Black liquor gasification is considered as an interesting alternative to the recovery boiler-based process of green liquor production. Although the handling of the smelt in the two separate processes is similar, the final concentration and temperature of the green liquor from gasification might both be higher. This, together with the S/Na split acquired by the gasification unit, may increase the risk of scaling of slightly soluble salts during green liquor handling. This work uses a previously developed solubility model for sodium carbonate, calcium carbonate and pirssonite, CaCO3Na2CO3 ·2H2O in order to evaluate the scaling risk in green liquor obtained from the gasification process. The model, originally based on both gasification green liquor and regular green liquor data, was verified against new samples of green liquor from an experimental gasification unit in Sweden. During the conducted sampling campaign, the following process parameters were varied in order to establish their influence on the final liquor composition: temperature and load of the gasifier, mixing rate in the smelt dissolver, and composition of the dilution water. It has been found that varying the process parameters within the normal operational limits has a relatively small influence, on the composition of the green liquor. The risk for pirssonite precipitation in gasification green liquor was estimated as relatively low, which is consistent with earlier findings. The calculated values of the apparent solubility product were also consistent with previous results.
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