213-Upgrade application of an anti-clogging and high-efficiency separation technology for secondary steam separation in multi-effect evaporation concentration systems for foamy liquids

Our company once carried out a technical upgrade using vane separators for a company in East China that produced calcium propionate, in order to solve the problem of blockage in the liquid-solid-vapor purification equipment for the secondary steam from its calcium propionate neutralization evaporators. Recently, we have received a request from a company in Shandong to upgrade the secondary steam purification equipment used in its calcium propionate neutralization solution evaporator, as this equipment is experiencing blockages. Let’s first discuss the issue of calcium propionate neutralization solution generating carbon dioxide and water vapor during evaporation in the concentrator; these gases blow out the lightweight calcium propionate crystals suspended on the liquid surface, causing them to escape in the form of large amounts of stable foam through the gas outlet at the top of the separation chamber and into downstream pipeline equipment, thereby leading to accumulation and blockages. After that, we can expand the discussion to similar conditions in other projects.

This post was last edited by luoli519 on 2023-1-15 at 14:43. Some people ask why carbon dioxide is produced during the evaporation and concentration process of the calcium propionate neutralization solution This is mainly because the production process of calcium propionate involves the reaction of calcium carbonate with propionic acid to release carbon dioxide. Residual reactions in the calcium propionate neutralization solution, as well as dissolved carbon dioxide gas, are both factors that contribute to the release of carbon dioxide during the evaporation and concentration process of this solution. Calcium propionate formed as a result of the reaction precipitates as lightweight feathery crystals that float on the surface of the more viscous mother liquor. The large amount of steam generated at the liquid surface, along with the carbon dioxide released, contributes to the formation of numerous stable bubbles. Driven by air currents, these bubbles carry the calcium propionate crystals and the layer of mother liquor with them, allowing them to pass through the existing defoaming elements and escape from the gas-phase outlet pipe of the evaporator, entering the downstream pipeline systems.

This post was last edited by luoli519 on 2023-1-11 at 20:56. The diagram below shows a schematic of the calcium propionate neutralization solution evaporator in a certain enterprise:

This evaporator uses a conventional and simple wire mesh demister, which not only tends to get clogged by calcium propionate crystals, but also has limited operational flexibility and poor stability in separation efficiency. As a result, large amounts of calcium propionate escape along with the steam into the vapor outlet pipeline of the evaporator, where they settle and accumulate, causing blockages in the pipelines and disruptions in gas flow. This transforms the evaporator, which was originally operated under negative pressure, into a system operating under positive pressure, thereby **hindering the continuous and stable operation of the production facility and leading to significant fluctuations in production capacity.

The last edit to this post was made by luoli519 on 2023-1-11 at 21:05. The image shown is a photo taken on site by the owner, showing the evaporator’s secondary steam outlet pipeline blocked by calcium propionate, and the situation during the shutdown to clear the blockage.

In recent years, most companies that use multi-effect evaporators have, in order to achieve energy efficiency management goals, compressed the secondary steam from the evaporators and reused it as a heating source for the subsequent evaporators, thereby significantly improving the efficiency of heat utilization. Steam compressors (heat pumps) have strict requirements regarding the amount of liquid and salts present in the inlet secondary steam. Therefore, before the secondary steam generated by the evaporator enters the steam compressor (heat pump), it must be thoroughly and efficiently purified using a high-performance vapor-liquid-solid separator to remove any residual liquid and scale. Otherwise, secondary steam containing saline scale mother liquor entering the compression cylinder of the compressor (heat pump) will cause crystals to form and attach to the rotating and stationary components inside the compressor, leading to corrosion of those components and even damage to the rotating parts.

This post was last edited by luoli519 on 2023-1-12 01:49. The image below shows the obvious corrosion on the impeller blades, which was discovered during the maintenance of a centrifugal compressor for secondary steam in a certain enterprise.

The scale crystals that enter the steam compressor (heat pump) continue to accumulate and grow on the high-speed rotating components. This not only accelerates and worsens the corrosion of these internal components, but also the growing aggregates of crystals significantly affect the dynamic balance of the high-speed rotating components, posing a risk of damage or even breakage of these components during operation. The image below shows the damaged blades of the secondary steam centrifugal compressor used in a certain enterprise’s evaporator:

The reason why the steam entering the secondary steam compressor carries liquid droplets and film of saline scale is inevitably due to the unstable operating efficiency of the separation equipment upstream of the steam compressor. In the case of evaporators for calcium propionate neutralization solutions, a large amount of foam is generated; this foam carries the lightweight calcium propionate crystals into the conventional wire mesh demister installed in the evaporator. As a result, the wire mesh demister becomes clogged frequently and steam flow is impaired. The secondary steam produced by the evaporator cannot be discharged in time, leading to pressure buildup. Insufficient steam supply to the steam compressor causes the high-speed rotating components to vibrate, which further increases the risk of these components breaking or cracking.

This post was last edited by luoli519 on 2024-4-8 at 16:50. Here is an excerpt providing reference information on a case study of upgrading the secondary steam purification system in calcium propionate neutralization evaporators by using vane separators instead of the traditional mesh demisters.