Re: Need For Speed Carbon Steam Key
Avery Blaschko
Natural gas reforming is an advanced and mature production process that builds upon the existing natural gas pipeline delivery infrastructure. Today, 95% of the hydrogen produced in the United States is made by natural gas reforming in large central plants. This is an important technology pathway for near-term hydrogen production.
Subsequently, in what is called the "water-gas shift reaction," the carbon monoxide and steam are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final process step called "pressure-swing adsorption," carbon dioxide and other impurities are removed from the gas stream, leaving essentially pure hydrogen. Steam reforming can also be used to produce hydrogen from other fuels, such as ethanol, propane, or even gasoline.
In partial oxidation, the methane and other hydrocarbons in natural gas react with a limited amount of oxygen (typically from air) that is not enough to completely oxidize the hydrocarbons to carbon dioxide and water. With less than the stoichiometric amount of oxygen available, the reaction products contain primarily hydrogen and carbon monoxide (and nitrogen, if the reaction is carried out with air rather than pure oxygen), and a relatively small amount of carbon dioxide and other compounds. Subsequently, in a water-gas shift reaction, the carbon monoxide reacts with water to form carbon dioxide and more hydrogen.
Reforming low-cost natural gas can provide hydrogen today for fuel cell electric vehicles (FCEVs) as well as other applications. Over the long term, DOE expects that hydrogen production from natural gas will be augmented with production from renewable, nuclear, coal (with carbon capture and storage), and other low-carbon, domestic energy resources.
Petroleum use and emissions are lower than for gasoline-powered internal combustion engine vehicles. The only product from an FCEV tailpipe is water vapor but even with the upstream process of producing hydrogen from natural gas as well as delivering and storing it for use in FCEVs, the total greenhouse gas emissions are cut in half and petroleum is reduced over 90% compared to today's gasoline vehicles.
A few years ago I was talking on the telephone with the retired Director of Research at Ransom and Randolph. I cannot recall the exact topic of discussion but it had something to do with burnout time. He suggested that I could burn out a flask much faster if I put it into a hot oven rather than ramping the temperature up slowly over a period of hours. I remember remarking that I thought that the sudden thermal shock might cause the investment to crack but I tried his suggestion.
First, I was cautioned to make sure that the flask was not partially dried. That might cause cracking. If the flask had set for several hours or over the weekend it should be immersed in water until the investment is thoroughly moistened. Then if the flask is placed in a hot oven, the moisture in the pores of the investment will turn to steam and escape. As long as water or steam is present, the flask internal temperature cannot rise above 212 F (100 C) the boiling point of water. In the case of small 2 x 2.5 inch flasks the core temperature remains at 212 F (100 C) for about 20 minutes until all of the water is vaporized. At the same time the wax melts and runs out of the sprue and pouring cup. The investment does not crack and I have done this fast burnout many times.
Once all the water leaves the pores in the investment, the flask rapidly rises to the final burnout temperature where I allow it to remain until all the wax is completely eliminated. This is determined by looking at the sprue opening and the pouring cup in the flask. As long as the surface around the opening is gray we know the burnout is incomplete. The gray coating is incompletely vaporized carbon residue. When all wax or carbon residue is gone the burnout is complete. The opening of the flask is chauky white. Total burnout time is as long as it takes to obtain a white flask and is not dependent on any particular time-temperature program. Small flasks will burnout rapidly in an hour or two while large flasks (or an oven full of small flasks) will take longer. The test of how long is the white color of the sprue opening and pouring cup.
I must admit I have never partially dried flasks for different lengths of time to see when it will cause the investment to crack during burnout. If I must allow flasks to sit around for several days before burnout, I usually immerse them in water or throw a wet rag over them to keep the flasks saturated.
has anyone got more information/ finer details of this process. I am new to casting but would like to learn right. What is meant by partially dried flask? how to check? process someone is using that works as a quality control method?
This is very similar to the process we used to create our sea shell pieces in out Sealife line. It maybe a lost art but its still the best. We recreated actual shells from our own beach home into beautiful keepsakes for ourselves and other Sanibel Beach lovers to cherish for years to come. Check it out.
We have proposed a new support system that shows the internal state and future behavior of plant operations using an online process simulator. For improved simulation accuracy, we propose a tracking simulator that works simultaneously with actual process operations and automatically adjusts the simulation parameters. In this paper, we describe the application of the tracking simulator to an actual steam reforming process for fuel cells. We also present composition estimation and prediction as features of the operation support system.
The process industry in Japan faces increasingly critical environmental and safety issues. Additionally, in Japan, many skilled engineers with years of experience will be retiring in 2007. Although the process industries such as petroleum, petrochemical, steel and paper, etc., are highly automated, human skill is still required in an abnormal situation or for a critical production change. Thus, new solutions are needed to overcome the above problems.
The opportunity of manual operations due to abnormal situation is reduced due to the increased stability and reliability of plants and their control systems. A training simulator for teaching operators how to handle start-up, shut-down, and other operations under abnormal situation has been developed and is widely used in process industries. These process simulators faithfully demonstrate actual plant behavior due to the accurate modeling of physical and chemical phenomena.
If the process simulator were to work simultaneously with the actual plant, operators would gain a deeper understanding of crucial plant phenomena. For instance, the following operation support can be expected:
However, to ensure that plant behavior is displayed exactly, the parameters of the simulator must be adjusted exactly. Thus, we propose a tracking simulator that works simultaneously with the plant and automatically adjusts the simulation parameters.
To demonstrate the tracking simulator using an actual plant, we constructed the experimental plant of steam reforming process shown in Figure 1. This experimental plant converts methane in natural gas into hydrogen for a fuel cell unit.
The process consists of 4 main parts: bubbler, reforming reactor, shift reactor and preferential oxidation (PROX) reactor. The bubbler is used for humidification of the feed gas, i.e. methane gas. Methane gas is mixed with water in this unit. Hydrogen (H2) is generated when the gas mixture passes through the catalyst bed in the reforming reactor, which is called the steam reforming reaction. Carbon monoxide (CO) is also generated as a by-product of this reaction. Then, the shift reactor generates H2and CO2 from residue CO and steam by the shift reaction. Finally, to eliminate residue CO, it is combusted with air (O2 ) in the 14 Yokogawa Technical Report English Edition, No. 43 (2007) PROX reactor.
Electric heaters are mounted on all reactors and the bubbler, and they are controlled by adjusting the current. The experimental plant is equipped with the process control system STARDOM, developed by Yokogawa.
Entire units including not only reactors but also valves, heat exchangers, etc., are modeled in our plant simulator. However, only the reactor model is discussed in this paper due to space limitations.
where r is reaction rate, xi is componential molar percent, P is total pressure, T is temperature, R is gas constant, Nc is number of components, k1 is frequency factor, k2 is activation energy, and Np, Nt, Ni are exponent coefficients of pressure, temperature, and concentration.
Next, at each partition in the catalyst layer, heat balance is calculated using reaction heat Q, heat transfer from the reactor wall q, inlet enthalpy h0 and outlet enthalpy h1. Therefore, the equation is expressed as equation (3).
The heat transfer from the reactor wall to the catalyst layer q is proportional to the temperature difference between the reactor wall and the catalyst. Heat emission qa is proportional to the difference between the reactor wall temperature and outside air temperature Tatm. They are described as follows:
where Aw and Uw are heat transfer surface area and heat transfer coefficient between the reactor wall and the catalyst, Aa and Ua are heat transfer surface area and heat transfer coefficient between the reactor wall and outside air.
As mentioned above, the other two reactors are modeled in the same manner as the steam reforming reactor. The entire process is modeled by constructing such a model for each piece of equipment. It is possible to construct an accurate plant simulator by using the process modeling technique based on physical and chemical laws.
In this study, we use the OmegaLand, integrated environment for dynamic simulator based on physical and chemical engineering. In OmegaLand, the models for general equipment such as valves and heat exchangers are installed as a library of standard units. There is also a useful graphical modeling environment in which the process model is easily constructed simply by using the mouse to connect component units.
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