Partial Oxidation Shell gasification

A. Partial oxidation (Shell Gasification or catalytic partial oxidation)... 

Ammonia production by partial oxidation of hydrocarbon feeds depends to some degree on the gasification step. The clean raw synthesis gas from a Shell partial oxidation system is first treated for sulfur removal, then passed through shift conversion. A Hquid nitrogen scmbbiag step follows. 

The noncatalytic partial oxidation of hydrocarbons by the Shell gasification process (SGP) takes place in a refractory-lined reactor that uses a specially designed burner. The oxidant is preheated and then mixed with steam... 

The FT process is well known and already applied on a large scale [9,10,11,12]. Currently, the two players that operate commercial Fischer-Tropsch plants are Shell and Sasol. In the Sasol and Shell plants gasification of coal and partial oxidation of natural gas, respectively, produce the syngas for the FT synthesis with well-defined compositions. Shell operates the SMDS (Shell Middle Distillate Synthesis) process in Bintulu, Malaysia, which produces heavy waxes with a cobalt catalyst in multi-tubular fixed bed reactors. Sasol in South Afirica uses iron catalysts and operates several types of reactors, of which the slurry bubble column reactor is the most versatile (i.e. applied in the Sasol Slurry Phase Distillate SSPD),... 

A gas with an H /CO ratio of about 2 can be produced very competitively by non-catalytic autothermal partial oxidation, for example the Shell Gasification Process (SGP) (see Table 1). Such gas is particularly suitable for the production of high-quality middle distillates which are (iso)paraffinic in nature. For the manufacture of these products little or no adjustment of the H2/CO ratio is required, consequently giving a high overall process efficiency. In the case of paraffinic middle distillate production there is a net formation of water, as illustrated by the following reactions ... 

The current producers of partial oxidation processes are BASF, Texaco, Shell, and Hydrocarbon Research. A process block diagram showing the three process steps can be seen in Figure 2.18 [30]. The first step is the gasification process with the addition of oxygen and water. A detailed schematic of the Shell Gasification plant (SGP) is shown in Figure 2.19 [28]. The most important features of the process are the reactor, waste-heat-boiler, carbon catcher,... 

Partial oxidation is another important method to convert the petroleum feedstocks to methane rich synthetic gas [20], There are three well-developed commercial processes available in the market the Shell Gasification Process (SGP), the Texaco Gasification Process (TGP), and the Ube Process. In the following text a description of the SGP is presented and this process is compared with the TGP. A description of the Ube process is not included. 

The non-catalytic partial oxidation [486] (POX, Texaco, Shell) needs high temperature to ensure complete conversion of methane and to reduce soot formation. Some soot is normally formed and is removed in a separate soot scrubber system downstream of the partial oxidation reactor. The thermal processes typically result in a product gas with H2/C0=1.7—1.8. Gasification of heavy oil fractions, petcoke, coal and biomass may play an increasing role as these fiaetions are becoming more available and natural gas (NG) less available. 

Two processes are commercially established for heavy oil gasification, the Shell and the Texaco process (Figures 6.2.27 and 6.2.28) but the main steps of both processes are practically identical [see Supp (1978, 1997) for details). Besides partial oxidation of natural gas and residue oil, this process has been developed further for coal slurries (Table 6.2.6). Oxygen, pre-heated heavy oil, and steam are fed to the refractory-lined reactor where the oil is sprayed into the reactor. The reaction starts in a water-cooled burner, which also houses the atomizing gun and the oxygen and steam inlets. 

Development and Current Status. Development of the Shell gasification process for partial oxidation of oil and gas began in the early 1950s. More than 50 commercial Shell partial-oxidation plants have been built worldwide to convert a variety of hydrocarbon liquids and gases to carbon monoxide and hydrogen (1). This gas is most coromonly used as synthesis gas to produce high-value chemicals, such as ammonia and methanol. 

There are about a dozen gasification processes under development in this country and in Europe. A number of them have reached the stage of large pilot plants. The one that is probably closest to commercialization is the Texaco partial oxidation process. Texaco and Shell have both licensed partial oxidation processes for use with a variety of petroleum feeds since the late 19A0 s, and over 250 gasifiers have been installed, largely for making... 

Operation at very low temperatures with very sharp separations results in relatively complex flow schemes. This, combined with the need for low level refrigeration, leads to high plant costs. As a result, most applications of the Rectisol process represent relatively difficult gas treating conditions where other gas treating processes are not suitable for one reason or another. Typical applications are the purification of gas streams in the heavy oil partial oxidation processes of Shell and Texaco and the Lurgi coal gasification process, as used at the Sasol plants in South Africa. 

The Shell process uses partial oxygen gasification. Because insufficient oxygen exists for complete combustion (20-30% of the oxygen required for complete combustion is used), only a fraction of carbon in the coal is oxidized completely to C02. The heat released from this combustion provides most of the energy needed for endothermic coal gasification reactions and raises the gasifier temperature. Some steam is usually added to prevent excessive... 

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