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During the drying and pyrolysis phases of kraft black liquor combustion, significant swelling of individual liquor particles occurs. Swollen volumes can reach 20 to 30 times the original volume during combustion. The swelling process can conceivably affect the combustibility of black liquor and the amount of carryover in a recovery furnace.The composition of black liquor was found to have a large influence on swelling. A combination of sugar acids and kraft lignin swelled to a larger extent than when either component was pyrolyzed separately. A 1:1 ratio of these two components resulted in maximum swelling for the various ratios tested. The molecular weight of kraft lignin had an effect on swollen volume with higher molecular weight fractions producing lower swelling chars.Other components were found to reduce the swelling of black liquors. Extractives interfered with the swelling by appearing to change the deformable properties of the pyrolyzing material. Inorganic salts acted as a diluent.Analysis of the surface characteristics of chars revealed that good swelling chars were composed of small bubbles 50 to 150 microns in diameter. Poor swelling liquors did not exhibit this phenomenon. The formation of bubbles was found to be initiated at 240°C, which closely corresponded to the thermal decomposition temperature of a sugar acid. Kraft lignin appeared to have a major influence on the viscous properties of the pyrolyzing particle. The composition of black liquor determines to a large extent the surface active and viscous forces present in black liquor; these forces are believed to be responsible for the extent to which kraft black liquors deform and swell during pyrolysis.

China has water shortage problems, especially in its northern region. The accelerated industrialization in the country further compounds the issue. A drastic corrective measure is the South-North Water Diversion Project which will transfer 40 billion m 3 /year of water from the south to the north. Other less dramatic abatement measures are water pollution control and wastewater reuse practices.Severn Trent Services has participated in three projects in China that involve tertiary treatment of wastewater for reuse. One project in Dalian utilizes a fixed-film biological treatment technology (SAF TM ) and a deep bed sand filter (DeepBed TM ) for upgrading a municipal secondary effluent for various industrial reuses. The other two projects employ the same treatment technologies for potential recycle of wastewater for internal reuses in two petrochemical complexes.The SAF TM treatment technology and DeepBed TM filter system were proven to be technically efficient and cost effective for upgrading secondary effluent for reuse. The Dalian reuse plant with a capacity of 20,000 m 3 /day flow is producing a high quality reusable effluent with NH 4 -N at <1 mg/L, TSS < 1 mg/L and COD < 40 mg/L. The treatment plant owner is satisfied with an investment return of less than 3 years payback period. The end users realize about 60% cost savings by using the tertiary treated wastewater in place of potable water. The City of Dalian preserves the precious drinking water for domestic consumption and has sufficient fresh water to entice foreign investments to Dalian. It is a perfect model of a win-win policy.The treatment technology is also applicable to the upgrade of industrial wastewater for reuse. The pilot study at PetroChina Jinxi Petrochemical Plant No. 5 demonstrated that the technology was able to produce a high quality effluent for reuse with less than 1 mg/L of NH 4 -N, 5 mg/L of TSS and 80 mg/L of COD. If a COD standard of 40 mg/L is absolutely required for cooling water makeup, a physical/chemical treatment would have to be added.PetroChina Harbin Petrochemical Plant has an existing secondary activated sludge process and a tertiary treatment facility, which consists of chemical coagulation, sedimentation, granular filtration and granular activated carbon adsorption. The existing treatment plant cannot effectively remove ammonium nitrogen from the wastewater; plant effluent has an average ammonium nitrogen concentration of about 150 mg/L. The SAF TM process was able to nitrify the ammonium nitrogen to meet the reuse requirement of 1 mg/L or a discharge limit of 50 mg/L.

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