Digestion control

Digester Control For control purposes at constant sulfidity and alkah charge, the deligniftcation rate is treated as a homogeneous reaction, which is first order with respect to the lignin, % remaining in the wood, —dL jdt = kL. The influence of time, t, and temperature, T (Kelvin), has been incorporated into one term, called the JT-factor (33). 

Extracellular peptidases are relatively easy to isolate and are, therefore, well-studied. In higher organisms, they perform a variety of different functions such as food digestion, control of blood pressure and blood clotting, and complement activation, among others. A few examples are compiled in Table 2.2. 

Once the analytical parameters have been determined from the method development and the method has proven suitable for routine measurements, internal quality control (IQC) procedures must be established to maintain the validity of the analytical scheme and to better monitor potential sources of errors. The IQC used includes pre- and post-digestion controls, blank determination, half range of the calibration graph checking, and recovery rate of the samples. The stability of the recovery rate with time (Fig. 1.4) shows that the method is robust after using... 

Browning BL (1967a) Methods of wood chemistry Vol. II. Interscience, New York, 785-823 Browning BL (1967b) Methods of wood chemistry Vol. I. Wilcy-Interscience, New York, 14 Bublitz WJ (1981) Fluorescence of pulping liquors a tool for digester control Tappi 64(6) 73-76... 

NH2-temiinus resulting in a mass of about 30 IdD and 3) an external peptide standard (450 pmol) that was provided dry in an eppendoiftube and that had the same amino acid composition as the unique tryptic peptide insert but whose sequence was randomized. In the case of the two protein samples, 70 pmol of each had been subjected to SDS PAGE and were supplied either as Coomassie Blue stained gel slices or as a section of amido black stained PVDF membrane. In the case of the PVDF samples, an oversize piece of PVDF was included so that a section could be used as a digest control, and in the case of the gel samples, a blank section of gel was included for the same purpose in a separate eppendorf tube. 

WJ Bubhtz. Fluorescence of Pulping Liquors A Tool for Digester Control Tappi 64 13-16, 1981. 

Potassium is analyzed in chemicals that are used in the fertilizer industry and in finished fertilizers by flame photometric methods (44) or volumetric sodium tertraphenylboron methods (45) as approved by the AO AC. Gravimetric deterrnination of potassium as K2PtClg, known as the Lindo-Gladding method (46), and the wet-digestion deterrnination of potassium (47) have been declared surplus methods by the AO AC. Other methods used for control purposes and special analyses include atomic absorption spectrophotometry, inductively coupled plasma (icp) emission spectrophotometry, and a radiometric method based on measuring the radioactivity of the minute amount of the isotope present in all potassium compounds (48). 

Technology has been introduced for on-line estimation of the kappa number based on absorption of ultraviolet light (35). This breakthrough ia optical sensor technology permits closed-loop feedback control of digesters from on-line measurement of the kappa number. 

The normal limit for lignin removal in the digester is set both by pulp strength requirements, usually indicated by pulp viscosity, and by yield requirements. As noted earlier, direct control of hydroxide and hydrosulftde concentrations can maximize lignin removal while maintaining pulp strength. 

Bile Acid Sequestrants. The bile acid binding resins, colestipol [26658424] and cholestyramine, ate also effective in controlling semm cholesterol levels (150). Cholestyramine, a polymer having mol wt > ICf, is an anion-exchange resin. It is not absorbed in the gastrointestinal tract, is not affected by digestive enzymes, and is taken orally after being suspended in water (151). 

Agricultural Use. Citric acid and its ammonium salts are used to form soluble chelates of iron, copper, magnesium, manganese, and zinc micronutrients in Hquid fertilizers (97—103). Citric acid and citrate salts are used in animal feeds to form soluble, easily digestible chelates of essential metal nutrients, enhance feed flavor to increase food uptake, control gastric pH and improve feed efficiency. 

An anaerobic digester is a no-recycle complete mix reactor. Thus, its performance is independent of organic loading but is controlled by hydraulic retention time (HRT). Based on kinetic theoiy and values of the pseudo constants for methane bac teria, a minimum HRT of 3 to 4 days is required. To provide a safety factor and compensate for load variation as indicated earlier, HRT is kept in the range 10 to 30 days. Thickening of feed sludge is used to reduce the tank volume required... 

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