Gas Generators

Gas Generators, apparatus for the conversion of solid fuel into gaseous or so-called producer gas. In contrast to simple fireplaces, combustion of fuel in gas generators is carried out in a significantly thicker layer of combustible material, with an amount of air smaller than that required for complete combustion of the fuel. Carbon dioxide, formed in the lower zones of the generator by the reaction: C + O₂ = CO₂, is easily reduced at high temperature by carbon of the incandescent fuel, according to the equation: CO₂ + C = 2CO; both these reactions, as proceeding directly one after another, can be expressed by the equation: C + 0.5O₂ = CO. In addition to air, water vapor is also supplied to the generator in most cases, which also reacts with incandescent coal: H₂O + C = CO + H₂. The presence of hydrogen increases the calorific value of the gas. There are several constructions of gas generators, which essentially represent a vertical cylindrical shaft lined inside with fireclay, and covered on top with an iron casing. At the bottom there is a grate, through which air is supplied, and under the grate is an ash pit, where ash is collected. In the lower part of the generator there are pipes supplying air and steam, and the resulting gas is led off to a gas collector or into the gas network through a wide pipe emerging from the upper part of the generator. Above the arch of the generator there is a charging box with a removable lid for charging fuel. In the arch itself there is a series of openings called "stoking" openings, since they serve for stoking (breaking up and leveling the combustible material with staves) and simultaneously for observing the gas. Various fuels are used in generators: coal, coke, brown coal, wood, peat. The composition of producer gas, which, according to Bunge, varies within the following limits, depends on the construction of the generators, and mainly on the type of fuel: Fuel Name Gas Composition in % CO₂ CH₄ C_nH_m N₂ Coal ... 21-26 4-7 1-3 0-2 Coke ... 23-33 1-6 1-4 1-3 Brown coal ... 21-30 1-8 3-5 2-3 Wood ... 17-26 5-11 5-9 4-8 Peat ... 21-28 7-10 8-13 57-68 62-66 58-61 51-59 54-58. The analysis of blast-furnace gas published by Bunsen in 1838 served as a stimulus for the widespread technical use of gas for heating purposes (from 1836). Based on experiments with blast-furnace gas, Bischoff obtained producer gas in special devices (gas generators). When the regenerators (heat collectors) were invented by the Simons brothers in the 1850s, the use of producer gas in industry began to develop rapidly. The possibility of obtaining a significantly higher temperature in the furnaces when using gasified fuel than when using solid fuel is the reason for the widespread use of gas generators in many productions where a very high temperature is required (for example, in the glass, ceramic, zinc-smelting, chemical, and especially metallurgical industries, primarily in open-hearth furnaces).

a - generator shaft; k - column supporting the shaft; b - grate, mounted on the bottom of a rotating dish d, serving as a water seal (ash pit); i - scraper (shovel); (- tuyere; o - gas outlet pipe; p - hole through which steam and air enter the tuyere; g-h - water seal; m - arch of refractory brick; n - stoking box; g - stoking hole for observing the course of work and breaking up large pieces of coke. Gas generators are also used for the extermination of suspicious rats and mice on ships. Producer gas, consisting of a whole series of harmful gases, among which a large percentage falls on the typical blood poison - CO, is a serious source of a huge number of occupational poisonings and diseases of workers in the aforementioned productions. Although generators, as well as the gas pipelines leading from them, through which gas is supplied to the furnaces or other units, are hermetically sealed in the technical and production sense, nevertheless producer gas usually seeps out in quantities, although ignored in technology, but quite sufficient to cause pathological phenomena in workers. In countries where the mandatory registration of occupational poisonings is carried out, statistics annually record cases of poisoning by producer gas. Thus, in England for the years 1908-12, 119 cases were registered in this category, of which 11 were fatal. Such poisonings were also noted in the USSR. The components of producer gas, including sulfur compounds, cause various diseases, primarily of the respiratory tract, and the high temperature and its sharp fluctuations when working at generators, usually arranged in semi-open premises (tunnels), in combination with great physical strain during their maintenance (loading, stoking, cleaning, ash removal) contribute to the spread of rheumatic and cold diseases among the corresponding groups of workers. Serious improvement of working conditions with gas generators can be achieved by the following measures. From a hygienic point of view, it is advisable to recommend Morgan system gas generators, which are equipped with specially designed charging devices and grates. The charging device consists of a so-called iron hopper, equipped with a double lock in the form of a lid and a cone connected to each other. Such a device allows replenishing an operating generator with fuel without at the same time allowing gas to escape in large quantities. Fuel is supplied via bunkers installed above the generators, thanks to which it is automatically poured into the charging device. The grate construction eliminates the need for manual cleaning of it (one of the heaviest operations) and removing hot ash, since ash and clinker automatically enter ash tanks located under the generators, filled with water, from which they are easily removed in a cold state. Moreover, the construction of Morgan gas generators does not require tuyere rooms, which allows them to be installed at ground level, whereas all gas generators of other systems are installed at a depth of 4-5 m, which significantly worsens the already heavy working conditions of tuyere workers. To avoid the most harmful moment of work - gas blowing out during stoking, the stoking holes must be provided with steam pipes, from which steam enters with significant speed and, together with the entrained air, creates a continuous cylindrical steam-air curtain in the hole, preventing the gas coming from the generator. Work with gas generators is classified by Soviet labor legislation as particularly harmful, compensated by an additional two-week vacation.