Abstract: Gas-phase methods and systems for reducing NOx emissions and other contaminants in exhaust gases, and industrial processes using the same, are disclosed. In accordance with the present invention, hydrocarbon(s) autoignite and autothermally heat an exhaust gas from an industrial process so that NH.sub.3, HNCO or a combination thereof are effective for selectively reducing NOx autocatalytically. Preferably, the reduction of NOx is initiated/driven by the autoignition of hydrocarbon(s) in the exhaust gas. Within the temperature range of about 900-1600.degree. F., the introduced hydrocarbon(s) autoignite spontaneously under fuel-lean conditions of about 2-18% O.sub.2 in the exhaust gas. Once ignited, the reactions proceed autocatalytically, heating the exhaust gas autothermally. Under some conditions, a blue chemiluminescence may be visible.

Abstract: A method is provided for abating acidic contaminants, such as sulfur dioxide and hydrogen chloride, in exhaust gases while minimizing the formation of visible plumes of ammonium salts proximate to the outlet of the exhaust stack by injecting a spray of an alkaline liquid, such as sodium hydroxide or potassium hydroxide, into the contaminated exhaust gases wherein the pH of the alkaline liquid is high enough, i.e. greater than a pH of about 11, so that the acidic contaminants preferentially react with the alkaline liquid rather than the ammonia in the gases, thereby minimizing formation of visible plumes of ammonium salts.

Abstract: Formation of calcium sulfite in a desulfurization column for desulfurizing flue gas is prevented by maintaining the pH of the sorption liquid in the column in the range of 5.5-7.0 and the chemical oxygen demand of the sorption liquid below an upper value determined by the concentration of magnesium sulfate. The upper value of the chemical oxygen demand of the sorption liquid can be controlled by maintaining the quantity of magnesium sulfate in an oxidization vessel arranged downstream of the desulfurization column. The oxidized liquid discharged from the oxidization vessel is neutralized in a double composition vessel, and the thus-obtained slurry is returned directly to the desulfurization column. By preventing formation of calcium sulfite, high-quality gypsum is formed in the double composition vessel.

Abstract: There is provided a method for flue gas desulfurization which is capable of conducting minute control of oxidation and which is capable of maintaining the concentration of sulfurous acid in an absorbent liquid within a proper range in a highly reliable and efficient manner, even in the case where an abrupt change occurs in the operational conditions of the system. In the method for controlling the oxidation in flue gas desulfurization, the value of proportional sensitivity K in the feed back control process, which is based primarily on the oxidation-reduction potential, is increased depending on the deviation .epsilon. in a region where the detected oxidation reduction potential value PN is below the target oxidation reduction potential value SN in correspondence with the characteristic change of the oxidation-reduction potential against the concentration of sulfurous acid.

Abstract: A method for removing nitrogen oxides out of the exhaust gas from a combustion apparatus is provided by reducing the nitrogen oxides with injected ammonia or urea to produce nitrogen and water. The method further includes the provision of at least one, sensor placed downstream from the nitrogen oxides removal step for measuring the concentration of the residual ammonia and nitrogen oxides in the exhaust gas after the nitrogen oxides removal step. The method also further includes the provision of a controller for controlling the rate that the ammonia and/or urea is injected into the exhaust gas so that the rate of ammonia and/or urea injection is repeatedly increased and decreased in response to the signal generated by the sensor about a reference value plus the average of the increased and reduced rates of ammonia and urea injection.

Abstract: Gas-phase methods and systems for reducing NOx emissions and other contaminants in exhaust gases, and industrial processes using the same, are disclosed. In accordance with the present invention, hydrocarbon(s) autoignite and autothermally heat an exhaust gas from an industrial process so that NH.sub.3, HNCO or a combination thereof are effective for selectively reducing NOx autocatalytically. Preferably, the reduction of NOx is initiated/driven by the autoignition of hydrocarbon(s) in the exhaust gas. Within the temperature range of about 900-1600.degree. F., the introduced hydrocarbon(s) autoignite spontaneously under fuel-lean conditions of about 2-18% O.sub.2 in the exhaust gas. Once ignited, the reactions proceed autocatalytically, heating the exhaust gas autothermally.

Abstract: A wet-type flue gas desulfurization method and plant making use of a solid desulfurizing agent in which exhaust gas exhausted from a combustion apparatus such as a boiler is brought into contact with absorbing liquid to absorb sulfur oxide from the exhaust gas into the absorbing liquid followed by neutralization of the absorbing liquid containing the sulfur oxide thus absorbed. The solid desulfurizing agent is selectively retained in an absorbing liquid neutralizing zone and the absorbing liquid, containing water as a main constituent and solid products formed from the absorbed sulfur oxide, is selectively removed from the neutralizing zone. In the neutralizing zone the upward flow of the absorbing liquid, optionally augmented by an upward flow of air or water, forms a fluidized bed of limestone particles, thereby preventing coating of the limestone by gypsum and thereby retaining reactivity of limestone.

Abstract: The process calculates the amount of silica and oxidizing agent to use in a refining process for metallurgical-grade silicon. The calculation for silica takes into account (1) the aluminum content of the previous batch of refined silicon; (2) the calcium content of the previous batch of refined silicon; (3) the trend in the aluminum content of the unrefined silicon; and (4) the age of the ladle used for refining. The process then calculates the amount of silica based on a predetermined minimum amount of silica to add, a predetermined maximum amount of silica to add and the amount of silica added to the previous batch of refined silicon. The calculation for oxidizing agent is based on (1) the aluminum content of the previous batch of refilled silicon; (2) the calcium content of the previous batch of refined silicon; and (3) the age of the ladle.

Abstract: A method of controlling the oxidation of sulfites in a flue gas desulfurization process involves treating the exhaust gas with an absorbing fluid containing a calcium compound and controlling the oxidation of sulfites by regulating oxygen flow into the absorbing fluid. Oxygen flow is controlled by continuously monitoring the oxidation-reduction potential (ORP) of the absorbing fluid relative to the same fluid in a completely oxidized state using a detector with a plurality of fluid tanks, one of which functions as a reference tank at any particular time. The fully oxidized reference tank is periodically switched, reducing adherence of oxidizing substances to the ORP electrodes, resulting in more accurate measurements and reduced chemical oxygen demand of the waste water.

Abstract: Apparatus and method for remediation of particulate matter and gaseous pollutants entrained in flue gases. The flue gases, having a pre-determined moisture content, are mixed with sorbent material and forced through an induct venturi equipped with a mixing impeller. Downstream, the reaction products are removed from the gas stream and collected for use as construction material. The vented gas stream is monitored for specific pollutants and the amount of sorbent material introduced into the system can be automated in response to reading obtained. Additionally, the gas stream can pass through a bag house or cyclone wherein the bags are impregnated with materials specific to the pollutants carried in the stream.

Abstract: Sulfur dioxide is removed from flue gas by scrubbing with sea water and aeration of the sump to convert the removed sulfur dioxide into bisulfate with neutralization in a reaction basin subsequently forming sulfate. The neutralization is carried out by the treatment of sea water and a pH of 4 to 5 and preferably 4.15 to 4.5 is maintained in the liquid phase removed from the sump by controlled recycling of the sump liquid to the absorption zone or addition of further quantities of sea water to the column.

Abstract: This invention relates to a process for controlling the temperature of a fluidized bed reactor in the manufacture of titanium tetrachloride, wherein an exhaust gas stream comprising carbonyl sulfide, sulfur dioxide, carbon monoxide, carbon dioxide, and chlorine is formed. In the process, the exhaust gas stream is first analyzed to determine the analyzed concentration of carbonyl sulfide (or concentration ratio of carbonyl sulfide to sulfur dioxide), the desired concentration of carbonyl sulfide (or concentration ratio of carbonyl sulfide to sulfur dioxide) in the exhaust gas stream is determined, and the difference between the analyzed concentration of carbonyl sulfide (or concentration ratio of carbonyl sulfide to sulfur dioxide) and the desired concentration of carbonyl sulfide (or concentration ratio of carbonyl sulfide to sulfur dioxide) in the exhaust gas stream is then calculated.

Abstract: An integrated, at least substantially self-contained and at least substantially closed-loop combustion process and system for the control of gaseous, ionic, colloidal, liquid or particulate matter, particularly noxious contaminants contained in the off-gas of a combustion unit, the system comprising a:(a) chemical treatment chamber;(b) a reactant source communicating with the treatment chamber and adapted to provide reactant chemicals in contact with the off-gas;(c) a reactant chemical selector associated with the reactant source;(d) a control device communicating with the off-gas within the combustion system for analyzing the off-gas and actuating the selector in response to the analysis to provide reactant chemicals for contact with the off-gas;(e) an expansion chamber communicating with the treatment chamber and adapted to provide a reduced pressure region of treated off-gas received from the treatment chamber means;(f) an exhaust port in the expansion chamber for discharging the off-gas, and(g) cooling me

Abstract: In a flue gas desulfurization process wherein, when sulfur oxide-containing exhaust gas is treated with an absorbing solution containing a calcium compound, an oxygen-containing gas is passed through the absorbing solution and the flow rate of the oxygen-containing gas is controlled by detecting the oxidation-reduction potential of the absorbing solution continuously, an oxidation controlling method which comprises detecting a first deviation signal between the oxidation-reduction potential of the absorbing solution and the oxidation-reduction potential of the absorbing solution in a completely oxidized state and controlling the flow rate of the oxygen-containing gas in response to a second deviation signal between the first deviation signal and a preset oxidation-reduction potential deviation value.

Abstract: A method for reducing gaseous emission of halogen compounds in a fluidized bed reactor in which the fine particles entrained in flue gases are used to form a temporary layer of particles on the baghouse filter to absorb halogen gases.

Abstract: A treatment solution which is stored in a treatment vessel is supplied to a mixing vessel and a simple fluoride solution is supplied into the mixing vessel from a simple fluoride supply vessel to convert aluminum salt of complex hydrofluoric acid which is contained in the treatment solution to complex hydrofluoric acid. Concentration of HF remaining in the mixed solution is measured with a metal silicon electrode meter provided in an HF concentration measuring part, so that a control signal is transmitted from a control unit to a pump and a flow control part on the basis of the data as obtained. The simple fluoride solution is supplied from the simple fluoride supply vessel to the treatment solution which is stored in the treatment vessel to return the activity of the treatment solution stored in the treatment vessel and to control the same in a prescribed range.

Abstract: There is disclosed an improved process for the preparation of phosphorus trichloride wherein elemental phosphorus is caused to react with chlorine. The improvement comprises continuous, high speed analysis of the contents of the reactor whereby the reaction is controlled to produce less phosphorus pentachloride and other by-products. The analysis is performed by a laser Raman spectrometer associated with an optrode having a remotely located probe head and a circulating sampling system to continuously provide fresh sample to the probe head continuously. Also disclosed is apparatus for the automatic control of the reaction by control of the reactant feed to the reactor in response to the on-line, continuous analysis of the reactor contents.

Abstract: A carbon black process control system measures input variables such as feedstock flow rate, feedstock quality, air flow rate, air humidity, air temperature, fuel flow rate, fuel quality, and/or potassium additive solution flow rate at spaced intervals while the carbon black reactor is operating. Then, at spaced intervals in time one or more output variables of the carbon black, such as iodine number and/or DBP, are predicted in accordance with a prediction algorithm based on the values of the measured input variables. Then, at spaced intervals in time the predicted values of the output variables, such as iodine number and/or DBP, are averaged. Based on the average values of the predicted output variables, one or more input variables are then adjusted to achieve goal values of the predicted output variables, and thus obtain carbon black of substantially consistent quality.

Abstract: An improved acid gas recovery system is provided which has particular application in reducing the incidence of sulfide and other acid gas excursions. The present invention addresses the disadvantages of prior absorption techniques by closely monitoring and maintaining a reaction zone temperature profile within a contactor to improve and control the reaction between acid gas components and the aqueous amine absorbent. The temperature profile is maintained by frequently adjusting relative flow rates of the feed gas and lean amine in the process which in turn reduces the incidence of excursions.

Abstract: Membrane or pressure swing adsorption systems are used for air separation, with the crude nitrogen stream obtained thereby passing to a catalytic combustion system for reaction of residual oxygen with hydrogen to produce a high purity nitrogen product. Excess hydrogen in the nitrogen product is minimized by controlling the amount of hydrogen employed based on the instantaneous crude nitrogen flow and purity, and adjusting hydrogen ingestion in response to nitrogen product purity feedback. Plant flow rate tracking control limits maximum rates of flow change to ensure stable operation.

Abstract: A control system for controlling the operation of an apparatus for growing tubular crystalline bodies. The control system comprises a weight sensor for measuring the weight of the crystal, a length sensor for measuring the length of the crystal, a pressure sensor for measuring the pressure inside the crystal, and a controller coupled to the weight, length and pressure sensors for controlling the operation of the crystal growing apparatus. The controller is coupled to the die heater of the apparatus for controlling the temperature of melt contained in the crucible of the apparatus based on the outputs of the weight, length and pressure sensors. To ensure the wall of the tubular crystalline body is maintained at a substantially uniform thickness, precise measurement of the weight of the body must be made. Compensation is provided by this invention for weight measurement errors that are created by pressure fluctations within the tubular crystalline body.

Abstract: The crystallization of a crystalline silicate product from an crystallization mixture is monitored by measuring the specific electrical conductivity of the mixture. The crystallization of metallosilicates, such as aluminosilicate zeolites, may be monitored in this way. Measurement of the electrical conductivity of the crystallization mixture may be carried out on line in a batch or continuous crystallization process. In a continuous process the conductivity may be monitored and used to control the crystallization process parameters in order to achieve a desired degree of crystallinity in the product.

Abstract: A continuous method for preparing silane and a co-product by reacting a metal hydride such as NaAlH.sub.4 with a silicon halide such as SiF.sub.4. The method involves a reactor loop comprising a primary reactor, a secondary reactor and a separation zone. Most of the metal hydride is reacted in the first reactor to which it is added in a substantially constant rate. The remainder of the hydride is reacted in the secondary reactor, in which all or substantially all of the silicon halide is added. The rate of silicon halide addition is governed by feed back from the reaction in the secondary reactor, (.rarw.T so that stoichiometric or substantially stoichiometric operation is achieved. This conserves resources, provides improved co-product and reduces costs.

Abstract: A process for the preparation of a crystalline sheet-type alkali metal silicate is described, in which an aqueous solution of an alkali metal silicate or a suspension of an amorphous alkali metal silica having a molar ratio M.sub.2 O (unneutralized)/SiO.sub.2, where M represents an alkali metal, of 0.05:1 to 0.8:1 is allowed to react at temperatures of 70.degree. to 250.degree. C. until the sheet-type alkali metal silicate crystallizes out. After the beginning of crystallization, an acidic compound is added in an amount such that an M.sub.2 O (unneutralized)/SiO.sub.2 ratio of 0.05:1 to 0.8:1 is constantly maintained in the mother liquor of a filtered sample. However, at least an amount corresponding to 5 milliequivalents of H.sup.+ per mole of SiO.sub.2 in the alkali metal silicate used is added. The use of seed crystals of the desired sheet silicate is advantageous.

Abstract: In a heat exchange unit that recovers waste heat from carbon black smoke by preheating oxygen-containing gas such as air being passed to a carbon black producing reactor, a control loop is provided that automatically diverts the oxygen-containing gas being preheated through a by-pass line if the temperature of the effluent smoke being removed from the heat exchange is below a minimum temperature value in order to minimize the deposition of carbon on the heat exchange surfaces in said heat exchange zone.

Abstract: In order to prevent burn-off of a radial feedstock nozzle in a carbon black reactor, resulting when the feedstock stopped flowing through the nozzle, a preselected minimum temperature of the feedstock tube actuates a mechanism to withdraw the feedstock from the hot zone of the reactor.

Abstract: Methods and apparatus adaptable to continuous production of hydrogen sulfide by chemical reaction of sulfur with a gaseous sulfur-reducing reactant selected from methane or other hydrocarbons, hydrogen, carbon-containing compounds such as carbon disulfide, gases with high CO contents, e.g. from gasification of coal, or mixtures of such gases are provided utilizing a separately-fired sulfur heater to vaporize liquid sulfur feedstock. Adding steam with the sulfur reduces the temperature level requirements of the sulfur vapors and provides H.sub.2 and O.sub.2 for the hydrolysis reactions. Control of the temperature of the sulfur vapors and steam delivered into the system through the sulfur vaporizer is used to modulate sulfiding reaction temperatures. A major portion of the steam is introduced with the sulfur vapors; a minor portion of the steam can be added with the feedstock reductant gas to assist in heat recovery from the reaction product gases and to facilitate standby conditions.

Abstract: There is provided a method for converting sulfur dioxide in an exhaust gas to sulfur, which comprises the reduction step of reducing sulfur dioxide in an exhaust gas containing water vapor to hydrogen sulfide in the presence of carbon, a part of the exhaust gas is caused to bypass the reduction step and the remainder of the exhaust gas is fed to the reduction step to convert sulfur dioxide in the exhaust gas to hydrogen sulfide; the gas from the reduction step is mixed with the exhaust gas bypassing the reduction step while controlling the amount of the bypassing exhaust gas so that the ratio of hydrogen sulfide to sulfur dioxide in the mixed gas is maintained at 2; the mixed gas is fed to the Claus reaction step; and the Claus reaction step of reacting hydrogen sulfide formed at the reduction step with sulfur dioxide to convert hydrogen sulfide to sulfur.

Abstract: Methods and apparatus adaptable to continuous production of hydrogen sulfide from chemical reaction of sulfur with various gaseous sulfur-reducing reactants selected from hydrocarbons, carbon monoxide, carbon-containing compounds such as carbon disulfide, hydrogen, of mixtures of such gases are provided utilizing a fired process sulfur heater to vaporize liquid sulfur feed stock.Control of the temperature of the sulfur vapors and the amount of liquid sulfur feed are used to modulate sulfiding reaction temperatures.Viscosity of the liquid sulfur feed stock is modified by contact with product gases in order to facilitate flow rate control as liquid sulfur is pumped into the sulfur vaporizer where its temperature increases above about 300.degree. F.Steam for hydrolysis purposes is introduced with the sulfur vapors, to augment temperature modulation of the sulfiding reactions, and/or with the reductant gas to assist in heat recovery from the reaction product gases.

Abstract: A continuous process with feedback control is disclosed for the soda ash digestion of tungsten concentrates in which a slurry of the concentrate in an aqueous sodium carbonate solution is digested in an autoclave at a temperature of at least about 180.degree. C. to provide a pregnant solution of WO.sub.3. High dissolution efficiency is maintained during digestion by continuously monitoring the pregnant solution which includes determining the specific gravity and the Na.sub.2 CO.sub.3 concentration of the pregnant liquor from which feedback signals are produced which are used to control the amount of Na.sub.2 CO.sub.3 and H.sub.2 O fed to the slurry in accordance with the digestion conditions predetermined to provide the desired dissolution efficiency.

Abstract: In a carbon black manufacturing process in which an off-specification rerun carbon black is mixed with the carbon black flowing from a carbon black reactor to produce a combined carbon black stream, method and apparatus is provided for controlling the carbon black process so as to insure that the combined carbon black stream will meet predetermined specifications. The feed flow to the carbon black reactor is controlled in response to a comparison of a prediction of the actual surface area of the combined carbon black stream with the desired surface area of the combined carbon black stream so as to provide a combined carbon black stream made up of carbon black particles which have a desired surface area.

Abstract: Control of the synthesis loop pressure of an ammonia plant is accomplished by automatically changing the purge rate of the recycle gas to maintain optimum synthesis loop pressure. The control logic of this invention allows compressor speed to be set at a constant value and suction pressure to the first stage of the synthesis loop compressor to be maintained by changing the purge rate of the recycle gas. This allows the synthesis loop pressure to seek the highest possible value at the given feed rates of the synthesis gas and compressor speed assuring optimum compressor loading.If the feed rate of synthesis gas is low, additional control is achieved by using the synthesis loop pressure signal or the concentration of inerts signal to vary the compressor speed.

Abstract: In a carbon black manufacturing process a method is provided whereby the off-gas from at least one carbon black manufacturing process is utilized both to lower the temperature of the hot combustion gases and to provide some heat to the hot combustion gases by being burned in the combustion tunnel of a carbon black reactor. A portion of the off-gas is utilized while still holding the total volume of the hot combustion gases substantially constant at a preselected substantially constant temperature to insure a substantially constant quality of carbon black.

Abstract: A waste flue gas cleaning method and an apparatus for practicing said method, in which a reactant solution is sprayed into a waste flue gas introduced into a spray tower, whereby a toxic component in the flue gas is caused to be absorbed in and react with the droplets of the sprayed reactant solution, and the water contained in the droplets is vaporized and the reaction products are dried into solid particles by the sensible heat of said flue gas. A series of the above operation is accomplished within the spray tower while maintaining the outlet gas temperature always above the dew point of the flue gas, and the solid particles of the reaction products are removed from the flue gas by an after dust collector.

Abstract: Control of the temperature of an ammonia synthesis reactor is accomplished so as to reduce temperature oscillations throughout the reactor. This allows the ammonia synthesis reactor to be operated close to the lowest stable operating temperature which results in optimal reactor performance. The temperature of the effluent flowing from the ammonia synthesis reactor is monitored to detect the presence of thermal waves. The temperature of the effluent flowing from the synthesis reactor is utilized to generate a correction term which is utilized in temperature control for the ammonia synthesis reactor to stabilize the operation of the ammonia synthesis reactor.

Abstract: In a carbon black manufacturing process in which a carbon black dryer is utilized to produce a product carbon black having a specified dryness, method and apparatus is provided for controlling the flow of fuel to the carbon black dryer so as to insure that the dryness of the carbon black product will meet predetermined specifications. Feedforward, predictive control of the flow rate of the fuel to the carbon black dryer is utilized to compensate for changes in the flow rate of wet carbon black or for changes in the moisture content of the wet carbon black. In this manner, the dryness of the carbon black product is maintained at a predetermined specification even though process variations may occur.

Abstract: In a carbon black manufacturing process in which an off-specification rerun carbon black is mixed with the carbon black flowing from a carbon black reactor to produce a combined carbon black stream, method and apparatus is provided for controlling the carbon black process so as to insure that the combined carbon black stream will meet predetermined specifications. The feed flow to the carbon black reactor is controlled in response to a comparison of a prediction of the actual surface area of the combined carbon black stream with the desired surface area of the combined carbon black stream so as to provide a combined carbon black stream made up of carbon black particles which have a desired surface area.

Abstract: A method and apparatus for producing carbon black under fine-tuned conditions which comprises measuring a property of the black produced in a tangential introduction of hot gases to produce a vortex operation and adjusting introduction of the hot gases and/or the make oil or gas responsive to said property until it has a desired value. In one embodiment, the adjustment is made manually. In another embodiment, it can be made by a computerized operation. The point of introduction of hot gases can be adjusted by providing at least one movable orifice-carrying element in the conduit supplying the hot combustion gases. The discharge end of the make oil or gas supply pipe can also be relocated according to the measured property.

Abstract: The invention relates to a computerized process and apparatus for automatically regulating the power, feed rate and electrode position of hollow or solid electrodes in submerged arc electric furnaces used for the production of quality-controlled metallurgical products such as calcium carbide.

Abstract: A method for sampling and controlling the addition of suspended gases, liquids and solids in a control stream to a process stream is disclosed wherein the surface area of the suspended material acts as the determining feature for control of the process. The measured surface area is compared with a preselected surface area to control the addition of the suspended material. This method is particularly useful for the control of particulate seed material to the process stream in the Bayer process for the production of alumina. The method is also broadly applicable to physical and/or chemical control means in an analytical scheme for controlling and monitoring any process.

Abstract: Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. The flow rate of a feed stream containing hydrogen sulfide to a tail gas cleanup process is also manipulated utilizing feedforward and feedback control to maintain the hydrogen sulfide and sulfur dioxide concentrations in the gas stream from the tail gas cleanup process at acceptable levels to avoid environmental polution.

Abstract: Carbon black is produced by heating a carbonaceous feed material to an elevated temperature to decompose the feed material to produce carbon black. A sample of the effluent from the reactor is passed as a suspension of carbon black particles in a gas into an optical cell. A beam of light is directed into the cell, and scattered light is measured at two different locations. A signal representative of the ratio of the two measured scattered light intensities is employed to control the introduction into the reactor of an alkali metal which controls the structure of the carbon black produced.

Abstract: A control system for controlling the operation of an apparatus for growing tubular crystalline bodies. The control system comprises a weight sensor for measuring the weight of the crystal, a length sensor for measuring the length of the crystal, a pressure sensor for measuring the pressure inside the crystal, and a controller coupled to the weight, length and pressure sensors for controlling the operation of the crystal growing apparatus. The controller is coupled to the die heater of the apparatus for controlling the temperature of melt contained in the crucible of the apparatus based on the outputs of the weight, length and pressure sensors. To ensure the wall of the tubular crystalline body is maintained at a substantially uniform thickness, precise measurement of the weight of the body must be made. Compensation is provided by this invention for weight measurement errors that are created by pressure fluctuations within the tubular crystalline body.