Process carried out in factory need steam of should be dry enough to give amount of heat to threads for drying them. But the problem is that steam coming to the process application area, is not dry enough to give satisfactory results. Steam produced at boiler is of required quality but when it reaches to application area it is of low quality.
This is major concern for the factory employees. It also affects operation of process equipment as the equipment has to work under this faulty condition and this will lead to premature failure of process equipment.Even this wet steam cause many other problems like corrosion of gauges, less heat transfer due to layer of water, premature failure due to corrosion of gauges, improper working of equipment under this condition, poor quality of product, higher fuel consumption and higher expense on fuel. This all problem is due to wet steam so we find that this problem is important to consider and there is lot of scope of savings in terms of cost as well as energy.
Another problem was occurring with chimney. Main function of chimney is disposal of waste hot flue gases, produced at the end of combustion process in the furnace, to atmosphere. Here factory is using wood fired water tube boiler, so the wood is fired in the combustion chamber to produce steam in water tubes for process. Then this hot gases coming out of furnace is used for preheat water in economizer. Hot flue gases passing through economizer, will then come to chimney from where it will dispose to atmosphere. Chimney of circular cross section is used. Here the main problem in industry is that chimney is blocked in 6 to 7 days because of disposal of carbon on surface of the chimney wall.
Because of this workers have to clean the chimney every week otherwise the combustion process cannot be proceeded due to choke up of chimney. Boiler operation is off during cleaning of chimney and this makes the boiler to cool down. When the cleaning is done, the boiler can be used. When boiler is started again, it will take some hours to heat it up then it can give actually heat to the water to produce steam.
This will lead to time consuming process as well as productivity is also affected. Due to this problem factory has to face the problems like less productivity, required more time to clean chimney and fully utilization of equipment is not achieved.3.2 Major IssuesDuring visit we had found that there is certain problem in plant regarding to chimney and Quality of steam. Factory workers and senior employees decided to support and help us in our project. They were ready to give any kind of information related to plant based on our project. As in factory two problems are there, so we have decided to include both problems in our project.1) Inefficient steam system3.
2.1 Inefficient steam system:Steam quality is an important factor that affects the quality of product and fuel consumption of process, process time and is directly related to cost of product and cost of fuel. Process carried out in factory need steam of enough dryness fraction that is steam should be dry enough to give amount of heat to threads for drying them and wet enough so that it will not damage the threads. Here we found that steam coming to the process application area, is not dry enough to give satisfactory results.
Steam reached at application area is of less dry. Steam produced at boiler is of required quality but when it reaches to application area it is of low quality. This is major concern for the factory employees. It also affects operation of process equipment as the equipment has to work under this faulty condition and this will lead to premature failure of process equipment.Even this wet steam cause many other problems like Corrosion of gauges, less heat transfer due to layer of water, premature failure due to corrosion of gauges, improper working of equipment under this condition, poor quality of product, higher fuel consumption and higher expense on fuel. This all problem is due to wet steam so we find that this problem is important to consider and there is lot of scope of savings in terms of cost as well as energy.3.
2.1.1 Causes:The steam distribution system is the essential link between the steam generator and the steam user. There are various methods to carry steam from a central source to the point of use.
The central source might be a boiler house or the discharge from a co-generation plant. The boilers may burn primary fuel, or be waste heat boilers using exhaust gases from high temperature processes, engines or even incinerators. Whatever the source, an efficient steam distribution system is essential if steam of the right quality and pressure is to be supplied, in the right quantity, to the steam using equipment. Installation and maintenance of the steam system are important issues, and must be considered at the design stage.An understanding of the basic steam circuit or ‘steam and condensate loop’ is required.
As steam condenses in a process, flow is induced in the supply pipe. Condensate has a very small volume compared to the steam, and this causes a pressure drop, which causes the steam to flow through the pipes.The steam generated in the boiler must be conveyed through pipe work to the point where its heat energy is required. Initially there will be one or more main pipes, or ‘steam mains’, which carry steam from the boiler in the general direction of the steam using plant. Smaller branch pipes can then carry the steam to the individual pieces of equipment.Steam on contact with the cooler pipes will begin to condense immediately. On start-up of the system, the condensing rate will be at its maximum, as this is the time where there is maximum temperature difference between the steam and the pipe work. This condensing rate is commonly called the ‘starting load’.
Once the pipe work has warmed up, the temperature difference between the steam and pipe work is minimal, but some condensation will occur as the pipe work still continues to transfer heat to the surrounding air. This condensing rate is commonly called the ‘running load’.When the valve on the steam pipe serving an item of steam using plant is opened, steam flowing from the distribution system enters the plant and again comes in contact with cooler surfaces. The steam then transfers its energy in warming up an equipment and product (starting load), and, when up to temperature, continues to transfer heat to the process (running load). There is now a continuous supply of steam from the boiler to satisfy the connected load and to maintain this supply more steam must be generated.
In order to do this, more water (and fuel to heat this water) is supplied to the boiler to make up for the water which has previously been evaporated into steam. The condensate formed in both the steam distribution pipework and in the process equipment is a convenient supply of useable hot boiler feed water. Although it is important to remove this condensate from the steam space, it is a valuable commodity and should not be allowed to run to waste. Returning all condensate to the boiler feed tank closes the steam energy loop, and should be practiced wherever practical.