Desulfurization Technology

 

Background

 

Due to the increasingly stricter regulations for deep reduction of fuel sulfur content, development of new deep desulfurization processes for liquid transport fuels has become one of the major challenges to the refining industry and to the production of hydrocarbon fuels for fuel cell applications. The sulfur compounds in the current transport fuels corresponding to the S level of 350-500 ppm (parts per million) account for only about 0.12-0.25 wt % of the fuel. The conventional hydrotreating approaches will need to increase catalyst bed volume at high-temperature and high-pressure conditions for treating 100 % of the whole fuel in order to convert the fuel mass of less than 0.25 wt %.  Planet has been exploring processes for desulfurization at low temperatures, which can effectively reduce the sulfur content in diesel fuel at low investment and operating cost to meet the needs for ultra-clean transportation fuels and for fuel cell applications.

 

In order to reduce the sulfur content in transport fuels for environmental protection purpose, US Environmental Protection Agency has issued regulations that has required the refineries to reduce the sulfur content of gasoline from a current average of 300 ppm to 30 ppm by 2006, and the sulfur content of highway diesel fuel from a current limit of 500 ppm to 15 ppm by 2006.

 

In terms of technology availability, the sulfur content in gasoline can be reduced to less than 30 ppm by current hydrotreating processes. The major problem is that the current hydrotreating technology results in high hydrogen consumption and significant reduction of octane number due to olefin saturation.  For diesel fuel, the current hydrotreating technology is difficult to reduce the sulfur content to less than 50 ppm, because the remaining sulfur compounds in current diesel fuel are the refractory sulfur compounds.  These refractory sulfur compounds are the alkyl dibenzothiophenes with one or two alkyl groups at 4- and 6-positions, which strongly inhibit hydrodesulfurization of the compounds.  Studies have shown that in order to reduce the sulfur content of the diesel fuel from 350 ppm to less than 50 ppm using the current hydrotreating technology, even with catalysis twice as active as current commercial catalysts, the reactor volume must be at least a couple of times larger than those currently used in refineries.  As is well known, the increase in volume of the high-temperature and high pressure reactor is very expensive and the increase of catalyst activity by even 50 % over existing hydrotreating catalysts is hard as the existing hydrotreating catalysts have been developed and optimized over the pass 50 years.

 

The regulation for ultra-low sulfur fuel is motivated in part by the need for using the new emission-control technologies that are sensitive to sulfur. On the other hand, ultraclean fuel is also needed for use with a fuel cell system.  The Fuel cell is one of the most promising and convenient energy conversion devices for generating electricity for both mobile vehicles and stationary power plants including residential applications. For the 6 automotive fuel cells and military fuel cells, liquid hydrocarbons (gasoline, kerosene, jet fuel or diesel) are ideal fuels due to their higher energy density, ready availability, and safety for transportation and storage. However, the liquid hydrocarbons usually contain certain sulfur compounds that are poisonous to both the shift catalysts in hydrocarbon fuel process and the electrode catalysts in fuel cell process. Thus, the sulfur compounds in the liquid hydrocarbons need to be reduced to less than 0.1 ppm.

 

Consequently, development of new deep desulfurization processes for liquid transport fuels becomes one of the major challenges to the refining industry and to the fuels for fuel cell application.

 

Planet's Introduces Ultra Low Desulfurization Technology - SRU-15

The technology is designed to treat the diesel fuel produced from a distillation unit to reduce Sulfur compounds from levels of 60-100 ppm to less than 15 ppm to meet current ULSD standards.

 

This technology development is designed for the reduction of Sulfur compounds in Transmix and other high Sulfur fuel streams. In keeping with the company’s mantra to create new and innovative ways to utilize available resources, it was determined there was need for a way to reduce Sulfur compounds in off spec diesel fuel to meet the latest federally mandated regulations for ULSD (Ultra Low Sulfur Diesel).

 

Transmix is a readily available source of feedstock for use in the production of diesel fuel and naptha. It is a by-product of several industries related to the production, storage and transportation of hydrocarbon based products, including the following:

  • Pipeline gas/diesel transmix

  • Cross-dumps of gas and diesel

  • Barge Strippings

  • Petroleum and chemical site/tank cleaning and remediation

  • Interface and purge of non-compatible products in tankers, pipelines, and tankage

  • Re-refining of red-dye product

Transmix is a costly by-product of these processes and results in a cross mixture of products that must be re-refined at the refinery, which is wasteful and displaces refinery volume for incoming crude oil, or processed into diesel and naptha in smaller distillation plants. Because Transmix is typically high in Sulfur compounds it becoming increasingly difficult for the Transmix processors to produce diesel fuel to meet ULSD standards of less than 15 ppm.

 

Recognizing this problem and the opportunity it presented, Planet committed in April 2010 to develop a solution utilizing a chemistry / technology based process. Further, the company’s management challenged its team to fast-track the project from conception and laboratory testing to an operating prototype in 90 days and dedicated a budget of $450,000 to conceptualize, prove, design, build, and test, the technology. The system incorporates a design that can be pre-fabricated in modules for cost effective manufacture and transportation and readily “plugs in” to the client’s distillation system.

 

As previously stated in a press release dated June 23 2010, Planet has formally partnered with Lerro Processing LP to market the technology and through this partnership, an agreement has been established with an independent Transmix processor to install and operate the first SRU-15 as a beta site for testing. The terms of the agreement include a contract with the company to pay a per gallon treatment price for fuel processed through the system from the date it begins operation. Planet will own, maintain, and operate the system through the limited partnership and plans are to market the concept to a large number of potential customers facing the dilemma of meeting ULSD standards.

 

The process is patentable and patent applications will be initiated following the appropriate testing and documentation phase of the project.