Will research experience in chemical engineering count when applying to grad school for biomedical engineering?
Your research experience counts!

Specifically, you are getting experience in the process of "doing research": finding a question, reading the literature, forming hypotheses and figuring out how to test them, etc. These are important skills, even moreso than (say) knowing your way around a specific instrument's console. Admission committees also know that your local options, especially as an undergrad, are limited. I did linguistics and computer science research as an undergrad, and then applied (successfully) to neuroscience programs. 

If you can do well with your current work, I think you'll be good shape for grad school. You probably do want to address this change in your personal statement by briefly mentioning how/why your motivations changed and the skills you will bring to your new program. I talked a little about I saw machine learning techniques crash and burn on language/vision tasks, and wanted to understand how people/animals did so well with such lousy "hardware". I also mentioned that my existing training would let me analyze and model large datasets, like the ones I hoped to collect.

Finally, don't forget that some of your skills are "reusable" in biomedical engineering. The development of tracers for PET/SPECT involves a lot of chemistry, ditto for flourophores for microscopy. Process experience can help when building or using high-throughput screening systems. There's also a lot of interest in developing substrates that nerves, blood vessels, etc can grow on or are compatible with certain techniques. 

This is all conditioned on you remaining somewhat interested in chemical engineering and doing well in your research+coursework. If your heart isn't in it and you're likely to do badly, I would certainly switch; I just don't think it's essential.

Good luck!