OXIDATIVE GASIFICATION

Equipment. Partial-oxidation gasification section equipment in many plants consists essentially of (/) the gasification reactor (2) the waste-heat exchanger for heat recovery from the hot reactor gas or direct quench system (J) the economizer heat exchanger for further heat recovery (4) the carbon removal system for separating carbon from the reactor product gas and (5) the carbon recovery system for recycle of carbon. 

Gasification coupled with water-gas shift is the most widely practiced process route for biomass to hydrogen. Thermal, steam, and partial oxidation gasification technologies are under development. Feedstocks include both dedicated crops and agricultural and forest product residues of hardwood, softwood, and herbaceous species. 

Today, different processes (steam reforming, autothermal reforming, partial oxidation, gasification) are available and commercially mature for hydrogen production from natural gas or coal. These processes would have to be combined with technologies for C02 capture and storage (CCS), to keep the emissions profile low. A power plant that combines electricity and hydrogen production can be more efficient than retrofitted C02 separation systems for conventional power plants. 

The Texaco gasification process is a partial oxidation gasification process for generating synthetic gas, principally hydrogen and carbon monoxide. 

Process Steam Reforming Partial Oxidation Gasification Steam-Iron Electrolysis (Current) Electrolysis (New Technology)... 

JVoccss Steam reforming Steam reforming Partial oxidation Gasification ... 

Hence, according to the proportion of CO and CO2, the gaseous mixture required for conversion must have a hydrogen to carbon molar ratio between 2 and 3 . Sudi a gas can be obtained, as mentioned above, by partial oxidation, gasification, or steam reforming. 

Fig. 6 Effect of mixed catalyst on gasification of cellulose with partial oxidation. Gasification of liquidized product...

It is interesting to note that many of the factors that were important in controlling catalysis are also important in oxidation. The concentration and nature of surface complexes is as important in oxidative gasification as in catalysis, and the presence or absence of metal or metal-salt impurities has a profound effect on the kinetics of the reaction. The kinetics of the reaction may be influenced by mass and heat transfer in the carbons and depend, among many other factors, on the nature and structure of the carbons. ... 

Masaru Watanabe, Hiroshi Inomata, Mitsumasa Osada, Takafumi Sato, Adschiri, Kunio Arai. (2003), Catalytic effects of NaOH and ZrO2 for partial oxidative gasification of -hexadecane and lignin in supercritical water. Fuel. 82,545-552. 

Tocess Reforming Reforming Partial oxidation Gasification with air j in oxygen ... 

Can Recycling an Unwanted Product or an Inert Shift the Reaction Equilibrium to Produce Less of an Unwanted Product Another exanple of recycling an inert or unwanted product is to use that material to change the conversion and selectivity of an equilibrium reaction. For exanple, consider the production of synthesis gas (H2 and CO) via the partial oxidation (gasification) of coal ... 

Ammonia from coal gasification has been used for fertilizer production at Sasol since the beginning of operations in 1955. In 1964 a dedicated coal-based ammonia synthesis plant was brought on stream. This plant has now been deactivated, and is being replaced with a new faciUty with three times the production capacity. Nitric acid is produced by oxidation and is converted with additional ammonia into ammonium nitrate fertilizers. The products are marketed either as a Hquid or in a soHd form known as Limestone Ammonium Nitrate. Also, two types of explosives are produced from ammonium nitrate. The first is a mixture of fuel oil and porous ammonium nitrate granules. The second type is produced by emulsifying small droplets of ammonium nitrate solution in oil. 

Parameter Steam reforming (SR) Partial oxidation (POX) Texaco gasification (TG) Water electrolysis... 

Partial oxidation of heavy Hquid hydrocarbons requires somewhat simpler environmental controls. The principal source of particulates is carbon, or soot, formed by the high temperature of the oxidation step. The soot is scmbbed from the raw synthesis gas and either recycled back to the gasifier, or recovered as soHd peUetized fuel. Sulfur and condensate treatment is similar in principle to that required for coal gasification, although the amounts of potential poUutants generated are usually less. 

This process is one of the three commercially practiced processes for the production of acetic anhydride. The other two are the oxidation of acetaldehyde [75-07-0] and the carbonylation of methyl acetate [79-20-9] in the presence of a rhodium catalyst (coal gasification technology, Halcon process) (77). The latter process was put into operation by Tennessee Eastman in 1983. In the United States the total acetic anhydride production has been reported to be in the order of 1000 metric tons. 

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. 

Capital costs which foUow the same trend as energy consumption, can be about 1.5 to 2.0 times for partial oxidation and coal gasification, respectively, that for natural gas reforming (41). A naphtha reforming plant would cost about 15—20% more than one based on natural gas because of the requirement for hydrotreatiag faciUties and a larger front-end needed for carbon dioxide removal. 

---