Combinations of CHCL and СHCL with propane and chladones 125, 227ea as prospective noncombustible refrigerants

В данной работе рассмотрена проблема пожарной опасности применяемых в настоящее время хладагентов, предложено решение - создание негорючих смесевых композиций органических хлоридов с пропаном и хладонами 125, 227еа. Показана возможность увеличения доли короткоживущих компонентов в негорючих смесевых хладагентах, содержащих парниковые газы, с помощью создания тройных смесей. According to existing international agreements production of greenhouse gases must be drastically reduced in all sectors including refrigeration. It is known that refrigerants having short atmospheric lifetime are combustible. One of the methods to solve the problem of combustibility of refrigerants is to create noncombustible mixtures of combustible substance with an inhibitor of combustion. Such mixtures of organic chlorides with propane and CFH or CFH are investigated in this paper both theoretically and experimentally. Experimental equipment was specially adjusted to the combustion properties of the used chlorinated substances. It was obtained that CHCl и CНCl are strong inhibitors of combustion processes including self-inhibition of combustion of these substances themselves. Fluorinated hydrocarbons CFH and CFH are effective in suppression of combustion of dichloromethane and 1, 2-dichloroethane in air. As it follows from the obtained results, it is possible to reduce the content of the greenhouse component in the mixed refrigerant by 93% mass by creating noncombustible mixtures of dichlorides with CFH or CFH which are greenhouse gases. It was also revealed that CFH and CFH are stronger suppressants for combustion of CHCl and CНCl than for combustion of propane. Creation of triple noncombustible mixtures between CH, CHCl and CFH is advisable only when it is necessary to optimize energy efficiency of the refrigerant.

On a composition of combustion products at a burning of methane-fluorinated hydrocarbon mixtures in air

Выполнена расчетная оценка равновесного состава продуктов горения околостехиометрических смесей вида метан - фторированный углеводород - воздух с использованием как программного комплекса Chemical Workbench, так и предложенной в настоящей работе упрощенной методики. Найдено, что основными продуктами горения являются CO, HO, CO, HF. При этом концентрации прочих продуктов горения имеют существенно более низкие значения. С помощью программного комплекса FDS выполнен расчет динамики концентраций опасных продуктов (СО, HF) в атмосфере модельного помещения объемом 12,6 м. Найдено, что для указанного помещения предельно допустимая концентрация CO достигается через 730 с после начала горения, а HF - практически мгновенно. Результаты работы могут быть полезны при применении фторированных углеводородов для пожаротушения и флегматизации горючих газовых смесей. Calculations of equilibrium compositions of combustion products at burning of near stoichiometric mixtures of methane-fluorinated hydrocarbon-air are presented. The program tool Chemical Workbench was used. Also a Simplified method was proposed. It was found that CO, HO, CO and HF are the main combustion products, and the concentration of other products are much more lower. The results of the calculations of the concentrations of the above mentioned products (CO, HO, CO and HF) by means of the simplified method are close to that obtained by the tool Chemical Workbench ones. The concentrations of CO and HF (the main hazardous products) as a function of time were determined for a typical room volume of 12, 6 m using the program tool FDS 6. It was found that a limiting allowable concentration of CO was reached after 730 s from the burning beginning, but at the case of HF this concentration was reached almost instantaneously. The results of this study can be used at an application of the fluorinated hydrocarbons for fire extinguishing and inertization of flammable gaseous mixtures.

Long-term Observations of Atmospheric Halogenated Organic Trace Gases

CFCs (chlorofluorocarbons) and other strong ozone-depleting halogenated organic trace gases were used in numerous industrial, household and agriculture applications. First atmospheric measurements of CFCs were performed in the 1970s, well ahead of the detection of the ozone hole in the 1980s. The continuous observation of these ozone-depleting substances (ODSs) is crucial for monitoring their global ban within the Montreal Protocol. In addition, also HFCs (fluorinated hydrocarbons) are measured, which were introduced as substitutes of ODSs and are potent greenhouse gases. Since 2000, Empa continuously measures more than 50 halogenated trace gases at the high-Alpine station of Jungfraujoch (3850 m asl) as part of the global AGAGE network (Advanced Global Atmospheric Gases Experiment). Jungfraujoch is the highest location worldwide where such measurements are performed, and the site where several of these compounds were measured in the atmosphere for the first time. The measurements at Jungfraujoch and at other globally well-positioned sites serve as an early warning system, i. e. before potentially harmful halogenated organic substances can accumulate and detrimentally affect the natural environment.

EXPERIMENTAL STUDIES OF THE TOXIC PROPERTIES OF HALOGEN-DERIVATIVES OF SATURATED HYDROCARBONS (CHLADONS)

A study was made on toxicity and hazards of 16 chladons which are representatives of various halogen derivatives of saturated hydrocarbons (fluorine derivatives of methane, ethane, propane, butane). It is shown that in terms of acute toxicity parameters, the studied chladons refer to low-toxic and low-risk substances (hazard class 4 according to GOST 12.1.007). The least toxic are fully fluorinated hydrocarbons: tetrafluoromethane, hexafluoroethane, octafluoropropane, decafluorobutane.` In the clinical picture of acute poisoning, signs of a narcotic effect prevail. Limit values Limac were determined for fluorocarbons in the range of 750-180 mg/l, for mixed fluorochlorinated hydrocarbons- up to 100 mg / l (45, 80 mg/l), for fluoriodohydrocarbns (pentafluoriodoethane) 10.5 mg/l. The main criteria tests were indicators of the state of the nervous and cardiovascular systems. Long-term exposure to the compounds studied (chladons Nos. 32, 125, 227, 218, 31-10) caused marked changes in the functional state of the nervous and cardiovascular systems, peripheral blood composition and metabolic processes. Hygiene standards for most tested chladons in the workplace air (MAC workplace) are approved at the level of 3000 mg/m3, hazard class 4;,vapors; in the atmospheric air of residential areas, the MAC. average daily of 10 (20) mg/m3 is set, and 100 mg/m3 for maximum single concentration (MAC.maximum single), reflective -resorptive effect, hazard class 4.

Deep Oxidation of Fluorinated Hydrocarbons in Molten Catalysts

<p>The oxidation of fluorine-containing organic substances: fluorocarbon liquid M-1, fluorinated alcohol H(CF₂)₈CH₂OH, and powder polytetrafluoroethylene with air has been studied in melts: NaOH; 43 mol.% LiCl - 33 mol.% NaCl - 24 mol.% KCl (eutectic mixture); (LiCl-NaCl-KCl)eutec. + 10 mass.% V₂O₅; (LiCl-NaCl-KCl) eutec. + 15 mass.% V₂O₅; 56 mol.% Na₂CO₃ - 44 mol.% K₂CO₃ (eutectic), (Na₂CO₃K₂CO₃)eutect. + 15 mass.% V₂O₅, and K₃V₅O₁₄. The compositions of the melts have been examined by GC, DTA, chemical analysis and XRD, and they have been shown to change during the reaction, depending on the composition and partial pressure of the gaseous products over the melt surface. The alkali metal chloride melt containing 15 mass.% V₂O₅ has been found to be most stable to the action of fluorine compounds. Possibility of deep oxidation of fluorine-containing organic substances in melts based on hydroxides, carbonates and chlorides of alkali metals doped with oxides of vanadium has been proved. The process of deep oxidation of fluorinated hydrocarbons is accompanied by formation of an equilibrium mixture containing hydroxides, carbonates, chlorides and fluorides of alkali metals, as well as their vanadates, if V₂O₅ additive is used. The relative amounts of these substances in molten systems are determined by the partial pressure of oxygen, CO₂and water vapor.</p>

Magnesium Melt Protection

Mg especially in the molten state is well known for its high affinity to O2. When O2 content of the atmosphere is larger than 4%, molten Mg will burn! To avoid this, melt protection is necessary. At present mostly SF6 is used during primary production and processing of Mg and its alloys. Unfortunately SF6 is a very potent greenhouse gas that is > 23,000 times more effective than CO2. This also affects life cycle considerations e.g. for the use of Mg alloys in transportation. However, other protective gases like SO2 or fluorinated hydrocarbons like HFC134a, Novec 612, or AMCover (=HFC134a) have been suggested to replace SF6. Additionally fluxes mixed from different salts may be used again as well to protect molten Mg. But fluxes and feasible replacements of SF6 have also disadvantages. Moreover SF6 and other fluorinated hydrocarbons are under discussion especially in Europe. There is an existing EU legislation that will ban SF6 from 2018 and there are similar discussions regarding all other fluorinated hydrocarbons. Due to this, new innovative ways have to be found or old methods have to be renewed to allow Mg industries further safe processing of molten magnesium. This contribution will report the state of the art in protecting molten Mg and alternatives to the use of SF6.