Takahax process

Tait equation Takadiastase Takagi reagent Takahax process Takanelite Takasweet Takatherm... 

Hiperion A process for removing hydrogen sulfide and organic sulfur compounds from hydrocarbons. Similar to the Takahax process but using a solution of chelated iron and naphthaquinone. The elemental sulfur produced is removed by filtration. Licensed by Ultrasystems, CA. 

In this sector, the Stretford Process offered by British Gas Corp. and the Takahax Process of Tokyo Gas Cie. Ltd. have prevailed over the older processes of this type such as Giammarco-Vetrocoke, Ferrox, Thylox and others [2.4]. A certain preference for the former can be observed in the USA and Europe, whereas the latter is more frequently used in Japan. The Takahax process, which exists in 4 versions in combination with the Hirohax process developed by Nippon Steel, is specifically tailored to coke oven gas cleaning and may therefore be left unconsidered here. 

Perox Process, 762 Takahax Process, 765 Stretford Process, 769 Hiperion Process, 794 Sulfolin Process, 797 Unisulf Process, 802... 

This section reviews three groups of processes each with two representatives. The first group contains the Perox and Takahax processes, which utilize the liquid redox potential of... 

The first liquid redox quinone process was the Perox process, developed in Germany in 1950. It employs p-benzoquinone, and was a forerunner to other quinone based processes. The second process discussed in this section is the naphthoquinone-based Takahax process, developed in Japan by the Tokyo Gas Company. This process, which achieved significant market penetration in Japan, was introduced in the same time frame as the Svetford process, and constituted an attempt to eliminate the use of heavy metals that is characteristic of Stretford type processes. 

The Takahax process was developed by Hasebe (1970) of the Tokyo Gas Company Ltd., to replace the Thylox and Giammarco-Vetrocoke processes (Swaim, 1972). The first commercial application of the Takahax process was to desulfurize coal gas in a revamped 1.4 MMscfd Thylox plant operated by Kamaishi Gas. About a hundred Takahax units were in operation at one time in Japan, primarily in gas works, steel plants, and chemical plants. The process is still extensively used in Japan for the desulfurization of coke oven gas. 

The Takahax process utilizes naphthoquinone (NQ) compounds as the oxygen carrier. The preferred solutions contain salts of 1,4-naphthoquinone-2- ulfonic acid dissolved in an alkaline aqueous media within a pH range of 8 to 9 (Hasebe, 1970). The original Takahax process was based on sodium carbonate however, either sodium carbonate or ammonia are now used as the solution alkaline component. The quinone compound used in the Takahax process has a redox potential which is more than double that of anthraquinone di-sulfonic acid, also known as ADA, the quinone compound used in the Stretford proces.s. The greater redox potential of this naphthoquinone compound promotes a rapid conversion of H2S to sulfur without the addition of vanadium. 

A major drawback of the Takahax process is the slow rate of reoxidation of the reduced hydro-naphthoquinone sodium salt. This increases the regmerator residence time requirements and the capital cost. It is reported that the process is capable of producing treated gas containing less than 10 ppm of hydrogen sulfide even when the raw gas contains substantial quantities of carbon dioxide. In addition, 85 to 95% of the HCN in the feed is removed (GEESL 1981). 

Table 9-10 Typical Operating Conditlona of Takahax Process ...

The flow scheme of the Takahax process is quite similar to that of the Perox process, and, as in the Perox process, the oxidation of hydrosulfide to elemental sulfur in the absorber occurs almost instantaneously. Therefme, there is no need for a delay tank downstream of the absorber to complete the reaction. The process requires no steam and operates at ambient pressure. 

In the Takahax process the precipitated sulfur is very fine and not amenable to flotation. Therefore, when elemental sulfur recovery is desired, the sulfur recovery technique is based on continuous recirculation of a sulfur slurry of relatively high solids content and removal of sulfur from a slip stream in a filter press. 

Improvements made to the process by Nippon Steel during the early 1970s were described by Kozumi et al. (1977). One important new feature was the possible use of ammonia as the alkaline component of the solution in addition to sodium carbonate. This led to the development of two parallel technologies the Ammonia-Takahax and the Sodium-Takahax proces.s-es. The application of the Ammonia-Takahax process is preferred when the feed gas contains sufficient ammonia, and ammonium sulfate is the desired byproduct. The Sodium-Takahax process is preferred when either elemental sulfur or sulfuric acid is the desired byproduct (GEESl, 1981). 

Other modifications to the original process were aimed at developing new waste liquor treatment methods to make the Takahax process a closed-loop system. 

The first two options are available with the Ammonia-Takahax process, and the last two with the Sodium-Takahax process. 

In the U.S., the Takahax process has been used in combination with a wet oxidation Hiro-hax unit (Type A), where the thiosulfate and thiocyanate ammonium salts dissolved in the bleed stream are oxidized to fertilizer grade ammonium sulfate at high temperature (480°-535 F), and pressure (1,000-1,280 psig). In Japan, both wet oxidation units (Type A), and sulfur production units (Type D), are frequently selected, the choice depending primarily on the feed gas composition. 

The principal reactions in the Takahax process (Barry and Hernandez, 1990) are... 

The Takahax process is licensed in the United States by General Electric Environmental Services (GEESI), of Lebanon, PA. The first major installation of the Takahax process in the U.S. was in 1979 at Kaiser Steel s Fontana, CA, plant (GEESI, 1981) followed in 1981 by a second Takahax unit at the by-products plant of Republic Steel s coke plant, located in Chicago, IL (Williams et al., 1983). Both of these installations are Type A Takahax units. 

The Hiperion process is a modified version of the Takahax process. Prior to 1994. the process was licensed in the U.S. by Ultrasystems Engineers Contractors of Irvine, CA. In the Hiperion process, the active catalyst is a combination of naphthoquinone with chelated iron, which is claimed to considerably reduce the reoxidation residence time requirement when compared to the Takahax process (Dalrymple and Trofe, 1989). Since the volume of liquid needed in the oxidizer, and consequently the vessel size, is proportional to the residence time requirement, the change in solution chemistry is intended to reduce capital costs and make the process more attractive economically. 

Kozumi, T Idzutsu, W., Swaim, C. D., Tsurok, H., and Tsuchiya, T., 1977, Coke Oven Gas Desulfurization by the Takahax Process, paper presented at McMaster Symposium on Treatment of Coke-Oven Gas, McMaster Univ., Hamilton, Ontario, Canada, May 26. 

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