U.S. refinery-sulfur production peaked in 1996

Edward J. Swain
Consultant
Houston

U.S. production and recovery of sulfur increased at an average annual rate of 1%/year between 1988 and 1997.

This growth is expected to continue through the next decade.

About 50% of U.S. sulfur production is used to produce phosphatic fertilizers, and the other 50% is used in chemically oriented businesses.

U.S. sulfur is produced or recovered from three main sources: Frasch mines, pyrites, and hydrocarbon operations. Most sulfur production before the mid-1950s was elemental sulfur from Frasch mining or sulfuric acid from pyrites. After the mid-1950s, recovered sulfur from natural gas-treating facilities and petroleum refineries played a more significant role in the production of elemental sulfur.

This article updates an earlier one (OGJ, Apr. 21, 1997, p. 71), which charts the production of sulfur during 1986-1995. This article will report U.S. sulfur production up to 1997.

The historical production of sulfur is illustrated in Fig. 1 [69,516 bytes]. During 1997, recovered elemental sulfur from refineries was at a rate of 14,329 metric tons/calendar day (mt/cd). This quantity represented 50% of the total quantity of sulfur produced in 1997. This rate, however, is slightly lower than that of 1996, when sulfur production peaked at a rate of 14,699 mt/cd.

The production of sulfur from Frasch mines is a swing source of sulfur to meet U.S. demand. In the past decade, Frasch sulfur has been slowly slipping as a primary source of U.S. sulfur.

Sulfur from natural gas

Table 1 [39,789 bytes] shows 1993-1997 sulfur produced from U.S. natural gas plants grouped by Petroleum Administration for Defense Districts (PADDs). For a map of PADDs, see OGJ, Oct. 5, 1998, p. 43.

The six states in PADD 3 produce about 70.5% of the total U.S. gas production. The large quantity of recovered elemental sulfur in combined PADDs 4 and 5 is a result of production from several large natural gas plants that treat gas from the Overthrust Belt in Wyoming, which contains high concentrations of hydrogen sulfide (H₂S).

Oil & Gas Journal reported 615 natural gas treating plants and 64 associated sulfur-recovery units (SRUs) serving the natural gas industry in the beginning of 1998 (OGJ, June 8, 1998, p. 57). The distribution of these facilities is shown in Table 2 [40,464 bytes].

The 64 SRUs have a design capacity of 10,240 mt/cd, and they recovered about 6,630 mt/cd during 1997, a utilization rate of about 65%. Installed excess capacity provides flexibility as the amount of raw-gas streams varies through the life of the gas field.

Sulfur from refineries

Sour gases produced from the refinery come from four main sources:

• Medium/high sulfur and medium/heavy crude feeds
• Hydrotreating of virgin/cracked naphtha and light virgin/cracked distillates
• Thermal processing and catalytic cracking of vacuum gas oils (VGOs) and reduced crude oils.
• Hydrodesulfurization and hydrocracking of atmospheric distillates, VGOs, and reduced crude oils.

Table 3 [43,694 bytes] shows the recovered sulfur from 1993 to 1997, grouped by PADDs. It is reasonable to expect PADD 3 to have the highest sulfur recovery capacity because it represents about 47% of the total U.S. refining operating capacity.

Sulfur recovered by U.S. refineries has increased about 33% during the past 10 years although crude runs have only increased about 11%. Table 4 [56,937 bytes] charts the past 10-year crude run history (1988-1997) with the history of recovered sulfur from refineries.

The sulfur recovery rate, expressed as metric tons of sulfur/1,000 bbl of crude, has increased about 20% over the past 10 years. The decline of the sulfur recovery rate in 1997 is puzzling. Although there was an increase in crude oil runs, poorer-quality crude oils with lower gravity and higher sulfur contents were processed. There were no major changes in processing schemes and product yields. Four of the five PADDs, however, reported a decline in sulfur recovery rate in 1997.

As of Jan. 1, 1998, 109 of the 152 U.S. refineries (72%) had sulfur recovery facilities (OGJ, Dec. 22, 1997, p. 41). These 109 refineries represent 92% of the U.S. crude distillation capacity. U.S. refineries have mostly medium-to-large crude-distillation capacities and complex downstream facilities.

Sulfur capacity in the U.S. was about 24,281 metric tons/day (mt/d) in 1998. Thus, the utilization rate in 1998 was about 59%. Excess capacity is built into the sulfur plant designs to provide operability to meet environmental demands.

Most recent U.S. projects include new sulfur-recovery units or the expansion of existing units. Recovery of sulfur from refineries will continue to be a growing source of sulfur to meet U.S. sulfur demands.

In 1997, about 14,300 mt/cd of sulfur were recovered from U.S. refineries. This represents 55.3% of the sulfur contained in crude-oil feeds.

Sulfur-recovery factors per PADD in 1997 were estimated to be:

• PADD 1, 32.3%
• PADD 2, 40.3%
• PADD 3, 65.5%
• PADD 4, 29.9%
• PADD 5, 59.5%.

These recovery factors are based on a study of crude-oil characteristics (OGJ, Oct. 5, 1998, p. 43). As more downstream units are added to upgrade oil fractions into clean-burning transportation fuels to meet EPA SOx emissions regulations, sulfur recovery in refineries is expected to increase to 60% of the contained sulfur in crudes by the year 2000.

Much of the unrecovered sulfur is found in several products: asphalt, road oils, petroleum coke, and residual fuel oil.

One of the driving forces of increased sulfur recovery in the future is the increasing sulfur content of crudes being processed by U.S refiners. In the past 10 years (1988-1997), sulfur content of crudes processed in the U.S. has been increasing at a rate of about 0.16 wt %/year. In the past 5 years, however, that rate has slowed to 0.02 wt %/year.

If the 10-year trend continues, coupled with the addition of downstream units to upgrade more heavy fractions into light, clean transportation fuels, an additional 102,000 metric tons of recovered sulfur are expected by 2000.

The following six refining companies accounted for almost 47% of the total sulfur recovered from refineries in 1997:

• Star Enterprise, 1,444 mt/cd
• Exxon Co., U.S.A., 1,216 mt/cd
• Citgo Petroleum Corp., 1,104 mt/cd
• Amoco Oil Co., 1,095 mt/cd
• Tosco Refining Co., 965 mt/cd
• Shell Oil Co., 857 mt/cd.

Prices

Frasch-sulfur and recovered-sulfur prices for the 1988-1997 period as reported by the U.S. Bureau of Mines/Geological Survey are listed in Table 5 [36,571 bytes]. In 1997, average prices increased to $36.06, from $34.11 in 1996.

Estimated 1997 sulfur sales (fob plant) varied widely. As usual, low values were found in the Rocky Mountain states (PADD 4) and the West Coast (PADD 5). Estimated sales of recovered sulfur were $36.29/mt in PADD 1, $28.39/mt in PADD 2, $30.47/mt in PADD 3, $18.94/mt in PADD 4, and $5.01/mt in PADD 5.

Imports, exports

About 2.06 million mt of elemental sulfur were imported to the U.S. in 1997. Canada and Mexico are the exporters to the U.S.

Canada is the world's largest sulfur exporter. Nearly 90% of its production is exported. Sulfur recovered from natural gas processing represents about 81.2% of total Canadian production; Canadian production was 10.20 million mt in 1997.

All sulfur production in Canada is from recovered operations because there is no Frasch mining in Canada.

Import sulfur into the U.S. from Canada during 1997 was up about 5.3% from 1996 imports. The price paid for Canadian sulfur, moreover, was down to $21.09/mt in 1997. This was a decrease of 26.2% from the 1996 price, but above an all-time low of $17.80/mt in 1993.

In 1991, the price for Canadian sulfur at the border was $55.43/ton. The majority of Canadian sulfur is recovered in Alberta and British Columbia and exported from the Port of Vancouver.

At the 1997 export price, Canadian sulfur should be stockpiling in the field at the recovery plants. Current sulfur price at Vancouver is quoted at between $35 and $38/ton, whereas quoted prices in Alberta for sulfur delivery to the U.S. ranges between $8 and $12/ton.

Sulfur imported from Mexico during 1994-1997 was from recovered sources. Once a large Frasch-sulfur producer, Mexico's last Frasch mine was closed in May 1993 as a result of high operating costs and low sulfur prices. Three other Mexican Frasch mines closed in 1992.

Production of Frasch sulfur dropped from 1.4 million mt in 1990 to 102,000 mt in 1993.

Sulfur from Mexico was $50.83/ton in 1997, an increase of $3.51/ton from 1996.

In 1997, sulfur quantities shipped to the U.S. accounted for 52% of Mexico's recovered quantity.

Sulfur from the U.S. is exported to Western Europe, South America, Africa, and the Far East. Export sulfur prices have declined over the past 2 years as a result of lower worldwide sulfur demand and competition from sulfur-producing countries like Canada, the Former Soviet Union, Poland, and Saudi Arabia.

It is doubtful that the U.S. sulfur-export market will reach 1 million tons in 1998 as it did in 1991.

The Author