The Bessemer Process Bessemer Converter

Bessemer converter is a pear-shaped furnace, 20 feet high and 10 feet in diameter. It is made of steel plates and is lined inside with brick to resist heat. There are number of holes at the base, called tuyeres, for air circulation. The converter can be rotated on a horizontal central axis.

Process

The Bessemer converter is turned into a horizontal position and molten pig iron is poured into it. A blast of hot air is sent through the tuyeres.
The converter is rotated so that it is vertical and hot air is blown continuously. In its upward travel through the converter, the air oxidises the impurities in pig iron.



Manganese and silicon are oxidised to the respective oxides during the first 5 to 10 minutes. Carbon monoxide is liberated at a later stage and it burns with a blue flame at the mouth of the converter. When all the carbon is oxidised, the blue flame dies out. To convert pig iron to steel, the required amount of carbon is then added. This is in the form of an alloy of iron called spiegeleisen. It contains carbon and manganese besides iron. The resulting product is manganese steel, which is removed by tilting the converter.

Note:

>Adding a little aluminium or silicon-iron alloy to molten steel helps in removing dissolved carbon monoxide or nitrogen from the molten metals.

>Gas must not be left behind as an impurity. The presence of carbon monoxide or nitrogen can cause defects like blowholes in castings.

Slag Formation

The impurities like manganese oxide and silicon dioxide formed during the initial stages of the Bessemer process are removed when they react with each to form a slag.


Note:-

If the cast or pig iron contains phosphorus as an impurity ,the converter should be lined with lime (CaO) and magnesia (MgO) instead of silica.Some lime is also added to the charge.

Hydronic Heat Exchanger - The 3 Basic Types of Hydronic Heating Systems You Should Know

Hydronic heat exchangers or "steam" systems have been around with us since the 1800's at the dawn of the Industrial Age. Steam engines changed the world of transportation almost overnight and steam heat or hydronic heat exchanger systems did the same thing residential and commercial heating.

Almost at the same time that the first steam boilers were made power the great railroad engines, manufacturing mills and cargo ships, steam heat found its way into the home. This is not an unnatural course of events considering the amount of heat that can be put out by steam; as anyone who has ever sat for long in a moist sauna can testify to.

The Theory behind Hydronic Heating Systems

These systems are actually very simple. The most common hydronic heat exchanger consists of three main components: the boiler (the heating source), the piping array and the heat exchangers (which transfer the heat from the water into warmth for the room.)

The process goes like this: water is heated and then either turned into steam or very near to boiling and is then piped to radiators (located through-out the house) or to thermal mass floorings (which absorbs the heat and slowly releases it into the room).

The 3 types of fuel sources for a hydronic heat exchanger are electric, gas or oil-fired boilers. Boilers can be made from cast-iron, stainless steel or copper. While there are different ways that each of these boilers are constructed, each with their own advantages and disadvantages, the main idea to understand that is each boiler is basically heating a closed-water system.

This means that any chronic lost of fluid can cause a problem. This is why the type of piping array becomes critically important to the overall system.

The Three Basic Hydronic Heat Exchanger Types

As you may have guessed by now, hydronic heat exchangers are most often classified by their piping arrangements:

o One-pipe or single pipe

o Two pipe

o Loop series

The oldest of hydronic heat exchanger designs is the one-pipe array. A single pipe carries steam from the boiler to every radiator in the structure. The single-pipe has a layout made so that eventually gravity will pull the condensed water in the piping back into the boiler tank. A two-pipe system uses a second return pipe instead of gravity-induced flow to bring water back to the holding tanks.

Both single and two pipe systems were designed for steam-based heat exchangers but most modern units use hot water in a loop series of pipes as the heat conductors. This type of system offers a slimmer wall-mount, stainless steel heat transfer unit and has better energy-efficient water to air heat transfer rates.

Another advantage of this kind of hydronic heating is that if properly equipped will heat water for domestic uses like cooking, washing or bathing as well as water for external uses such as swimming pools, spas, hot tubs, garages or greenhouses. Plus looped pipe hydronic heat exchangers will not only provide heat in the winter months but can be used to circulate chilled water in the summer months to aid in overall cooling.

So as you can see modern hydronic heat exchanger systems  can not warm you and your family in those cold winter months but also provide a low cost method of central air cooling as well.

After a successful life in trading, importing and exports, Rupert now spends his time writing freelance articles for many well-known publications, as well as various educational institutions. 

Better Heat Exchanger Cleaning Through Technology

Maintenance of a platform's Waste Heat Recovery Unit (WHRU) and similar shell and tube heat exchangers can be an extremely dangerous process. It needs to be disconnected, taken off line, and moved to shore for repair. Shell and tube heat exchangers are made of coiled tubes and can become fouled with carbon deposits. The traditional methods for clearing the blockage include bypassing the fouled unit, cutting off bends and cleaning the tubes, then re-welding the U-bends, and complete unit replacement.

The old methods are becoming more outmoded due to advancements in technology. It is inefficient to bypass the unit. Just as it would be less efficient to run your car with 2 cylinders not firing. This inefficiency, of course, also increases operational costs. It is time consuming and costly to cut the U-bends and re-weld them. Sometimes it can be difficult or impossible to get access to reattach them.

Some of these new methods include the ability to clean areas with limited access, and clear deposits from U-bends without ever removing them. This can sometimes be done without even taking the unit offline, and usually takes less time and results in a higher degree of defouling. In fact, many units can be restored to near-factory efficiency. For big refineries, petro-chemical plants, or power plants, this can amount to six figure savings.

The U-bends themselves also retain many deposits, and continue to be a bottleneck to the system. Full replacement carries the cost of completely replacing equipment that, other than the heat exchanger tube fouling, is still in working order. This method also requires the unit be taken offline for the full duration of replacement. obviously this carries a heavy expense and serious loss of production.

Traditional heat exchanger cleaning methods and heat exchanger cleaning equipment have changed very little over the last few decades. Pressure jetting is still the primary means used by many companies, but it is slow, inefficient, and ultimately very costly. Additionally, many companies are skeptical of newer methods, falling back on the "that's the way it's always been done," chain of logic. They are also weary of trying new techniques that are not as "proven" to be effective. Finally, many have long term tube cleaning contracts that do not allow for a change in heat exchanger cleaning technique, unless the contractor were to adopt the new methods.

Newer heat exchanger cleaning equipment and techniques are more technologically advanced, and by extension, require a higher skilled laborer than old style pressure jetting. These new developments include the ability to clean tight radius bends, clean units while keeping them in place, and even while keeping them online. It has also resulted in faster, more efficient cleaning. Many tube bundles can now be cleaned more effectively than with pressure jetting, and jobs that used to take days may now take only a few hours. Difficult to access units are now accessible with these new technologies.

Some of the technology that has been developed includes special nozzles that can be used on tight bends, laser cleaning, and new "smart" metals that respond to changes in density and pressure to prevent damage to the tubes. With these methods, jobs can be finished with less downtime, because cleaning and descaling can be done more quickly. Equipment is also less likely to be damaged in the process. Many of these new processes are safer, create less waste, use no chemicals, and have a significantly reduced environmental impact.