Cold gas cleaning

Overall, the implication is that a system incorporating such a membrane and cold gas cleaning will require the following steps ... 

The Selexol method of acid gas removal may be used for combined removal of H2S and CO2 [3, 9], in which case it is desirable to employ sulfur-tolerant shift reactors before the Selexol system. On the other hand, if H2S alone is removed with a cold gas cleaning system, it is preferred to do so before shift reactor to avoid loss of CO2. 

Another example of a commercial-scale hybrid cold gas cleaning application is provided by the Harbopre up-draft gasification plant in Denmark [33]. Here, the gas is first processed in a water scrubber, with further water/tar aerosol and dust removal being carried out in a wet ESP (Figure 11.7). This combined operation results in the contents of both tar and dust in the cleaned gas being brought to below 25 mg/Nm, at 40 C. 

The use of hot gas clean-up methods to remove the sulfur and particulates from the gasified fuel increases turbine performance by a few percentage points over the cold clean-up systems. Hot gas clean-up permits use of the sensible heat and enables retention of the carbon dioxide and water vapor in the... 

Using essentially the same sub-dewpoint Claus reaction principle the Cold Bed Absorption (CBA) process of Amoco (47) achieves the same level of tail gas desulfurization. The low temperature high efficiency swing converters can be in line rather than as a tail gas clean up add on unit. 

Beside the problems of gas cleaning and waste water treatment the upscaling of fixed-bed gasifiers is limited to app. 1 MWe. But even in this relatively small power range electrical efficiencies between 18 and 28%, depending on the efficiency of the IC engine and the cold gas efficiency of the gasifier, are possible. The ratio electrical power to heat output (a) reaches 0,45 up to 0,65. 

For sulfur treatment, various cold gas systems have been developed to remove the bulk of sulfurous contaminants. The technologies and the levels of gas cleaning that they can achieve were summarized by Kerens et al. [9] ... 

In this section, techniques concerning melting practices and furnace operation will be discussed. These techniques may apply either to cold or hot blast operation, or to both. Flue-gas related techniques, such as post combustion and flue-gas cleaning, are discussed in Section 4.5.2. That section also discusses the conversion of cold blast to hot blast cupola furnaces. 

The effect and use of the oxygas burner depends on the cupola concerned. In cold blast cupola furnaces, the technique is used to ensure easy restarts or to reduce the proportion of coke. In hot blast operation, the technique is used to increase the furnace capacity without modifying the melting bed. The replacement of part of the coke with CH4 results in a reduction in flue-gas voliune. This is used as a means of increasing the furnace capacity, without over-saturating the installed flue-gas cleaning system. 

Additional operational data for cold and hot blast cupolas, with various flue-gas cleaning equipment types, are given and discussed in Section 4.5.2. Those data are taken from operating plants. 

---