Steam stripper /stripping

As the spent catalyst falls into the stripper, hydrocarbons are adsorbed on the catalyst surface, hydrocarbon vapors fill the catalyst pores, and the vapors entrained with the catalyst also fall into the stripper. Stripping steam, at a rate of 2 to 5 lbs per 1,000 lbs (2 kg to 5 kg per 1,000 kg,) is primarily used to remove the entrained hydrocarbons between catalyst particles. Stripping steam does not address hydrocarbon desorption and hydrocarbons filling the catalyst pores. However, reactions continue to occur in the stripper. These reactions are... 

Spent catalyst from the reactor/cyclones discharges into the stripper. Stripping steam displaces hydrocarbon vapors entrained with the catalyst and removes volatile hydrocarbons from the catalyst. 

A steam stripper, as shown in Fig. 10.1, works in the same way. The diesel-oil product drawn from the fractionator column is contaminated with gasoline. The stripping steam mixes with the diesel-oil product on the trays inside the stripper tower. The steam reduces the hydrocarbon partial pressure and thus allows more gasoline to vaporize and to escape from the liquid phase into the vapor phase. The heat of vaporization of the gasoline cannot come from the steam, because the steam (at 300°F) is colder than the diesel oil (at 500°F). The heat of vaporization must come from the diesel-oil product itself. 

Many side-stream steam strippers, of the type shown in Fig. 10.1, do not work very well. Operating personnel report that the stripping steam is not effective in removing undesirable lighter components from the stripper feed. Why could this be so ... 

In the subsequent product stripping section, the product is stripped free of benzene and water using a live steam stripper or a reboiler column. The effluent discharged from the washing area is steam-stripped to recuperate MNB. 

The other method, extraction, passes the air-solvent vapor mixture through a miniature solvent-extraction system using mineral oil as a solvent to absorb, or extract, the solvent vapor from the airstream. The mineral oil then goes to a steam stripper to strip out the solvent. The steam-solvent vapors are condensed and go to the solvent-water separator. The hot mineral oil from the stripper is chilled and goes back to the absorber where it picks up more solvent. Called mineral oil scrubber, the mineral oil is continuously recirculated through the absorber, the stripper, and the chiller. 

Each side-product liquid draw goes through a steam stripper, usually equipped with 5 or 10 trays, to prevent inclusion of more volatile hydrocarbons in the product. The side-product stripper may be reboiled for sharper separation. Optimum amounts of stripping steam will often be in the order of 2% or 3% w or more of each product rate. After stripping, the side products are cooled in the preheat train and cooled further in water or air coolers to safe storage temperatures. Heavy gas oil and residuum products often go to downstream cracking processes without cooling. 

The most prevalent stripping gases are steam and air (or nitrogen). Thousands of air strippers are used to purify contaminated groundwaters, and many steam strippers are used to purify contaminated process aqueous wastes as well as groundwaters. 

While packed steam strippers are not widely used, there is no reason why they should not be. Performance data for such strippers are limited, however. Because of the temperature levels, metal pickings would normally be specified. Kolev et al. studied chloroform stripping in a 0.40-m column using metal structured packing. Ortiz-Del Castillo et al. studied toluene stripping in a... 

Adsorbed and entrained vapors are removed from the retorted shale by steam in the spent shale stripper. Stripped shale is sent to the heat recovery section. The overhead products from the spent shale stripper are combined with the retort vapors and are further superheated with steam to reduce condensation coking and quenched with fractionator bottoms in a quench tower. 

Stripper. The same flowchart can be used as the stripper, or you can attach a heater and then a stripper to the liquid outiet from the absorber. The liquid feed to the stripper should be the liquid product from the absorber (part le), but heat it to 85°C (at 1 atm) first. The gus feed to the stripper should be pure steam, at 1 atm Use 6 stages. Be sure to put your steam (the stripping gas) on stage 6 and the liquid from the absorber should be put in above stage 1. Stripper is at 1.0 atm... 

Perhaps someone has retrofitted the stripper feed to preheat crude before it flows to the stripper. This is a good energy-saving scheme for the crude unit however, a steam stripper will not work on subcooled feed. The feed must be at its bubble point (i.e., the tower drawoff temperature). Otherwise, the steam will not be an effective stripping agent. 

Using 1,400 Ib/hr of steam to strip 7,000 B/SD of gas oil should produce a temperature drop of roughly 20°F between the gas oil feed and the stripper bottoms. This results from the heat of vaporization in the stripper originating from the gas oil itself. The steam s function is to reduce the hydrocarbon partial pressure across the stripping trays. The steam normally does not contribute much heat to the oil. Therefore, there is a linear relationship between the percent of gas oil feed vaporized and the temperature drop of the gas oil in the stripper. A 20°F temperature drop corresponds to about 12 wt% vaporized a 2°F temperature drop equates to little, if any, vaporization. 

A similar problem occurs in the amine solution regenerator or stripper (see Fig. 33.1). The H S strips out easily. Residual CO, which is more tightly boimd to the amine molecule, requires lots of trays and lots of steam to strip out. 

Steam introduced at the column bottom is used to strip a volatile impurity i from an aqueous solution introduced at the column top. Develop the following simplified form of the Kremser equation for the steam stripper ... 

Because light products must pass from the feed point up to their respective drawoff point, any intermediate stream will contain some of these lighter materials. Stream stripping (note the group of steam strippers beside the first column in Fig. 15.10) is a way to reintroduce these light materials back into the tower to continue their passage up through the column. 

A steam stripper, as shown in Fig. 13.1, works in the same way. The diesel-oil product drawn from the fractionator column is contaminated with gasoline. The stripping steam mixes with the diesel-oil product on... 

---