Conventional high-rate

Thickener Types Flocculants are commonly used in thickeners, and this practice nas resulted in thickener classifications as conventional, high-rate, ultrahigh-rate, or high-density. These designations can be confusing in that they imply sharp distinction between each type, which is not the case. 

Conventional high-rate digestion under baseline operating conditions of 35 C digestion temperature, 0.1 lb VS/ft -day loading and a 12-day detention time. 

Steady-state performance of conventional high-rate mesophilic digestion of the biomass-waste blend at the baseline loading and detention time is presented in Table I. The methane yields from replicate baseline runs ranged... 

Methane yield decreased to 2.4 SCF/lb VS added (43.8% of theoretical yield) when the loading rate was increased to 0.18 lb VS/ft -day and the detention time decreased to 9 days (Table I). These data indicate that conventional digestion process efficiency would decrease substantially as the loading rate is increased and the detention time is decreased beyond the baseline values of these parameters. Unconventional or advanced digestion methods are thus needed to overcome the limitations of the conventional high-rate process. 

Film. By far the largest appHcation for LLDPE resins (over 60% in the United States) is film. Because LLDPE film has high tensile strength and puncture resistance, it is able to compete with HDPE film for many uses. The toughness and low temperature properties of LLDPE film also exceed those of conventional LDPE. Furthermore, because LLDPE resins exhibit relatively low strain hardening in the molten state and lower extensional viscosity, it can be produced at high rates with Httle risk of bubble breaks. 

FIG. 18-87 Unit area vs. flocciilant dose, illiistrating the relationship between conventional and high-rate thickeners. 

In the McCoy table of recommended concentrations of boiler salines, the guidelines for pressures from 100 to 900 psi apply to conventional field-erected boilers with moderate rates of heat transfer, say, 50,000 Btu/hr/ft2. At high rates characteristic of packaged boilers, large amounts of insoluble material cannot be managed effectively by any dispersant presently available. 

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