Steam line, bleeding

The kiln operator selects the appropriate sehedule and adjusts the temperature and humidity as necessary by manipulation of the heating eoils (dry heat) and spray valves (steam), with occasional adjustments to the air inlet and outlet vents, which exchange hot, moist air from the kiln for cold, drier air from outside. The steam line raises and maintains the humidity while the kiln warms up. It should be used only infrequently thereafter as economy in operation depends on making maximum use of the moisture extracted from the lumber to maintain the required humidity in the kiln. As moisture evaporates the humidity rises above the schedule value and the vents open a little to bleed off some of the hot damp air. 

Dump station on each steam line from SG for two phase flow (feed and bleed) ... 

Install flame arresters in lines and vents carrying combustible vapors. Assess the requirement for double-block-and-bleed valve arrangements—where personnel are occasionally expected to enter vessels—in high pressure steam lines where isolation is needed for maintenance. 

It is decided to bleed off 0.25 kg/s of vapour from the vapour line to the second effect for use in another process. If the feed is still heated to the boiling-point of the first effect by external means, what will be the change in the steam consumption of the evaporator unit ... 

Af a(j,j is the additional boiler fuel required when the heater is ou of service, cB is the unit cost of steam in the i - 1 bleed line, and cp is the unit cost of boiler fuel (coal). These available-energy flows are calculated in the usual manner and are given in Table II and reference (6). The unit costs are obtained with exactly the same techniques discussed by Reistad and Gaggioli (2)—by applying money balances to each component (boiler, high-pressure turbine,. . . ) of the system of interest to get the dollar flows and then by the subsequent division of the appropriate available-energy flows to obtain the unit costs. 

The complete performance of an extraction turbine can be represented by a diagram such as Fig. T-75 in which the output is expressed in percentage of rated capacity and the throttle flow in percentage of that at full load without extraction. The line labeled 0% extraction at const, extr. press. represents the performance of the turbine when no steam is extracted but with the extraction valve acting to hold extraction pressure at the bleed connection. 

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