Carbon recycling plant
The carbon recycling plant (auxiliary plant, white side) of a coking plant has the task of using various processes to separate the carbon recyclable materials contained in the raw gas from this. Carbon recycling plants can be compared to a chemical company. The most important carbon materials are raw tar , raw benzene , ammonia ( nitrogen ), hydrogen sulphide ( sulfur ). In the carbon recycling plants (KW-A) physical and chemical processes are used to extract the carbon and the required gas qualities.
History and background
As early as the beginning of the 1840s, English companies opened gas coking plants in the larger cities of continental Europe to generate light gas. The new technology experienced a rapid upswing, as early as 1860 more than 220 German cities had at least one gas station. In 1849, hard coal coke was used for smelting for the first time in the Ruhr area. Technical advances in mining made it possible to extract the fatty coal , which is particularly suitable for coke production, from greater depths. A stormy development set in, in the course of which almost every colliery that extracted fat coal built a coking plant.
The gas generated was initially only used to heat the coke ovens, surplus was burned off or used to generate steam. In the light gas factories, however, the gas was the main product and it was necessary to remove unwanted substances from the gas before it was fed into the pipe network. These initially included the coal tar produced when the gas was cooled and the ammonia water. These were seen as waste products: the tar was mostly buried on or near the gas works and the ammonia water was drained into septic tanks. Or, where possible, used as fertilizer. Due to the contained phenols and rhodanides , this was only possible outside of the vegetation phases.
The hydrogen sulfide still present in the gas was removed with a cleaning compound consisting of lawn iron ores . Benzene and higher hydrocarbons were desirable accompanying substances, as they made up the luminosity of the gas in the dovetail burners of that time. Some of these were subsequently added to the gas and the gas was carburized. The technical improvements of the coking plants ensured that the companies in the Ruhr area could increase their gas production and market it. The cleaning procedures of the gas works were adopted for this.
In the last third of the 19th century, the industrial upswing continued in the chemical-scientific field, coal tar and benzene were discovered as valuable raw materials for the chemical industry and which can be produced from ammonia and artificial fertilizers comparable to Chile's nitrate . Within a few years, waste products were turned into valuable materials that opened up new sources of income for coking plants and, in some cases, surpassed the old ones, gas and coke. The ammonia was now started to be removed from the gas using scrubbers, cleaned and z. Some of them are already used to produce fertilizers at the coking plants.
Since the invention of the mantle in 1885 by Auer , the benzene contained in the gas was also an unwanted accompanying substance and the benzene began to be removed with washing oil and distilled as crude benzene. From the 1920s onwards, the sulfuric acid required for fertilizer production was no longer bought in, but instead produced from the hydrogen sulfide contained in the gas . To do this, the hydrogen sulfide was washed out, separated from the washing liquor and burned to sulfuric acid in contact ovens.
Task
The aim of a KW-A is to produce salable products as inexpensively as possible while keeping the environmental impact as low as possible. The quality requirements for all products must be met.
Components of the raw gas of a medium feed coal (extract):
- Raw tar 100 - 125 g / m³ iN
- Crude benzene ~ 30 g / m³ iN
- Ammonia 6 - 9 g / m³ iN
- Hydrogen sulfide 7 - 11 g / m³ iN
- Hydrocyanic acid 0.5 - 1 g / m³ iN
- Phenols 1.8-3.6 g / m³ iN
The coke oven gas or coke oven gas is fed through the scrubbers and electrostatic precipitators of the low-pressure gas cleaning system by gas suction devices. The low pressure gas cleaning essentially consists of:
- Gas coolers,
- Tar separators,
- Electrostatic precipitator,
- Ammonia scrubber,
- H 2 S washer,
- Benzene scrubbers.
This partially purified gas is z. B. used for underfiring the coke oven battery. The coke oven gas was also fed into the public gas network as town gas. For this purpose, the partially cleaned gas was fed to high-pressure compressors and compressed to 7-10 bar. Compression was carried out by high pressure piston compressors, turbo compressors and, recently, screw compressors have also been used. Since the partially cleaned gas still contains a considerable amount of harmful components, a fine cleaning had to be carried out afterwards. This consists z. B. from:
- Aftercoolers,
- Fine filtering with a bed of lawn iron ore to bind the remaining hydrogen sulfide,
- High pressure benzene scrubber,
- Refrigeration dryer for setting the dew point.
The finally cleaned gas represented the town gas and was fed into the public gas supply. In the Ruhr area, the gas supply was switched to natural gas in the 1970s. Today's buyer of the purified coke oven gas from the Prosper coking plant is " Ruhrgas ".
Individual evidence
- ↑ Former gas works and colliery coking plant locations in North Rhine-Westphalia, in USWF 12/2000 doi : 10.1007 / BF03038047
literature
- Payer / Baum, gas cleaning and by-product extraction (PDF file; 4.8 MB)