Fired heat, cost

In new plants, water should be considered as a heat transfer medium instead of oil. A decision to use water has to be made early in the design because the operating pressure will be higher. Although this will add to the cost, there will be savings in lower fire protection costs. In some plants the heat transfer oil is a bigger fire hazard than the process materials [9-1IJ. 

However, a small-diameter tube gives more pressure drop for a given flowrate through each tube and a given tube length. Of course, a larger number of parallel tubes that are shorter can be used to keep pressure drop at a reasonable level, but this increases the shell diameter of the reactor, which increases the cost. Mechanical problems also limit the minimum tube diameter. Typical tube diameter in cooled tubular reactors is 0.03 m. Typical tube diameter in a furnace-fired heated tubular reactor is 0.15 m. 

Novatec has developed two systems which can be applied to drying fillers. One is an indirect gas fired heater which can be used with any drier to improve the process economy. About 80% of the heating cost can be saved by the use of these heaters. Novatec also offers a portable drying/conveying system which conveys particulate materials through the drier and delivers them directly to the next process step. 

In the rotary kiln of cement works, clay and lime are sintered or burnt into cement clinker. The reactor is run in counterflow Primary firing heats the material to approx. 1,400 °C, secondary firing in the loading area ensures calcinations at approx. 900 °C. Approximately 3.3 GJ energy are required for production of 1 Mg cement [20]. To reduce the energy costs, which account for approx. 50 % of the production costs, substitute fuels such as old tires, used oil, paint sludges, sawdust or refuse-derived fuels are used. As much as 30 % of the total heat requirement of a plant have been covered by these secondary fuels [21], the solid residues of which are integrated into the product [19]. 

Dowtherm furnace package unit including firing. FOB cost = 110000 for heat absorbed = 280 kj/s with n = 0.61 for the range 40-2800. 

Fig. 37. TLe apparatus is stated to present the foUowiig advantages over the method of melting hy fire-heat —3, The copper is not injured by local heat, and will last for many years 2, there is little risk of burning the teUow or fat during the heating 3, the pan costs 50 per cent, less that those ordinarily used 4, the pan can be instantly checked, thus preventing the danger of boiling over 5, no risk of accidents fronx fire 6, economy of fuel. The following are the details of the apparatus ...

A more recent advance has been the introduction of the combined RF convective dryer in which RF heats the volume of the product and, by reducing the viscosity and surface tension of the water, causes liquid phase flow to the surface, at which greater part of the required energy is provided by the convective, normally gas-fired heat. These equipments are used in a range of industrial applications on particulates, three-dimensional solids, and works for which pure RF would not be cost effective. The overall energy efficiency is very high [57]. 

To carry out a simple estimate of the financial payback of a proposed installation you must divide the total installation costs by the annual savings. For example, let us suppose that you intend to replace your existing coal, calor gas or oil-fired heating system with a ground source heat pump because you live in the country and there is a large plot of grassland next to your house. The estimated cost of... 

Air preheat temperature requirements of 2250—2300 K are anticipated for natural gas-fired systems, and about 2000 K for oil or coal-fired systems (11). Use of 32—40% oxygen enrichment lowers the preheat temperature requirement to a moderate 900—1000 K, which can be attained with conventional metal-type tubular heat exchangers. Depending on the cost of oxygen, this is a viable alternative to the use of separately fired high temperature preheaters. 

Most processors of fiber-reinforced composites choose a phenol formaldehyde (phenoHc) resin because these resins are inherently fire retardant, are highly heat resistant, and are very low in cost. When exposed to flames they give off very Htde smoke and that smoke is of low immediate toxicity. PhenoHc resins (qv) are often not chosen, however, because the resole types have limited shelf stabiHty, both resole and novolac types release volatiles during their condensation cure, formaldehyde [50-00-0] emissions are possible during both handling and cure, and the polymers formed are brittle compared with other thermosetting resins. 

Flue dampers that block the flue when the burner is not firing increase the efficiency of gas-fired water heaters. These can operate electrically or thermally. Because gas-fired water heaters lose so much heat up the flue during standby periods, this can provide significant savings. These are readily available on larger water heaters used in commercial settings but haven t been applied in the residential market because of their cost. 

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