Gas separation: processes – With control responsive to sensed condition
Reexamination Certificate
1999-04-27
2001-07-10
Simmons, David A. (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
C095S273000, C095S287000, C095S288000, C055S315000, C055S315100, C055S338000, C055S338100, C055S467000, C055S467100
Reexamination Certificate
active
06258151
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method and an apparatus for the purification and reuse of waste air mixed with additives (for example, solvents) or impurities, and, in particular, to a method and an apparatus for the purification and reuse of waste air mixed with solvents from dryer appliances of web-fed offset printing machines.
For the purification of waste air, it is known, as the state of the art, to carry out thermal post-combustion of the waste air and thereby eliminate, by combustion at temperatures of 700-800° C., the additives and impurities contained in it. Post-combustion of this kind is energy consuming and produces undesirable additional substances (for example, CO
2
, carbons).
The object on which the invention is based is to offer a method and an apparatus for the purification of waste air by the removal of additives or of impurities, in which energy-consuming post-combustion is dispensed with.
SUMMARY OF THE INVENTION
A first method variant according to the invention provides for leading the waste air through at least one condenser, in order to condense out additives and impurities contained in the waste air, and to lead the waste air through at least one separator element for the further purification of the waste air.
By virtue of the combination of the method steps of condensing out and separation, substantial or complete purification of the waste air, depending on the additives or impurities contained in it, is carried out, so that there is no longer any need for thermal post-combustion. If any extremely small fraction of additives (for example, solvents) or impurities still remains, it becomes possible, in a further method step of the method according to the invention, to recirculate the purified waste air and to reuse it for the renewed absorption or suction-removal of additives or impurities and, consequently, makes a renewed execution of the method possible.
Since there is no discharge of purified air into the surroundings, thermal post-combustion, which would result in basically complete purity of the waste air, irrespective of the additives and impurities, may be dispensed with. Any remaining slight residual constituents of additives and impurities are not discharged into the environment, but can be used once again for the execution of the method according co the invention.
The first method variant according to the invention makes it possible, by the combination of the method steps of condensing out and separation and by the recirculation of the waste air, purified in this way, within a closed circuit, to dispense with the energy-consuming thermal post-combustion which is necessary when ar open circuit, with the purified waste air being discharged into the environment, is used.
By virtue of the constant circulation of the repeatedly purified waste air, to which meterable quantities of fresh air may be added, it becomes possible to employ a condensing-out and separation purification technology which is more energy-effective and therefore more cost-effective than thermal post-combustion. At the same time, the requirements as to the purity and degree of purification of the waste air, which are required for the continuous and repeated execution of the method, and the requirements that the method according to the invention be environmentally friendly, are satisfied.
Before being introduced into the condenser, the laden waste air is advantageously guided through a fresh-air heat exchanger, so as to pass through a first cooling stage, in order, thereupon, to cause the additives and impurities to be condensed out in the following condenser.
Connecting in series two condensers, through which the waste air is led, brings about particularly thorough and complete condensing out. Such a series connection of two separator elements likewise increases the degree of purity of the waste air led through, after it has passed through the separator elements.
Concentration of the additives or impurities precipitated and separated in the condenser and separator element is advantageously carried out in a collector, so that condensed solvents converging there can be supplied again for their original purpose and serve for ink production.
In order further to increase the purifying capacity of the first method variant according to the invention, it is recommended to use, downstream of the condenser and separator element, a further filter element, through which the waste air is led.
Before the purified waste air is recirculated for the renewed absorption and suction-removal of additives and impurities, the already completely purified waste air is led through a conditioning apparatus, by means of which quantity metering, the admixture of fresh-air quantities required and the influencing of further air parameters (for example, temperature, humidity) can be carried out.
An advantageous multiple utilization of the first method variant according to the invention is achieved by driving a turbine by means of the waste air led through, the result of this being that current for driving individual assemblies of the purification system is generated in a generator connected to the turbine.
Furthermore, along the lines of combined power, heat and cold generation, the prevailing waste air and the waste air to be purified may be used for operating a cold generator and a heat generator, the thermal power of which may be used in each case, at the necessary location, for air cooling and air heating respectively.
The above-described possibilities for the multiple utilization of the waste air to be purified allow the cost-saving operation of the method as a whole, since at least a fraction of the electrical and thermal energy required for carrying out the method can be generated and made available, without having to resort to external energy sources.
The first apparatus variant according to the invention is distinguished by a completely closed pipe system, during the passage through which the waste air to be purified, after being led through a condenser, with subsequent condensing our, and after being led through a separator element, with further purification, is once again fed to the location where the waste air is extracted, and the purified waste air can be used for the reabsorption of additives and impurities By virtue of the closed circuit, no waste air at all is discharged into the environment, so that no account has to be taken of the relevant stringent purity requirements, which, according to the state of the art, have been achieved by thermal post-combustion in conjunction with an open circuit, and any remaining relatively small fractions of additives and impurities nevertheless allow the substantially purified waste air to be reused.
A second method variant according to the invention relates, in particular, to ink pastes which are used in web-fed offset printing and of which approximately 70% consists of pigments and approximately 30% of high-boiling mineral oils. Hitherto, after the drying operation in the dryer, these mineral oils have been released, suction-removed by the waste air and burnt with the aid of supporting gas at high temperatures of approximately 750° C., in order thereby to adhere to the prescribed content of residual carbons. Furthermore, benzenes released in the region of the printing units of the printing machines as a result of washings of the rubber blankets were also absorbed and discharged by means of the waste air.
The further method variant according to the invention, then, makes it possible to purify the waste air without thermal post-combustion. The waste air therefore no longer has to be heated to 750° C. and burnt with the aid of supporting gas, but has to be heated merely to a temperature of about 160° C.
By the use of indirectly heated dryers (that is to say, without an open flame), no oxygen is extracted from the purification air, so that pure circulating-air operation can be implemented, without the supply of fresh air, and, even in the machine enclosures used as a work area and in the surroundings of the printing machines, there is a
Harle Rainer
Thielen Gunter
Hopkins Robert A.
Maul & Co. - CHR Belser GmbH
Merchant & Gould P.C.
Simmons David A.
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