Back-pressure regulator

Fig. 8. Fluid-bed MTG demonstration plant schematic diagram. BPR = Back pressure regulator TC = temperature controller.

The Back Pressure Regulator (BPR) shown at the end can be a gas dome-loaded Grove Inc. regulator or a spring-loaded Tescom model. The same holds for the forward pressure regulators. Instead of regulators, controllers can be used too, especially since small electronic control valves are now available. 

The total feed flow is set for a higher level than it is needed for the experiment. The excess feed is released by a back pressure regulator (BPR at the bottom of the picture), e.g., at 21 atm and is led to the analyzer. The... 

Figure 14.10 Schematic diagram of the aromatics analyser system BP, back-pressure regulator CF, flow controller CP, pressure controller Inj, splitless injector with septum purge V, tliree-way valve column I, polar capillary column column 2, non-polar capillary column R, restrictor FID I, and FID2, flame-ionization detectors.

Figure 9.5 Back pressure regulation valve assembly all functions -two temperature regulators (CVT) and solenoid (EVM) (Courtesy of Danfoss)...

Back pressure regulation valves (Figure 9.5) can be used in the suction line, and their function is to prevent the evaporator pressure falling below a predetermined or controlled value, although the compressor suction pressure may be lower. 

A service gauge is usually fitted adjacent to the valve or as part of the valve assembly, to facilitate setting or readjustment. Above about 40 mm pipe size, the basic back pressure regulation valve is used as a pilot to operate a main servo valve. Other pilot signals can be used on the same servo. 

Figure 10.2 Use of back pressure regulating valve to maintain evaporator pressure (and temperature)...

Figure 5.28 Schematic of the experimental set-up. Water/ethylene glycol/SDS reservoir (a) high-pressure liquid pumps (b) catalyst/ substrate HPLC injection valve with 200 pi sample loop (c) hydrogen supply, equipped with mass flow controller (d) micro mixer (e) heating jacket (f) tubular glass or quartz reactor (g) back-pressure regulator (h) [64],...

II- Zero dead volume SSI Flow-Through Back-Pressure Regulator maintaining in the reactor pressure about 4 bars, 12- container for products. 

Implementation of SFC has initially been hampered by instrumental problems, such as back-pressure regulation, need for syringe pumps, consistent flow-rates, pressure and density gradient control, modifier gradient elution, small volume injection (nL), poor reproducibility of injection, and miniaturised detection. These difficulties, which limited sensitivity, precision or reproducibility in industrial applications, were eventually overcome. Because instrumentation for SFC is quite complex and expensive, the technique is still not widely accepted. At the present time few SFC instrument manufacturers are active. Berger and Wilson [239] have described packed SFC instrumentation equipped with FID, UV/VIS and NPD, which can also be employed for open-tubular SFC in a pressure-control mode. Column technology has been largely borrowed from GC (for the open-tubular format) or from HPLC (for the packed format). Open-tubular coated capillaries (50-100 irn i.d.), packed capillaries (100-500 p,m i.d.), and packed columns (1 -4.6 mm i.d.) have been used for SFC (Table 4.27). 

Pressure regulator. The split inlet is back pressure regulated to ensure a constant head pressure, therefore, a steady flow through the column. For capillary columns, the inlet pressure determines the column flow, as per Eq. (14.11). As the inlet operates, the split vent can be opened or closed or upstream gas flow may change the regulator maintains the desired pressure, therefore the desired column flow. 

Fig. 11 Extraction device consisting of A CO2 cylinder, B syringe pump, C oven, D extraction cell, E particle filter, F back-pressure regulator, G sampling tube...

Dissolved air flotation equipment is available from a number of manufacturers. Packaged units of steel construction are available with capacities to 7.6 cu m/min (2000 gpm). The essential elements of the DAF system are the pressurizing pump, air injection facilities, pressurization tank or contact vessel, back-pressure regulating device, and the flotation chamber [40]. 

Figure 3.10 exemplifies the application of packed-column SFC for the rapid determination of the enantiomeric purity of pharmaceutical materials. The method employed a CHIRALCEL OD CSP with a carbon dioxide/methanol/ isopropylamine mobile phase under isocratic conditions. A flow rate of 4 mFmin was used to generate a high linear velocity whilst maintaining an outlet pressure of 200 bar by use of a back-pressure regulator to ensure reproducible chromatography. Baseline resolution of the enantiomers of propanolol was achieved in approximately 3 min with an overall cycle time of 4 min. Detection was by UV... 

Figure 3.10 Determination of the enantiomeric purity of propranolol API using packed-column chiral SFC. Distomer content measured at 0.04% by area. (Conditions CHIRALCEL OD 25 cm X 0.46 cm i.d. mobile phase carbon dioxide methanol containing 0.5% isopropylamine [70 30, v/v isocratic] flow rate 4 ml/min constant outlet back-pressure regulator 200 bar detection UV at 220 nm column temperature 30 C injection volume 10 fil.)...

EV = extraction vessel HE = water bath TV = two-way through valve TC = thermocouple BPR = back pressure regulator ... 

The SFE process was carried out in a JASCO system. For each run, which lasted for an hour, 0.5g of the as-synthesised HMS was being loaded into the extraction cell housed in an oven. The system uses a HPLC and a syringe pump for pumping liquid CO2 and the modifier (methanol) respectively so as to build up the system pressure. The desired system pressure was set and controlled by a back pressure regulator while the system temperature was set and controlled by the temperature controller attached to the oven. The extracted amine surfactant is collected in a vial placed at the outlet of the back pressure regulator. 

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