Cold Product Research Articles

Pulverized coal combustion and gasification in a cyclone reactor. 2. Model and comparison with experiment

This paper describes a macroscopic, isothermal model for pulverized coal combustion in a cyclone reactor. Fuel-rich gasification without steam addition is also considered through a gas-phase equilibrium treatment. Fluid mechanics are modeled by a particle force balance and a series combination of a perfectly stirred reactor and a plug flow reactor. Kinetic treatments of coal pyrolysis, char oxidation, and carbon monoxide oxidation are included. The model predicts carbon conversion efficiency and product gas composition; gasification parameters, such as cold and hot gas efficiency and product gas heating value, are calculated for fuel-rich conditions. Extensive comparisons between the model predictions and experimental results are presented. The experiments were carried out in a laboratory-scale, atmospheric pressure cyclone reactor. Air flowrates ranged from 25 to 100 kg/h, coal feed rates from 4 to 14 kg/h, and equivalence ratios from 0.67 to 2.4. The level of agreement between experiment and theory was satisfactory; discrepancies are discussed in terms of possible revisions to the model or more detailed experiments.

Transcriptional activity in lysates of cultured mesenchymal cells from embryonic tooth germs.

Mesenchymal cells isolated from the papilla of embryonic tooth germs of the mouse were cultured in a complex medium for five to six days. Liquid nitrogen lysates, prepared from these cells, incorporated nucleoside monophosphates into a cold acid-insoluble product. The product was sensitive to RNase and no product was formed if the lysate was pretreated with DNase. The reaction was sensitive to EDTA and, in its presence, optimum activity was obtained with 2 mM MgCl2. On sucrose gradients, the reaction product was distributed between two broad peaks; one centered about 18S and the other above 28S. The RNA polymerase inhibitor alpha-amanitin inhibited approximately 50% of the activity at a concentration of 10 microgram/ml.

A histoenzymatic study of rat intrafusal muscle fibres

The histochemical activities of myofibrillar adenosine triphosphatase (ATPase), succinic dehydrogenase (SDH) and alpha glycerophosphate dehydrogenase (alpha-GPD) were studied in intrafusal muscle fibres of rat fast and slow muscles. The ATPase reaction was carried out after the three standard acid preincubations. The cold K2-EDTA preincubated ATPase reaction product was similar to that seen following the regular or alkali-preincubated ATPase reaction, except that the intermediate bag fibres exhibited much higher activity after cold K2-EDTA preincubation. Following either acetic acid solution or cold and room temperature K2-EDTA-preincubation, followed by the ATPase reaction, chain fibres of the fast muscles vastus lateralis and extensor digitorum longus exhibited a very low amount of reaction product as compared with those of the slow soleus. Veronal acetate and K2-EDTA preincubations (and equally preincubation in acetic acid solution) resulted in acid stable ATPase activity along the entire length of the typical bag fibres but only in the polar regions of the intermediate bag fibres. On the basis of differing alpha-GPD reaction, two sub populations of nuclear chain fibres were discovered in one spindle. It is a matter of conjecture, to what extent the histochemical differences of intrafusal fibres from fast and slow muscles reflects functional distinctions in the response to stretch of muscle spindles from fast and slow muscles.

Some properties of a DNA-dependent RNA polymerase from Halobacterium cutirubrum.

A DNA–protein–membrane complex, which incorporated ribonucleoside triphosphates (rNTP's) into a cold trichloracetic acid insoluble product, was isolated from an homogenate of the extremely halophilic Halobacterium cutirubrum by high speed centrifugation. After digestion with DNase and chromatography on a Sephadex column, the complex yielded an enzyme preparation which incorporated rNTP's in the presence of added DNA. Incorporation by both the complex and the enzyme preparation depended on all four rNTP's and was sensitive to DNase and RNase. Nearest-neighbor analyses showed that the product from the partially purified enzyme contained all four rNTP's in roughly equal proportion. The enzyme was inhibited by actinomycin D and acriflavin but not by rifampicin or streptovaricin. It showed no specificity for DNA templates. From Sephadex chromatography and centrifugation on glycerol gradients, its molecular weight was estimated to be roughly 300 000 – 400 000 daltons.For incorporation, the optimum Mg2+ concentration was 40 mM. The complex was active at all concentrations of KCl or NH4Cl up to saturation, but the partially purified enzyme was active only below 0.4 M. The lack of activity at higher concentrations was not due to irreversible denaturation of the enzyme but concentrated salt may have inhibited the reaction by altering the configuration of the DNA template.

Radiochemical analysis of corrosion product mixtures from high temperature pressurized water loop systems

This paper describes the various types of samples of activated corrosion products obtained from the high-temperature pressurized water-loop facilities in the NRX reactor and the radiochemical procedures and radioactivity assay methods which are used in analysis of these samples.Typically, in-pile loops are simulated reactor systems, i.e. they consist of a primary flowing coolant system and auxiliary make-up, purification, sampling and cooling systems. Two of the loops in NRX, namely, the carbon steel English Electric Corporation “Leo” loop and the Bettis Atomic Power Laboratory central thimble CR-V Loop, are described with particular attention to their associated sampling facilities: autoclaves and out-pile test sections for corrosion and corrosion product deposition studies, hot and cold corrosion product filters for filtration of insoluble materials, and ion exchange columns for purification of the loop water and the study of the ion-exchange behaviour of activated water-borne corrosion and fission products.The types of samples obtained and the method of attack used to separate and isolate specific fractions of the mixed corrosion products are described. In particular, the separation scheme devised is one which permits the isolation of elements of the first transition series and their associated activated impurities from one another. The separation is basically an anion exchange technique involving the successive elution of carrier-equilibrated species.Resin samples from the loop purification system are attacked in the presence of carriers by either digestion with H2SO4-HNO3 or by alkaline fusion.In some cases, corrosion product deposits are assayed directly for activity distribution by means of gamma-scintillation spectrometry (differential pulse height analysis). Application of composite gamma-ray spectrum resolution to deposition coupons and pipe samples is described.The radionuclides found in loop water and in unfilterable corrosion products are mainly radiative neutron capture products of the corroded in-pile and out-pile materials. The main nuclides analyzed for are 45.1 d Fe59, 5.25 y Co60, 27.8 d Cr51, 12.8 h Cu64, 2.58 h Mn68, 2.56 h Ni65, 245 d Zn65 and 65 d Zr95. Fast neutron reactions have been also observed through the appearance of 300 d Mn54 and 72 d Co58. Two radionuclides observed in the water and in solid corrosion products are 60 d Sb124 and 2.8 d Sb122. The source of these radionuclides has not been positively identified. The corrosion products from the CR-V loop also contain 253 d Ag110m, 43 d Cd114m and 50 d In114m arising from the corrosion of an in-pile specimen of a Ag-In-Cd alloy.Radioactivity assay of the purified fractions from separated samples is mainly by γ-ray scintillation spectrometry. Routine activity assay utilizing comparison with standardized differential pulse height distributions for pure radionuclides has been adopted because of the versatility of its use for both separated and gross samples. Conventional end-window beta-proportional counting techniques are used for those nuclides whose decay modes and energies preclude gamma-ray intensity assay techniques.The complexity of corrosion product mixtures from in-pile loops requires that stringent control be maintained at all phases of the program from the time of sampling to the time radioactivity assay is completed. Several problem areas are discussed. For example, large amounts of Fe59 contaminating Co60 samples and Zr95 contamination of Mn54, are difficult to detect without considerable scrutiny of counting data. Carrier exchange is difficult to effect in some cases: e.g. Zr96-ZrN exchange. The gamma-counting data in particular receive careful scrutiny. The gravimetric assay of carrier yield is in some cases a doubtful and time-consuming operation ; therefore, techniques eliminating gravimetric procedures should be explored.