On coal charging, coke pushing, and dust removal in coke ovens

I work in the production of rammed coke ovens, and I am also building a surface dust removal station; before this, I was involved with smoke and dust removal vehicles. Our smoke and dust removal vehicles are highly effective, but due to environmental regulations, ground-based dust removal stations are required. To be honest, I have inspected many dust removal stations for coking plants – those designed by various engineering firms – but their performance in reducing smoke and dust is really disappointing; in fact, it’s not even as good as that of my own smoke and dust removal vehicle. So, I’m worried about this issue. However, we can change one first. If it doesn’t work, change it again.

To function properly, a ground station needs to have an excellent dust removal effect. But the investment is large, and the operating costs are high as well. Besides, many of them are not well-made and don’t perform very well; they’re all there just to meet environmental regulations.

Our plant produces compacted coke at a rate of 4.3 units per unit time. We have just modified the coke pushing and dust removal vehicle: there are two traveling vehicles connected to it on the coke side – one is equipped with a dust removal cover and an exhaust fan, while the other is fitted with a Venturi spray dust removal system. The coke dust removed in this way is sent to the coke quenching tank, and the results are very good.

Hehe, but so far, the one that seems to work well is Shanxi Coking

Our facility uses 4.3-meter ramming coke ovens, and we are installing a two-in-one dry-type floor station. The main components include a smoke suppression vehicle (with a combustion chamber), dust collection main pipes, a pre-filter, a 4,000-square-meter bag filter, fans, and a control system. The total cost is approximately 12 million yuan. Waste gas is cooled through air distribution, and the main concern is the service life of the bags. Machine-side dust removal has not been installed yet. This post was last edited by Lao Shi on 2008-1-15 11:26.]

Regarding smoke and dust reduction during coal loading in rammed coke ovens, I advocate the use of high-pressure ammonia water spraying for smoke-free coal loading, as this method helps save energy and reduce emissions. I predict that this approach will replace existing methods for reducing smoke and dust during coal loading in rammed coke ovens! ! !

Our facility produces 4.3-grade rammed coke, and we use floor-based dust removal, which works quite well.

In my opinion, it is best to use dust removal ground stations. Smoke-free coal loading using high-pressure ammonia is a double-edged sword; when used properly, it can achieve smoke-free coal loading； When not used properly, the pressure of ammonia water is too low and the flow rate is small; the resulting negative pressure is insufficient to meet the requirements for smoke-free coal loading, which leads to excessive smoke and fire during coal loading ； Excessively high pressure and flow rate of ammonia water cause a large amount of dust to be drawn into the gas collection duct, from where it enters the primary cooler. This reduces the efficiency of cooling the gas and increases the resistance in the primary cooler as well. The most crucial thing for the dust removal station is to prevent explosions. Generally, it is designed with an explosion vent.

There is another issue: is it necessary to install a pre-filter (or cooler) at the ground station? When I went to the site for an inspection, there were coolers in place, but the temperature at the inlet of the filter was only 30–40 degrees Celsius. The filter can withstand temperatures up to 120 degrees Celsius; it’s likely that without a cooler, the temperature of the flue gas would be around 100 degrees Celsius. So maybe it’s not necessary to use such a device. And what type of valve is used for the accident cold air valve? Electric butterfly valve? Thank you!

A pre-filter is a type of gravity filter; its main purpose is to remove larger particles of dust first, thereby preventing damage to the filter bags. The dust removal system with lower flue gas temperature is likely the top-mounted type, as it is a non-combustion method; whereas ramming-based dust removal involves combustion, resulting in very high exhaust gas temperatures. (We don’t use a cooler either; we rely on air distribution for cooling.)

The pre-filter you mentioned also functions as a cooler; is the air distribution achieved by installing a cold air valve at the inlet of the filter? Is it still by adjusting the fan volume to control the cold air drawn in from the dust collection hood?

Why is combustion needed for ramming and dust removal? Is it because of the high content of smoke and tar? Why does rammed material have a high tar content? Can’t it just not burn even if the tar content is high? The reason for not burning it is probably to avoid the bag from burning up; pre-spraying can be used for that purpose. I hope Old Shi and other experts can help clarify these doubts – there are so many of them. Thank you! This post was last edited by ppm on 2008-1-17 11:47.]

I have discussed these few issues with the designers on many occasions, but the results were not entirely convincing to me. After combustion in the smoke suppression vehicle, air is introduced to cool down the mixture; if the temperature is still high upon reaching the dust collector, the emergency valve is activated to lower the temperature (via automatic control), keeping it below 120°C ； Regarding the combustion issue, since we believe that the flue gas drawn out during coal charging by ramming contains both combustible components as well as air and exhaust gases, and there is a possibility of intermittent combustion, we simply opted for the combustion method ； Coke discharge dust removal and coal loading dust removal are carried out alternately; all the bag filters are used during coke discharge, while half of them are used during coal loading, with rotation between the two processes (the number of furnaces involved in this rotation is determined based on actual conditions), so that the coke dust generated during coke discharge can be used as a pre-spraying coating. I did a brief investigation into users of ramming coal-loading dust removal systems, and found no cases where the results were particularly good; the manufacturer we have chosen also has no existing operational examples yet. Given the practical circumstances, there’s no time to carefully select a dust removal solution (**deadline for use: L**), so we chose this one. But we have a dust removal system for a 3.2-meter ramming furnace here, and something similar to it, which works quite well. Once we put it into use, regardless of the results, I will write in detail about how it was used. I’m not an expert in dust removal; I only got involved in this project hastily, and I only know the basics. Thank you all for offering suggestions – there’s still time for me to take action now.

Coal is loaded from the side through ramming, and the coal-loading smoke is burned at the top of the furnace; the ground station combines two functions together, so it should be possible to use dust removal bags without prior spraying, right? “For the Shanxi Coking plant you are examining, the 6m top-mounted combined dust removal system is used, right? It doesn’t involve combustion, nor is there any pre-spraying, is that correct? Thank you!

Our factory uses 4.3-meter top-loading coke ovens, and we purchased Daejeung top-loading coal feeding cars the year before last. The specific structure consists of a spiral coal-firing combustion chamber, a fan, multi-tube dust removal, and water bath dust removal. The disadvantages are high energy consumption, heavy vehicle weight (60 tons), and significant damage to the furnace. The combustion chamber needs to be preheated regularly; it cannot produce coke continuously. Deflagration often occurs. Due to spiral coal feeding, the coal supply often gets blocked in winter. Based on its principle, we modified the old coal feeding vehicles by eliminating the spiral coal feeding mechanism and introducing gas for ignition at the coal feeding port; we also built a homemade water bath dust removal box, which solved all the aforementioned problems. Easy to operate. Low operating costs. It works very well. The ground dust removal station was designed and constructed in Shanxi; it utilizes the suction power of fans to draw in the dust from coke cars, burn it, treat it with water, and then discharge it – a relatively simple process. However, with the fan located at the back, the suction force is low, so there is basically no dust removal effect; moreover, the equipment corrodes at an astonishing rate – the iron plates in the flue were worn through in less than a year.

Combustion plays two roles during coal charging: 1) A large amount of raw gas is generated during coal charging, and this raw gas can explode when it reaches a certain proportion with air; to prevent explosions in the dust collection pipes, combustion must take place in advance, thereby significantly reducing the proportion of flammable gases in those pipes. 2) Characteristic pollutants associated with coking, such as benzene, toluene, and xylene, are primarily present in the raw gas produced at lower temperatures, and combustion is the best method for reducing and removing these characteristic pollutants.

At present, for coal charging and coke pushing in coke ovens, dry ground-based dust removal systems offer the best results, but they require high investment. For dry ground stations, there are those that combine multiple functions and those with separate systems for coal loading and coke pushing. From the perspective of operation and performance, the separate systems are more stable; a separate dust collection bag for coal loading must be equipped with a pre-spraying device. Our factory’s 6-meter coke ovens perform very well; they operate more stably and have a lower failure rate compared to the mobile and wet-type ovens used with the previous 4.3-meter coke ovens.

Our plant uses 4.3-meter ramming coke ovens, and employs methods such as dust removal from the coke side floor, adsorption combustion on the machine side, as well as the use of smoke guiding vehicles and high-pressure ammonia water spraying for coal loading to achieve good dust removal results. Especially devices like smoke guidance vehicles – we have just started using them, and they work well when used properly; however, they require fairly strict operating procedures.

Our unit has 6-meter coke ovens. High-pressure ammonia water smoke-free coal charging and coke discharge ground dust removal station. It works very well.

Floor dust removal requires a large investment, but it yields good results. Jiaonai Plant also has a dust-removing coal loading vehicle, which, in my opinion, works very well as well; it helps to avoid the problem of no dust removal facilities available during maintenance at the ground station. .