CALCULATION AND DESIGN OF AN INDUSTRIAL REACTOR FOR PYRROLES SYNTHESIS

Industry of pyrroles synthesis on the basis of acetylene, ammonia and amines over polyfunctional catalyst can be organised only when for its recovery the rational industrial technology allowing to synthesize this product in necessary quantity and demanded quality cheap enough from accessible raw materials is developed. Considering the issues related to the development of a new reactor with high productivity and economic efficiency, the processes running in the reactor were studied. Phase characteristics have been investigated in response to changes in acetylene conversion rate due to the height of the catalyst layer. As a result, high productivity of acetylene production with zinc-chromaluminum catalyst at the temperature range of 340-440оС is achieved for 92% when the layer height is 1200 mm from the reactor top point. Based on the mass balance as well as the experimental result, a reactor for the industrial synthesis of pyrroles has been proposed.

Impact of PAH photodissociation on the formation of small hydrocarbons in the Orion Bar and the horsehead PDRs

ABSTRACT We study whether polycyclic aromatic hydrocarbons (PAHs) can be a weighty source of small hydrocarbons in photodissociation regions (PDRs). We modelled the evolution of 20 specific PAH molecules in terms of dehydrogenation and destruction of the carbon skeleton under the physical conditions of two well-studied PDRs, the Orion Bar, and the Horsehead nebula that represent prototypical examples of PDRs irradiated by ‘high’ and ‘low’ ultraviolet radiation field. PAHs are described as microcanonical systems. The acetylene molecule is considered as the main carbonaceous fragment of the PAH dissociation, as it follows from laboratory experiments and theory. We estimated the rates of acetylene production in gas phase chemical reactions and compared them with the rates of the acetylene production through the PAH dissociation. It is found that the latter rates can be higher than the former rates in the Orion Bar at AV < 1 and also at AV > 3.5. In the Horsehead nebula, the chemical reactions provide more acetylene than the PAH dissociation. The produced acetylene participate in the reactions of the formation of small hydrocarbons (C2H, C3H, C3H+, C3H2, C4H). Acetylene production via the PAH destruction may increase the abundances of small hydrocarbons produced in gas phase chemical reactions in the Orion Bar only at AV > 3.5. In the Horsehead nebula, the contribution of PAHs to the abundances of the small hydrocarbons is negligible. We conclude that the PAHs are not a major source of small hydrocarbons in both PDRs except some locations in the Orion Bar.

Hierarchical system of fuzzy regulation of acetylene production process by oxidative pyrolysis of natural gas

The paper describes a complex chemical-technological system of producing acetylene by oxidative pyrolysis of natural gas, for which ensuring technological safety is a prerequisite for its functioning. There have been discussed the ways of developing a control system for this process while ensuring its technological safety based on the definition of its area and security center. A two-level control option is proposed, in which the upper level performs dynamic correction of the tasks of the regulators of the local contours of the lower level, taking into account the safety requirements. The approach using the fuzzy logic apparatus to implement the work of the upper level of the control system in order to increase the technological safety of the process is proposed. The algorithm of the upper level of the control system is presented taking into account the frequency of obtaining information about the state of the process. To prevent an emergency in the intervals between obtaining information about the state of the process, it is proposed to use a mathematical model of the process with periodic adjustment of the input data used for calculations. The proposed version of the control system can reduce the number of emergency stops of the process, which will lead to saving resources and reducing environmental pollution.

Gypsum Expanded Clay Concrete for External Walls

The technology of multicomponent water-proof gypsum binder and gypsum expanded clay concrete with water resistance increased by 1.8–2.2 times comparing to the initial gypsum, and with a softening coefficient of 0.85–0.91, is developed and patented. The binder contains a complex mineral additive including a waste product, carbide silt, and biosilica. The use of the carbide silt (waste product from the acetylene production) together with the biosilica as the WPB components provides for both the engineering-and-economic efficiency and the ecological one. The energy consumption of the WPB production is considerably lower than that of other widely used binding agents based on the Portland cement due to the reduction of the electric power consumption by 2.5 to 3 times and that of the fuel by 3 to 3.5 times. Gypsum expanded clay concrete prepared on the basis of this binder has water resistance, freeze-thaw resistance and creep measure allowing to use it as a wall material for manufacturing wall blocks or for erecting monolithic buildings.

Simulation of calcium acetylide and acetylene production

Design simulation of a reactor for acetylene production from calcium acetylide and its purification in the gaseous phase is presented. Simulations were performed using the program ASPEN+ which is a very flexible and useful tool for the simulation and optimization of various types of chemical technologies including gas-liquid-solid systems. The first step of the acetylene synthesis, based on coal as the raw material, is the production of calcium acetylide. This substance is obtained from coke and limestone in an electric arc furnace at elevated temperatures. Raw materials used in this process contain relatively large amounts of impurities that are converted and entrapped in the desired product of the above reaction. Some of the impurities, e.g. metallic iron or its alloys, can be separated easily. However, most of the other elements present in the form of their compounds with calcium remain a part of “technical grade” calcium acetylide. Acetylene is commercially produced by the reaction of “technical grade” calcium acetylide with water under controlled reaction conditions in an inert atmosphere. Depending on the purity of calcium acetylide used, the produced raw acetylene contains a variety of admixtures that lower its quality. As a consequence, prior to its expedition to the customer, raw acetylene should be submitted to a down-stream processing that consists of the separation of basic and acidic pollutants present in acetylene by absorption. The final processing step is adsorption and/or freezing-out of water vapor from the purified acetylene stream. Besides acetylene, the reaction of calcium acetylide with an excess of water provides aqueous calcium hydroxide. In order to commercialize this byproduct, the content of water in the mixture should be lowered to the required level. In this contribution, development of a model of calcium acetylide and acetylene production as well as the simulation of these processes in ASPEN+ are presented. Simulation results of a realistic production line model correlate very well with the actual data from the technology used in Fortischem, a.s., Novaky, Slovakia.