Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including heat exchanger for reaction chamber or reactants...
Reexamination Certificate
1999-10-22
2002-12-17
Bos, Steven (Department: 1754)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including heat exchanger for reaction chamber or reactants...
C422S203000, C422S200000
Reexamination Certificate
active
06495110
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method and an apparatus for processing matter by hydrothermal reactions, such as rupturing of molecular chains, recombination and decoupling occluded molecules, oxidation and reduction reactions, by holding the matter with water held at temperature above 200° C.
BACKGROUND ART
In recent years, it has been pointed out that ashes generated from incineration of municipal waste contain substances harmful to humans such as dioxin and others, resulting in demands for treatment processing to deal with such matters. Also, needs are increasing for processing halogen compounds, herbicides, PCB, DDT and other organic halogen compounds contained in pesticides, chemical weapons such as poison gas, explosives, substances with high organic contents unamenable to biological processing, waste water containing matters unamenable to biological processing, compounds that suppresses biological metabolic reactions, and other substances that cannot be discharged or left in the environment.
As a method of treating such substances, expectations are high for hydrothermal reactions that hold the substances with water at temperature above 200° C. and perform tasks such as severing of molecular chains, recombination and decoupling occluded molecules, oxidation and reduction reactions. This high expectation is because this type of chemical processing can be carried out in a closed-circuit system and the facility can be relatively small.
Especially, in the so-called super-critical zones, it is known that a medium exists in an unusual middle state that is neither gas nor liquid, and exhibits special physical and chemical properties that can be used to perform various treatments. Here, the super-critical state, when the medium is water, means that the temperature exceeds the critical temperature of 374.15° C. and the pressure exceeds the critical pressure of 225.56 atmosphere, and a state near this critical point, such as temperature between 200 and 374.15° C. at a pressure exceeding the saturated vapor pressure, is called a sub-critical state. Here, in order to create such state, it is necessary to maintain the pressure of the medium to higher than its vapor pressure to avoid the temperature decrease as a result of heat loss caused by latent heat of vaporization. As an example, a relation between temperature and vapor pressure for water is shown in FIG.
9
.
Such hydrothermal reactions are useful not only to decontaminate the substances, but are also useful as a technology for converting organic waste matter to carbon slurry, which can be used as a carbon source for fuel or chemical reactions. The process includes steps of: converting organic matter to water slurry; thermal treatment at a high temperature and high pressure condition; washing and dewatering and increasing the calorific value by separating and concentrating dechlorinated solid carbon and oil.
Typical methods and apparatuses for performing super-critical processing are known wherein such steps are conducted as: charging a waste matter to be processed into a vertical pressure chamber; and creating the super-critical zone in the upper half of the chamber and creating a sub-critical zone in the bottom half of the chamber. In such apparatus, chemical reactions such as oxidation reactions are carried out in the super-critical zone, while solid particles that are present in the waste matter or in the reaction products are separated and absorbed in the slurry at the sub-critical zone. A outlet is provided at the top of the chamber to remove the fluid reaction products of the super-critical state region. This discharge fluid is sent to the next processing station through piping provided with a filter, where solid particles included in the reaction products are removed.
In such apparatus, the pressured matter is charged into the super-critical zone provided at upper region of the chamber through a supply pipe. Oxidation of organic substances such as dioxin are carried out in the super-critical zone, and the fluid layer at the super-critical temperature first flows downward and then flows upward. Therefore, combusted liquid waste is discharged through the pipe at the top of the chamber, but the inorganic substances contained in the charged matter, which do not dissolve in the super-critical zone, are precipitated. These precipitates continue to flow downward, due to momentum and gravity forces, and reach the liquid phase in the sub-critical zone. The liquid phase in the sub-critical zone dissolves organic substances that do not dissolve in the super-critical zone, and forms a slurry which does not dissolve in the super-critical zone. The slurry thus obtained is discharged through a pipe provided at the bottom of the chamber which is in the sub-critical zone.
However, in such conventional technology, because the inside wall of the reaction chamber is exposed to the super-critical temperature and strong oxidation ambient, even expensive material such as Inconel are attacked by corrosion. Also, because of this concern for corrosion, it was not possible to raise the reaction temperature too much. Furthermore, the use of such expensive materials, in a thickness range of several centimeters which is necessary to withstand the high pressure above 225.56 atmosphere, results in a very costly apparatus.
In the case of decomposition of substances like dioxin, that are highly toxic at very small amounts, it was very common to use a second reactor in addition to the main reactor. This is because the super-critical oxidation reaction alone cannot raise the temperature high enough to obtain appropriate reaction rates, resulting in insufficient residence time in the chamber for the reacting substances. Also, if the waste matter contains porous matter, only the surface is reacted but the interior matter may be left unprocessed, so that there is danger of retaining toxic substances in the residues.
Also, because the pressure chamber almost behaves as a complete mixing reactor, there is a possibility of some of the substances to be processed flowing out of the chamber without having been processed. One of the possible methods to prevent this is to increase the flow rate by re-circulating the fluid inside the chamber so that increased inflow can stir and mix the contents of the chamber. Another method is to provide a secondary processing chamber for processing the unreacted substances.
Salts are not dissolved in the super-critical zone and are precipitated, whereas they are dissolved and diluted in the sub-critical zone to be discharged. However, a diffusive boundary region between the super-critical and sub-critical zone is exposed to a severe condition where alternating drying and wetting actions take place, and may grow scales consisting of salts and other retained solid particles in its vicinity. For this reason, the location of the boundary region is periodically moved by adjusting the process, and the grown scales must be removed by stopping the process. Some of the scales are difficult to remove, and may even necessitate disassembling the chamber, especially when the chamber is used for processing municipal waste incineration ashes, which may contain calcium, potassium, sodium, chlorine, and sulfur, very often in concentration as high as 10-20%. As a result, it is expected that the chamber cannot be operated over a prolonged period.
Furthermore, when removing the fluid directly from the super-critical zone of the chamber, precipitated micro-particles of salts and solid particles originally contained in the waste matter may sometimes be carried out together. Therefore, it is necessary to remove the particles at the reaction products in the super-critical state with a filter to prevent corrosion of the delivery pipe. However, because the process temperature exceeds 374.15° C., the filter must be made of expensive materials such as ceramics, and often faces clogging problems.
Furthermore, relatively non-fluid substances such as salts and occluded solid particles tend to settle in the bottom of the chamber. To remove such sett
Higo Tsutomu
Serikawa Massahiro Roberto
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