Modifier pump design

Modifier Pump. The first feature in our adapted design is the introduction of a liquid pump via an instrument controlled VALCO (Model E04, Valeo Instruments, Houston, TX), four position selection valve. We have used an LKB Model 2150, dual piston pump for pumping modifier and entrainer fluids (LKB-Produkter AB, Bromma, Sweden). However, any suitable liquid pump could be substituted. Only pure fluids such as carbon dioxide have been introduced with the Suprex system syringe pump. With the addition of this second pump to deliver liquids, modifier is introduced directly into the extraction vessel. A wide range of alternative fluids and fluid mixtures can be rapidly selected with this dual pumping option. The criteria for selection of a modifier pump include the ability of the pump heads to withstand pressures in the range of 100 to 300 atm and interfacing capabilities, i.e. the ability to be turned on and off by the Suprex contact closure controls. 

Above 25O F the pump design must be modified and more expensive packing glands must be used thus... 

The instrument was built by modifying the design of a TREF 300 unit (Polymer Char, Spain) which incorporates an oven used for sample preparation and a high precision TREF column oven. Other components are syringe pump, HPLC pump, high temperature isothermal oven (SEC oven) in which the injection valve, a multiposition selection valve and the SEC column set are placed. A dual band 1R4 infrared detector (Polymer Char, Spain) is used as the cOTicentration detector. 

Now, it s one thing to say to ii.se a pump with an NPSHr less than 2 feet. It s another thing to find a pump with this design parameter, that at the same time eomplies with the demands of the operation. Perhaps it will be neeessary to modify the system to increase the Hs2, reduce the Hf, or modify the pump to reduce the Hi. Other possible options are ... 

This is the beginning of many problems with pumps. A pump is sf d with at one set of system coordinates. Then the system (the TDH) goe " mi and the pump moves on its curve away from its BEP out to one or the oth( i It is necessary to determir- i -num and minimum tions in the design the pump within these elev ions. If the system continues to pump, you ll either have to modify t ... /stem or modify or change the pu.-you really like to change bearin, . .d seals. 

CANDU-9 is the next generation of CANDUs. It is a larger version of the CANDU producing 870 MWe, the CANDU-9 to complement the mid-size CANDU-6 with updated proven technology, a modified CANDU-6 station layout, improved construction methods and operational features. Standardization, a feature of CANDU reactors, is emphasized in CANDU-9 in the key components (steam generators, coolant pumps, pressure tubes, etc.) being the same design as those proven in service at CANDU power stations. 

As will be shown later the equation above is identical to the mass balance equation for a continuous stirred-tank reactor. The recycle can be provided either by an external pump as shown in Fig. 5.4-18 or by an impeller installed within the reaction chamber. The latter design was proposed by Weychert and Trela (1968). A commercial and advantageously modified version of such a reactor has been developed by Berty (1974, 1979), see Fig. 5.4-19. In these reactors, the relative velocity between the catalyst particles and the fluid phases is incretised without increasing the overall feed and outlet flow rates. 

In experiments which are carried out under normal pressure, the gaseous products are taken from a modified, commercially available low temperature furnace. The gas flows viscously in the specially designed capillary through an intermediate volume to the peristaltic pump. Hereby the gas pressure in the intermediate volume is reduced to approx. 1 mm Hg. By means of a variable... 

The different chemical compounds used as wax crystal modifiers do not all provide ideal performance under every circumstance. Various tests have been designed to help differentiate the performance of one wax crystal modifier over another. For example, a modifier may be quite effective at controlling wax crystal formation to enable a fuel to flow by gravity from a storage tank to a pump. However, once past the pump, the modifier may not effectively reduce the wax crystal size and shape to allow cold fuel to flow effectively through a line filter. The result is wax accumulation on the filter media, plugging of the fuel filter, and halting of fuel flow. A different wax crystal modifier or a product with wax dispersant properties may be required to permit effective fuel filtration. 

To avoid the problems with vacuum cleaner surface dust sampling a special surface dust sampler, HVS-3, was developed (Roberts et al, 1991). The sampler consists of a nozzle that can be adjusted to a well defined distance to the surface, a cyclone that collects the dust particles, an air pump, and an exhaust filter to capture particles that are not retained in the cyclone. SVOCs may break through the cyclone as vapors and a PUF plug can be inserted after the cyclone. HVS-3 has been modified to ensure a more constant suction pressure and volume, and a known sampled area (Gyntelberg et al, 1994). The design and use of the HSV3 has now been standardized (ASTM, 1997, D 5438-94). 

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