Calorific values Capital cost

Condensing boilers are now available for both gas- and oil-fired plant, the advantage of these being that the flue gases are further cooled down to below 100°C so that the latent heat available in the flue gas water vapor is recovered. The condensate has to be removed and the boiler capital cost is higher than for conventional plant. However, the boiler plant efficiency is increased to the order of 90 per cent, based upon the fuel gross calorific value. Where the flue gas exit temperatures are in excess of 200° C a further economy can be obtained by the provision of a spray recuperator in the case of gas and flue gas economizers for oil and coal. 

Tabic 3 shows the effect of the second methanation stage on product calorific value. While consumption of LI G is minimized, the capital cost is increased and Ihe overall thermal efficiency is slightly reduced. 

The calorific value of the product from hydrogasification is lower than that from single methanation, particularly with high carbon/hydrogen feedstocks because of the additional steam required. However, by adding a final metlianator. the calorific value can be increased to that obtained from double methanation, again with increased capital cost and reduced efficiency. This process (Fig. 2) is used in the first operational SNG plant in the United States at Harrison, N.J. Typical gas analyses are given in Table 4. 

Basis for Plant Design. The composition of municipal refuse is assumed as shown in Table III. The municipal refuse has the lower calorific value of ca. 1,500 Kcal/Kg. Plant size of 600 T/D is assumed. The capital investment costs, utilities, etc. were calculated using contacts with equipment vendors. Cost for repairs are assumed to be two percent of the plant construction cost per year. Unit costs of utilities and unit prices of recovered energy and material are assumed, based on the actual prices in 1979. Ash and other residues disposal cost is assumed to be 2,450 Yen/T, taking note of the representative cost data of large cities in Japan, The grant available to a municipality is assumed to pay up to fifty percent of the capital investment. The remaining investment cost must be amortized in fifteen years with the interest rate of six percent. 

Fuel Relative capital cost Relative cost of unit net heat Ash content % % volatiles % sulfur Net calorific value (kcal/kg) Relative ease of handling Level of hazard Comments... 

Given the use of the off-gas of the DMTM process for energy generation and the possibility of utilization of steam produced directly at the TPP, the efficiency of carbon use in such integrated process is expected to be close to 100%. A full use of the reaction heat and calorific value of the exhaust gas actually eliminates the two main drawbacks of the DMTM method associated with the low selectivity of methanol formation and low conversion of gas per pass. At the same time, its benefits, such as one-step nature of the process and relatively low capital and operating costs, make the DMTM-based integrated method of methanol production quite competitive compared with existing methods of production of commercial methanol. 

It is surprising to many that the method of application can have such a large effect on odour. Even with waterborne systems, incineration may still be required to reduce or remove odour. In this instance, it may not be economically viable to use waterborne systems, because solvents have calorific values which means that they can fuel or at least partially fuel an incinerator, thereby reducing the need for expensive fuel oil. It may be that a smaller incinerator can be used with waterborne systems compared to a solvent based system, with associated lower capital costs. The overall comparisons are not straightforward and all factors must be considered in the overall cost equation. 

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