EFFICIENT CONTROL OF FUNCTIONING OF ELECTRICAL GAS PREPARATION COMPLEX TO TRANSPORTATION BY MAIN PIPELINE

The article discusses the problem of increasing the effi ciency of the linear section of the main gas pipeline system by developing eff ective control algorithms for the operating modes of the gas cooling unit. To develop control algorithms for a gas cooling unit, adapted mathematical models of thermal processes in air-cooled gas devices and in a gas pipeline are used. It is shown that when considering the dynamic modes, the gas pipeline system can be represented as consisting of two dynamic links. The link “gas cooling unit”, which includes up to 24 electric drives with heat exchangers, is characterized by relatively short time constants. In the main gas pipeline, heat exchange processes proceed much more slowly. This circumstance allows the main att ention to be focused on the development of an eff ective control system for the cooling plant. The control is carried out by discrete or continuous change in the fl ow rate of the cooling air through the heat exchanger by adjusting the number of switched on air coolers and changing the fan speed. The search for control algorithms for air coolers is carried out by formulating and solving the problem of minimizing the root-mean-square deviation of the gas temperature at the outlet from the heat exchanger from the required value. To implement the obtained control algorithms, a functional diagram of the automatic control system for the operating modes of the gas cooling unit has been developed.

sub-Hz Differential Rotational Spectroscopy of Enantiomers

Observation of parity-violating effects in chiral molecules is a long-standing challenge of the molecular spectroscopy community. In the microwave regime, the difference in transition frequencies between enantiomers is predicted to be below the mHz level, which is considerably beyond current experimental capabilities. The most promising future efforts combine vibrational spectroscopy, buffer gas cooling, and carefully chosen molecular candidates with large predicted parity-violating shifts. Here, we demonstrate for the first time high-precision differential microwave spectroscopy, achieving sub-Hz precision by coupling a cryogenic buffer gas cell with a tunable microwave Fabry-Perot cavity. We report statistically limited sub-Hz precision of (0.08±0.72) Hz, observed between enantiopure samples of (R)-1,2-propanediol and (S)-1,2-propanediol at frequencies near 15 GHz. We confirm highly repeatable spectroscopic measurements compared to traditional pulsed-jet methods, opening up new capabilities in probing subtle molecular structural effects at the 10−10 level and providing a platform for exploring sources of systematic error in parity-violation searches. We discuss dominant systematic effects at this level and propose possible extensions of the technique for higher precision.

Cooling-induced Vortex Decay in Keplerian Disks

Vortices are readily produced by hydrodynamical instabilities, such as the Rossby wave instability, in protoplanetary disks. However, large-scale asymmetries indicative of dust-trapping vortices are uncommon in submillimeter continuum observations. One possible explanation is that vortices have short lifetimes. In this paper, we explore how radiative cooling can lead to vortex decay. Elliptical vortices in Keplerian disks go through adiabatic heating and cooling cycles. Radiative cooling modifies these cycles and generates baroclinicity that changes the potential vorticity of the vortex. We show that the net effect is typically a spin down, or decay, of the vortex for a subadiabatic radial stratification. We perform a series of two-dimensional shearing box simulations, varying the gas cooling (or relaxation) time, t cool, and initial vortex strength. We measure the vortex decay half-life, t half, and find that it can be roughly predicted by the timescale ratio t cool/t turn, where t turn is the vortex turnaround time. Decay is slow in both the isothermal (t cool ≪ t turn) and adiabatic (t cool ≫ t turn) limits; it is fastest when t cool ∼ 0.1 t turn, where t half is as short as ∼300 orbits. At tens of astronomical units where disk rings are typically found, t turn is likely much longer than t cool, potentially placing vortices in the fast decay regime.

Development of a model of the optimal temperature mode of the main gas pipeline operation

The influence of the ambient air temperature on changes in the parameters and thermophysical characteristics of the gas pumped through the underground pipeline was investigated. This was done because there are no scientifically sound recommendations for the optimal gas temperature after coolers at the compressor station. The presence of the site of inversion of heat exchange between gas and soil – a change in the direction of heat exchange along the length of the gas pipeline was revealed. It was proved that the air temperature above the soil surface should be substituted into the formula for calculating the change in gas temperature along the length of the pipeline between compressor stations. This made it possible to determine quantitative changes in the thermophysical and hydraulic characteristics of the gas along the pipe length, in particular, the change in density, viscosity, heat capacity, flow regime. It is shown that the change in air temperature during the year leads to a change in the gas pressure at the end of the gas pipeline section up to 0.15 MPa. A change in air temperature by 10 °С leads to a change in gas temperature by approximately 5 °С. Analytical studies made it possible to develop practical recommendations for the power-saving operation of air coolers at compressor stations. It was determined that the optimum gas temperature at the cooler outlet will be the temperature at which the heat exchange inversion point along the length of the gas pipeline coincides with the location of the subsequent station. It is shown how to control gas cooling in air coolers. In particular, by shutting down one of several operating devices and changing the speed of the fan drive. The developed recommendations will make it possible to quickly regulate the temperature mode of the underground gas pipeline operation at optimal power consumption for the operation of the gas cooling system after gas compression

Modern Solutions for the Reconstruction of Gas Exhaust Ducts of Converters Operating in Ukraine

Nowadays most of the installed gas cleaning equipment of oxygen converters of metallurgical plants performs cleaning out of emissions of solid particles with final concentrations higher than acceptable. The inconsistency of the efficiency of the BOF-gas purification with the new emission standards entails the rejection of the emission permit and as a consequences the shutdown of metallurgical plants as well as the loss of the sales markets. In order to prevent the shutdown of the main shops of the metallurgical plants with the simultaneous implementation of appropriate environmental protection measures, it is important to launch the reconstruction of all gas-cleaning units of the converter exhaust ducts. The first element of the BOF-gas cooling and purification system is the BOF-gas cooler, its equipment is in close connection with the process equipment, thus the technological mode of steel production fully depends on its operating mode. The article describes the options of modernization of the exhaust duct of HRSG installed in the BOF-gas cleaning system. Besides, two options of BOF-gas cleaning system presented. In addition, two options of HRSG design: the old one and modernized – were compared.

Combined control of fans of gas cooling units electric drives

The problem of the temperature control at the outlet of gas cooling units of compressor stations of main gas pipelines is discussed. To solve the problemt, a discrete or frequency control of electric motors of fans of gas air cooling devices is used. The problems of electromagnetic compatibility that arise in typical power supply systems of gas cooling installations when connecting electric motors of fans through frequency converters are noted. A combined fan motor control system is considered, in which the electric motors are divided into two groups. The electric motors of the first group are connected to the network directly, the second through frequency converters. By reducing the number of electric motors connected to the network through frequency converters, the negative impact of frequency-controlled drives on the quality of electricity is reduced and the costs of modernization projects are reduced in comparison with the option of the variant using a frequency converter for each electric motor. The energy characteristics of the combined control system are analyzed. The relations that establish the relationship between the temperature difference at the cooling unit and the power of the fan motors for various control methods are obtained. The optimal control algorithm according to the criterion of maximum power saving is proposed, which provides for the interconnected control of the number of discrete-controlled motors and the speed of frequency-controlled drives. The variants of the implementation of the optimal control algorithm are discussed. Analytical expressions for power saving on the fan motor shaft in a combined system compared with a discrete one and a method for estimating energy savings are considered. The obtained results are recommended to be used to assess the technical and economic efficiency of projects for the modernization of electrical complexes of gas cooling units.

THE VERIFICATION OF THE RSG-GAS REACTOR COOLING TOWER HEAT TRANSFER CAPACITY

The RSG-GAS reactor has been replaced and the technical specifications for the new cooling tower specify that the heat transfer capacity from the secondary cooling water to the environment is 5500 kW per module. Therefore, this study aims to verify the theoretical calculations of the heat transfer capacity using performance test data collected on the 30 MW power operation on December 20, 2018, such as the temperature of the primary and secondary coolant entering and exiting the cooling tower, wet bulb, and environmental dry bulb temperature, as well as the inlet and outlet air temperature. Furthermore, the data were used to calculate the heat transfer capacity from the secondary cooling water to the environment. The results showed that each cell of the RSG-GAS cooling tower reactor transfers the heat of approximately 5528.52 kW. This value is consistent with the technical specifications written in the revised RSG-GAS Safety Analysis Report 11.