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CEM-System Liquid Delivery System with Vapour Control0 pages
CEM
Liquid Delivery System with Vapour Control
Liquid Flow Control
Liquids
(selection of some references)
•tETOHt
•tSnCl4t
•tTiCl4
•tHMDSOt •tTCAt
•tTMB
•tHMDSnt •t TEOSt
•tWater
•tSiHCl3t
•t TIBAt
•tZn(C2H5)2
•tSiH3Cl
•tCupraselect™
•t
Organic compounds (such as Acetone, Alcohol,
Butanol, Ethanol, Hexane, Methanol, etc.)
Carrier Gas Control
CEM
Mixing chamber for
liquid and carrier gas
with heat exchanger
for total evaporation
> Introduction
In a number of processes two or more components must be mixed
together. In instances where it comprises a vapour of a liquid in a
carrier gas, traditional Bubbler Systems and the more recent Vapour
Source Controllers have been used. These devices, however, can often
not handle sufficient quantities of liquid with a low vapour pressure, or
perform in an imperfect way. Moreover, they cannot instantaneously
provide vapour of a mixture of liquids with different vapour pressures.
Bronkhorst High-Tech B.V. have therefore developed a unique patented
system to realise Mass Flow Control of Vapours with an innovation: the
CEM-Liquid Delivery System (LDS). It can be applied for atmospheric,
pressurized and vacuum processes, vaporising liquid flows from 0,25 to
1200 g/h of water; for most other fluids the maximum capacity will
even be higher.
> Description
At room temperature the liquid, for instance TEOS, HMDSO,
CupraselectTM or water, is drawn from a container with an inert gas
blanket, or membrane, and measured by a liquid mass flow meter
type µ-FLOW, LIQUI-FLOWTM or mini CORI-FLOWTM. The required flow
rate is controlled to the setpoint value by a control valve (C) forming an
integral part of the patented liquid flow and carrier gas mixing valve
(M). The then formed mixture is subsequently led into the evaporator to
achieve total
evaporation (E). This explains the abbreviation of CEM viz.:
Control - Evaporation - Mixing, the 3 basic functions of the Liquid
Delivery System.
A complete system also incorporates a readout/control unit,
including power supply, for operation of the CEM-system devices.
> Features
ut ccurately controlled gas/liquid mixture
a
utfast response
uthigh reproduceability
ut ery stable vapour flow
v
utlexible selection of gas/liquid ratio
f
utower working temperature than conventional systems
l
ut ptional control by PC/PLC (RS232/fieldbus)
o
