Bio-refinery system of DME or CH4 production from black liquor gasification in pulp mills

There is great interest in developing black liquor gasification technology over recent years for efficient recovery of bio-based residues in chemical pulp mills. Two potential technologies of producing dimethyl ether (DME) and methane (CH₄) as alternative fuels from black liquor gasification integrated with the pulp mill have been studied and compared in this paper. System performance is evaluated based on: (i) comparison with the reference pulp mill, (ii) fuel to product efficiency (FTPE) and (iii) biofuel production potential (BPP). The comparison with the reference mill shows that black liquor to biofuel route will add a highly significant new revenue stream to the pulp industry. The results indicate a large potential of DME and CH₄ production globally in terms of black liquor availability. BPP and FTPE of CH₄ production is higher than DME due to more optimized integration with the pulping process and elimination of evaporation unit in the pulp mill.     

Exploration of the effect of process variables on the production of high-value fuel gas from glucose via supercritical water gasification

A new continuous supercritical water gasification reactor was designed to investigate glucose gasification in supercritical water at high temperatures and low residence times. A 2(3) full factorial experiment was performed to determine the effects of feed concentration, temperature, and residence time on glucose gasification. The temperature levels (750°C and 800°C) were higher than ever used, while the residence times (4 and 6.5s) were shorter than ever used in previous supercritical water gasification studies. The reactor proved capable of attaining higher gasification rates than previously shown with high efficiencies and yields. In addition, the glucose gasification reaction was modeled by estimating activation energy and reaction order of glucose gasification in supercritical water.     

Recovery of activated carbon catalyst,calcium, nitrogen and phosphate from effluent following supercritical water gasification of poultry manure

A new method for suspending a fine, activated carbon catalyst in a biomass feedstock used for a supercritical water gasification (SCWG) continuous reactor is proposed. In a previous study, the organic matter in poultry manure was shown to be completely converted into gases such as H₂, CO₂ and CH₄ using SCWG. In practice, however, since the feedstock is not only composed of organic matter, but also contains inorganic material, water and catalyst, products such as gas, solid and liquid are produced during SCWG. The aim of this work was to investigate SCWG by-product utilization. This paper describes fundamental studies on the recovery of materials from SCWG products to develop a novel and simple recycling process that utilizes the by-products. A major portion of the activated carbon, monetite and ammonium sulfate can be isolated from the SCWG effluent.     

Kraft black liquor for improving the productivity of Spirulina biomass

Summary Mass cultivation of Spirulina for commercial application suffers from poor productivity when measured against laboratory results or theoretical projections. Wider applications of algal products require that this gap be reduced. Addition of eucalyptus kraft black liquor at a maximum of 0.1% to Spirulina cultures enhanced biomass productivity by at least 40%. The factors enhancing Spirulina biomass productivity were insoluble at low pH, of low molecular mass and stable to high temperature. Single addition of kraft black liquor in outdoor continuous cultures afforded sustained enhancement in biomass productivity for at least eight weeks.     

Decomposition reaction of sesamin in supercritical water

The methylenedioxyphenyl moiety in the structure of sesamin and episesamin was changed into the catechol moieties, (1R,2S,5R,6S)-6-(3,4-dihydroxyphenyl)-2-(3,4-methylenedioxyphenyl)-3,7-dioxabicyclo[3,3,0]octane, (1R,2R,5R,6S)-2-(3,4-dihydroxyphenyl)-6-(3,4-methylenedioxyphenyl)-3,7-dioxabicyclo[3,3,0]octane, (1R,2R,5R,6S)-6-(3,4-dihydroxyphenyl)-2-(3,4-methylenedioxyphenyl)-3,7-dioxabicyclo[3,3,0]octane, (1R,2S,5R,6S)-2,6-bis(3,4-dihydroxyphenyl)-3,7-dioxabicyclo[3,3,0]octane, and (1R,2R,5R,6S)-2,6-bis(3,4-dihydroxyphenyl)-3,7-dioxabicyclo[3,3,0]octane, in supercritical water. These products had same structures as the sesamin metabolites which act as antioxidants in the liver. These features suggested the direct preparation of antioxidants from sesamin by a one-step reaction using supercritical water.     

Biodiesel production by supercritical process with crude bio-methanol prepared by wood gasification

In order to prepare a genuine biodiesel, it is essential to use methanol prepared from biomass but not natural gas for biodiesel production. Thus, we have proposed to use crude bio-methanol produced by wood gasification for biodiesel production. Since such a bio-methanol contains some impurities, an effect of its impurities was studied on the biodiesel production by supercritical method. In general, impurities in crude bio-methanol are reported to include methyl formate, ethanol, 1-butanol, diisopropyl ether, water, etc. Triglycerides and oleic acids were, thus, treated with these impurities under supercritical conditions. As a result, it was found that methyl formate, ethanol and 1-butanol could convert them to fatty acid alkyl esters (BDF), whereas no conversion was achieved with diisopropyl ether. Thus, crude bio-methanol can be used for BDF production as a substitute for methanol from fossil resources. However, due to more efficient reaction, crude bio-methanol can be more applicable to the two-step supercritical methanol process, consisting of hydrolysis of triglycerides and subsequent esterification of fatty acids, compared with the one-step supercritical methanol process, where transesterification of triglycerides is a major reaction.     

Bacterial decolorization of black liquor in axenic and mixed condition and characterization of metabolites

The pulping byproducts (black liquor) cause serious environmental problem due to its high pollution load. In order to search the degradability of black liquor, the potential bacterial strains Citrobacter freundii (FJ581026) and Citrobacter sp. (FJ581023) were applied in axenic and mixed condition. Results revealed that the mixed bacterial culture are more effective than axenic condition and can reduce 82% COD, 79% AOX, 79% color and 60% lignin after 144 h of incubation period. Additionally, the optimum activity of lignin degrading enzyme was noted at 96 h and characterized as manganese peroxidase (MnP) by SDS–PAGE analysis. Further, the HPLC analysis of control and bacterial degraded sample has shown the reduction as well as shifting of peaks compared to control indicating the degradation as well as transformation of compounds of black liquor. The comparative GC–MS analysis of control and degraded black liquor revealed that along with lignin fragment some chlorophenolic compounds 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol and pentachlorophenol were detected in black liquor degraded by axenic culture whereas these chlorophenolic compounds were completely absent in black liquor degraded by mixed bacterial culture. These chlorophenol inhibit the oxidative degradation which seems a major reason behind the low degradability of axenic degradation compared to mixed culture. The innovation of this aerobic treatment of alkaline black liquor opens additional possibilities for the better treatment of black liquor along with its metabolic product.     

Carbon and char residue yields from rapid pyrolysis of kraft black liquor

The yields of char residue, fixed carbon, and inorganic carbonate were measured for oxidized black liquor char residues produced in a laboratory laminar entrained-flow reactor (LEFR) at heating rates of 4000-13,000 degrees C/s. The char residue yields at the end of devolatilization thus obtained decreased nearly linearly with temperature, from 75% at 700 degrees C to 58% at 1100 degrees C. There were explainable differences in the char residue yields from the liquor used in this study and those used in other studies. Char residue yields seemed to depend mainly on the temperature to which the particles or droplets were exposed and were not very sensitive to heating rate. Fixed carbon yields behaved similarly to those of the char residue. The fixed carbon remaining at the end of devolatilization decreased from 67% at 700 degrees C to about 45% at 1100 degrees C. The carbonate content in black liquor changed very little before and after devolatilization.     

Influence of pressure on pyrolysis of black liquor: 1. Swelling

This is the first of two papers concerning the behavior of black liquor during pyrolysis under pressurized conditions. Two industrial kraft liquors were pyrolyzed in a laboratory-scale pressurized single particle reactor and a pressurized grid heater at temperatures ranging from 650 to 1100 degrees C and at pressures between 1 and 20 bar. The dimensions of the chars produced were measured and the specific swollen volume was calculated. Swelling decreased roughly logarithmically over the pressure range 1-20 r. An expression is developed to predict the specific swollen volume at elevated pressure when the volume at 1 bar is known. The bulk density of the char increased with pressure, indicating that liquors will be entrained less easily at higher pressures.     

Supercritical water gasification of biomass: Thermodynamic constraints

In the present work, the supercritical water gasification (SCWG) of biomass is analyzed with a view to outlining the possible thermodynamic constraints that must be taken into account to develop this new process. In particular, issues concerning the formation of solid carbon and the process heat duty are discussed. The analysis is conducted by means of a two-phase non-stoichiometric thermodynamic model, based on Gibbs free energy minimization. Results show that char formation at equilibrium only occurs at high biomass concentrations, with a strong dependence on biomass composition. As regards the process heat duty, SCWG is mostly endothermic when biomass concentration is low, although a very small amount of oxidizing agent is able to make the process exothermic, with only a small loss in the heating value of the syngas produced.     

不同纤维素原料超临界水解的研究

分别以稻草秸秆、经预处理的稻草秸秆、脱脂棉、微晶纤维素和定性滤纸为原材料,利用间歇式的超临界反应设备,在400℃的盐浴中进行木质纤维素的超临界水解,采用3,5-二硝基水杨酸(DNS)法对产物中的还原糖进行测定,研究反应时间对不同纤维素原料水解产糖的影响。结果表明:在超临界条件下,不同原料在较短的时间内还原糖含量均出现峰值,随着反应时间的延长还原糖产量呈现下降的趋势;稻秆、预处理后的稻秆、脱脂棉、微晶纤维素和定性滤纸的最大产糖量分别为7.42、9.05、12.55、18.01和14.24 g/L;与此对应的最佳反应时间分别为3.5、4、3、3、4 min;对应的最大还原糖产率分别为14.84%、18.10%、25.10%、36.02%、28.48%。     

Exploring the antioxidant potential of lignin isolated from black liquor of oil palm waste

This study was conducted to evaluate the potential antioxidant activity of lignin obtained from black liquor, a hazardous waste product generated during the extraction of palm oil. Antioxidant potential of the extracted lignin was evaluated by dissolving the extracted samples in 2 different solvent systems, namely, 2-methoxy ethanol and DMSO. Results revealed high percent inhibition of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in the lignin sample dissolved in 2-methoxy ethanol over DMSO (concentration range of 1–100 μg/ml). Lignin extracted in 2-methoxy ethanol exhibited higher inhibition percentage (at 50 μg/ml, 84.2%), whereas a concentration of 100 μg/ml was found to be effective in the case of the DMSO solvent (69.8%). Fourier transform infrared (FTIR) spectrometry revealed that the functional groups from the extracted lignin and commercial lignin were highly similar, indicating the purity of the lignin extracted from black liquor. These results provide a strong basis for further applications of lignin in the food industry and also illustrate an eco-friendly approach to utilize oil palm black liquor. To cite this article: R. Bhat et al., C. R. Biologies 332 (2009).     

Fermentation of kraft black liquor for the production of citric acid by Candida tropicalis

Summary The production of citric acid by batch fermentation with the yeast strain Candida tropicalis ATCC 20240 was chosen as a potential process for the valorization of kraft black liquor. The effect of nitrogen concentration was studied and direct bioconversion of acetate to citrate was achieved when no nitrogen was supplemented to the medium. The use of kraft black liquor's acetate as a potential substrate for citric acid production was investigated. The acid precipitated liquor was highly inhibitory when its concentration was above 25% of the fermentation broth content. The yields of citric acid at low concentrations of kraft black liquor (5% and 15%) were the same as those recorded in synthetic acetate medium. Other organic acids present in the liquor may affect the yields and rates of citric acid production over acetate. Substrate uptake rates and product formation rates were lower, however, in comparison to synthetic media. The utilization of immobilized biomass improved the process parameters on kraft black liquor and enhanced the fermentation capabilities.     

Laccase-initiated cross-linking of lignocellulose fibres using a ultra-filtered lignin isolated from kraft black liquor

In this work, the effect of Trametes pubescens laccase (TpL) used in combination with a low-molecular-weight ultra-filtered lignin (UFL) to improve mechanical properties of kraft liner pulp and chemi-thermo-mechanical pulp was studied. UFL was isolated by ultra-filtration from the kraft cooking black liquor obtained from softwood pulping. This by-product from the pulp industry contains an oligomeric lignin with almost twice the amount of free phenolic moieties than residual kraft pulp lignin. The reactivity of TpL on UFL and kraft pulp was studied by nuclear magnetic resonance spectroscopy and size exclusion chromatography. Laccase was shown to polymerise UFL and residual kraft pulp lignin in the fibres, seen by the increase in their average molecular weight and in the case of UFL as a decrease in the amount of phenolic hydroxyls. The laccase initiated cross-linking of lignin, mediated by UFL, which gives rise to more than a twofold increase in wet strength of kraft liner pulp handsheets without loosing other critical mechanical properties. Hence, this could be an interesting path to decrease mechano-sorptive creep that has been reported to lessen in extent as wet strength is given to papers. The laccase/2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) mediator system showed a greater increase in wet tensile strength of the resulting pulp sheets than the laccase/UFL system. However, other mechanical properties such as dry tensile strength, compression strength and Scott Bond internal strength were negatively affected by the laccase/ABTS system.     

Paenibacillus campinasensis BL11: a wood material-utilizing bacterial strain isolated from black liquor

In order to search for new thermophilic microorganisms and their enzymes, bacterial strains from black liquor of brownstock at washing stage of kraft pulping process were screened. Therein a multiple glycosyl hydrolase-producing strain, BL11, was isolated as a dominant species in the xylan-degrading bacterial population and identified as Paenibacillus campinasensis. The bacterial strain used all kinds of saccharides and polysaccharides, except lignin as carbon source and produced multiple extracellular polysaccharide-degrading enzymes, including one xylanase (41 kDa), three cellulases (42, 57 and 86 kDa), one pectinase (28 kDa) and one cyclodextrin glucanotransferase (38 kDa). P. campinasensis BL11 lacked lipase and protease activities and was able to grow over a wide range of pH, but it particularly grew well around neutral pH at 55 degrees C. Based on its physiological characteristics, it has strong potential for industrial application and bioresource utilization.     

Enhanced remediation of black liquor by activated sludge bioaugmented with a novel exogenous microorganism culture

Black liquor (BL) is a notoriously difficult wastewater to treat due to the economic and efficiency limitations of physiochemical methods and intrinsic difficulties with bioremediation strategies caused by the high pH (10–13) and lignin content. This study investigated the feasibility of a novel bioaugmentation strategy for BL treatment, which uses a mixed microorganism culture of lignocellulose-degrading microorganisms isolated from degraded bamboo slips. Black liquor treatment was assessed in terms of chemical oxygen demand (COD) and color removal with a sequencing batch reactor organic loading rate of 9 kg COD/L·day under highly alkaline conditions (pH?10). Results revealed that bioaugmented activated sludge treatment of BL with special mixed microorganisms significantly enhanced the removal efficiency of COD, color, and lignin from the wastewater up to 64.8, 50.5, and 53.2 %, respectively. Gel permeation chromatography profiles showed that the bioaugmentation system could successfully degrade high molecular lignin fragments in black liquor. This work confirms bioaugmentation as a feasible alternative strategy for enhanced biological treatment of wastewater with high lignin content and high organic load rate under strongly alkaline conditions.     

Influence of pressure on pyrolysis of black liquor: 2. Char yields and component release

This is the second in a series of papers concerning the behavior of black liquor during pyrolysis at elevated pressures. Two industrial black liquors were pyrolyzed under pressurized conditions in two laboratory-scale devices, a pressurized single-particle reactor and a pressurized grid heater. Temperatures ranging between 650 and 1100 degrees C and pressures in the range 1-20 bar were studied. Char yields were calculated and based on analysis of some of the chars the fate of carbon, sodium, potassium and sulfur was determined as a function of pyrolysis pressure. At temperatures below 800 degrees C little variation in char yield was observed at different pressures. At higher temperatures char yield increased with pressure due to slower decomposition of sodium carbonate. For the same reason, sodium release decreased with pressure. Sulfur release, however, increased with pressure primarily because there was less opportunity for its capture in the less-swollen chars.     

Alkaline subcritical water gasification of dairy industry waste (Whey)

The near-critical water gasification of dairy industry waste in the form of Whey, a product composed of mixtures of carbohydrates (mainly lactose) and amino acids such as glycine and glutamic acid, has been studied. The gasification process involved partial oxidation with hydrogen peroxide in the presence of NaOH. The reactions were studied over the temperature range from 300°C to 390°C, corresponding pressures of 9.5-24.5 MPa and reaction times from 0 min to 120 min. Hydrogen production was affected by the presence of NaOH, the concentration of H(2)O(2), temperature, reaction time and feed concentration. Up to 40% of the theoretical hydrogen gas production was achieved at 390°C. Over 80% of the Whey nitrogen content was found as ammonia, mainly in the liquid effluent.     

Assessment of current status and the potential for commercial exploitation of biomass gasification in India

India would seem to present a unique opportunity for large scale commercial exploitation of biomass gasification technology for meeting a variety of energy needs, particularly in the agricultural and rural sector. The combination of favourable parameters includes a clear-cut national commitment, prevailing power shortages and high cost of power, vast geographical expanse, specific applications like irrigation pumping and rural electrification as well as availability of the essential infra-structural base. The country already has more than 250 systems covering a spectrum of power ratings and end use applications and while the overall experience has been favourable, a number of problem areas have already been identified for corrective action. While the paper discusses applications like irrigation pumping, village electrification and pump-set energisation in some detail, other significant applications include captive industrial power generation and MW scale grid-fed power generation coupled to energy plantations on wastelands. Economic viability of the available systems is seen to be acceptable to marginal depending on the assumptions made and perspective chosen i.e., macro national policy perspective vis-à-vis micro, individual user perspective. While the entire situational setting is seen to be quite attractive for deployment of this technology, a number of likely constraints in commercial exploitation are identified and discussed. However, a majority of these can be suitably tackled and the overall perception for commercial exploitation of biomass gasification technology would seem to be quite bright for India.