بهينه سازي طراحي گازگير لجن UASB به منظور افزايش سرعت در بستر لجن بدون تغيير سرعت در ناحيه ي زلال سازي

NOVEL UASB GAS-SOLID SEPARATOR DESIGN TO ENHANCE UPFLOW VELOCITY WITHOT INCREASED SLUDGE WASHOUT

In high-rate anaerobic wastewater treatment reactors such as up flow anaerobic sludge blanket (UASB) system, gas solids separator (GSS) plays a critical role in main­taining stability in reactor performance. Operational and performance problems of the current design include complexity and clogging of gas collection pipes due to sludge entry, excessive number of gas separators, and limitations on up flow velocities due to potential sludge washout. To overcome these problems, a new design is proposed in which the total volume of GSS is filled with gas-supernatant and flow is partially diverted to a side- basin adjacent to the main reactor. In this basin, gas is separated from supernatant, the remaining good sludge is settled and returned back to the reaction zone in the main reactor, and undesirable sludge and the associated flowr is returned to the influent pump station for recycle back into the bottom of reactor. Advantages of the new design include the possibility of increasing velocity in the blanket zone without chang­ing velocity in the clarification region. The degree of in­crease is dependent on the extent of flow diversion but an operational velocity of about 2.5 mhr~l is easily achiev­able even though much larger velocities arc theoretically possible. Inactive sludge accumulated outside the tur­bulent domain of inlet openings is also made available. Horizontal velocities of at least 20 mhr~l underneath GSS units due to flow into the side basin is a new phe­nomenon in the new design which further improves gas separation. Since lesser total overlap area is needed due to larger and fewer number of settlers in the reactor (re­duction factor of around 70%), more area for fluid flow is available resulting in lower inter-GSS velocities. Fur­thermore, larger settlers are easier and more economi­cal to construct and gas-collecting pipes and auxiliary appurtenances to secure GSS structures are eliminated with con sequent reduced capital and operating expenses.