Two UASB reactors R-I and R-II, each of 10liters capacity, made up of acryl material were operated parallel and continuously for a period of 220 days, using actual effluent of the NSSC pulp and paper mill, at mesophilic temperature and neutral pH. The main objective was to investigate the treatability performance of the reactors at varying OLR and HRT in terms of TOC and lignin removal. The reactor R-I was used by conventional procedure, whereas, for the reactor R-II methanol and activated carbon was added to supplement its efficiency. Corresponding to an optimum OLR of 4.5kg/m3-day and HRT of 18hrs, the reactor R-II gives 69% TOC and 60% lignin removal. But, in the reactor R-I at same operating conditions, only 56% TOC and 51% lignin removal was noticed. However, the biogas yield in the reactor R-I was noticed relatively more than in the R-II. The biogas yield observed was 0.28m3/kg-CODrem and 0.18m3/kg-CODrem in the reactor R-I and R-II, respectively, with 56-58% methane content in both the reactors. The average VFAs concentration observed in the reactor R-I and R-II is 360mg/L and 230mg/L, respectively. The results of this study suggest that the use of methanol and activated carbon to enhance the treatability efficiency of the UASB reactor is a viable option for the treatment of NSSC pulping effluent.

Rapeseed straw was collected from a cultivation farm in the vicinity of Babul, Mazandaran. Average fiber length, width, lumen diameter and cell wall thickness were measured as 860, 27.95, 18.86, and 4.42 mm respectively. Chemical components of rapeseed straw including cellulose, lignin, ash and extractives were measured as 44%, 19.21%, 6%, and 13% respectively. Optimum pulping conditions to reach the pulp yield of 66%, were selected applying chemical charge of 20% (based on Na2O), cooking temperature of 170oC, and cooking time of 30 min. The pulps were refined to 350 and 400 ml CSF using PFI mill. Statistical analysis showed that mechanical properties of hand sheets with the basis weight of 127 gm-2 made from rapeseed straw NSSC pulp at the freeness of 350 and 400 ml CSF exhibited better properties compared to mixed hardwood NSSC pulp to produce fluting paper.

By carrying various cooking from sunflower stack chips using NSSC pulping process, optimum cooking at pulp yield of 43.8 % and kappa number of 82.6 was selected under cooking condition of 20 % chemical charge based on sodium oxide, cooking time of 180 min, and maximum temperature of 170 degree Celsius. The pulps were refined to obtain freeness levels of 328 ad 372 ml, CSF, by PFI mill revolutions of 150 and 500, respectively. Standard hand sheets with grammage of 127 g/m2 were made from both sunflower NSSC pulps, at three levels of 10, 20 and 30 % in admixture with hardwood NSSC pulp from Mazandaran Wood and Paper Industries (MWPI), and their physical and strength properties were measured. Statistical analysis showed that, up to 30 % of sunflower NSSC pulp with freeness of 328 ml, CSF can be blended with hardwood NSSC pulp from MWPI, to make fluting paper. It has been also shown that, up to 30 % of hardwood NSSC pulp from MWPI can be substituted by sunflower NSSC pulp at freeness level of 372 ml, CSF, if 5 % unbleached softwood kraft pulp can be used in the furnish.

This research was performed to improve the properties of the pulp made of Aspen Deltoides, using antraquinone (AQ) catalizer. Neutral sulfite semi chemical (NSSC) method in three efficiency levels of 55, 60, and 65% was applied. Cooking situations was selected as: Specific Temperature (175o C), Time (Variable), Specific Percentage of Chemicals 14% and Anthraquinone 0.1%. In all stages of cooking, weight ratio of sodium sulfide to sodium bicarbonate was set as 4.5/1. The ratio of cooking liquid to chips was 5.1. The results indicated that AQ causes an increase in efficiency and a significant decrease in Kappa. Researches also indicated that by the use of AQ, strength indexes of the paper such as strength of burst, tearing, tensile, Ring Crush Test and Corrugating Medium Test increases. Optical experiments on hand sheets following addition of AQ, indicated increase in brightness and decrease in opacity.

Cellulose fibers undergo a series of irreversible changes i.e hornification when exposed to cycles of wetting and drying. In this study, the effect of recycling on physical and chemical properties of chemimechanical pulp (CMP) and neutral sulfite semi-chemical (NSSC) pulp was evaluated. The pulps were recycled three times. Hornification was measured by Water retention value. The results indicated that water retention value and carboxyl groups were decreased due to recycling, hornification also increased during cycles of wetting and drying. Changes in crystalline structure of the pulp during first cycle of recycling were investigated by ATR- FTIR. The crystallinity index increased to some extent, when compared to virgin pulp. Recycling influence on the fiber length was not significant. Hornification introduced as a main cause of poor properties of recycled paper. Also, reduction of carboxyl groups could be one of the causes for lowering water retention value and decrease in strengths.

This study was conducted to investigate the properties of NSSC pulp from seed original stem and second-growth of Eucalyptus camaldulensis. Cooking conditions were as follow: time 30, 60 and 90 minutes, Temperature 165oC and L/w: 6/1. Na2SO3 and NaHCO3: 15% and 7% based on OD weight of wood, respectively. In this study fiber dimension and chemical compositions of woods were determined. The pulps were refined to reach the target freeness value (400ml, CSF). Then, hand sheets were made and tested. The average pulp yield for seed original stem wood was higher than the second-growth wood. The results of the strength properties indicate that all properties of the pulp produced from seed original stem in the same condition are higher than those of the pulp of the second-growth wood, but there was no significant difference between them. However, regarding to the results in terms of fast-growth, higher pulp yield and lower refining energy required to reach the proper freeness value, make the second-growth wood as suitable as the seed original stem wood in pulp and paper industry.

The effect of recycling on physical properties of lignin rich chemimechanical pulp (CMP) and  neutral sulfite semi-chemical (NSSC) pulp was evaluated. The pulps were exposed to recyclingtreatment for three times without any further refining and the fines were conserved. The results indicated that some physical properties like tensile strength, tensile energy adsorption (TEA), burst strength, apparent density and compression strength were decreased by recycling due to hornification followed by loss in fiber flexibility and swelling which give rise to interfiber bonding loss. However the opacity and light scattering coefficient presented gain through recycling. Besides, the bending stiffness, air permeability and roughness increased due to recycling. The observations generally indicated that the CMP and NSSC pulps behavior under recycling is much similar to that of chemical pulp rather than mechanical pulps.

This research was performed to determine optimum freeness of pulp produced from bogasse by NSSC process. Depithed bagasse (Wet method) was prepared from pars pulp and paper mill, Khozestan province. The cooks was done using the cooking liquor of Mazandaran pulp and paper mill having 20% chemicals on the basis of dry bagasse weight. Then, the pulps were refined up to 350±25, 400±25, 450±25 CSF by using PFI Mill refiner. Then, 127 gr/m2 hand sheet papers were made from different samples of pulps and their strength properties were measured. TAPPI standard was used to measure the resistant properties of hand sheet papers. The results showed that papers produced from pulps with 350±25 (CSF) freeness, have the most mechanical properties. Concerning other factors such as possessing minimum standard values and refining energy, pulps with 400±25 (CSF) is recommended. In addition, when the refining increased, the resistance indexes of paper such as Ring Crush Test (RCT), Stiffness, Tensile Strength, Burst Strength, and Breaking Length was increased. The only exception was tear strength that decreased, probably because of cutting and shortening of fibers due to increased refining.

In this research, neutral sulfite semi-chemical (NSSC) pulping of mazandaran province canola stalks was studied. At first the anatomic and chemical properties of canola stalke fiber were measured. The pulping conditions were as follows: Pulping temperature on one level (170 oC), pulping time of 3 levels (20, 30 and 40 minutes) and sodium sulfite charge on 3 levels (10, 15, and 20%). In all cooks, the proportion of Na2So3 to Na2Co3 was 2 to 1 The output after cooking varied from 61 to 82 %. Regarding the optimum freeness for the NSSC process, pulp was refined to obtain 400±25 CSF. From each pulps sample, 127 g/m2 handsheets were prepared. Then, using TAPPI standard methods, strength properties of handsheets were studied. The statistical analysis of strength indexes showed that the pulping condition with 20% sodium sulfite and cooking for 30 minutes the optimum condition of (NSSC) pulping for corrugated medium production. The paper properties including corrugated medium test, ring crush test, tensile strength index, tear strength index and burst strength index were 232 KN/m, 1.96 KN/m, 35.56 N.m/g, 6.19 mN.m2/g and 2.29 Kpa.m2/g respectively.