced, highly compact heat and mass exchangers.


The ARU is recovering 200 barrels per day of LPG and has recovered as a lot as 315 barrels-per-day. The unit also achieves the design chilling temperature of 0°F. It is all the time operated to achieve the bottom potential temperature and routinely achieves 0°F during the winter.

It’s now very uncommon that any fuel is launched from the refinery fuel header into the flare header. The typical LPG recovery is at least 50% more than what was previously flared, so it’s normally necessary to import natural gas to make up the deficit. The recovered liquid falls 60% inside the gasoline fraction and 40% in the LPG fraction. Thus, it may be considered that the newly imported natural gasoline is being converted into gasoline and LPG at effectively one hundred% thermal effectivity, with wonderful financial value added.

An integral a part of the mission is the associated discount in regulated emissions. Recovering salable hydrocarbon products from the refinery fuel gas system considerably reduces the quantity of flared fuel fuel. This not solely saves money and reduces wasted energy, but also lowers emissions from the refinery flare. Additionally, reducing the flared fuel fuel minimizes the dimensions of the flare; large flares from refineries are sometimes a supply of complaint amongst neighboring communities.

The Affiliation of Vitality Engineers designated this project “Environmental Mission of the Year for 1998.

The ARU diminished emissions at the plant by: 9.91 tons/yr CO; 1.82 tons/yr NOx; 0.07 tons/yr PM10; 1.5t/yr VOC and; 7,741 t/yr CO2.


– Payback of lower than 2 years
– Recovers 2.1 million gallons of gasoline and liquefied petroleum gas a yr
– Decreases annual CO2 emissions by 10,000 tons
– Realizes elevated profit of $900,000

Large Refinery

An rising DOE-sponsored technology has been deployed. The technology recovers light ends from a catalytic reformer plant using waste heat powered ammonia absorption refrigeration. It’s deployed at the 27,000 bpd Bloomfield, New Mexico refinery of Western Refining Firm.

The expertise recovers roughly 50,000 barrels per 12 months of liquefied petroleum fuel that was previously being flared. The elimination of the flare also reduces CO2 emissions by 17,000 tons per yr, plus tons per year reductions in NOx, CO, and VOCs. The waste heat is supplied directly to the absorption unit from the Unifiner effluent. The added cooling of that stream relieves a bottleneck formerly current attributable to restricted availability of cooling water. The 350°F Unifiner effluent is cooled to 260°F. The catalytic reformer vent fuel is instantly chilled to minus 25°F, and the FCC column overhead reflux is chilled by 25°F glycol.

Lastly accomplished in 2008, this mission can now be thought-about a hit: it is each worthwhile and highly helpful to the surroundings. The capabilities of directly-integrated waste-heat powered ammonia absorption refrigeration and their benefits to the refining industry have been demonstrated.

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