US1730541A - Boiler efficiency meter - Google Patents

Description

, 8, 1929. J. M. SPITZGLASS 1,730,54f

BOILER EFFICIENCY METER Filed May 1. 1926 &

Patented Oct. 8, 1929 UNITED STATES PATENT OFFICE JACOB M. SPITZGLASS, OF CHICAGO, ILLINOIS, ASSIGNOR TO REPUBLIC" FLOW METERS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS BOILER EFFICIENCY METER Applicaticn filed. May 1, 1926. Serial No. 105,957.

My invention relates to methods for controlling apparatus for generating or using power, and one object of the invention is to provide means by which the operator may at all times be apprised of the conditions existing in the apparatus so that if he observes that any of them are at variance with those which have been predetermined as being most advantageous, they may be corrected,

thus causing the apparatus always to function with maximum efficiency even though the capacities at which it is operating change from time to time. For illustration, take the case of a steam generating plant in which fuel is employed to generate the heat. Ordinarily the demands upon the boiler will vary from time to time. My apparatus is designed to make it possible for the operator in charge of the boiler room to so control the conditions of operation as to produce maximum efficiency at the various capacities at which the boiler is called upon to operate. The steam flow, that is, the rate at which the boiler must produce steam, depends, in the case of a factory, upon the amount of power required, or in the case of a heating plant, on

' the amount of heat which must be supplied.

This factor of steam flow, therefore, while variable, is not, practically speaking, under the control of the man in charge of the boiler room but is dependent upon exigencies beyond his control, such as power or heat requirements. Consequently the steam flow or boiler capacity is the given or predetermined factor, and one purpose of the invention is to provide a method and means for keeping the operator advised as to the capacity at. which the boiler is operating and also keep him advised as to other correlative conditions or factors so that he may be able to modify them in such manner as to obtain maximum efficiency. Another object of the invention is to provide means by which the operator may readily compute the efficiency at which the boiler is operating at any given moment. Another object is to. provide means by which a permanent record of the various conditions or factors may be made and the efliciencies computed.

Boiler efiiciency is obtained in practice by determining the loss of heat due to improper combustion of fuel in the furnace and improper absorption of heat in the boiler.

In ordinary boiler room operation most of the loss is the heat carried away through the stack by the heated gases. Improper combustion (caused by feeding too much air) increases the weight of gas per pound of fuel so that more pounds are heated from room,

to stack temperature for each pound of fuel. Besides, such improper combustion causes a reduction in the furnace temperatures, which in itself reduces'the possible transfer of heat to the boiler. Improper absorption or transfer of heat to the boiler, increases the temperature of the escaping gases. The product of the two forms the so-called stack losses, which have been found in all cases to be indicative of the total loss of heat through the boiler.

Let L signify the percent loss in the boiler, and W and T the weight and temperature of. the escaping gases respectively. Then L=KWT 1 considered is the difference between the room temperature and the temperature ofthe flue gases at the .last pass in the boiler or at the base of the stack, buta scale may be readily prepared to read direct in degrees above the room temperature and T will therefore be understood as representing the difference in temperature or the rise-above room temperature.

The value of 7 cannot be obtained directly, but it has been found by experience based on. numerous tests and experiments that the per cent of carbon dioxide in the flue gases is a direct index of the amount of air used for the combustionof the fuel (it being understood, of course, that in the practical operation of a steam boiler a greater amount of air than that theoretically required for complete combustion is always supplied, such excess resulting in the proportionate reduction of the CO contents in the flue gases). Consequently the amount of CO in the gases is an index of the weight of the gases passing through the stack per pound of fuel. Hence we may write W=a function of P. (2)

That is, the Weight of gases'per pound of fuel is a function of P where P represents the percent of CO in the products of comwhere C is a constant. This substitution is close enough for practical purposes although in the actual construction of my apparatus the scale may be made according to the 1noreaccurately determ ned relation of W to P.

Combining Equations (1) and (2) we have and by calling K=CK, we have To illustrate the application of this equation; let it be assumed that a given fuel, say western bituminous screenings, having a 0 heat value of 11,000 E. t. u. per pound, re-

quires a minimum weight of 8.4: pounds of air for perfect combustion resulting in a maximum of 18.4 per cent of CO In practice, it is first necessary to obtain othe characteristics of the particular .boiler forwhich the instrument is to be used and for this purpose severaltests are run on the performance of the boiler. Let it be assumed that a test shows that when T is equal to 500 (sodegrees F., and P is equal to 10 per cent 6 With a knowledge of these conditions, we

solve for the value of K from Equation For convenience we let T represent units of temperature, 100 degrees F each. Then Thus the loss may be computed at any time by observing the temperature and the percent of CO and this formula will hold substantially true for various capacities or rates of steam flow ofthe particular installation under observation.

To give a concrete illustration of the method and operation of the apparatus, reference may be had to the accompanying diagram in which a record strip a is causedto travel beneath styluses b, 0, and (Z. In the present case, the strip is assumed to travel downward and as mechanism for causing record strips to travel are Well known such mechanism need not be described here. The sheet has cross rulings e which indicate the various hours of the day, these hours being denoted by appropriate markings 7 here shown in a column at the left margin of the strips The strip .is divided into three sections arrangedside by side, the section 9 at the left representing steam flow, the section I), at the middle representing the percent of ()O and the section at the right represent. ing the stack temperature, or more properly speaking, the difference between the ,stack ten'iperature and the temperature of the boiler room.

The steam flow section 9 has vertical rulings or ordinates is spaced equally and TBPIQ. senting units of steam flow. These units are indicated by a row of numerals m which in the present illustration progress from left to right in increments of ten. These units are selected arbitrarily and the operator may, if he wishes, translate these units intoactual pounds of steam generated per hour.

The CO section It has vertical rulings or ordinates a spaced equally and representing the percentage of CO These percentages are indicated by a row of numerals j) which in the present illustration progress from left to right in increments of two.

The stack temperature section at the right has vertical rulings 7 that are spaced equally and represent stack temperatures. These temperatures are indicated by a row of numerals s which progress from lift to right in increments of one hundred.

Said rows m, p and s of numerals may be printed directly upon the record strip at intervals or they may be markedon a stationary portion of the apparatus in suchposi'tionthat stacktemperature.

the vertical lines or ordinates k, n, 1' will pass under them in uxtaposition thereto.

The styluses b, 0, (Z, may be supported and operated by any appropriate type of mechanism so long as they are moved in accordance with the variation of the factors which they represent. In the present case, which is largely diagrammatic, the styluses are supported upon rods t slidable upon a guide bar a and controlled by rods w, 11 a which are moved by suitable devices in accordance with the variable factors of steam flow, percentage of CO and stack temperature. For example, the rod 02 may be operated by a steam flow meter, which is a known instrument, and the rod 3 may be operated by a gas analyzer which will indicate the percentage of (30,, such instruments also being known. The rod :4 may be operated by a pyrometerwhich is also a known instrument.

The styluses b, 0, and d trace graphs B, C, D respectively on the record strip and from the considerations above stated it will be evident that the loss will be least and the efficiency greatest in proportion as the graph G moves towaird the right and the graph D moves toward the left. Thus by merely noting the by noting the distance between the two graphs.

But my device in its developed form goes further than this and is so constructed that the observer may by making a simple multiplication of two numerals calculate the efliciency at which the boiler is operating. The mechanism more intimately concerned with this characteristic will now be described.

The bridge 1) is mounted in front of the record strip and held stationary by screws Q) or other suitable fastening means. In the form illustrated, it consists of glass, celluloid or other transparent material, although this is not essential. On this bridge is juxtaposition to scale 8 there is marked a scale s in which the numerals represent units of temperature. The integers in the present illustration run from 0 to 9, progress from left to right, and each unit represents 100 degrees of This scale represents the temperature factor T of Equation No. (3) and it will be noted that it progresses in the same direction as the scale s, and that the zero point is at the line R.

On said bridge 1: in juxtaposition to scale p there is marked a scale p in which the numerals progress in the opposite direction from scale 39. These numerals are marked to represent the values of in Equation No.

represents the WVfactor, although as this is determined according to my method from the CO factor in the flue gases, in the parlance of the boiler room the scale p is more aptto be referred to as the CO factor and is so marked in the diagram. In the form illustrated scale p runs from i to 18 with the graduations gradually decreasing in extent. toward the higher portion of the scale.

The scales 7), s as stated are calibrated according to Equation No. (.3) so that by multiplying the readings on thesetwo scales together the product will give'the percent loss in the efficiency of the boiler.v The result is that my instrument provides means by which the heat losses may be obtained by simply multiplying together the readings on the two scales s, and the efficiency may readily be obtained by subtracting this loss from unity or 100%.

From the foregoing it will be evident that the device illustrated constitutes a boiler efficiency meter and embodies in a single instrument means for indicating or recording three variable factors, viz steam flow, stack temperature and percentage of the carbon dioxide in the stack gases, the later factor in my device being interpretable in terms of the weight of flue gases per pound of fuel. Thus the operator may be appraised at all times of the actual conditions of operation, and he is afforded simple and reliable means by which he may, by an easy computation, calculate the efficiency at which the boiler is operating.

According to the arrangement illustrated, the graphs C and D approach each other as the efficiency increases and recede from each other as it decreases, but it will be understood, of course, that this arrangement may be reversed without departing from the spirit of the invention, for by reversing the scales p, s and reversing the movement of the indicators 0, d the efliciency will be greatest when the graphs 0, D are farthest apart and, least when they are closest together. The present arrangement, however, is preferred, for according to it the zero points may be located on a common line (in the present case line B) and the instrument will present a more graphic and readily understood picture to the mind of the operator.

Having thus described my invention what I claim as new and desire to secure by Let ters Patent is:

1. The method of determining a factor ap proximately proportional to the loss of efliciency in a furnace, which consists in measuring the percentage of carbon dioxide in the flue gases and their temperature on reaching the stack, determining the temperature of the air in the furnace room and multiplying the difference between these temperatures by the reciprocal of the said carbon dioxide percentage. a

2. The method of determining a factor approximately proportional to the loss'of eificiency in a furnace, comprising obtaining an index of the state of the flue gases by measur ing the percentage of carbon dioxide therein, and determining the temperature of the flue gases in the stack, determining the temperature of the air supplied to the furnace, and multiplying the difierence between these temperatures by the reciprocal of the said carbon dioxide percentage.

In Witness whereof, I have hereunto subscribed my name. 7

JACOB M. SPITZGLASS.

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