Ammonium Sulphate – A By-product of Coal Coking Process...

Ammonium Sulphate – A By-product of Coal Coking Process Ammonium sulphate is produced as a by-product during removal of ammonia (NH3) from the raw coke oven gas generated during the coking of the metallurgical coal in by-product coke ovens. Its industrial production began over a century ago, as by-product in gas cleaning in coke and coal gasification plants. Ammo­nium sulphate is produced as crystals. It is an organic, white odorless solid and crystalline salt with a number of commercial uses. It contains around 21% nitrogen (N2) and 24% sulphur (S). The Chemical Abstracts Service (CAS) registry number for ammonium sulphate is 7783–20–2. Its EC number is 231-984-1. Its IUPAC ID is Diazanium sulfate. It is currently classifiable under Harmonized Tariff Schedule of the United States (HTSUS) subheading 3102.21.0000. This process by which ammonium sulphate is produced consists of absorption of ammonia in the coke oven gas in a solution of ammonium sulphate and sulphuric acid. The absorption reaction is 2NH3 + H2SO4 = (NH4)2SO4. The ammonium sulphate produced by the reaction of NH3 with H2SO4 is recovered by crystallization. The crystals are then centrifuged, washed and dried. Since ammonium sulphate is produced as a by-product during the recovery of ammonia from coke oven gas, there are normally a lot of impurities from different sources. These are organic impurities as well as the inorganic impurities. The combined effects of these impurities are complex and influence the purity and the crystal shape and size. Ammonium sulphate is available in a variety of grades, including granular and standard grades. Granular grade accounts for the vast majority of the market.  Its relatively large particle size (typically 2.5 mm) makes it well suited for mixing with other fertilizers and application by spreading machines.  Standard grade has a smaller particle size (less than 2 mm) and...

Recovery of Ammonia during Production of Coke from Coking Coal Jan26

Recovery of Ammonia during Production of Coke from Coking Coal...

Recovery of Ammonia during Production of Coke from Coking Coal Ammonia (NH3) is a by-product produced during the production of coke from coking coal in the by-product coke ovens. It is a constituent of the coke oven gas (COG) leaving the coke ovens, with a typical concentration in raw COG of 6 grams per normal cubic meters (g/N cum). The solubility of NH3 in water leads to its presence in the flushing liquor of coke oven battery (COB) with a typical concentration of 5 grams per litre (g/l) to 6 g/l of total NH3. Therefore, due to the net production of flushing liquor in the COB, also sometimes being referred to as excess flushing liquor, there arises a liquid stream as well as a gas stream from which NH3 is required to be removed. The quantity of excess liquor is around 12 % of the dry coal throughput, which depends on the coal moisture content. Removal of NH3 from the gas stream is a universal feature of a coke oven and by-product plant. This is because NH3, in the presence of the other COG contaminants hydrogen cyanide (HCN), hydrogen sulphide (H2S), oxygen (O2), and water, is extremely corrosive to pipelines made of carbon steel. Also, when ammonia is uncontrollably burnt in any combustion chamber, it forms nitrogen oxides (NOx) which causes air pollution. Hence, removal of NH3 from COG and liquid stream is required to be also done due to environmental reasons. The primary NH3 handling process in the coke oven and by-product plant deals with the removal and disposal of the NH3 present in the COG. However, NH3 recovery systems often include facilities to handle the NH3 arising in the excess flushing liquor. For proper understanding of how these facilities are incorporated into...

Coke Oven By-Product Plant Jan17

Coke Oven By-Product Plant...

Coke Oven By-Product Plant The coke oven by-product plant is an integral part of the by-product coke making process. During the production of coke by coal carburization in a coke oven battery a large amount gas is generated due to the vaporization of volatile matter in the coal. The gas is generated over most of the coking period, the composition and the rate of evolution changing during this period and being normally complete by the time coal charge temperature reaches 700 deg C. This gas is known as raw coke oven gas and is processed in the by-product plant. The functions of the by-product plant are to process the raw gas to recover valuable coal chemicals and to condition the gas so that it can be used as a clean, environmentally friendly fuel gas. After leaving the coke oven chambers, the raw coke oven gas is sprayed with flushing liquor so as to reduce its temperature to a reasonably low level and to condense the most easily condensable (high boiling point) components. The raw gas is cooled by adiabatic evaporation of some of the spray liquor to around 80 deg C and is water saturated. The temperature of the gas becomes sufficiently low so that it can be handled in the gas collecting mains. From the gas collecting main the raw coke oven gas flows into the suction main. The amount of flushing liquor sprayed into the hot gas leaving the oven chambers is far more than is required for cooling, and the remaining flushing liquor which is not evaporated provides a liquid stream in the gas collecting main. At this stage there are two streams namely a liquid condensate stream and a gas stream. The two streams pass through a butterfly control valve...