DE102020002085A1 - Self-correcting program control for the production of a cryogenic-mechanical acting blasting agent, while maintaining an effective energy balance - Google Patents

Abstract

The invention relates to a control system that corrects itself at given parameters for the production of a low-residue / residue-free blasting agent based on water ice, the droplet size being determined by the combination of different nozzles, which in their entirety require a certain flow pressure, which at production-related deviations are kept constant by the control system and the speed of fall is delayed and swirled in the individual flow channels by countercurrents that can be regulated in their intensity, while at the same time the partially frozen drops of different sizes are sprayed in a mixing area with water and nitrogen to form further layers of ice, whereby the amount of nitrogen introduced is dosed, in order to maintain the energy balance, depending on the amount of water introduced at the same time.

Description

The invention relates to a self-correcting control for the production of a low-residue / residue-free blasting agent on the basis of water ice in falling speed delayed by controllable countercurrents in the individual flow channels, of different sizes and with one or more additional layers of water , with a nitrogen consumption dependent on the water throughput while maintaining a constant energy balance.

A large number of methods for cleaning by blasting with solid abrasives are known. In these largely mechanical processes, different blasting media such as glass beads, slag, sand or salts are used, which are blown onto the surface to be cleaned with water or compressed air. In addition to the purely mechanical processes, thermal processes are also used, which are referred to as cold blasting processes. The blasting agent used is primarily CO ₂ dry ice, which evaporates as a gas after blasting. The disadvantage here is the low level of aggressiveness of the abrasive

In DE 103 09 191 A1 describes a device for dry ice blasting with a mixture of compressed air and dry ice for cleaning surfaces. The brittleness of the CO2 particles has proven to be a disadvantage. Due to the brittleness, approx. 70% of the amount of blasting media is lost unused or has a negative effect due to the cooling of the work area. With the use of shredded CO ₂ pellets, the hit rate is increased and the CO2 particles used are better used. The formation of condensation and the associated formation of ice in the vicinity of the cleaning area have proven to be disadvantageous.

the end WO 2003 101667 A1 it is known that CO ₂ pellets are used as a solid blasting agent for cleaning surfaces. The CO ₂ pellets act as a soft, not very abrasive blasting agent, which means that there is no damage to the surface to be cleaned. Due to the temperature of approx. -78 ° C of the CO ₂ pellets, a thermal voltage is created between the contamination and the surface of the component to be cleaned, which leads to the contamination being detached (cryogenic effect). CO2 particles and compressed air are used as energy sources.

The disadvantage of cleaning with CO ₂ as a blasting agent, however, is that only a slight abrasive effect is recorded. This low level of abrasiveness restricts the area of application for this cleaning technology.

DE 102015209994 A1 describes a method and an apparatus for cleaning jet engines with solid dry ice and water ice. The disadvantage here is that commercially available crash ice with a temperature of approx. - 12 ° C is used, which therefore has only a low level of hardness and a film of water is created when the required comminution is carried out, which has a negative impact on cleaning performance.

In DE 10 2009 027 974 B4 , DE 10 2004 057 665 A1 and DE 20 2010 000 713 U1 Devices for comminuting the CO ₂ pellet are described in which the dry ice particles are mechanically comminuted and introduced into the air flow with the aid of metering units or according to the injector principle.

In WO 2015/074765 A1 different possibilities for the production of water ice are described. The disadvantage here is that the water ice has to be crushed again, whereby the pressure required for crushing creates a film of water which leads to the small water particles freezing together again or contact with the ambient air cannot be avoided. A cylinder is also described which makes it possible to produce water ice particles of different sizes through different nozzle sizes. The relatively rigid cooling by spraying in or releasing an unregulated amount of liquid nitrogen, with which a cold gas atmosphere is created and the sprayed water droplets are to be cooled, has proven to be a disadvantage. A relatively stationary gas atmosphere is formed around the water droplets or around the partially frozen water droplets, which has a nagative effect on further cooling. The manufacturing process has proven to be a further disadvantage. The production cannot be carried out continuously, but must be interrupted after a certain time so that the water ice produced can be removed.

In DE 10 2010 020 618 A1 describes a method for producing CO ₂ pellets or CO ₂ particles with increased mechanical hardness and abrasiveness, in which water ice particles can be produced by adding water. The disadvantage of this is that the size of the water ice particles cannot be influenced.

In scripture DE 34 34 163 A1 water is added to the CO2 snow created when the liquid CO ₂ relaxes, so that additional water snow is created. This mixture is pelletized and blown onto the surface to be cleaned with a jet of water or compressed air. The resulting mixture of blasting media is only slightly aggressive, as the water ice that forms is only _{cooled to the temperature of the CO 2} snow.

DE 35 05 675 A1 describes a method for removing surfaces, in which prefabricated water ice is mixed with a water jet. The water ice can also be formed by ice-forming germs within the water jet. The disadvantage of this method is that there is no cryogenic effect, but only mechanical abrasion by the water ice particles; but this is relatively low, as the water ice particles only have a temperature of max. - 10 ° C and are heated by the water

For an effective use of the CO2 blasting technology, a temperature difference is required between the contamination to be removed and the substrate. The contamination is _{cooled by the CO 2} pellets and the required temperature difference or thermal voltage is created. A disadvantage of the CO ₂ -Strahltechnik the low abrasiveness of CO ₂ pellets has been found.

In DE 100 10 012 A1 and DE 201 15 013 U1 _{CO 2} pellets are added to the compressed air flow and an additional blasting agent that is solid at room temperature is added to increase the abrasiveness. The disadvantage here, however, is that some of the solid blasting media added remains in the system or the formation of dust cannot be avoided. In addition, the low constancy of the quantitative ratio between the CO ₂ blasting agent and the additional blasting agent is disadvantageous.

The end ( 1 ) A. Momber "Handbook for the surface treatment of concrete" is known that the hardness of the water ice is temperature-dependent. The hardness of the water ice is inversely proportional to its temperature. This means that as the temperature decreases, the hardness of the water ice increases. For example, water ice with a temperature of -10 ° C has a Mohs hardness of 2, comparable to plaster of paris. In comparison, water ice has a Mohs hardness of 6 - 7 at a temperature of - 100 ° C.

Various technologies for the production of water ice are known (e.g. (2) company publications from ZIEGRA, ”or (3) company documents from Kälte Berlin). The water ice produced is mainly used and has been used for cooling in the food industry a temperature down to - 15 ° C. The water ice is manufactured and sold in blocks, as slices, as nuggats in different sizes or as crash ice. During experiments, the inventor recognized that the further processing of commercially available water ice, with initial temperatures down to -15 ° C, for example by further cooling and crushing, did not bring the hoped-for success, since the necessary crushing to obtain a material that can be jetted was caused by the The pressure to be applied creates a thin layer of water, which causes the crushed ice particles to freeze together immediately.

The contact of the water ice with the ambient air during filling after production and when transferring to the blasting device has proven to be a further disadvantage. When it comes into contact with the surrounding air, condensate is formed immediately, which leads to re-freezing.

In ( 4th ) "Low-temperature water ice blasting (TWS) basic investigation into the applicability of cryogenic water ice particles for deburring blasting" (Mathias Petzold, Shaker Verlag 2014) describes a device for the production of water ice by finely atomizing water in a closed, with a cold nitrogen atmosphere, Container is introduced. The nitrogen has two tasks to fulfill, on the one hand to cool the container and on the other hand to freeze the water. It has proven to be a disadvantage that the amount of nitrogen to be introduced cannot be matched to the amount of water sprayed in. Another disadvantage is that the temperature difference between nitrogen and water does not result in a constant temperature profile in the container during the manufacturing process

In ( 5 ) "Ice blasting / deburring - an innovative processing method for needs-oriented deburring of components and workpieces" (B. Karpuschewski, R&D project OvGU Magdeburg) describes a cryo-tank for producing water ice. The disadvantage here is that the nitrogen is used to cool the gas atmosphere and to freeze the water and only the temperature is used as a control variable. A further disadvantage is that the water is sprayed in with a nozzle at a relatively high pressure and only water ice particles with a size of <0.8 mm are produced as a result.

The analysis of the state of the art has shown that normal CO ₂ dry ice blasting is ideally suited for impurities that become brittle due to the coldness of the blasting agent. By shredding the commercially available CO ₂ pellets, the efficiency of the CO ₂ blasting systems can be increased and the consumption of blasting media can be reduced. However, this does not increase the aggressiveness. The further processing of commercial water ice by further cooling and crushing and subsequent mixing with CO ₂ particles has proven to be unrealistic.
The production of water ice by spraying water into a cold atmosphere is only possible with small amounts of water, since the water brought in at room temperature leads to a rise in temperature and therefore there is no balanced energy balance.
The geometrical design of the drop and spray nozzles requires a constant feed pressure for the formation of the droplets; the introduction of nitrogen and water causes changes in the pressure in the gas atmosphere, which means that the feed pressure does not remain constant.

Since the prior art has not shown a satisfactory solution for the continuous production of cryogenic water ice as a blasting agent, the object of the present invention is to regulate the workflow for the production of cryogenic water ice so that the pressure and temperature of the gas atmosphere and the The feed pressure in the distributor head remains constant or can be regulated in predetermined ranges.

Furthermore, the object of the invention is to adapt the amount of the nitrogen sprayed in to the water introduced so that a balanced energy balance is achieved, taking into account the general losses.

Another object of the invention is to regulate the manufacturing process in such a way that water ice particles of different sizes and in several layers can be manufactured simultaneously in the specified manufacturing sequence.

Another object of the invention is to record the production-relevant parameters in such a way that a later evaluation of the production process is possible and conclusions can be drawn about the quality.

Furthermore, the object of the invention is to be that deviations from the production process or safety concept, this also applies to the direct environment, are displayed and an alarm is triggered immediately in the event of a hazard.

The task is achieved by measuring the pressure and temperature as well as the nitrogen and water quantities with several sensors at different positions and processing the measurement results of the sensors in a control block and triggering different reactions according to the given program.

To establish and secure the required working temperature in the cryo-tube, pressurized liquid nitrogen is blown from the spray nozzles on the nitrogen ring line, due to the slow cooling of the cryo-tube and the internals in stages, into the cryo-tube and into the transferred to the gaseous state. With the fans, a uniform flow is built up, which should ensure a stable working temperature in the cryo-tube. The temperature is measured in the lower area of the cryo-tube and the deviations are corrected by changing the nitrogen supply. If the temperature is constant, the further work steps are released.

The inventor has found in experiments that the water droplets forming at the outlet of a nozzle are influenced by the size, shape and roughness of the nozzle outlet surface as well as by the nozzle diameter and the differential pressure between the nozzle inlet and nozzle outlet surfaces. By varying these parameters, water droplets of different sizes can be generated at a certain pressure, the differential pressure. With the combination of several nozzle variants it is possible to introduce water droplets of different sizes into the cold nitrogen atmosphere of the cryo-tube at the same time. If the differential pressure changes, the water throughput and thus the drop sequence and drop shape also change. If the differential pressure is too high, a thread of water occurs at the nozzle outlet, with the result that the amount of water cannot freeze completely and collects in the bottom area of the cryo-tube. If the differential pressure is too low, the water droplets stay too long on the nozzle outlet surface and freeze there.

An adjustable working pressure is created in the cryo-tube by injecting nitrogen to cool the cryo-tube. When the working temperature is reached, the working pressure, which is measured with a sensor, is also reached. In order to bring the water into the cryo-tube with the given drop formation, a pressure must be built up in the collecting space of the distributor head which corresponds to the sum of the working pressure and the differential pressure. The collecting space is self-contained. With the introduction of the dripping water, the amount of which can also be measured and regulated, the gas in the collecting space is compressed until the required pressure, i.e. the sum of the working pressure and differential pressure, is reached. The pressure in the collecting space is also measured with a sensor. With the introduction of the water and the nitrogen required to freeze this amount of water, the working pressure in the cryo-tube changes and with it the differential pressure, provided the pressure in the collecting space remains constant. If the working pressure in the cryo-tube decreases, the specified pressure in the collecting space is exceeded. The required pressure can be set again by opening the relief valve. If the working pressure in the cryo-tube increases, the pressure in the collecting space falls below the specified value. If the amount of dripping water is increased in small steps, the specified value rises again to the value calculated in the control block.

The inventor has recognized in experiments that a minimum amount of nitrogen is required for the production of the deep-cold water ice, which is dependent on the starting temperature of the water and the working temperature of the cryo-tube. It was also recognized that the simultaneous introduction of nitrogen and water can lead to significant temperature changes in the cryo-tube. Further investigations have shown that the minimum amount of nitrogen must be dosed in a timed manner, in coordination with the amount of water introduced in the same period, so that the energy balance remains balanced. The water droplets have room temperature when they enter the cryo-tube. Immediately after entry into the cryo-tube, the absolute temperature difference applies to the heat transfer, but this is reduced due to the stagnant gas atmosphere and the gas envelope that forms around the water droplets. In order to accelerate the cooling process, the amount of nitrogen required for the amount of water introduced is sprayed directly onto the water droplets in the mixing area. The flow achieved in this way removes the gas envelope and thus promotes direct contact between nitrogen and water droplets. The temperature in the mixing area should correspond to the working temperature of the cryo-tube. Since not the entire minimum amount of nitrogen immediately comes into contact with the amount of water introduced and with losses, e.g. B. due to the insulation, the temperature is measured and limited in the mixed area. If the temperature rises above the specified limit value, the nitrogen supply is increased and the water supply is interrupted until the setpoint is reached again. If the temperature falls below the specified limit, the nitrogen supply is throttled until the working temperature is reached.

The partially frozen water droplets are swirled by the nitrogen flow, but fall down by gravity. In order to reduce the speed of fall and thus to extend the freezing time, as well as to create the conditions for a single or multiple layer formation, a counter flow is built up with the help of several fans. The countercurrent causes the water droplets to be kept in a certain plane or blown up again so that they can be wetted with the additional spray water sprayed in from the nozzles on the water ring to form another layer of ice. Through the built-in components with the flow channels, the flow rate can be changed individually and the resulting water ice particles are exposed to the influence of nitrogen and the additional spray water until the mass is so great that the countercurrent can no longer stop the free fall entire cryo-tube is a relatively sluggish process. In contrast, the temperature changes in the mixing area are relatively quick and require short reaction times. The water introduced at room temperature leads to a rapid temperature increase in the mixing area and a relatively slow temperature increase in the entire cryo-tube runs

The main advantages of the invention are that the parameters relevant for the production of deep-cold water ice are not recorded individually and regulated within specified limits, but are recorded in their entirety and can be functionally reacted to immediately in the event of deviations from the target value.

Another essential advantage of the invention is that the geometric design of the drip nozzle, in order to form a single water droplet, requires a precisely determinable differential pressure between the nozzle inlet and nozzle outlet surfaces, and when the geometric design changes, at the same differential pressure, water droplets of different sizes are formed .

Another advantage of the invention is that with the combination of several drip nozzles of different geometrical design, with the same differential pressure, water droplets of different sizes are created, which in a cryogenic atmosphere immediately form a thin ice shell surrounding the water droplets and thus produce a blasting agent with different particle sizes can be.

Another essential advantage of the invention is that, in order to achieve a balanced energy balance, the amounts of nitrogen required to cool the cryo-tube and to freeze the water droplets are introduced separately and the temperature is measured separately in the respective effective range and the required amount of nitrogen is determined and determined as a function of the specified parameters be dosed

Another advantage of the invention is that the amount of water introduced is constantly determined and the amount of nitrogen required to freeze the amount of water introduced, depending on the specified manufacturing parameters, is calculated and appropriately dosed and thus the energy balance can be kept balanced.

Another advantage of the invention is that the differential pressure required for the formation of the water droplets can be kept constant in the case of production-related pressure fluctuations in the cryo-tube

It is also advantageous that the time required for the water droplet to freeze through is determined not only by free fall but also by a countercurrent.

It is also advantageous that the intensity of the countercurrent enables the formation of one or more additional water ice layers.

Another advantage of the invention is that the intensity of the countercurrent can be changed in each flow channel so that water ice particles of different sizes can be produced.

• 1 : Prinzipieller Aufbau der Steuerung
• 2 : Steuerungsschema

The invention is to be described using an exemplary embodiment. Show it

• 1 : Basic structure of the control
• 2 : Control scheme

In a closed cryo-tube ( 1 ) becomes a certain amount of liquid nitrogen N ₁ that came with the sensor S ₁ is detected, for cooling the interior ( 20th ) and the internals ( 16 ) of the cryo-tube ( 1 ) sprayed. The required amount N ₁ becomes from the total mass M _G the cryo-tube ( 1 ) and the adjustable working temperature T ₁ calculated. The liquid nitrogen with the pressure p ₁ relaxed after leaving the spray nozzles on the ring line ( 2 ). The inside of the cryo-tube cools due to the pressure reduction and the transition to the gas phase ( 1 ) to the adjustable working temperature T ₁ starting with multiple sensors S ₂ in the lower area of the cryo-tube ( 1 ) is measured, at the same time the pressure in the cryotube rises ( 1 ) to the value p ₂ . The value p ₂ is with the sensor S ₃ recorded.

In the lid ( 3 ) of the cryo-tube ( 1 ) is the distributor head ( 4th ) for the controlled entry of the amount of water W _c , which results from the amount of dripping water W ₁ and the amount of spray water W ₂ composed and an initial temperature T ₂ owns, mounted. The amount of water spray W ₂ is via the water spray nozzle ( 9 ) and the additional spray water W ₃ is via the spray nozzles on the water ring ( 17th ) brought in.

The total amount of water W _G is with the flow sensor S ₄ recorded. The amount of dripping water W ₁ is with the sensor S ₅ and the amount of spray water W ₂ + W ₃ is measured with the sensor S ₆ measured

The amount of dripping water W ₁ comes after opening the drip valve ( 5 ) into the collecting room ( 6th ) of the distributor head ( 4th ) and from there depending on the design of the drip nozzles ( 7th ) into the cryo-tube ( 1 ) Since the drip nozzles ( 7th ), if no water ice is made, it will be in the collecting area ( 6th ) located gas on the pressure p ₃ compressed that with the sensor S ₇ is detected.

The number of drip nozzles ( 7th ) and their combination is determined in order to obtain a certain drop size and its number and is therefore known. The influence of the roughness of the drop nozzle outlet surface DR, the shape of the drop nozzle outlet surface DF and the nozzle diameter were investigated in tests D _D determined for the drop shape and the drop sequence and tested various combinations. For these selected combinations, the relationship between pressure p ₄ and amount of dripping water W ₁ certainly. A precisely defined amount of dripping water W ₁ requires the associated differential pressure p ₄ , which was determined in the tests in a normal atmosphere.

Ist der Wert für p₃ zu hoch, entsteht ein durchgängiger, nicht erwünschter, Wasserfaden. Ist der Wert für p₃ zu gering, frieren die Wassertropfen bereits an den Tropfdüsen (7) fest.In the cryo-tube ( 1 ) is built up by spraying in the amount of nitrogen N ₁ a changing pressure p ₂ on. So that the dripping water W ₁ from the collecting room ( 6th ) of the distributor head ( 4th ) into the cryo-tube ( 1 ), the pressure must be p ₃ > p ₂ . This results in general $${\text{p}}_{}$$$${}_3={\text{<figure-callout id="2" label="p" filenames="DE102020002085A1\_0008.png" state="{{state}}">p</figure-callout>}}_2+{\text{p}}_{\mathrm{4th}}$$

Is the value for p ₃ too high, a continuous, undesirable, water thread is created. Is the value for p ₃ too little, the water droplets are already freezing on the drip nozzles ( 7th ) fixed.

In the cold nitrogen atmosphere of the cryo-tube ( 1 ) with the adjustable working temperature T ₁ , becomes the total amount of water W _G with the starting temperature T ₂ brought in. The entire amount of water W _G is recorded with the flow sensor S4 and the outlet temperature T ₂ of the water is with the sensor S ₈ measured. The one for cooling the entire amount of water W _G The required amount of nitrogen N2 is supplied via the cooling nozzles on the nitrogen ring ( 11 ) on the drops of water ( 8th ) and on the water droplets in the spray cone ( 10 ) from the water spray nozzle ( 9 ) blown. The amount of water measured with sensor S4 W _G determines the required amount of nitrogen N ₂ . The following applies to the amount of nitrogen N2 $${\text{N}}_{}$$$${}_2=\text{f}\left({\text{<figure-callout id="1" label="T" filenames="DE102020002085A1\_0008.png" state="{{state}}">T</figure-callout>}}_1,{\text{<figure-callout id="2" label="T" filenames="DE102020002085A1\_0008.png" state="{{state}}">T</figure-callout>}}_2,{\text{W.}}_{\text{G}}\right)$$

For the per unit of time t ₃ introduced partial quantities d _N2 for nitrogen and d _{flat share} applies to water $${\text{N}}_{}$$$${}_2{\text{/ d}}_{\text{N2}}={\text{W.}}_{\text{2}}{\text{/ d}}_{\text{Flat share}}$$

ergibt, bildet sich relativ schnell eine, den Wassertropfen (8) umschließende, dünne Eisschicht, sowie eine stationärer Gashülle um den Wassertropfen (8) mit dem Effekt, dass die Abkühlung des Restwassertropfens durch die isolierend wirkende Gashülle langsamer verläuft.From the distributor head ( 4th ) becomes the amount of dripping water W ₁ with an initial temperature T ₂ , with the differential pressure p ₄ , through several drip nozzles ( 7th ) into the cryo-tube ( 1 ) with temperature T ₁ pressed. Due to the high temperature difference T _D that made up $${\text{T}}_{\text{D.}}={\text{<figure-callout id="2" label="T" filenames="DE102020002085A1\_0008.png" state="{{state}}">T</figure-callout>}}_2+{\text{/ <figure-callout id="1" label="T" filenames="DE102020002085A1\_0008.png" state="{{state}}">T</figure-callout>}}_{\text{1}}\text{/}$$

results, one forms relatively quickly, the water droplets ( 8th ) surrounding, thin layer of ice, as well as a stationary gas envelope around the water droplet ( 8th ) with the effect that the cooling of the remaining water droplets is slower due to the insulating gas envelope.

The amount of water spray W ₂ comes with a higher spray pressure p ₅ from the water spray nozzle ( 9 ) into the cryo-tube ( 1 ) pressed, thereby forming a spray cone ( 10 ). The fine water droplets of the spray cone ( 10 ) meet the partially frozen water droplets ( 8th ) with the insulating gas envelope, which is thereby partially removed and forms a new layer of water on the partially frozen water droplet ( 8th ).

The spray nozzle ( 2 ) amount of nitrogen introduced N ₁ has the atmosphere in the cryo-tube ( 1 ) on T ₁ cooled down. This means that there is no liquid nitrogen in the cryo-tube ( 1 ) which, through the transition to the gas phase, can extract the heat from the water introduced.

It is known that the water to get from the starting temperature T ₂ that came with the sensor S ₈ is measured at working temperature T ₁ To be cooled, goes through three phases and thereby a certain amount of heat Q ₁ must give off an additional amount of nitrogen N ₂ must be included. This additional required amount of nitrogen N ₂ is via the pairs of opposite cooling nozzles ( 11 ) into the cryo-tube ( 1 ) blown and with the sensor S ₉ Controlled in terms of quantity and with the throttle valve V8 regulated. The amount of nitrogen to be injected N ₂ is set in such a way that it is necessary for the cooling of the partial quantity of W ₂ sufficient. It applies $${\text{Q}}_{\text{wab}}={\text{Q}}_{\text{Well}}$$

The amount of nitrogen required for cooling can be defined for the amount of water introduced per unit of time.

However, this only applies if each nitrogen particle hits the associated water droplets. The lateral spraying of nitrogen leads to a swirling of the water droplets with the nitrogen particles and thus to a fluctuating change in temperature T ₁ in this mixing area ( 12th ) associated with the sensor S ₁₀ is detected. The temperature T ₁ in the mixing area ( 12th ) is given by the upper value T _1O and sub-values T _1U of the sensor S ₁₀ restricted and accordingly the nitrogen supply N ₂ regulated. Thus $${\text{<figure-callout id="2" label="N" filenames="DE102020002085A1\_0008.png" state="{{state}}">N</figure-callout>}}_2=\text{f}\left({\text{T}}_{\text{1O}}{\text{, T}}_{\text{1U}}{\text{, <figure-callout id="1" label="W" filenames="DE102020002085A1\_0008.png" state="{{state}}">W</figure-callout>}}_{\text{1}}{\text{, <figure-callout id="2" label="W" filenames="DE102020002085A1\_0008.png" state="{{state}}">W</figure-callout>}}_{\text{2}}\text{, dN}=\text{f}\left(\text{dT}\right)\right)$$

Normally the drops fall ( 8th ) vertically downwards. The time of free fall corresponds to the freezing time t _E . The free fall can be _{slowed down by a counter flow G s} and thus the freezing time t _E be extended. The counterflow G _s is generated by the fan ( 13th ) generated. The nitrogen gas is supplied through the suction nozzle ( 14th ) sucked in and into the corresponding flow channels ( 15th ) directed. The countercurrent G _S , in the flow channels ( 15th ) can be controlled by the motor on the blower ( 13th ) are regulated in their intensity and thus also the freezing time t _E .

• Alle Ventile sind geschlossen.

The function is as follows:

• All valves are closed.

Valve V1 in the nitrogen line to the spray nozzle ( 2 ) will be a time t ₁ from the time module Z1 opened. A part of the determined amount of nitrogen N _{1 that is} generated with the sensor S ₁ detected and with the throttle valve V4 is regulated in the amount, flows with the pressure p ₁ at intervals through the spray nozzle ( 2 ) into the cryo-tube ( 1 ) and expanded to cold nitrogen gas. At the same time the fans ( 13th ) via the time modules Z2 until Z7 switched on and the controlled systems R 1 to R 6 for the individual flow channels ( 15th ), with the corresponding switch-on times t ₂ until t ₇ activated. and thus the nitrogen gas is circulated. The interior of the cryo-tube ( 1 ) and the internals ( 16 ) gradually cooled. This act of opening the valve V1 repeats itself until the temperature in the Cryo-R is at the specified working temperature T ₁ has stabilized. Is the working temperature T ₁ that came with the sensors S ₂ in the lower area of the cryo-tube ( 1 ) is measured, the valve V1 closed.

With the relaxation of the under the pressure p ₁ standing nitrogen builds up in the cryo-tube ( 1 ) the pressure p ₂ on. The pressure p ₂ is adjustable and is operated with the pressure relief valve V2 limited in size. With the opening of the valve V3 and the drip valve ( 5 ) an adjustable pressure and volume of water reaches the collecting space ( 6th ) of the distributor head ( 4th ) and builds up the pressure p ₃ on. Is the intended pressure p ₃ reached, the drip valve ( 5 ) closed. Will the intended pressure p ₃ the valve is exceeded V5 from the pressure sensor S ₇ open until the pressure p ₃ is reached again.

The drip nozzles ( 7th ) from the time module Z8 over a time interval t ₈ opened. The differential pressure corresponds to the drop nozzle combination p ₄ given. This differential pressure has the effect that the amount of dripping water determined for the selected combination of drip nozzles W ₁ Because the pressure is enforced p ₂ in the cryo-tube ( 1 ) varies, the pressure must p ₃ in the collecting room ( 6th ) these pressure fluctuations are adapted so that the differential pressure p ₄ remains constant.

It applies $${\text{<figure-callout id="3" label="p" filenames="DE102020002085A1\_0008.png" state="{{state}}">p</figure-callout>}}_3={\text{<figure-callout id="2" label="p" filenames="DE102020002085A1\_0008.png" state="{{state}}">p</figure-callout>}}_2+{\text{p}}_{\mathrm{4th}}$$

The pressure adjustment in the collecting space ( 6th ) occurs when the working pressure rises p ₂ in the cryo-tube ( 1 ) by increasing the amount of dripping water W ₁ at the throttle valve V3 and thus to an increase in pressure p ₃ in the collecting room ( 6th ). The working pressure decreases p ₂ in the cryo-tube ( 1 ), the pressure becomes p ₃ in the collecting room ( 6th ) by briefly opening the valve V5 reduced..

The drops of water ( 8th ) arrive at a constant differential pressure p ₄ into the cryo-tube ( 1 ) and immediately form a layer of ice and a gas envelope there. To remove the gas envelope and to form one or more additional layers of ice on the water droplet ( 8th ) is optionally available from the nozzles on the water ring ( 17th ), after opening the ring valve V7 or the water spray nozzle ( 9 ) after opening the spray valve V6 , Water on the partially frozen water droplets ( 8th ) sprayed. The opening hours t ₉ of the ring valve V7 is made by the time module Z9 and the opening time t ₁₀ the water spray nozzle ( 9 ) is determined by the time module Z10 regulated Water can also be poured onto the partially frozen water droplets from both nozzles at the same time or at different intervals ( 8th ) can be sprayed.

The amount of water introduced W _G is recorded with sensor S4 and the amount of nitrogen required for cooling N ₂ calculated from this. The nitrogen required for the amount of water currently flowing is supplied by the throttle valve V8 regulated and with the sensor S ₉ controlled. This ensures that the energy balance remains constant.

That by the blower ( 13th ) circulated cold nitrogen gas and the amount of spray water W ₂ + W _{3 introduced} with the temperature T ₂ and the amount of nitrogen blown in N ₂ lead to turbulence in the mixing area ( 12th ) and thus to deviations from the specified working temperature T ₁ . For the water droplets to freeze through, it is essential to maintain the working temperature T ₁ necessary. To ensure the working temperature T ₁ and for quick correction is in the mixing area ( 12th ) is also the sensor S ₁₀ Installed. When the set upper limit T _{10b is reached} on the sensor S ₁₀ is the water supply by closing the valves V3 , V6 and V7 interrupted until the working temperature T ₁ is reached again. If the set lower limit T _{1un is} reached, the nitrogen supply is stopped at the throttle valve V8 reduced until the working temperature T ₁ is stable again.

The drops of water W ₁ After leaving the drip nozzles, the different adjustable flow speeds in the individual flow channels ( 15th ), which are implemented by the controlled systems R1 to R6, as well as by the amount of water blown in W ₂ and the amount of nitrogen N ₂ in the mixing area ( 12th ) are whirled around in an uncontrolled manner, while they are exposed to another layer of water, which immediately freezes to a new layer of ice due to the nitrogen. The uncontrolled turbulence creates water ice particles of different sizes and thus with different weights. Depending on the weight, the water ice particles either fall through the interior ( 20th ) the internals ( 16 ) or due to a low flow velocity in one of the flow channels ( 15th ) into the collecting cone ( 18th ) or due to the higher flow velocity in one of the flow channels ( 15th ) back to the mixing area ( 12th ) thrown. In the mixing area ( 12th ) the water ice particles can receive another layer of ice or they hit a partially frozen water droplet ( 8th ) which can be destroyed in the process, forming angular fragments of ice.

The one in the collecting cone ( 18th ) coming together water ice is released through the outlet system ( 19th ) deducted.

The supply of nitrogen and water into the cryo-tube ( 1 ), as well as the removal of the water ice leads to changes in the pressure p ₂ in the cryo-tube ( 1 ). This inevitably also changes the differential pressure p ₄ . Since the drop formation from the differential pressure p ₄ depends, this must be corrected by a correction of the pressure p ₃ in the collecting room ( 6th ) be balanced.

Is the differential pressure p ₄ too little, the pressure must be p ₃ in the collecting room ( 5 ) increase. This is done by increasing the water throughput W1 until the difference between the pressure p ₃ in the collecting room ( 5 ) and the pressure p ₂ in the cryo-tube ( 1 ) again to the specified differential pressure p ₄ is equivalent to. Is the differential pressure p ₄ too high, the pressure becomes p ₃ in the collecting room ( 5 ) by opening the valve V5 in the distributor head ( 4th ) reduced.

List of reference symbols

1

Cryo-tube

2

Ring line with spray nozzle

3

lid

4th

Distributor head

5

Drip valve

6th

Collection room

7th

Drip nozzle

8th

Waterdrop

9

Water spray nozzle

10

Spray cone

11

Nitrogen ring with cooling nozzles

12th

Mixing area

13th

fan

14th

Intake manifold

15th

Flow channel

16

Internals

17th

Water ring

18th

Collecting cone

19th

Outlet

20th

Indoor

21

Relief valve

DR

Roughness of the nozzle exit surface

DF

Shape of the drip nozzle outlet area

DD

Nozzle diameter

dN2

currently introduced amount of nitrogen

dWG

currently introduced amount of water

N1

Amount of nitrogen to cool the cryo-tube

N2

Amount of nitrogen used to cool the water

MG

Mass of the cryo-tube

Flat share

Total amount of water

WC

Water volume distributor head

W1

Amount of dripping water

W2

Amount of water spray

W3

Additional spray water

T1

Working temperature in the cryo-tube

T2

Outlet temperature of the water

TD

Temperature difference

T1O

upper working temperature

T1U

lower working temperature

tE

Freezing time

t1

Opening time V1

t2

Fan switch-on time 13th .1

t3

Fan switch-on time 13th .2

t4

Fan switch-on time 13th .3

t5

Fan switch-on time 13th .4

t6

Fan switch-on time 13th .5

t7

Fan switch-on time 13th .6

t8

Opening time drip nozzles ( 7th ) through Z8

t9

Opening time ring valve V7 through Z9

t10

Opening time water spray nozzle ( 9 ) through Z10

GS

Countercurrent

Q1

Amount of heat in the water

Qwab

amount of heat to be given off by the water

QNauf

amount of heat to be absorbed by nitrogen

S1

Flow rate nitrogen N1

S2

Temperature in cryo-tube

S3

Pressure in the cryo-tube

S4

Flow rate WG

S5

Flow rate W1

S6

Flow rate W2 + W3

S7

Pressure in the manifold head plenum

S8

Water inlet temperature

S9

Flow rate nitrogen N2

S10

Temperature in the mixing area

S11

Temperature at the collecting cone

V1

Nitrogen valve cooling cryo-tube

V2

Pressure relief valve cryo-tube

V3

Water valve W1

V4

Throttle valve nitrogen N1

V5

Pressure relief valve collecting chamber distributor head

V6

Spray valve

V7

Ring valve

V8

Throttle valve

p1

Liquid nitrogen pressure

p2

Pressure in the cryo-tube

p3

Pressure in the collecting space

p4

Differential pressure

p5

Spray pressure

Z1

Time module for V1

Z2

Time module for R1

Z3

Time module for R2

Z4

Time module for R3

Z5

Time module for R4

Z6

Time module for R5

Z7

Time module for R6

Z8

Opening time t ₈ Drip nozzles ( 7th )

Z9

Opening time t ₉ Ring valve V7

Z10

Opening time t ₁₀ Water spray nozzle ( 9 )

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 10309191 A1 [0003]
• WO 2003101667 A1 [0004]
• DE 102015209994 A1 [0006]
• DE 102009027974 B4 [0007]
• DE 102004057665 A1 [0007]
• DE 202010000713 U1 [0007]
• WO 2015/074765 A1 [0008]
• DE 102010020618 A1 [0009]
• DE 3434163 A1 [0010]
• DE 3505675 A1 [0011]
• DE 10010012 A1 [0013]
• DE 20115013 U1 [0013]

Claims (6)

Program control for the production of a solid cryogenic blasting agent from water, characterized in that water in the form of drops, with a pressure dependent on the combination of drop nozzles, different geometric dimensions, is introduced into a cold nitrogen atmosphere of a closed cryo-tube and the drops are of different sizes , braked by a controllable countercurrent in free fall and sprayed one or more times with water and nitrogen, while maintaining a balanced energy balance between water and nitrogen, and the parameters relevant for the production of the cryogenic water ice particles are recorded in their entirety in a control unit and are functionally networked with each other in such a way that the required pressure is kept constant despite production-related changes in the specified parameters. Program control for the production of a solid cryogenic abrasive from water Claim 1 characterized in that the amount of water introduced is constantly monitored and the amount of nitrogen required for the formation of deep-frozen water ice, depending on the set working temperature and the inlet temperature of the water, is determined and introduced at the same time. Program control for the production of a solid cryogenic abrasive from water according to one of the preceding claims, characterized in that the water droplets in a mixing area of several nozzles at different angles are acted upon with a water film of varying intensity and the corresponding amount of nitrogen that further layers of ice are on the partially frozen Water droplets can form, with deviations from the specified working temperature in the mixed area being corrected by changes in the water throughput or the nitrogen input Program control for the production of a solid cryogenic blasting agent from water according to one of the preceding claims, characterized in that the free fall of the water droplets is slowed down by a countercurrent, and the speed of the countercurrent in the individual flow channels by the associated fan in a range from zero to the specified The maximum value can be varied so that the frozen and partially frozen water droplets are conveyed back into the mixing area and sprayed again with water and nitrogen and thus the size of the water ice particles is increased by the formation of further water ice layers, with the change in the flow velocities in the flow channels, which takes place according to a predetermined program, the water ice particles formed can pass through the flow channel at zero speed into the collecting cone. Program control for the production of a solid cryogenic blasting agent from water according to one of the preceding claims, characterized in that the differential pressure required for the formation of water droplets alone between the drip nozzle inlet area and the drip nozzle outlet area of a given drop combination is entered as a constant and added to the variable internal pressure in the cryo-tube and the resulting value of the pressure at the drip nozzle inlet surface can be corrected either by increasing the amount of dripping water in the collecting space of the distributor head in the event of negative pressure or by briefly opening a relief valve in the event of excess pressure. Program control for the production of a solid cryogenic blasting agent from water according to one of the preceding claims, characterized in that the ratio of the size distribution of the water ice particles is dependent on the combination of drip nozzles and a specific program sequence and differential pressure are required for this combination, and these values are available as recipes, which have to be corrected by the control system based on the working temperature in the cryo-tube and the outlet temperature of the water.

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