| 1. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
New findings in sulfite pulping of softwood dissolving pulps
- 2015
-
Ingår i: 5th Avancell Conference Chalmers University of Technology Gothenburg Sweden, October 6-7 2015.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Karlstads University has for a long time done research on sulfite pulping with the purpose to increase the knowledge on sulfite pulping, to verify old fundamental results an to keep the knowledge on sulfite pulping alive. The basic objective during the last years has been to increase the value of the products produced in such a process and the vision is to make sulfite pulps the preferred pulp grade for dissolving pulps. These studies have so far included spruce and pine. Domsjö Fabriker and MoRe Research in Örnsköldsvik, Sweden have been industry partners in this project.
|
|
| 2. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
Some process aspects on acid sulphite pulping of softwood
- 2016
-
Ingår i: Journal of Science & Technology for Forest Products and Processes. - Montreal : Pulp and Paper Technical Association of Canada. - 1927-6311 .- 1927-632X. ; 6:2, s. 48-54
-
Tidskriftsartikel (refereegranskat)
|
|
| 3. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
Some process aspects on single-stage bisulfite pulping of pine
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 31:3, s. 379-385
-
Tidskriftsartikel (refereegranskat)abstract
- Sulfite pulping of pine is well-known to be a risky process because problematic lignin conden-sation reactions can occur resulting in poor pulp quality. However, sulfite pulping of pine is interesting of economic reasons as pine wood is cheaper than spruce. Therefore it has become interesting to investigate sulfite pulping again to determine if old data are still valid. Thus sodium bisulfite pulping of pine was carried out to investigate the influence of time, temperature and cooking acid quality. A small comparison of spruce pulping was also included. By using different cooking temperatures the activation energies for delignification and for degradation of cellulose and hemicelluloses could be determined. The results showed no lignin condensation reactions, thus it was not problematic to carry out these pine cooking experiments. It was found that glucomannan had higher activation energy than xylan and the activation energies of these hemicelluloses were lower than the corresponding value for the lignin degradation. It was found that the activation energy for bisulfite pulping of pine was slightly lower than the activation energy for bisulfite pulping of spruce.
|
|
| 4. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
The influence of different types of bisulfite cooking liquors on pine wood components
- 2016
-
Ingår i: BioResources. - Raleigh : North Carolina State University. - 1930-2126. ; 11:3, s. 5961-5973
-
Tidskriftsartikel (refereegranskat)abstract
- In this laboratory study, the initial phase of a single-stage sodium bisulfite cook was observed and analyzed. The experiments were carried out using either a lab- or a mill-prepared cooking acid, and the cooking temperature used in these experiments was 154 °C. Investigated parameters were the chemical consumption, the pH profile, and the pulp yield with respect to cellulose, lignin, glucomannan, xylan, and finally extractives. Cooking was extended down to approximately 60% pulp yield and the pulp composition during the cook, with respect to carbohydrates and lignin, was summarized in a kinetic model. The mill-prepared cooking acid had a higher COD (Chemical Oxygen Demand) and TOC (Total Organic Carbon) content than the lab-prepared cooking acid and this influenced the pH and the formation of thiosulfate during the cook. It was found that the presence of dissolved carbohydrates and lignin in the bisulfite cooking liquor affected the extractives removal and the thiosulfate formation.
|
|
| 5. |
|
|
| 6. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
The Initial Phase of Sodium Bisulfite Pulping of Pine, Part II
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - Härnösand : Mittuniversitetet. - 0283-2631 .- 2000-0669. ; 31:3, s. 379-385
-
Tidskriftsartikel (refereegranskat)abstract
- Single stage sodium bisulfite cooking of pine was carried out to investigate the influence of time and temperature in the initial phase of the cook. The cooking experiments were carried out using either a lab or a mill prepared cooking acid and the initial stage of the cook was extended up to 5 h cooking time. The impact of temperature on wood components and side reactions was analyzed between 142°C and 165°C. Arrhenius equation was used to determine the influence of temperature on wood components during the initial phase of bisulfite cooking and the activation energy was calculated for delignification rate, cellulose degradation and hemicellulose dissolution with regard to glucomannan and xylan. The extent of extractives removal at different temperature and time was also analyzed.
|
|
| 7. |
|
|
| 8. |
- Deshpande, Raghu, 1979-
(författare)
-
The initial phase of sodium sulfite pulping of softwood : A comparison of different pulping options
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Single stage and two-stage sodium sulfite cooking were carried out on either spruce, pine or pure pine heartwood chips to investigate the influence of several process parameters on the initial phase of such a cook down to about 60 % pulp yield. The cooking experiments were carried out in the laboratory with either a lab-prepared or a mill-prepared cooking acid and the temperature and time were varied. The influences of dissolved organic and inorganic components in the cooking liquor on the final pulp composition and on the extent of side reactions were investigated. Kinetic equations were developed and the activation energies for delignification and carbohydrate dissolution were calculated using the Arrhenius equation. A better understanding of the delignification mechanisms during bisulfite and acid sulfite cooking was obtained by analyzing the lignin carbohydrate complexes (LCC) present in the pulp when different cooking conditions were used. It was found that using a mill-prepared cooking acid beneficial effect with respect to side reactions, extractives removal and higher stability in pH during the cook were observed compared to a lab-prepared cooking acid. However, no significant difference in degrees of delignification or carbohydrate degradation was seen. The cellulose yield was not affected in the initial phase of the cook however; temperature had an influence on the rates of both delignification and hemicellulose removal. It was also found that the corresponding activation energies increased in the order: xylan, glucomannan, lignin and cellulose. The cooking temperature could thus be used to control the cook to a given carbohydrate composition in the final pulp. Lignin condensation reactions were observed during acid sulfite cooking, especially at higher temperatures. The LCC studies indicated the existence of covalent bonds between lignin and hemicellulose components with respect to xylan and glucomannan. LCC in native wood showed the presence of phenyl glycosides, ϒ-esters and α-ethers; whereas the α-ethers were affected during sulfite pulping. The existence of covalent bonds between lignin and wood polysaccharides might be the rate-limiting factor in sulfite pulping.
|
|
| 9. |
- Deshpande, Raghu, 1979-
(författare)
-
The initial phase of the sodium bisulfite pulping of softwood dissolving pulp
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The sulfite pulping process is today practised in only a small number of pulp mills around the globe and the number of sulfite mills that use sodium as the base (cation) is less than five. However, due to the increasing interest in the wood based biorefinery concept, the benefits of sulfite pulping and especially the sodium based variety, has recently gained a lot of interest. It was therefore considered to be of high importance to further study the sodium based sulfite process to investigate if its benefits could be better utilized in the future in the production of dissolving pulps. Of specific interest was to investigate how the pulping conditions in the initial part of the cook (≥ 60 % pulp yield) should be performed in the best way.Thus, this thesis is focused on the initial phase of single stage sodium bisulfite cooking of either 100 % spruce or 100 % pine wood chips. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and cooking time were varied. Activation energies for different wood components were investigated as well as side reactions concerning the formation of thiosulfate and sulfate.
|
|
| 10. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
The magic of sulphite pulping : The critical first stage of a dissolving pulp cook
- 2013
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A PhD project was started in 2012 with the purpose to in depth examine the first and second part of a sodium sulfite dissolving pulp cook including a following extraction stage. The experimental study started with the first part of the cook when using spruce or pine as the wood raw material and when using lab or mill cooking liquors. A large number of cooking experiments have been performed and a lot of data has been obtained and the risk for obtaining a black cook has been especially observed. In the latter case the thiosulphate content is very critical as it can both lead to a black cook and to decomposition reactions in the cooking liquor. How to avoid problematic cooking conditions will be especially highlighted in the project but ways to produce new pulp grades and new chemicals will be equally important
|
|
| 11. |
- Deshpande, Raghu, 1979-, et al.
(författare)
-
The reactivity of lignin carbohydrate complex (LCC) during manufacture of dissolving sulfite pulp from softwood
- 2018
-
Ingår i: Industrial crops and products (Print). - : Elsevier B.V.. - 0926-6690 .- 1872-633X. ; 115, s. 315-322
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of covalent bonds between lignin and polysaccharides was investigated in dissolving pulps made with one-stage and two-stage acidic sulfite pulping for 100% pine heartwood raw material. The covalent bonds between lignin and pulp polysaccharides occurred mainly to xylan and glucomannan and were of the phenyl glycosides and γ–esters types. The α-ethers that are common in wood were missing in the studied pulp samples. Based on these findings and known lignin reactions during sulfite pulping, a mechanism explaining the absence of the α-ethers is discussed. It is suggested that the lignin carbohydrate bonds may play a vital role in lignin recalcitrance.
|
|
