An Alternative Arrangement for Process Water Heating?

300 m3 /100 degrees

In what time frame?

per hour.

Can you inject steam directly into the water pipe? Controlling the steam valve from temperature measured downstream of the injection point.

You don't give line pressure, but it would help if this is somewhat above atmospheric, as inaccuracy in temperature measurement might mean it was trying to control to just above 100°C, resulting in boiling and perhaps steam flowing from the pipe.

Codey

The pressure is atmospheric, I dont know if this strategy of dirctly injecting into water pipe would be successful but ideally, we are looking for a better replacement of conventional counter flow heater. Is there any other device for water heating using steam, the steam we have is free as we will release it to atmosphere otherwise. So its quite economical to use it to heat up water, just we need a better heat exchanger,

Use a 3-way Valve . Port A Steam, port B Cold water and Port AB Hot water.

You stated your long term plan is to install a counterflow heat exchanger. I would recommend a careful examination of your water quality requirements in order to not run into higher maintenance cost due to scaling and corrosion. Reading between the lines I gather you have a rather primitive setup and the steam and water qualities may not be good enough to avoid severe scaling and/or corrosion. You may be able to find a used or surplus deaerator vessel with the required flow capacity from a small power plant.

I'm planning to use a simple tank for sometime for an inlet for water, then steam inlet, mixing with water and heating it up to atleast 60deg. Did anyone experience to setup a small unit like that?

It will be noisy. Make sure you have adequate pressure relief and that it goes to a safe place.