U.S. patent application number 12/438220 was filed with the patent office on 2010-04-08 for method for reacting self-igniting dusts in a vacuum pump device.
This patent application is currently assigned to OERLIKON LEYBOLD VACUUM GMBH. Invention is credited to Thomas Dreifert, Uwe Zollig.
Application Number | 20100086883 12/438220 |
Document ID | / |
Family ID | 38792066 |
Filed Date | 2010-04-08 |
United States Patent
Application |
20100086883 |
Kind Code |
A1 |
Zollig; Uwe ; et
al. |
April 8, 2010 |
METHOD FOR REACTING SELF-IGNITING DUSTS IN A VACUUM PUMP DEVICE
Abstract
Into a vacuum pump device arranged for suctional intake of a
process gas (38) possibly comprising reactive particles (40),
oxygen in the form of air or pure oxygen is supplied in a
controlled manner via an oxygen intake (26, 26a,26b). Thus,
controlled oxidation takes place in the compression chamber (24)
such that the dust cannot self-ignite in case of sudden
ventilation.
Inventors: |
Zollig; Uwe; (Koln, DE)
; Dreifert; Thomas; (Kerpen, DE) |
Correspondence
Address: |
FAY SHARPE LLP
1228 Euclid Avenue, 5th Floor, The Halle Building
Cleveland
OH
44115
US
|
Assignee: |
OERLIKON LEYBOLD VACUUM
GMBH
KOLN
DE
|
Family ID: |
38792066 |
Appl. No.: |
12/438220 |
Filed: |
August 7, 2007 |
PCT Filed: |
August 7, 2007 |
PCT NO: |
PCT/EP2007/058199 |
371 Date: |
October 13, 2009 |
Current U.S.
Class: |
431/12 ;
137/565.11 |
Current CPC
Class: |
Y10T 137/85986 20150401;
F04C 29/0092 20130101; F04D 19/04 20130101; F04C 28/28 20130101;
F04C 2280/02 20130101; F04D 3/02 20130101; F04C 18/16 20130101;
F04C 2220/12 20130101 |
Class at
Publication: |
431/12 ;
137/565.11 |
International
Class: |
F23N 3/00 20060101
F23N003/00; E03B 5/00 20060101 E03B005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 23, 2006 |
DE |
10 2006 039 529.8 |
Claims
1. A method for exhaustive reaction of self-igniting dust in a
dry-sealed vacuum pump device, comprising: during operation of the
vacuum pump device, continuously supplying oxygen thereto in a
dosed manner, whereby an oxidation of the dust is effected.
2. The method according to claim 1, wherein said supplying of
oxygen takes place at at least one of an entrance of the vacuum
pump device and in the feed lines of the vacuum pump device.
3. The method according to claim 1, wherein said supplying of
oxygen takes place along a compression chamber of the vacuum pump
device.
4. The method according to claim 1, wherein said supplying of
oxygen takes place along or between at least two compression
chambers.
5. The method according to claim 1, wherein the supplying of oxygen
is performed at an exit or in exhaust lines of the vacuum pump
device.
6. The method according to claim 1, wherein the supplying of oxygen
is performed via a settable or controllable throttle valve.
7. The method according to claim 1, further including: terminating
supplying a process gas for condensation, and continuing the
supplying of an oxygen-containing gas mixture, for cleaning the
pump device and the supply lines from dust and for exhaustive
reaction of the dust.
8. A dry-sealed vacuum pump device comprising: at least one driven
compression member; and a housing with a pump entrance and a pump
exit, one of said housing or a line connected thereto comprises at
least one gas and respectively oxygen intake provided with a
throttle valve for regulating an entrance cross-section.
9. The vacuum pump device of claim 8, further including: at least
one of temperature sensors and pressure sensors in a chamber in
which dust is oxidized to monitor a dust oxidation reaction.
10. A method of reacting exhaust dust in a dry-sealed vacuum
device, comprising: with a dry-sealed vacuum device, sucking in a
process gas with flammable dust; introducing oxygen into the
exhaust gas in or adjacent the dry-sealed vacuum device;
compressing the process gas with flammable dust and the oxygen in a
compression chamber of the dry-sealed vacuum device; oxidizing the
flammable dust with the introduced oxygen in the dry-sealed vacuum
device; and discharging the process gas and oxidized dust.
Description
BACKGROUND
[0001] The invention relates to a method for exhaustive reaction of
self-igniting dust in a dry-sealed vacuum pump device, as well as a
corresponding vacuum pump.
[0002] In metallurgical and various other processes performed in a
vacuum environment, it is frequently the case that particles or
fine dust are generated, which due to their chemical composition
and their large surface are so reactive that they will self-ignite
upon contact with ambient air, thus entering an exhaustive reaction
with the aerial oxygen. Examples of such processes are the
Czochralsky method for producing silicon monocrystals, or the
melting and degassing of steels. In the first case, silicon oxide
(SiO) is generated, and in the second case, metallic fine dust such
as e.g. magnesium dust, are generated. The dust particles are
sucked into the vacuum pump which generates the vacuum required for
the process. In oil-sealed vacuum pumps, the dust particles are
absorbed by the lubricant and will not be discharged from the pump.
Since the particles are mostly very hard and together with the oil
will act like a grinding agent, this will often lead to massive
wear within the vacuum pump. In dry-sealed vacuum pumps, on the
other hand, such as e.g. screw-type vacuum pumps, the massive
reaction upon sudden contact with oxygen involves a danger of
explosions. Therefore, in both cases, the assemblies are provided
with complex dust filters which will filter out the dust upstream
of the vacuum pump. The dust will accumulate within the dust
filter, whereby, however, the danger of explosion is not
eliminated. In dry-sealed pumps, there is also a possibility of
dust accumulating on the exhaust side of the vacuum pump.
[0003] The dust also causes a safety hazard to the maintenance
personnel of the systems because, in case of faulty operating or
unintentional venting of the system, inflammation of the dust
cannot be excluded. Such an inflammation may even occur in the
filter or in the tubing.
[0004] It is an object to provide a method for exhaustive reaction
of self-igniting dust in a dry-sealed vacuum pump, which method
shall effect a continuous oxidation of the reactive dust within the
vacuum pump, so that the vacuum pump per se is simplified and the
working processes to be performed at the vacuum pump are made
safer.
[0005] During operation of the vacuum pump device, oxygen is
continuously supplied thereto in a dosed manner, whereby an
oxidation of the dust is effected.
SUMMARY
[0006] One aspect provides a well-aimed exhaustive reaction of
oxidizable dust in the vacuum pump. Thus, for instance, silicon
oxide (SiO) is oxidized to silicon dioxide (SiO.sub.2), and metals
are oxidized to metal oxides. Since it is substantially gas that is
conveyed by the vacuum pump and since the absolute mass flow of
dust per time unit is relatively small, the present method offers
the possibility to accomplish a continuous and controlled
exhaustive reaction of the reactive dust. Uncontrolled inflammation
of the dust is reliably prevented. The supplying of oxygen can be
provided in the form of pure oxygen or in the form of air. The
oxygen supply will affect the suction performance of the pump only
to a mere negligible extent. The dust quantity introduced into the
vacuum pump per time unit is small enough to be continuously burned
with a relatively low air-gas ballast while this burning process
will not cause damage to the pump. All of the particles leaving the
pump again on the pressure side will have undergone an exhaustive
reaction. Consequently, a separation of dust can be performed by
use of normal dust filters on the pressure side without a danger of
uncontrolled reactions. This allows for a simplified and less
expensive installation of the vacuum pump. Possible accumulations
of dust in the tubing on the exhaust side will not be reactive
anymore and thus will be of no concern under the aspect of safety
technology.
[0007] The supplied oxygen-containing gas can be fed into the
vacuum pump device at a suitable site, e.g. into the pumping
chamber at the entrance to the pump, at a site along the
compression chamber, or at the pump exit.
[0008] Another aspect relates to a dry-sealed vacuum pump device
comprising at least one driven compression member and a housing
with pump entrance and pump exit. The vacuum pump is characterized
in that the housing comprises at least one oxygen entrance provided
with a throttle valve for regulating the cross section of the
entrance.
[0009] Possible embodiments of a dry-sealed vacuum pump are the
following: screw pumps, claw-type pumps, Roots pumps, turbo
compressors, lateral-channel blowers, dry-sealed rotary-vane pumps,
and others.
[0010] The vacuum pump device can comprise a sole vacuum pump, or a
plurality of pumps connected in series and each forming a pump
stage. The oxygen can also be introduced into a reaction chamber
arranged between two pump stages. As a reaction chamber, use can be
made also of a tube conduit.
[0011] According to a modified embodiment, temperature and pressure
sensors are provided for monitoring the reaction in the vacuum pump
device.
[0012] A method for cleansing the vacuum pump device and the feed
conduits from dust can reside in that, after the end of the
process, the supply of process gas is terminated while the supply
of an oxygen-containing gas mixture, e.g. air, through the pump
device is continued.
[0013] Finally, the oxygen required for oxidation can also be
contained in the buffer gas of a shaft sealing. In this case, the
oxygen will flow in dosed quantities from the shaft sealing into a
pump chamber or into a conduit of the pump device.
[0014] The following is a detailed description of an embodiment of
the invention with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic longitudinal sectional view through
the compression chamber of a vacuum pump,
[0016] FIG. 2 is a sectional view taken along line II-II in FIG. 1,
and
[0017] FIG. 3 is a schematic representation for illustrating the
principle of the present invention.
DETAILED DESCRIPTION
[0018] According to FIG. 1, there is provided a vacuum pump in the
form of a screw pump. Said pump comprises an elongate housing 10
supporting therein two screw rotors 12,14 for rotation in opposite
senses. Each screw rotor comprises a helically configured tooth
16,18 with a pitch continuously decreasing from the pump entrance
20 to the pump exit 22, as can be seen in FIG. 1. Thereby, the
working chamber, which in rotating rotors will be traveling in
axial direction, is reduced in size from pump entrance 20 towards
pump exit 22. Between the pump entrance and the pump exit, the
compression chamber 24 is arranged.
[0019] Pump entrance 20 forms the pumping chamber which will be
connected to the device that is to be evacuated. Into this pumping
chamber, the process gas 38 will be sucked. The process gas
contains particles 40 in the form of non-oxidized dust.
[0020] Pump entrance 20 is connected to an oxygen intake 26 which
is laterally arranged on housing 10 and is provided with a throttle
valve 28. Throttle valve 28 can be set to various throttle cross
sections so as to regulate the oxygen supply. The oxygen can be
pure oxygen or a component of a gas mixture, e.g. of air.
[0021] Within pump housing 10, the dust will undergo a controlled
reaction with the supplied oxygen as soon as, during condensation,
an oxygen partial pressure as required for reaction has been
reached.
[0022] An alternative embodiment of the oxygen intake is designated
by 26a. Oxygen intake 26a is located in the region of the
mid-length of compression chamber 24, namely in the middle between
the two mutually engaging helically shaped teeth 16,18.
[0023] A third alternative includes the oxygen intake 26b arranged
on pump exit 22.
[0024] At each of said oxygen intakes 26,26a, due to the vacuum
prevailing there, the oxygen and respectively the ambient air will
be sucked in. The above oxygen intake 26b, however, is located at
the pump exit 22 where atmospheric pressure prevails. For this
reason, a connected oxygen source must be subjected to
overpressure. In any case, a throttle valve 28 is provided on the
oxygen intake.
[0025] FIG. 3 is a schematic representation of the pump with the
pump entrance 20 for suctional intake of the process gas 38. In
this Figure, oxygen intake 26 is arranged at the suction connector
of pump entrance 20.
[0026] In FIG. 3, the black sphere symbols represent the
non-oxidized particles, and the hollow sphere symbols represent the
oxidized particles. Oxidation takes place in compression chamber 24
in dependence on which intake among the oxygen intakes 26,26a,26b
is in the opened state.
[0027] In FIG. 3, the shafts for rotating the screw rotors are
designated by 30.
[0028] The invention has been described with reference to the
preferred embodiments. Modifications and alterations may occur to
others upon reading and understanding the preceding detailed
description. It is intended that the invention be construed as
including all such modifications and alterations insofar as they
come within the scope of the appended claims or the equivalents
thereof.
* * * * *