Negative sides of process-flow diagrams for utilization of acidic decomposition gases from vacuum towers of production atmospheric-vacuum tubestill units in the radiation chambers of active furnaces at oil refineries (OR) are examined. New flow diagrams for utilization of decomposition gases from vacuum towers are proposed: adsorption of hydrogen sulfide by amine solutions; and combustion in a firebox using a special lining. It is pointed out that utilization of decomposition from vacuum towers in a firebox with subsequent recuperation of the heat of exiting exhaust gases and warming of a thermal agent is an economically effective technical solution recommended for implementation at OR.Utilization of acidic decomposition gases from vacuum towers in the radiation chambers of active furnaces in atmospheric tubestill units is practiced at many domestic oil refineries (OR). Let us examine the entire spectrum of negative consequences of adoption of such a technical solution, and possible alternate schemes for resolution of this problem.Decomposition gases are characterized by a high content of hydrogen sulfide H 2 S (10-45%, depending on the physicochemical composition of the feedstock and operating temperature regime of the furnace), and low excess pressure (p = 0.015-0.030 MPa) and temperature T = 25-50°C.Adsorption of hydrogen sulfide by diesel-fuel cuts in a mixing condenser with and without additives of surfaceactive substances (SAS) is carried out, for example, to lower the H 2 S content in decomposition gases at OR. The hydrogen sulfide-enriched diesel cuts are then pumped either into an electric desalting unit (to lower the viscosity of the crude), or into the feedstock of the hydrotreating unit; this is more optimal, since there is no mixing condenser in the flow diagrams of vacuum-creating equipment at many plants.As a rule, the circuit for utilization of acidic gases is as follows: separator -plain-or alloy-steel piping -fire barrier -separate inlet to radiation furnace, or inlet through fuel-oil line of combined burner. The degree of H 2 S conversion for this circuit does not exceed 60-70%, and the hydrogen sulfide is converted to SO 2 (SO 3 ) in the burning process. During oxidation of the H 2 S, a small amount of SO 2 (normally from 1 to 5%) is oxidized to SO 3 . The degree of conversion will depend on such factors as the temperature profile throughout the volume of the flue gases, the amount of sulfur dioxide in the flue gases, and the effect of aluminum as a component part of the refractory, etc.The SO 3 that has formed at temperatures ranging from 230 to 340°C enters into reaction with the water contained in the flue gases, forming sulfuric acid, which results in a number of serious problems: sulfuric acid contributes to a shift in the dew point to as high as 200°C, and condensation of the sulfuric acid may result in rapid surface corrosion of the metalwork of the furnace, the tubes of the soils in the convection chamber, and the recuperators extracting the heat of the exiting flue gases [1].The low d...
and that in the section 0.35 the electrodynamic forces are opposed to the electromagnetic forces, while in the section 0.75 they cooperate; then the useful work done by the electrodynamic forces will be Aed=/~d(0.7--0,3)5 = 0,4 6Fed = 0.4.3.290 = 3.48 l, which is 14% of the total energy of the REM in comparison with the case when Fed --0 over the whole stroke 6.In conclusion, we must remark that on the basis of our investigations we have elucidated the following.
i. The electromagnetic force is computed by that part of the working gap magnetic energy that is concentrated in the volume dVo = So'dd directly at the endface surface of the EMT armature during its displacement by a quantity dS. This energy is determined by the magnetic energy density at the site of the change in the working gap volume, i.e., on the other endface surface of the armature.
Improving the vibration safety of hand-operated percussive machines is an important technical problem. The difficulty of solving it is due to the conflicting practical requirements imposed on hand-operated machines. As well as vibration safety they must possess high productivity, low weight, and reliability under stringent conditions, and must be simple to service and cheap to produce.In most cases, the main sources of vibration in the frame of a drill are the reaction R(t) of the periodic force experienced by the frame, the moving striker, and collisions between the frame and the working instrument (bit). It has been theoretically shown [1] that change in the shape of the R(t) diagram permits us to improve the vibrationforce characteristic of the drill.A hand percussive machine will have the best vibration-force characteristic when vibration sources are absent and the thrust necessary for normal operation is minimal. For a stationary bit, it is sufficient that the disturbing force R(t) acting on the frame obeys the conditionwhere Qmtn is the lowest theoretically possible value of the thrust* at which the machine can operate with given values of the principal parameters of the impact mechanism,where Y is the duration of the operative cycle of the machine, z is the number of impacts per cycle (in the exampies which follow, z = 2), A is the energy per impact, and m is the mass of the striker.We will call a Working cycle which satisfies (1) an "ideal" cycle. A machine with an ideal cycle, an"ideal machine," can be regarded, for example, as a set of two strikers with a common frame (Fig. 1). The frame is divided by baffle 4 into two cavities in which strikers 1 and 2 move under the influence of compressed air or some other energy-transfer medium. These strikers inflict blows on the bit 3.The resultant R 1 of the pressure of the energy transfer medium on striker 1 and the resultant R 2 of the pressure of the energy transfer medium on striker 2 are plotted in Fig. 2. The Rt(t) andR2(t ) diagrams are the same, but mutually displaced by T/2. For simplicity, the impulses are represented as rectangular. Under the influence of forces R 1 and R 2 the strikers move in synchronism. The reactions of these forces are received only by the frame. We also assume that the bit is stationary, that there is no recoil of the strikers from the bit, and that the strikers move without friction.It is easy to see that for the operative-cycle parameters thus chosen, the total reaction R of the forces R 1 and R 2 acting on the frame will be constant and minimal. The R(t) diagram is shown in Fig. 2. Thus (1)ishere satisfied, * For machines based on the reactive principle, Qmin = 0.Institute of Mining, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk.
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