PROCEEDINGS
OF THE TOMSK ORDER OF THE RED BANNER OF LABOR POLYTECHNIC
INSTITUTE named after S. M. KIROV

Volume 150 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1968

ON THE OPERATION OF REGULATING DEVICES WITH UNPURIFIED MIXED PRODUCER GAS

A. A. Gurchenok, V. D. Serebrennikov, Yu. M. Trifonov
A. F. Fedorov

(Presented by Prof. G. N. Kokom)

At some enterprises, furnaces operate on unpurified mixed producer gas. The use of mixed producer gas has a number of advantages, the principal ones being: preservation of the physical heat of the gas, which leads to fuel savings; absence of apparatus for washing and purifying the gas; and a reduction in the length of communications. However, operation on unpurified producer gas causes certain difficulties connected with the deposition, inside gas pipelines and on regulating devices, of mechanical fuel particles and tars carried over from the gas generator. Hot-gas stations are characterized by communications of large cross section, so that, even with considerable deposits of carryover in them, the necessary flow areas are preserved. Under these conditions, however, the operation of regulating and shutoff equipment is impaired.

The present work gives the results of an investigation of the behavior of a regulating damper in the temperature-control system of the melting section of a glassmaking furnace at the Tomsk Electric-Lamp Plant.

The plant’s gas-generator station operates in direct connection with the consumer—the glassmaking furnaces. The sequence of arrangement of the units is as follows: mixed-gas generators, dust separator, hot valve, gas manifold with dust bag, and gas pipelines to the furnaces.

Coal from the Kuznetsk basin is used for the gasification process. Operation of the gas generator is characterized by the following: coal consumption—1.4 t per hour; gas temperature in the gas manifold—350°C; gas pressure—60 mm water column.

The gas manifold is made in the form of a metal pipeline 900 mm in diameter, inside which insulating brick is laid in a single roll course. The test regulating device was installed on a branch from the gas manifold of 400 mm diameter and was made in the form of a rotary damper of 360 mm diameter with a clearance of 20 mm. The flow area of the test regulating device was made oversized, which made it possible not to clean it of deposits for a long period of time (2–4 months). Opening the gas pipeline showed that deposits are observed both on the walls of the gas pipeline and on the damper disk itself. Figure 1 shows samples of deposits taken at the point where the gas pipeline branches from the main manifold, ahead of the damper. The samples have a rounded shape corresponding to the direction of the gas flow. The entrance to the branch gas pipeline proved to be bordered by an involute-shaped ring with traces of adherence.

toward the inlet to the gas pipeline. These formations facilitate the unhindered entry of the gas into the branch gas pipeline. Figure 2 shows samples of deposits on the rotary damper. On the end face the deposit reaches 25 mm (Fig. a). Figure b gives samples of deposits on the end

Fig. 1. Samples of deposits taken from the pipeline.

Fig. 2. Samples of deposits taken from the surface of the damper.

face, with traces of contact with the surface of the gas pipeline. Figures c and d show samples with a transverse fracture, from which the layered structure of the deposits is visible. Thus, over the entire surface of the damper, deposits

almost uniform. Because of the presence of deposits on the ends of the damper, its rotation was limited.

The results presented for the operation of the test regulating damper were used in designing the system for automatic temperature control.

It is obvious that, as deposits accumulate, the resistance of the damper will increase. Therefore, in calculations the diameter of the regulating member must be chosen with allowance for a possible reduction in the flow area. The regulating damper was designed so that, in the clean state, the required gas flow rate was attained at 30% opening. As fouling proceeds, the required degree of opening of the regulating member increases and reaches full opening (Fig. 3). After this, the damper must be stopped and cleaned of deposits, and the operating cycle is then repeated.

Fig. 3. Graph of the change in the position of the regulating member in % of CP between cleanings.

The rate of growth of deposits is small and does not affect the quality of regulation; a drawback of the damper is the need to stop it for cleaning operations, which, allowing for cooling and then reheating of the furnace, takes 6–8 hours.

In Fig. 4 the following relation is shown:

\[ x=\frac{2}{\pi}\left(\frac{d_1+d_2}{2}\right) \]

Fig. 4. Diagram for calculating the resistance moment when rotating the damper.

The mechanical strength of the damper was calculated with allowance for the mechanical forces required to remove deposits on the contact surface (Fig. 4). The greatest mechanical stresses will occur under the condition that crushing takes place along the entire perimeter of the contact surface.

If \(F\) denotes the area of contact of the damper surface with the crushed surface, and \(x\) the distance from the axis of rotation to the center of gravity of the perimeter of crushing, then the resisting moment will be

\[ M_y = \sigma_y \cdot F \cdot x, \]

where \(\sigma_y\) is the compressive strength of the deposits.

To determine \(\sigma_y\), specimens were made from the deposits and crushing tests were carried out. For specimens crushed along the fibers, the compressive strength varied within the range \(13.5\)—\(19.7\ \mathrm{kg/cm^2}\); across the fibers, \(4.2\)—\(12.1\ \mathrm{kg/cm^2}\).

The higher values apply to specimens taken from areas of the damper contact surface.

A mechanical calculation of the damper elements, carried out with allowance for the need to crush the deposits, showed that the shaft diameter and disk thickness must be considerably greater than in standard designs.

Conclusions

1. When selecting the cross section of a regulating element for operation on unpurified mixed producer gas, the design condition should be taken as that for obtaining the nominal gas flow rate with the damper opened by \(30\)—\(35\%\).

2. When using standard dampers, a verification calculation for mechanical strength must be performed, taking into account the forces required to crush the deposits.

3. Operating experience has shown sufficiently reliable performance of the regulating element in the automatic temperature-control system of a glass-melting furnace when operating on unpurified mixed producer gas.