Methane flow counter

Fig. 80. Methane flow counter 1) = High-voltage input 2) = Insulator 3) = Gas outlet = Gas inlet 5) - Brass plate 6) = Counting chamber 7) = Counting loop 8) = Sample 9) = Screw cap (after G. Tralan, Roentgen-Blatter 12/1960)...

Methane flow counters have an efficiency of around 50 %, on account of the positive geometry of the measuring unit. The zero effect in flow counters is in the region of 20 pulses/min., but this counter equipment can nevertheless compete successfully with an anticoincidence circuit as a result of its high efficiency. 

Proportional counters and scintillation counters are used as detectors. The proportional counters should preferably be designed without windows and take the form of methane flow counters, ce-rays generally feature extremely high energy levels of several MeV, but only a very limited range. Water can thus not be measured directly, and instead it is necessary to achieve a concentration of Oi -emitting nuclides, with particular attention being paid to radium 226, but also to uranium and thorium. 

Separate off, dry and weigh the strontium carbonate. Measure the activity of the preparation using an end-window counter or a methane flow counter. Bear in mind the formation of yttrium 90 as a daughter product of strontium 90. Either perform a fresh hydroxide precipitation for purification purposes or make allowance for the fact that in the first few hours following separation the apparent activity of strontium 90 increases by roughly 1 % per hour. 

The benefit obtained from counter-flow depends on the particular separation, but it can often be substantial, particularly in gas separation and per-vaporation processes. A comparison of cross-flow, counter-flow, and counter-flow/sweep for the same membrane module used to dehydrate natural gas is shown in Figure 4.18. Water is a smaller molecule and much more condensable than methane, the main component of natural gas, so membranes with a water/methane selectivity of 400-500 are readily available. In the calculations shown in Figure 4.18, the membrane is assumed to have a pressure-normalized... 

Proportional counters may consist of a sealed cylinder serving as cathode, a thin wire as anode and a thin window, but they are often constructed as flow counters, as shown in Fig. 7.10. In this type of counter a gas, preferably methane or a mixture of argon and methane, flows through the counter during operation and the sample is brought into the counter. The operational voltage depends on the nature and the pressure of the gas and varies between about 2 and 4 kV. 

Gas-flow counters may operate as proportional or GM counters. In fact, there are commercial models that may operate in one or the other region depending on the voltage applied and the gas used. In a proportional gas-flow counter, the gas is usually methane or a mixture of argon and methane. In the GM region, the gas is a mixture of argon and isobutane. 

A suitable aliquot is pipetted onto a platinum (or stainless steel) plate and evaporated to dryness under an infrared heat lamp. The plate containing the evaporated sample aliquot is heated to a dull red heat over a Fisher burner to destroy organic matter and counted in a stiitable alpha coimter. In this laboratory, the methane flow proportional alpha counter is used almost exclusively. 

However, many reactions of commercial interest have chemistry, mechanical, or system requirements that preclude the use of cross-flow reactors. Processes cannot use a cross-flow orientation primarily because of high temperatures and the need to internally recuperate heat such as steam methane reforming (SMR) [12, 13] and oxidation reactions [14]. Counter- and coflow devices require a micromanifold to dehver sufficiently uniform flow to each of the many parallel channels. 

Let us reconsider the critical flame temperature criterion for extinction. Williams [25], in a review of flame extinction, reports the theoretical adiabatic flame temperatures for different fuels in counter-flow diffusion flame experiments. These temperatures decreased with the strain rate (ua0/x), and ranged from 1700 to 2300 K. However, experimental measured temperatures in the literature tended to be much lower (e.g. Williams [25] reports 1650 K for methane, 1880 K for iso-octane and 1500 K for methylmethracrylate and heptane). He concludes that 1500 50 K can represent an approximate extinction temperature for many carbon-hydrogen-oxygen fuels burning in oxygen-nitrogen mixtures without chemical inhibitors . 

Development of Advanced Reservoir Characterisation and Simulation Tools for Improved Coalbed Methane Recovery. Led by Imperial College of Science Technology and Medicine, the main objective of this project is to develop technology and tools to more accurately assess the potential for improved methane recovery and COj sequestration by investigating the basic scientific phenomena of COj coal injection and retention. The researchers primary objective is to achieve a more comprehensive understanding of the fundamental mechanisms of water and CO2-CH4 adsorption/desorption, diffusion/counter diffusion, and 2-phase flow under simulated reservoir conditions (stress, pore pressure, and temperature). The results of these studies will then be applied to design of a CO2-ICBM recovery and COj sequestration simulator for the European industry. 

The plutonium solution concentration was determined by alpha counting 0.5-ml. aliquots evaporated to dryness on planchets. Gas flow internal proportional counting was used with 90% argon-10 % methane gas and Nuclear Measurement Corp. counters. 

Detector copper—xenon-sealed proportional counter silver, gold, and lead—flow proportional counter using 10% methane and 90% argon. 

Figure 4.18 Comparison of (a) cross-flow, (b) counter-flow and (c) counter-flow sweep module performance for the separation of water vapor from natural gas. Pressure-normalized methane flux 5 x 10 6cm3(STP)/cm2 s cmHg membrane selectivity, water/methane 200...

Part of the stream is washed counter currently with a feed side stream in the vent absorber (9) for benzene recovery. The absorber overhead flows to the hydrogen purification unit (10) where hydrogen purity is increased to 90%+ so it can be recycled to the reactor. The stabilizer (11) removes light ends, mostly methane and ethane, from the flash drum liquid. The bottoms are sent to the benzene column (12) where high-purity benzene is produced overhead. The bottoms stream, containing unreacted toluene and heavier aromatics, is pumped to the recycle column (13). Toluene, Cg aromatics and diphenyl are distilled overhead and recycled to the reactor. A small purge stream prevents the heavy components from building up in the process. 

The tube with a variable length of 10 - 15 m and a variable iimer diameter of 100 - 150 mm was entered at the bottom by helium of 950 °C which flowed upwards in an annulus at the outside providing heat to the reformer tube inside. The feed gas methane was heated up in a counter current flow and reached a temperature of 825 °C at the tube bottom. The resulting product gas was then cooled down by flowing upwards again through return pipes inside the reformer tube (internal pigtails). The temperature profiles in the EVA system are shown in Fig. B-2, left hand side. 

The BTMs are instruments deigned to detect and measure the tritium present in a mixture of radioactive gases. The BTM uses a gas-flow proportional counter tube with a volume of 1.3 liters. The proportional counter tube uses P-10 as tiie counting gas. P-10 is a mixture of 90 percent argon and 10 methane gas. The BTM detects tritium by using the rise-time... 

The sensitivity of these instruments for a particular radioisotope depends on the nature of the detector. Open methane gas-flow proportional counters give the highest count yields and have the additional... 

Zonal scanning is a most sensitive detection procedure, also for H-labeUed substances. The resolution of the method for scraping off and measuring 1 mm zones, is substantially better than directly recording the activity in a 6-M-counter or a methane gas flow proportional counter and nearly as good as with autoradiography. The first two methods mentioned are compared in Fig. 89. 

Fig. 89. Comparison of the sensitivity and resolution in direct activity determination on the layer using a methane gas flow proportional counter B) and a liquid scintillation counter (A) measurements on zones scraped from the same thin-layer chromatogram [646]...

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