Deashing of Sulfite-Alcohol Stillage Concentrates
Abstract Generated abstract
This study examines the deashing of solid sulfite-alcohol stillage concentrates using weak ammonia water and carbon dioxide, selected as potentially economical reagents when sourced from coke-plant ammonia liquor and flue gases. Experiments were conducted at room temperature by dissolving a KBT-grade concentrate sample in ammonia water of varying concentration and bubbling carbon dioxide through the solution, with reagent consumption varied relative to the theoretical requirement. The results show that high deashing levels, about 95 percent or more, can be obtained when ammonia and carbon dioxide are supplied in moderate excess, reducing the ash content of the treated solid concentrate from 13.32 percent to below 1 percent. The paper also estimates practical reagent consumption and notes that residual flue-gas heat could be used for partial evaporation if the resulting solution is too dilute.
Full Text
DEASHING OF CONCENTRATES OF SULFITE-ALCOHOL STILLAGE
Communication 2
V. M. Vityugin, V. A. Prokhorovich, L. G. Vedeneva
(Presented by the scientific seminar of the Department of OKhT)
As was already indicated in the first communication [1], the most promising deashing reagents for sulfite-alcohol stillage are ammonia and carbon dioxide. It is assumed that weak ammonia water will serve as the source of ammonia, while waste flue gases will serve as the source of carbon dioxide. At the same time, the ammonia water will serve as a solvent for solid SSB concentrates, and the flue gases, after bubbling through an SSB solution, will be purified and rendered harmless. This also determines the effectiveness of using such deashing reagents.
Below are the results of an experimental study evaluating the deashing ability of ammonia water and carbon dioxide.
As the object of the study, an averaged sample of sulfite-alcohol stillage concentrates of grade KBT (GOST 8518-57) from the Solikamsk Pulp and Paper Combine was used. The analytical data for the SSB sample are given below.
Ash content on a dry-mass basis, %, 13.32.
Chemical analysis of the ash, %
| Component | Content |
|---|---|
| SiO₂ | 1.30% |
| Fe₂O₃ | 0.24% |
| Al₂O₃ | 0.86% |
| CaO | 55.02% |
| MgO | 5.00% |
| SO₃ | 32.30% |
To dissolve the solid SSB concentrates, ammonia water with a concentration from 10 to 100 g/l was used. The carbon dioxide for the experiments was obtained in a Kipp apparatus. The consumption of carbon dioxide for deashing varied from 2 to 10 l per 100 g of solid SSB. Deashing was carried out at room temperature.
Experiments on deashing SSB concentrates in a solution of weak ammonia water were carried out by bubbling carbon dioxide through the solution layer for 30 minutes. Depending on the amount of carbon dioxide supplied and on the ammonia content in the solution, the breakthrough of carbon dioxide ranged from 30 to 90%.
The results of the experiments are presented in Table 1.
As is evident from Table 1, the best deashing results are obtained with an excess of ammonia and carbon dioxide of about 40–50% over the theoretically required amount. However, with an increase in the contact time of carbon dioxide with the ammonia solution, the amount of ammonium carbonate formed in the solution will increase and, consequently, the excess of reagents can be reduced.
Under practical conditions, the optimum consumption of deashing reagents can be adopted according to the data of experiment 10. When using cheap weak ammonia water from a by-product coke plant with an ammonia concentration of about 20 g/l, its specific consumption will be 6 m³ per 1 t of solid concentrate of sulfite-alcohol stillage. The consumption of flue gases in this case (CO₂ content—14–15%) will be 510 m³ per 1 t of solid SAS concentrate. If the SAS solution obtained is too dilute for practical use, partial evaporation can be carried out using the residual heat of the flue gases.
Table 1
Effect of ammonia and carbon dioxide consumption on the degree of deashing of sulfite-alcohol stillage
| No. | Specific gravity of SAS solution, g/cm³ | Ammonia consumption, g/100 g SAS | Carbon dioxide gas consumption, g/100 g SAS | Ash content of solid SAS after treatment, % | Degree of deashing, % |
|---|---|---|---|---|---|
| 1 | 1.20 | 2.5 | 17.0 | 12.00 | 9.9 |
| 2 | 1.20 | 4.0 | 17.0 | 10.90 | 18.0 |
| 3 | 1.19 | 9.3 | 17.0 | 3.58 | 73.1 |
| 4 | 1.18 | 18.6 | 17.0 | 0.79 | 94.0 |
| 5 | 1.17 | 27.9 | 17.0 | 0.70 | 94.8 |
| 6 | 1.19 | 12.3 | 5.0 | 5.20 | 61.0 |
| 7 | 1.19 | 12.3 | 10.0 | 3.82 | 71.3 |
| 8 | 1.19 | 12.3 | 12.5 | 2.18 | 83.5 |
| 9 | 1.19 | 12.3 | 14.0 | 1.50 | 88.7 |
| 10 | 1.19 | 12.3 | 15.0 | 0.66 | 95.0 |
| 11 | 1.19 | 12.3 | 17.5 | 0.55 | 97.5 |
| 12 | 1.14 | 18.6 | 20.5 | 0.67 | 94.9 |
REFERENCES
- V. M. Vityugin and E. S. Plotnikova. Deashing of sulfite-alcohol stillage. Izvestiya TPI, vol. 112, 1962.