Once upon a time, coke oven gas was considered a by-product in the process of making coke, so often it was even vented to the atmosphere (which is a very waste!). Later, gas was used to heat coke ovens, and today it is already fully distributed to outside consumers for domestic use and other needs. How is coke gas produced and what is its composition? This article discusses all aspects of the issue and provides specific examples of the use of gas.
Historical aspect
The history of coke oven gas began in the late 19th - early 20th century. Even then, it was used for lighting, heating and, accordingly, for cooking and other household chores. At that time, the industrial revolution and urbanization broke out. The production of by-products, coal tar and ammonia began to serve as the most important components, namely raw materials, in the manufacture of dyes of a chemical composition and in the chemical industry as a whole. Thus, absolutely all types of dyesartificial nature were made from tar and coke oven gas.
In addition, coke oven gas has become widely used in furnaces for the manufacture of industrial products, in gas-fired engines and, of course, as a raw material in the production of chemical products.
Production of coke oven gas
Obtaining coke oven gas occurs simultaneously with the production of coke at coke plants by dry distillation of coal. It is important to note that this process must necessarily proceed at a temperature of 900-1200 degrees. As noted above, at the initial stages of generation, gas was considered a by-product, so it often escaped into the atmospheric air. A little later, coke ovens began to be heated with coke oven gas. Thus, gas consumption for personal needs has undergone a significant reduction (almost to 60%), while the rest of the amount belonged to other categories of consumers, for example, for heating furnaces in metallurgical production, the temperature of which is extremely high, or for household chores. Today, absolutely all gas belongs to outside consumers. Why? The fact is that coke oven gas is very high in calories, which means that it is possible to use cheaper gas for heating furnaces. LPG is a prime example of this. By the way, it is based on a propane-butane mixture.
Coke oven gas composition
As it turned out, from a variety of gasesof artificial origin, the gas considered in the article and obtained in the process of coal coking is of great importance. It should be noted that from a practical point of view, its composition undergoes significant fluctuations. This depends, as a rule, on the feedstock that is used as fuel, on the difference in modes of operation, on the physical condition of the coke ovens, and so on. Its calorific value lies within 15-19 MJ/m3. If we consider the components of this gas as a percentage of the volume, then the following picture is formed:
- H2: 55-60.
- CH4: 20-30.
- CO: 5-7.
- CO2: 2-3.
- N2: 4.
- unsaturated hydrocarbons: 2-3.
- O2: 0, 4-0, 8.
It is important to note that coke oven gas (formula: H2CH4NH3C2H4) has a density at a temperature of zero degrees from 0.45 to 0.50 kg / m3, the heat capacity is equal to 1.35 kJ / (m3 K), and the temperature, accompanying the ignition process, reaches 600-650 degrees.
Substance formula
As it turned out above, the composition of coke oven gas includes substances such as hydrogen (H2), methane (CH4), ammonia (NH3) and ethylene (C2H4). As an example, it would be appropriate to give the following composition of purified coke oven gas:
| Component | H2 | CH4 | CO | N2 | SN | O2 |
| Content, % | 55, 5 | 27, 6 | 8, 2 | 6, 0 | 2, 0 | 0, 7 |
It is important to note that the composition of the gas under consideration is strictly dependent on the temperature regime of the coking process and its duration. The quality of the coal being processed also plays a huge role. Thus, the higher the temperature regime of the coking process, the higher the level of decomposition of hydrocarbons, and hence the higher the content of hydrogen and carbon monoxide in the gas. Accordingly, the content of carbon dioxide, on the contrary, will be lower.
Need for coke gas cleaning
Today, the problem of the need to clean coke oven gas is quite acute, because this composition adversely affects the environmental aspect of life. Thus, modern society strives to improve the relevant technologies. Cleaning of coke oven gases is necessary for the efficiency of plant mechanisms, because hydrogen cyanide, whose content in coke oven gas is quite high, is the main cause of corrosion of professional equipment. In addition, ammonia is necessarily released during the formation of coke oven gas. This substance has an extremely detrimental effect not only on pipelines, but also on the environment, because it eventually gets there. The result of the considered operations is a high level of loss of products of chemical origin for a particular plant, andalso a significant degree of emission of gases and wastes of liquid origin into the atmosphere.
Coke gas cleaning process
As it turned out, the production of coke oven gas entails a number of problems, which fully justifies the need for its purification. To date, the most effective method is the invention described in this chapter, which is widely used in the coke industry. First of all, it is necessary to flush the gas with an ammonium phosphate solution in an absorber, which must be equipped with trays. Next, the coke oven gas should be treated with this solution before it enters the tray area of the absorber. In this case, the specific consumption of the circulating solution should be 1.0-1.2 l/m3 of gas, then its density will be equal to 1.195-1.210 kg/l. This method of cleaning coke oven gas, as noted above, is often used today in the relevant industry, because it is the most effective.
Coke oven gas application
Today, coke oven gas is very widely and safely used in society as a fuel in metallurgical plants, as well as in municipal economic activities and as a raw material for production. As it turned out, hydrogen is emitted from coke oven gas, which is simply necessary for the synthesis of ammonia by means of a known method of condensation functioning under the condition of a low temperature regime. As a result of thisDuring the operation, a fraction is formed that serves as a high-quality raw material for various kinds of syntheses. It should be noted that the admixture of hydrogen sulfide in coke oven gas is absolutely undesirable in any case (both when coke oven gas is used as a fuel and when it serves as a raw material for the production of chemical products). That is why the cleansing process, which was fully discussed in the previous chapter, is so necessary.
Gas properties
In conclusion, it would be appropriate to consider the physical properties of coke oven gas. Thus, its calorific power is from 3600 to 3700 kcal / m3, the specific gravity in the composition of the substance varies from 0.45 to 0.46 kg / m3 (which is almost three times lighter than air), the maximum temperature regime of its combustion is equal to to 2060 degrees, and the process itself is accompanied by a red flame.
It is important to note that the gas in question is explosive when combined with air. Moreover, the lower explosive limit by volume is 6 percent gas (the rest is air), while the upper explosive level reaches 32 percent gas (the rest is air). The ignition temperature is equal to 550 degrees, and to burn 1 cubic meter of gas, approximately 5 cubic meters of air are needed. Coke gas is not endowed with color and taste, but it has a tart smell of naphthalene, rotten eggs, which can be explained by the content of hydrogen sulfide in its composition.
