Tail-gas treatment

Indeed, more pollutants may be emitted in the production of energy to replace the energy used for tail-gas treatment, than are recovered by the more efficient tail-gas treating processes. 

Reductive Tail Gas Treatments. It was largely as a result of the effort to achieve better than 99% recovery that the reductive tail gas desulfurization processes (46) were developed in the 1970 s. The two main methods are the Beavon Sulfur Removal (BSR) (47) and the Shell Claus Off-Gas Treatment (SCOT) (48) processes. Both of these processes are now widely used as tail gas desulfurization units on sulfur recovery plants and can readily achieve point source emission levels below 250 ppm and below 100 ppm if necessary to meet regulatory standards. 

Environmental regulations may force the "Claus" sulfur recovery to exceed 99%, requiring tail gas treatment. High CO2 in the original Claus feed, hence in the Claus tail gas, works strongly against the tail gas processes which use amine solution to extract H2S, and subsequently require incineration of residual H2S in a large volume of CO2. 

The H2S concentration in the tail gas of a conventional Claus plant is still some 5%. This H2S is normally incinerated to S02 and released to the atmosphere. Due to stricter environmental regulations a large number of new technologies based on Claus tail gas treatment have been developed to minimise the S02 exhaust from sulphur recovery units. The Superclaus process and the Shell Claus Off-Gas Treating (SCOT) process are treated below. For descriptions of other tail-gas processes, the reader is referred to [2],... 

Claus plant (including tail gas treatment) are of the order of 32/tonne exclusive of steam credit. Subtracting these costs from the totals in Table I, the overall net revenue from the Claus system would be 21.75/tonne of sulphur produced whereas that from the decomposition process would be 50.50 /tonne - a 230% difference. Even in the unlikely event that the total capital and operating costs for the decomposition process exceed those of the Claus system by 100%, the two processes are still approximately competitive. 

There are three principal approaches to tail gas treatment ... 

Typical technology SNEA/DEA Benhcld K,CO, Lurgi/Rectisol Claus and tail gas treatment 1... 

The Electrochemical Membrane Separator (EMS) technology being developed is compared to a wet removal process with subsequent Claus Plant processing to elemental sulfur and SCOT Tail Gas treatment of flue gases. This wet process utilities aqueous Methyldiethanolamine (MDEA) as an absorbent in a scrubbing operation to bring the HjS level from 1.7% to 4 ppm. The flow rate to these processes is 50MM SCFD and the process pressure is 715 psi. The... 

Referred single train with tail gas treatment (TGT) and overall... 

Main process parameters used for the techno-economical comparison are summarized in Table 8.1, where the novel process is compared with a conventional Claus unit -I- tail gas treatment (TGT) and steam methane reforming (SMR) for hydrogen production. 

Tail-Gas Treatment - Except for atmospheric units, exit gas from the absorber is normally... 

Other methods such as absorption by silica gel or molecular sieves or scrubbing with alkalies or urea solutions are also used by some companies but to a smaller extent. Detailed descriptions of tail-gas treatment processes are given in Chapter 19 [11,12]. 

Atmospheric Emissicms [13] - The main emissions to the atmosphere are oxides of nitrogen (NOx) and nitrous oxide (N2O). The concentration of NOx in emissions varies between 75 and 2,000 ppmv. The concentration of NOx depends on final acid concentration, absorption tower pressure and design, temperatures of the cooling tower water, quantity and quality of process water, d degree of tail-gas treatment, if any. 

Claus processes [1, 2] are used for large-scale (>5 t sulfur day ) industrial treatment of H2S-containing gases, with extension processes and tail gas treatment for conversions > 97 %, the limit otherwise imposed by equilibria in the... 

For all tail-gas treatment processes, the last traces of umeeovered sulfur go to an incinerator, where they are converted into SO2 and dispersed into the atmosphere. 

Blanco, J., Avila, R, Marzo, L., Suarez, S., and Knapp, C. Low temperature monolithic SCR catalysts for tail gas treatment in nitric acid plants. Stud. Surf. Sci. Catal 2000,130, 1391-1396. 

Industrial acid plant tail gas treatment methods... 

Consideration should be given to the following parameters when selecting an appropriate tail gas treatment technology. 

Cansolv , 2009. Cansolv SO2 scruhhing system for sulfuric acid plants, case study refinery acid plant tail gas treatment. Retrieved from http //www.cansolv.com/rtecontent/docu ment/CaseStudy.AcidPlantTailGas.pdf (accessed 05.10.12). 

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