Q&A

(2012) Question 19: Since API-932 (Waterwash Best Practices) was published, what has been the impact on reactor effluent air cooler washwater system design and reliability? Are there any active or ongoing studies to improve waterwash systems, in addition to API-932?

The question of issues associated with waterwash has been discussed since the API-932 was issued. This first slide gives a little chronology of some of the documents.

(2012) Question 20: What is the industry experience with managing cracked feedstocks to avoid hydrotreater problems such as fouling, and pressure drop?

Some of the mitigation options can be summarized in four areas. The first is feed logistics. We would say that if you are going to handle this, you need to do as much direct feeding as possible.

(2012) Question 21: High pressure strippers are an option for controlling VOCs in process condensate and managing export steam quality in a steam methane reformer hydrogen plant. What types of pH controls are being used?

Most hydrogen plants take the process condensate, send it to a deaerator to clean it up, and then reuse that condensate while mixing it with some boiler feedwater internally. There are configurations that have high pressure strippers where they will bring in some steam and do some initial stripping.

(2012) Question 22: What preventative maintenance program is applied to safety instrumented systems on a steam methane reformer that are Safety Integrity Level (SIL) rated?

Safety instrumented systems (SIS), as defined by ANSI/ISA-84.00.01-2004 Part 1(IEC-61511-1 Mod), are required to have components functionally tested and/or replaced/ refurbished under preventative maintenance (PM) to provide the reliability required to have a Safety Integrity Level (SIL) rating. SIL-rated safety systems are often required when a greater degree of protection layers is required then that offered by standard design.

(2012) Question 23: What are some options for increasing the cetane index (CI) of diesel to more easily meet export market requirements?

Cetane improvement chemistry mechanisms available to us are aromatic saturation and naphthenic ring opening (hydrocracking), both of which allow us to further take advantage of low-cost hydrogen to provide cetane upgrades and liquid volume gains.

(2012) Question 41: Have the panel members considered 15% ethanol (E15) gasoline blending?

My first slide shows a little background. The EPA administers the Renewable Fuel Standard program that has volume requirements for renewable fuels.

(2012) Question 42: What options are available to produce on-spec jet fuel from high total acid number (TAN) sources? What impacts these choices?

Regarding the conventional hydrotreating, I do not think high TAN would be an issue; but if you try to caustic-treat high TAN material, you will end up with what amounts to be the equivalent of lye soap. So anywhere you want oil and water separation to take place, the soap components may cause rag layers and carryover.

(2012) Question 43: In reforming units, what equipment could be susceptible to high temperature hydrogen attack (HTHA)? How are panelists approaching evaluation and replacement of equipment that could be susceptible to HTHA?

First, a little background: API 941 discusses high temperature hydrogen attack. At low temperatures, less than about 430°F, carbon steel has been used successfully up to 10,000 psi. But with elevated temperatures, the molecular hydrogen will dissociate into atomic hydrogen, which can readily enter and diffuse into the steel.

(2012) Question 45: What is the maximum allowable limit for the iron content of a reforming catalyst? Is this limit the same for semi-regenerative and continuously-regenerative catalysts?

We have seen that the maximum allowable iron on catalyst cannot be reduced to a simple number. Historically, about 3,000 wppm is the level at which we see yield start to suffer, but not every wppm of iron has the same impact on the unit. Iron deposited on the surface of the catalyst, usually from corrosion-related byproducts, tends to have less of an impact on the overall performance.

(2012) Question 46: Are refiners modifying the operating conditions in reforming units, for example, chloride on catalyst, in order to capture margin differences between natural gas, used as fuel, and liquid products?

I will start with a bit of review of some reactions, and then I will get into a couple of examples of what we have done at HollyFrontier. Of course, the downside to reforming is that the liquid product has less volume than the feed to the unit due to physical laws inherent to the chemical reactions. First, the high-octane product will have a higher density than the feed; and second, some portion of the feed will be cracked to LPGs and fuel gas in the process.

Find the answer to your technical question in AFPM's extensive Q&A database.

Q&A