Carbonate channel

Model the carbonate precipitation in this carbonate channel by means of a Id transport with 40 cells of 10 m length each. Dispersivity is assumed with lm. Use the key words KINETICS and RATES and the BASIC program for calcite from the data set PHREEQC.dat describing the kinetics for both the calcite dissolution and the calcite precipitation. How much calcite precipitates each year within the channel s first 400 meter after the discharge How much C02 degasses at the same time ... 

Apply 1 m/s as flow velocity so that the total contact time in the channel is 500 seconds. The modeling should be done as Id transport model with 10 cells (dispersivity 0.1 m) and last over 750 seconds. Also take into account the contact with the atmosphere. Therefore, ran the model once with a C02 partial pressure of 0.03 Vol% and a second time with 1 Vol%, both times assuming an oxygen partial pressure of 21 Vol% 02. The latter case corresponds rather to a closed carbonate channel. 

The acid mine water is defined as SOLUTION 0 and the water in the carbonate channel as SOLUTION 1. Within the key word KINETICS 1-10 the calculation tolerance as well as the initial and the total mole mass of calcite can be defined. Obligatory are only the parameter 50 and 0.6. These are needed by the BASIC program, which must be implemented within the key word RATES. Here, we use the BASIC program listed at the end of the database PHREEQC.dat. If the database PHREEQC.dat is used (which is not free of troubles, since there are, e g., no data for uranium) or if the paragraph is copied into another database, it is not necessary to define a RATES block in the input file. PHREEQC uses automatically the RATES block from the database. Yet, if any other kinetic rates are to be used, the BASIC program must be copied into the input file under RATES. In any case, the KINETICS block is required. 

Fig. 73 Concentration changes in an acid mine water while flowing thorough a 500m long carbonate channel...

Alternative Names/Abbreviations Activated carbon, acetyiene carbon, decolourising carbon, actibon, ultra carbon, channel black, furnace black, thermal black, gas black, lamp black... 

In general, it is difficult to extract quantitative information directly from a CP experiment. To overcome one of the main obstacles in normal CP, the short T p of the protons, Johnson and Schmidt-Rohr proposed the multiCP sequence [113]. The sequence can be seen in Fig. 4B. It basically contains a series of CP blocks interleaved with longitudinal relaxation periods of C duration. Prior to a relaxation period, all magnetization on both the proton and the carbon channels is stored along the z-axis by applying x/2 pulses. 

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