What is claimed is:
1. A chemical decontamination method of chemically decontaminating radioactive nuclides from a metallic material surface contaminated by the radioactive nuclides, the method comprising the steps of:
reductively decontaminating using a reductive decontaminating agent containing at least two kinds of components; and then
decomposing said reductive decontaminating agent using a decomposing apparatus for decomposing at least two kinds of chemical substances in said reductive decontaminating agent.
2. A chemical decontamination method according to claim 1, wherein in said step of decomposing said reductive decontaminating agent using the decomposing apparatus, said at least two kinds of chemical substances in said reductive decontaminating agent are decomposed at a time.
3. A chemical decontamination method according to claim 1, wherein when said apparatus for decomposing at least two kinds of chemical substances in said reductive decontaminating agent cleanses radioactive nuclides from the decontaminating agent using a cation resin column during decontaminating, a composition trapped by said cation resin column at an inlet side of a cleaning apparatus is selectively decomposed.
4. A chemical decontamination method according to claim 3, wherein in a decomposing apparatus for the reductive decontaminating agent, a composition trapped by said cation resin column at the inlet side of the cleaning apparatus is selectively decomposed when the radioactive nuclides in the decontaminating agent are cleansed using the cation resin column during decontaminating, and said at least two kinds of compositions are decomposed at a time by controlling an adding amount of hydrogen peroxide after completion of the decontaminating step.
5. A chemical decontamination method according to anyone of claim 1 to claim 4, wherein compositions of said reductive decontaminating agent include oxalic acid and hydrazine.
6. A chemical decontamination method of chemically decontaminating radioactive nuclides from a metallic material surface contaminated by the radioactive nuclides, the method comprising the steps of:
reductively decontaminating using a reductive decontaminating agent; and then
decomposing said reductive decontaminating agent using a decomposing apparatus for decomposing at least oxalic acid and hydrazine in said reductive decontaminating agent.
7. A chemical decontamination method according to any one of claim 1 to claim 6, wherein said reductive decontaminating agent contains oxalic acid and hydrazine, and is a reductive acid solution of which a concentration of oxalic acid is 0.05 to 0.3 wt % and a pH is 2 to 3.
8. A chemical decontamination method according to any one of claim 1 to claim 6, which further comprises an oxidative dissolving process for oxidatively dissolving chromium in a metal oxide on the metallic material surface contaminated by the radioactive nuclides into hexadic chromium using permanganate before or after the reductive dissolving process for dissolving and removing the metal oxide.
9. A chemical decontamination method according to claim 8, wherein said reductive dissolving process and said oxidative dissolving process are alternatively performed, and said reductive dissolving process is performed at least twice.
10. A chemical decontamination method according to any one of claim 1 to claim 9, wherein a catalyst decomposition column is used as the decomposing apparatus for the reductive decontaminating agent.
11. A chemical decontamination method according to claim 10, wherein at least one element selected from the group consisting of platinum, ruthenium, vanadium, palladium, iridium and rhodium is used as a catalyst filled in said catalyst column, and an oxidizing agent is supplied in an inlet side of said catalyst column.
12. A chemical decontamination method according to any one of claim 1 to claim 11, wherein a quantity of hydrogen peroxide added is less than an equivalent weight of the components trapped in the cation resin column when components trapped in the cation resin column is selectively decomposed, and a quantity of hydrogen peroxide added is more than an equivalent weight react with the components trapped in the cation resin column when components trapped in the cation resin column and components trapped in the anion resin column are decomposed at a time.
13. A chemical decontaminating system, which comprises a catalyst decomposition column in an upstream side of an ion exchange resin column and a hydrogen peroxide injection apparatus in a further upstream side in order to reduce an amount of waste products caused by a chemical decontaminating agent in a case where a mixed decontaminating agent for a composition trapped in a cation resin column and for a composition trapped in an anion exchange resin is used for the chemical decontaminating agent, and in order to selectively decompose the composition trapped in a cation resin column in an inlet side of a cleaning apparatus when radioactive nuclides in the decontaminating agent are cleansed using the cation resin column during decontaminating and decompose the both compositions after completion of decontaminating process.
14. A chemical decontaminating system according to claim 13, which further comprises a gas-liquid separating apparatus for separating decomposed gas in an upstream side of the catalyst decomposition column and in a downstream side of the ion exchange resin.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A process for preparing butadiene from n-butane comprising the steps of
(A) providing an n-butane-containing feed gas stream,
(B) feeding the n-butane-containing feed gas stream into a first dehydrogenation zone and nonoxidatively catalytically dehydrogenating n-butane to 1-butene, 2-butene and optionally butadiene to obtain a first product gas stream comprising n-butane, 1-butene and 2-butene, with or without butadiene and secondary components,
(C) feeding the first product gas stream comprising n-butane, 1-butene and 2-butene, with or without butadiene and secondary components, into a second dehydrogenation zone and oxidatively dehydrogenating 1-butene and 2-butene to butadiene to give a second product gas stream comprising butadiene, n-butane and steam, with or without secondary components,
(D) recovering butadiene from the second product gas stream.
2. The process as claimed in claim 1, wherein the provision of the n-butane-containing feed gas stream comprises the steps of
(A1) providing a liquefied petroleum gas (LPG) stream,
(A2) removing propane and optionally methane, ethane and pentanes from the LPG stream to obtain a butane-containing stream,
(A3) removing isobutane from the butane-containing stream to obtain the n-butane-containing feed gas stream and optionally isomerizing the removed isobutane to an n-butaneisobutane mixture and recycling the n-butaneisobutane mixture into the isobutane removal.
3. The process as claimed in claim 1 or 2, wherein the nonoxidative catalytic dehydrogenation (B) of n-butane is carried out as an autothermal catalytic dehydrogenation.
4. The process as claimed in any of claims 1 to 3, wherein the oxidative dehydrogenation (C) is carried out in more than one stage.
5. The process as claimed in any of claims 1 to 4, wherein the recovery (D) of butadiene from the second product gas stream comprises the steps:
(D1) cooling the product gas stream with water to condense out steam and any high-boiling organic secondary components;
(D2) removing the low-boiling secondary components contained in the second product gas stream which are selected from the group consisting of hydrogen, carbon monoxide, carbon dioxide, nitrogen, methane, ethane, ethene, propane and propene, to obtain a stream comprising butadiene and n-butane, with or without 1-butene and 2-butene, and with or without oxygenates as further secondary components;
(D3) optionally removing the oxygenates to obtain a stream comprising butadiene and n-butane, with or without 1-butene and 2-butene;
(D4) separating the stream comprising butadiene and n-butane, with or without 1-butene and 2-butene, into a stream comprising n-butane, with or without 1-butene and 2-butene, and a stream comprising butadiene;
(D5) optionally recycling the stream comprising n-butane, with or without 1-butene and 2-butene, into the nonoxidative catalytic dehydrogenation (B).