Steam fuels

Ingress of Water, Steam, Fuel, Lubricants, Corrosion Products from High Pressure System... 

Pressure Stripping Steam Booster Steam Fuel... 

In 1999 a new gasifier was installed at the Institute. This gasifier has the same basic design as mentioned above, but an improved operation performance as the previous one. The experiments, shown in this paper, were carried out in the old pitot plant as well as the new one. As fuel for the experiments wood pellets were used. These have the advantage, that the water contents is very low (<10%) and it is a standardised fuel with nearly the same composition over the whole year. The steam-fuel ratio was varied from 0,18-0.8 kg steam per kg dry fuel. The steam-fiiel ratio is calculated in the following way ... 

As known from literature, the gas composition depends mainly on the used fuel, on the temperature and on the steam-fuel ratio [4,8,9]. The gas composition depends also on the residence time, but in all experiments the residence time was kept as constant as possible. Therefore in the following diagrams the dependency of the dry product gas composition to these parameters is shown. The nitrogen content for all experiments was below 5 vol% and is not shown in the diagrams. The rest to 100 % is nitrogen and higher hydrocarbons. From the gaschromatographic analysis it can be seen, that the main component of the these hydrocarbons is ethene. 

With the results of these measurements the gas composition of the product gas can be calculated for different steam-fuel ratios and temperatures. The next step will be to improve the model of the gasifier on basis of this measurements. 

As known from previous experiments the tar content depends strongly on the gasification temperature. Here the dependency of the tar content on the steam-fuel ratio was studied. In the first diagram the dependency of the tar content on the steam-... 

In the next diagram the tar dependency on the temperature is shown at different steam-fuel ratios. For this diagram two steam-fuel ratios were used to show the dependency of the tar content on the temperature. 

It can be seen from the diagram, that the dependency on the temperature is higher at a low steam-fuel ratio. It is also shown in this diagram, that a higher steam-fuel ratio causes a lower tar content in the product gas. From these results it was realised, that the optimal steam-fuel ratio for a low tar content is higher than 0.5 kg steam per kg dry fuel. The optimal temperature for a low tar content is higher than 850°C. 

In the next diagram the dependency of the steam content in the product gas on the steam-fiiel ratio is shown. It can be seen, that the steam content in the product gas increases with increasing steam-fiiel ratio. It can be also seen, that there is no linear dependency. At a steam-fiiel ratio of about 0.1 kg/kg all steam would be used by the gasification reactions. This steam-fuel ratio could not be investigated by experiments, because the lowest steam-fiiel ratio, which is possible at the lOOkWih gasifier is 0.15 kg/kg. 

It can be seen, that the water conversion decreases with increasing steam-fiiel ratio. Also the influence of the temperature on the water conversion was investigated. As estimated before, the water conversion increases with increasing temperature. From these results it can be estimated, that the optimal steam-fuel ratio is below 0.5 kg steam per kg dry fuel. Above this ratio the water conversion is almost constant and more steam causes only more steam content in the product gas, without shifting the reactions to the desired side. 

In the lOOkWd, pilot plant two steam-fiiel ratios for all further experiments could be defined. One is 0.25 kg/kg, which causes a high tar content, but also a low steam content in the product gas, the second is 0.5 kg/kg, which causes a tower tar content, but also a higher steam content in the product gas than the first one. With this two steam-fuel ratios all further experiments will be done and the separation efficiencies of the gas treatment system will be investigated. 

Sharma, R.K, and Bakhshi, N.N. Catalytic Conversion of Crude Tall Oil to Fuels and Chemicals over HZSM-5 Effect of Co-feeding Steam. Fuel Process. Techno . 27, 113-130, 1991. 

With induced FGR into the fuel gas (IFGR) and steam (fuel gas) 0.01 (low flux boiler)... 

In the third zone, slow secondary reactions take place. The carbon particulates formed react with C02 and steam to form synthesis gas. However, these slow reactions do not reach equilibrium due to low residence time in the reactor, leaving some carbon formation in the reactor. The final composition of the synthesis gas is determined by the water-gas-shift reaction (Reaction 2.2). The key variables to control outlet gas composition are the oxygen fuel ratio and steam fuel ratio. 

Typical utilities, per metric ton butene-1 (80% butenes in feed) Steam + fuel, MMKcal 1.3... 

Enthalpies of water, heating steam, fuel, wet and dry synthesis gas Fuel conversion degree ... 

The cost of corrosion has already been dealt with in the first chapter. The annual cost of corrosion in the United States was estimated in 1949 to be 5 billion, 2.1% of GNP. The cost of corrosion in the United Kingdom was estimated to be 1.365 million (1971 prices). By 1975, the estimated cost of corrosion in the United States had risen to 70 billion, 4.2% of GNP. The cost of corrosion consists of the cost of replacement as well as indirect costs and may occur for any of the following reasons (i) lost production shutdown or failure (ii) maintenance (iii) compliance with environmental and consumer regulations (iv) loss of product quality in a plant owing to contamination from corrosion of the materials used to make the production line. (v) high fuel and energy costs as a result of steam, fuel, water, or compressed air leakage from corroded pipes. 

Estimation of the cost of energy inputs for the new process is difficult at the early research stage when process information is limited. One method which is useful at this stage is described by Marsden and requires only data on the number of major process operations, process throughputs and chemical heats of reaction. It enables an estimate of the total energy requirement of the process to be made and inspection of the assumed reactor conditions and expected distillation temperatures will usually enable a split into steam, fuel and electricity consumption to be made. 

The production of fertilizers requires steam, fuel for drying, and water for scrubbing of gases, trust, and dust from granulation or prilling units. 

---