Rationalization of the Thermal Regime of a Glass-Melting Furnace
Abstract Generated abstract
This paper examines excessive fuel consumption in glass-melting furnaces at the Tomsk Electric-Lamp Plant. The authors installed gas metering diaphragms, introduced forced air supply to the regenerators for more controllable regulation, and measured gas and air flows together with combustion-product composition. Contrary to the prevailing assumption that fuel losses resulted from insufficient air, incomplete combustion, or burner short-circuiting, the measurements showed combustion with a very large excess of air and no detectable combustible gases in the exhaust. The resulting adjustment of air supply reduced water-gas consumption to about 470 normal cubic meters per hour, corresponding to a specific heat consumption of 5937 kcal per kilogram of melted glass.
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Rationalization of the Thermal Regime of a Glass-Melting Furnace
P. A. Andriyanov, N. N. Norkin
(Presented by Prof. I. V. Gebler, Doctor of Technical Sciences)
The work was carried out at the Tomsk Electric-Lamp Plant in connection with the large overconsumption of fuel for heating glass-melting furnaces. Prior to the present work, the plant had no metering of water-gas consumption. One of the authors (P. A. Andriyanov) designed diaphragms; at his direction they were manufactured and installed on the gas pipelines to two glass-melting furnaces.
At the plant there was a widespread opinion that the overconsumption of gas was due to a shortage of air, incomplete combustion of the gas, and leakage of gas into the downdraft regenerator as a result of “short-circuiting” of two burners. The task of the present work was to establish the true cause of the gas overconsumption and to eliminate this overconsumption.
For heating the furnaces, water gas of the following composition is used: CO—38.4%; H₂—50.7%; CH₄—1.88%; CO₂—4.95%; O₂—0.45%, and N₂—4.41%. The calorific value of the gas is \(Q_{n}^{p} = 2626\) kcal/nm³. For combustion, the theoretically required amount of air is 2.28 nm³/nm³; this gives 2.84 nm³/nm³ of combustion products of the following composition: CO₂—16.0%; H₂O—19.2%; N₂—64.8%. The calorimetric combustion temperature with air preheated to 1100°C is equal to 2570°C.
In the gas pipeline \(D = 104\) mm, a diaphragm \(d = 80\) mm was installed, whose calculation formula is
\[ V = 74.4 \sqrt{\Delta p}\ \text{m}^3/\text{h}, \]
where \(\Delta p\) is the pressure drop in mm of water column.
Fig. 1. Air-supply scheme to the furnace.
1. Regenerator. 2. Air duct. 3. Gate valve. 4. Change-over drum. 5. Water seal. 6. Under-batch channel.
Before the present work was carried out, air was supplied to the regenerators by the natural draft of the regenerators; the change in air flow rate was regulated by changing the cross section of the opening in the butterfly valve by means of a damper. The authors proposed forced air supply to the regenerators by means of a fan, for the purpose of rapid and convenient regulation of the air flow rate. This air-supply system is shown in Fig. 1. Measurements of the gas flow rate (by an orifice plate) and of the air flow rate (by a vane anemometer) gave the following results: gas flow rate up to 560 nm³/hr, air flow rate up to 2000 nm³/hr, which corresponds to an excess-air coefficient \(\alpha = 2\). Analysis of the combustion products was carried out using a VTI chemical gas analyzer; samples were taken at the top of the end wall of the regenerative chamber before the flue gases entered the checkerwork, as shown in Fig. 2. Composition of the combustion products: CO₂, from 9.75 to 10.45%; O₂, from 9.65 to 10.6%; CO, H₂, and CH₄—not detected.
Fig. 2. Sampling of combustion products. 1. Regenerator checkerwork. 2. Fireclay tube for sampling. 3. Regenerator. 4. Burner. 5. Working chamber.
Thus, the combustion of water gas was carried out with an extremely large excess of air, which caused excessive consumption of water gas.
As a result of the work carried out (installation of monitoring and measuring instruments, change in the air-supply system, regulation of the air supply), the air consumption and the consumption of water gas were reduced; at present the consumption of water gas is 470 nm³/hr, which corresponds to a specific heat consumption of 5937 kcal/kg of melted glass.